posix setgid()不能降低权限

Question

我正在尝试创建一个函数来降低sudo权限。

我是一个包dcli的维护者，这是一个旨在取代bash的dart包。

https://pub.dev/packages/dcli

我的目标之一是允许用户将sudo权限降级为原始用户对代码某些部分的权限：

如果我们有一个名为touch_me.dart的脚本

用户将运行：sudo touch_me

touch_me.dart脚本将为：

void main() {
  test('isPriviliged', () {
    try {
      print('isPriviliged: ${Shell.current.isPrivilegedUser}');

      print('uid: ${getuid()}');
      print('gid: ${getgid()}');
      print('euid: ${geteuid()}');
      print('euid: ${geteuid()}');
      print('user: ${getlogin()}');
      print('SUDO_UID: ${env['SUDO_UID']}');
      print('SUDO_USER: ${env['SUDO_USER']}');
      print('SUDO_GUID: ${env['SUDO_GID']}');

  
      print('de-escalating to: uid: $originalUID, gid: $originalGID');

      print('pre-descalation euid: ${geteuid()}');
      print('pre-descalation user egid: ${getegid()}');

      releasePrivileges();

      print('post-descalation euid: ${geteuid()}');
      print('post-descalation user egid: ${getegid()}');

      touch('test.txt', create: true);

      'ls -la test.txt'.run;

      withPrivileges(() {
        print('with privileges euid: ${geteuid()}');
        print('with privileges egid: ${getegid()}');

        touch('test2.txt', create: true);

        'ls -la test2.txt'.run;
      });
    } on PosixException catch (e, st) {
      print(e);
      print(st);
    }
  });
}
 bool get isPrivilegedUser {
    return _whoami() == 'root';
  }


/// revert uid and gid to original user's id's
void releasePrivileges() {
  if (Shell.current.isPrivilegedUser) {
    var sUID = env['SUDO_UID'];
    var gUID = env['SUDO_GID'];

    // convert id's to integers.
    var originalUID = sUID != null ? int.tryParse(sUID) ?? 0 : 0;
    var originalGID = gUID != null ? int.tryParse(gUID) ?? 0 : 0;

    setegid(originalGID);
    seteuid(originalUID);
  }
}

/// Run [privilegedCallback] with root UID and gid
void withPrivileges(RunPrivileged privilegedCallback) {
  var privileged = Shell.current.isPrivilegedUser;

  if (!privileged) {
    setegid(0);
    seteuid(0);
  }

  /// run the callback method with escalated privileges.
  privilegedCallback();

  /// If the code was originally running privileged then
  /// we leave it as it was.
  if (!privileged) {
    releasePrivileges();
  }
}



typedef RunPrivileged = void Function();

除了对gid的更改之外，其他所有内容都可以正常工作。即使releasePrivileges调用setegid( SUDO_GID )并且SUDO_GID为1000，创建的文件的gid也为0。

isPriviliged: true

uid: 0

gid: 0

euid: 0

euid: 0

user: bsutton

SUDO_UID: 1000

SUDO_USER: bsutton

SUDO_GUID: 1000

de-escalating to: uid: 1000, gid: 1000

pre-descalation euid: 0

pre-descalation user egid: 0

post-descalation euid: 1000

post-descalation user egid: 1000

-rw-r--r-- 1 bsutton root 0 Jan 18 10:23 test.txt
with privileges euid: 0

with privileges egid: 0

-rw-r--r-- 1 root root 0 Jan 18 10:23 test2.txt

编辑：

以下是演示该问题的最简单示例：

void main() {
  var sUID = env['SUDO_UID'];
  var gUID = env['SUDO_GID'];

  // convert id's to integers.
  var originalUID = sUID != null ? int.tryParse(sUID) ?? 0 : 0;
  var originalGID = gUID != null ? int.tryParse(gUID) ?? 0 : 0;

  setegid(originalGID);
  seteuid(originalUID);

  touch('test.txt', create: true);

  'ls -la test.txt'.run;
}

Answer 1

问题出在我的测试环境:<

在早期的测试中，我意外地创建了gid = 0的test.txt。

如果我重新运行测试，在开始之前删除test.txt，代码将按预期的:<运行