chore: migrate to gitea

vendor/cloud.google.com/go/auth/credentials/compute.go

@@ -0,0 +1,102 @@
+// Copyright 2023 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package credentials
+
+import (
+	"context"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"net/url"
+	"strings"
+	"time"
+
+	"cloud.google.com/go/auth"
+	"cloud.google.com/go/compute/metadata"
+)
+
+var (
+	computeTokenMetadata = map[string]interface{}{
+		"auth.google.tokenSource":    "compute-metadata",
+		"auth.google.serviceAccount": "default",
+	}
+	computeTokenURI = "instance/service-accounts/default/token"
+)
+
+// computeTokenProvider creates a [cloud.google.com/go/auth.TokenProvider] that
+// uses the metadata service to retrieve tokens.
+func computeTokenProvider(opts *DetectOptions, client *metadata.Client) auth.TokenProvider {
+	return auth.NewCachedTokenProvider(&computeProvider{
+		scopes:           opts.Scopes,
+		client:           client,
+		tokenBindingType: opts.TokenBindingType,
+	}, &auth.CachedTokenProviderOptions{
+		ExpireEarly:         opts.EarlyTokenRefresh,
+		DisableAsyncRefresh: opts.DisableAsyncRefresh,
+	})
+}
+
+// computeProvider fetches tokens from the google cloud metadata service.
+type computeProvider struct {
+	scopes           []string
+	client           *metadata.Client
+	tokenBindingType TokenBindingType
+}
+
+type metadataTokenResp struct {
+	AccessToken  string `json:"access_token"`
+	ExpiresInSec int    `json:"expires_in"`
+	TokenType    string `json:"token_type"`
+}
+
+func (cs *computeProvider) Token(ctx context.Context) (*auth.Token, error) {
+	tokenURI, err := url.Parse(computeTokenURI)
+	if err != nil {
+		return nil, err
+	}
+	hasScopes := len(cs.scopes) > 0
+	if hasScopes || cs.tokenBindingType != NoBinding {
+		v := url.Values{}
+		if hasScopes {
+			v.Set("scopes", strings.Join(cs.scopes, ","))
+		}
+		switch cs.tokenBindingType {
+		case MTLSHardBinding:
+			v.Set("transport", "mtls")
+			v.Set("binding-enforcement", "on")
+		case ALTSHardBinding:
+			v.Set("transport", "alts")
+		}
+		tokenURI.RawQuery = v.Encode()
+	}
+	tokenJSON, err := cs.client.GetWithContext(ctx, tokenURI.String())
+	if err != nil {
+		return nil, fmt.Errorf("credentials: cannot fetch token: %w", err)
+	}
+	var res metadataTokenResp
+	if err := json.NewDecoder(strings.NewReader(tokenJSON)).Decode(&res); err != nil {
+		return nil, fmt.Errorf("credentials: invalid token JSON from metadata: %w", err)
+	}
+	if res.ExpiresInSec == 0 || res.AccessToken == "" {
+		return nil, errors.New("credentials: incomplete token received from metadata")
+	}
+	token := &auth.Token{
+		Value:    res.AccessToken,
+		Type:     res.TokenType,
+		Expiry:   time.Now().Add(time.Duration(res.ExpiresInSec) * time.Second),
+		Metadata: computeTokenMetadata,
+	}
+	return token, nil
+}

vendor/cloud.google.com/go/auth/credentials/detect.go

@@ -0,0 +1,471 @@
+// Copyright 2023 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package credentials
+
+import (
+	"context"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"log/slog"
+	"net/http"
+	"os"
+	"time"
+
+	"cloud.google.com/go/auth"
+	"cloud.google.com/go/auth/internal"
+	"cloud.google.com/go/auth/internal/credsfile"
+	"cloud.google.com/go/auth/internal/trustboundary"
+	"cloud.google.com/go/compute/metadata"
+	"github.com/googleapis/gax-go/v2/internallog"
+)
+
+const (
+	// jwtTokenURL is Google's OAuth 2.0 token URL to use with the JWT(2LO) flow.
+	jwtTokenURL = "https://oauth2.googleapis.com/token"
+
+	// Google's OAuth 2.0 default endpoints.
+	googleAuthURL  = "https://accounts.google.com/o/oauth2/auth"
+	googleTokenURL = "https://oauth2.googleapis.com/token"
+
+	// GoogleMTLSTokenURL is Google's default OAuth2.0 mTLS endpoint.
+	GoogleMTLSTokenURL = "https://oauth2.mtls.googleapis.com/token"
+
+	// Help on default credentials
+	adcSetupURL = "https://cloud.google.com/docs/authentication/external/set-up-adc"
+)
+
+var (
+	// for testing
+	allowOnGCECheck = true
+)
+
+// CredType specifies the type of JSON credentials being provided
+// to a loading function such as [NewCredentialsFromFile] or
+// [NewCredentialsFromJSON].
+type CredType string
+
+const (
+	// ServiceAccount represents a service account file type.
+	ServiceAccount CredType = "service_account"
+	// AuthorizedUser represents a user credentials file type.
+	AuthorizedUser CredType = "authorized_user"
+	// ExternalAccount represents an external account file type.
+	//
+	// IMPORTANT:
+	// This credential type does not validate the credential configuration. A security
+	// risk occurs when a credential configuration configured with malicious urls
+	// is used.
+	// You should validate credential configurations provided by untrusted sources.
+	// See [Security requirements when using credential configurations from an external
+	// source] https://cloud.google.com/docs/authentication/external/externally-sourced-credentials
+	// for more details.
+	ExternalAccount CredType = "external_account"
+	// ImpersonatedServiceAccount represents an impersonated service account file type.
+	//
+	// IMPORTANT:
+	// This credential type does not validate the credential configuration. A security
+	// risk occurs when a credential configuration configured with malicious urls
+	// is used.
+	// You should validate credential configurations provided by untrusted sources.
+	// See [Security requirements when using credential configurations from an external
+	// source] https://cloud.google.com/docs/authentication/external/externally-sourced-credentials
+	// for more details.
+	ImpersonatedServiceAccount CredType = "impersonated_service_account"
+	// GDCHServiceAccount represents a GDCH service account credentials.
+	GDCHServiceAccount CredType = "gdch_service_account"
+	// ExternalAccountAuthorizedUser represents an external account authorized user credentials.
+	ExternalAccountAuthorizedUser CredType = "external_account_authorized_user"
+)
+
+// TokenBindingType specifies the type of binding used when requesting a token
+// whether to request a hard-bound token using mTLS or an instance identity
+// bound token using ALTS.
+type TokenBindingType int
+
+const (
+	// NoBinding specifies that requested tokens are not required to have a
+	// binding. This is the default option.
+	NoBinding TokenBindingType = iota
+	// MTLSHardBinding specifies that a hard-bound token should be requested
+	// using an mTLS with S2A channel.
+	MTLSHardBinding
+	// ALTSHardBinding specifies that an instance identity bound token should
+	// be requested using an ALTS channel.
+	ALTSHardBinding
+)
+
+// OnGCE reports whether this process is running in Google Cloud.
+func OnGCE() bool {
+	// TODO(codyoss): once all libs use this auth lib move metadata check here
+	return allowOnGCECheck && metadata.OnGCE()
+}
+
+// DetectDefault searches for "Application Default Credentials" and returns
+// a credential based on the [DetectOptions] provided.
+//
+// It looks for credentials in the following places, preferring the first
+// location found:
+//
+//   - A JSON file whose path is specified by the GOOGLE_APPLICATION_CREDENTIALS
+//     environment variable. For workload identity federation, refer to
+//     https://cloud.google.com/iam/docs/how-to#using-workload-identity-federation
+//     on how to generate the JSON configuration file for on-prem/non-Google
+//     cloud platforms.
+//   - A JSON file in a location known to the gcloud command-line tool. On
+//     Windows, this is %APPDATA%/gcloud/application_default_credentials.json. On
+//     other systems, $HOME/.config/gcloud/application_default_credentials.json.
+//   - On Google Compute Engine, Google App Engine standard second generation
+//     runtimes, and Google App Engine flexible environment, it fetches
+//     credentials from the metadata server.
+//
+// Important: If you accept a credential configuration (credential
+// JSON/File/Stream) from an external source for authentication to Google
+// Cloud Platform, you must validate it before providing it to any Google
+// API or library. Providing an unvalidated credential configuration to
+// Google APIs can compromise the security of your systems and data. For
+// more information, refer to [Validate credential configurations from
+// external sources](https://cloud.google.com/docs/authentication/external/externally-sourced-credentials).
+func DetectDefault(opts *DetectOptions) (*auth.Credentials, error) {
+	if err := opts.validate(); err != nil {
+		return nil, err
+	}
+	trustBoundaryEnabled, err := trustboundary.IsEnabled()
+	if err != nil {
+		return nil, err
+	}
+	if len(opts.CredentialsJSON) > 0 {
+		return readCredentialsFileJSON(opts.CredentialsJSON, opts)
+	}
+	if opts.CredentialsFile != "" {
+		return readCredentialsFile(opts.CredentialsFile, opts)
+	}
+	if filename := os.Getenv(credsfile.GoogleAppCredsEnvVar); filename != "" {
+		creds, err := readCredentialsFile(filename, opts)
+		if err != nil {
+			return nil, err
+		}
+		return creds, nil
+	}
+
+	fileName := credsfile.GetWellKnownFileName()
+	if b, err := os.ReadFile(fileName); err == nil {
+		return readCredentialsFileJSON(b, opts)
+	}
+
+	if OnGCE() {
+		metadataClient := metadata.NewWithOptions(&metadata.Options{
+			Logger:           opts.logger(),
+			UseDefaultClient: true,
+		})
+		gceUniverseDomainProvider := &internal.ComputeUniverseDomainProvider{
+			MetadataClient: metadataClient,
+		}
+
+		tp := computeTokenProvider(opts, metadataClient)
+		if trustBoundaryEnabled {
+			gceConfigProvider := trustboundary.NewGCEConfigProvider(gceUniverseDomainProvider)
+			var err error
+			tp, err = trustboundary.NewProvider(opts.client(), gceConfigProvider, opts.logger(), tp)
+			if err != nil {
+				return nil, fmt.Errorf("credentials: failed to initialize GCE trust boundary provider: %w", err)
+			}
+
+		}
+		return auth.NewCredentials(&auth.CredentialsOptions{
+			TokenProvider: tp,
+			ProjectIDProvider: auth.CredentialsPropertyFunc(func(ctx context.Context) (string, error) {
+				return metadataClient.ProjectIDWithContext(ctx)
+			}),
+			UniverseDomainProvider: gceUniverseDomainProvider,
+		}), nil
+	}
+
+	return nil, fmt.Errorf("credentials: could not find default credentials. See %v for more information", adcSetupURL)
+}
+
+// DetectOptions provides configuration for [DetectDefault].
+type DetectOptions struct {
+	// Scopes that credentials tokens should have. Example:
+	// https://www.googleapis.com/auth/cloud-platform. Required if Audience is
+	// not provided.
+	Scopes []string
+	// TokenBindingType specifies the type of binding used when requesting a
+	// token whether to request a hard-bound token using mTLS or an instance
+	// identity bound token using ALTS. Optional.
+	TokenBindingType TokenBindingType
+	// Audience that credentials tokens should have. Only applicable for 2LO
+	// flows with service accounts. If specified, scopes should not be provided.
+	Audience string
+	// Subject is the user email used for [domain wide delegation](https://developers.google.com/identity/protocols/oauth2/service-account#delegatingauthority).
+	// Optional.
+	Subject string
+	// EarlyTokenRefresh configures how early before a token expires that it
+	// should be refreshed. Once the token’s time until expiration has entered
+	// this refresh window the token is considered valid but stale. If unset,
+	// the default value is 3 minutes and 45 seconds. Optional.
+	EarlyTokenRefresh time.Duration
+	// DisableAsyncRefresh configures a synchronous workflow that refreshes
+	// stale tokens while blocking. The default is false. Optional.
+	DisableAsyncRefresh bool
+	// AuthHandlerOptions configures an authorization handler and other options
+	// for 3LO flows. It is required, and only used, for client credential
+	// flows.
+	AuthHandlerOptions *auth.AuthorizationHandlerOptions
+	// TokenURL allows to set the token endpoint for user credential flows. If
+	// unset the default value is: https://oauth2.googleapis.com/token.
+	// Optional.
+	TokenURL string
+	// STSAudience is the audience sent to when retrieving an STS token.
+	// Currently this only used for GDCH auth flow, for which it is required.
+	STSAudience string
+	// CredentialsFile overrides detection logic and sources a credential file
+	// from the provided filepath. If provided, CredentialsJSON must not be.
+	// Optional.
+	//
+	// Deprecated: This field is deprecated because of a potential security risk.
+	// It does not validate the credential configuration. The security risk occurs
+	// when a credential configuration is accepted from a source that is not
+	// under your control and used without validation on your side.
+	//
+	// If you know that you will be loading credential configurations of a
+	// specific type, it is recommended to use a credential-type-specific
+	// NewCredentialsFromFile method. This will ensure that an unexpected
+	// credential type with potential for malicious intent is not loaded
+	// unintentionally. You might still have to do validation for certain
+	// credential types. Please follow the recommendation for that method. For
+	// example, if you want to load only service accounts, you can use
+	//
+	//	creds, err := credentials.NewCredentialsFromFile(ctx, credentials.ServiceAccount, filename, opts)
+	//
+	// If you are loading your credential configuration from an untrusted source
+	// and have not mitigated the risks (e.g. by validating the configuration
+	// yourself), make these changes as soon as possible to prevent security
+	// risks to your environment.
+	//
+	// Regardless of the method used, it is always your responsibility to
+	// validate configurations received from external sources.
+	//
+	// For more details see:
+	// https://cloud.google.com/docs/authentication/external/externally-sourced-credentials
+	CredentialsFile string
+	// CredentialsJSON overrides detection logic and uses the JSON bytes as the
+	// source for the credential. If provided, CredentialsFile must not be.
+	// Optional.
+	//
+	// Deprecated: This field is deprecated because of a potential security risk.
+	// It does not validate the credential configuration. The security risk occurs
+	// when a credential configuration is accepted from a source that is not
+	// under your control and used without validation on your side.
+	//
+	// If you know that you will be loading credential configurations of a
+	// specific type, it is recommended to use a credential-type-specific
+	// NewCredentialsFromJSON method. This will ensure that an unexpected
+	// credential type with potential for malicious intent is not loaded
+	// unintentionally. You might still have to do validation for certain
+	// credential types. Please follow the recommendation for that method. For
+	// example, if you want to load only service accounts, you can use
+	//
+	//	creds, err := credentials.NewCredentialsFromJSON(ctx, credentials.ServiceAccount, json, opts)
+	//
+	// If you are loading your credential configuration from an untrusted source
+	// and have not mitigated the risks (e.g. by validating the configuration
+	// yourself), make these changes as soon as possible to prevent security
+	// risks to your environment.
+	//
+	// Regardless of the method used, it is always your responsibility to
+	// validate configurations received from external sources.
+	//
+	// For more details see:
+	// https://cloud.google.com/docs/authentication/external/externally-sourced-credentials
+	CredentialsJSON []byte
+	// UseSelfSignedJWT directs service account based credentials to create a
+	// self-signed JWT with the private key found in the file, skipping any
+	// network requests that would normally be made. Optional.
+	UseSelfSignedJWT bool
+	// Client configures the underlying client used to make network requests
+	// when fetching tokens. Optional.
+	Client *http.Client
+	// UniverseDomain is the default service domain for a given Cloud universe.
+	// The default value is "googleapis.com". This option is ignored for
+	// authentication flows that do not support universe domain. Optional.
+	UniverseDomain string
+	// Logger is used for debug logging. If provided, logging will be enabled
+	// at the loggers configured level. By default logging is disabled unless
+	// enabled by setting GOOGLE_SDK_GO_LOGGING_LEVEL in which case a default
+	// logger will be used. Optional.
+	Logger *slog.Logger
+}
+
+// NewCredentialsFromFile creates a [cloud.google.com/go/auth.Credentials] from
+// the provided file. The credType argument specifies the expected credential
+// type. If the file content does not match the expected type, an error is
+// returned.
+//
+// Important: If you accept a credential configuration (credential
+// JSON/File/Stream) from an external source for authentication to Google
+// Cloud Platform, you must validate it before providing it to any Google
+// API or library. Providing an unvalidated credential configuration to
+// Google APIs can compromise the security of your systems and data. For
+// more information, refer to [Validate credential configurations from
+// external sources](https://cloud.google.com/docs/authentication/external/externally-sourced-credentials).
+func NewCredentialsFromFile(credType CredType, filename string, opts *DetectOptions) (*auth.Credentials, error) {
+	b, err := os.ReadFile(filename)
+	if err != nil {
+		return nil, err
+	}
+	return NewCredentialsFromJSON(credType, b, opts)
+}
+
+// NewCredentialsFromJSON creates a [cloud.google.com/go/auth.Credentials] from
+// the provided JSON bytes. The credType argument specifies the expected
+// credential type. If the JSON does not match the expected type, an error is
+// returned.
+//
+// Important: If you accept a credential configuration (credential
+// JSON/File/Stream) from an external source for authentication to Google
+// Cloud Platform, you must validate it before providing it to any Google
+// API or library. Providing an unvalidated credential configuration to
+// Google APIs can compromise the security of your systems and data. For
+// more information, refer to [Validate credential configurations from
+// external sources](https://cloud.google.com/docs/authentication/external/externally-sourced-credentials).
+func NewCredentialsFromJSON(credType CredType, b []byte, opts *DetectOptions) (*auth.Credentials, error) {
+	if err := checkCredentialType(b, credType); err != nil {
+		return nil, err
+	}
+	// We can't use readCredentialsFileJSON because it does auto-detection
+	// for client_credentials.json which we don't support here (no type field).
+	// Instead, we call fileCredentials just as readCredentialsFileJSON does
+	// when it doesn't detect client_credentials.json.
+	return fileCredentials(b, opts)
+}
+
+func checkCredentialType(b []byte, expected CredType) error {
+
+	fileType, err := credsfile.ParseFileType(b)
+	if err != nil {
+		return err
+	}
+	if CredType(fileType) != expected {
+		return fmt.Errorf("credentials: expected type %q, found %q", expected, fileType)
+	}
+	return nil
+}
+
+func (o *DetectOptions) validate() error {
+	if o == nil {
+		return errors.New("credentials: options must be provided")
+	}
+	if len(o.Scopes) > 0 && o.Audience != "" {
+		return errors.New("credentials: both scopes and audience were provided")
+	}
+	if len(o.CredentialsJSON) > 0 && o.CredentialsFile != "" {
+		return errors.New("credentials: both credentials file and JSON were provided")
+	}
+	return nil
+}
+
+func (o *DetectOptions) tokenURL() string {
+	if o.TokenURL != "" {
+		return o.TokenURL
+	}
+	return googleTokenURL
+}
+
+func (o *DetectOptions) scopes() []string {
+	scopes := make([]string, len(o.Scopes))
+	copy(scopes, o.Scopes)
+	return scopes
+}
+
+func (o *DetectOptions) client() *http.Client {
+	if o.Client != nil {
+		return o.Client
+	}
+	return internal.DefaultClient()
+}
+
+func (o *DetectOptions) logger() *slog.Logger {
+	return internallog.New(o.Logger)
+}
+
+func readCredentialsFile(filename string, opts *DetectOptions) (*auth.Credentials, error) {
+	b, err := os.ReadFile(filename)
+	if err != nil {
+		return nil, err
+	}
+	return readCredentialsFileJSON(b, opts)
+}
+
+func readCredentialsFileJSON(b []byte, opts *DetectOptions) (*auth.Credentials, error) {
+	// attempt to parse jsonData as a Google Developers Console client_credentials.json.
+	config := clientCredConfigFromJSON(b, opts)
+	if config != nil {
+		if config.AuthHandlerOpts == nil {
+			return nil, errors.New("credentials: auth handler must be specified for this credential filetype")
+		}
+		tp, err := auth.New3LOTokenProvider(config)
+		if err != nil {
+			return nil, err
+		}
+		return auth.NewCredentials(&auth.CredentialsOptions{
+			TokenProvider: tp,
+			JSON:          b,
+		}), nil
+	}
+	return fileCredentials(b, opts)
+}
+
+func clientCredConfigFromJSON(b []byte, opts *DetectOptions) *auth.Options3LO {
+	var creds credsfile.ClientCredentialsFile
+	var c *credsfile.Config3LO
+	if err := json.Unmarshal(b, &creds); err != nil {
+		return nil
+	}
+	switch {
+	case creds.Web != nil:
+		c = creds.Web
+	case creds.Installed != nil:
+		c = creds.Installed
+	default:
+		return nil
+	}
+	if len(c.RedirectURIs) < 1 {
+		return nil
+	}
+	var handleOpts *auth.AuthorizationHandlerOptions
+	if opts.AuthHandlerOptions != nil {
+		handleOpts = &auth.AuthorizationHandlerOptions{
+			Handler:  opts.AuthHandlerOptions.Handler,
+			State:    opts.AuthHandlerOptions.State,
+			PKCEOpts: opts.AuthHandlerOptions.PKCEOpts,
+		}
+	}
+	return &auth.Options3LO{
+		ClientID:         c.ClientID,
+		ClientSecret:     c.ClientSecret,
+		RedirectURL:      c.RedirectURIs[0],
+		Scopes:           opts.scopes(),
+		AuthURL:          c.AuthURI,
+		TokenURL:         c.TokenURI,
+		Client:           opts.client(),
+		Logger:           opts.logger(),
+		EarlyTokenExpiry: opts.EarlyTokenRefresh,
+		AuthHandlerOpts:  handleOpts,
+		// TODO(codyoss): refactor this out. We need to add in auto-detection
+		// for this use case.
+		AuthStyle: auth.StyleInParams,
+	}
+}

