vendor: update buildkit to master@ae9d0f5

Signed-off-by: Justin Chadwell <me@jedevc.com>

vendor/golang.org/x/oauth2/google/internal/externalaccount/aws.go

@@ -52,6 +52,13 @@ const (
 	// 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"
 
@@ -241,6 +248,7 @@ type awsCredentialSource struct {
 	RegionURL                   string
 	RegionalCredVerificationURL string
 	CredVerificationURL         string
+	IMDSv2SessionTokenURL       string
 	TargetResource              string
 	requestSigner               *awsRequestSigner
 	region                      string
@@ -268,12 +276,22 @@ func (cs awsCredentialSource) doRequest(req *http.Request) (*http.Response, erro
 
 func (cs awsCredentialSource) subjectToken() (string, error) {
 	if cs.requestSigner == nil {
-		awsSecurityCredentials, err := cs.getSecurityCredentials()
+		awsSessionToken, err := cs.getAWSSessionToken()
 		if err != nil {
 			return "", err
 		}
 
-		if cs.region, err = cs.getRegion(); err != nil {
+		headers := make(map[string]string)
+		if awsSessionToken != "" {
+			headers[awsIMDSv2SessionTokenHeader] = awsSessionToken
+		}
+
+		awsSecurityCredentials, err := cs.getSecurityCredentials(headers)
+		if err != nil {
+			return "", err
+		}
+
+		if cs.region, err = cs.getRegion(headers); err != nil {
 			return "", err
 		}
 
@@ -340,7 +358,37 @@ func (cs awsCredentialSource) subjectToken() (string, error) {
 	return url.QueryEscape(string(result)), nil
 }
 
-func (cs *awsCredentialSource) getRegion() (string, error) {
+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 := ioutil.ReadAll(io.LimitReader(resp.Body, 1<<20))
+	if err != nil {
+		return "", err
+	}
+
+	if resp.StatusCode != 200 {
+		return "", fmt.Errorf("oauth2/google: unable to retrieve AWS session token - %s", string(respBody))
+	}
+
+	return string(respBody), nil
+}
+
+func (cs *awsCredentialSource) getRegion(headers map[string]string) (string, error) {
 	if envAwsRegion := getenv("AWS_REGION"); envAwsRegion != "" {
 		return envAwsRegion, nil
 	}
@@ -357,6 +405,10 @@ func (cs *awsCredentialSource) getRegion() (string, error) {
 		return "", err
 	}
 
+	for name, value := range headers {
+		req.Header.Add(name, value)
+	}
+
 	resp, err := cs.doRequest(req)
 	if err != nil {
 		return "", err
@@ -381,7 +433,7 @@ func (cs *awsCredentialSource) getRegion() (string, error) {
 	return string(respBody[:respBodyEnd]), nil
 }
 
-func (cs *awsCredentialSource) getSecurityCredentials() (result awsSecurityCredentials, err error) {
+func (cs *awsCredentialSource) getSecurityCredentials(headers map[string]string) (result awsSecurityCredentials, err error) {
 	if accessKeyID := getenv("AWS_ACCESS_KEY_ID"); accessKeyID != "" {
 		if secretAccessKey := getenv("AWS_SECRET_ACCESS_KEY"); secretAccessKey != "" {
 			return awsSecurityCredentials{
@@ -392,12 +444,12 @@ func (cs *awsCredentialSource) getSecurityCredentials() (result awsSecurityCrede
 		}
 	}
 
-	roleName, err := cs.getMetadataRoleName()
+	roleName, err := cs.getMetadataRoleName(headers)
 	if err != nil {
 		return
 	}
 
-	credentials, err := cs.getMetadataSecurityCredentials(roleName)
+	credentials, err := cs.getMetadataSecurityCredentials(roleName, headers)
 	if err != nil {
 		return
 	}
@@ -413,7 +465,7 @@ func (cs *awsCredentialSource) getSecurityCredentials() (result awsSecurityCrede
 	return credentials, nil
 }
 
-func (cs *awsCredentialSource) getMetadataSecurityCredentials(roleName string) (awsSecurityCredentials, error) {
+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)
@@ -422,6 +474,10 @@ func (cs *awsCredentialSource) getMetadataSecurityCredentials(roleName string) (
 	}
 	req.Header.Add("Content-Type", "application/json")
 
