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// Copyright 2021 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package externalaccount
import (
"context"
"crypto/hmac"
"crypto/sha256"
"encoding/hex"
"encoding/json"
"errors"
"fmt"
"io"
"net/http"
"net/url"
"os"
"path"
"sort"
"strings"
"time"
"golang.org/x/oauth2"
)
// 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"`
}
// awsRequestSigner is a utility class to sign http requests using a AWS V4 signature.
type awsRequestSigner struct {
RegionName string
AwsSecurityCredentials *AwsSecurityCredentials
}
// getenv aliases os.Getenv for testing
var getenv = os.Getenv
const (
defaultRegionalCredentialVerificationUrl = "https://sts.{region}.amazonaws.com?Action=GetCallerIdentity&Version=2011-06-15"
// 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"
// Supported AWS configuration environment variables.
awsAccessKeyId = "AWS_ACCESS_KEY_ID"
awsDefaultRegion = "AWS_DEFAULT_REGION"
awsRegion = "AWS_REGION"
awsSecretAccessKey = "AWS_SECRET_ACCESS_KEY"
awsSessionToken = "AWS_SESSION_TOKEN"
awsTimeFormatLong = "20060102T150405Z"
awsTimeFormatShort = "20060102"
)
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 strings.Builder
for _, header := range headers {
headerValue := strings.Join(lowerCaseHeaders[header], ",")
fullHeaders.WriteString(header)
fullHeaders.WriteByte(':')
fullHeaders.WriteString(headerValue)
fullHeaders.WriteByte('\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 = io.ReadAll(io.LimitReader(requestBody, 1<<20))
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
}
// 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 {
signedRequest := cloneRequest(req)
timestamp := now()
signedRequest.Header.Add("host", requestHost(req))
if rs.AwsSecurityCredentials.SessionToken != "" {
signedRequest.Header.Add(awsSecurityTokenHeader, rs.AwsSecurityCredentials.SessionToken)
}
if signedRequest.Header.Get("date") == "" {
signedRequest.Header.Add(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 := fmt.Sprintf("%s/%s/%s/%s", 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 := fmt.Sprintf("%s\n%s\n%s\n%s", awsAlgorithm, timestamp.Format(awsTimeFormatLong), credentialScope, requestHash)
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
}
type awsCredentialSource struct {
environmentID string
regionURL string
regionalCredVerificationURL string
credVerificationURL string
imdsv2SessionTokenURL string
targetResource string
requestSigner *awsRequestSigner
region string
ctx context.Context
client *http.Client
awsSecurityCredentialsSupplier AwsSecurityCredentialsSupplier
supplierOptions SupplierOptions
}
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"`
}
func (cs awsCredentialSource) doRequest(req *http.Request) (*http.Response, error) {
if cs.client == nil {
cs.client = oauth2.NewClient(cs.ctx, nil)
}
return cs.client.Do(req.WithContext(cs.ctx))
}
func canRetrieveRegionFromEnvironment() bool {
// The AWS region can be provided through AWS_REGION or AWS_DEFAULT_REGION. Only one is
// required.
return getenv(awsRegion) != "" || getenv(awsDefaultRegion) != ""
}
func canRetrieveSecurityCredentialFromEnvironment() bool {
// Check if both AWS_ACCESS_KEY_ID and AWS_SECRET_ACCESS_KEY are available.
return getenv(awsAccessKeyId) != "" && getenv(awsSecretAccessKey) != ""
}
func (cs awsCredentialSource) shouldUseMetadataServer() bool {
return cs.awsSecurityCredentialsSupplier == nil && (!canRetrieveRegionFromEnvironment() || !canRetrieveSecurityCredentialFromEnvironment())
}
func (cs awsCredentialSource) credentialSourceType() string {
if cs.awsSecurityCredentialsSupplier != nil {
return "programmatic"
}
return "aws"
}
func (cs awsCredentialSource) subjectToken() (string, error) {
// Set Defaults
if cs.regionalCredVerificationURL == "" {
cs.regionalCredVerificationURL = defaultRegionalCredentialVerificationUrl
}
if cs.requestSigner == nil {
headers := make(map[string]string)
if cs.shouldUseMetadataServer() {
awsSessionToken, err := cs.getAWSSessionToken()
if err != nil {
return "", err
}
if awsSessionToken != "" {
headers[awsIMDSv2SessionTokenHeader] = awsSessionToken
}
}
awsSecurityCredentials, err := cs.getSecurityCredentials(headers)
if err != nil {
return "", err
}
cs.region, err = cs.getRegion(headers)
if err != nil {
return "", err
}
cs.requestSigner = &awsRequestSigner{
RegionName: cs.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.NewRequest("POST", strings.Replace(cs.regionalCredVerificationURL, "{region}", cs.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 cs.targetResource != "" {
req.Header.Add("x-goog-cloud-target-resource", cs.targetResource)
}
cs.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 (cs *awsCredentialSource) getAWSSessionToken() (string, error) {
if cs.imdsv2SessionTokenURL == "" {
return "", nil
}
req, err := http.NewRequest("PUT", cs.imdsv2SessionTokenURL, nil)
if err != nil {
return "", err
}
req.Header.Add(awsIMDSv2SessionTtlHeader, awsIMDSv2SessionTtl)
resp, err := cs.doRequest(req)
