fix: dangling symlink, write, delete scope bugs

http/resource_test.go

@@ -5,6 +5,7 @@ import (
 	"net/http/httptest"
 	"os"
 	"path/filepath"
+	"strings"
 	"testing"
 	"time"
 
@@ -14,6 +15,7 @@ import (
 
 	"github.com/filebrowser/filebrowser/v2/diskcache"
 	"github.com/filebrowser/filebrowser/v2/settings"
+	"github.com/filebrowser/filebrowser/v2/storage"
 	"github.com/filebrowser/filebrowser/v2/storage/bolt"
 	"github.com/filebrowser/filebrowser/v2/users"
 )
@@ -115,3 +117,108 @@ func signToken(t *testing.T, perm users.Permissions, key []byte) string {
 	}
 	return signed
 }
+
+// scopedUserStorage returns a storage whose single user (ID 1) is scoped to
+// userScope through a symlink-confining ScopedFs (via customFSUser), mirroring
+// production. Used by the symlink scope-escape regression tests below.
+func scopedUserStorage(t *testing.T, userScope string, perm users.Permissions, key []byte) *storage.Storage {
+	t.Helper()
+	db, err := storm.Open(filepath.Join(t.TempDir(), "db"))
+	if err != nil {
+		t.Fatalf("failed to open db: %v", err)
+	}
+	t.Cleanup(func() { _ = db.Close() })
+
+	st, err := bolt.NewStorage(db)
+	if err != nil {
+		t.Fatalf("failed to get storage: %v", err)
+	}
+	if err := st.Users.Save(&users.User{Username: "u", Password: "pw", Perm: perm}); err != nil {
+		t.Fatalf("failed to save user: %v", err)
+	}
+	if err := st.Settings.Save(&settings.Settings{Key: key}); err != nil {
+		t.Fatalf("failed to save settings: %v", err)
+	}
+	st.Users = &customFSUser{
+		Store: st.Users,
+		fs:    afero.NewBasePathFs(afero.NewOsFs(), userScope),
+	}
+	return st
+}
+
+// Regression for the dangling-symlink write escape (GHSA-8wc8-hf36-mjh9 /
+// GHSA-fh54-6rfh-r8f3): POSTing to an in-scope dangling symlink whose target is
+// outside the scope must not dereference the link to create the out-of-scope
+// file.
+func TestResourcePostRejectsDanglingSymlinkWriteEscape(t *testing.T) {
+	root := t.TempDir()
+	userScope := filepath.Join(root, "user")
+	outside := filepath.Join(root, "outside")
+	for _, d := range []string{userScope, outside} {
+		if err := os.MkdirAll(d, 0o755); err != nil {
+			t.Fatal(err)
+		}
+	}
+	// A dangling symlink inside the scope pointing at a not-yet-existing file
+	// outside it (planted out-of-band, per the advisory preconditions).
+	outsideTarget := filepath.Join(outside, "created.txt")
+	if err := os.Symlink(outsideTarget, filepath.Join(userScope, "evil")); err != nil {
+		t.Skipf("cannot create symlink: %v", err)
+	}
+
+	key := []byte("test-signing-key")
+	perm := users.Permissions{Create: true, Modify: true}
+	st := scopedUserStorage(t, userScope, perm, key)
+	signed := signToken(t, perm, key)
+
+	req, _ := http.NewRequest(http.MethodPost, "/evil?override=true", strings.NewReader("http-outside"))
+	req.Header.Set("X-Auth", signed)
+	rec := httptest.NewRecorder()
+	handle(resourcePostHandler(diskcache.NewNoOp()), "", st, &settings.Server{}).ServeHTTP(rec, req)
+
+	if _, statErr := os.Stat(outsideTarget); statErr == nil {
+		data, _ := os.ReadFile(outsideTarget)
+		t.Fatalf("VULNERABLE: out-of-scope file created via dangling symlink (status=%d, content=%q)", rec.Code, string(data))
+	}
+	if rec.Code != http.StatusForbidden {
+		t.Errorf("expected 403, got %d body=%q", rec.Code, rec.Body.String())
+	}
+}
+
+// Regression for the symlink-following delete escape (GHSA-hq4g-mpch-f9vp /
+// GHSA-fmm7-x4gx-8jhr): a Create-only user POSTing to a child of an escaping
+// symlinked directory must not delete the out-of-scope target through the
+// failed-upload cleanup RemoveAll.
+func TestResourcePostCleanupDoesNotDeleteThroughSymlink(t *testing.T) {
+	root := t.TempDir()
+	userScope := filepath.Join(root, "user")
+	outside := filepath.Join(root, "outside")
+	for _, d := range []string{userScope, outside} {
+		if err := os.MkdirAll(d, 0o755); err != nil {
+			t.Fatal(err)
+		}
+	}
+	victim := filepath.Join(outside, "victim.txt")
+	if err := os.WriteFile(victim, []byte("keep"), 0o644); err != nil {
+		t.Fatal(err)
+	}
+	// An escaping directory symlink inside the scope (planted out-of-band).
+	if err := os.Symlink(outside, filepath.Join(userScope, "link")); err != nil {
+		t.Skipf("cannot create symlink: %v", err)
+	}
+
+	key := []byte("test-signing-key")
+	// Create-only: Perm.Delete is deliberately false — the bug must not need it.
+	perm := users.Permissions{Create: true}
+	st := scopedUserStorage(t, userScope, perm, key)
+	signed := signToken(t, perm, key)
+
+	req, _ := http.NewRequest(http.MethodPost, "/link/victim.txt", strings.NewReader("x"))
+	req.Header.Set("X-Auth", signed)
+	rec := httptest.NewRecorder()
+	handle(resourcePostHandler(diskcache.NewNoOp()), "", st, &settings.Server{}).ServeHTTP(rec, req)
+
+	if _, statErr := os.Stat(victim); statErr != nil {
+		t.Fatalf("VULNERABLE: out-of-scope victim.txt deleted by cleanup RemoveAll (status=%d): %v", rec.Code, statErr)
+	}
+}