+	for name, value := range headers {
+		req.Header.Add(name, value)
+	}
+
 	resp, err := cs.doRequest(req)
 	if err != nil {
 		return result, err
@@ -441,7 +497,7 @@ func (cs *awsCredentialSource) getMetadataSecurityCredentials(roleName string) (
 	return result, err
 }
 
-func (cs *awsCredentialSource) getMetadataRoleName() (string, error) {
+func (cs *awsCredentialSource) getMetadataRoleName(headers map[string]string) (string, error) {
 	if cs.CredVerificationURL == "" {
 		return "", errors.New("oauth2/google: unable to determine the AWS metadata server security credentials endpoint")
 	}
@@ -451,6 +507,10 @@ func (cs *awsCredentialSource) getMetadataRoleName() (string, error) {
 		return "", err
 	}
 
+	for name, value := range headers {
+		req.Header.Add(name, value)
+	}
+
 	resp, err := cs.doRequest(req)
 	if err != nil {
 		return "", err

vendor/golang.org/x/oauth2/google/internal/externalaccount/basecredentials.go

@@ -39,6 +39,9 @@ type Config struct {
 	// 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.
@@ -53,6 +56,11 @@ type Config struct {
 	QuotaProjectID string
 	// Scopes contains the desired scopes for the returned access token.
 	Scopes []string
+	// The optional 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.
+	WorkforcePoolUserProject string
 }
 
 // Each element consists of a list of patterns.  validateURLs checks for matches
@@ -66,13 +74,16 @@ var (
 		regexp.MustCompile(`(?i)^sts\.googleapis\.com$`),
 		regexp.MustCompile(`(?i)^sts\.[^\.\s\/\\]+\.googleapis\.com$`),
 		regexp.MustCompile(`(?i)^[^\.\s\/\\]+-sts\.googleapis\.com$`),
+		regexp.MustCompile(`(?i)^sts-[^\.\s\/\\]+\.p\.googleapis\.com$`),
 	}
 	validImpersonateURLPatterns = []*regexp.Regexp{
 		regexp.MustCompile(`^[^\.\s\/\\]+\.iamcredentials\.googleapis\.com$`),
 		regexp.MustCompile(`^iamcredentials\.googleapis\.com$`),
 		regexp.MustCompile(`^iamcredentials\.[^\.\s\/\\]+\.googleapis\.com$`),
 		regexp.MustCompile(`^[^\.\s\/\\]+-iamcredentials\.googleapis\.com$`),
+		regexp.MustCompile(`^iamcredentials-[^\.\s\/\\]+\.p\.googleapis\.com$`),
 	}
+	validWorkforceAudiencePattern *regexp.Regexp = regexp.MustCompile(`//iam\.googleapis\.com/locations/[^/]+/workforcePools/`)
 )
 
 func validateURL(input string, patterns []*regexp.Regexp, scheme string) bool {
@@ -86,14 +97,17 @@ func validateURL(input string, patterns []*regexp.Regexp, scheme string) bool {
 	toTest := parsed.Host
 
 	for _, pattern := range patterns {
-
-		if valid := pattern.MatchString(toTest); valid {
+		if pattern.MatchString(toTest) {
 			return true
 		}
 	}
 	return false
 }
 
+func validateWorkforceAudience(input string) bool {
+	return validWorkforceAudiencePattern.MatchString(input)
+}
+
 // TokenSource Returns an external account TokenSource struct. This is to be called by package google to construct a google.Credentials.
 func (c *Config) TokenSource(ctx context.Context) (oauth2.TokenSource, error) {
 	return c.tokenSource(ctx, validTokenURLPatterns, validImpersonateURLPatterns, "https")
@@ -115,6 +129,13 @@ func (c *Config) tokenSource(ctx context.Context, tokenURLValidPats []*regexp.Re
 		}
 	}
 