if err != nil {
return "", err
}
defer resp.Body.Close()
respBody, err := io.ReadAll(io.LimitReader(resp.Body, 1<<20))
if err != nil {
return "", err
}
if resp.StatusCode != 200 {
return "", fmt.Errorf("oauth2/google/externalaccount: unable to retrieve AWS session token - %s", string(respBody))
}
return string(respBody), nil
}
func (cs *awsCredentialSource) getRegion(headers map[string]string) (string, error) {
if cs.awsSecurityCredentialsSupplier != nil {
return cs.awsSecurityCredentialsSupplier.AwsRegion(cs.ctx, cs.supplierOptions)
}
if canRetrieveRegionFromEnvironment() {
if envAwsRegion := getenv(awsRegion); envAwsRegion != "" {
cs.region = envAwsRegion
return envAwsRegion, nil
}
return getenv("AWS_DEFAULT_REGION"), nil
}
if cs.regionURL == "" {
return "", errors.New("oauth2/google/externalaccount: unable to determine AWS region")
}
req, err := http.NewRequest("GET", cs.regionURL, nil)
if err != nil {
return "", err
}
for name, value := range headers {
req.Header.Add(name, value)
}
resp, err := cs.doRequest(req)
if err != nil {
return "", err
}
defer resp.Body.Close()
respBody, err := io.ReadAll(io.LimitReader(resp.Body, 1<<20))
if err != nil {
return "", err
}
if resp.StatusCode != 200 {
return "", fmt.Errorf("oauth2/google/externalaccount: unable to retrieve AWS region - %s", string(respBody))
}
// This endpoint will return the region in format: us-east-2b.
// Only the us-east-2 part should be used.
respBodyEnd := 0
if len(respBody) > 1 {
respBodyEnd = len(respBody) - 1
}
return string(respBody[:respBodyEnd]), nil
}
func (cs *awsCredentialSource) getSecurityCredentials(headers map[string]string) (result *AwsSecurityCredentials, err error) {
if cs.awsSecurityCredentialsSupplier != nil {
return cs.awsSecurityCredentialsSupplier.AwsSecurityCredentials(cs.ctx, cs.supplierOptions)
}
if canRetrieveSecurityCredentialFromEnvironment() {
return &AwsSecurityCredentials{
AccessKeyID: getenv(awsAccessKeyId),
SecretAccessKey: getenv(awsSecretAccessKey),
SessionToken: getenv(awsSessionToken),
}, nil
}
roleName, err := cs.getMetadataRoleName(headers)
if err != nil {
return
}
credentials, err := cs.getMetadataSecurityCredentials(roleName, headers)
if err != nil {
return
}
if credentials.AccessKeyID == "" {
return result, errors.New("oauth2/google/externalaccount: missing AccessKeyId credential")
}
if credentials.SecretAccessKey == "" {
return result, errors.New("oauth2/google/externalaccount: missing SecretAccessKey credential")
}
return &credentials, nil
}
func (cs *awsCredentialSource) getMetadataSecurityCredentials(roleName string, headers map[string]string) (AwsSecurityCredentials, error) {
var result AwsSecurityCredentials
req, err := http.NewRequest("GET", fmt.Sprintf("%s/%s", cs.credVerificationURL, roleName), nil)
if err != nil {
return result, err
}
for name, value := range headers {
req.Header.Add(name, value)
}
resp, err := cs.doRequest(req)
if err != nil {
return result, err
}
defer resp.Body.Close()
respBody, err := io.ReadAll(io.LimitReader(resp.Body, 1<<20))
if err != nil {
return result, err
}
if resp.StatusCode != 200 {
return result, fmt.Errorf("oauth2/google/externalaccount: unable to retrieve AWS security credentials - %s", string(respBody))
}
err = json.Unmarshal(respBody, &result)
return result, err
}
func (cs *awsCredentialSource) getMetadataRoleName(headers map[string]string) (string, error) {
if cs.credVerificationURL == "" {
return "", errors.New("oauth2/google/externalaccount: unable to determine the AWS metadata server security credentials endpoint")
}
req, err := http.NewRequest("GET", cs.credVerificationURL, nil)
if err != nil {
return "", err
}
for name, value := range headers {
req.Header.Add(name, value)
}
resp, err := cs.doRequest(req)
if err != nil {
return "", err
}
defer resp.Body.Close()
respBody, err := io.ReadAll(io.LimitReader(resp.Body, 1<<20))
if err != nil {
return "", err
}
if resp.StatusCode != 200 {
return "", fmt.Errorf("oauth2/google/externalaccount: unable to retrieve AWS role name - %s", string(respBody))
}
return string(respBody), nil
}

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// Copyright 2020 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
/*
Package externalaccount provides support for creating workload identity
federation and workforce identity federation token sources that can be
used to access Google Cloud resources from external identity providers.
# Workload Identity Federation
Using workload identity federation, your application can access Google Cloud
resources from Amazon Web Services (AWS), Microsoft Azure or any identity
provider that supports OpenID Connect (OIDC) or SAML 2.0.
Traditionally, applications running outside Google Cloud have used service
account keys to access Google Cloud resources. Using identity federation,
you can allow your workload to impersonate a service account.
This lets you access Google Cloud resources directly, eliminating the
maintenance and security burden associated with service account keys.
