Refactor internal routers (partial backport, auth token const time comparing) (#32473) (#32479)

Partially backport #32473. LFS related changes are not in 1.22, so skip
them.

1. Ignore non-existing repos during migrations
2. Improve ReadBatchLine's comment
3. Use `X-Gitea-Internal-Auth` header for internal API calls and make
the comparing constant time (it wasn't a serous problem because in a
real world it's nearly impossible to timing-attack the token, but indeed
security related and good to fix and backport)
4. Fix route mock nil check

Author: wxiaoguang

models/migrations/v1_21/v276.go

@@ -12,6 +12,7 @@ import (
 	"code.gitea.io/gitea/modules/git"
 	giturl "code.gitea.io/gitea/modules/git/url"
 	"code.gitea.io/gitea/modules/setting"
+	"code.gitea.io/gitea/modules/util"
 
 	"xorm.io/xorm"
 )
@@ -163,7 +164,9 @@ func migratePushMirrors(x *xorm.Engine) error {
 
 func getRemoteAddress(ownerName, repoName, remoteName string) (string, error) {
 	repoPath := filepath.Join(setting.RepoRootPath, strings.ToLower(ownerName), strings.ToLower(repoName)+".git")
-
+	if exist, _ := util.IsExist(repoPath); !exist {
+		return "", nil
+	}
 	remoteURL, err := git.GetRemoteAddress(context.Background(), repoPath, remoteName)
 	if err != nil {
 		return "", fmt.Errorf("get remote %s's address of %s/%s failed: %v", remoteName, ownerName, repoName, err)

modules/git/batch_reader.go

@@ -146,9 +146,8 @@ func catFileBatch(ctx context.Context, repoPath string) (WriteCloserError, *bufi
 }
 
 // ReadBatchLine reads the header line from cat-file --batch
-// We expect:
-// <sha> SP <type> SP <size> LF
-// sha is a hex encoded here
+// We expect: <oid> SP <type> SP <size> LF
+// then leaving the rest of the stream "<contents> LF" to be read
 func ReadBatchLine(rd *bufio.Reader) (sha []byte, typ string, size int64, err error) {
 	typ, err = rd.ReadString('\n')
 	if err != nil {

modules/private/internal.go

@@ -43,7 +43,7 @@ Ensure you are running in the correct environment or set the correct configurati
 	req := httplib.NewRequest(url, method).
 		SetContext(ctx).
 		Header("X-Real-IP", getClientIP()).
-		Header("Authorization", fmt.Sprintf("Bearer %s", setting.InternalToken)).
+		Header("X-Gitea-Internal-Auth", fmt.Sprintf("Bearer %s", setting.InternalToken)).
 		SetTLSClientConfig(&tls.Config{
 			InsecureSkipVerify: true,
 			ServerName:         setting.Domain,

modules/web/route.go

@@ -5,6 +5,7 @@ package web
 
 import (
 	"net/http"
+	"reflect"
 	"strings"
 
 	"code.gitea.io/gitea/modules/web/middleware"
@@ -80,15 +81,23 @@ func (r *Route) getPattern(pattern string) string {
 	return strings.TrimSuffix(newPattern, "/")
 }
 
+func isNilOrFuncNil(v any) bool {
+	if v == nil {
+		return true
+	}
+	r := reflect.ValueOf(v)
+	return r.Kind() == reflect.Func && r.IsNil()
+}
+
 func (r *Route) wrapMiddlewareAndHandler(h []any) ([]func(http.Handler) http.Handler, http.HandlerFunc) {
 	handlerProviders := make([]func(http.Handler) http.Handler, 0, len(r.curMiddlewares)+len(h)+1)
 	for _, m := range r.curMiddlewares {
-		if m != nil {
+		if !isNilOrFuncNil(m) {
 			handlerProviders = append(handlerProviders, toHandlerProvider(m))
 		}
 	}
 	for _, m := range h {
-		if h != nil {
+		if !isNilOrFuncNil(m) {
 			handlerProviders = append(handlerProviders, toHandlerProvider(m))
 		}
 	}

routers/private/internal.go

@@ -5,6 +5,7 @@
 package private
 
 import (
+	"crypto/subtle"
 	"net/http"
 	"strings"
 
@@ -18,22 +19,23 @@ import (
 	chi_middleware "github.com/go-chi/chi/v5/middleware"
 )
 
-// CheckInternalToken check internal token is set
-func CheckInternalToken(next http.Handler) http.Handler {
+func authInternal(next http.Handler) http.Handler {
 	return http.HandlerFunc(func(w http.ResponseWriter, req *http.Request) {
-		tokens := req.Header.Get("Authorization")
-		fields := strings.SplitN(tokens, " ", 2)
 		if setting.InternalToken == "" {
 			log.Warn(`The INTERNAL_TOKEN setting is missing from the configuration file: %q, internal API can't work.`, setting.CustomConf)
 			http.Error(w, http.StatusText(http.StatusForbidden), http.StatusForbidden)
 			return
 		}
-		if len(fields) != 2 || fields[0] != "Bearer" || fields[1] != setting.InternalToken {
+
+		tokens := req.Header.Get("X-Gitea-Internal-Auth") // TODO: use something like JWT or HMAC to avoid passing the token in the clear
+		after, found := strings.CutPrefix(tokens, "Bearer ")
+		authSucceeded := found && subtle.ConstantTimeCompare([]byte(after), []byte(setting.InternalToken)) == 1
+		if !authSucceeded {
 			log.Debug("Forbidden attempt to access internal url: Authorization header: %s", tokens)
 			http.Error(w, http.StatusText(http.StatusForbidden), http.StatusForbidden)
-		} else {
-			next.ServeHTTP(w, req)
+			return
 		}
+		next.ServeHTTP(w, req)
 	})
 }
 
@@ -51,7 +53,7 @@ func bind[T any](_ T) any {
 func Routes() *web.Route {
 	r := web.NewRoute()
 	r.Use(context.PrivateContexter())
-	r.Use(CheckInternalToken)
+	r.Use(authInternal)
 	// Log the real ip address of the request from SSH is really helpful for diagnosing sometimes.
 	// Since internal API will be sent only from Gitea sub commands and it's under control (checked by InternalToken), we can trust the headers.
 	r.Use(chi_middleware.RealIP)