cmd,feature: add identity token auto generation for workload identity (#18373)
Adds the ability to detect what provider the client is running on and tries fetch the ID token to use with Workload Identity. Updates https://github.com/tailscale/corp/issues/33316 Signed-off-by: Danni Popova <danni@tailscale.com>main
Danni Popova
3 months ago
committed by
GitHub
parent
58042e2de3
commit
6a6aa805d6
@ -1 +1 @@ |
||||
sha256-MKMLpGUYzUPYKjVYQSnxDQDdH1oXaM8bCIbhCTuGeV0= |
||||
sha256-WeMTOkERj4hvdg4yPaZ1gRgKnhRIBXX55kUVbX/k/xM= |
||||
|
||||
@ -0,0 +1,242 @@ |
||||
// Copyright (c) Tailscale Inc & AUTHORS
|
||||
// SPDX-License-Identifier: BSD-3-Clause
|
||||
|
||||
// Package wif deals with obtaining ID tokens from provider VMs
|
||||
// to be used as part of Workload Identity Federation
|
||||
package wif |
||||
|
||||
import ( |
||||
"context" |
||||
"encoding/json" |
||||
"errors" |
||||
"fmt" |
||||
"io" |
||||
"net/http" |
||||
"net/url" |
||||
"os" |
||||
"strings" |
||||
"time" |
||||
|
||||
"github.com/aws/aws-sdk-go-v2/aws" |
||||
"github.com/aws/aws-sdk-go-v2/config" |
||||
"github.com/aws/aws-sdk-go-v2/feature/ec2/imds" |
||||
"github.com/aws/aws-sdk-go-v2/service/sts" |
||||
"github.com/aws/smithy-go" |
||||
"tailscale.com/util/httpm" |
||||
) |
||||
|
||||
type Environment string |
||||
|
||||
const ( |
||||
EnvGitHub Environment = "github" |
||||
EnvAWS Environment = "aws" |
||||
EnvGCP Environment = "gcp" |
||||
EnvNone Environment = "none" |
||||
) |
||||
|
||||
// ObtainProviderToken tries to detect what provider the client is running in
|
||||
// and then tries to obtain an ID token for the audience that is passed as an argument
|
||||
// To detect the environment, we do it in the following intentional order:
|
||||
// 1. GitHub Actions (strongest env signals; may run atop any cloud)
|
||||
// 2. AWS via IMDSv2 token endpoint (does not require env vars)
|
||||
// 3. GCP via metadata header semantics
|
||||
// 4. Azure via metadata endpoint
|
||||
func ObtainProviderToken(ctx context.Context, audience string) (string, error) { |
||||
env := detectEnvironment(ctx) |
||||
|
||||
switch env { |
||||
case EnvGitHub: |
||||
return acquireGitHubActionsIDToken(ctx, audience) |
||||
case EnvAWS: |
||||
return acquireAWSWebIdentityToken(ctx, audience) |
||||
case EnvGCP: |
||||
return acquireGCPMetadataIDToken(ctx, audience) |
||||
default: |
||||
return "", errors.New("could not detect environment; provide --id-token explicitly") |
||||
} |
||||
} |
||||
|
||||
func detectEnvironment(ctx context.Context) Environment { |
||||
if os.Getenv("ACTIONS_ID_TOKEN_REQUEST_URL") != "" && |
||||
os.Getenv("ACTIONS_ID_TOKEN_REQUEST_TOKEN") != "" { |
||||
return EnvGitHub |
||||
} |
||||
|
||||
client := httpClient() |
||||
if detectAWSIMDSv2(ctx, client) { |
||||
return EnvAWS |
||||
} |
||||
if detectGCPMetadata(ctx, client) { |
||||
return EnvGCP |
||||
} |
||||
return EnvNone |
||||
} |
||||
|
||||
func httpClient() *http.Client { |
||||