Follow the detailed instructions on how to configure Workload Identity Federation
in various platforms:
Amazon Web Services (AWS): https://cloud.google.com/iam/docs/workload-identity-federation-with-other-clouds#aws
Microsoft Azure: https://cloud.google.com/iam/docs/workload-identity-federation-with-other-clouds#azure
OIDC identity provider: https://cloud.google.com/iam/docs/workload-identity-federation-with-other-providers#oidc
SAML 2.0 identity provider: https://cloud.google.com/iam/docs/workload-identity-federation-with-other-providers#saml
For OIDC and SAML providers, the library can retrieve tokens in fours ways:
from a local file location (file-sourced credentials), from a server
(URL-sourced credentials), from a local executable (executable-sourced
credentials), or from a user defined function that returns an OIDC or SAML token.
For file-sourced credentials, a background process needs to be continuously
refreshing the file location with a new OIDC/SAML token prior to expiration.
For tokens with one hour lifetimes, the token needs to be updated in the file
every hour. The token can be stored directly as plain text or in JSON format.
For URL-sourced credentials, a local server needs to host a GET endpoint to
return the OIDC/SAML token. The response can be in plain text or JSON.
Additional required request headers can also be specified.
For executable-sourced credentials, an application needs to be available to
output the OIDC/SAML token and other information in a JSON format.
For more information on how these work (and how to implement
executable-sourced credentials), please check out:
https://cloud.google.com/iam/docs/workload-identity-federation-with-other-providers#create_a_credential_configuration
To use a custom function to supply the token, define a struct that implements the [SubjectTokenSupplier] interface for OIDC/SAML providers,
or one that implements [AwsSecurityCredentialsSupplier] for AWS providers. This can then be used when building a [Config].
The [golang.org/x/oauth2.TokenSource] created from the config using [NewTokenSource] can then be used to access Google
Cloud resources. For instance, you can create a new client from the
[cloud.google.com/go/storage] package and pass in option.WithTokenSource(yourTokenSource))
Note that this library does not perform any validation on the token_url, token_info_url,
or service_account_impersonation_url fields of the credential configuration.
It is not recommended to use a credential configuration that you did not generate with
the gcloud CLI unless you verify that the URL fields point to a googleapis.com domain.
# Workforce Identity Federation
Workforce identity federation lets you use an external identity provider (IdP) to
authenticate and authorize a workforce—a group of users, such as employees, partners,
and contractors—using IAM, so that the users can access Google Cloud services.
Workforce identity federation extends Google Cloud's identity capabilities to support
syncless, attribute-based single sign on.
With workforce identity federation, your workforce can access Google Cloud resources
using an external identity provider (IdP) that supports OpenID Connect (OIDC) or
SAML 2.0 such as Azure Active Directory (Azure AD), Active Directory Federation
Services (AD FS), Okta, and others.
Follow the detailed instructions on how to configure Workload Identity Federation
in various platforms:
Azure AD: https://cloud.google.com/iam/docs/workforce-sign-in-azure-ad
Okta: https://cloud.google.com/iam/docs/workforce-sign-in-okta
OIDC identity provider: https://cloud.google.com/iam/docs/configuring-workforce-identity-federation#oidc
SAML 2.0 identity provider: https://cloud.google.com/iam/docs/configuring-workforce-identity-federation#saml
For workforce identity federation, the library can retrieve tokens in four ways:
from a local file location (file-sourced credentials), from a server
(URL-sourced credentials), from a local executable (executable-sourced
credentials), or from a user supplied function that returns an OIDC or SAML token.
For file-sourced credentials, a background process needs to be continuously
refreshing the file location with a new OIDC/SAML token prior to expiration.
For tokens with one hour lifetimes, the token needs to be updated in the file
every hour. The token can be stored directly as plain text or in JSON format.
For URL-sourced credentials, a local server needs to host a GET endpoint to
return the OIDC/SAML token. The response can be in plain text or JSON.
Additional required request headers can also be specified.
For executable-sourced credentials, an application needs to be available to
output the OIDC/SAML token and other information in a JSON format.
For more information on how these work (and how to implement
executable-sourced credentials), please check out:
https://cloud.google.com/iam/docs/workforce-obtaining-short-lived-credentials#generate_a_configuration_file_for_non-interactive_sign-in
To use a custom function to supply the token, define a struct that implements the [SubjectTokenSupplier] interface for OIDC/SAML providers.
This can then be used when building a [Config].
The [golang.org/x/oauth2.TokenSource] created from the config using [NewTokenSource] can then be used access Google
Cloud resources. For instance, you can create a new client from the
[cloud.google.com/go/storage] package and pass in option.WithTokenSource(yourTokenSource))
# Security considerations
Note that this library does not perform any validation on the token_url, token_info_url,
or service_account_impersonation_url fields of the credential configuration.
It is not recommended to use a credential configuration that you did not generate with
the gcloud CLI unless you verify that the URL fields point to a googleapis.com domain.
*/
package externalaccount
import (
"context"
"fmt"
"net/http"
"regexp"
"strconv"
"strings"
"time"
"golang.org/x/oauth2"
"golang.org/x/oauth2/google/internal/impersonate"
"golang.org/x/oauth2/google/internal/stsexchange"
)
const (
universeDomainPlaceholder = "UNIVERSE_DOMAIN"
defaultTokenURL = "https://sts.UNIVERSE_DOMAIN/v1/token"
defaultUniverseDomain = "googleapis.com"
)
// now aliases time.Now for testing
var now = func() time.Time {
return time.Now().UTC()
}
// Config stores the configuration for fetching tokens with external credentials.
type Config 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. Required.
