refactor auth interface to return error when verify failure (#22119)

This PR changed the Auth interface signature from 
`Verify(http *http.Request, w http.ResponseWriter, store DataStore, sess
SessionStore) *user_model.User`
to 
`Verify(http *http.Request, w http.ResponseWriter, store DataStore, sess
SessionStore) (*user_model.User, error)`.

There is a new return argument `error` which means the verification
condition matched but verify process failed, we should stop the auth
process.

Before this PR, when return a `nil` user, we don't know the reason why
it returned `nil`. If the match condition is not satisfied or it
verified failure? For these two different results, we should have
different handler. If the match condition is not satisfied, we should
try next auth method and if there is no more auth method, it's an
anonymous user. If the condition matched but verify failed, the auth
process should be stop and return immediately.

This will fix #20563

Co-authored-by: KN4CK3R <admin@oldschoolhack.me>
Co-authored-by: Jason Song <i@wolfogre.com>

8 files changed, 57 insertions, 58 deletions

diff --git a/services/auth/basic.go b/services/auth/basic.go
index 839aaa7a4e..5fb80703ab 100644
--- a/services/auth/basic.go
+++ b/services/auth/basic.go
@@ -40,20 +40,20 @@ func (b *Basic) Name() string {
 // "Authorization" header of the request and returns the corresponding user object for that
 // name/token on successful validation.
 // Returns nil if header is empty or validation fails.
-func (b *Basic) Verify(req *http.Request, w http.ResponseWriter, store DataStore, sess SessionStore) *user_model.User {
+func (b *Basic) Verify(req *http.Request, w http.ResponseWriter, store DataStore, sess SessionStore) (*user_model.User, error) {
 	// Basic authentication should only fire on API, Download or on Git or LFSPaths
 	if !middleware.IsAPIPath(req) && !isContainerPath(req) && !isAttachmentDownload(req) && !isGitRawReleaseOrLFSPath(req) {
-		return nil
+		return nil, nil
 	}
 
 	baHead := req.Header.Get("Authorization")
 	if len(baHead) == 0 {
-		return nil
+		return nil, nil
 	}
 
 	auths := strings.SplitN(baHead, " ", 2)
 	if len(auths) != 2 || (strings.ToLower(auths[0]) != "basic") {
-		return nil
+		return nil, nil
 	}
 
 	uname, passwd, _ := base.BasicAuthDecode(auths[1])
@@ -77,11 +77,11 @@ func (b *Basic) Verify(req *http.Request, w http.ResponseWriter, store DataStore
 		u, err := user_model.GetUserByID(req.Context(), uid)
 		if err != nil {
 			log.Error("GetUserByID:  %v", err)
-			return nil
+			return nil, err
 		}
 
 		store.GetData()["IsApiToken"] = true
-		return u
+		return u, nil
 	}
 
 	token, err := auth_model.GetAccessTokenBySHA(authToken)
@@ -90,7 +90,7 @@ func (b *Basic) Verify(req *http.Request, w http.ResponseWriter, store DataStore
 		u, err := user_model.GetUserByID(req.Context(), token.UID)
 		if err != nil {
 			log.Error("GetUserByID:  %v", err)
-			return nil
+			return nil, err
 		}
 
 		token.UpdatedUnix = timeutil.TimeStampNow()
@@ -99,13 +99,13 @@ func (b *Basic) Verify(req *http.Request, w http.ResponseWriter, store DataStore
 		}
 
 		store.GetData()["IsApiToken"] = true
-		return u
+		return u, nil
 	} else if !auth_model.IsErrAccessTokenNotExist(err) && !auth_model.IsErrAccessTokenEmpty(err) {
 		log.Error("GetAccessTokenBySha: %v", err)
 	}
 
 	if !setting.Service.EnableBasicAuth {
-		return nil
+		return nil, nil
 	}
 
 	log.Trace("Basic Authorization: Attempting SignIn for %s", uname)
@@ -114,7 +114,7 @@ func (b *Basic) Verify(req *http.Request, w http.ResponseWriter, store DataStore
 		if !user_model.IsErrUserNotExist(err) {
 			log.Error("UserSignIn: %v", err)
 		}
-		return nil
+		return nil, err
 	}
 
 	if skipper, ok := source.Cfg.(LocalTwoFASkipper); ok && skipper.IsSkipLocalTwoFA() {
@@ -123,5 +123,5 @@ func (b *Basic) Verify(req *http.Request, w http.ResponseWriter, store DataStore
 
 	log.Trace("Basic Authorization: Logged in user %-v", u)
 
