getgrouplist implementation

[Mark Kettenis <kettenis at wins dot uva dot nl>]

Here is a patch that implements getgrouplist() from 4.4 BSD.  We
really need this to handle supplementary group ID's in the Hurd and
implementing it outside glibc would be pretty hard.  I added the
prototype to <grp.h> since that is where initgroups() and setgroups()
live.  On *BSD all these functions live in <unistd.h>, so perhaps we
should also add these prototypes there.

Mark


Index: ChangeLog
from  Mark Kettenis  <kettenis@gnu.org>

	* grp/initgroups.c (initgroups): Factor out re-usable code into...
	(internal_getgrouplist): ... new function.
	(getgrouplist): New function.
	* grp/grp.h (getgrouplist): New prototype.
	* grp/Versions [2.2.4]: Add getgrouplist.

Index: grp/initgroups.c
===================================================================
RCS file: /cvs/glibc/libc/grp/initgroups.c,v
retrieving revision 1.24
diff -u -p -r1.24 initgroups.c
--- grp/initgroups.c 2001/04/17 03:34:06 1.24
+++ grp/initgroups.c 2001/06/07 19:42:10
@@ -136,51 +136,19 @@ compat_call (service_user *nip, const ch
   return NSS_STATUS_SUCCESS;
 }
 
-/* Initialize the group set for the current user
-   by reading the group database and using all groups
-   of which USER is a member.  Also include GROUP.  */
-int
-initgroups (user, group)
-     const char *user;
-     gid_t group;
+static int
+internal_getgrouplist (const char *user, gid_t group, long int *size,
+		       gid_t **groupsp, long int limit)
 {
-#if defined NGROUPS_MAX && NGROUPS_MAX == 0
-
-  /* No extra groups allowed.  */
-  return 0;
-
-#else
-
   service_user *nip = NULL;
   initgroups_dyn_function fct;
   enum nss_status status = NSS_STATUS_UNAVAIL;
   int no_more;
   /* Start is one, because we have the first group as parameter.  */
   long int start = 1;
-  long int size;
-  gid_t *groups;
-  int result;
 
-  /* We always use sysconf even if NGROUPS_MAX is defined.  That way, the
-     limit can be raised in the kernel configuration without having to
-     recompile libc.  */
-  long int limit = __sysconf (_SC_NGROUPS_MAX);
+  *groupsp[0] = group;
 
-  if (limit > 0)
-    size = limit;
-  else
-    {
-      /* No fixed limit on groups.  Pick a starting buffer size.  */
-      size = 16;
-    }
-
-  groups = (gid_t *) malloc (size * sizeof (gid_t));
-  if (__builtin_expect (groups == NULL, 0))
-    /* No more memory.  */
-    return -1;
-
-  groups[0] = group;
-
   if (__nss_group_database != NULL)
     {
       no_more = 0;
@@ -196,14 +164,14 @@ initgroups (user, group)
 
       if (fct == NULL)
 	{
-	  status = compat_call (nip, user, group, &start, &size, &groups,
+	  status = compat_call (nip, user, group, &start, size, groupsp,
 				limit, &errno);
 
 	  if (nss_next_action (nip, NSS_STATUS_UNAVAIL) != NSS_ACTION_CONTINUE)
 	    break;
 	}
       else
-	status = DL_CALL_FCT (fct, (user, group, &start, &size, &groups,
+	status = DL_CALL_FCT (fct, (user, group, &start, size, groupsp,
 				    limit, &errno));
 
       /* This is really only for debugging.  */
@@ -220,10 +188,81 @@ initgroups (user, group)
 	nip = nip->next;
     }
 
