src,deps: disable setuid() etc if io_uring enabled

Within Node.js, attempt to determine if libuv is using io_uring. If it
is, disable process.setuid() and other user identity setters.

We cannot fully prevent users from changing the process's user identity,
but this should still prevent some accidental, dangerous scenarios.

PR-URL: nodejs-private/node-private#528
Reviewed-By: Rafael Gonzaga <rafael.nunu@hotmail.com>
CVE-ID: CVE-2024-22017

Author: tniessen

deps/uv/src/unix/linux.c

@@ -503,6 +503,14 @@ static int uv__use_io_uring(void) {
 }
 
 
+UV_EXTERN int uv__node_patch_is_using_io_uring(void) {
+  // This function exists only in the modified copy of libuv in the Node.js
+  // repository. Node.js checks if this function exists and, if it does, uses it
+  // to determine whether libuv is using io_uring or not.
+  return uv__use_io_uring();
+}
+
+
 static void uv__iou_init(int epollfd,
                          struct uv__iou* iou,
                          uint32_t entries,

doc/api/cli.md

@@ -2896,8 +2896,9 @@ various asynchronous I/O operations.
 
 `io_uring` is disabled by default due to security concerns. When `io_uring`
 is enabled, applications must not change the user identity of the process at
-runtime, neither through JavaScript functions such as [`process.setuid()`][] nor
-through native addons that can invoke system functions such as [`setuid(2)`][].
+runtime. In this case, JavaScript functions such as [`process.setuid()`][] are
+unavailable, and native addons must not invoke system functions such as
+[`setuid(2)`][].
 
 This environment variable is implemented by a dependency of Node.js and may be
 removed in future versions of Node.js. No stability guarantees are provided for

src/node_credentials.cc

@@ -1,4 +1,5 @@
 #include "env-inl.h"
+#include "node_errors.h"
 #include "node_external_reference.h"
 #include "node_internals.h"
 #include "util-inl.h"
@@ -12,6 +13,7 @@
 #include <unistd.h>  // setuid, getuid
 #endif
 #ifdef __linux__
+#include <dlfcn.h>  // dlsym()
 #include <linux/capability.h>
 #include <sys/auxv.h>
 #include <sys/syscall.h>
@@ -231,6 +233,45 @@ static gid_t gid_by_name(Isolate* isolate, Local<Value> value) {
   }
 }
 
+#ifdef __linux__
+extern "C" {
+int uv__node_patch_is_using_io_uring(void);
+
+int uv__node_patch_is_using_io_uring(void) __attribute__((weak));
+
+typedef int (*is_using_io_uring_fn)(void);
+}
+#endif  // __linux__
+
+static bool UvMightBeUsingIoUring() {
+#ifdef __linux__
+  // Support for io_uring is only included in libuv 1.45.0 and later, and only
+  // on Linux (and Android, but there it is always disabled). The patch that we
+  // apply to libuv to work around the io_uring security issue adds a function
+  // that tells us whether io_uring is being used. If that function is not
+  // present, we assume that we are dynamically linking against an unpatched
+  // version.
+  static std::atomic<is_using_io_uring_fn> check =
+      uv__node_patch_is_using_io_uring;
+  if (check == nullptr) {
+    check = reinterpret_cast<is_using_io_uring_fn>(
+        dlsym(RTLD_DEFAULT, "uv__node_patch_is_using_io_uring"));
+  }
+  return uv_version() >= 0x012d00u && (check == nullptr || (*check)());
+#else
+  return false;
+#endif
+}
+
+static bool ThrowIfUvMightBeUsingIoUring(Environment* env, const char* fn) {
+  if (UvMightBeUsingIoUring()) {
+    node::THROW_ERR_INVALID_STATE(
+        env, "%s() disabled: io_uring may be enabled. See CVE-2024-22017.", fn);
+    return true;
+  }
+  return false;
+}
+
 static void GetUid(const FunctionCallbackInfo<Value>& args) {
   Environment* env = Environment::GetCurrent(args);
   CHECK(env->has_run_bootstrapping_code());
@@ -266,6 +307,8 @@ static void SetGid(const FunctionCallbackInfo<Value>& args) {
   CHECK_EQ(args.Length(), 1);
   CHECK(args[0]->IsUint32() || args[0]->IsString());
 