-	return u
+	return u, nil
 }
diff --git a/services/auth/group.go b/services/auth/group.go
index a9112029c5..0a0330b3aa 100644
--- a/services/auth/group.go
+++ b/services/auth/group.go
@@ -9,7 +9,6 @@ import (
 	"reflect"
 	"strings"
 
-	"code.gitea.io/gitea/models/db"
 	user_model "code.gitea.io/gitea/models/user"
 )
 
@@ -80,23 +79,23 @@ func (b *Group) Free() error {
 }
 
 // Verify extracts and validates
-func (b *Group) Verify(req *http.Request, w http.ResponseWriter, store DataStore, sess SessionStore) *user_model.User {
-	if !db.HasEngine {
-		return nil
-	}
-
+func (b *Group) Verify(req *http.Request, w http.ResponseWriter, store DataStore, sess SessionStore) (*user_model.User, error) {
 	// Try to sign in with each of the enabled plugins
 	for _, ssoMethod := range b.methods {
-		user := ssoMethod.Verify(req, w, store, sess)
+		user, err := ssoMethod.Verify(req, w, store, sess)
+		if err != nil {
+			return nil, err
+		}
+
 		if user != nil {
 			if store.GetData()["AuthedMethod"] == nil {
 				if named, ok := ssoMethod.(Named); ok {
 					store.GetData()["AuthedMethod"] = named.Name()
 				}
 			}
-			return user
+			return user, nil
 		}
 	}
 
-	return nil
+	return nil, nil
 }
diff --git a/services/auth/httpsign.go b/services/auth/httpsign.go
index e73db4f248..4d52315381 100644
--- a/services/auth/httpsign.go
+++ b/services/auth/httpsign.go
@@ -39,10 +39,10 @@ func (h *HTTPSign) Name() string {
 // Verify extracts and validates HTTPsign from the Signature header of the request and returns
 // the corresponding user object on successful validation.
 // Returns nil if header is empty or validation fails.
-func (h *HTTPSign) Verify(req *http.Request, w http.ResponseWriter, store DataStore, sess SessionStore) *user_model.User {
+func (h *HTTPSign) Verify(req *http.Request, w http.ResponseWriter, store DataStore, sess SessionStore) (*user_model.User, error) {
 	sigHead := req.Header.Get("Signature")
 	if len(sigHead) == 0 {
-		return nil
+		return nil, nil
 	}
 
 	var (
@@ -53,14 +53,14 @@ func (h *HTTPSign) Verify(req *http.Request, w http.ResponseWriter, store DataSt
 	if len(req.Header.Get("X-Ssh-Certificate")) != 0 {
 		// Handle Signature signed by SSH certificates
 		if len(setting.SSH.TrustedUserCAKeys) == 0 {
-			return nil
+			return nil, nil
 		}
 
 		publicKey, err = VerifyCert(req)
 		if err != nil {
 			log.Debug("VerifyCert on request from %s: failed: %v", req.RemoteAddr, err)
 			log.Warn("Failed authentication attempt from %s", req.RemoteAddr)
-			return nil
+			return nil, nil
 		}
 	} else {
 		// Handle Signature signed by Public Key
@@ -68,21 +68,21 @@ func (h *HTTPSign) Verify(req *http.Request, w http.ResponseWriter, store DataSt
 		if err != nil {
 			log.Debug("VerifyPubKey on request from %s: failed: %v", req.RemoteAddr, err)
 			log.Warn("Failed authentication attempt from %s", req.RemoteAddr)
-			return nil
+			return nil, nil
 		}
 	}
 
 	u, err := user_model.GetUserByID(req.Context(), publicKey.OwnerID)
 	if err != nil {
 		log.Error("GetUserByID:  %v", err)
-		return nil
+		return nil, err
 	}
 
 	store.GetData()["IsApiToken"] = true
 
 	log.Trace("HTTP Sign: Logged in user %-v", u)
 