vendor/cloud.google.com/go/auth/credentials/doc.go

@@ -0,0 +1,45 @@
+// Copyright 2023 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Package credentials provides support for making OAuth2 authorized and
+// authenticated HTTP requests to Google APIs. It supports the Web server flow,
+// client-side credentials, service accounts, Google Compute Engine service
+// accounts, Google App Engine service accounts and workload identity federation
+// from non-Google cloud platforms.
+//
+// A brief overview of the package follows. For more information, please read
+// https://developers.google.com/accounts/docs/OAuth2
+// and
+// https://developers.google.com/accounts/docs/application-default-credentials.
+// For more information on using workload identity federation, refer to
+// https://cloud.google.com/iam/docs/how-to#using-workload-identity-federation.
+//
+// # Credentials
+//
+// The [cloud.google.com/go/auth.Credentials] type represents Google
+// credentials, including Application Default Credentials.
+//
+// Use [DetectDefault] to obtain Application Default Credentials.
+//
+// Application Default Credentials support workload identity federation to
+// access Google Cloud resources from non-Google Cloud platforms including Amazon
+// Web Services (AWS), Microsoft Azure or any identity provider that supports
+// OpenID Connect (OIDC). Workload identity federation is recommended for
+// non-Google Cloud environments as it avoids the need to download, manage, and
+// store service account private keys locally.
+//
+// # Workforce Identity Federation
+//
+// For more information on this feature see [cloud.google.com/go/auth/credentials/externalaccount].
+package credentials

vendor/cloud.google.com/go/auth/credentials/filetypes.go

@@ -0,0 +1,329 @@
+// Copyright 2023 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package credentials
+
+import (
+	"errors"
+	"fmt"
+
+	"cloud.google.com/go/auth"
+	"cloud.google.com/go/auth/credentials/internal/externalaccount"
+	"cloud.google.com/go/auth/credentials/internal/externalaccountuser"
+	"cloud.google.com/go/auth/credentials/internal/gdch"
+	"cloud.google.com/go/auth/credentials/internal/impersonate"
+	internalauth "cloud.google.com/go/auth/internal"
+	"cloud.google.com/go/auth/internal/credsfile"
+	"cloud.google.com/go/auth/internal/trustboundary"
+)
+
+const cloudPlatformScope = "https://www.googleapis.com/auth/cloud-platform"
+
+func fileCredentials(b []byte, opts *DetectOptions) (*auth.Credentials, error) {
+	fileType, err := credsfile.ParseFileType(b)
+	if err != nil {
+		return nil, err
+	}
+	if fileType == "" {
+		return nil, errors.New("credentials: unsupported unidentified file type")
+	}
+
+	var projectID, universeDomain string
+	var tp auth.TokenProvider
+	switch CredType(fileType) {
+	case ServiceAccount:
+		f, err := credsfile.ParseServiceAccount(b)
+		if err != nil {
+			return nil, err
+		}
+		tp, err = handleServiceAccount(f, opts)
+		if err != nil {
+			return nil, err
+		}
+		projectID = f.ProjectID
+		universeDomain = resolveUniverseDomain(opts.UniverseDomain, f.UniverseDomain)
+	case AuthorizedUser:
+		f, err := credsfile.ParseUserCredentials(b)
+		if err != nil {
+			return nil, err
+		}
+		tp, err = handleUserCredential(f, opts)
+		if err != nil {
+			return nil, err
+		}
+		universeDomain = f.UniverseDomain
+	case ExternalAccount:
+		f, err := credsfile.ParseExternalAccount(b)
+		if err != nil {
+			return nil, err
+		}
+		tp, err = handleExternalAccount(f, opts)
+		if err != nil {
+			return nil, err
+		}
+		universeDomain = resolveUniverseDomain(opts.UniverseDomain, f.UniverseDomain)
+	case ExternalAccountAuthorizedUser:
+		f, err := credsfile.ParseExternalAccountAuthorizedUser(b)
+		if err != nil {
+			return nil, err
+		}
+		tp, err = handleExternalAccountAuthorizedUser(f, opts)
+		if err != nil {
+			return nil, err
+		}
+		universeDomain = f.UniverseDomain
+	case ImpersonatedServiceAccount:
+		f, err := credsfile.ParseImpersonatedServiceAccount(b)
+		if err != nil {
+			return nil, err
+		}
+		tp, err = handleImpersonatedServiceAccount(f, opts)
+		if err != nil {
+			return nil, err
+		}
+		universeDomain = resolveUniverseDomain(opts.UniverseDomain, f.UniverseDomain)
+	case GDCHServiceAccount:
+		f, err := credsfile.ParseGDCHServiceAccount(b)
+		if err != nil {
+			return nil, err
+		}
+		tp, err = handleGDCHServiceAccount(f, opts)
+		if err != nil {
+			return nil, err
+		}
+		projectID = f.Project
+		universeDomain = f.UniverseDomain
+	default:
+		return nil, fmt.Errorf("credentials: unsupported filetype %q", fileType)
+	}
+	return auth.NewCredentials(&auth.CredentialsOptions{
+		TokenProvider: auth.NewCachedTokenProvider(tp, &auth.CachedTokenProviderOptions{
+			ExpireEarly: opts.EarlyTokenRefresh,
+		}),
+		JSON:              b,
+		ProjectIDProvider: internalauth.StaticCredentialsProperty(projectID),
+		// TODO(codyoss): only set quota project here if there was a user override
+		UniverseDomainProvider: internalauth.StaticCredentialsProperty(universeDomain),
+	}), nil
+}
+
+// resolveUniverseDomain returns optsUniverseDomain if non-empty, in order to
+// support configuring universe-specific credentials in code. Auth flows
+// unsupported for universe domain should not use this func, but should instead
+// simply set the file universe domain on the credentials.
+func resolveUniverseDomain(optsUniverseDomain, fileUniverseDomain string) string {
+	if optsUniverseDomain != "" {
+		return optsUniverseDomain
+	}
+	return fileUniverseDomain
+}
+
+func handleServiceAccount(f *credsfile.ServiceAccountFile, opts *DetectOptions) (auth.TokenProvider, error) {
+	ud := resolveUniverseDomain(opts.UniverseDomain, f.UniverseDomain)
+	if opts.UseSelfSignedJWT {
+		return configureSelfSignedJWT(f, opts)
+	} else if ud != "" && ud != internalauth.DefaultUniverseDomain {
+		// For non-GDU universe domains, token exchange is impossible and services
+		// must support self-signed JWTs.
+		opts.UseSelfSignedJWT = true
+		return configureSelfSignedJWT(f, opts)
+	}
+	opts2LO := &auth.Options2LO{
+		Email:          f.ClientEmail,
+		PrivateKey:     []byte(f.PrivateKey),
+		PrivateKeyID:   f.PrivateKeyID,
+		Scopes:         opts.scopes(),
+		TokenURL:       f.TokenURL,
+		Subject:        opts.Subject,
+		Client:         opts.client(),
+		Logger:         opts.logger(),
+		UniverseDomain: ud,
+	}
+	if opts2LO.TokenURL == "" {
+		opts2LO.TokenURL = jwtTokenURL
+	}
+
+	tp, err := auth.New2LOTokenProvider(opts2LO)
+	if err != nil {
+		return nil, err
+	}
+
+	trustBoundaryEnabled, err := trustboundary.IsEnabled()
+	if err != nil {
+		return nil, err
+	}
+	if !trustBoundaryEnabled {
+		return tp, nil
+	}
+	saConfig := trustboundary.NewServiceAccountConfigProvider(opts2LO.Email, opts2LO.UniverseDomain)
+	return trustboundary.NewProvider(opts.client(), saConfig, opts.logger(), tp)
+}
+
+func handleUserCredential(f *credsfile.UserCredentialsFile, opts *DetectOptions) (auth.TokenProvider, error) {
+	opts3LO := &auth.Options3LO{
+		ClientID:         f.ClientID,
+		ClientSecret:     f.ClientSecret,
+		Scopes:           opts.scopes(),
+		AuthURL:          googleAuthURL,
+		TokenURL:         opts.tokenURL(),
+		AuthStyle:        auth.StyleInParams,
+		EarlyTokenExpiry: opts.EarlyTokenRefresh,
+		RefreshToken:     f.RefreshToken,
+		Client:           opts.client(),
+		Logger:           opts.logger(),
+	}
+	return auth.New3LOTokenProvider(opts3LO)
+}
+
+func handleExternalAccount(f *credsfile.ExternalAccountFile, opts *DetectOptions) (auth.TokenProvider, error) {
+	externalOpts := &externalaccount.Options{
+		Audience:                       f.Audience,
+		SubjectTokenType:               f.SubjectTokenType,
+		TokenURL:                       f.TokenURL,
+		TokenInfoURL:                   f.TokenInfoURL,
+		ServiceAccountImpersonationURL: f.ServiceAccountImpersonationURL,
+		ClientSecret:                   f.ClientSecret,
+		ClientID:                       f.ClientID,
+		CredentialSource:               f.CredentialSource,
+		QuotaProjectID:                 f.QuotaProjectID,
+		Scopes:                         opts.scopes(),
+		WorkforcePoolUserProject:       f.WorkforcePoolUserProject,
+		Client:                         opts.client(),
+		Logger:                         opts.logger(),
+		IsDefaultClient:                opts.Client == nil,
+	}
+	if f.ServiceAccountImpersonation != nil {
+		externalOpts.ServiceAccountImpersonationLifetimeSeconds = f.ServiceAccountImpersonation.TokenLifetimeSeconds
+	}
+	tp, err := externalaccount.NewTokenProvider(externalOpts)
+	if err != nil {
+		return nil, err
+	}
+	trustBoundaryEnabled, err := trustboundary.IsEnabled()
+	if err != nil {
+		return nil, err
+	}
+	if !trustBoundaryEnabled {
+		return tp, nil
+	}
+
+	ud := resolveUniverseDomain(opts.UniverseDomain, f.UniverseDomain)
+	var configProvider trustboundary.ConfigProvider
+
+	if f.ServiceAccountImpersonationURL == "" {
+		// No impersonation, this is a direct external account credential.
+		// The trust boundary is based on the workload/workforce pool.
+		var err error
+		configProvider, err = trustboundary.NewExternalAccountConfigProvider(f.Audience, ud)
+		if err != nil {
+			return nil, err
+		}
+	} else {
+		// Impersonation is used. The trust boundary is based on the target service account.
+		targetSAEmail, err := impersonate.ExtractServiceAccountEmail(f.ServiceAccountImpersonationURL)
+		if err != nil {
+			return nil, fmt.Errorf("credentials: could not extract target service account email for trust boundary: %w", err)
+		}
+		configProvider = trustboundary.NewServiceAccountConfigProvider(targetSAEmail, ud)
+	}
+
+	return trustboundary.NewProvider(opts.client(), configProvider, opts.logger(), tp)
+}
+
+func handleExternalAccountAuthorizedUser(f *credsfile.ExternalAccountAuthorizedUserFile, opts *DetectOptions) (auth.TokenProvider, error) {
+	externalOpts := &externalaccountuser.Options{
+		Audience:     f.Audience,
+		RefreshToken: f.RefreshToken,
+		TokenURL:     f.TokenURL,
+		TokenInfoURL: f.TokenInfoURL,
+		ClientID:     f.ClientID,
+		ClientSecret: f.ClientSecret,
+		Scopes:       opts.scopes(),
+		Client:       opts.client(),
+		Logger:       opts.logger(),
+	}
+	tp, err := externalaccountuser.NewTokenProvider(externalOpts)
+	if err != nil {
+		return nil, err
+	}
+	trustBoundaryEnabled, err := trustboundary.IsEnabled()
+	if err != nil {
+		return nil, err
+	}
+	if !trustBoundaryEnabled {
+		return tp, nil
+	}
+
+	ud := resolveUniverseDomain(opts.UniverseDomain, f.UniverseDomain)
+	configProvider, err := trustboundary.NewExternalAccountConfigProvider(f.Audience, ud)
+	if err != nil {
+		return nil, err
+	}
+	return trustboundary.NewProvider(opts.client(), configProvider, opts.logger(), tp)
+}
+
+func handleImpersonatedServiceAccount(f *credsfile.ImpersonatedServiceAccountFile, opts *DetectOptions) (auth.TokenProvider, error) {
+	if f.ServiceAccountImpersonationURL == "" || f.CredSource == nil {
+		return nil, errors.New("missing 'source_credentials' field or 'service_account_impersonation_url' in credentials")
+	}
+
+	sourceOpts := *opts
+
+	// Source credential needs IAM or Cloud Platform scope to call the
+	// iamcredentials endpoint. The scopes provided by the user are for the
+	// impersonated credentials.
+	sourceOpts.Scopes = []string{cloudPlatformScope}
+	sourceTP, err := fileCredentials(f.CredSource, &sourceOpts)
+	if err != nil {
+		return nil, err
+	}
+	ud := resolveUniverseDomain(opts.UniverseDomain, f.UniverseDomain)
+	scopes := opts.scopes()
+	if len(scopes) == 0 {
+		scopes = f.Scopes
+	}
+	impOpts := &impersonate.Options{
+		URL:            f.ServiceAccountImpersonationURL,
+		Scopes:         scopes,
+		Tp:             sourceTP,
+		Delegates:      f.Delegates,
+		Client:         opts.client(),
+		Logger:         opts.logger(),
+		UniverseDomain: ud,
+	}
+	tp, err := impersonate.NewTokenProvider(impOpts)
+	if err != nil {
+		return nil, err
+	}
+	trustBoundaryEnabled, err := trustboundary.IsEnabled()
+	if err != nil {
+		return nil, err
+	}
+	if !trustBoundaryEnabled {
+		return tp, nil
+	}
+	targetSAEmail, err := impersonate.ExtractServiceAccountEmail(f.ServiceAccountImpersonationURL)
+	if err != nil {
+		return nil, fmt.Errorf("credentials: could not extract target service account email for trust boundary: %w", err)
+	}
+	targetSAConfig := trustboundary.NewServiceAccountConfigProvider(targetSAEmail, ud)
+	return trustboundary.NewProvider(opts.client(), targetSAConfig, opts.logger(), tp)
+}
+func handleGDCHServiceAccount(f *credsfile.GDCHServiceAccountFile, opts *DetectOptions) (auth.TokenProvider, error) {
+	return gdch.NewTokenProvider(f, &gdch.Options{
+		STSAudience: opts.STSAudience,
+		Client:      opts.client(),
+		Logger:      opts.logger(),
+	})
+}