return &http.Client{ |
||||
Timeout: time.Second * 5, |
||||
} |
||||
} |
||||
|
||||
func detectAWSIMDSv2(ctx context.Context, client *http.Client) bool { |
||||
req, err := http.NewRequestWithContext(ctx, httpm.PUT, "http://169.254.169.254/latest/api/token", nil) |
||||
if err != nil { |
||||
return false |
||||
} |
||||
req.Header.Set("X-aws-ec2-metadata-token-ttl-seconds", "1") |
||||
|
||||
resp, err := client.Do(req) |
||||
if err != nil { |
||||
return false |
||||
} |
||||
defer resp.Body.Close() |
||||
|
||||
return resp.StatusCode == http.StatusOK |
||||
} |
||||
|
||||
func detectGCPMetadata(ctx context.Context, client *http.Client) bool { |
||||
req, err := http.NewRequestWithContext(ctx, httpm.GET, "http://metadata.google.internal", nil) |
||||
if err != nil { |
||||
return false |
||||
} |
||||
req.Header.Set("Metadata-Flavor", "Google") |
||||
|
||||
resp, err := client.Do(req) |
||||
if err != nil { |
||||
return false |
||||
} |
||||
defer resp.Body.Close() |
||||
|
||||
return resp.Header.Get("Metadata-Flavor") == "Google" |
||||
} |
||||
|
||||
type githubOIDCResponse struct { |
||||
Value string `json:"value"` |
||||
} |
||||
|
||||
func acquireGitHubActionsIDToken(ctx context.Context, audience string) (string, error) { |
||||
reqURL := os.Getenv("ACTIONS_ID_TOKEN_REQUEST_URL") |
||||
reqTok := os.Getenv("ACTIONS_ID_TOKEN_REQUEST_TOKEN") |
||||
if reqURL == "" || reqTok == "" { |
||||
return "", errors.New("missing ACTIONS_ID_TOKEN_REQUEST_URL/TOKEN (ensure workflow has permissions: id-token: write)") |
||||
} |
||||
|
||||
u, err := url.Parse(reqURL) |
||||
if err != nil { |
||||
return "", fmt.Errorf("parse ACTIONS_ID_TOKEN_REQUEST_URL: %w", err) |
||||
} |
||||
if strings.TrimSpace(audience) != "" { |
||||
q := u.Query() |
||||
q.Set("audience", strings.TrimSpace(audience)) |
||||
u.RawQuery = q.Encode() |
||||
} |
||||
|
||||
req, err := http.NewRequestWithContext(ctx, httpm.GET, u.String(), nil) |
||||
if err != nil { |
||||
return "", fmt.Errorf("build request: %w", err) |
||||
} |
||||
req.Header.Set("Authorization", "Bearer "+reqTok) |
||||
req.Header.Set("Accept", "application/json") |
||||
|
||||
client := httpClient() |
||||
resp, err := client.Do(req) |
||||
if err != nil { |
||||
return "", fmt.Errorf("request github oidc token: %w", err) |
||||
} |
||||
defer resp.Body.Close() |
||||
|
||||
if resp.StatusCode/100 != 2 { |
||||
b, _ := io.ReadAll(io.LimitReader(resp.Body, 2048)) |
||||
return "", fmt.Errorf("github oidc token endpoint returned %s: %s", resp.Status, strings.TrimSpace(string(b))) |
||||
} |
||||
|
||||
var tr githubOIDCResponse |
||||
if err := json.NewDecoder(resp.Body).Decode(&tr); err != nil { |
||||
return "", fmt.Errorf("decode github oidc response: %w", err) |
||||
} |
||||
if strings.TrimSpace(tr.Value) == "" { |
||||
return "", errors.New("github oidc response contained empty token") |
||||
} |
||||
|
||||
// GitHub response doesn't provide exp directly; caller can parse JWT if needed.
