New gr_add function to provide a clean and safe method to append a new member

into an existing group.

Submitted by:	db

2 files changed, 42 insertions, 0 deletions

diff --git a/libutil/gr_util.c b/libutil/gr_util.c
index 6bf102f..90062eb 100644
--- a/libutil/gr_util.c
+++ b/libutil/gr_util.c
@@ -479,6 +479,46 @@ gr_dup(const struct group *gr)
 }
 
 /*
+ * Add a new member name to a struct group.
+ */
+struct group *
+gr_add(struct group *gr, const char *newmember)
+{
+	size_t mlen;
+	int num_mem=0;
+	char **members;
+	struct group *newgr;
+
+	if (newmember == NULL)
+		return(gr_dup(gr));
+
+	if (gr->gr_mem != NULL) {
+		for (num_mem = 0; gr->gr_mem[num_mem] != NULL; num_mem++) {
+			if (strcmp(gr->gr_mem[num_mem], newmember) == 0) {
+				errno = EEXIST;
+				return (NULL);
+			}
+		}
+	}
+	/* Allocate enough for current pointers + 1 more and NULL marker */
+	mlen = (num_mem + 2) * sizeof(*gr->gr_mem);
+	if ((members = calloc(1, mlen )) == NULL) {
+		errno = ENOMEM;
+		return (NULL);
+	}
+	memcpy(members, gr->gr_mem, num_mem * sizeof(*gr->gr_mem));
+	members[num_mem++] = (char *)newmember;
+	members[num_mem] = NULL;
+	gr->gr_mem = members;
+	newgr = gr_dup(gr);
+	if (newgr == NULL)
+		errno = ENOMEM;
+
+	free(members);
+	return (newgr);
+}
+
+/*
  * Scan a line and place it into a group structure.
  */
 static bool
diff --git a/libutil/libutil.h b/libutil/libutil.h
index bf42766..fcd74e1 100644
--- a/libutil/libutil.h
+++ b/libutil/libutil.h
@@ -166,6 +166,8 @@ int 	gr_copy(int __ffd, int _tfd, const struct group *_gr,
 	    struct group *_old_gr);
 struct group *
 	gr_dup(const struct group *_gr);
+struct group *
+	gr_add(struct group *_gr, const char *_newmember);
 int	gr_equal(const struct group *_gr1, const struct group *_gr2);
 void	gr_fini(void);
 int	gr_init(const char *_dir, const char *_master);