vendor/cloud.google.com/go/auth/credentials/internal/externalaccount/aws_provider.go

@@ -0,0 +1,531 @@
+// Copyright 2023 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package externalaccount
+
+import (
+	"bytes"
+	"context"
+	"crypto/hmac"
+	"crypto/sha256"
+	"encoding/hex"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"log/slog"
+	"net/http"
+	"net/url"
+	"os"
+	"path"
+	"sort"
+	"strings"
+	"time"
+
+	"cloud.google.com/go/auth/internal"
+	"github.com/googleapis/gax-go/v2/internallog"
+)
+
+var (
+	// getenv aliases os.Getenv for testing
+	getenv = os.Getenv
+)
+
+const (
+	// AWS Signature Version 4 signing algorithm identifier.
+	awsAlgorithm = "AWS4-HMAC-SHA256"
+
+	// The termination string for the AWS credential scope value as defined in
+	// https://docs.aws.amazon.com/general/latest/gr/sigv4-create-string-to-sign.html
+	awsRequestType = "aws4_request"
+
+	// The AWS authorization header name for the security session token if available.
+	awsSecurityTokenHeader = "x-amz-security-token"
+
+	// The name of the header containing the session token for metadata endpoint calls
+	awsIMDSv2SessionTokenHeader = "X-aws-ec2-metadata-token"
+
+	awsIMDSv2SessionTTLHeader = "X-aws-ec2-metadata-token-ttl-seconds"
+
+	awsIMDSv2SessionTTL = "300"
+
+	// The AWS authorization header name for the auto-generated date.
+	awsDateHeader = "x-amz-date"
+
+	defaultRegionalCredentialVerificationURL = "https://sts.{region}.amazonaws.com?Action=GetCallerIdentity&Version=2011-06-15"
+
+	// Supported AWS configuration environment variables.
+	awsAccessKeyIDEnvVar     = "AWS_ACCESS_KEY_ID"
+	awsDefaultRegionEnvVar   = "AWS_DEFAULT_REGION"
+	awsRegionEnvVar          = "AWS_REGION"
+	awsSecretAccessKeyEnvVar = "AWS_SECRET_ACCESS_KEY"
+	awsSessionTokenEnvVar    = "AWS_SESSION_TOKEN"
+
+	awsTimeFormatLong  = "20060102T150405Z"
+	awsTimeFormatShort = "20060102"
+	awsProviderType    = "aws"
+)
+
+type awsSubjectProvider struct {
+	EnvironmentID               string
+	RegionURL                   string
+	RegionalCredVerificationURL string
+	CredVerificationURL         string
+	IMDSv2SessionTokenURL       string
+	TargetResource              string
+	requestSigner               *awsRequestSigner
+	region                      string
+	securityCredentialsProvider AwsSecurityCredentialsProvider
+	reqOpts                     *RequestOptions
+
+	Client *http.Client
+	logger *slog.Logger
+}
+
+func (sp *awsSubjectProvider) subjectToken(ctx context.Context) (string, error) {
+	// Set Defaults
+	if sp.RegionalCredVerificationURL == "" {
+		sp.RegionalCredVerificationURL = defaultRegionalCredentialVerificationURL
+	}
+	headers := make(map[string]string)
+	if sp.shouldUseMetadataServer() {
+		awsSessionToken, err := sp.getAWSSessionToken(ctx)
+		if err != nil {
+			return "", err
+		}
+
+		if awsSessionToken != "" {
+			headers[awsIMDSv2SessionTokenHeader] = awsSessionToken
+		}
+	}
+
+	awsSecurityCredentials, err := sp.getSecurityCredentials(ctx, headers)
+	if err != nil {
+		return "", err
+	}
+	if sp.region, err = sp.getRegion(ctx, headers); err != nil {
+		return "", err
+	}
+	sp.requestSigner = &awsRequestSigner{
+		RegionName:             sp.region,
+		AwsSecurityCredentials: awsSecurityCredentials,
+	}
+
+	// Generate the signed request to AWS STS GetCallerIdentity API.
+	// Use the required regional endpoint. Otherwise, the request will fail.
+	req, err := http.NewRequestWithContext(ctx, "POST", strings.Replace(sp.RegionalCredVerificationURL, "{region}", sp.region, 1), nil)
+	if err != nil {
+		return "", err
+	}
+	// The full, canonical resource name of the workload identity pool
+	// provider, with or without the HTTPS prefix.
+	// Including this header as part of the signature is recommended to
+	// ensure data integrity.
+	if sp.TargetResource != "" {
+		req.Header.Set("x-goog-cloud-target-resource", sp.TargetResource)
+	}
+	sp.requestSigner.signRequest(req)
+
+	/*
+	   The GCP STS endpoint expects the headers to be formatted as:
+	   # [
+	   #   {key: 'x-amz-date', value: '...'},
+	   #   {key: 'Authorization', value: '...'},
+	   #   ...
+	   # ]
+	   # And then serialized as:
+	   # quote(json.dumps({
+	   #   url: '...',
+	   #   method: 'POST',
+	   #   headers: [{key: 'x-amz-date', value: '...'}, ...]
+	   # }))
+	*/
+
+	awsSignedReq := awsRequest{
+		URL:    req.URL.String(),
+		Method: "POST",
+	}
+	for headerKey, headerList := range req.Header {
+		for _, headerValue := range headerList {
+			awsSignedReq.Headers = append(awsSignedReq.Headers, awsRequestHeader{
+				Key:   headerKey,
+				Value: headerValue,
+			})
+		}
+	}
+	sort.Slice(awsSignedReq.Headers, func(i, j int) bool {
+		headerCompare := strings.Compare(awsSignedReq.Headers[i].Key, awsSignedReq.Headers[j].Key)
+		if headerCompare == 0 {
+			return strings.Compare(awsSignedReq.Headers[i].Value, awsSignedReq.Headers[j].Value) < 0
+		}
+		return headerCompare < 0
+	})
+
+	result, err := json.Marshal(awsSignedReq)
+	if err != nil {
+		return "", err
+	}
+	return url.QueryEscape(string(result)), nil
+}
+
+func (sp *awsSubjectProvider) providerType() string {
+	if sp.securityCredentialsProvider != nil {
+		return programmaticProviderType
+	}
+	return awsProviderType
+}
+
+func (sp *awsSubjectProvider) getAWSSessionToken(ctx context.Context) (string, error) {
+	if sp.IMDSv2SessionTokenURL == "" {
+		return "", nil
+	}
+	req, err := http.NewRequestWithContext(ctx, "PUT", sp.IMDSv2SessionTokenURL, nil)
+	if err != nil {
+		return "", err
+	}
+	req.Header.Set(awsIMDSv2SessionTTLHeader, awsIMDSv2SessionTTL)
+
+	sp.logger.DebugContext(ctx, "aws session token request", "request", internallog.HTTPRequest(req, nil))
+	resp, body, err := internal.DoRequest(sp.Client, req)
+	if err != nil {
+		return "", err
+	}
+	sp.logger.DebugContext(ctx, "aws session token response", "response", internallog.HTTPResponse(resp, body))
+	if resp.StatusCode != http.StatusOK {
+		return "", fmt.Errorf("credentials: unable to retrieve AWS session token: %s", body)
+	}
+	return string(body), nil
+}
+
+func (sp *awsSubjectProvider) getRegion(ctx context.Context, headers map[string]string) (string, error) {
+	if sp.securityCredentialsProvider != nil {
+		return sp.securityCredentialsProvider.AwsRegion(ctx, sp.reqOpts)
+	}
+	if canRetrieveRegionFromEnvironment() {
+		if envAwsRegion := getenv(awsRegionEnvVar); envAwsRegion != "" {
+			return envAwsRegion, nil
+		}
+		return getenv(awsDefaultRegionEnvVar), nil
+	}
+
+	if sp.RegionURL == "" {
+		return "", errors.New("credentials: unable to determine AWS region")
+	}
+
+	req, err := http.NewRequestWithContext(ctx, "GET", sp.RegionURL, nil)
+	if err != nil {
+		return "", err
+	}
+
+	for name, value := range headers {
+		req.Header.Add(name, value)
+	}
+	sp.logger.DebugContext(ctx, "aws region request", "request", internallog.HTTPRequest(req, nil))
+	resp, body, err := internal.DoRequest(sp.Client, req)
+	if err != nil {
+		return "", err
+	}
+	sp.logger.DebugContext(ctx, "aws region response", "response", internallog.HTTPResponse(resp, body))
+	if resp.StatusCode != http.StatusOK {
+		return "", fmt.Errorf("credentials: unable to retrieve AWS region - %s", body)
+	}
+
+	// This endpoint will return the region in format: us-east-2b.
+	// Only the us-east-2 part should be used.
+	bodyLen := len(body)
+	if bodyLen == 0 {
+		return "", nil
+	}
+	return string(body[:bodyLen-1]), nil
+}
+
+func (sp *awsSubjectProvider) getSecurityCredentials(ctx context.Context, headers map[string]string) (result *AwsSecurityCredentials, err error) {
+	if sp.securityCredentialsProvider != nil {
+		return sp.securityCredentialsProvider.AwsSecurityCredentials(ctx, sp.reqOpts)
+	}
+	if canRetrieveSecurityCredentialFromEnvironment() {
+		return &AwsSecurityCredentials{
+			AccessKeyID:     getenv(awsAccessKeyIDEnvVar),
+			SecretAccessKey: getenv(awsSecretAccessKeyEnvVar),
+			SessionToken:    getenv(awsSessionTokenEnvVar),
+		}, nil
+	}
+
+	roleName, err := sp.getMetadataRoleName(ctx, headers)
+	if err != nil {
+		return
+	}
+	credentials, err := sp.getMetadataSecurityCredentials(ctx, roleName, headers)
+	if err != nil {
+		return
+	}
+
+	if credentials.AccessKeyID == "" {
+		return result, errors.New("credentials: missing AccessKeyId credential")
+	}
+	if credentials.SecretAccessKey == "" {
+		return result, errors.New("credentials: missing SecretAccessKey credential")
+	}
+
+	return credentials, nil
+}
+
+func (sp *awsSubjectProvider) getMetadataSecurityCredentials(ctx context.Context, roleName string, headers map[string]string) (*AwsSecurityCredentials, error) {
+	var result *AwsSecurityCredentials
+
+	req, err := http.NewRequestWithContext(ctx, "GET", fmt.Sprintf("%s/%s", sp.CredVerificationURL, roleName), nil)
+	if err != nil {
+		return result, err
+	}
+	for name, value := range headers {
+		req.Header.Add(name, value)
+	}
+	sp.logger.DebugContext(ctx, "aws security credential request", "request", internallog.HTTPRequest(req, nil))
+	resp, body, err := internal.DoRequest(sp.Client, req)
+	if err != nil {
+		return result, err
+	}
+	sp.logger.DebugContext(ctx, "aws security credential response", "response", internallog.HTTPResponse(resp, body))
+	if resp.StatusCode != http.StatusOK {
+		return result, fmt.Errorf("credentials: unable to retrieve AWS security credentials - %s", body)
+	}
+	if err := json.Unmarshal(body, &result); err != nil {
+		return nil, err
+	}
+	return result, nil
+}
+
+func (sp *awsSubjectProvider) getMetadataRoleName(ctx context.Context, headers map[string]string) (string, error) {
+	if sp.CredVerificationURL == "" {
+		return "", errors.New("credentials: unable to determine the AWS metadata server security credentials endpoint")
+	}
+	req, err := http.NewRequestWithContext(ctx, "GET", sp.CredVerificationURL, nil)
+	if err != nil {
+		return "", err
+	}
+	for name, value := range headers {
+		req.Header.Add(name, value)
+	}
+
+	sp.logger.DebugContext(ctx, "aws metadata role request", "request", internallog.HTTPRequest(req, nil))
+	resp, body, err := internal.DoRequest(sp.Client, req)
+	if err != nil {
+		return "", err
+	}
+	sp.logger.DebugContext(ctx, "aws metadata role response", "response", internallog.HTTPResponse(resp, body))
+	if resp.StatusCode != http.StatusOK {
+		return "", fmt.Errorf("credentials: unable to retrieve AWS role name - %s", body)
+	}
+	return string(body), nil
+}
+
+// awsRequestSigner is a utility class to sign http requests using a AWS V4 signature.
+type awsRequestSigner struct {
+	RegionName             string
+	AwsSecurityCredentials *AwsSecurityCredentials
+}
+
+// signRequest adds the appropriate headers to an http.Request
+// or returns an error if something prevented this.
+func (rs *awsRequestSigner) signRequest(req *http.Request) error {
+	// req is assumed non-nil
+	signedRequest := cloneRequest(req)
+	timestamp := Now()
+	signedRequest.Header.Set("host", requestHost(req))
+	if rs.AwsSecurityCredentials.SessionToken != "" {
+		signedRequest.Header.Set(awsSecurityTokenHeader, rs.AwsSecurityCredentials.SessionToken)
+	}
+	if signedRequest.Header.Get("date") == "" {
+		signedRequest.Header.Set(awsDateHeader, timestamp.Format(awsTimeFormatLong))
+	}
+	authorizationCode, err := rs.generateAuthentication(signedRequest, timestamp)
+	if err != nil {
+		return err
+	}
+	signedRequest.Header.Set("Authorization", authorizationCode)
+	req.Header = signedRequest.Header
+	return nil
+}
+
+func (rs *awsRequestSigner) generateAuthentication(req *http.Request, timestamp time.Time) (string, error) {
+	canonicalHeaderColumns, canonicalHeaderData := canonicalHeaders(req)
+	dateStamp := timestamp.Format(awsTimeFormatShort)
+	serviceName := ""
+
+	if splitHost := strings.Split(requestHost(req), "."); len(splitHost) > 0 {
+		serviceName = splitHost[0]
+	}
+	credentialScope := strings.Join([]string{dateStamp, rs.RegionName, serviceName, awsRequestType}, "/")
+	requestString, err := canonicalRequest(req, canonicalHeaderColumns, canonicalHeaderData)
+	if err != nil {
+		return "", err
+	}
+	requestHash, err := getSha256([]byte(requestString))
+	if err != nil {
+		return "", err
+	}
+
+	stringToSign := strings.Join([]string{awsAlgorithm, timestamp.Format(awsTimeFormatLong), credentialScope, requestHash}, "\n")
+	signingKey := []byte("AWS4" + rs.AwsSecurityCredentials.SecretAccessKey)
+	for _, signingInput := range []string{
+		dateStamp, rs.RegionName, serviceName, awsRequestType, stringToSign,
+	} {
+		signingKey, err = getHmacSha256(signingKey, []byte(signingInput))
+		if err != nil {
+			return "", err
+		}
+	}
+
+	return fmt.Sprintf("%s Credential=%s/%s, SignedHeaders=%s, Signature=%s", awsAlgorithm, rs.AwsSecurityCredentials.AccessKeyID, credentialScope, canonicalHeaderColumns, hex.EncodeToString(signingKey)), nil
+}
+
+func getSha256(input []byte) (string, error) {
+	hash := sha256.New()
+	if _, err := hash.Write(input); err != nil {
+		return "", err
+	}
+	return hex.EncodeToString(hash.Sum(nil)), nil
+}
+
+func getHmacSha256(key, input []byte) ([]byte, error) {
+	hash := hmac.New(sha256.New, key)
+	if _, err := hash.Write(input); err != nil {
+		return nil, err
+	}
+	return hash.Sum(nil), nil
+}
+
+func cloneRequest(r *http.Request) *http.Request {
+	r2 := new(http.Request)
+	*r2 = *r
+	if r.Header != nil {
+		r2.Header = make(http.Header, len(r.Header))
+
+		// Find total number of values.
+		headerCount := 0
+		for _, headerValues := range r.Header {
+			headerCount += len(headerValues)
+		}
+		copiedHeaders := make([]string, headerCount) // shared backing array for headers' values
+
+		for headerKey, headerValues := range r.Header {
+			headerCount = copy(copiedHeaders, headerValues)
+			r2.Header[headerKey] = copiedHeaders[:headerCount:headerCount]
+			copiedHeaders = copiedHeaders[headerCount:]
+		}
+	}
+	return r2
+}
+
+func canonicalPath(req *http.Request) string {
+	result := req.URL.EscapedPath()
+	if result == "" {
+		return "/"
+	}
+	return path.Clean(result)
+}
+
+func canonicalQuery(req *http.Request) string {
+	queryValues := req.URL.Query()
+	for queryKey := range queryValues {
+		sort.Strings(queryValues[queryKey])
+	}
+	return queryValues.Encode()
+}
+
+func canonicalHeaders(req *http.Request) (string, string) {
+	// Header keys need to be sorted alphabetically.
+	var headers []string
+	lowerCaseHeaders := make(http.Header)
+	for k, v := range req.Header {
+		k := strings.ToLower(k)
+		if _, ok := lowerCaseHeaders[k]; ok {
+			// include additional values
+			lowerCaseHeaders[k] = append(lowerCaseHeaders[k], v...)
+		} else {
+			headers = append(headers, k)
+			lowerCaseHeaders[k] = v
+		}
+	}
+	sort.Strings(headers)
+
+	var fullHeaders bytes.Buffer
+	for _, header := range headers {
+		headerValue := strings.Join(lowerCaseHeaders[header], ",")
+		fullHeaders.WriteString(header)
+		fullHeaders.WriteRune(':')
+		fullHeaders.WriteString(headerValue)
+		fullHeaders.WriteRune('\n')
+	}
+
+	return strings.Join(headers, ";"), fullHeaders.String()
+}
+
+func requestDataHash(req *http.Request) (string, error) {
+	var requestData []byte
+	if req.Body != nil {
+		requestBody, err := req.GetBody()
+		if err != nil {
+			return "", err
+		}
+		defer requestBody.Close()
+
+		requestData, err = internal.ReadAll(requestBody)
+		if err != nil {
+			return "", err
+		}
+	}
+
+	return getSha256(requestData)
+}
+
+func requestHost(req *http.Request) string {
+	if req.Host != "" {
+		return req.Host
+	}
+	return req.URL.Host
+}
+
+func canonicalRequest(req *http.Request, canonicalHeaderColumns, canonicalHeaderData string) (string, error) {
+	dataHash, err := requestDataHash(req)
+	if err != nil {
+		return "", err
+	}
+	return fmt.Sprintf("%s\n%s\n%s\n%s\n%s\n%s", req.Method, canonicalPath(req), canonicalQuery(req), canonicalHeaderData, canonicalHeaderColumns, dataHash), nil
+}
+
+type awsRequestHeader struct {
+	Key   string `json:"key"`
+	Value string `json:"value"`
+}
+
+type awsRequest struct {
+	URL     string             `json:"url"`
+	Method  string             `json:"method"`
+	Headers []awsRequestHeader `json:"headers"`
+}
+
+// The AWS region can be provided through AWS_REGION or AWS_DEFAULT_REGION. Only one is
+// required.
+func canRetrieveRegionFromEnvironment() bool {
+	return getenv(awsRegionEnvVar) != "" || getenv(awsDefaultRegionEnvVar) != ""
+}
+
+// Check if both AWS_ACCESS_KEY_ID and AWS_SECRET_ACCESS_KEY are available.
+func canRetrieveSecurityCredentialFromEnvironment() bool {
+	return getenv(awsAccessKeyIDEnvVar) != "" && getenv(awsSecretAccessKeyEnvVar) != ""
+}
+
+func (sp *awsSubjectProvider) shouldUseMetadataServer() bool {
+	return sp.securityCredentialsProvider == nil && (!canRetrieveRegionFromEnvironment() || !canRetrieveSecurityCredentialFromEnvironment())
+}

