fix: Various sec fixes (#38108) (#38147)

Backport #38108

- Enforce repository token scope on RSS/Atom feed endpoints so a PAT
without repo scope can no longer read private repo commit data.
- Block HTTP redirects during repository migration clones to prevent
SSRF reaching internal addresses via an attacker-controlled redirect.
- Redact the notification subject after repo access is revoked so
private issue/PR metadata is no longer leaked through the notification
API.

Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>

modules/git/repo.go

@@ -121,6 +121,9 @@ func Clone(ctx context.Context, from, to string, opts CloneRepoOptions) error {
 	}
 
 	cmd := gitcmd.NewCommand().AddArguments("clone")
+	// Never follow HTTP redirects: no clone caller needs them, and a remote redirecting to an
+	// otherwise-blocked address would be an SSRF vector (e.g. migrating from an attacker URL).
+	cmd.AddArguments("-c", "http.followRedirects=false")
 	if opts.SkipTLSVerify {
 		cmd.AddArguments("-c", "http.sslVerify=false")
 	}

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 +22,23 @@ func TestRepoIsEmpty(t *testing.T) {
 	assert.NoError(t, err)
 	assert.True(t, isEmpty)
 }
+
+// TestCloneRefusesRedirects ensures Clone never follows HTTP redirects, so a remote
+// cannot redirect to an otherwise-blocked address (SSRF, e.g. during migration).
+func TestCloneRefusesRedirects(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()
+
+	err := Clone(t.Context(), redirect.URL, filepath.Join(t.TempDir(), "dst"), CloneRepoOptions{})
+	assert.Error(t, err)
+	assert.False(t, targetHit.Load(), "git must not follow the redirect to the target")
+}