Audience string
// SubjectTokenType is the STS token type based on the Oauth2.0 token exchange spec.
// 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”
// Required.
SubjectTokenType string
// TokenURL is the STS token exchange endpoint. If not provided, will default to
// https://sts.UNIVERSE_DOMAIN/v1/token, with UNIVERSE_DOMAIN set to the
// default service domain googleapis.com unless UniverseDomain is set.
// Optional.
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. Optional.
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. Optional.
ServiceAccountImpersonationURL string
// ServiceAccountImpersonationLifetimeSeconds is the number of seconds the service account impersonation
// token will be valid for. If not provided, it will default to 3600. Optional.
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 ClientId as username and ClientSecret as password. Optional.
ClientSecret string
// ClientID is only required in conjunction with ClientSecret, as described above. Optional.
ClientID string
// CredentialSource contains the necessary information to retrieve the token itself, as well
// as some environmental information. One of SubjectTokenSupplier, AWSSecurityCredentialSupplier or
// CredentialSource must be provided. Optional.
CredentialSource *CredentialSource
// QuotaProjectID is injected by gCloud. If the value is non-empty, the Auth libraries
// will set the x-goog-user-project header which overrides the project associated with the credentials. Optional.
QuotaProjectID string
// Scopes contains the desired scopes for the returned access token. Optional.
Scopes []string
// WorkforcePoolUserProject is the workforce pool user project number when the credential
// corresponds to 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
// SubjectTokenSupplier is an optional token supplier for OIDC/SAML credentials.
// One of SubjectTokenSupplier, AWSSecurityCredentialSupplier or CredentialSource must be provided. Optional.
SubjectTokenSupplier SubjectTokenSupplier
// AwsSecurityCredentialsSupplier is an AWS Security Credential supplier for AWS credentials.
// One of SubjectTokenSupplier, AWSSecurityCredentialSupplier or CredentialSource must be provided. Optional.
AwsSecurityCredentialsSupplier AwsSecurityCredentialsSupplier
// 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
}
var (
validWorkforceAudiencePattern *regexp.Regexp = regexp.MustCompile(`//iam\.googleapis\.com/locations/[^/]+/workforcePools/`)
)
func validateWorkforceAudience(input string) bool {
return validWorkforceAudiencePattern.MatchString(input)
}
// NewTokenSource Returns an external account TokenSource using the provided external account config.
func NewTokenSource(ctx context.Context, conf Config) (oauth2.TokenSource, error) {
if conf.Audience == "" {
return nil, fmt.Errorf("oauth2/google/externalaccount: Audience must be set")
}
if conf.SubjectTokenType == "" {
return nil, fmt.Errorf("oauth2/google/externalaccount: Subject token type must be set")
}
if conf.WorkforcePoolUserProject != "" {
valid := validateWorkforceAudience(conf.Audience)
if !valid {
return nil, fmt.Errorf("oauth2/google/externalaccount: Workforce pool user project should not be set for non-workforce pool credentials")
}
}
count := 0
if conf.CredentialSource != nil {
count++
}
if conf.SubjectTokenSupplier != nil {
count++
}
if conf.AwsSecurityCredentialsSupplier != nil {
count++
}
if count == 0 {
return nil, fmt.Errorf("oauth2/google/externalaccount: One of CredentialSource, SubjectTokenSupplier, or AwsSecurityCredentialsSupplier must be set")
}
if count > 1 {
return nil, fmt.Errorf("oauth2/google/externalaccount: Only one of CredentialSource, SubjectTokenSupplier, or AwsSecurityCredentialsSupplier must be set")
}
return conf.tokenSource(ctx, "https")
}
// tokenSource is a private function that's directly called by some of the tests,
// because the unit test URLs are mocked, and would otherwise fail the
// validity check.
func (c *Config) tokenSource(ctx context.Context, scheme string) (oauth2.TokenSource, error) {
ts := tokenSource{
ctx: ctx,
conf: c,
}
if c.ServiceAccountImpersonationURL == "" {
return oauth2.ReuseTokenSource(nil, ts), nil
}
scopes := c.Scopes
ts.conf.Scopes = []string{"https://www.googleapis.com/auth/cloud-platform"}
imp := impersonate.ImpersonateTokenSource{
Ctx: ctx,
URL: c.ServiceAccountImpersonationURL,
Scopes: scopes,
Ts: oauth2.ReuseTokenSource(nil, ts),
TokenLifetimeSeconds: c.ServiceAccountImpersonationLifetimeSeconds,
}
return oauth2.ReuseTokenSource(nil, imp), nil
}
// Subject token file types.
const (
fileTypeText = "text"
fileTypeJSON = "json"
)
// Format contains information needed to retrieve a subject token for URL or File sourced credentials.
type Format struct {
// Type should be either "text" or "json". This determines whether the file or URL sourced credentials
// expect a simple text subject token or if the subject token will be contained in a JSON object.
// When not provided "text" type is assumed.
Type string `json:"type"`
// SubjectTokenFieldName is only required for JSON format. This is the field name that the credentials will check
// for the subject token in the file or URL response. This would be "access_token" for azure.
