Add artifacts v4 jwt to job message and accept it (#28885)

This change allows act_runner / actions_runner to use jwt tokens for
`ACTIONS_RUNTIME_TOKEN` that are compatible with
actions/upload-artifact@v4.

The official Artifact actions are now validating and extracting the jwt
claim scp to get the runid and jobid, the old artifact backend also
needs to accept the same token jwt.

---
Related to #28853

I'm not familar with the auth system, maybe you know how to improve this

I have tested
- the jwt token is a valid token for artifact uploading
- the jwt token can be parsed by actions/upload-artifact@v4 and passes
their scp claim validation

Next steps would be a new artifacts@v4 backend.

~~I'm linking the act_runner change soonish.~~
act_runner change to make the change effective and use jwt tokens
<https://gitea.com/gitea/act_runner/pulls/471>

routers/api/actions/artifacts.go

@@ -78,6 +78,7 @@ import (
 	"code.gitea.io/gitea/modules/util"
 	"code.gitea.io/gitea/modules/web"
 	web_types "code.gitea.io/gitea/modules/web/types"
+	actions_service "code.gitea.io/gitea/services/actions"
 )
 
 const artifactRouteBase = "/_apis/pipelines/workflows/{run_id}/artifacts"
@@ -137,13 +138,34 @@ func ArtifactContexter() func(next http.Handler) http.Handler {
 				return
 			}
 
+			// New act_runner uses jwt to authenticate
+			tID, err := actions_service.ParseAuthorizationToken(req)
+
+			var task *actions.ActionTask
+			if err == nil {
+
+				task, err = actions.GetTaskByID(req.Context(), tID)
+				if err != nil {
+					log.Error("Error runner api getting task by ID: %v", err)
+					ctx.Error(http.StatusInternalServerError, "Error runner api getting task by ID")
+					return
+				}
+				if task.Status != actions.StatusRunning {
+					log.Error("Error runner api getting task: task is not running")
+					ctx.Error(http.StatusInternalServerError, "Error runner api getting task: task is not running")
+					return
+				}
+			} else {
+				// Old act_runner uses GITEA_TOKEN to authenticate
 				authToken := strings.TrimPrefix(authHeader, "Bearer ")
-			task, err := actions.GetRunningTaskByToken(req.Context(), authToken)
+
+				task, err = actions.GetRunningTaskByToken(req.Context(), authToken)
 				if err != nil {
 					log.Error("Error runner api getting task: %v", err)
 					ctx.Error(http.StatusInternalServerError, "Error runner api getting task")
 					return
 				}
+			}
 
 			if err := task.LoadJob(req.Context()); err != nil {
 				log.Error("Error runner api getting job: %v", err)

routers/api/actions/runner/utils.go

@@ -151,6 +151,11 @@ func generateTaskContext(t *actions_model.ActionTask) *structpb.Struct {
 
 	refName := git.RefName(ref)
 
+	giteaRuntimeToken, err := actions.CreateAuthorizationToken(t.ID, t.Job.RunID, t.JobID)
+	if err != nil {
+		log.Error("actions.CreateAuthorizationToken failed: %v", err)
+	}
+
 	taskContext, err := structpb.NewStruct(map[string]any{
 		// standard contexts, see https://docs.github.com/en/actions/learn-github-actions/contexts#github-context
 		"action":            "",                                                   // string, The name of the action currently running, or the id of a step. GitHub removes special characters, and uses the name __run when the current step runs a script without an id. If you use the same action more than once in the same job, the name will include a suffix with the sequence number with underscore before it. For example, the first script you run will have the name __run, and the second script will be named __run_2. Similarly, the second invocation of actions/checkout will be actionscheckout2.
@@ -190,6 +195,7 @@ func generateTaskContext(t *actions_model.ActionTask) *structpb.Struct {
 
