fix(sec): block redirects in repository migration clone (SSRF)

Migration validates the initial clone address against the allow/block
list, but a git-service migration clones with `git clone`, which follows
an HTTP 302 from the remote to an internal address without re-validating.
This let a low-privilege user reach internal services through Gitea.

Refuse redirects on the migration clone via `http.followRedirects=false`,
the only reliable guard since git resolves redirects below Gitea's
validation layer. Applied to both the repository and wiki clones.

Assisted-by: Claude:claude-opus-4-8

modules/git/repo.go

@@ -111,6 +111,9 @@ type CloneRepoOptions struct {
 	SkipTLSVerify bool
 	SingleBranch  bool
 	Env           []string
+	// NoFollowRedirects refuses HTTP redirects during the clone. It is used for
+	// migrations to stop a remote redirecting to an otherwise-blocked address (SSRF).
+	NoFollowRedirects bool
 }
 
 // Clone clones original repository to target path.
@@ -124,6 +127,9 @@ func Clone(ctx context.Context, from, to string, opts CloneRepoOptions) error {
 	if opts.SkipTLSVerify {
 		cmd.AddArguments("-c", "http.sslVerify=false")
 	}
+	if opts.NoFollowRedirects {
+		cmd.AddArguments("-c", "http.followRedirects=false")
+	}
 	if opts.Mirror {
 		cmd.AddArguments("--mirror")
 	}

modules/git/repo_test.go

@@ -4,7 +4,10 @@
 package git
 
 import (
+	"net/http"
+	"net/http/httptest"
 	"path/filepath"
+	"sync/atomic"
 	"testing"
 
 	"github.com/stretchr/testify/assert"
@@ -19,3 +22,34 @@ func TestRepoIsEmpty(t *testing.T) {
 	assert.NoError(t, err)
 	assert.True(t, isEmpty)
 }
+
+// TestCloneNoFollowRedirects ensures the migration clone refuses HTTP redirects,
+// so a remote cannot redirect to an otherwise-blocked address (SSRF). Without the
+// option git follows the redirect and reaches the target.
+func TestCloneNoFollowRedirects(t *testing.T) {
+	var targetHit atomic.Bool
+	target := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		targetHit.Store(true)
+		w.WriteHeader(http.StatusNotFound)
+	}))
+	defer target.Close()
+
+	redirect := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		http.Redirect(w, r, target.URL+r.URL.Path, http.StatusFound)
+	}))
+	defer redirect.Close()
+
+	t.Run("FollowsRedirectByDefault", func(t *testing.T) {
+		targetHit.Store(false)
+		err := Clone(t.Context(), redirect.URL, filepath.Join(t.TempDir(), "dst"), CloneRepoOptions{})
+		assert.Error(t, err)
+		assert.True(t, targetHit.Load(), "git should reach the redirect target without the protection")
+	})
+
+	t.Run("RefusesRedirect", func(t *testing.T) {
+		targetHit.Store(false)
+		err := Clone(t.Context(), redirect.URL, filepath.Join(t.TempDir(), "dst"), CloneRepoOptions{NoFollowRedirects: true})
+		assert.Error(t, err)
+		assert.False(t, targetHit.Load(), "git must not follow the redirect to the target")
+	})
+}

services/repository/migrate.go

@@ -45,10 +45,11 @@ func cloneWiki(ctx context.Context, repo *repo_model.Repository, opts migration.
 		}
 	}
 	if err := gitrepo.CloneExternalRepo(ctx, wikiRemoteURL, storageRepo, git.CloneRepoOptions{
-		Mirror:        true,
-		Quiet:         true,
-		Timeout:       migrateTimeout,
-		SkipTLSVerify: setting.Migrations.SkipTLSVerify,
+		Mirror:            true,
+		Quiet:             true,
+		Timeout:           migrateTimeout,
+		SkipTLSVerify:     setting.Migrations.SkipTLSVerify,
+		NoFollowRedirects: true,
 	}); err != nil {
 		log.Error("Clone wiki failed, err: %v", err)
 		cleanIncompleteWikiPath()
@@ -91,10 +92,11 @@ func MigrateRepositoryGitData(ctx context.Context, u *user_model.User,
 	}
 
 	if err := gitrepo.CloneExternalRepo(ctx, opts.CloneAddr, repo, git.CloneRepoOptions{
-		Mirror:        true,
-		Quiet:         true,
-		Timeout:       migrateTimeout,
-		SkipTLSVerify: setting.Migrations.SkipTLSVerify,
+		Mirror:            true,
+		Quiet:             true,
+		Timeout:           migrateTimeout,
+		SkipTLSVerify:     setting.Migrations.SkipTLSVerify,
+		NoFollowRedirects: true,
 	}); err != nil {
 		if errors.Is(err, context.DeadlineExceeded) {
 			return repo, fmt.Errorf("clone timed out, consider increasing [git.timeout] MIGRATE in app.ini, underlying err: %w", err)