+	if c.WorkforcePoolUserProject != "" {
+		valid := validateWorkforceAudience(c.Audience)
+		if !valid {
+			return nil, fmt.Errorf("oauth2/google: workforce_pool_user_project should not be set for non-workforce pool credentials")
+		}
+	}
+
 	ts := tokenSource{
 		ctx:  ctx,
 		conf: c,
@@ -124,11 +145,12 @@ func (c *Config) tokenSource(ctx context.Context, tokenURLValidPats []*regexp.Re
 	}
 	scopes := c.Scopes
 	ts.conf.Scopes = []string{"https://www.googleapis.com/auth/cloud-platform"}
-	imp := impersonateTokenSource{
-		ctx:    ctx,
-		url:    c.ServiceAccountImpersonationURL,
-		scopes: scopes,
-		ts:     oauth2.ReuseTokenSource(nil, ts),
+	imp := ImpersonateTokenSource{
+		Ctx:                  ctx,
+		URL:                  c.ServiceAccountImpersonationURL,
+		Scopes:               scopes,
+		Ts:                   oauth2.ReuseTokenSource(nil, ts),
+		TokenLifetimeSeconds: c.ServiceAccountImpersonationLifetimeSeconds,
 	}
 	return oauth2.ReuseTokenSource(nil, imp), nil
 }
@@ -147,7 +169,7 @@ type format struct {
 }
 
 // CredentialSource stores the information necessary to retrieve the credentials for the STS exchange.
-// Either the File or the URL field should be filled, depending on the kind of credential in question.
+// One field amongst File, URL, and Executable should be filled, depending on the kind of credential in question.
 // The EnvironmentID should start with AWS if being used for an AWS credential.
 type CredentialSource struct {
 	File string `json:"file"`
@@ -155,33 +177,50 @@ type CredentialSource struct {
 	URL     string            `json:"url"`
 	Headers map[string]string `json:"headers"`
 
+	Executable *ExecutableConfig `json:"executable"`
+
 	EnvironmentID               string `json:"environment_id"`
 	RegionURL                   string `json:"region_url"`
 	RegionalCredVerificationURL string `json:"regional_cred_verification_url"`
 	CredVerificationURL         string `json:"cred_verification_url"`
+	IMDSv2SessionTokenURL       string `json:"imdsv2_session_token_url"`
 	Format                      format `json:"format"`
 }
 
-// parse determines the type of CredentialSource needed
+type ExecutableConfig struct {
+	Command       string `json:"command"`
+	TimeoutMillis *int   `json:"timeout_millis"`
+	OutputFile    string `json:"output_file"`
+}
+
+// parse determines the type of CredentialSource needed.
 func (c *Config) parse(ctx context.Context) (baseCredentialSource, error) {
 	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: aws version '%d' is not supported in the current build", awsVersion)
 			}
-			return awsCredentialSource{
+
+			awsCredSource := awsCredentialSource{
 				EnvironmentID:               c.CredentialSource.EnvironmentID,
 				RegionURL:                   c.CredentialSource.RegionURL,
 				RegionalCredVerificationURL: c.CredentialSource.RegionalCredVerificationURL,
 				CredVerificationURL:         c.CredentialSource.URL,
 				TargetResource:              c.Audience,
 				ctx:                         ctx,
-			}, nil
+			}
+			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: unable to parse credential source")
 }
@@ -224,7 +263,15 @@ func (ts tokenSource) Token() (*oauth2.Token, error) {
 		ClientID:     conf.ClientID,
 		ClientSecret: conf.ClientSecret,
 	}
-	stsResp, err := exchangeToken(ts.ctx, conf.TokenURL, &stsRequest, clientAuth, header, nil)
+	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 conf.WorkforcePoolUserProject != "" && conf.ClientID == "" {
+		options = map[string]interface{}{
+			"userProject": conf.WorkforcePoolUserProject,
+		}
+	}
+	stsResp, err := exchangeToken(ts.ctx, conf.TokenURL, &stsRequest, clientAuth, header, options)
 	if err != nil {
 		return nil, err
 	}

vendor/golang.org/x/oauth2/google/internal/externalaccount/executablecredsource.go

