Fix wrong user in OpenID response (#16736)

* Fixed usage of wrong user.

* Added tests.

models/fixtures/oauth2_grant.yml

@@ -5,3 +5,19 @@
   scope: "openid profile"
   created_unix: 1546869730
   updated_unix: 1546869730
+
+- id: 2
+  user_id: 3
+  application_id: 1
+  counter: 1
+  scope: "openid"
+  created_unix: 1546869730
+  updated_unix: 1546869730
+
+- id: 3
+  user_id: 5
+  application_id: 1
+  counter: 1
+  scope: "openid profile email"
+  created_unix: 1546869730
+  updated_unix: 1546869730

routers/web/user/oauth.go

@@ -187,7 +187,7 @@ func newAccessTokenResponse(grant *models.OAuth2Grant, signingKey oauth2.JWTSign
 				ErrorDescription: "cannot find application",
 			}
 		}
-		err = app.LoadUser()
+		user, err := models.GetUserByID(grant.UserID)
 		if err != nil {
 			if models.IsErrUserNotExist(err) {
 				return nil, &AccessTokenError{
@@ -212,17 +212,17 @@ func newAccessTokenResponse(grant *models.OAuth2Grant, signingKey oauth2.JWTSign
 			Nonce: grant.Nonce,
 		}
 		if grant.ScopeContains("profile") {
-			idToken.Name = app.User.FullName
-			idToken.PreferredUsername = app.User.Name
-			idToken.Profile = app.User.HTMLURL()
-			idToken.Picture = app.User.AvatarLink()
-			idToken.Website = app.User.Website
-			idToken.Locale = app.User.Language
-			idToken.UpdatedAt = app.User.UpdatedUnix
+			idToken.Name = user.FullName
+			idToken.PreferredUsername = user.Name
+			idToken.Profile = user.HTMLURL()
+			idToken.Picture = user.AvatarLink()
+			idToken.Website = user.Website
+			idToken.Locale = user.Language
+			idToken.UpdatedAt = user.UpdatedUnix
 		}
 		if grant.ScopeContains("email") {
-			idToken.Email = app.User.Email
-			idToken.EmailVerified = app.User.IsActive
+			idToken.Email = user.Email
+			idToken.EmailVerified = user.IsActive
 		}
 
 		signedIDToken, err = idToken.SignToken(signingKey)

routers/web/user/oauth_test.go

@@ -0,0 +1,75 @@
+// Copyright 2021 The Gitea Authors. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+package user
+
+import (
+	"testing"
+
+	"code.gitea.io/gitea/models"
+	"code.gitea.io/gitea/services/auth/source/oauth2"
+
+	"github.com/golang-jwt/jwt"
+	"github.com/stretchr/testify/assert"
+)
+
+func createAndParseToken(t *testing.T, grant *models.OAuth2Grant) *oauth2.OIDCToken {
+	signingKey, err := oauth2.CreateJWTSingingKey("HS256", make([]byte, 32))
+	assert.NoError(t, err)
+	assert.NotNil(t, signingKey)
+	oauth2.DefaultSigningKey = signingKey
+
+	response, terr := newAccessTokenResponse(grant, signingKey)
+	assert.Nil(t, terr)
+	assert.NotNil(t, response)
+
+	parsedToken, err := jwt.ParseWithClaims(response.IDToken, &oauth2.OIDCToken{}, func(token *jwt.Token) (interface{}, error) {
+		assert.NotNil(t, token.Method)
+		assert.Equal(t, signingKey.SigningMethod().Alg(), token.Method.Alg())
+		return signingKey.VerifyKey(), nil
+	})
+	assert.NoError(t, err)
+	assert.True(t, parsedToken.Valid)
+
+	oidcToken, ok := parsedToken.Claims.(*oauth2.OIDCToken)
+	assert.True(t, ok)
+	assert.NotNil(t, oidcToken)
+
+	return oidcToken
+}
+
+func TestNewAccessTokenResponse_OIDCToken(t *testing.T) {
+	assert.NoError(t, models.PrepareTestDatabase())
+
+	grants, err := models.GetOAuth2GrantsByUserID(3)
+	assert.NoError(t, err)
+	assert.Len(t, grants, 1)
+
+	// Scopes: openid
+	oidcToken := createAndParseToken(t, grants[0])
+	assert.Empty(t, oidcToken.Name)
+	assert.Empty(t, oidcToken.PreferredUsername)
+	assert.Empty(t, oidcToken.Profile)
+	assert.Empty(t, oidcToken.Picture)
+	assert.Empty(t, oidcToken.Website)
+	assert.Empty(t, oidcToken.UpdatedAt)
+	assert.Empty(t, oidcToken.Email)
+	assert.False(t, oidcToken.EmailVerified)
+
+	user := models.AssertExistsAndLoadBean(t, &models.User{ID: 5}).(*models.User)
+	grants, err = models.GetOAuth2GrantsByUserID(user.ID)
+	assert.NoError(t, err)
+	assert.Len(t, grants, 1)
+
+	// Scopes: openid profile email
+	oidcToken = createAndParseToken(t, grants[0])
+	assert.Equal(t, user.FullName, oidcToken.Name)
+	assert.Equal(t, user.Name, oidcToken.PreferredUsername)
+	assert.Equal(t, user.HTMLURL(), oidcToken.Profile)
+	assert.Equal(t, user.AvatarLink(), oidcToken.Picture)
+	assert.Equal(t, user.Website, oidcToken.Website)
+	assert.Equal(t, user.UpdatedUnix, oidcToken.UpdatedAt)
+	assert.Equal(t, user.Email, oidcToken.Email)
+	assert.Equal(t, user.IsActive, oidcToken.EmailVerified)
+}