1 files changed, 38 insertions, 52 deletions

diff --git a/lib/group-member.c b/lib/group-member.c
index 0187026..365e166 100644
--- a/lib/group-member.c
+++ b/lib/group-member.c
@@ -1,12 +1,12 @@
 /* group-member.c -- determine whether group id is in calling user's group list
 
-   Copyright (C) 1994, 1997, 1998, 2003, 2005, 2006 Free Software
+   Copyright (C) 1994, 1997-1998, 2003, 2005-2006, 2009-2016 Free Software
    Foundation, Inc.
 
-   This program is free software; you can redistribute it and/or modify
+   This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
-   the Free Software Foundation; either version 2, or (at your option)
-   any later version.
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
 
    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
@@ -14,99 +14,85 @@
    GNU General Public License for more details.
 
    You should have received a copy of the GNU General Public License
-   along with this program; if not, write to the Free Software Foundation,
-   Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.  */
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
 
 #include <config.h>
 
-#include "group-member.h"
+/* Specification.  */
+#include <unistd.h>
 
-#include <stdbool.h>
 #include <stdio.h>
 #include <sys/types.h>
 #include <stdlib.h>
 
-#include <unistd.h>
+#include "xalloc-oversized.h"
 
-#include "xalloc.h"
+/* Most processes have no more than this many groups, and for these
+   processes we can avoid using malloc.  */
+enum { GROUPBUF_SIZE = 100 };
 
 struct group_info
   {
-    int n_groups;
-    GETGROUPS_T *group;
+    gid_t *group;
+    gid_t groupbuf[GROUPBUF_SIZE];
   };
 
-#if HAVE_GETGROUPS
-
 static void
 free_group_info (struct group_info const *g)
 {
-  free (g->group);
+  if (g->group != g->groupbuf)
+    free (g->group);
 }
 
-static bool
+static int
 get_group_info (struct group_info *gi)
 {
-  int n_groups;
-  int n_group_slots = getgroups (0, NULL);
-  GETGROUPS_T *group;
-
-  if (n_group_slots < 0)
-    return false;
+  int n_groups = getgroups (GROUPBUF_SIZE, gi->groupbuf);
+  gi->group = gi->groupbuf;
 
-  /* Avoid xnmalloc, as it goes awry when SIZE_MAX < n_group_slots.  */
-  if (xalloc_oversized (n_group_slots, sizeof *group))
-    xalloc_die ();
-  group = xmalloc (n_group_slots * sizeof *group);
-  n_groups = getgroups (n_group_slots, group);
-
-  /* In case of error, the user loses. */
   if (n_groups < 0)
     {
-      free (group);
-      return false;
+      int n_group_slots = getgroups (0, NULL);
+      if (0 <= n_group_slots
+          && ! xalloc_oversized (n_group_slots, sizeof *gi->group))
+        {
+          gi->group = malloc (n_group_slots * sizeof *gi->group);
+          if (gi->group)
+            n_groups = getgroups (n_group_slots, gi->group);
+        }
     }
 
-  gi->n_groups = n_groups;
-  gi->group = group;
-
-  return true;
+  /* In case of error, the user loses.  */
+  return n_groups;
 }
 
-#endif /* not HAVE_GETGROUPS */
-
 /* Return non-zero if GID is one that we have in our groups list.
-   If there is no getgroups function, return non-zero if GID matches
-   either of the current or effective group IDs.  */
+   Note that the groups list is not guaranteed to contain the current
+   or effective group ID, so they should generally be checked
+   separately.  */
 
 int
 group_member (gid_t gid)
 {
-#ifndef HAVE_GETGROUPS
-  return ((gid == getgid ()) || (gid == getegid ()));
-#else
   int i;
   int found;
   struct group_info gi;
-
-  if (! get_group_info (&gi))
-    return 0;
+  int n_groups = get_group_info (&gi);
 
   /* Search through the list looking for GID. */
   found = 0;
-  for (i = 0; i < gi.n_groups; i++)
+  for (i = 0; i < n_groups; i++)
     {
       if (gid == gi.group[i])
-	{
-	  found = 1;
-	  break;
-	}
+        {
+          found = 1;
+          break;
+        }
     }
 
   free_group_info (&gi);
 
   return found;
-#endif /* HAVE_GETGROUPS */
 }
 
 #ifdef TEST
@@ -120,7 +106,7 @@ main (int argc, char **argv)
 
   program_name = argv[0];
 
-  for (i=1; i<argc; i++)
+  for (i = 1; i < argc; i++)
     {
       gid_t gid;