library/2175: initgroups() has arbitrary restriction

[Phil Pennock <Phil.Pennock@globnix.org>]

>Number:         2175
>Category:       library
>Synopsis:       initgroups() has arbitrary restriction
>Confidential:   no
>Severity:       non-critical
>Priority:       low
>Responsible:    bugs
>State:          open
>Class:          change-request
>Submitter-Id:   net
>Arrival-Date:   Tue Nov 13 13:30:01 MST 2001
>Last-Modified:
>Originator:     Phil Pennock
>Organization:
>Release:        any
>Environment:
	
	System      : OpenBSD 2.9
	Architecture: OpenBSD.i386
	Machine     : i386
>Description:
initgroups(3) has an arbitrary (documented) limit of the NGROUPS #define.
This could be more flexibly handled using the kern.ngroups sysctl.
ports/security/chrootuid/patches/patch-chrootuid_c contains the relevant
logic from me, if USE_SYSCTL is defined but doesn't release the memory since
chrootuid will exec() shortly thereafter.
>How-To-Repeat:
Current behaviour is as documented.  This is a request for a change to
the desired behaviour.
>Fix:
This patch against src/lib/libc/gen/initgroups.c r1.5 should fix the code
(and remove a bogus #include <stdio.h>).
Man-page should lose the paragraph on the NGROUPS restriction.

--- initgroups.c.orig	Tue Nov 13 21:08:27 2001
+++ initgroups.c	Tue Nov 13 21:18:19 2001
@@ -36,9 +36,10 @@
 #endif /* LIBC_SCCS and not lint */
 
 #include <sys/param.h>
+#include <sys/sysctl.h>
 
 #include <err.h>
-#include <stdio.h>
+#include <stdlib.h>
 #include <unistd.h>
 
 int
@@ -46,12 +47,25 @@
 	const char *uname;
 	gid_t agroup;
 {
-	gid_t groups[NGROUPS];
-	int ngroups;
+	gid_t *groups;
+	int ngroups, mib[2];
+	size_t len;
+
+	mib[0] = CTL_KERN;
+	mib[1] = KERN_NGROUPS;
+	len = sizeof(ngroups);
+
+	if (sysctl(mib, 2, &ngroups, &len, NULL, 0))
+		return (-1);
+
+	if (!(groups = calloc(ngroups, sizeof(int))))
+		return (-1);
 
-	ngroups = NGROUPS;
 	(void) getgrouplist(uname, agroup, groups, &ngroups);
-	if (setgroups(ngroups, groups) < 0)
+	if (setgroups(ngroups, groups) < 0) {
+		free(groups);
 		return (-1);
+	}
+	free(groups);
 	return (0);
 }

>Audit-Trail:
>Unformatted: