lib: disable futimes when permission model is enabled

RafaelGSS · marco-ippolito · commit ebbf942a83bc · 2026-01-07T16:37:53.000+01:00
Refs: https://hackerone.com/reports/3390084 PR-URL: nodejs-private/node-private#748 Reviewed-By: Matteo Collina <matteo.collina@gmail.com> Reviewed-By: Anna Henningsen <anna@addaleax.net> CVE-ID: CVE-2025-55132
diff --git a/lib/fs.js b/lib/fs.js
@@ -1261,6 +1261,11 @@ function rmSync(path, options) {
 function fdatasync(fd, callback) {
   const req = new FSReqCallback();
   req.oncomplete = makeCallback(callback);
+
+  if (permission.isEnabled()) {
+    callback(new ERR_ACCESS_DENIED('fdatasync API is disabled when Permission Model is enabled.'));
+    return;
+  }
   binding.fdatasync(fd, req);
 }
 
@@ -1272,6 +1277,9 @@ function fdatasync(fd, callback) {
  * @returns {void}
  */
 function fdatasyncSync(fd) {
+  if (permission.isEnabled()) {
+    throw new ERR_ACCESS_DENIED('fdatasync API is disabled when Permission Model is enabled.');
+  }
   binding.fdatasync(fd);
 }
 
@@ -1285,6 +1293,10 @@ function fdatasyncSync(fd) {
 function fsync(fd, callback) {
   const req = new FSReqCallback();
   req.oncomplete = makeCallback(callback);
+  if (permission.isEnabled()) {
+    callback(new ERR_ACCESS_DENIED('fsync API is disabled when Permission Model is enabled.'));
+    return;
+  }
   binding.fsync(fd, req);
 }
 
@@ -1295,6 +1307,9 @@ function fsync(fd, callback) {
  * @returns {void}
  */
 function fsyncSync(fd) {
+  if (permission.isEnabled()) {
+    throw new ERR_ACCESS_DENIED('fsync API is disabled when Permission Model is enabled.');
+  }
   binding.fsync(fd);
 }
 
@@ -2221,6 +2236,11 @@ function futimes(fd, atime, mtime, callback) {
   mtime = toUnixTimestamp(mtime, 'mtime');
   callback = makeCallback(callback);
 
+  if (permission.isEnabled()) {
+    callback(new ERR_ACCESS_DENIED('futimes API is disabled when Permission Model is enabled.'));
+    return;
+  }
+
   const req = new FSReqCallback();
   req.oncomplete = callback;
   binding.futimes(fd, atime, mtime, req);
@@ -2236,6 +2256,10 @@ function futimes(fd, atime, mtime, callback) {
  * @returns {void}
  */
 function futimesSync(fd, atime, mtime) {
+  if (permission.isEnabled()) {
+    throw new ERR_ACCESS_DENIED('futimes API is disabled when Permission Model is enabled.');
+  }
+
   binding.futimes(
     fd,
     toUnixTimestamp(atime, 'atime'),
diff --git a/test/fixtures/permission/fs-write.js b/test/fixtures/permission/fs-write.js
@@ -573,3 +573,48 @@ const relativeProtectedFolder = process.env.RELATIVEBLOCKEDFOLDER;
     code: 'ERR_ACCESS_DENIED',
   });
 }
+
+// fs.utimes with read-only fd
+{
+  assert.throws(() => {
+    // blocked file is allowed to read
+    const fd = fs.openSync(blockedFile, 'r');
+    const date = new Date();
+    date.setFullYear(2100,0,1);
+
+    fs.futimes(fd, date, date, common.expectsError({
+      code: 'ERR_ACCESS_DENIED',
+    }));
+    fs.futimesSync(fd, date, date);
+  }, {
+    code: 'ERR_ACCESS_DENIED',
+  });
+}
+
+// fs.fdatasync with read-only fd
+{
+  assert.throws(() => {
+    // blocked file is allowed to read
+    const fd = fs.openSync(blockedFile, 'r');
+    fs.fdatasync(fd, common.expectsError({
+      code: 'ERR_ACCESS_DENIED',
+    }));
+    fs.fdatasyncSync(fd);
+  }, {
+    code: 'ERR_ACCESS_DENIED',
+  });
+}
+
+// fs.fsync with read-only fd
+{
+  assert.throws(() => {
+    // blocked file is allowed to read
+    const fd = fs.openSync(blockedFile, 'r');
+    fs.fsync(fd, common.expectsError({
+      code: 'ERR_ACCESS_DENIED',
+    }));
+    fs.fsyncSync(fd);
+  }, {
+    code: 'ERR_ACCESS_DENIED',
+  });
+}
diff --git a/test/parallel/test-permission-fs-supported.js b/test/parallel/test-permission-fs-supported.js
@@ -77,7 +77,22 @@ const ignoreList = [
   'unwatchFile',
   ...syncAndAsyncAPI('lstat'),
   ...syncAndAsyncAPI('realpath'),
-  // fd required methods
+  // File descriptor–based metadata operations
+  //
+  // The kernel does not allow opening a file descriptor for an inode
+  // with write access if the inode itself is read-only. However, it still
+  // permits modifying the inode’s metadata (e.g., permission bits, ownership,
+  // timestamps) because you own the file. These changes can be made either
+  // by referring to the file by name (e.g., chmod) or through any existing
+  // file descriptor that identifies the same inode (e.g., fchmod).
+  //
+  // If the kernel required write access to change metadata, it would be
+  // impossible to modify the permissions of a file once it was made read-only.
+  // For that reason, syscalls such as fchmod, fchown, and futimes bypass
+  // the file descriptor’s access mode. Even a read-only ('r') descriptor
+  // can still update metadata. To prevent unintended modifications,
+  // these APIs are therefore blocked by default when permission model is
+  // enabled.
   ...syncAndAsyncAPI('close'),
   ...syncAndAsyncAPI('fchown'),
   ...syncAndAsyncAPI('fchmod'),
