Fix http auth header parsing (#34936)

Using `strings.EqualFold` is wrong in many cases.

modules/auth/httpauth/httpauth.go

@@ -0,0 +1,47 @@
+// Copyright 2025 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package httpauth
+
+import (
+	"encoding/base64"
+	"strings"
+
+	"code.gitea.io/gitea/modules/util"
+)
+
+type BasicAuth struct {
+	Username, Password string
+}
+
+type BearerToken struct {
+	Token string
+}
+
+type ParsedAuthorizationHeader struct {
+	BasicAuth   *BasicAuth
+	BearerToken *BearerToken
+}
+
+func ParseAuthorizationHeader(header string) (ret ParsedAuthorizationHeader, _ bool) {
+	parts := strings.Fields(header)
+	if len(parts) != 2 {
+		return ret, false
+	}
+	if util.AsciiEqualFold(parts[0], "basic") {
+		s, err := base64.StdEncoding.DecodeString(parts[1])
+		if err != nil {
+			return ret, false
+		}
+		u, p, ok := strings.Cut(string(s), ":")
+		if !ok {
+			return ret, false
+		}
+		ret.BasicAuth = &BasicAuth{Username: u, Password: p}
+		return ret, true
+	} else if util.AsciiEqualFold(parts[0], "token") || util.AsciiEqualFold(parts[0], "bearer") {
+		ret.BearerToken = &BearerToken{Token: parts[1]}
+		return ret, true
+	}
+	return ret, false
+}

modules/auth/httpauth/httpauth_test.go

@@ -0,0 +1,43 @@
+// Copyright 2025 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package httpauth
+
+import (
+	"encoding/base64"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestParseAuthorizationHeader(t *testing.T) {
+	type parsed = ParsedAuthorizationHeader
+	type basic = BasicAuth
+	type bearer = BearerToken
+	cases := []struct {
+		headerValue string
+		expected    parsed
+		ok          bool
+	}{
+		{"", parsed{}, false},
+		{"?", parsed{}, false},
+		{"foo", parsed{}, false},
+		{"any value", parsed{}, false},
+
+		{"Basic ?", parsed{}, false},
+		{"Basic " + base64.StdEncoding.EncodeToString([]byte("foo")), parsed{}, false},
+		{"Basic " + base64.StdEncoding.EncodeToString([]byte("foo:bar")), parsed{BasicAuth: &basic{"foo", "bar"}}, true},
+		{"basic " + base64.StdEncoding.EncodeToString([]byte("foo:bar")), parsed{BasicAuth: &basic{"foo", "bar"}}, true},
+
+		{"token value", parsed{BearerToken: &bearer{"value"}}, true},
+		{"Token value", parsed{BearerToken: &bearer{"value"}}, true},
+		{"bearer value", parsed{BearerToken: &bearer{"value"}}, true},
+		{"Bearer value", parsed{BearerToken: &bearer{"value"}}, true},
+		{"Bearer wrong value", parsed{}, false},
+	}
+	for _, c := range cases {
+		ret, ok := ParseAuthorizationHeader(c.headerValue)
+		assert.Equal(t, c.ok, ok, "header %q", c.headerValue)
+		assert.Equal(t, c.expected, ret, "header %q", c.headerValue)
+	}
+}

modules/base/tool.go

@@ -8,13 +8,10 @@ import (
 	"crypto/sha1"
 	"crypto/sha256"
 	"crypto/subtle"
-	"encoding/base64"
 	"encoding/hex"
-	"errors"
 	"fmt"
 	"hash"
 	"strconv"
-	"strings"
 	"time"
 
 	"code.gitea.io/gitea/modules/setting"
@@ -36,19 +33,6 @@ func ShortSha(sha1 string) string {
 	return util.TruncateRunes(sha1, 10)
 }
 
-// BasicAuthDecode decode basic auth string
-func BasicAuthDecode(encoded string) (string, string, error) {
-	s, err := base64.StdEncoding.DecodeString(encoded)
-	if err != nil {
-		return "", "", err
-	}
-
-	if username, password, ok := strings.Cut(string(s), ":"); ok {
-		return username, password, nil
-	}
-	return "", "", errors.New("invalid basic authentication")
-}
-
 // VerifyTimeLimitCode verify time limit code
 func VerifyTimeLimitCode(now time.Time, data string, minutes int, code string) bool {
 	if len(code) <= 18 {

modules/base/tool_test.go

@@ -26,25 +26,6 @@ func TestShortSha(t *testing.T) {
 	assert.Equal(t, "veryverylo", ShortSha("veryverylong"))
 }
 
