1 /* provide consistent interface to getgroups for systems that don't allow N==0 2 3 Copyright (C) 1996, 1999, 2003, 2006-2021 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 */