In preparation for raising NGROUPS and NGROUPS_MAX, change base

system callers of getgroups(), getgrouplist(), and setgroups() to
allocate buffers dynamically.  Specifically, allocate a buffer of size
sysconf(_SC_NGROUPS_MAX)+1 (+2 in a few cases to allow for overflow).

This (or similar gymnastics) is required for the code to actually follow
the POSIX.1-2008 specification where {NGROUPS_MAX} may differ at runtime
and where getgroups may return {NGROUPS_MAX}+1 results on systems like
FreeBSD which include the primary group.

In id(1), don't pointlessly add the primary group to the list of all
groups, it is always the first result from getgroups().  In principle
the old code was more portable, but this was only done in one of the two
places where getgroups() was called to the overall effect was pointless.

Document the actual POSIX requirements in the getgroups(2) and
setgroups(2) manpages.  We do not yet support a dynamic NGROUPS, but we
may in the future.

MFC after:	2 weeks

3 files changed, 34 insertions, 13 deletions

diff --git a/usr.bin/id/id.c b/usr.bin/id/id.c
index d18e8b0..1929d96 100644
--- a/usr.bin/id/id.c
+++ b/usr.bin/id/id.c
@@ -258,7 +258,8 @@ id_print(struct passwd *pw, int use_ggl, int p_euid, int p_egid)
 	gid_t gid, egid, lastgid;
 	uid_t uid, euid;
 	int cnt, ngroups;
-	gid_t groups[NGROUPS + 1];
+	long ngroups_max;
+	gid_t *groups;
 	const char *fmt;
 
 	if (pw != NULL) {
@@ -270,12 +271,16 @@ id_print(struct passwd *pw, int use_ggl, int p_euid, int p_egid)
 		gid = getgid();
 	}
 
+	ngroups_max = sysconf(_SC_NGROUPS_MAX) + 1;
+	if ((groups = malloc(sizeof(gid_t) * ngroups_max)) == NULL)
+		err(1, "malloc");
+
 	if (use_ggl && pw != NULL) {
-		ngroups = NGROUPS + 1;
+		ngroups = ngroups_max;
 		getgrouplist(pw->pw_name, gid, groups, &ngroups);
 	}
 	else {
-		ngroups = getgroups(NGROUPS + 1, groups);
+		ngroups = getgroups(ngroups_max, groups);
 	}
 
 	if (pw != NULL)
@@ -306,6 +311,7 @@ id_print(struct passwd *pw, int use_ggl, int p_euid, int p_egid)
 		lastgid = gid;
 	}
 	printf("\n");
+	free(groups);
 }
 
 #ifdef USE_BSM_AUDIT
@@ -361,15 +367,19 @@ group(struct passwd *pw, int nflag)
 {
 	struct group *gr;
 	int cnt, id, lastid, ngroups;
-	gid_t groups[NGROUPS + 1];
+	long ngroups_max;
+	gid_t *groups;
 	const char *fmt;
 
+	ngroups_max = sysconf(_SC_NGROUPS_MAX) + 1;
+	if ((groups = malloc(sizeof(gid_t) * (ngroups_max))) == NULL)
+		err(1, "malloc");
+
 	if (pw) {
-		ngroups = NGROUPS + 1;
+		ngroups = ngroups_max;
 		(void) getgrouplist(pw->pw_name, pw->pw_gid, groups, &ngroups);
 	} else {
-		groups[0] = getgid();
-		ngroups = getgroups(NGROUPS, groups + 1) + 1;
+		ngroups = getgroups(ngroups_max, groups);
 	}
 	fmt = nflag ? "%s" : "%u";
 	for (lastid = -1, cnt = 0; cnt < ngroups; ++cnt) {
@@ -389,6 +399,7 @@ group(struct passwd *pw, int nflag)
 		lastid = id;
 	}
 	(void)printf("\n");
+	free(groups);
 }
 
 void
diff --git a/usr.bin/newgrp/newgrp.c b/usr.bin/newgrp/newgrp.c
index 62d552f..91b62a5 100644
--- a/usr.bin/newgrp/newgrp.c
+++ b/usr.bin/newgrp/newgrp.c
@@ -146,8 +146,8 @@ restoregrps(void)
 static void
 addgroup(const char *grpname)
 {
-	gid_t grps[NGROUPS_MAX];
-	long lgid;
+	gid_t *grps;
+	long lgid, ngrps_max;
 	int dbmember, i, ngrps;
 	gid_t egid;
 	struct group *grp;
@@ -185,7 +185,10 @@ addgroup(const char *grpname)
 		}
 	}
 
-	if ((ngrps = getgroups(NGROUPS_MAX, (gid_t *)grps)) < 0) {
+	ngrps_max = sysconf(_SC_NGROUPS_MAX) + 1;
+	if ((grps = malloc(sizeof(gid_t) * ngrps_max)) == NULL)
+		err(1, "malloc");
+	if ((ngrps = getgroups(ngrps_max, (gid_t *)grps)) < 0) {
 		warn("getgroups");
 		return;
 	}
@@ -217,7 +220,7 @@ addgroup(const char *grpname)
 
 	/* Add old effective gid to supp. list if it does not exist. */
 	if (egid != grp->gr_gid && !inarray(egid, grps, ngrps)) {
-		if (ngrps == NGROUPS_MAX)
+		if (ngrps == ngrps_max)
 			warnx("too many groups");
 		else {
 			grps[ngrps++] = egid;
@@ -231,6 +234,7 @@ addgroup(const char *grpname)
 		}
 	}
 
+	free(grps);
 }
 
 static int
diff --git a/usr.bin/quota/quota.c b/usr.bin/quota/quota.c
index 503b43d..f504e7c 100644
--- a/usr.bin/quota/quota.c
+++ b/usr.bin/quota/quota.c
@@ -117,7 +117,8 @@ int
 main(int argc, char *argv[])
 {
 	int ngroups; 
-	gid_t mygid, gidset[NGROUPS];
+	long ngroups_max;
+	gid_t mygid, *gidset;
 	int i, ch, gflag = 0, uflag = 0, errflag = 0;
 
 	while ((ch = getopt(argc, argv, "f:ghlrquv")) != -1) {
@@ -159,13 +160,18 @@ main(int argc, char *argv[])
 			errflag += showuid(getuid());
 		if (gflag) {
 			mygid = getgid();
-			ngroups = getgroups(NGROUPS, gidset);
+			ngroups_max = sysconf(_SC_NGROUPS_MAX) + 1;
+			if ((gidset = malloc(sizeof(gid_t) * ngroups_max))
+			    == NULL)
+				err(1, "malloc");
+			ngroups = getgroups(ngroups_max, gidset);
 			if (ngroups < 0)
 				err(1, "getgroups");
 			errflag += showgid(mygid);
 			for (i = 0; i < ngroups; i++)
 				if (gidset[i] != mygid)
 					errflag += showgid(gidset[i]);
+			free(gidset);
 		}
 		return(errflag);
 	}