SubjectTokenFieldName string `json:"subject_token_field_name"`
}
// CredentialSource stores the information necessary to retrieve the credentials for the STS exchange.
type CredentialSource struct {
// File is the location for file sourced credentials.
// One field amongst File, URL, Executable, or EnvironmentID should be provided, depending on the kind of credential in question.
//
// 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).
File string `json:"file"`
// Url is the URL to call for URL sourced credentials.
// One field amongst File, URL, Executable, or EnvironmentID should be provided, depending on the kind of credential in question.
//
// 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).
URL string `json:"url"`
// Headers are the headers to attach to the request for URL sourced credentials.
Headers map[string]string `json:"headers"`
// Executable is the configuration object for executable sourced credentials.
// One field amongst File, URL, Executable, or EnvironmentID should be provided, depending on the kind of credential in question.
//
// 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).
Executable *ExecutableConfig `json:"executable"`
// EnvironmentID is the EnvironmentID used for AWS sourced credentials. This should start with "AWS".
// One field amongst File, URL, Executable, or EnvironmentID should be provided, depending on the kind of credential in question.
//
// 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).
EnvironmentID string `json:"environment_id"`
// RegionURL is the metadata URL to retrieve the region from for EC2 AWS credentials.
RegionURL string `json:"region_url"`
// RegionalCredVerificationURL is the AWS regional credential verification URL, will default to
// "https://sts.{region}.amazonaws.com?Action=GetCallerIdentity&Version=2011-06-15" if not provided."
RegionalCredVerificationURL string `json:"regional_cred_verification_url"`
// IMDSv2SessionTokenURL is the URL to retrieve the session token when using IMDSv2 in AWS.
IMDSv2SessionTokenURL string `json:"imdsv2_session_token_url"`
// Format is the format type for the subject token. Used for File and URL sourced credentials. Expected values are "text" or "json".
Format Format `json:"format"`
}
// ExecutableConfig contains information needed for executable sourced credentials.
type ExecutableConfig struct {
// Command is the the full command to run to retrieve the subject token.
// This can include arguments. Must be an absolute path for the program. Required.
Command string `json:"command"`
// TimeoutMillis is the timeout duration, in milliseconds. Defaults to 30000 milliseconds when not provided. Optional.
TimeoutMillis *int `json:"timeout_millis"`
// OutputFile is the absolute path to the output file where the executable will cache the response.
// If specified the auth libraries will first check this location before running the executable. Optional.
OutputFile string `json:"output_file"`
}
// SubjectTokenSupplier can be used to supply a subject token to exchange for a GCP access token.
type SubjectTokenSupplier interface {
// SubjectToken should return a valid subject token or an error.
// The external account token source does not cache the returned subject token, so caching
// logic should be implemented in the supplier to prevent multiple requests for the same subject token.
SubjectToken(ctx context.Context, options SupplierOptions) (string, error)
}
// AWSSecurityCredentialsSupplier can be used to supply AwsSecurityCredentials and an AWS Region to
// exchange for a GCP access token.
type AwsSecurityCredentialsSupplier interface {
// AwsRegion should return the AWS region or an error.
AwsRegion(ctx context.Context, options SupplierOptions) (string, error)
// AwsSecurityCredentials should return a valid set of AwsSecurityCredentials or an error.
// The external account token source does not cache the returned security credentials, so caching
// logic should be implemented in the supplier to prevent multiple requests for the same security credentials.
AwsSecurityCredentials(ctx context.Context, options SupplierOptions) (*AwsSecurityCredentials, error)
}
// SupplierOptions contains information about the requested subject token or AWS security credentials from the
// Google external account credential.
type SupplierOptions 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
}
// tokenURL returns the default STS token endpoint with the configured universe
// domain.
func (c *Config) tokenURL() string {
if c.UniverseDomain == "" {
return strings.Replace(defaultTokenURL, universeDomainPlaceholder, defaultUniverseDomain, 1)
}
return strings.Replace(defaultTokenURL, universeDomainPlaceholder, c.UniverseDomain, 1)
}
// parse determines the type of CredentialSource needed.
