Update

vendor/tailscale.com/feature/identityfederation/identityfederation.go

@@ -0,0 +1,139 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+// Package identityfederation registers support for using ID tokens to
+// automatically request authkeys for logging in.
+package identityfederation
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"net/http"
+	"net/url"
+	"strconv"
+	"strings"
+	"time"
+
+	"golang.org/x/oauth2"
+	"tailscale.com/feature"
+	"tailscale.com/internal/client/tailscale"
+	"tailscale.com/ipn"
+	"tailscale.com/wif"
+)
+
+func init() {
+	feature.Register("identityfederation")
+	tailscale.HookResolveAuthKeyViaWIF.Set(resolveAuthKey)
+	tailscale.HookExchangeJWTForTokenViaWIF.Set(exchangeJWTForToken)
+}
+
+// resolveAuthKey uses OIDC identity federation to exchange the provided ID token and client ID for an authkey.
+func resolveAuthKey(ctx context.Context, baseURL, clientID, idToken, audience string, tags []string) (string, error) {
+	if clientID == "" {
+		return "", nil // Short-circuit, no client ID means not using identity federation
+	}
+
+	if idToken == "" {
+		if audience == "" {
+			return "", errors.New("federated identity requires either an ID token or an audience")
+		}
+		providerIdToken, err := wif.ObtainProviderToken(ctx, audience)
+		if err != nil {
+			return "", errors.New("federated identity authkeys require --id-token")
+		}
+		idToken = providerIdToken
+	}
+	if len(tags) == 0 {
+		return "", errors.New("federated identity authkeys require --advertise-tags")
+	}
+	if baseURL == "" {
+		baseURL = ipn.DefaultControlURL
+	}
+
+	strippedID, ephemeral, preauth, err := parseOptionalAttributes(clientID)
+	if err != nil {
+		return "", fmt.Errorf("failed to parse optional config attributes: %w", err)
+	}
+
+	accessToken, err := exchangeJWTForToken(ctx, baseURL, strippedID, idToken)
+	if err != nil {
+		return "", fmt.Errorf("failed to exchange JWT for access token: %w", err)
+	}
+	if accessToken == "" {
+		return "", errors.New("received empty access token from Tailscale")
+	}
+
+	tsClient := tailscale.NewClient("-", tailscale.APIKey(accessToken))
+	tsClient.UserAgent = "tailscale-cli-identity-federation"
+	tsClient.BaseURL = baseURL
+
+	authkey, _, err := tsClient.CreateKey(ctx, tailscale.KeyCapabilities{
+		Devices: tailscale.KeyDeviceCapabilities{
+			Create: tailscale.KeyDeviceCreateCapabilities{
+				Reusable:      false,
+				Ephemeral:     ephemeral,
+				Preauthorized: preauth,
+				Tags:          tags,
+			},
+		},
+	})
+	if err != nil {
+		return "", fmt.Errorf("unexpected error while creating authkey: %w", err)
+	}
+	if authkey == "" {
+		return "", errors.New("received empty authkey from control server")
+	}
+
+	return authkey, nil
+}
+
+func parseOptionalAttributes(clientID string) (strippedID string, ephemeral bool, preauthorized bool, err error) {
+	strippedID, attrs, found := strings.Cut(clientID, "?")
+	if !found {
+		return clientID, true, false, nil
+	}
+
+	parsed, err := url.ParseQuery(attrs)
+	if err != nil {
+		return "", false, false, fmt.Errorf("failed to parse optional config attributes: %w", err)
+	}
+
+	for k := range parsed {
+		switch k {
+		case "ephemeral":
+			ephemeral, err = strconv.ParseBool(parsed.Get(k))
+		case "preauthorized":
+			preauthorized, err = strconv.ParseBool(parsed.Get(k))
+		default:
+			return "", false, false, fmt.Errorf("unknown optional config attribute %q", k)
+		}
+	}
+	if err != nil {
+		return "", false, false, err
+	}
+
+	return strippedID, ephemeral, preauthorized, nil
+}
+
+// exchangeJWTForToken exchanges a JWT for a Tailscale access token.
+func exchangeJWTForToken(ctx context.Context, baseURL, clientID, idToken string) (string, error) {
+	httpClient := &http.Client{Timeout: 10 * time.Second}
+	ctx = context.WithValue(ctx, oauth2.HTTPClient, httpClient)
+
+	token, err := (&oauth2.Config{
+		Endpoint: oauth2.Endpoint{
+			TokenURL: fmt.Sprintf("%s/api/v2/oauth/token-exchange", baseURL),
+		},
+	}).Exchange(ctx, "", oauth2.SetAuthURLParam("client_id", clientID), oauth2.SetAuthURLParam("jwt", idToken))
+	if err != nil {
+		// Try to extract more detailed error message
+		var retrieveErr *oauth2.RetrieveError
+		if errors.As(err, &retrieveErr) {
+			return "", fmt.Errorf("token exchange failed with status %d: %s", retrieveErr.Response.StatusCode, string(retrieveErr.Body))
+		}
+		return "", fmt.Errorf("unexpected token exchange request error: %w", err)
+	}
+
+	return token.AccessToken, nil
+}