-func TestBasicAuthDecode(t *testing.T) {
-	_, _, err := BasicAuthDecode("?")
-	assert.Equal(t, "illegal base64 data at input byte 0", err.Error())
-
-	user, pass, err := BasicAuthDecode("Zm9vOmJhcg==")
-	assert.NoError(t, err)
-	assert.Equal(t, "foo", user)
-	assert.Equal(t, "bar", pass)
-
-	_, _, err = BasicAuthDecode("aW52YWxpZA==")
-	assert.Error(t, err)
-
-	_, _, err = BasicAuthDecode("invalid")
-	assert.Error(t, err)
-
-	_, _, err = BasicAuthDecode("YWxpY2U=") // "alice", no colon
-	assert.Error(t, err)
-}
-
 func TestVerifyTimeLimitCode(t *testing.T) {
 	defer test.MockVariableValue(&setting.InstallLock, true)()
 	initGeneralSecret := func(secret string) {

modules/util/string.go

@@ -110,3 +110,24 @@ func SplitTrimSpace(input, sep string) []string {
 	}
 	return stringList
 }
+
+func asciiLower(b byte) byte {
+	if 'A' <= b && b <= 'Z' {
+		return b + ('a' - 'A')
+	}
+	return b
+}
+
+// AsciiEqualFold is from Golang https://cs.opensource.google/go/go/+/refs/tags/go1.24.4:src/net/http/internal/ascii/print.go
+// ASCII only. In most cases for protocols, we should only use this but not [strings.EqualFold]
+func AsciiEqualFold(s, t string) bool { //nolint:revive // PascalCase
+	if len(s) != len(t) {
+		return false
+	}
+	for i := 0; i < len(s); i++ {
+		if asciiLower(s[i]) != asciiLower(t[i]) {
+			return false
+		}
+	}
+	return true
+}

routers/web/auth/oauth2_provider.go

@@ -4,18 +4,16 @@
 package auth
 
 import (
-	"errors"
 	"fmt"
 	"html"
 	"html/template"
 	"net/http"
 	"net/url"
 	"strconv"
-	"strings"
 
 	"code.gitea.io/gitea/models/auth"
 	user_model "code.gitea.io/gitea/models/user"
-	"code.gitea.io/gitea/modules/base"
+	"code.gitea.io/gitea/modules/auth/httpauth"
 	"code.gitea.io/gitea/modules/json"
 	"code.gitea.io/gitea/modules/log"
 	"code.gitea.io/gitea/modules/setting"
@@ -108,9 +106,8 @@ func InfoOAuth(ctx *context.Context) {
 
 	var accessTokenScope auth.AccessTokenScope
 	if auHead := ctx.Req.Header.Get("Authorization"); auHead != "" {
-		auths := strings.Fields(auHead)
-		if len(auths) == 2 && (auths[0] == "token" || strings.ToLower(auths[0]) == "bearer") {
-			accessTokenScope, _ = auth_service.GetOAuthAccessTokenScopeAndUserID(ctx, auths[1])
+		if parsed, ok := httpauth.ParseAuthorizationHeader(auHead); ok && parsed.BearerToken != nil {
+			accessTokenScope, _ = auth_service.GetOAuthAccessTokenScopeAndUserID(ctx, parsed.BearerToken.Token)
 		}
 	}
 
@@ -127,18 +124,12 @@ func InfoOAuth(ctx *context.Context) {
 	ctx.JSON(http.StatusOK, response)
 }
 
-func parseBasicAuth(ctx *context.Context) (username, password string, err error) {
-	authHeader := ctx.Req.Header.Get("Authorization")
-	if authType, authData, ok := strings.Cut(authHeader, " "); ok && strings.EqualFold(authType, "Basic") {
-		return base.BasicAuthDecode(authData)
-	}
-	return "", "", errors.New("invalid basic authentication")
-}
-
 // IntrospectOAuth introspects an oauth token
 func IntrospectOAuth(ctx *context.Context) {
 	clientIDValid := false
-	if clientID, clientSecret, err := parseBasicAuth(ctx); err == nil {
+	authHeader := ctx.Req.Header.Get("Authorization")
+	if parsed, ok := httpauth.ParseAuthorizationHeader(authHeader); ok && parsed.BasicAuth != nil {
+		clientID, clientSecret := parsed.BasicAuth.Username, parsed.BasicAuth.Password
 		app, err := auth.GetOAuth2ApplicationByClientID(ctx, clientID)
 		if err != nil && !auth.IsErrOauthClientIDInvalid(err) {
 			// this is likely a database error; log it and respond without details
@@ -465,16 +456,16 @@ func AccessTokenOAuth(ctx *context.Context) {
 	form := *web.GetForm(ctx).(*forms.AccessTokenForm)
 	// if there is no ClientID or ClientSecret in the request body, fill these fields by the Authorization header and ensure the provided field matches the Authorization header
 	if form.ClientID == "" || form.ClientSecret == "" {
-		authHeader := ctx.Req.Header.Get("Authorization")
-		if authType, authData, ok := strings.Cut(authHeader, " "); ok && strings.EqualFold(authType, "Basic") {
-			clientID, clientSecret, err := base.BasicAuthDecode(authData)
-			if err != nil {
+		if authHeader := ctx.Req.Header.Get("Authorization"); authHeader != "" {
+			parsed, ok := httpauth.ParseAuthorizationHeader(authHeader)
+			if !ok || parsed.BasicAuth == nil {
 				handleAccessTokenError(ctx, oauth2_provider.AccessTokenError{
 					ErrorCode:        oauth2_provider.AccessTokenErrorCodeInvalidRequest,
 					ErrorDescription: "cannot parse basic auth header",
 				})
 				return
 			}
+			clientID, clientSecret := parsed.BasicAuth.Username, parsed.BasicAuth.Password
 			// validate that any fields present in the form match the Basic auth header
 			if form.ClientID != "" && form.ClientID != clientID {
 				handleAccessTokenError(ctx, oauth2_provider.AccessTokenError{