vendor/cloud.google.com/go/auth/credentials/internal/externalaccount/executable_provider.go

@@ -0,0 +1,284 @@
+// Copyright 2023 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package externalaccount
+
+import (
+	"bytes"
+	"context"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"net/http"
+	"os"
+	"os/exec"
+	"regexp"
+	"strings"
+	"time"
+
+	"cloud.google.com/go/auth/internal"
+)
+
+const (
+	executableSupportedMaxVersion = 1
+	executableDefaultTimeout      = 30 * time.Second
+	executableSource              = "response"
+	executableProviderType        = "executable"
+	outputFileSource              = "output file"
+
+	allowExecutablesEnvVar = "GOOGLE_EXTERNAL_ACCOUNT_ALLOW_EXECUTABLES"
+
+	jwtTokenType   = "urn:ietf:params:oauth:token-type:jwt"
+	idTokenType    = "urn:ietf:params:oauth:token-type:id_token"
+	saml2TokenType = "urn:ietf:params:oauth:token-type:saml2"
+)
+
+var (
+	serviceAccountImpersonationRE = regexp.MustCompile(`https://iamcredentials..+/v1/projects/-/serviceAccounts/(.*@.*):generateAccessToken`)
+)
+
+type nonCacheableError struct {
+	message string
+}
+
+func (nce nonCacheableError) Error() string {
+	return nce.message
+}
+
+// environment is a contract for testing
+type environment interface {
+	existingEnv() []string
+	getenv(string) string
+	run(ctx context.Context, command string, env []string) ([]byte, error)
+	now() time.Time
+}
+
+type runtimeEnvironment struct{}
+
+func (r runtimeEnvironment) existingEnv() []string {
+	return os.Environ()
+}
+func (r runtimeEnvironment) getenv(key string) string {
+	return os.Getenv(key)
+}
+func (r runtimeEnvironment) now() time.Time {
+	return time.Now().UTC()
+}
+
+func (r runtimeEnvironment) run(ctx context.Context, command string, env []string) ([]byte, error) {
+	splitCommand := strings.Fields(command)
+	cmd := exec.CommandContext(ctx, splitCommand[0], splitCommand[1:]...)
+	cmd.Env = env
+
+	var stdout, stderr bytes.Buffer
+	cmd.Stdout = &stdout
+	cmd.Stderr = &stderr
+
+	if err := cmd.Run(); err != nil {
+		if ctx.Err() == context.DeadlineExceeded {
+			return nil, context.DeadlineExceeded
+		}
+		if exitError, ok := err.(*exec.ExitError); ok {
+			return nil, exitCodeError(exitError)
+		}
+		return nil, executableError(err)
+	}
+
+	bytesStdout := bytes.TrimSpace(stdout.Bytes())
+	if len(bytesStdout) > 0 {
+		return bytesStdout, nil
+	}
+	return bytes.TrimSpace(stderr.Bytes()), nil
+}
+
+type executableSubjectProvider struct {
+	Command    string
+	Timeout    time.Duration
+	OutputFile string
+	client     *http.Client
+	opts       *Options
+	env        environment
+}
+
+type executableResponse struct {
+	Version        int    `json:"version,omitempty"`
+	Success        *bool  `json:"success,omitempty"`
+	TokenType      string `json:"token_type,omitempty"`
+	ExpirationTime int64  `json:"expiration_time,omitempty"`
+	IDToken        string `json:"id_token,omitempty"`
+	SamlResponse   string `json:"saml_response,omitempty"`
+	Code           string `json:"code,omitempty"`
+	Message        string `json:"message,omitempty"`
+}
+
+func (sp *executableSubjectProvider) parseSubjectTokenFromSource(response []byte, source string, now int64) (string, error) {
+	var result executableResponse
+	if err := json.Unmarshal(response, &result); err != nil {
+		return "", jsonParsingError(source, string(response))
+	}
+	// Validate
+	if result.Version == 0 {
+		return "", missingFieldError(source, "version")
+	}
+	if result.Success == nil {
+		return "", missingFieldError(source, "success")
+	}
+	if !*result.Success {
+		if result.Code == "" || result.Message == "" {
+			return "", malformedFailureError()
+		}
+		return "", userDefinedError(result.Code, result.Message)
+	}
+	if result.Version > executableSupportedMaxVersion || result.Version < 0 {
+		return "", unsupportedVersionError(source, result.Version)
+	}
+	if result.ExpirationTime == 0 && sp.OutputFile != "" {
+		return "", missingFieldError(source, "expiration_time")
+	}
+	if result.TokenType == "" {
+		return "", missingFieldError(source, "token_type")
+	}
+	if result.ExpirationTime != 0 && result.ExpirationTime < now {
+		return "", tokenExpiredError()
+	}
+
+	switch result.TokenType {
+	case jwtTokenType, idTokenType:
+		if result.IDToken == "" {
+			return "", missingFieldError(source, "id_token")
+		}
+		return result.IDToken, nil
+	case saml2TokenType:
+		if result.SamlResponse == "" {
+			return "", missingFieldError(source, "saml_response")
+		}
+		return result.SamlResponse, nil
+	default:
+		return "", tokenTypeError(source)
+	}
+}
+
+func (sp *executableSubjectProvider) subjectToken(ctx context.Context) (string, error) {
+	if token, err := sp.getTokenFromOutputFile(); token != "" || err != nil {
+		return token, err
+	}
+	return sp.getTokenFromExecutableCommand(ctx)
+}
+
+func (sp *executableSubjectProvider) providerType() string {
+	return executableProviderType
+}
+
+func (sp *executableSubjectProvider) getTokenFromOutputFile() (token string, err error) {
+	if sp.OutputFile == "" {
+		// This ExecutableCredentialSource doesn't use an OutputFile.
+		return "", nil
+	}
+
+	file, err := os.Open(sp.OutputFile)
+	if err != nil {
+		// No OutputFile found. Hasn't been created yet, so skip it.
+		return "", nil
+	}
+	defer file.Close()
+
+	data, err := internal.ReadAll(file)
+	if err != nil || len(data) == 0 {
+		// Cachefile exists, but no data found. Get new credential.
+		return "", nil
+	}
+
+	token, err = sp.parseSubjectTokenFromSource(data, outputFileSource, sp.env.now().Unix())
+	if err != nil {
+		if _, ok := err.(nonCacheableError); ok {
+			// If the cached token is expired we need a new token,
+			// and if the cache contains a failure, we need to try again.
+			return "", nil
+		}
+
+		// There was an error in the cached token, and the developer should be aware of it.
+		return "", err
+	}
+	// Token parsing succeeded.  Use found token.
+	return token, nil
+}
+
+func (sp *executableSubjectProvider) executableEnvironment() []string {
+	result := sp.env.existingEnv()
+	result = append(result, fmt.Sprintf("GOOGLE_EXTERNAL_ACCOUNT_AUDIENCE=%v", sp.opts.Audience))
+	result = append(result, fmt.Sprintf("GOOGLE_EXTERNAL_ACCOUNT_TOKEN_TYPE=%v", sp.opts.SubjectTokenType))
+	result = append(result, "GOOGLE_EXTERNAL_ACCOUNT_INTERACTIVE=0")
+	if sp.opts.ServiceAccountImpersonationURL != "" {
+		matches := serviceAccountImpersonationRE.FindStringSubmatch(sp.opts.ServiceAccountImpersonationURL)
+		if matches != nil {
+			result = append(result, fmt.Sprintf("GOOGLE_EXTERNAL_ACCOUNT_IMPERSONATED_EMAIL=%v", matches[1]))
+		}
+	}
+	if sp.OutputFile != "" {
+		result = append(result, fmt.Sprintf("GOOGLE_EXTERNAL_ACCOUNT_OUTPUT_FILE=%v", sp.OutputFile))
+	}
+	return result
+}
+
+func (sp *executableSubjectProvider) getTokenFromExecutableCommand(ctx context.Context) (string, error) {
+	// For security reasons, we need our consumers to set this environment variable to allow executables to be run.
+	if sp.env.getenv(allowExecutablesEnvVar) != "1" {
+		return "", errors.New("credentials: executables need to be explicitly allowed (set GOOGLE_EXTERNAL_ACCOUNT_ALLOW_EXECUTABLES to '1') to run")
+	}
+
+	ctx, cancel := context.WithDeadline(ctx, sp.env.now().Add(sp.Timeout))
+	defer cancel()
+
+	output, err := sp.env.run(ctx, sp.Command, sp.executableEnvironment())
+	if err != nil {
+		return "", err
+	}
+	return sp.parseSubjectTokenFromSource(output, executableSource, sp.env.now().Unix())
+}
+
+func missingFieldError(source, field string) error {
+	return fmt.Errorf("credentials: %q missing %q field", source, field)
+}
+
+func jsonParsingError(source, data string) error {
+	return fmt.Errorf("credentials: unable to parse %q: %v", source, data)
+}
+
+func malformedFailureError() error {
+	return nonCacheableError{"credentials: response must include `error` and `message` fields when unsuccessful"}
+}
+
+func userDefinedError(code, message string) error {
+	return nonCacheableError{fmt.Sprintf("credentials: response contains unsuccessful response: (%v) %v", code, message)}
+}
+
+func unsupportedVersionError(source string, version int) error {
+	return fmt.Errorf("credentials: %v contains unsupported version: %v", source, version)
+}
+
+func tokenExpiredError() error {
+	return nonCacheableError{"credentials: the token returned by the executable is expired"}
+}
+
+func tokenTypeError(source string) error {
+	return fmt.Errorf("credentials: %v contains unsupported token type", source)
+}
+
+func exitCodeError(err *exec.ExitError) error {
+	return fmt.Errorf("credentials: executable command failed with exit code %v: %w", err.ExitCode(), err)
+}
+
+func executableError(err error) error {
+	return fmt.Errorf("credentials: executable command failed: %w", err)
+}

vendor/cloud.google.com/go/auth/credentials/internal/externalaccount/externalaccount.go