func (c *Config) parse(ctx context.Context) (baseCredentialSource, error) {
//set Defaults
if c.TokenURL == "" {
c.TokenURL = c.tokenURL()
}
supplierOptions := SupplierOptions{Audience: c.Audience, SubjectTokenType: c.SubjectTokenType}
if c.AwsSecurityCredentialsSupplier != nil {
awsCredSource := awsCredentialSource{
awsSecurityCredentialsSupplier: c.AwsSecurityCredentialsSupplier,
targetResource: c.Audience,
supplierOptions: supplierOptions,
ctx: ctx,
}
return awsCredSource, nil
} else if c.SubjectTokenSupplier != nil {
return programmaticRefreshCredentialSource{subjectTokenSupplier: c.SubjectTokenSupplier, supplierOptions: supplierOptions, ctx: ctx}, nil
} else if len(c.CredentialSource.EnvironmentID) > 3 && c.CredentialSource.EnvironmentID[:3] == "aws" {
if awsVersion, err := strconv.Atoi(c.CredentialSource.EnvironmentID[3:]); err == nil {
if awsVersion != 1 {
return nil, fmt.Errorf("oauth2/google/externalaccount: aws version '%d' is not supported in the current build", awsVersion)
}
awsCredSource := awsCredentialSource{
environmentID: c.CredentialSource.EnvironmentID,
regionURL: c.CredentialSource.RegionURL,
regionalCredVerificationURL: c.CredentialSource.RegionalCredVerificationURL,
credVerificationURL: c.CredentialSource.URL,
targetResource: c.Audience,
ctx: ctx,
}
if c.CredentialSource.IMDSv2SessionTokenURL != "" {
awsCredSource.imdsv2SessionTokenURL = c.CredentialSource.IMDSv2SessionTokenURL
}
return awsCredSource, nil
}
} else if c.CredentialSource.File != "" {
return fileCredentialSource{File: c.CredentialSource.File, Format: c.CredentialSource.Format}, nil
} else if c.CredentialSource.URL != "" {
return urlCredentialSource{URL: c.CredentialSource.URL, Headers: c.CredentialSource.Headers, Format: c.CredentialSource.Format, ctx: ctx}, nil
} else if c.CredentialSource.Executable != nil {
return createExecutableCredential(ctx, c.CredentialSource.Executable, c)
}
return nil, fmt.Errorf("oauth2/google/externalaccount: unable to parse credential source")
}
type baseCredentialSource interface {
credentialSourceType() string
subjectToken() (string, error)
}
// tokenSource is the source that handles external credentials. It is used to retrieve Tokens.
type tokenSource struct {
ctx context.Context
conf *Config
}
func getMetricsHeaderValue(conf *Config, credSource baseCredentialSource) string {
return fmt.Sprintf("gl-go/%s auth/%s google-byoid-sdk source/%s sa-impersonation/%t config-lifetime/%t",
goVersion(),
"unknown",
credSource.credentialSourceType(),
conf.ServiceAccountImpersonationURL != "",
conf.ServiceAccountImpersonationLifetimeSeconds != 0)
}
// Token allows tokenSource to conform to the oauth2.TokenSource interface.
func (ts tokenSource) Token() (*oauth2.Token, error) {
conf := ts.conf
credSource, err := conf.parse(ts.ctx)
if err != nil {
return nil, err
}
subjectToken, err := credSource.subjectToken()
if err != nil {
return nil, err
}
stsRequest := stsexchange.TokenExchangeRequest{
GrantType: "urn:ietf:params:oauth:grant-type:token-exchange",
Audience: conf.Audience,
Scope: conf.Scopes,
RequestedTokenType: "urn:ietf:params:oauth:token-type:access_token",
SubjectToken: subjectToken,
SubjectTokenType: conf.SubjectTokenType,
}
header := make(http.Header)
header.Add("Content-Type", "application/x-www-form-urlencoded")
header.Add("x-goog-api-client", getMetricsHeaderValue(conf, credSource))
clientAuth := stsexchange.ClientAuthentication{
AuthStyle: oauth2.AuthStyleInHeader,
ClientID: conf.ClientID,
ClientSecret: conf.ClientSecret,
}
var options map[string]any
// Do not pass workforce_pool_user_project when client authentication is used.
// The client ID is sufficient for determining the user project.
if conf.WorkforcePoolUserProject != "" && conf.ClientID == "" {
options = map[string]any{
"userProject": conf.WorkforcePoolUserProject,
}
}
stsResp, err := stsexchange.ExchangeToken(ts.ctx, conf.TokenURL, &stsRequest, clientAuth, header, options)
if err != nil {
return nil, err
}
accessToken := &oauth2.Token{
AccessToken: stsResp.AccessToken,
TokenType: stsResp.TokenType,
}
// The RFC8693 doesn't define the explicit 0 of "expires_in" field behavior.
if stsResp.ExpiresIn <= 0 {
return nil, fmt.Errorf("oauth2/google/externalaccount: got invalid expiry from security token service")
}
accessToken.Expiry = now().Add(time.Duration(stsResp.ExpiresIn) * time.Second)
if stsResp.RefreshToken != "" {
accessToken.RefreshToken = stsResp.RefreshToken
}
return accessToken, nil
}

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@@ -0,0 +1,312 @@
// Copyright 2022 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package externalaccount
import (
"bytes"
"context"
"encoding/json"
"errors"
"fmt"
"io"
"os"
"os/exec"
"regexp"
"strings"
"time"
)
var serviceAccountImpersonationRE = regexp.MustCompile("https://iamcredentials\\..+/v1/projects/-/serviceAccounts/(.*@.*):generateAccessToken")
const (
executableSupportedMaxVersion = 1
defaultTimeout = 30 * time.Second
timeoutMinimum = 5 * time.Second
timeoutMaximum = 120 * time.Second
executableSource = "response"
outputFileSource = "output file"
)
type nonCacheableError struct {
message string
}
func (nce nonCacheableError) Error() string {
return nce.message
}
func missingFieldError(source, field string) error {
return fmt.Errorf("oauth2/google/externalaccount: %v missing `%q` field", source, field)
}
func jsonParsingError(source, data string) error {
return fmt.Errorf("oauth2/google/externalaccount: unable to parse %v\nResponse: %v", source, data)
}
func malformedFailureError() error {