services/auth/basic.go

@@ -7,12 +7,11 @@ package auth
 import (
 	"errors"
 	"net/http"
-	"strings"
 
 	actions_model "code.gitea.io/gitea/models/actions"
 	auth_model "code.gitea.io/gitea/models/auth"
 	user_model "code.gitea.io/gitea/models/user"
-	"code.gitea.io/gitea/modules/base"
+	"code.gitea.io/gitea/modules/auth/httpauth"
 	"code.gitea.io/gitea/modules/log"
 	"code.gitea.io/gitea/modules/setting"
 	"code.gitea.io/gitea/modules/timeutil"
@@ -54,17 +53,15 @@ func (b *Basic) Verify(req *http.Request, w http.ResponseWriter, store DataStore
 		return nil, nil
 	}
 
-	baHead := req.Header.Get("Authorization")
-	if len(baHead) == 0 {
+	authHeader := req.Header.Get("Authorization")
+	if authHeader == "" {
 		return nil, nil
 	}
-
-	auths := strings.SplitN(baHead, " ", 2)
-	if len(auths) != 2 || (strings.ToLower(auths[0]) != "basic") {
+	parsed, ok := httpauth.ParseAuthorizationHeader(authHeader)
+	if !ok || parsed.BasicAuth == nil {
 		return nil, nil
 	}
-
-	uname, passwd, _ := base.BasicAuthDecode(auths[1])
+	uname, passwd := parsed.BasicAuth.Username, parsed.BasicAuth.Password
 
 	// Check if username or password is a token
 	isUsernameToken := len(passwd) == 0 || passwd == "x-oauth-basic"

services/auth/oauth2.go

@@ -13,6 +13,7 @@ import (
 	actions_model "code.gitea.io/gitea/models/actions"
 	auth_model "code.gitea.io/gitea/models/auth"
 	user_model "code.gitea.io/gitea/models/user"
+	"code.gitea.io/gitea/modules/auth/httpauth"
 	"code.gitea.io/gitea/modules/log"
 	"code.gitea.io/gitea/modules/setting"
 	"code.gitea.io/gitea/modules/timeutil"
@@ -97,9 +98,9 @@ func parseToken(req *http.Request) (string, bool) {
 
 	// check header token
 	if auHead := req.Header.Get("Authorization"); auHead != "" {
-		auths := strings.Fields(auHead)
-		if len(auths) == 2 && (auths[0] == "token" || strings.ToLower(auths[0]) == "bearer") {
-			return auths[1], true
+		parsed, ok := httpauth.ParseAuthorizationHeader(auHead)
+		if ok && parsed.BearerToken != nil {
+			return parsed.BearerToken.Token, true
 		}
 	}
 	return "", false

services/lfs/server.go

@@ -27,6 +27,7 @@ import (
 	repo_model "code.gitea.io/gitea/models/repo"
 	"code.gitea.io/gitea/models/unit"
 	user_model "code.gitea.io/gitea/models/user"
+	"code.gitea.io/gitea/modules/auth/httpauth"
 	"code.gitea.io/gitea/modules/json"
 	lfs_module "code.gitea.io/gitea/modules/lfs"
 	"code.gitea.io/gitea/modules/log"
@@ -594,19 +595,11 @@ func parseToken(ctx stdCtx.Context, authorization string, target *repo_model.Rep
 	if authorization == "" {
 		return nil, errors.New("no token")
 	}
-
-	parts := strings.SplitN(authorization, " ", 2)
-	if len(parts) != 2 {
-		return nil, errors.New("no token")
-	}
-	tokenSHA := parts[1]
-	switch strings.ToLower(parts[0]) {
-	case "bearer":
-		fallthrough
-	case "token":
-		return handleLFSToken(ctx, tokenSHA, target, mode)
+	parsed, ok := httpauth.ParseAuthorizationHeader(authorization)
+	if !ok || parsed.BearerToken == nil {
+		return nil, errors.New("token not found")
 	}
-	return nil, errors.New("token not found")
+	return handleLFSToken(ctx, parsed.BearerToken.Token, target, mode)
 }
 
 func requireAuth(ctx *context.Context) {