|
||||
return tr.Value, nil |
||||
} |
||||
|
||||
func acquireAWSWebIdentityToken(ctx context.Context, audience string) (string, error) { |
||||
// LoadDefaultConfig wires up the default credential chain (incl. IMDS).
|
||||
cfg, err := config.LoadDefaultConfig(ctx) |
||||
if err != nil { |
||||
return "", fmt.Errorf("load aws config: %w", err) |
||||
} |
||||
|
||||
// Verify credentials are available before proceeding.
|
||||
if _, err := cfg.Credentials.Retrieve(ctx); err != nil { |
||||
return "", fmt.Errorf("AWS credentials unavailable (instance profile/IMDS?): %w", err) |
||||
} |
||||
|
||||
imdsClient := imds.NewFromConfig(cfg) |
||||
region, err := imdsClient.GetRegion(ctx, &imds.GetRegionInput{}) |
||||
if err != nil { |
||||
return "", fmt.Errorf("couldn't get AWS region: %w", err) |
||||
} |
||||
cfg.Region = region.Region |
||||
|
||||
stsClient := sts.NewFromConfig(cfg) |
||||
in := &sts.GetWebIdentityTokenInput{ |
||||
Audience: []string{strings.TrimSpace(audience)}, |
||||
SigningAlgorithm: aws.String("ES384"), |
||||
DurationSeconds: aws.Int32(300), // 5 minutes
|
||||
} |
||||
|
||||
out, err := stsClient.GetWebIdentityToken(ctx, in) |
||||
if err != nil { |
||||
var apiErr smithy.APIError |
||||
if errors.As(err, &apiErr) { |
||||
return "", fmt.Errorf("aws sts:GetWebIdentityToken failed (%s): %w", apiErr.ErrorCode(), err) |
||||
} |
||||
return "", fmt.Errorf("aws sts:GetWebIdentityToken failed: %w", err) |
||||
} |
||||
|
||||
if out.WebIdentityToken == nil || strings.TrimSpace(*out.WebIdentityToken) == "" { |
||||
return "", fmt.Errorf("aws sts:GetWebIdentityToken returned empty token") |
||||
} |
||||
|
||||
return *out.WebIdentityToken, nil |
||||
} |
||||
|
||||
func acquireGCPMetadataIDToken(ctx context.Context, audience string) (string, error) { |
||||
u := "http://metadata.google.internal/computeMetadata/v1/instance/service-accounts/default/identity" |
||||
v := url.Values{} |
||||
v.Set("audience", strings.TrimSpace(audience)) |
||||
v.Set("format", "full") |
||||
fullURL := u + "?" + v.Encode() |
||||
|
||||
req, err := http.NewRequestWithContext(ctx, httpm.GET, fullURL, nil) |
||||
if err != nil { |
||||
return "", fmt.Errorf("build request: %w", err) |
||||
} |
||||
req.Header.Set("Metadata-Flavor", "Google") |
||||
|
||||
client := httpClient() |
||||
resp, err := client.Do(req) |
||||
if err != nil { |
||||
return "", fmt.Errorf("call gcp metadata identity endpoint: %w", err) |
||||
} |
||||
defer resp.Body.Close() |
||||
|
||||
if resp.StatusCode/100 != 2 { |
||||
b, _ := io.ReadAll(io.LimitReader(resp.Body, 2048)) |
||||
return "", fmt.Errorf("gcp metadata identity endpoint returned %s: %s", resp.Status, strings.TrimSpace(string(b))) |
||||
} |
||||
|
||||
b, err := io.ReadAll(io.LimitReader(resp.Body, 1024*1024)) |
||||
if err != nil { |
||||
return "", fmt.Errorf("read gcp id token: %w", err) |
||||
} |
||||
jwt := strings.TrimSpace(string(b)) |
||||
if jwt == "" { |
||||
return "", fmt.Errorf("gcp metadata returned empty token") |
||||
} |
||||
|
||||
return jwt, nil |
||||
} |
||||
Loading…
Reference in new issue