-	return u
+	return u, nil
 }
 
 func VerifyPubKey(r *http.Request) (*asymkey_model.PublicKey, error) {
diff --git a/services/auth/interface.go b/services/auth/interface.go
index d238a40856..f2f1aaf39c 100644
--- a/services/auth/interface.go
+++ b/services/auth/interface.go
@@ -24,8 +24,9 @@ type Method interface {
 	// If verification is successful returns either an existing user object (with id > 0)
 	// or a new user object (with id = 0) populated with the information that was found
 	// in the authentication data (username or email).
-	// Returns nil if verification fails.
-	Verify(http *http.Request, w http.ResponseWriter, store DataStore, sess SessionStore) *user_model.User
+	// Second argument returns err if verification fails, otherwise
+	// First return argument returns nil if no matched verification condition
+	Verify(http *http.Request, w http.ResponseWriter, store DataStore, sess SessionStore) (*user_model.User, error)
 }
 
 // Initializable represents a structure that requires initialization
diff --git a/services/auth/oauth2.go b/services/auth/oauth2.go
index 7aea3eadf3..c0a8250e95 100644
--- a/services/auth/oauth2.go
+++ b/services/auth/oauth2.go
@@ -108,18 +108,14 @@ func (o *OAuth2) userIDFromToken(req *http.Request, store DataStore) int64 {
 // or the "Authorization" header and returns the corresponding user object for that ID.
 // If verification is successful returns an existing user object.
 // Returns nil if verification fails.
-func (o *OAuth2) Verify(req *http.Request, w http.ResponseWriter, store DataStore, sess SessionStore) *user_model.User {
-	if !db.HasEngine {
-		return nil
-	}
-
+func (o *OAuth2) Verify(req *http.Request, w http.ResponseWriter, store DataStore, sess SessionStore) (*user_model.User, error) {
 	if !middleware.IsAPIPath(req) && !isAttachmentDownload(req) && !isAuthenticatedTokenRequest(req) {
-		return nil
+		return nil, nil
 	}
 
 	id := o.userIDFromToken(req, store)
 	if id <= 0 {
-		return nil
+		return nil, nil
 	}
 	log.Trace("OAuth2 Authorization: Found token for user[%d]", id)
 
@@ -128,11 +124,11 @@ func (o *OAuth2) Verify(req *http.Request, w http.ResponseWriter, store DataStor
 		if !user_model.IsErrUserNotExist(err) {
 			log.Error("GetUserByName: %v", err)
 		}
-		return nil
+		return nil, err
 	}
 
 	log.Trace("OAuth2 Authorization: Logged in user %-v", user)
-	return user
+	return user, nil
 }
 
 func isAuthenticatedTokenRequest(req *http.Request) bool {
diff --git a/services/auth/reverseproxy.go b/services/auth/reverseproxy.go
index 2d5b6611b5..0206ccdf66 100644
--- a/services/auth/reverseproxy.go
+++ b/services/auth/reverseproxy.go
@@ -51,10 +51,10 @@ func (r *ReverseProxy) Name() string {
 // If a username is available in the "setting.ReverseProxyAuthUser" header an existing
 // user object is returned (populated with username or email found in header).
 // Returns nil if header is empty.
-func (r *ReverseProxy) getUserFromAuthUser(req *http.Request) *user_model.User {
+func (r *ReverseProxy) getUserFromAuthUser(req *http.Request) (*user_model.User, error) {
 	username := r.getUserName(req)
 	if len(username) == 0 {
-		return nil
+		return nil, nil
 	}
 	log.Trace("ReverseProxy Authorization: Found username: %s", username)
 
@@ -62,11 +62,11 @@ func (r *ReverseProxy) getUserFromAuthUser(req *http.Request) *user_model.User {
 	if err != nil {
 		if !user_model.IsErrUserNotExist(err) || !r.isAutoRegisterAllowed() {
 			log.Error("GetUserByName: %v", err)
-			return nil
+			return nil, err
 		}
 		user = r.newUser(req)
 	}
-	return user
+	return user, nil
 }
 
 // getEmail extracts the email from the "setting.ReverseProxyAuthEmail" header
@@ -106,12 +106,15 @@ func (r *ReverseProxy) getUserFromAuthEmail(req *http.Request) *user_model.User
 // First it will attempt to load it based on the username (see docs for getUserFromAuthUser),
 // and failing that it will attempt to load it based on the email (see docs for getUserFromAuthEmail).
 // Returns nil if the headers are empty or the user is not found.
-func (r *ReverseProxy) Verify(req *http.Request, w http.ResponseWriter, store DataStore, sess SessionStore) *user_model.User {
-	user := r.getUserFromAuthUser(req)
+func (r *ReverseProxy) Verify(req *http.Request, w http.ResponseWriter, store DataStore, sess SessionStore) (*user_model.User, error) {
+	user, err := r.getUserFromAuthUser(req)
+	if err != nil {
+		return nil, err
+	}
 	if user == nil {
 		user = r.getUserFromAuthEmail(req)
 		if user == nil {
-			return nil
+			return nil, nil
 		}
 	}
 