@@ -0,0 +1,431 @@
+// Copyright 2023 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package externalaccount
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"log/slog"
+	"net/http"
+	"regexp"
+	"strconv"
+	"strings"
+	"time"
+
+	"cloud.google.com/go/auth"
+	"cloud.google.com/go/auth/credentials/internal/impersonate"
+	"cloud.google.com/go/auth/credentials/internal/stsexchange"
+	"cloud.google.com/go/auth/internal/credsfile"
+	"github.com/googleapis/gax-go/v2/internallog"
+)
+
+const (
+	timeoutMinimum = 5 * time.Second
+	timeoutMaximum = 120 * time.Second
+
+	universeDomainPlaceholder = "UNIVERSE_DOMAIN"
+	defaultTokenURL           = "https://sts.UNIVERSE_DOMAIN/v1/token"
+	defaultUniverseDomain     = "googleapis.com"
+)
+
+var (
+	// Now aliases time.Now for testing
+	Now = func() time.Time {
+		return time.Now().UTC()
+	}
+	validWorkforceAudiencePattern *regexp.Regexp = regexp.MustCompile(`//iam\.googleapis\.com/locations/[^/]+/workforcePools/`)
+)
+
+// Options stores the configuration for fetching tokens with external credentials.
+type Options struct {
+	// Audience is the Secure Token Service (STS) audience which contains the resource name for the workload
+	// identity pool or the workforce pool and the provider identifier in that pool.
+	Audience string
+	// SubjectTokenType is the STS token type based on the Oauth2.0 token exchange spec
+	// e.g. `urn:ietf:params:oauth:token-type:jwt`.
+	SubjectTokenType string
+	// TokenURL is the STS token exchange endpoint.
+	TokenURL string
+	// TokenInfoURL is the token_info endpoint used to retrieve the account related information (
+	// user attributes like account identifier, eg. email, username, uid, etc). This is
+	// needed for gCloud session account identification.
+	TokenInfoURL string
+	// ServiceAccountImpersonationURL is the URL for the service account impersonation request. This is only
+	// required for workload identity pools when APIs to be accessed have not integrated with UberMint.
+	ServiceAccountImpersonationURL string
+	// ServiceAccountImpersonationLifetimeSeconds is the number of seconds the service account impersonation
+	// token will be valid for.
+	ServiceAccountImpersonationLifetimeSeconds int
+	// ClientSecret is currently only required if token_info endpoint also
+	// needs to be called with the generated GCP access token. When provided, STS will be
+	// called with additional basic authentication using client_id as username and client_secret as password.
+	ClientSecret string
+	// ClientID is only required in conjunction with ClientSecret, as described above.
+	ClientID string
+	// CredentialSource contains the necessary information to retrieve the token itself, as well
+	// as some environmental information.
+	CredentialSource *credsfile.CredentialSource
+	// QuotaProjectID is injected by gCloud. If the value is non-empty, the Auth libraries
+	// will set the x-goog-user-project which overrides the project associated with the credentials.
+	QuotaProjectID string
+	// Scopes contains the desired scopes for the returned access token.
+	Scopes []string
+	// WorkforcePoolUserProject should be set when it is a workforce pool and
+	// not a workload identity pool. The underlying principal must still have
+	// serviceusage.services.use IAM permission to use the project for
+	// billing/quota. Optional.
+	WorkforcePoolUserProject string
+	// UniverseDomain is the default service domain for a given Cloud universe.
+	// This value will be used in the default STS token URL. The default value
+	// is "googleapis.com". It will not be used if TokenURL is set. Optional.
+	UniverseDomain string
+	// SubjectTokenProvider is an optional token provider for OIDC/SAML
+	// credentials. One of SubjectTokenProvider, AWSSecurityCredentialProvider
+	// or CredentialSource must be provided. Optional.
+	SubjectTokenProvider SubjectTokenProvider
+	// AwsSecurityCredentialsProvider is an AWS Security Credential provider
+	// for AWS credentials. One of SubjectTokenProvider,
+	// AWSSecurityCredentialProvider or CredentialSource must be provided. Optional.
+	AwsSecurityCredentialsProvider AwsSecurityCredentialsProvider
+	// Client for token request.
+	Client *http.Client
+	// IsDefaultClient marks whether the client passed in is a default client that can be overriden.
+	// This is important for X509 credentials which should create a new client if the default was used
+	// but should respect a client explicitly passed in by the user.
+	IsDefaultClient bool
+	// Logger is used for debug logging. If provided, logging will be enabled
+	// at the loggers configured level. By default logging is disabled unless
+	// enabled by setting GOOGLE_SDK_GO_LOGGING_LEVEL in which case a default
+	// logger will be used. Optional.
+	Logger *slog.Logger
+}
+
+// SubjectTokenProvider can be used to supply a subject token to exchange for a
+// GCP access token.
+type SubjectTokenProvider interface {
+	// SubjectToken should return a valid subject token or an error.
+	// The external account token provider does not cache the returned subject
+	// token, so caching logic should be implemented in the provider to prevent
+	// multiple requests for the same subject token.
+	SubjectToken(ctx context.Context, opts *RequestOptions) (string, error)
+}
+
+// RequestOptions contains information about the requested subject token or AWS
+// security credentials from the Google external account credential.
+type RequestOptions struct {
+	// Audience is the requested audience for the external account credential.
+	Audience string
+	// Subject token type is the requested subject token type for the external
+	// account credential. Expected values include:
+	// “urn:ietf:params:oauth:token-type:jwt”
+	// “urn:ietf:params:oauth:token-type:id-token”
+	// “urn:ietf:params:oauth:token-type:saml2”
+	// “urn:ietf:params:aws:token-type:aws4_request”
+	SubjectTokenType string
+}
+
+// AwsSecurityCredentialsProvider can be used to supply AwsSecurityCredentials
+// and an AWS Region to exchange for a GCP access token.
+type AwsSecurityCredentialsProvider interface {
+	// AwsRegion should return the AWS region or an error.
+	AwsRegion(ctx context.Context, opts *RequestOptions) (string, error)
+	// GetAwsSecurityCredentials should return a valid set of
+	// AwsSecurityCredentials or an error. The external account token provider
+	// does not cache the returned security credentials, so caching logic should
+	// be implemented in the provider to prevent multiple requests for the
+	// same security credentials.
+	AwsSecurityCredentials(ctx context.Context, opts *RequestOptions) (*AwsSecurityCredentials, error)
+}
+
+// AwsSecurityCredentials models AWS security credentials.
+type AwsSecurityCredentials struct {
+	// AccessKeyId is the AWS Access Key ID - Required.
+	AccessKeyID string `json:"AccessKeyID"`
+	// SecretAccessKey is the AWS Secret Access Key - Required.
+	SecretAccessKey string `json:"SecretAccessKey"`
+	// SessionToken is the AWS Session token. This should be provided for
+	// temporary AWS security credentials - Optional.
+	SessionToken string `json:"Token"`
+}
+
+func (o *Options) validate() error {
+	if o.Audience == "" {
+		return fmt.Errorf("externalaccount: Audience must be set")
+	}
+	if o.SubjectTokenType == "" {
+		return fmt.Errorf("externalaccount: Subject token type must be set")
+	}
+	if o.WorkforcePoolUserProject != "" {
+		if valid := validWorkforceAudiencePattern.MatchString(o.Audience); !valid {
+			return fmt.Errorf("externalaccount: workforce_pool_user_project should not be set for non-workforce pool credentials")
+		}
+	}
+	count := 0
+	if o.CredentialSource != nil {
+		count++
+	}
+	if o.SubjectTokenProvider != nil {
+		count++
+	}
+	if o.AwsSecurityCredentialsProvider != nil {
+		count++
+	}
+	if count == 0 {
+		return fmt.Errorf("externalaccount: one of CredentialSource, SubjectTokenProvider, or AwsSecurityCredentialsProvider must be set")
+	}
+	if count > 1 {
+		return fmt.Errorf("externalaccount: only one of CredentialSource, SubjectTokenProvider, or AwsSecurityCredentialsProvider must be set")
+	}
+	return nil
+}
+
+// client returns the http client that should be used for the token exchange. If a non-default client
+// is provided, then the client configured in the options will always be returned. If a default client
+// is provided and the options are configured for X509 credentials, a new client will be created.
+func (o *Options) client() (*http.Client, error) {
+	// If a client was provided and no override certificate config location was provided, use the provided client.
+	if o.CredentialSource == nil || o.CredentialSource.Certificate == nil || (!o.IsDefaultClient && o.CredentialSource.Certificate.CertificateConfigLocation == "") {
+		return o.Client, nil
+	}
+
+	// If a new client should be created, validate and use the certificate source to create a new mTLS client.
+	cert := o.CredentialSource.Certificate
+	if !cert.UseDefaultCertificateConfig && cert.CertificateConfigLocation == "" {
+		return nil, errors.New("credentials: \"certificate\" object must either specify a certificate_config_location or use_default_certificate_config should be true")
+	}
+	if cert.UseDefaultCertificateConfig && cert.CertificateConfigLocation != "" {
+		return nil, errors.New("credentials: \"certificate\" object cannot specify both a certificate_config_location and use_default_certificate_config=true")
+	}
+	return createX509Client(cert.CertificateConfigLocation)
+}
+
+// resolveTokenURL sets the default STS token endpoint with the configured
+// universe domain.
+func (o *Options) resolveTokenURL() {
+	if o.TokenURL != "" {
+		return
+	} else if o.UniverseDomain != "" {
+		o.TokenURL = strings.Replace(defaultTokenURL, universeDomainPlaceholder, o.UniverseDomain, 1)
+	} else {
+		o.TokenURL = strings.Replace(defaultTokenURL, universeDomainPlaceholder, defaultUniverseDomain, 1)
+	}
+}
+
+// NewTokenProvider returns a [cloud.google.com/go/auth.TokenProvider]
+// configured with the provided options.
+func NewTokenProvider(opts *Options) (auth.TokenProvider, error) {
+	if err := opts.validate(); err != nil {
+		return nil, err
+	}
+	opts.resolveTokenURL()
+	logger := internallog.New(opts.Logger)
+	stp, err := newSubjectTokenProvider(opts)
+	if err != nil {
+		return nil, err
+	}
+
+	client, err := opts.client()
+	if err != nil {
+		return nil, err
+	}
+
+	tp := &tokenProvider{
+		client: client,
+		opts:   opts,
+		stp:    stp,
+		logger: logger,
+	}
+
+	if opts.ServiceAccountImpersonationURL == "" {
+		return auth.NewCachedTokenProvider(tp, nil), nil
+	}
+
+	scopes := make([]string, len(opts.Scopes))
+	copy(scopes, opts.Scopes)
+	// needed for impersonation
+	tp.opts.Scopes = []string{"https://www.googleapis.com/auth/cloud-platform"}
+	imp, err := impersonate.NewTokenProvider(&impersonate.Options{
+		Client:               client,
+		URL:                  opts.ServiceAccountImpersonationURL,
+		Scopes:               scopes,
+		Tp:                   auth.NewCachedTokenProvider(tp, nil),
+		TokenLifetimeSeconds: opts.ServiceAccountImpersonationLifetimeSeconds,
+		Logger:               logger,
+	})
+	if err != nil {
+		return nil, err
+	}
+	return auth.NewCachedTokenProvider(imp, nil), nil
+}
+
+type subjectTokenProvider interface {
+	subjectToken(ctx context.Context) (string, error)
+	providerType() string
+}
+
+// tokenProvider is the provider that handles external credentials. It is used to retrieve Tokens.
+type tokenProvider struct {
+	client *http.Client
+	logger *slog.Logger
+	opts   *Options
+	stp    subjectTokenProvider
+}
+
+func (tp *tokenProvider) Token(ctx context.Context) (*auth.Token, error) {
+	subjectToken, err := tp.stp.subjectToken(ctx)
+	if err != nil {
+		return nil, err
+	}
+
+	stsRequest := &stsexchange.TokenRequest{
+		GrantType:          stsexchange.GrantType,
+		Audience:           tp.opts.Audience,
+		Scope:              tp.opts.Scopes,
+		RequestedTokenType: stsexchange.TokenType,
+		SubjectToken:       subjectToken,
+		SubjectTokenType:   tp.opts.SubjectTokenType,
+	}
+	header := make(http.Header)
+	header.Set("Content-Type", "application/x-www-form-urlencoded")
+	header.Add("x-goog-api-client", getGoogHeaderValue(tp.opts, tp.stp))
+	clientAuth := stsexchange.ClientAuthentication{
+		AuthStyle:    auth.StyleInHeader,
+		ClientID:     tp.opts.ClientID,
+		ClientSecret: tp.opts.ClientSecret,
+	}
+	var options map[string]interface{}
+	// Do not pass workforce_pool_user_project when client authentication is used.
+	// The client ID is sufficient for determining the user project.
+	if tp.opts.WorkforcePoolUserProject != "" && tp.opts.ClientID == "" {
+		options = map[string]interface{}{
+			"userProject": tp.opts.WorkforcePoolUserProject,
+		}
+	}
+	stsResp, err := stsexchange.ExchangeToken(ctx, &stsexchange.Options{
+		Client:         tp.client,
+		Endpoint:       tp.opts.TokenURL,
+		Request:        stsRequest,
+		Authentication: clientAuth,
+		Headers:        header,
+		ExtraOpts:      options,
+		Logger:         tp.logger,
+	})
+	if err != nil {
+		return nil, err
+	}
+
+	tok := &auth.Token{
+		Value: stsResp.AccessToken,
+		Type:  stsResp.TokenType,
+	}
+	// The RFC8693 doesn't define the explicit 0 of "expires_in" field behavior.
+	if stsResp.ExpiresIn <= 0 {
+		return nil, fmt.Errorf("credentials: got invalid expiry from security token service")
+	}
+	tok.Expiry = Now().Add(time.Duration(stsResp.ExpiresIn) * time.Second)
+	return tok, nil
+}
+
+// newSubjectTokenProvider determines the type of credsfile.CredentialSource needed to create a
+// subjectTokenProvider
+func newSubjectTokenProvider(o *Options) (subjectTokenProvider, error) {
+	logger := internallog.New(o.Logger)
+	reqOpts := &RequestOptions{Audience: o.Audience, SubjectTokenType: o.SubjectTokenType}
+	if o.AwsSecurityCredentialsProvider != nil {
+		return &awsSubjectProvider{
+			securityCredentialsProvider: o.AwsSecurityCredentialsProvider,
+			TargetResource:              o.Audience,
+			reqOpts:                     reqOpts,
+			logger:                      logger,
+		}, nil
+	} else if o.SubjectTokenProvider != nil {
+		return &programmaticProvider{stp: o.SubjectTokenProvider, opts: reqOpts}, nil
+	} else if len(o.CredentialSource.EnvironmentID) > 3 && o.CredentialSource.EnvironmentID[:3] == "aws" {
+		if awsVersion, err := strconv.Atoi(o.CredentialSource.EnvironmentID[3:]); err == nil {
+			if awsVersion != 1 {
+				return nil, fmt.Errorf("credentials: aws version '%d' is not supported in the current build", awsVersion)
+			}
+
+			awsProvider := &awsSubjectProvider{
+				EnvironmentID:               o.CredentialSource.EnvironmentID,
+				RegionURL:                   o.CredentialSource.RegionURL,
+				RegionalCredVerificationURL: o.CredentialSource.RegionalCredVerificationURL,
+				CredVerificationURL:         o.CredentialSource.URL,
+				TargetResource:              o.Audience,
+				Client:                      o.Client,
+				logger:                      logger,
+			}
+			if o.CredentialSource.IMDSv2SessionTokenURL != "" {
+				awsProvider.IMDSv2SessionTokenURL = o.CredentialSource.IMDSv2SessionTokenURL
+			}
+
+			return awsProvider, nil
+		}
+	} else if o.CredentialSource.File != "" {
+		return &fileSubjectProvider{File: o.CredentialSource.File, Format: o.CredentialSource.Format}, nil
+	} else if o.CredentialSource.URL != "" {
+		return &urlSubjectProvider{
+			URL:     o.CredentialSource.URL,
+			Headers: o.CredentialSource.Headers,
+			Format:  o.CredentialSource.Format,
+			Client:  o.Client,
+			Logger:  logger,
+		}, nil
+	} else if o.CredentialSource.Executable != nil {
+		ec := o.CredentialSource.Executable
+		if ec.Command == "" {
+			return nil, errors.New("credentials: missing `command` field — executable command must be provided")
+		}
+
+		execProvider := &executableSubjectProvider{}
+		execProvider.Command = ec.Command
+		if ec.TimeoutMillis == 0 {
+			execProvider.Timeout = executableDefaultTimeout
+		} else {
+			execProvider.Timeout = time.Duration(ec.TimeoutMillis) * time.Millisecond
+			if execProvider.Timeout < timeoutMinimum || execProvider.Timeout > timeoutMaximum {
+				return nil, fmt.Errorf("credentials: invalid `timeout_millis` field — executable timeout must be between %v and %v seconds", timeoutMinimum.Seconds(), timeoutMaximum.Seconds())
+			}
+		}
+		execProvider.OutputFile = ec.OutputFile
+		execProvider.client = o.Client
+		execProvider.opts = o
+		execProvider.env = runtimeEnvironment{}
+		return execProvider, nil
+	} else if o.CredentialSource.Certificate != nil {
+		cert := o.CredentialSource.Certificate
+		if !cert.UseDefaultCertificateConfig && cert.CertificateConfigLocation == "" {
+			return nil, errors.New("credentials: \"certificate\" object must either specify a certificate_config_location or use_default_certificate_config should be true")
+		}
+		if cert.UseDefaultCertificateConfig && cert.CertificateConfigLocation != "" {
+			return nil, errors.New("credentials: \"certificate\" object cannot specify both a certificate_config_location and use_default_certificate_config=true")
+		}
+		return &x509Provider{
+			TrustChainPath: o.CredentialSource.Certificate.TrustChainPath,
+			ConfigFilePath: o.CredentialSource.Certificate.CertificateConfigLocation,
+		}, nil
+	}
+	return nil, errors.New("credentials: unable to parse credential source")
+}
+
+func getGoogHeaderValue(conf *Options, p subjectTokenProvider) string {
+	return fmt.Sprintf("gl-go/%s auth/%s google-byoid-sdk source/%s sa-impersonation/%t config-lifetime/%t",
+		goVersion(),
+		"unknown",
+		p.providerType(),
+		conf.ServiceAccountImpersonationURL != "",
+		conf.ServiceAccountImpersonationLifetimeSeconds != 0)
+}

