From 7e5a584f0cd7f5d333da5f68e110a75271d8f40d Mon Sep 17 00:00:00 2001
From: Stephen Heumann <heumann1@illinois.edu>
Date: Tue, 4 Nov 2014 16:24:41 -0600
Subject: [PATCH] Use alternative code (also from BusyBox) for checking if the
 user is in a group, avoiding a call to getgroups(), which isn't supported.

This could actually be further simplified, since GNO doesn't really have group-based file permissions, but I'll leave that until later.
---
 coreutils/test.c  | 52 +++--------------------------------------------
 include/libbb.h   |  2 ++
 libbb/appletlib.c | 15 ++++++++++++++
 3 files changed, 20 insertions(+), 49 deletions(-)

diff --git a/coreutils/test.c b/coreutils/test.c
index d2f3b1216..4dc36e8a9 100644
--- a/coreutils/test.c
+++ b/coreutils/test.c
@@ -390,8 +390,6 @@ struct test_statics {
 	/* set only by check_operator(), either to bogus struct
 	 * or points to matching operator_t struct. Never NULL. */
 	const struct operator_t *last_operator;
-	gid_t *group_array;
-	int ngroups;
 	jmp_buf leaving;
 };
 
@@ -401,8 +399,6 @@ extern struct test_statics *const test_ptr_to_statics;
 #define S (*test_ptr_to_statics)
 #define args            (S.args         )
 #define last_operator   (S.last_operator)
-#define group_array     (S.group_array  )
-#define ngroups         (S.ngroups      )
 #define leaving         (S.leaving      )
 
 #define INIT_S() do { \
@@ -561,46 +557,14 @@ static int binop(void)
 }
 
 
-static void initialize_group_array(void)
-{
-	int n;
-
-	/* getgroups may be expensive, try to use it only once */
-	ngroups = 32;
-	do {
-		/* FIXME: ash tries so hard to not die on OOM,
-		 * and we spoil it with just one xrealloc here */
-		/* We realloc, because test_main can be entered repeatedly by shell.
-		 * Testcase (ash): 'while true; do test -x some_file; done'
-		 * and watch top. (some_file must have owner != you) */
-		n = ngroups;
-		group_array = xrealloc(group_array, n * sizeof(gid_t));
-		ngroups = getgroups(n, group_array);
-	} while (ngroups > n);
-}
-
-
 /* Return non-zero if GID is one that we have in our groups list. */
-//XXX: FIXME: duplicate of existing libbb function?
-// see toplevel TODO file:
-// possible code duplication ingroup() and is_a_group_member()
 static int is_a_group_member(gid_t gid)
 {
-	int i;
-
-	/* Short-circuit if possible, maybe saving a call to getgroups(). */
+	/* Short-circuit if possible */
 	if (gid == getgid() || gid == getegid())
 		return 1;
-
-	if (ngroups == 0)
-		initialize_group_array();
-
-	/* Search through the list looking for GID. */
-	for (i = 0; i < ngroups; i++)
-		if (gid == group_array[i])
-			return 1;
-
-	return 0;
+		
+	return ingroup(getuid(), gid) || ingroup(geteuid(), gid);
 }
 
 
@@ -863,16 +827,6 @@ int test_main(int argc, char **argv)
 	if (res)
 		goto ret;
 
-	/* resetting ngroups is probably unnecessary.  it will
-	 * force a new call to getgroups(), which prevents using
-	 * group data fetched during a previous call.  but the
-	 * only way the group data could be stale is if there's
-	 * been an intervening call to setgroups(), and this
-	 * isn't likely in the case of a shell.  paranoia
-	 * prevails...
-	 */
-	/*ngroups = 0; - done by INIT_S() */
-
 	argv++;
 	args = argv;
 
diff --git a/include/libbb.h b/include/libbb.h
index 7ec6ef28f..90b566abd 100644
--- a/include/libbb.h
+++ b/include/libbb.h
@@ -841,6 +841,8 @@ void die_if_bad_username(const char* name) FAST_FUNC;
 #define die_if_bad_username(name) ((void)(name))
 #endif
 
+int ingroup(uid_t u, gid_t g);
+
 #if ENABLE_FEATURE_UTMP
 void FAST_FUNC write_new_utmp(pid_t pid, int new_type, const char *tty_name, const char *username, const char *hostname);
 void FAST_FUNC update_utmp(pid_t pid, int new_type, const char *tty_name, const char *username, const char *hostname);
diff --git a/libbb/appletlib.c b/libbb/appletlib.c
index 1852da245..1d70b7358 100644
--- a/libbb/appletlib.c
+++ b/libbb/appletlib.c
@@ -18,3 +18,18 @@ void FAST_FUNC bb_show_usage(void)
 {
 	xfunc_die();
 }
+
+/* check if u is member of group g */
+int ingroup(uid_t u, gid_t g)
+{
+	struct group *grp = getgrgid(g);
+	if (grp) {
+		char **mem;
+		for (mem = grp->gr_mem; *mem; mem++) {
+			struct passwd *pwd = getpwnam(*mem);
+			if (pwd && (pwd->pw_uid == u))
+				return 1;
+		}
+	}
+	return 0;
+}