return nonCacheableError{"oauth2/google/externalaccount: response must include `error` and `message` fields when unsuccessful"}
}
func userDefinedError(code, message string) error {
return nonCacheableError{fmt.Sprintf("oauth2/google/externalaccount: response contains unsuccessful response: (%v) %v", code, message)}
}
func unsupportedVersionError(source string, version int) error {
return fmt.Errorf("oauth2/google/externalaccount: %v contains unsupported version: %v", source, version)
}
func tokenExpiredError() error {
return nonCacheableError{"oauth2/google/externalaccount: the token returned by the executable is expired"}
}
func tokenTypeError(source string) error {
return fmt.Errorf("oauth2/google/externalaccount: %v contains unsupported token type", source)
}
func exitCodeError(exitCode int) error {
return fmt.Errorf("oauth2/google/externalaccount: executable command failed with exit code %v", exitCode)
}
func executableError(err error) error {
return fmt.Errorf("oauth2/google/externalaccount: executable command failed: %v", err)
}
func executablesDisallowedError() error {
return errors.New("oauth2/google/externalaccount: executables need to be explicitly allowed (set GOOGLE_EXTERNAL_ACCOUNT_ALLOW_EXECUTABLES to '1') to run")
}
func timeoutRangeError() error {
return errors.New("oauth2/google/externalaccount: invalid `timeout_millis` field — executable timeout must be between 5 and 120 seconds")
}
func commandMissingError() error {
return errors.New("oauth2/google/externalaccount: missing `command` field — executable command must be provided")
}
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.ExitCode())
}
return nil, executableError(err)
}
bytesStdout := bytes.TrimSpace(stdout.Bytes())
if len(bytesStdout) > 0 {
return bytesStdout, nil
}
return bytes.TrimSpace(stderr.Bytes()), nil
}
type executableCredentialSource struct {
Command string
Timeout time.Duration
OutputFile string
ctx context.Context
config *Config
env environment
}
// CreateExecutableCredential creates an executableCredentialSource given an ExecutableConfig.
// It also performs defaulting and type conversions.
func createExecutableCredential(ctx context.Context, ec *ExecutableConfig, config *Config) (executableCredentialSource, error) {
if ec.Command == "" {
return executableCredentialSource{}, commandMissingError()
}
result := executableCredentialSource{}
result.Command = ec.Command
if ec.TimeoutMillis == nil {
result.Timeout = defaultTimeout
} else {
result.Timeout = time.Duration(*ec.TimeoutMillis) * time.Millisecond
if result.Timeout < timeoutMinimum || result.Timeout > timeoutMaximum {
return executableCredentialSource{}, timeoutRangeError()
}
}
result.OutputFile = ec.OutputFile
result.ctx = ctx
result.config = config
result.env = runtimeEnvironment{}
return result, nil
}
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 (cs executableCredentialSource) 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))
}
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 && cs.OutputFile != "" {
return "", missingFieldError(source, "expiration_time")
}
if result.TokenType == "" {
return "", missingFieldError(source, "token_type")
}
if result.ExpirationTime != 0 && result.ExpirationTime < now {
return "", tokenExpiredError()
}
if result.TokenType == "urn:ietf:params:oauth:token-type:jwt" || result.TokenType == "urn:ietf:params:oauth:token-type:id_token" {
if result.IdToken == "" {
return "", missingFieldError(source, "id_token")
}
return result.IdToken, nil
}
if result.TokenType == "urn:ietf:params:oauth:token-type:saml2" {
if result.SamlResponse == "" {
return "", missingFieldError(source, "saml_response")
}
return result.SamlResponse, nil
}
return "", tokenTypeError(source)
}
func (cs executableCredentialSource) credentialSourceType() string {
return "executable"
}
func (cs executableCredentialSource) subjectToken() (string, error) {
if token, err := cs.getTokenFromOutputFile(); token != "" || err != nil {
return token, err
}
return cs.getTokenFromExecutableCommand()
}
func (cs executableCredentialSource) getTokenFromOutputFile() (token string, err error) {
if cs.OutputFile == "" {
// This ExecutableCredentialSource doesn't use an OutputFile.
return "", nil
}
file, err := os.Open(cs.OutputFile)
if err != nil {
// No OutputFile found. Hasn't been created yet, so skip it.
return "", nil
}
defer file.Close()
data, err := io.ReadAll(io.LimitReader(file, 1<<20))
if err != nil || len(data) == 0 {
// Cachefile exists, but no data found. Get new credential.
return "", nil
}
token, err = cs.parseSubjectTokenFromSource(data, outputFileSource, cs.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 (cs executableCredentialSource) executableEnvironment() []string {
result := cs.env.existingEnv()
result = append(result, fmt.Sprintf("GOOGLE_EXTERNAL_ACCOUNT_AUDIENCE=%v", cs.config.Audience))
result = append(result, fmt.Sprintf("GOOGLE_EXTERNAL_ACCOUNT_TOKEN_TYPE=%v", cs.config.SubjectTokenType))
result = append(result, "GOOGLE_EXTERNAL_ACCOUNT_INTERACTIVE=0")
if cs.config.ServiceAccountImpersonationURL != "" {
matches := serviceAccountImpersonationRE.FindStringSubmatch(cs.config.ServiceAccountImpersonationURL)
if matches != nil {
result = append(result, fmt.Sprintf("GOOGLE_EXTERNAL_ACCOUNT_IMPERSONATED_EMAIL=%v", matches[1]))
}
}
if cs.OutputFile != "" {
result = append(result, fmt.Sprintf("GOOGLE_EXTERNAL_ACCOUNT_OUTPUT_FILE=%v", cs.OutputFile))
}
return result
}
func (cs executableCredentialSource) getTokenFromExecutableCommand() (string, error) {
// For security reasons, we need our consumers to set this environment variable to allow executables to be run.