vendor/cloud.google.com/go/auth/credentials/internal/externalaccount/file_provider.go

@@ -0,0 +1,78 @@
+// Copyright 2023 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package externalaccount
+
+import (
+	"bytes"
+	"context"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"os"
+
+	"cloud.google.com/go/auth/internal"
+	"cloud.google.com/go/auth/internal/credsfile"
+)
+
+const (
+	fileProviderType = "file"
+)
+
+type fileSubjectProvider struct {
+	File   string
+	Format *credsfile.Format
+}
+
+func (sp *fileSubjectProvider) subjectToken(context.Context) (string, error) {
+	tokenFile, err := os.Open(sp.File)
+	if err != nil {
+		return "", fmt.Errorf("credentials: failed to open credential file %q: %w", sp.File, err)
+	}
+	defer tokenFile.Close()
+	tokenBytes, err := internal.ReadAll(tokenFile)
+	if err != nil {
+		return "", fmt.Errorf("credentials: failed to read credential file: %w", err)
+	}
+	tokenBytes = bytes.TrimSpace(tokenBytes)
+
+	if sp.Format == nil {
+		return string(tokenBytes), nil
+	}
+	switch sp.Format.Type {
+	case fileTypeJSON:
+		jsonData := make(map[string]interface{})
+		err = json.Unmarshal(tokenBytes, &jsonData)
+		if err != nil {
+			return "", fmt.Errorf("credentials: failed to unmarshal subject token file: %w", err)
+		}
+		val, ok := jsonData[sp.Format.SubjectTokenFieldName]
+		if !ok {
+			return "", errors.New("credentials: provided subject_token_field_name not found in credentials")
+		}
+		token, ok := val.(string)
+		if !ok {
+			return "", errors.New("credentials: improperly formatted subject token")
+		}
+		return token, nil
+	case fileTypeText:
+		return string(tokenBytes), nil
+	default:
+		return "", errors.New("credentials: invalid credential_source file format type: " + sp.Format.Type)
+	}
+}
+
+func (sp *fileSubjectProvider) providerType() string {
+	return fileProviderType
+}

vendor/cloud.google.com/go/auth/credentials/internal/externalaccount/info.go

@@ -0,0 +1,74 @@
+// Copyright 2023 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package externalaccount
+
+import (
+	"runtime"
+	"strings"
+	"unicode"
+)
+
+var (
+	// version is a package internal global variable for testing purposes.
+	version = runtime.Version
+)
+
+// versionUnknown is only used when the runtime version cannot be determined.
+const versionUnknown = "UNKNOWN"
+
+// goVersion returns a Go runtime version derived from the runtime environment
+// that is modified to be suitable for reporting in a header, meaning it has no
+// whitespace. If it is unable to determine the Go runtime version, it returns
+// versionUnknown.
+func goVersion() string {
+	const develPrefix = "devel +"
+
+	s := version()
+	if strings.HasPrefix(s, develPrefix) {
+		s = s[len(develPrefix):]
+		if p := strings.IndexFunc(s, unicode.IsSpace); p >= 0 {
+			s = s[:p]
+		}
+		return s
+	} else if p := strings.IndexFunc(s, unicode.IsSpace); p >= 0 {
+		s = s[:p]
+	}
+
+	notSemverRune := func(r rune) bool {
+		return !strings.ContainsRune("0123456789.", r)
+	}
+
+	if strings.HasPrefix(s, "go1") {
+		s = s[2:]
+		var prerelease string
+		if p := strings.IndexFunc(s, notSemverRune); p >= 0 {
+			s, prerelease = s[:p], s[p:]
+		}
+		if strings.HasSuffix(s, ".") {
+			s += "0"
+		} else if strings.Count(s, ".") < 2 {
+			s += ".0"
+		}
+		if prerelease != "" {
+			// Some release candidates already have a dash in them.
+			if !strings.HasPrefix(prerelease, "-") {
+				prerelease = "-" + prerelease
+			}
+			s += prerelease
+		}
+		return s
+	}
+	return versionUnknown
+}

vendor/cloud.google.com/go/auth/credentials/internal/externalaccount/programmatic_provider.go

@@ -0,0 +1,30 @@
+// Copyright 2024 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package externalaccount
+
+import "context"
+
+type programmaticProvider struct {
+	opts *RequestOptions
+	stp  SubjectTokenProvider
+}
+
+func (pp *programmaticProvider) providerType() string {
+	return programmaticProviderType
+}
+
+func (pp *programmaticProvider) subjectToken(ctx context.Context) (string, error) {
+	return pp.stp.SubjectToken(ctx, pp.opts)
+}

vendor/cloud.google.com/go/auth/credentials/internal/externalaccount/url_provider.go

@@ -0,0 +1,93 @@
+// Copyright 2023 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package externalaccount
+
+import (
+	"context"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"log/slog"
+	"net/http"
+
+	"cloud.google.com/go/auth/internal"
+	"cloud.google.com/go/auth/internal/credsfile"
+	"github.com/googleapis/gax-go/v2/internallog"
+)
+
+const (
+	fileTypeText             = "text"
+	fileTypeJSON             = "json"
+	urlProviderType          = "url"
+	programmaticProviderType = "programmatic"
+	x509ProviderType         = "x509"
+)
+
+type urlSubjectProvider struct {
+	URL     string
+	Headers map[string]string
+	Format  *credsfile.Format
+	Client  *http.Client
+	Logger  *slog.Logger
+}
+
+func (sp *urlSubjectProvider) subjectToken(ctx context.Context) (string, error) {
+	req, err := http.NewRequestWithContext(ctx, "GET", sp.URL, nil)
+	if err != nil {
+		return "", fmt.Errorf("credentials: HTTP request for URL-sourced credential failed: %w", err)
+	}
+
+	for key, val := range sp.Headers {
+		req.Header.Add(key, val)
+	}
+	sp.Logger.DebugContext(ctx, "url subject token request", "request", internallog.HTTPRequest(req, nil))
+	resp, body, err := internal.DoRequest(sp.Client, req)
+	if err != nil {
+		return "", fmt.Errorf("credentials: invalid response when retrieving subject token: %w", err)
+	}
+	sp.Logger.DebugContext(ctx, "url subject token response", "response", internallog.HTTPResponse(resp, body))
+	if c := resp.StatusCode; c < http.StatusOK || c >= http.StatusMultipleChoices {
+		return "", fmt.Errorf("credentials: status code %d: %s", c, body)
+	}
+
+	if sp.Format == nil {
+		return string(body), nil
+	}
+	switch sp.Format.Type {
+	case "json":
+		jsonData := make(map[string]interface{})
+		err = json.Unmarshal(body, &jsonData)
+		if err != nil {
+			return "", fmt.Errorf("credentials: failed to unmarshal subject token file: %w", err)
+		}
+		val, ok := jsonData[sp.Format.SubjectTokenFieldName]
+		if !ok {
+			return "", errors.New("credentials: provided subject_token_field_name not found in credentials")
+		}
+		token, ok := val.(string)
+		if !ok {
+			return "", errors.New("credentials: improperly formatted subject token")
+		}
+		return token, nil
+	case fileTypeText:
+		return string(body), nil
+	default:
+		return "", errors.New("credentials: invalid credential_source file format type: " + sp.Format.Type)
+	}
+}
+
+func (sp *urlSubjectProvider) providerType() string {
+	return urlProviderType
+}

vendor/cloud.google.com/go/auth/credentials/internal/externalaccount/x509_provider.go

@@ -0,0 +1,220 @@
+// Copyright 2024 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package externalaccount
+
+import (
+	"context"
+	"crypto/tls"
+	"crypto/x509"
+	"encoding/base64"
+	"encoding/json"
+	"encoding/pem"
+	"errors"
+	"fmt"
+	"io/fs"
+	"net/http"
+	"os"
+	"strings"
+	"time"
+
+	"cloud.google.com/go/auth/internal/transport/cert"
+)
+
+// x509Provider implements the subjectTokenProvider type for x509 workload
+// identity credentials. This provider retrieves and formats a JSON array
+// containing the leaf certificate and trust chain (if provided) as
+// base64-encoded strings. This JSON array serves as the subject token for
+// mTLS authentication.
+type x509Provider struct {
+	// TrustChainPath is the path to the file containing the trust chain certificates.
+	// The file should contain one or more PEM-encoded certificates.
+	TrustChainPath string
+	// ConfigFilePath is the path to the configuration file containing the path
+	// to the leaf certificate file.
+	ConfigFilePath string
+}
+
+const pemCertificateHeader = "-----BEGIN CERTIFICATE-----"
+
+func (xp *x509Provider) providerType() string {
+	return x509ProviderType
+}
+
+// loadLeafCertificate loads and parses the leaf certificate from the specified
+// configuration file. It retrieves the certificate path from the config file,
+// reads the certificate file, and parses the certificate data.
+func loadLeafCertificate(configFilePath string) (*x509.Certificate, error) {
+	// Get the path to the certificate file from the configuration file.
+	path, err := cert.GetCertificatePath(configFilePath)
+	if err != nil {
+		return nil, fmt.Errorf("failed to get certificate path from config file: %w", err)
+	}
+	leafCertBytes, err := os.ReadFile(path)
+	if err != nil {
+		return nil, fmt.Errorf("failed to read leaf certificate file: %w", err)
+	}
+	// Parse the certificate bytes.
+	return parseCertificate(leafCertBytes)
+}
+
+// encodeCert encodes a x509.Certificate to a base64 string.
+func encodeCert(cert *x509.Certificate) string {
+	// cert.Raw contains the raw DER-encoded certificate. Encode the raw certificate bytes to base64.
+	return base64.StdEncoding.EncodeToString(cert.Raw)
+}
+
+// parseCertificate parses a PEM-encoded certificate from the given byte slice.
+func parseCertificate(certData []byte) (*x509.Certificate, error) {
+	if len(certData) == 0 {
+		return nil, errors.New("invalid certificate data: empty input")
+	}
+	// Decode the PEM-encoded data.
+	block, _ := pem.Decode(certData)
+	if block == nil {
+		return nil, errors.New("invalid PEM-encoded certificate data: no PEM block found")
+	}
+	if block.Type != "CERTIFICATE" {
+		return nil, fmt.Errorf("invalid PEM-encoded certificate data: expected CERTIFICATE block type, got %s", block.Type)
+	}
+	// Parse the DER-encoded certificate.
+	certificate, err := x509.ParseCertificate(block.Bytes)
+	if err != nil {
+		return nil, fmt.Errorf("failed to parse certificate: %w", err)
+	}
+	return certificate, nil
+}
+
+// readTrustChain reads a file of PEM-encoded X.509 certificates and returns a slice of parsed certificates.
+// It splits the file content into PEM certificate blocks and parses each one.
+func readTrustChain(trustChainPath string) ([]*x509.Certificate, error) {
+	certificateTrustChain := []*x509.Certificate{}
+
+	// If no trust chain path is provided, return an empty slice.
+	if trustChainPath == "" {
+		return certificateTrustChain, nil
+	}
+
+	// Read the trust chain file.
+	trustChainData, err := os.ReadFile(trustChainPath)
+	if err != nil {
+		if errors.Is(err, fs.ErrNotExist) {
+			return nil, fmt.Errorf("trust chain file not found: %w", err)
+		}
+		return nil, fmt.Errorf("failed to read trust chain file: %w", err)
+	}
+
+	// Split the file content into PEM certificate blocks.
+	certBlocks := strings.Split(string(trustChainData), pemCertificateHeader)
+
+	// Iterate over each certificate block.
+	for _, certBlock := range certBlocks {
+		// Trim whitespace from the block.
+		certBlock = strings.TrimSpace(certBlock)
+
+		if certBlock != "" {
+			// Add the PEM header to the block.
+			certData := pemCertificateHeader + "\n" + certBlock
+
+			// Parse the certificate data.
+			cert, err := parseCertificate([]byte(certData))
+			if err != nil {
+				return nil, fmt.Errorf("error parsing certificate from trust chain file: %w", err)
+			}
+
+			// Append the certificate to the trust chain.
+			certificateTrustChain = append(certificateTrustChain, cert)
+		}
+	}
+
+	return certificateTrustChain, nil
+}
+
+// subjectToken retrieves the X.509 subject token. It loads the leaf
+// certificate and, if a trust chain path is configured, the trust chain
+// certificates. It then constructs a JSON array containing the base64-encoded
+// leaf certificate and each base64-encoded certificate in the trust chain.
+// The leaf certificate must be at the top of the trust chain file. This JSON
+// array is used as the subject token for mTLS authentication.
+func (xp *x509Provider) subjectToken(context.Context) (string, error) {
+	// Load the leaf certificate.
+	leafCert, err := loadLeafCertificate(xp.ConfigFilePath)
+	if err != nil {
+		return "", fmt.Errorf("failed to load leaf certificate: %w", err)
+	}
+
+	// Read the trust chain.
+	trustChain, err := readTrustChain(xp.TrustChainPath)
+	if err != nil {
+		return "", fmt.Errorf("failed to read trust chain: %w", err)
+	}
+
+	// Initialize the certificate chain with the leaf certificate.
+	certChain := []string{encodeCert(leafCert)}
+
+	// If there is a trust chain, add certificates to the certificate chain.
+	if len(trustChain) > 0 {
+		firstCert := encodeCert(trustChain[0])
+
+		// If the first certificate in the trust chain is not the same as the leaf certificate, add it to the chain.
+		if firstCert != certChain[0] {
+			certChain = append(certChain, firstCert)
+		}
+
+		// Iterate over the remaining certificates in the trust chain.
+		for i := 1; i < len(trustChain); i++ {
+			encoded := encodeCert(trustChain[i])
+
+			// Return an error if the current certificate is the same as the leaf certificate.
+			if encoded == certChain[0] {
+				return "", errors.New("the leaf certificate must be at the top of the trust chain file")
+			}
+
+			// Add the current certificate to the chain.
+			certChain = append(certChain, encoded)
+		}
+	}
+
+	// Convert the certificate chain to a JSON array of base64-encoded strings.
+	jsonChain, err := json.Marshal(certChain)
+	if err != nil {
+		return "", fmt.Errorf("failed to format certificate data: %w", err)
+	}
+
+	// Return the JSON-formatted certificate chain.
+	return string(jsonChain), nil
+
+}
+
+// createX509Client creates a new client that is configured with mTLS, using the
+// certificate configuration specified in the credential source.
+func createX509Client(certificateConfigLocation string) (*http.Client, error) {
+	certProvider, err := cert.NewWorkloadX509CertProvider(certificateConfigLocation)
+	if err != nil {
+		return nil, err
+	}
+	trans := http.DefaultTransport.(*http.Transport).Clone()
+
+	trans.TLSClientConfig = &tls.Config{
+		GetClientCertificate: certProvider,
+	}
+
+	// Create a client with default settings plus the X509 workload cert and key.
+	client := &http.Client{
+		Transport: trans,
+		Timeout:   30 * time.Second,
+	}
+
+	return client, nil
+}

