1 /* provide consistent interface to getgroups for systems that don't allow N==0
2
3 Copyright (C) 1996, 1999, 2003, 2006-2023 Free Software Foundation, Inc.
4
5 This file is free software: you can redistribute it and/or modify
6 it under the terms of the GNU Lesser General Public License as
7 published by the Free Software Foundation; either version 2.1 of the
8 License, or (at your option) any later version.
9
10 This file is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 GNU Lesser General Public License for more details.
14
15 You should have received a copy of the GNU Lesser General Public License
16 along with this program. If not, see <https://www.gnu.org/licenses/>. */
17
18 /* written by Jim Meyering */
19
20 #include <config.h>
21
22 #include <unistd.h>
23
24 #include <errno.h>
25 #include <stdlib.h>
26 #include <stdint.h>
27
28 #if !HAVE_GETGROUPS
29
30 /* Provide a stub that fails with ENOSYS, since there is no group
31 information available on mingw. */
32 int
33 getgroups (_GL_UNUSED int n, _GL_UNUSED GETGROUPS_T *groups)
34 {
35 errno = ENOSYS;
36 return -1;
37 }
38
39 #else /* HAVE_GETGROUPS */
40
41 # undef getgroups
42 # ifndef GETGROUPS_ZERO_BUG
43 # define GETGROUPS_ZERO_BUG 0
44 # endif
45
46 /* On OS X 10.6 and later, use the usual getgroups, not the one
47 supplied when _DARWIN_C_SOURCE is defined. _DARWIN_C_SOURCE is
48 normally defined, since it means "conform to POSIX, but add
49 non-POSIX extensions even if that violates the POSIX namespace
50 rules", which is what we normally want. But with getgroups there
51 is an inconsistency, and _DARWIN_C_SOURCE means "change getgroups()
52 so that it no longer works right". The BUGS section of compat(5)
53 says that the behavior is dubious if you compile different sections
54 of a program with different _DARWIN_C_SOURCE settings, so fix only
55 the offending symbol. */
56 # ifdef __APPLE__
57 int posix_getgroups (int, gid_t []) __asm ("_getgroups");
58 # define getgroups posix_getgroups
59 # endif
60
61 /* On at least NeXTstep 3.2, getgroups (0, NULL) always fails.
62 On other systems, it returns the number of supplemental
63 groups for the process. This function handles that special case
64 and lets the system-provided function handle all others. However,
65 it can fail with ENOMEM if memory is tight. It is unspecified
66 whether the effective group id is included in the list. */
67
68 int
69 rpl_getgroups (int n, gid_t *group)
70 {
71 int n_groups;
72 GETGROUPS_T *gbuf;
73
74 if (n < 0)
75 {
76 errno = EINVAL;
77 return -1;
78 }
79
80 if (n != 0 || !GETGROUPS_ZERO_BUG)
81 {
82 int result;
83 if (sizeof *group == sizeof *gbuf)
84 return getgroups (n, (GETGROUPS_T *) group);
85
86 if (SIZE_MAX / sizeof *gbuf <= n)
87 {
88 errno = ENOMEM;
89 return -1;
90 }
91 gbuf = malloc (n * sizeof *gbuf);
92 if (!gbuf)
93 return -1;
94 result = getgroups (n, gbuf);
95 if (0 <= result)
96 {
97 n = result;
98 while (n--)
99 group[n] = gbuf[n];
100 }
101 free (gbuf);
102 return result;
103 }
104
105 n = 20;
106 while (1)
107 {
108 /* No need to worry about address arithmetic overflow here,
109 since the ancient systems that we're running on have low
110 limits on the number of secondary groups. */
111 gbuf = malloc (n * sizeof *gbuf);
112 if (!gbuf)
113 return -1;
114 n_groups = getgroups (n, gbuf);
115 if (n_groups == -1 ? errno != EINVAL : n_groups < n)
116 break;
117 free (gbuf);
118 n *= 2;
119 }
120
121 free (gbuf);
122 return n_groups;
123 }
124
125 #endif /* HAVE_GETGROUPS */