mirror of https://github.com/tailscale/tailscale/
cmd,feature: add workload idenity auto discovery
Adds the ability to auto detect what provider the client is running on and tries fetch the JWT to use with Workload Identity. Updates https://github.com/tailscale/corp/issues/33316 Signed-off-by: Danni Popova <danni@tailscale.com>danni/wif-auto-detect-env
Danni Popova
5 days ago
parent
76fb09c6bd
commit
3fc49ad980
@ -1 +1 @@
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sha256-MKMLpGUYzUPYKjVYQSnxDQDdH1oXaM8bCIbhCTuGeV0=
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sha256-WeMTOkERj4hvdg4yPaZ1gRgKnhRIBXX55kUVbX/k/xM=
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@ -0,0 +1,242 @@
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// Copyright (c) Tailscale Inc & AUTHORS
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// SPDX-License-Identifier: BSD-3-Clause
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// Package wif deals with obtaining ID tokens from provider VMs
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// to be used as part of Workload Identity Federation
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package wif
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import (
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"context"
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"encoding/json"
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"errors"
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"fmt"
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"io"
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"net/http"
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"net/url"
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"os"
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"strings"
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"time"
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"github.com/aws/aws-sdk-go-v2/aws"
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"github.com/aws/aws-sdk-go-v2/config"
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"github.com/aws/aws-sdk-go-v2/feature/ec2/imds"
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"github.com/aws/aws-sdk-go-v2/service/sts"
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"github.com/aws/smithy-go"
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"tailscale.com/util/httpm"
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)
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type Environment string
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const (
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EnvGitHub Environment = "github"
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EnvAWS Environment = "aws"
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EnvGCP Environment = "gcp"
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EnvNone Environment = "none"
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)
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// ObtainProviderToken tries to detect what provider the client is running in
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// and then tries to obtain an ID token for the audience that is passed as an argument
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// To detect the environment, we do it in the following intentional order:
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// 1. GitHub Actions (strongest env signals; may run atop any cloud)
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// 2. AWS via IMDSv2 token endpoint (does not require env vars)
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// 3. GCP via metadata header semantics
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// 4. Azure via metadata endpoint
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func ObtainProviderToken(ctx context.Context, audience string) (token string, err error) {
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env := detectEnvironment(ctx)
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switch env {
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case EnvGitHub:
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return acquireGitHubActionsIDToken(ctx, audience)
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case EnvAWS:
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return acquireAWSWebIdentityToken(ctx, audience)
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case EnvGCP:
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return acquireGCPMetadataIDToken(ctx, audience)
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default:
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return "", errors.New("could not detect environment; provide --id-token explicitly")
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}
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}
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func detectEnvironment(ctx context.Context) Environment {
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if os.Getenv("ACTIONS_ID_TOKEN_REQUEST_URL") != "" &&
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os.Getenv("ACTIONS_ID_TOKEN_REQUEST_TOKEN") != "" {
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return EnvGitHub
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}
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client := hTTPClient()
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if detectAWSIMDSv2(ctx, client) {
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return EnvAWS
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}
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if detectGCPMetadata(ctx, client) {
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return EnvGCP
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}
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return EnvNone
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}
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func hTTPClient() *http.Client {
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return &http.Client{
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Timeout: time.Second * 5,
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}
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}
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func detectAWSIMDSv2(ctx context.Context, client *http.Client) bool {
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req, err := http.NewRequestWithContext(ctx, httpm.PUT, "http://169.254.169.254/latest/api/token", nil)
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if err != nil {
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return false
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}
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req.Header.Set("X-aws-ec2-metadata-token-ttl-seconds", "60")
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resp, err := client.Do(req)
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if err != nil {
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return false
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}
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defer resp.Body.Close()
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return resp.StatusCode == http.StatusOK
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}
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func detectGCPMetadata(ctx context.Context, client *http.Client) bool {
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req, err := http.NewRequestWithContext(ctx, httpm.GET, "http://metadata.google.internal", nil)
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if err != nil {
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return false
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}
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req.Header.Set("Metadata-Flavor", "Google")
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resp, err := client.Do(req)
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if err != nil {
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return false
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}
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defer resp.Body.Close()
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return resp.Header.Get("Metadata-Flavor") == "Google"
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}
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type githubOIDCResponse struct {
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Value string `json:"value"`
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}
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func acquireGitHubActionsIDToken(ctx context.Context, audience string) (jwt string, err error) {
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reqURL := os.Getenv("ACTIONS_ID_TOKEN_REQUEST_URL")
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reqTok := os.Getenv("ACTIONS_ID_TOKEN_REQUEST_TOKEN")
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if reqURL == "" || reqTok == "" {
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return "", errors.New("missing ACTIONS_ID_TOKEN_REQUEST_URL/TOKEN (ensure workflow has permissions: id-token: write)")
