lib/getugroups.c

   1 /* getugroups.c -- return a list of the groups a user is in
   2
   3    Copyright (C) 1990, 1991, 1998, 1999, 2000, 2003, 2004 Free
   4    Software Foundation.
   5
   6    This program is free software; you can redistribute it and/or modify
   7    it under the terms of the GNU General Public License as published by
   8    the Free Software Foundation; either version 2, or (at your option)
   9    any later version.
  10
  11    This program is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14    GNU General Public License for more details.
  15
  16    You should have received a copy of the GNU General Public License
  17    along with this program; if not, write to the Free Software Foundation,
  18    Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */
  19
  20 /* Written by David MacKenzie. */
  21
  22 #ifdef HAVE_CONFIG_H
  23 # include <config.h>
  24 #endif
  25
  26 #include <sys/types.h>
  27 #include <stdio.h> /* grp.h on alpha OSF1 V2.0 uses "FILE *". */
  28 #include <grp.h>
  29
  30 #ifdef HAVE_UNISTD_H
  31 # include <unistd.h>
  32 #endif
  33
  34 #include <errno.h>
  35 #ifndef EOVERFLOW
  36 # define EOVERFLOW EINVAL
  37 #endif
  38
  39 /* setgrent, getgrent, and endgrent are not specified by POSIX.1,
  40    so header files might not declare them.
  41    If you don't have them at all, we can't implement this function.
  42    You lose!  */
  43 struct group *getgrent ();
  44
  45 #include <string.h>
  46
  47 #define STREQ(s1, s2) ((strcmp (s1, s2) == 0))
  48
  49 /* Like `getgroups', but for user USERNAME instead of for the current
  50    process.  Store at most MAXCOUNT group IDs in the GROUPLIST array.
  51    If GID is not -1, store it first (if possible).  GID should be the
  52    group ID (pw_gid) obtained from getpwuid, in case USERNAME is not
  53    listed in /etc/groups.
  54    Always return the number of groups of which USERNAME is a member.  */
  55
  56 int
  57 getugroups (int maxcount, GETGROUPS_T *grouplist, char *username, gid_t gid)
  58 {
  59   struct group *grp;
  60   register char **cp;
  61   register int count = 0;
  62
  63   if (gid != (gid_t) -1)
  64     {
  65       if (maxcount != 0)
  66         grouplist[count] = gid;
  67       ++count;
  68     }
  69
  70   setgrent ();
  71   while ((grp = getgrent ()) != 0)
  72     {
  73       for (cp = grp->gr_mem; *cp; ++cp)
  74         {
  75           int n;
  76
  77           if ( ! STREQ (username, *cp))
  78             continue;
  79
  80           /* See if this group number is already on the list.  */
  81           for (n = 0; n < count; ++n)
  82             if (grouplist && grouplist[n] == grp->gr_gid)
  83               break;
  84
  85           /* If it's a new group number, then try to add it to the list.  */
  86           if (n == count)
  87             {
  88               if (maxcount != 0)
  89                 {
  90                   if (count >= maxcount)
  91                     {
  92                       endgrent ();
  93                       return count;
  94                     }
  95                   grouplist[count] = grp->gr_gid;
  96                 }
  97               count++;
  98               if (count < 0)
  99                 {
 100                   errno = EOVERFLOW;
 101                   return -1;
 102                 }
 103             }
 104         }
 105     }
 106   endgrent ();
 107
 108   return count;
 109 }