+  if (ThrowIfUvMightBeUsingIoUring(env, "setgid")) return;
+
   gid_t gid = gid_by_name(env->isolate(), args[0]);
 
   if (gid == gid_not_found) {
@@ -285,6 +328,8 @@ static void SetEGid(const FunctionCallbackInfo<Value>& args) {
   CHECK_EQ(args.Length(), 1);
   CHECK(args[0]->IsUint32() || args[0]->IsString());
 
+  if (ThrowIfUvMightBeUsingIoUring(env, "setegid")) return;
+
   gid_t gid = gid_by_name(env->isolate(), args[0]);
 
   if (gid == gid_not_found) {
@@ -304,6 +349,8 @@ static void SetUid(const FunctionCallbackInfo<Value>& args) {
   CHECK_EQ(args.Length(), 1);
   CHECK(args[0]->IsUint32() || args[0]->IsString());
 
+  if (ThrowIfUvMightBeUsingIoUring(env, "setuid")) return;
+
   uid_t uid = uid_by_name(env->isolate(), args[0]);
 
   if (uid == uid_not_found) {
@@ -323,6 +370,8 @@ static void SetEUid(const FunctionCallbackInfo<Value>& args) {
   CHECK_EQ(args.Length(), 1);
   CHECK(args[0]->IsUint32() || args[0]->IsString());
 
+  if (ThrowIfUvMightBeUsingIoUring(env, "seteuid")) return;
+
   uid_t uid = uid_by_name(env->isolate(), args[0]);
 
   if (uid == uid_not_found) {
@@ -363,6 +412,8 @@ static void SetGroups(const FunctionCallbackInfo<Value>& args) {
   CHECK_EQ(args.Length(), 1);
   CHECK(args[0]->IsArray());
 
+  if (ThrowIfUvMightBeUsingIoUring(env, "setgroups")) return;
+
   Local<Array> groups_list = args[0].As<Array>();
   size_t size = groups_list->Length();
   MaybeStackBuffer<gid_t, 64> groups(size);
@@ -394,6 +445,8 @@ static void InitGroups(const FunctionCallbackInfo<Value>& args) {
   CHECK(args[0]->IsUint32() || args[0]->IsString());
   CHECK(args[1]->IsUint32() || args[1]->IsString());
 
+  if (ThrowIfUvMightBeUsingIoUring(env, "initgroups")) return;
+
   Utf8Value arg0(env->isolate(), args[0]);
   gid_t extra_group;
   bool must_free;

test/parallel/test-process-setuid-io-uring.js

@@ -0,0 +1,43 @@
+'use strict';
+const common = require('../common');
+
+const assert = require('node:assert');
+const { execFileSync } = require('node:child_process');
+
+if (!common.isLinux) {
+  common.skip('test is Linux specific');
+}
+
+if (process.arch !== 'x64' && process.arch !== 'arm64') {
+  common.skip('io_uring support on this architecture is uncertain');
+}
+
+const kv = /^(\d+)\.(\d+)\.(\d+)/.exec(execFileSync('uname', ['-r'])).slice(1).map((n) => parseInt(n, 10));
+if (((kv[0] << 16) | (kv[1] << 8) | kv[2]) < 0x050ABA) {
+  common.skip('io_uring is likely buggy due to old kernel');
+}
+
+const userIdentitySetters = [
+  ['setuid', [1000]],
+  ['seteuid', [1000]],
+  ['setgid', [1000]],
+  ['setegid', [1000]],
+  ['setgroups', [[1000]]],
+  ['initgroups', ['nodeuser', 1000]],
+];
+
+for (const [fnName, args] of userIdentitySetters) {
+  const call = `process.${fnName}(${args.map((a) => JSON.stringify(a)).join(', ')})`;
+  const code = `try { ${call}; } catch (err) { console.log(err); }`;
+
+  const stdout = execFileSync(process.execPath, ['-e', code], {
+    encoding: 'utf8',
+    env: { ...process.env, UV_USE_IO_URING: '1' },
+  });
+
+  const msg = new RegExp(`^Error: ${fnName}\\(\\) disabled: io_uring may be enabled\\. See CVE-[X0-9]{4}-`);
+  assert.match(stdout, msg);
+  assert.match(stdout, /code: 'ERR_INVALID_STATE'/);
+
+  console.log(call, stdout.slice(0, stdout.indexOf('\n')));
+}