100 lines
2.3 KiB
C
100 lines
2.3 KiB
C
/* Copyright (C) 1989, 1991, 1993, 1996 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Library General Public License as
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published by the Free Software Foundation; either version 2 of the
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License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Library General Public License for more details.
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You should have received a copy of the GNU Library General Public
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License along with the GNU C Library; see the file COPYING.LIB. If
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not, write to the Free Software Foundation, Inc., 675 Mass Ave,
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Cambridge, MA 02139, USA. */
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#include <alloca.h>
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#include <unistd.h>
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#include <string.h>
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#include <grp.h>
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#include <limits.h>
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#include <sys/types.h>
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/* Initialize the group set for the current user
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by reading the group database and using all groups
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of which USER is a member. Also include GROUP. */
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int
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initgroups (user, group)
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const char *user;
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gid_t group;
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{
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#if defined (NGROUPS_MAX) && NGROUPS_MAX == 0
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/* No extra groups allowed. */
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return 0;
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#else
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struct group *g;
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register size_t n;
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size_t ngroups;
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gid_t *groups;
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#ifdef NGROUPS_MAX
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# define limit NGROUPS_MAX
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ngroups = limit;
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#else
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long int limit = sysconf (_SC_NGROUPS_MAX);
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if (limit > 0)
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ngroups = limit;
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else
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/* No fixed limit on groups. Pick a starting buffer size. */
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ngroups = 16;
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#endif
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groups = __alloca (ngroups * sizeof *groups);
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setgrent ();
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n = 0;
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groups[n++] = group;
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while ((g = getgrent ()) != NULL)
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if (g->gr_gid != group)
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{
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register char **m;
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for (m = g->gr_mem; *m != NULL; ++m)
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if (!strcmp (*m, user))
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break;
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if (*m == NULL)
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{
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/* Matched the user. Insert this group. */
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if (n == ngroups && limit <= 0)
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{
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/* Need a bigger buffer. */
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groups = memcpy (__alloca (ngroups * 2 * sizeof *groups),
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groups, ngroups * sizeof *groups);
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ngroups *= 2;
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}
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groups[n++] = g->gr_gid;
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if (n == limit)
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/* Can't take any more groups; stop searching. */
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break;
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}
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}
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endgrent ();
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return setgroups (n, groups);
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#endif
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}
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