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}
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u, err := url.Parse(reqURL)
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if err != nil {
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return "", fmt.Errorf("parse ACTIONS_ID_TOKEN_REQUEST_URL: %w", err)
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}
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if strings.TrimSpace(audience) != "" {
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q := u.Query()
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q.Set("audience", strings.TrimSpace(audience))
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u.RawQuery = q.Encode()
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}
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req, err := http.NewRequestWithContext(ctx, httpm.GET, u.String(), nil)
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if err != nil {
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return "", fmt.Errorf("build request: %w", err)
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}
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req.Header.Set("Authorization", "Bearer "+reqTok)
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req.Header.Set("Accept", "application/json")
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client := hTTPClient()
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resp, err := client.Do(req)
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if err != nil {
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return "", fmt.Errorf("request github oidc token: %w", err)
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}
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defer resp.Body.Close()
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if resp.StatusCode/100 != 2 {
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b, _ := io.ReadAll(io.LimitReader(resp.Body, 2048))
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return "", fmt.Errorf("github oidc token endpoint returned %s: %s", resp.Status, strings.TrimSpace(string(b)))
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}
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var tr githubOIDCResponse
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if err := json.NewDecoder(resp.Body).Decode(&tr); err != nil {
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return "", fmt.Errorf("decode github oidc response: %w", err)
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}
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if strings.TrimSpace(tr.Value) == "" {
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return "", errors.New("github oidc response contained empty token")
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}
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// GitHub response doesn't provide exp directly; caller can parse JWT if needed.
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return tr.Value, nil
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}
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func acquireAWSWebIdentityToken(ctx context.Context, audience string) (jwt string, err error) {
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// LoadDefaultConfig wires up the default credential chain (incl. IMDS).
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cfg, err := config.LoadDefaultConfig(ctx)
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if err != nil {
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return "", fmt.Errorf("load aws config: %w", err)
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}
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// Verify credentials are available before proceeding.
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if _, err := cfg.Credentials.Retrieve(ctx); err != nil {
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return "", fmt.Errorf("AWS credentials unavailable (instance profile/IMDS?): %w", err)
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}
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imdsClient := imds.NewFromConfig(cfg)
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region, err := imdsClient.GetRegion(ctx, &imds.GetRegionInput{})
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if err != nil {
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return "", fmt.Errorf("couldn't get AWS region: %w", err)
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}
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cfg.Region = region.Region
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stsClient := sts.NewFromConfig(cfg)
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in := &sts.GetWebIdentityTokenInput{
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Audience: []string{strings.TrimSpace(audience)},
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SigningAlgorithm: aws.String("ES384"),
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DurationSeconds: aws.Int32(300), // 5 minutes
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}
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out, err := stsClient.GetWebIdentityToken(ctx, in)
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if err != nil {
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var apiErr smithy.APIError
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if errors.As(err, &apiErr) {
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return "", fmt.Errorf("aws sts:GetWebIdentityToken failed (%s): %w", apiErr.ErrorCode(), err)
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}
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return "", fmt.Errorf("aws sts:GetWebIdentityToken failed: %w", err)
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}
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if out.WebIdentityToken == nil || strings.TrimSpace(*out.WebIdentityToken) == "" {
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return "", fmt.Errorf("aws sts:GetWebIdentityToken returned empty token")
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}
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return *out.WebIdentityToken, nil
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}
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func acquireGCPMetadataIDToken(ctx context.Context, audience string) (jwt string, err error) {
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u := "http://metadata.google.internal/computeMetadata/v1/instance/service-accounts/default/identity"
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v := url.Values{}
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v.Set("audience", strings.TrimSpace(audience))
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v.Set("format", "full")
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fullURL := u + "?" + v.Encode()
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req, err := http.NewRequestWithContext(ctx, httpm.GET, fullURL, nil)
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if err != nil {
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return "", fmt.Errorf("build request: %w", err)
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}
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req.Header.Set("Metadata-Flavor", "Google")
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client := hTTPClient()
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resp, err := client.Do(req)
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if err != nil {
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return "", fmt.Errorf("call gcp metadata identity endpoint: %w", err)
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}
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defer resp.Body.Close()
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if resp.StatusCode/100 != 2 {
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b, _ := io.ReadAll(io.LimitReader(resp.Body, 2048))
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return "", fmt.Errorf("gcp metadata identity endpoint returned %s: %s", resp.Status, strings.TrimSpace(string(b)))
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}
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b, err := io.ReadAll(io.LimitReader(resp.Body, 1024*1024))
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if err != nil {
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return "", fmt.Errorf("read gcp id token: %w", err)
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}
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jwt = strings.TrimSpace(string(b))
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if jwt == "" {
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return "", fmt.Errorf("gcp metadata returned empty token")
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}
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return jwt, nil
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}
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