+  return start;
+}
+
+/* Store at most *NGROUPS members of the group set for USER into
+   *GROUPS.  Also include GROUP.  The actual number of groups found is
+   returned in *NGROUPS.  Return -1 if the if *NGROUPS is too small.  */
+int
+getgrouplist (const char *user, gid_t group, gid_t *groups, int *ngroups)
+{
+  gid_t *newgroups;
+  long int size = *ngroups;
+  int result;
+
+  newgroups = (gid_t *) malloc (size * sizeof (gid_t));
+  if (__builtin_expect (newgroups == NULL, 0))
+    /* No more memory.  */
+    return -1;
+
+  result = internal_getgrouplist (user, group, &size, &newgroups, -1);
+  if (result > *ngroups)
+    {
+      *ngroups = result;
+      result = -1;
+    }
+  else
+    *ngroups = result;
+      
+  memcpy (groups, newgroups, *ngroups * sizeof (gid_t));
+
+  free (newgroups);
+  return result;
+}
+
+/* Initialize the group set for the current user
+   by reading the group database and using all groups
+   of which USER is a member.  Also include GROUP.  */
+int
+initgroups (const char *user, gid_t group)
+{
+#if defined NGROUPS_MAX && NGROUPS_MAX == 0
+
+  /* No extra groups allowed.  */
+  return 0;
+
+#else
+
+  long int size;
+  gid_t *groups;
+  int ngroups;
+  int result;
+
+ /* We always use sysconf even if NGROUPS_MAX is defined.  That way, the
+     limit can be raised in the kernel configuration without having to
+     recompile libc.  */
+  long int limit = __sysconf (_SC_NGROUPS_MAX);
+
+  if (limit > 0)
+    size = limit;
+  else
+    {
+      /* No fixed limit on groups.  Pick a starting buffer size.  */
+      size = 16;
+    }
+
+  groups = (gid_t *) malloc (size * sizeof (gid_t));
+  if (__builtin_expect (groups == NULL, 0))
+    /* No more memory.  */
+    return -1;
+
+  ngroups = internal_getgrouplist (user, group, &size, &groups, limit);
+
   /* Try to set the maximum number of groups the kernel can handle.  */
   do
-    result = setgroups (start, groups);
-  while (result == -1 && errno == EINVAL && --start > 0);
+    result = setgroups (ngroups, groups);
+  while (result == -1 && errno == EINVAL && --ngroups > 0);
 
   free (groups);
 
Index: grp/grp.h
===================================================================
RCS file: /cvs/glibc/libc/grp/grp.h,v
retrieving revision 1.28
diff -u -p -r1.28 grp.h
--- grp/grp.h 2000/02/28 04:24:18 1.28
+++ grp/grp.h 2001/06/07 19:42:10
@@ -1,4 +1,4 @@
-/* Copyright (C) 1991,92,95,96,97,98,99,2000 Free Software Foundation, Inc.
+/* Copyright (C) 1991,92,95,96,97,98,99,2000,01 Free Software Foundation, Inc.
    This file is part of the GNU C Library.
 
    The GNU C Library is free software; you can redistribute it and/or
@@ -135,6 +135,12 @@ extern int fgetgrent_r (FILE *__restrict
 
 /* Set the group set for the current user to GROUPS (N of them).  */
 extern int setgroups (size_t __n, __const __gid_t *__groups) __THROW;
+
+/* Store at most *NGROUPS members of the group set for USER into
+   *GROUPS.  Also include GROUP.  The actual number of groups found is
+   returned in *NGROUPS.  Return -1 if the if *NGROUPS is too small.  */
+extern int getgrouplist (__const char *__user, __gid_t __group,
+			 __gid_t *__groups, int *__ngroups) __THROW;
 
 /* Initialize the group set for the current user
    by reading the group database and using all groups
Index: grp/Versions
===================================================================
RCS file: /cvs/glibc/libc/grp/Versions,v
retrieving revision 1.3
diff -u -p -r1.3 Versions
--- grp/Versions 1999/07/09 20:47:25 1.3
+++ grp/Versions 2001/06/07 19:42:10
@@ -24,4 +24,8 @@ libc {
     # g*
     getgrent_r; getgrgid_r; getgrnam_r;
   }
+  GLIBC_2.2.4 {
+    # g*
+    getgrouplist;
+  }
 }