allow the actions user to login via the jwt token (#32527)

We have some actions that leverage the Gitea API that began receiving
401 errors, with a message that the user was not found. These actions
use the `ACTIONS_RUNTIME_TOKEN` env var in the actions job to
authenticate with the Gitea API. The format of this env var in actions
jobs changed with go-gitea/gitea/pull/28885 to be a JWT (with a
corresponding update to `act_runner`) Since it was a JWT, the OAuth
parsing logic attempted to parse it as an OAuth token, and would return
user not found, instead of falling back to look up the running task and
assigning it to the actions user.

Make ACTIONS_RUNTIME_TOKEN in action runners could be used,
attempting to parse Oauth JWTs. The code to parse potential old
`ACTION_RUNTIME_TOKEN` was kept in case someone is running an older
version of act_runner that doesn't support the Actions JWT.

(cherry picked from commit 407b6e6dfc7ee9ebb8a16c7f1a786e4c24d0516e)

Conflicts:
	services/auth/oauth2.go
  trivial context conflicts because OAuth2 scopes are in Forgejo and
  not yet in Gitea

models/fixtures/action_task.yml

@@ -1,3 +1,22 @@
+-
+  id: 46
+  attempt: 3
+  runner_id: 1
+  status: 3 # 3 is the status code for "cancelled"
+  started: 1683636528
+  stopped: 1683636626
+  repo_id: 4
+  owner_id: 1
+  commit_sha: c2d72f548424103f01ee1dc02889c1e2bff816b0
+  is_fork_pull_request: 0
+  token_hash: 6d8ef48297195edcc8e22c70b3020eaa06c52976db67d39b4260c64a69a2cc1508825121b7b8394e48e00b1bf8718b2aaaaa
+  token_salt: eeeeeeee
+  token_last_eight: eeeeeeee
+  log_filename: artifact-test2/2f/47.log
+  log_in_storage: 1
+  log_length: 707
+  log_size: 90179
+  log_expired: 0
 -
   id: 47
   job_id: 192

services/actions/auth.go

@@ -83,7 +83,12 @@ func ParseAuthorizationToken(req *http.Request) (int64, error) {
 		return 0, fmt.Errorf("split token failed")
 	}
 
-	token, err := jwt.ParseWithClaims(parts[1], &actionsClaims{}, func(t *jwt.Token) (any, error) {
+	return TokenToTaskID(parts[1])
+}
+
+// TokenToTaskID returns the TaskID associated with the provided JWT token
+func TokenToTaskID(token string) (int64, error) {
+	parsedToken, err := jwt.ParseWithClaims(token, &actionsClaims{}, func(t *jwt.Token) (any, error) {
 		if _, ok := t.Method.(*jwt.SigningMethodHMAC); !ok {
 			return nil, fmt.Errorf("unexpected signing method: %v", t.Header["alg"])
 		}
@@ -93,8 +98,8 @@ func ParseAuthorizationToken(req *http.Request) (int64, error) {
 		return 0, err
 	}
 
-	c, ok := token.Claims.(*actionsClaims)
+	c, ok := parsedToken.Claims.(*actionsClaims)
-	if !token.Valid || !ok {
+	if !parsedToken.Valid || !ok {
 		return 0, fmt.Errorf("invalid token claim")
 	}
 

services/auth/oauth2.go

@@ -18,6 +18,7 @@ import (
 	"code.gitea.io/gitea/modules/setting"
 	"code.gitea.io/gitea/modules/timeutil"
 	"code.gitea.io/gitea/modules/web/middleware"
+	"code.gitea.io/gitea/services/actions"
 	"code.gitea.io/gitea/services/auth/source/oauth2"
 )
 
@@ -94,6 +95,18 @@ func CheckOAuthAccessToken(ctx context.Context, accessToken string) (int64, stri
 	return grant.UserID, grantScopes
 }
 
+// CheckTaskIsRunning verifies that the TaskID corresponds to a running task
+func CheckTaskIsRunning(ctx context.Context, taskID int64) bool {
+	// Verify the task exists
+	task, err := actions_model.GetTaskByID(ctx, taskID)
+	if err != nil {
+		return false
+	}
+
+	// Verify that it's running
+	return task.Status == actions_model.StatusRunning
+}
+
 // OAuth2 implements the Auth interface and authenticates requests
 // (API requests only) by looking for an OAuth token in query parameters or the
 // "Authorization" header.
@@ -137,8 +150,17 @@ func parseToken(req *http.Request) (string, bool) {
 func (o *OAuth2) userIDFromToken(ctx context.Context, tokenSHA string, store DataStore) int64 {
 	// Let's see if token is valid.
 	if strings.Contains(tokenSHA, ".") {
-		uid, grantScopes := CheckOAuthAccessToken(ctx, tokenSHA)
+		// First attempt to decode an actions JWT, returning the actions user
+		if taskID, err := actions.TokenToTaskID(tokenSHA); err == nil {
+			if CheckTaskIsRunning(ctx, taskID) {
+				store.GetData()["IsActionsToken"] = true
+				store.GetData()["ActionsTaskID"] = taskID
+				return user_model.ActionsUserID
+			}
+		}
 
+		// Otherwise, check if this is an OAuth access token
+		uid, grantScopes := CheckOAuthAccessToken(ctx, tokenSHA)
 		if uid != 0 {
 			store.GetData()["IsApiToken"] = true
 			if grantScopes != "" {

services/auth/oauth2_test.go

@@ -0,0 +1,55 @@
+// Copyright 2024 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package auth
+
+import (
+	"context"
+	"testing"
+
+	"code.gitea.io/gitea/models/unittest"
+	user_model "code.gitea.io/gitea/models/user"
+	"code.gitea.io/gitea/modules/web/middleware"
+	"code.gitea.io/gitea/services/actions"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestUserIDFromToken(t *testing.T) {
+	require.NoError(t, unittest.PrepareTestDatabase())
+
+	t.Run("Actions JWT", func(t *testing.T) {
+		const RunningTaskID = 47
+		token, err := actions.CreateAuthorizationToken(RunningTaskID, 1, 2)
+		require.NoError(t, err)
+
+		ds := make(middleware.ContextData)
+
+		o := OAuth2{}
+		uid := o.userIDFromToken(context.Background(), token, ds)
+		assert.Equal(t, int64(user_model.ActionsUserID), uid)
+		assert.Equal(t, true, ds["IsActionsToken"])
+		assert.Equal(t, ds["ActionsTaskID"], int64(RunningTaskID))
+	})
+}
+
+func TestCheckTaskIsRunning(t *testing.T) {
+	require.NoError(t, unittest.PrepareTestDatabase())
+	cases := map[string]struct {
+		TaskID   int64
+		Expected bool
+	}{
+		"Running":   {TaskID: 47, Expected: true},
+		"Missing":   {TaskID: 1, Expected: false},
+		"Cancelled": {TaskID: 46, Expected: false},
+	}
+
+	for name := range cases {
+		c := cases[name]
+		t.Run(name, func(t *testing.T) {
+			actual := CheckTaskIsRunning(context.Background(), c.TaskID)
+			assert.Equal(t, c.Expected, actual)
+		})
+	}
+}