@@ -124,7 +127,7 @@ func (r *ReverseProxy) Verify(req *http.Request, w http.ResponseWriter, store Da
 	store.GetData()["IsReverseProxy"] = true
 
 	log.Trace("ReverseProxy Authorization: Logged in user %-v", user)
-	return user
+	return user, nil
 }
 
 // isAutoRegisterAllowed checks if EnableReverseProxyAutoRegister setting is true
diff --git a/services/auth/session.go b/services/auth/session.go
index ef2c35d58a..c751135738 100644
--- a/services/auth/session.go
+++ b/services/auth/session.go
@@ -29,12 +29,12 @@ func (s *Session) Name() string {
 // Verify checks if there is a user uid stored in the session and returns the user
 // object for that uid.
 // Returns nil if there is no user uid stored in the session.
-func (s *Session) Verify(req *http.Request, w http.ResponseWriter, store DataStore, sess SessionStore) *user_model.User {
+func (s *Session) Verify(req *http.Request, w http.ResponseWriter, store DataStore, sess SessionStore) (*user_model.User, error) {
 	user := SessionUser(sess)
 	if user != nil {
-		return user
+		return user, nil
 	}
-	return nil
+	return nil, nil
 }
 
 // SessionUser returns the user object corresponding to the "uid" session variable.
diff --git a/services/auth/sspi_windows.go b/services/auth/sspi_windows.go
index 988afb4730..045834b691 100644
--- a/services/auth/sspi_windows.go
+++ b/services/auth/sspi_windows.go
@@ -77,15 +77,15 @@ func (s *SSPI) Free() error {
 // If authentication is successful, returns the corresponding user object.
 // If negotiation should continue or authentication fails, immediately returns a 401 HTTP
 // response code, as required by the SPNEGO protocol.
-func (s *SSPI) Verify(req *http.Request, w http.ResponseWriter, store DataStore, sess SessionStore) *user_model.User {
+func (s *SSPI) Verify(req *http.Request, w http.ResponseWriter, store DataStore, sess SessionStore) (*user_model.User, error) {
 	if !s.shouldAuthenticate(req) {
-		return nil
+		return nil, nil
 	}
 
 	cfg, err := s.getConfig()
 	if err != nil {
 		log.Error("could not get SSPI config: %v", err)
-		return nil
+		return nil, err
 	}
 
 	log.Trace("SSPI Authorization: Attempting to authenticate")
@@ -108,7 +108,7 @@ func (s *SSPI) Verify(req *http.Request, w http.ResponseWriter, store DataStore,
 			log.Error("%v", err)
 		}
 
-		return nil
+		return nil, err
 	}
 	if outToken != "" {
 		sspiAuth.AppendAuthenticateHeader(w, outToken)
@@ -116,7 +116,7 @@ func (s *SSPI) Verify(req *http.Request, w http.ResponseWriter, store DataStore,
 
 	username := sanitizeUsername(userInfo.Username, cfg)
 	if len(username) == 0 {
-		return nil
+		return nil, nil
 	}
 	log.Info("Authenticated as %s\n", username)
 
@@ -124,16 +124,16 @@ func (s *SSPI) Verify(req *http.Request, w http.ResponseWriter, store DataStore,
 	if err != nil {
 		if !user_model.IsErrUserNotExist(err) {
 			log.Error("GetUserByName: %v", err)
-			return nil
+			return nil, err
 		}
 		if !cfg.AutoCreateUsers {
 			log.Error("User '%s' not found", username)
-			return nil
+			return nil, nil
 		}
 		user, err = s.newUser(username, cfg)
 		if err != nil {
 			log.Error("CreateUser: %v", err)
-			return nil
+			return nil, err
 		}
 	}
 
@@ -143,7 +143,7 @@ func (s *SSPI) Verify(req *http.Request, w http.ResponseWriter, store DataStore,
 	}
 
 	log.Trace("SSPI Authorization: Logged in user %-v", user)
-	return user
+	return user, nil
 }
 
 // getConfig retrieves the SSPI configuration from login sources