vendor/cloud.google.com/go/auth/credentials/internal/externalaccountuser/externalaccountuser.go

@@ -0,0 +1,115 @@
+// Copyright 2023 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package externalaccountuser
+
+import (
+	"context"
+	"errors"
+	"log/slog"
+	"net/http"
+	"time"
+
+	"cloud.google.com/go/auth"
+	"cloud.google.com/go/auth/credentials/internal/stsexchange"
+	"cloud.google.com/go/auth/internal"
+	"github.com/googleapis/gax-go/v2/internallog"
+)
+
+// Options stores the configuration for fetching tokens with external authorized
+// user credentials.
+type Options struct {
+	// Audience is the Secure Token Service (STS) audience which contains the
+	// resource name for the workforce pool and the provider identifier in that
+	// pool.
+	Audience string
+	// RefreshToken is the OAuth 2.0 refresh token.
+	RefreshToken string
+	// TokenURL is the STS token exchange endpoint for refresh.
+	TokenURL string
+	// TokenInfoURL is the STS endpoint URL for token introspection. Optional.
+	TokenInfoURL string
+	// ClientID is only required in conjunction with ClientSecret, as described
+	// below.
+	ClientID string
+	// ClientSecret is currently only required if token_info endpoint also needs
+	// to be called with the generated a cloud access token. When provided, STS
+	// will be called with additional basic authentication using client_id as
+	// username and client_secret as password.
+	ClientSecret string
+	// Scopes contains the desired scopes for the returned access token.
+	Scopes []string
+
+	// Client for token request.
+	Client *http.Client
+	// Logger for logging.
+	Logger *slog.Logger
+}
+
+func (c *Options) validate() bool {
+	return c.ClientID != "" && c.ClientSecret != "" && c.RefreshToken != "" && c.TokenURL != ""
+}
+
+// NewTokenProvider returns a [cloud.google.com/go/auth.TokenProvider]
+// configured with the provided options.
+func NewTokenProvider(opts *Options) (auth.TokenProvider, error) {
+	if !opts.validate() {
+		return nil, errors.New("credentials: invalid external_account_authorized_user configuration")
+	}
+
+	tp := &tokenProvider{
+		o: opts,
+	}
+	return auth.NewCachedTokenProvider(tp, nil), nil
+}
+
+type tokenProvider struct {
+	o *Options
+}
+
+func (tp *tokenProvider) Token(ctx context.Context) (*auth.Token, error) {
+	opts := tp.o
+
+	clientAuth := stsexchange.ClientAuthentication{
+		AuthStyle:    auth.StyleInHeader,
+		ClientID:     opts.ClientID,
+		ClientSecret: opts.ClientSecret,
+	}
+	headers := make(http.Header)
+	headers.Set("Content-Type", "application/x-www-form-urlencoded")
+	stsResponse, err := stsexchange.RefreshAccessToken(ctx, &stsexchange.Options{
+		Client:         opts.Client,
+		Endpoint:       opts.TokenURL,
+		RefreshToken:   opts.RefreshToken,
+		Authentication: clientAuth,
+		Headers:        headers,
+		Logger:         internallog.New(tp.o.Logger),
+	})
+	if err != nil {
+		return nil, err
+	}
+	if stsResponse.ExpiresIn < 0 {
+		return nil, errors.New("credentials: invalid expiry from security token service")
+	}
+
+	// guarded by the wrapping with CachedTokenProvider
+	if stsResponse.RefreshToken != "" {
+		opts.RefreshToken = stsResponse.RefreshToken
+	}
+	return &auth.Token{
+		Value:  stsResponse.AccessToken,
+		Expiry: time.Now().UTC().Add(time.Duration(stsResponse.ExpiresIn) * time.Second),
+		Type:   internal.TokenTypeBearer,
+	}, nil
+}

vendor/cloud.google.com/go/auth/credentials/internal/gdch/gdch.go

@@ -0,0 +1,191 @@
+// Copyright 2023 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package gdch
+
+import (
+	"context"
+	"crypto"
+	"crypto/tls"
+	"crypto/x509"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"log/slog"
+	"net/http"
+	"net/url"
+	"os"
+	"strings"
+	"time"
+
+	"cloud.google.com/go/auth"
+	"cloud.google.com/go/auth/internal"
+	"cloud.google.com/go/auth/internal/credsfile"
+	"cloud.google.com/go/auth/internal/jwt"
+	"github.com/googleapis/gax-go/v2/internallog"
+)
+
+const (
+	// GrantType is the grant type for the token request.
+	GrantType        = "urn:ietf:params:oauth:token-type:token-exchange"
+	requestTokenType = "urn:ietf:params:oauth:token-type:access_token"
+	subjectTokenType = "urn:k8s:params:oauth:token-type:serviceaccount"
+)
+
+var (
+	gdchSupportFormatVersions map[string]bool = map[string]bool{
+		"1": true,
+	}
+)
+
+// Options for [NewTokenProvider].
+type Options struct {
+	STSAudience string
+	Client      *http.Client
+	Logger      *slog.Logger
+}
+
+// NewTokenProvider returns a [cloud.google.com/go/auth.TokenProvider] from a
+// GDCH cred file.
+func NewTokenProvider(f *credsfile.GDCHServiceAccountFile, o *Options) (auth.TokenProvider, error) {
+	if !gdchSupportFormatVersions[f.FormatVersion] {
+		return nil, fmt.Errorf("credentials: unsupported gdch_service_account format %q", f.FormatVersion)
+	}
+	if o.STSAudience == "" {
+		return nil, errors.New("credentials: STSAudience must be set for the GDCH auth flows")
+	}
+	signer, err := internal.ParseKey([]byte(f.PrivateKey))
+	if err != nil {
+		return nil, err
+	}
+	certPool, err := loadCertPool(f.CertPath)
+	if err != nil {
+		return nil, err
+	}
+
+	tp := gdchProvider{
+		serviceIdentity: fmt.Sprintf("system:serviceaccount:%s:%s", f.Project, f.Name),
+		tokenURL:        f.TokenURL,
+		aud:             o.STSAudience,
+		signer:          signer,
+		pkID:            f.PrivateKeyID,
+		certPool:        certPool,
+		client:          o.Client,
+		logger:          internallog.New(o.Logger),
+	}
+	return tp, nil
+}
+
+func loadCertPool(path string) (*x509.CertPool, error) {
+	pool := x509.NewCertPool()
+	pem, err := os.ReadFile(path)
+	if err != nil {
+		return nil, fmt.Errorf("credentials: failed to read certificate: %w", err)
+	}
+	pool.AppendCertsFromPEM(pem)
+	return pool, nil
+}
+
+type gdchProvider struct {
+	serviceIdentity string
+	tokenURL        string
+	aud             string
+	signer          crypto.Signer
+	pkID            string
+	certPool        *x509.CertPool
+
+	client *http.Client
+	logger *slog.Logger
+}
+
+func (g gdchProvider) Token(ctx context.Context) (*auth.Token, error) {
+	addCertToTransport(g.client, g.certPool)
+	iat := time.Now()
+	exp := iat.Add(time.Hour)
+	claims := jwt.Claims{
+		Iss: g.serviceIdentity,
+		Sub: g.serviceIdentity,
+		Aud: g.tokenURL,
+		Iat: iat.Unix(),
+		Exp: exp.Unix(),
+	}
+	h := jwt.Header{
+		Algorithm: jwt.HeaderAlgRSA256,
+		Type:      jwt.HeaderType,
+		KeyID:     string(g.pkID),
+	}
+	payload, err := jwt.EncodeJWS(&h, &claims, g.signer)
+	if err != nil {
+		return nil, err
+	}
+	v := url.Values{}
+	v.Set("grant_type", GrantType)
+	v.Set("audience", g.aud)
+	v.Set("requested_token_type", requestTokenType)
+	v.Set("subject_token", payload)
+	v.Set("subject_token_type", subjectTokenType)
+
+	req, err := http.NewRequestWithContext(ctx, "POST", g.tokenURL, strings.NewReader(v.Encode()))
+	if err != nil {
+		return nil, err
+	}
+	req.Header.Set("Content-Type", "application/x-www-form-urlencoded")
+	g.logger.DebugContext(ctx, "gdch token request", "request", internallog.HTTPRequest(req, []byte(v.Encode())))
+	resp, body, err := internal.DoRequest(g.client, req)
+	if err != nil {
+		return nil, fmt.Errorf("credentials: cannot fetch token: %w", err)
+	}
+	g.logger.DebugContext(ctx, "gdch token response", "response", internallog.HTTPResponse(resp, body))
+	if c := resp.StatusCode; c < http.StatusOK || c > http.StatusMultipleChoices {
+		return nil, &auth.Error{
+			Response: resp,
+			Body:     body,
+		}
+	}
+
+	var tokenRes struct {
+		AccessToken string `json:"access_token"`
+		TokenType   string `json:"token_type"`
+		ExpiresIn   int64  `json:"expires_in"` // relative seconds from now
+	}
+	if err := json.Unmarshal(body, &tokenRes); err != nil {
+		return nil, fmt.Errorf("credentials: cannot fetch token: %w", err)
+	}
+	token := &auth.Token{
+		Value: tokenRes.AccessToken,
+		Type:  tokenRes.TokenType,
+	}
+	raw := make(map[string]interface{})
+	json.Unmarshal(body, &raw) // no error checks for optional fields
+	token.Metadata = raw
+
+	if secs := tokenRes.ExpiresIn; secs > 0 {
+		token.Expiry = time.Now().Add(time.Duration(secs) * time.Second)
+	}
+	return token, nil
+}
+
+// addCertToTransport makes a best effort attempt at adding in the cert info to
+// the client. It tries to keep all configured transport settings if the
+// underlying transport is an http.Transport. Or else it overwrites the
+// transport with defaults adding in the certs.
+func addCertToTransport(hc *http.Client, certPool *x509.CertPool) {
+	trans, ok := hc.Transport.(*http.Transport)
+	if !ok {
+		trans = http.DefaultTransport.(*http.Transport).Clone()
+	}
+	trans.TLSClientConfig = &tls.Config{
+		RootCAs: certPool,
+	}
+}

vendor/cloud.google.com/go/auth/credentials/internal/impersonate/idtoken.go

@@ -0,0 +1,105 @@
+// Copyright 2025 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package impersonate
+
+import (
+	"bytes"
+	"context"
+	"encoding/json"
+	"fmt"
+	"log/slog"
+	"net/http"
+	"strings"
+	"time"
+
+	"cloud.google.com/go/auth"
+	"cloud.google.com/go/auth/internal"
+	"github.com/googleapis/gax-go/v2/internallog"
+)
+
+var (
+	universeDomainPlaceholder            = "UNIVERSE_DOMAIN"
+	iamCredentialsUniverseDomainEndpoint = "https://iamcredentials.UNIVERSE_DOMAIN"
+)
+
+// IDTokenIAMOptions provides configuration for [IDTokenIAMOptions.Token].
+type IDTokenIAMOptions struct {
+	// Client is required.
+	Client *http.Client
+	// Logger is required.
+	Logger              *slog.Logger
+	UniverseDomain      auth.CredentialsPropertyProvider
+	ServiceAccountEmail string
+	GenerateIDTokenRequest
+}
+
+// GenerateIDTokenRequest holds the request to the IAM generateIdToken RPC.
+type GenerateIDTokenRequest struct {
+	Audience     string `json:"audience"`
+	IncludeEmail bool   `json:"includeEmail"`
+	// Delegates are the ordered, fully-qualified resource name for service
+	// accounts in a delegation chain. Each service account must be granted
+	// roles/iam.serviceAccountTokenCreator on the next service account in the
+	// chain. The delegates must have the following format:
+	// projects/-/serviceAccounts/{ACCOUNT_EMAIL_OR_UNIQUEID}. The - wildcard
+	// character is required; replacing it with a project ID is invalid.
+	// Optional.
+	Delegates []string `json:"delegates,omitempty"`
+}
+
+// GenerateIDTokenResponse holds the response from the IAM generateIdToken RPC.
+type GenerateIDTokenResponse struct {
+	Token string `json:"token"`
+}
+
+// Token call IAM generateIdToken with the configuration provided in [IDTokenIAMOptions].
+func (o IDTokenIAMOptions) Token(ctx context.Context) (*auth.Token, error) {
+	universeDomain, err := o.UniverseDomain.GetProperty(ctx)
+	if err != nil {
+		return nil, err
+	}
+	endpoint := strings.Replace(iamCredentialsUniverseDomainEndpoint, universeDomainPlaceholder, universeDomain, 1)
+	url := fmt.Sprintf("%s/v1/%s:generateIdToken", endpoint, internal.FormatIAMServiceAccountResource(o.ServiceAccountEmail))
+
+	bodyBytes, err := json.Marshal(o.GenerateIDTokenRequest)
+	if err != nil {
+		return nil, fmt.Errorf("impersonate: unable to marshal request: %w", err)
+	}
+
+	req, err := http.NewRequestWithContext(ctx, "POST", url, bytes.NewReader(bodyBytes))
+	if err != nil {
+		return nil, fmt.Errorf("impersonate: unable to create request: %w", err)
+	}
+	req.Header.Set("Content-Type", "application/json")
+	o.Logger.DebugContext(ctx, "impersonated idtoken request", "request", internallog.HTTPRequest(req, bodyBytes))
+	resp, body, err := internal.DoRequest(o.Client, req)
+	if err != nil {
+		return nil, fmt.Errorf("impersonate: unable to generate ID token: %w", err)
+	}
+	o.Logger.DebugContext(ctx, "impersonated idtoken response", "response", internallog.HTTPResponse(resp, body))
+	if c := resp.StatusCode; c < 200 || c > 299 {
+		return nil, fmt.Errorf("impersonate: status code %d: %s", c, body)
+	}
+
+	var tokenResp GenerateIDTokenResponse
+	if err := json.Unmarshal(body, &tokenResp); err != nil {
+		return nil, fmt.Errorf("impersonate: unable to parse response: %w", err)
+	}
+	return &auth.Token{
+		Value: tokenResp.Token,
+		// Generated ID tokens are good for one hour.
+		Expiry: time.Now().Add(1 * time.Hour),
+	}, nil
+}

