1/* Copyright (C) 1991-2022 Free Software Foundation, Inc.
2 This file is part of the GNU C Library.
3
4 The GNU C Library is free software; you can redistribute it and/or
5 modify it under the terms of the GNU Lesser General Public
6 License as published by the Free Software Foundation; either
7 version 2.1 of the License, or (at your option) any later version.
8
9 The GNU C Library is distributed in the hope that it will be useful,
10 but WITHOUT ANY WARRANTY; without even the implied warranty of
11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
12 Lesser General Public License for more details.
13
14 You should have received a copy of the GNU Lesser General Public
15 License along with the GNU C Library; if not, see
16 <https://www.gnu.org/licenses/>. */
17
18#include <errno.h>
19#include <unistd.h>
20#include <sys/types.h>
21#include <hurd.h>
22#include <hurd/id.h>
23#include <string.h>
24
25/* Set the user ID of the calling process to UID.
26 If the calling process is the super-user, the real
27 and effective user IDs, and the saved set-user-ID to UID;
28 if not, the effective user ID is set to UID. */
29int
30__setuid (uid_t uid)
31{
32 auth_t newauth;
33 error_t err;
34
35retry:
36 HURD_CRITICAL_BEGIN;
37 __mutex_lock (&_hurd_id.lock);
38 err = _hurd_check_ids ();
39
40 if (!err)
41 {
42 /* Make a new auth handle which has UID as the real uid,
43 and as the first element in the list of effective uids. */
44
45 uid_t *newgen, *newaux, auxbuf[2];
46 size_t ngen, naux;
47
48 newaux = _hurd_id.aux.uids;
49 naux = _hurd_id.aux.nuids;
50 if (_hurd_id.gen.nuids == 0)
51 {
52 /* No effective uids now. The new set will be just UID. */
53 newgen = &uid;
54 ngen = 1;
55 }
56 else if (_hurd_id.gen.uids[0] == 0)
57 {
58 /* We are root; set the effective, real, and saved to UID. */
59 _hurd_id.gen.uids[0] = uid;
60 _hurd_id.valid = 0;
61 newgen = _hurd_id.gen.uids;
62 ngen = _hurd_id.gen.nuids;
63 if (_hurd_id.aux.nuids < 2)
64 {
65 newaux = auxbuf;
66 naux = 2;
67 }
68 newaux[0] = newaux[1] = uid;
69 }
70 else
71 {
72 /* We are not root; just change the effective UID. */
73 /* XXX that implies an unprivileged setuid(0) will give
74 the caller root, no questions asked! */
75 _hurd_id.gen.uids[0] = uid;
76 _hurd_id.valid = 0;
77 newgen = _hurd_id.gen.uids;
78 ngen = _hurd_id.gen.nuids;
79 }
80
81 err = __USEPORT (AUTH, __auth_makeauth
82 (port, NULL, MACH_MSG_TYPE_COPY_SEND, 0,
83 newgen, ngen, newaux, naux,
84 _hurd_id.gen.gids, _hurd_id.gen.ngids,
85 _hurd_id.aux.gids, _hurd_id.aux.ngids,
86 &newauth));
87 }
88 __mutex_unlock (&_hurd_id.lock);
89 HURD_CRITICAL_END;
90 if (err == EINTR)
91 /* Got a signal while inside an RPC of the critical section, retry again */
92 goto retry;
93
94 if (err)
95 return __hurd_fail (err);
96
97 /* Install the new handle and reauthenticate everything. */
98 err = __setauth (newauth);
99 __mach_port_deallocate (__mach_task_self (), newauth);
100 return err;
101}
102
103weak_alias (__setuid, setuid)
104

source code of glibc/sysdeps/mach/hurd/setuid.c