@@ -0,0 +1,309 @@
+// 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"
+	"io/ioutil"
+	"os"
+	"os/exec"
+	"regexp"
+	"strings"
+	"time"
+)
+
+var serviceAccountImpersonationRE = regexp.MustCompile("https://iamcredentials.googleapis.com/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: %v missing `%q` field", source, field)
+}
+
+func jsonParsingError(source, data string) error {
+	return fmt.Errorf("oauth2/google: unable to parse %v\nResponse: %v", source, data)
+}
+
+func malformedFailureError() error {
+	return nonCacheableError{"oauth2/google: response must include `error` and `message` fields when unsuccessful"}
+}
+
+func userDefinedError(code, message string) error {
+	return nonCacheableError{fmt.Sprintf("oauth2/google: response contains unsuccessful response: (%v) %v", code, message)}
+}
+
+func unsupportedVersionError(source string, version int) error {
+	return fmt.Errorf("oauth2/google: %v contains unsupported version: %v", source, version)
+}
+
+func tokenExpiredError() error {
+	return nonCacheableError{"oauth2/google: the token returned by the executable is expired"}
+}
+
+func tokenTypeError(source string) error {
+	return fmt.Errorf("oauth2/google: %v contains unsupported token type", source)
+}
+
+func exitCodeError(exitCode int) error {
+	return fmt.Errorf("oauth2/google: executable command failed with exit code %v", exitCode)
+}
+
+func executableError(err error) error {
+	return fmt.Errorf("oauth2/google: executable command failed: %v", err)
+}
+
+func executablesDisallowedError() error {
+	return errors.New("oauth2/google: executables need to be explicitly allowed (set GOOGLE_EXTERNAL_ACCOUNT_ALLOW_EXECUTABLES to '1') to run")
+}
+
+func timeoutRangeError() error {
+	return errors.New("oauth2/google: invalid `timeout_millis` field — executable timeout must be between 5 and 120 seconds")
+}
+
+func commandMissingError() error {
+	return errors.New("oauth2/google: 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) 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 := ioutil.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())
+}

vendor/golang.org/x/oauth2/google/internal/externalaccount/impersonate.go

@@ -29,30 +29,51 @@ type impersonateTokenResponse struct {
 	ExpireTime  string `json:"expireTime"`
 }
 
-type impersonateTokenSource struct {
-	ctx context.Context
-	ts  oauth2.TokenSource
+// ImpersonateTokenSource 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.
+type ImpersonateTokenSource struct {
+	// Ctx is the execution context of the impersonation process
+	// used to perform http call to the URL. Required
+	Ctx context.Context
+	// Ts is the source credential used to generate a token on the
+	// impersonated service account. Required.
+	Ts oauth2.TokenSource
 
-	url    string
-	scopes []string
+	// URL is the endpoint to call to generate a token
+	// on behalf 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.
+	TokenLifetimeSeconds int
 }
 
 // Token performs the exchange to get a temporary service account token to allow access to GCP.
-func (its impersonateTokenSource) Token() (*oauth2.Token, error) {
+func (its ImpersonateTokenSource) Token() (*oauth2.Token, error) {
+	lifetimeString := "3600s"
+	if its.TokenLifetimeSeconds != 0 {
+		lifetimeString = fmt.Sprintf("%ds", its.TokenLifetimeSeconds)
+	}
 	reqBody := generateAccessTokenReq{
-		Lifetime: "3600s",
-		Scope:    its.scopes,
+		Lifetime:  lifetimeString,
+		Scope:     its.Scopes,
+		Delegates: its.Delegates,
 	}
 	b, err := json.Marshal(reqBody)
 	if err != nil {
 		return nil, fmt.Errorf("oauth2/google: unable to marshal request: %v", err)
 	}
-	client := oauth2.NewClient(its.ctx, its.ts)
-	req, err := http.NewRequest("POST", its.url, bytes.NewReader(b))
+	client := oauth2.NewClient(its.Ctx, its.Ts)
+	req, err := http.NewRequest("POST", its.URL, bytes.NewReader(b))
 	if err != nil {
 		return nil, fmt.Errorf("oauth2/google: unable to create impersonation request: %v", err)
 	}
-	req = req.WithContext(its.ctx)
+	req = req.WithContext(its.Ctx)
 	req.Header.Set("Content-Type", "application/json")
 
 	resp, err := client.Do(req)