vendor/cloud.google.com/go/auth/credentials/internal/impersonate/impersonate.go

@@ -0,0 +1,168 @@
+// Copyright 2023 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package impersonate
+
+import (
+	"bytes"
+	"context"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"log/slog"
+	"net/http"
+	"regexp"
+	"time"
+
+	"cloud.google.com/go/auth"
+	"cloud.google.com/go/auth/internal"
+	"cloud.google.com/go/auth/internal/transport/headers"
+	"github.com/googleapis/gax-go/v2/internallog"
+)
+
+const (
+	defaultTokenLifetime = "3600s"
+	authHeaderKey        = "Authorization"
+)
+
+var serviceAccountEmailRegex = regexp.MustCompile(`serviceAccounts/(.+?):generateAccessToken`)
+
+// generateAccesstokenReq is used for service account impersonation
+type generateAccessTokenReq struct {
+	Delegates []string `json:"delegates,omitempty"`
+	Lifetime  string   `json:"lifetime,omitempty"`
+	Scope     []string `json:"scope,omitempty"`
+}
+
+type impersonateTokenResponse struct {
+	AccessToken string `json:"accessToken"`
+	ExpireTime  string `json:"expireTime"`
+}
+
+// NewTokenProvider uses a source credential, stored in Ts, to request an access token to the provided URL.
+// Scopes can be defined when the access token is requested.
+func NewTokenProvider(opts *Options) (auth.TokenProvider, error) {
+	if err := opts.validate(); err != nil {
+		return nil, err
+	}
+	return opts, nil
+}
+
+// Options for [NewTokenProvider].
+type Options struct {
+	// Tp is the source credential used to generate a token on the
+	// impersonated service account. Required.
+	Tp auth.TokenProvider
+
+	// URL is the endpoint to call to generate a token
+	// on behalf of the service account. Required.
+	URL string
+	// Scopes that the impersonated credential should have. Required.
+	Scopes []string
+	// Delegates are the service account email addresses in a delegation chain.
+	// Each service account must be granted roles/iam.serviceAccountTokenCreator
+	// on the next service account in the chain. Optional.
+	Delegates []string
+	// TokenLifetimeSeconds is the number of seconds the impersonation token will
+	// be valid for. Defaults to 1 hour if unset. Optional.
+	TokenLifetimeSeconds int
+	// Client configures the underlying client used to make network requests
+	// when fetching tokens. Required.
+	Client *http.Client
+	// Logger is used for debug logging. If provided, logging will be enabled
+	// at the loggers configured level. By default logging is disabled unless
+	// enabled by setting GOOGLE_SDK_GO_LOGGING_LEVEL in which case a default
+	// logger will be used. Optional.
+	Logger *slog.Logger
+	// UniverseDomain is the default service domain for a given Cloud universe.
+	UniverseDomain string
+}
+
+func (o *Options) validate() error {
+	if o.Tp == nil {
+		return errors.New("credentials: missing required 'source_credentials' field in impersonated credentials")
+	}
+	if o.URL == "" {
+		return errors.New("credentials: missing required 'service_account_impersonation_url' field in impersonated credentials")
+	}
+	return nil
+}
+
+// Token performs the exchange to get a temporary service account token to allow access to GCP.
+func (o *Options) Token(ctx context.Context) (*auth.Token, error) {
+	logger := internallog.New(o.Logger)
+	lifetime := defaultTokenLifetime
+	if o.TokenLifetimeSeconds != 0 {
+		lifetime = fmt.Sprintf("%ds", o.TokenLifetimeSeconds)
+	}
+	reqBody := generateAccessTokenReq{
+		Lifetime:  lifetime,
+		Scope:     o.Scopes,
+		Delegates: o.Delegates,
+	}
+	b, err := json.Marshal(reqBody)
+	if err != nil {
+		return nil, fmt.Errorf("credentials: unable to marshal request: %w", err)
+	}
+	req, err := http.NewRequestWithContext(ctx, "POST", o.URL, bytes.NewReader(b))
+	if err != nil {
+		return nil, fmt.Errorf("credentials: unable to create impersonation request: %w", err)
+	}
+	req.Header.Set("Content-Type", "application/json")
+	sourceToken, err := o.Tp.Token(ctx)
+	if err != nil {
+		return nil, err
+	}
+	headers.SetAuthHeader(sourceToken, req)
+	logger.DebugContext(ctx, "impersonated token request", "request", internallog.HTTPRequest(req, b))
+	resp, body, err := internal.DoRequest(o.Client, req)
+	if err != nil {
+		return nil, fmt.Errorf("credentials: unable to generate access token: %w", err)
+	}
+	logger.DebugContext(ctx, "impersonated token response", "response", internallog.HTTPResponse(resp, body))
+	if c := resp.StatusCode; c < http.StatusOK || c >= http.StatusMultipleChoices {
+		return nil, fmt.Errorf("credentials: status code %d: %s", c, body)
+	}
+
+	var accessTokenResp impersonateTokenResponse
+	if err := json.Unmarshal(body, &accessTokenResp); err != nil {
+		return nil, fmt.Errorf("credentials: unable to parse response: %w", err)
+	}
+	expiry, err := time.Parse(time.RFC3339, accessTokenResp.ExpireTime)
+	if err != nil {
+		return nil, fmt.Errorf("credentials: unable to parse expiry: %w", err)
+	}
+	token := &auth.Token{
+		Value:  accessTokenResp.AccessToken,
+		Expiry: expiry,
+		Type:   internal.TokenTypeBearer,
+	}
+	return token, nil
+}
+
+// ExtractServiceAccountEmail extracts the service account email from the impersonation URL.
+// The impersonation URL is expected to be in the format:
+// https://iamcredentials.googleapis.com/v1/projects/-/serviceAccounts/{SERVICE_ACCOUNT_EMAIL}:generateAccessToken
+// or
+// https://iamcredentials.googleapis.com/v1/projects/{PROJECT_ID}/serviceAccounts/{SERVICE_ACCOUNT_EMAIL}:generateAccessToken
+// Returns an error if the email cannot be extracted.
+func ExtractServiceAccountEmail(impersonationURL string) (string, error) {
+	matches := serviceAccountEmailRegex.FindStringSubmatch(impersonationURL)
+
+	if len(matches) < 2 {
+		return "", fmt.Errorf("credentials: invalid impersonation URL format: %s", impersonationURL)
+	}
+
+	return matches[1], nil
+}

vendor/cloud.google.com/go/auth/credentials/internal/stsexchange/sts_exchange.go

@@ -0,0 +1,167 @@
+// Copyright 2023 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package stsexchange
+
+import (
+	"context"
+	"encoding/base64"
+	"encoding/json"
+	"fmt"
+	"log/slog"
+	"net/http"
+	"net/url"
+	"strconv"
+	"strings"
+
+	"cloud.google.com/go/auth"
+	"cloud.google.com/go/auth/internal"
+	"github.com/googleapis/gax-go/v2/internallog"
+)
+
+const (
+	// GrantType for a sts exchange.
+	GrantType = "urn:ietf:params:oauth:grant-type:token-exchange"
+	// TokenType for a sts exchange.
+	TokenType = "urn:ietf:params:oauth:token-type:access_token"
+
+	jwtTokenType = "urn:ietf:params:oauth:token-type:jwt"
+)
+
+// Options stores the configuration for making an sts exchange request.
+type Options struct {
+	Client         *http.Client
+	Logger         *slog.Logger
+	Endpoint       string
+	Request        *TokenRequest
+	Authentication ClientAuthentication
+	Headers        http.Header
+	// ExtraOpts are optional fields marshalled into the `options` field of the
+	// request body.
+	ExtraOpts    map[string]interface{}
+	RefreshToken string
+}
+
+// RefreshAccessToken performs the token exchange using a refresh token flow.
+func RefreshAccessToken(ctx context.Context, opts *Options) (*TokenResponse, error) {
+	data := url.Values{}
+	data.Set("grant_type", "refresh_token")
+	data.Set("refresh_token", opts.RefreshToken)
+	return doRequest(ctx, opts, data)
+}
+
+// ExchangeToken performs an oauth2 token exchange with the provided endpoint.
+func ExchangeToken(ctx context.Context, opts *Options) (*TokenResponse, error) {
+	data := url.Values{}
+	data.Set("audience", opts.Request.Audience)
+	data.Set("grant_type", GrantType)
+	data.Set("requested_token_type", TokenType)
+	data.Set("subject_token_type", opts.Request.SubjectTokenType)
+	data.Set("subject_token", opts.Request.SubjectToken)
+	data.Set("scope", strings.Join(opts.Request.Scope, " "))
+	if opts.ExtraOpts != nil {
+		opts, err := json.Marshal(opts.ExtraOpts)
+		if err != nil {
+			return nil, fmt.Errorf("credentials: failed to marshal additional options: %w", err)
+		}
+		data.Set("options", string(opts))
+	}
+	return doRequest(ctx, opts, data)
+}
+
+func doRequest(ctx context.Context, opts *Options, data url.Values) (*TokenResponse, error) {
+	opts.Authentication.InjectAuthentication(data, opts.Headers)
+	encodedData := data.Encode()
+	logger := internallog.New(opts.Logger)
+
+	req, err := http.NewRequestWithContext(ctx, "POST", opts.Endpoint, strings.NewReader(encodedData))
+	if err != nil {
+		return nil, fmt.Errorf("credentials: failed to properly build http request: %w", err)
+
+	}
+	for key, list := range opts.Headers {
+		for _, val := range list {
+			req.Header.Add(key, val)
+		}
+	}
+	req.Header.Set("Content-Length", strconv.Itoa(len(encodedData)))
+
+	logger.DebugContext(ctx, "sts token request", "request", internallog.HTTPRequest(req, []byte(encodedData)))
+	resp, body, err := internal.DoRequest(opts.Client, req)
+	if err != nil {
+		return nil, fmt.Errorf("credentials: invalid response from Secure Token Server: %w", err)
+	}
+	logger.DebugContext(ctx, "sts token response", "response", internallog.HTTPResponse(resp, body))
+	if c := resp.StatusCode; c < http.StatusOK || c > http.StatusMultipleChoices {
+		return nil, fmt.Errorf("credentials: status code %d: %s", c, body)
+	}
+	var stsResp TokenResponse
+	if err := json.Unmarshal(body, &stsResp); err != nil {
+		return nil, fmt.Errorf("credentials: failed to unmarshal response body from Secure Token Server: %w", err)
+	}
+
+	return &stsResp, nil
+}
+
+// TokenRequest contains fields necessary to make an oauth2 token
+// exchange.
+type TokenRequest struct {
+	ActingParty struct {
+		ActorToken     string
+		ActorTokenType string
+	}
+	GrantType          string
+	Resource           string
+	Audience           string
+	Scope              []string
+	RequestedTokenType string
+	SubjectToken       string
+	SubjectTokenType   string
+}
+
+// TokenResponse is used to decode the remote server response during
+// an oauth2 token exchange.
+type TokenResponse struct {
+	AccessToken     string `json:"access_token"`
+	IssuedTokenType string `json:"issued_token_type"`
+	TokenType       string `json:"token_type"`
+	ExpiresIn       int    `json:"expires_in"`
+	Scope           string `json:"scope"`
+	RefreshToken    string `json:"refresh_token"`
+}
+
+// ClientAuthentication represents an OAuth client ID and secret and the
+// mechanism for passing these credentials as stated in rfc6749#2.3.1.
+type ClientAuthentication struct {
+	AuthStyle    auth.Style
+	ClientID     string
+	ClientSecret string
+}
+
+// InjectAuthentication is used to add authentication to a Secure Token Service
+// exchange request.  It modifies either the passed url.Values or http.Header
+// depending on the desired authentication format.
+func (c *ClientAuthentication) InjectAuthentication(values url.Values, headers http.Header) {
+	if c.ClientID == "" || c.ClientSecret == "" || values == nil || headers == nil {
+		return
+	}
+	switch c.AuthStyle {
+	case auth.StyleInHeader:
+		plainHeader := c.ClientID + ":" + c.ClientSecret
+		headers.Set("Authorization", "Basic "+base64.StdEncoding.EncodeToString([]byte(plainHeader)))
+	default:
+		values.Set("client_id", c.ClientID)
+		values.Set("client_secret", c.ClientSecret)
+	}
+}

vendor/cloud.google.com/go/auth/credentials/selfsignedjwt.go

@@ -0,0 +1,89 @@
+// Copyright 2023 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package credentials
+
+import (
+	"context"
+	"crypto"
+	"errors"
+	"fmt"
+	"log/slog"
+	"strings"
+	"time"
+
+	"cloud.google.com/go/auth"
+	"cloud.google.com/go/auth/internal"
+	"cloud.google.com/go/auth/internal/credsfile"
+	"cloud.google.com/go/auth/internal/jwt"
+)
+
+var (
+	// for testing
+	now func() time.Time = time.Now
+)
+
+// configureSelfSignedJWT uses the private key in the service account to create
+// a JWT without making a network call.
+func configureSelfSignedJWT(f *credsfile.ServiceAccountFile, opts *DetectOptions) (auth.TokenProvider, error) {
+	if len(opts.scopes()) == 0 && opts.Audience == "" {
+		return nil, errors.New("credentials: both scopes and audience are empty")
+	}
+	signer, err := internal.ParseKey([]byte(f.PrivateKey))
+	if err != nil {
+		return nil, fmt.Errorf("credentials: could not parse key: %w", err)
+	}
+	return &selfSignedTokenProvider{
+		email:    f.ClientEmail,
+		audience: opts.Audience,
+		scopes:   opts.scopes(),
+		signer:   signer,
+		pkID:     f.PrivateKeyID,
+		logger:   opts.logger(),
+	}, nil
+}
+
+type selfSignedTokenProvider struct {
+	email    string
+	audience string
+	scopes   []string
+	signer   crypto.Signer
+	pkID     string
+	logger   *slog.Logger
+}
+
+func (tp *selfSignedTokenProvider) Token(context.Context) (*auth.Token, error) {
+	iat := now()
+	exp := iat.Add(time.Hour)
+	scope := strings.Join(tp.scopes, " ")
+	c := &jwt.Claims{
+		Iss:   tp.email,
+		Sub:   tp.email,
+		Aud:   tp.audience,
+		Scope: scope,
+		Iat:   iat.Unix(),
+		Exp:   exp.Unix(),
+	}
+	h := &jwt.Header{
+		Algorithm: jwt.HeaderAlgRSA256,
+		Type:      jwt.HeaderType,
+		KeyID:     string(tp.pkID),
+	}
+	tok, err := jwt.EncodeJWS(h, c, tp.signer)
+	if err != nil {
+		return nil, fmt.Errorf("credentials: could not encode JWT: %w", err)
+	}
+	tp.logger.Debug("created self-signed JWT", "token", tok)
+	return &auth.Token{Value: tok, Type: internal.TokenTypeBearer, Expiry: exp}, nil
+}