if cs.env.getenv("GOOGLE_EXTERNAL_ACCOUNT_ALLOW_EXECUTABLES") != "1" {
return "", executablesDisallowedError()
}
ctx, cancel := context.WithDeadline(cs.ctx, cs.env.now().Add(cs.Timeout))
defer cancel()
output, err := cs.env.run(ctx, cs.Command, cs.executableEnvironment())
if err != nil {
return "", err
}
return cs.parseSubjectTokenFromSource(output, executableSource, cs.env.now().Unix())
}

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// Copyright 2020 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package externalaccount
import (
"bytes"
"encoding/json"
"errors"
"fmt"
"io"
"os"
)
type fileCredentialSource struct {
File string
Format Format
}
func (cs fileCredentialSource) credentialSourceType() string {
return "file"
}
func (cs fileCredentialSource) subjectToken() (string, error) {
tokenFile, err := os.Open(cs.File)
if err != nil {
return "", fmt.Errorf("oauth2/google/externalaccount: failed to open credential file %q", cs.File)
}
defer tokenFile.Close()
tokenBytes, err := io.ReadAll(io.LimitReader(tokenFile, 1<<20))
if err != nil {
return "", fmt.Errorf("oauth2/google/externalaccount: failed to read credential file: %v", err)
}
tokenBytes = bytes.TrimSpace(tokenBytes)
switch cs.Format.Type {
case "json":
jsonData := make(map[string]any)
err = json.Unmarshal(tokenBytes, &jsonData)
if err != nil {
return "", fmt.Errorf("oauth2/google/externalaccount: failed to unmarshal subject token file: %v", err)
}
val, ok := jsonData[cs.Format.SubjectTokenFieldName]
if !ok {
return "", errors.New("oauth2/google/externalaccount: provided subject_token_field_name not found in credentials")
}
token, ok := val.(string)
if !ok {
return "", errors.New("oauth2/google/externalaccount: improperly formatted subject token")
}
return token, nil
case "text":
return string(tokenBytes), nil
case "":
return string(tokenBytes), nil
default:
return "", errors.New("oauth2/google/externalaccount: invalid credential_source file format type")
}
}

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// Copyright 2023 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
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 "UNKNOWN"
}

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@@ -0,0 +1,21 @@
// Copyright 2024 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package externalaccount
import "context"
type programmaticRefreshCredentialSource struct {
supplierOptions SupplierOptions
subjectTokenSupplier SubjectTokenSupplier
ctx context.Context
}
func (cs programmaticRefreshCredentialSource) credentialSourceType() string {
return "programmatic"
}
func (cs programmaticRefreshCredentialSource) subjectToken() (string, error) {
return cs.subjectTokenSupplier.SubjectToken(cs.ctx, cs.supplierOptions)
}

View File

@@ -0,0 +1,78 @@
// Copyright 2020 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package externalaccount
import (
"context"
"encoding/json"
"errors"
"fmt"
"io"
"net/http"
"golang.org/x/oauth2"
)
type urlCredentialSource struct {
URL string
Headers map[string]string
Format Format
ctx context.Context
}
func (cs urlCredentialSource) credentialSourceType() string {
return "url"
}
func (cs urlCredentialSource) subjectToken() (string, error) {
client := oauth2.NewClient(cs.ctx, nil)
req, err := http.NewRequest("GET", cs.URL, nil)
if err != nil {
return "", fmt.Errorf("oauth2/google/externalaccount: HTTP request for URL-sourced credential failed: %v", err)
}
req = req.WithContext(cs.ctx)
for key, val := range cs.Headers {
req.Header.Add(key, val)
}
resp, err := client.Do(req)
if err != nil {
return "", fmt.Errorf("oauth2/google/externalaccount: invalid response when retrieving subject token: %v", err)
}
defer resp.Body.Close()
respBody, err := io.ReadAll(io.LimitReader(resp.Body, 1<<20))
if err != nil {
return "", fmt.Errorf("oauth2/google/externalaccount: invalid body in subject token URL query: %v", err)
}
if c := resp.StatusCode; c < 200 || c > 299 {
return "", fmt.Errorf("oauth2/google/externalaccount: status code %d: %s", c, respBody)
}
switch cs.Format.Type {
case "json":
jsonData := make(map[string]any)
err = json.Unmarshal(respBody, &jsonData)
if err != nil {
return "", fmt.Errorf("oauth2/google/externalaccount: failed to unmarshal subject token file: %v", err)
}
val, ok := jsonData[cs.Format.SubjectTokenFieldName]
if !ok {
return "", errors.New("oauth2/google/externalaccount: provided subject_token_field_name not found in credentials")
}
token, ok := val.(string)
if !ok {
return "", errors.New("oauth2/google/externalaccount: improperly formatted subject token")
}
return token, nil
case "text":
return string(respBody), nil
case "":
return string(respBody), nil
default:
return "", errors.New("oauth2/google/externalaccount: invalid credential_source file format type")
}
}