 		// additional contexts
 		"gitea_default_actions_url": setting.Actions.DefaultActionsURL.URL(),
+		"gitea_runtime_token":       giteaRuntimeToken,
 	})
 	if err != nil {
 		log.Error("structpb.NewStruct failed: %v", err)

services/actions/auth.go

@@ -0,0 +1,77 @@
+// Copyright 2024 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package actions
+
+import (
+	"fmt"
+	"net/http"
+	"strings"
+	"time"
+
+	"code.gitea.io/gitea/modules/log"
+	"code.gitea.io/gitea/modules/setting"
+
+	"github.com/golang-jwt/jwt/v5"
+)
+
+type actionsClaims struct {
+	jwt.RegisteredClaims
+	Scp    string `json:"scp"`
+	TaskID int64
+	RunID  int64
+	JobID  int64
+}
+
+func CreateAuthorizationToken(taskID, runID, jobID int64) (string, error) {
+	now := time.Now()
+
+	claims := actionsClaims{
+		RegisteredClaims: jwt.RegisteredClaims{
+			ExpiresAt: jwt.NewNumericDate(now.Add(24 * time.Hour)),
+			NotBefore: jwt.NewNumericDate(now),
+		},
+		Scp:    fmt.Sprintf("Actions.Results:%d:%d", runID, jobID),
+		TaskID: taskID,
+		RunID:  runID,
+		JobID:  jobID,
+	}
+	token := jwt.NewWithClaims(jwt.SigningMethodHS256, claims)
+
+	tokenString, err := token.SignedString([]byte(setting.SecretKey))
+	if err != nil {
+		return "", err
+	}
+
+	return tokenString, nil
+}
+
+func ParseAuthorizationToken(req *http.Request) (int64, error) {
+	h := req.Header.Get("Authorization")
+	if h == "" {
+		return 0, nil
+	}
+
+	parts := strings.SplitN(h, " ", 2)
+	if len(parts) != 2 {
+		log.Error("split token failed: %s", h)
+		return 0, fmt.Errorf("split token failed")
+	}
+
+	token, err := jwt.ParseWithClaims(parts[1], &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"])
+		}
+		return []byte(setting.SecretKey), nil
+	})
+	if err != nil {
+		return 0, err
+	}
+
+	c, ok := token.Claims.(*actionsClaims)
+	if !token.Valid || !ok {
+		return 0, fmt.Errorf("invalid token claim")
+	}
+
+	return c.TaskID, nil
+}

services/actions/auth_test.go

@@ -0,0 +1,55 @@
+// Copyright 2024 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package actions
+
+import (
+	"net/http"
+	"testing"
+
+	"code.gitea.io/gitea/modules/setting"
+
+	"github.com/golang-jwt/jwt/v5"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestCreateAuthorizationToken(t *testing.T) {
+	var taskID int64 = 23
+	token, err := CreateAuthorizationToken(taskID, 1, 2)
+	assert.Nil(t, err)
+	assert.NotEqual(t, "", token)
+	claims := jwt.MapClaims{}
+	_, err = jwt.ParseWithClaims(token, claims, func(t *jwt.Token) (interface{}, error) {
+		return []byte(setting.SecretKey), nil
+	})
+	assert.Nil(t, err)
+	scp, ok := claims["scp"]
+	assert.True(t, ok, "Has scp claim in jwt token")
+	assert.Contains(t, scp, "Actions.Results:1:2")
+	taskIDClaim, ok := claims["TaskID"]
+	assert.True(t, ok, "Has TaskID claim in jwt token")
+	assert.Equal(t, float64(taskID), taskIDClaim, "Supplied taskid must match stored one")
+}
+
+func TestParseAuthorizationToken(t *testing.T) {
+	var taskID int64 = 23
+	token, err := CreateAuthorizationToken(taskID, 1, 2)
+	assert.Nil(t, err)
+	assert.NotEqual(t, "", token)
+	headers := http.Header{}
+	headers.Set("Authorization", "Bearer "+token)
+	rTaskID, err := ParseAuthorizationToken(&http.Request{
+		Header: headers,
+	})
+	assert.Nil(t, err)
+	assert.Equal(t, taskID, rTaskID)
+}
+
+func TestParseAuthorizationTokenNoAuthHeader(t *testing.T) {
+	headers := http.Header{}
+	rTaskID, err := ParseAuthorizationToken(&http.Request{
+		Header: headers,
+	})
+	assert.Nil(t, err)
+	assert.Equal(t, int64(0), rTaskID)
+}