/soc/2015/mmcc/rand: 8cf1307f1ed8: Finish /dev/urandom read logic

[Michael McConville]

Changeset: 8cf1307f1ed8ad6acb8b7ff1507eec8f847983e8
Author:	 Michael McConville <mmcconville at mykolab.com>
Date:	 2015-08-14 22:57 -0400
Branch:	 default
URL: https://hg.pidgin.im/soc/2015/mmcc/rand/rev/8cf1307f1ed8

Description:

Finish /dev/urandom read logic

diffstat:

 libpurple/util.c |  26 ++++++++++++++++----------
 1 files changed, 16 insertions(+), 10 deletions(-)

diffs (46 lines):

diff --git a/libpurple/util.c b/libpurple/util.c
--- a/libpurple/util.c
+++ b/libpurple/util.c
@@ -4993,9 +4993,10 @@ purple_util_random(void *buf, size_t len
 {
 	int fd;
 	ssize_t res;
+	size_t total = 0;
 	PurpleSslOps *ops = purple_ssl_get_ops();
 
-	/* use SSL API if possible... */
+	/* use SSL API if available... */
 	if (ops && ops->rand_bytes) {
 		return (ops->rand_bytes)(buf, len);
 	/* ...otherwise, fall back to /dev/urandom */
@@ -5006,16 +5007,21 @@ purple_util_random(void *buf, size_t len
 					"could not open /dev/urandom: %s", g_strerror(errno));
 			return 1;
 		}
-		res = read(fd, buf, len);
-		if (res < 0) {
-			purple_debug_error("purple_random",
-					"/dev/urandom read failed: %s", g_strerror(errno));
-			return 1;
-		/* redundant condition to guard against overflow on cast */
-		} else if (res >= 0 && (size_t)res != len) {
-			purple_debug_error("purple_random", "/dev/urandom read returned too little data");
-			return 1;
+		/* this loop could become infinite, but that would be bizarre */
+		while (total < len) {
+			res = read(fd, buf, len - total);
+			if (res < 0) {
+				purple_debug_error("purple_random",
+						"/dev/urandom read failed: %s", g_strerror(errno));
+				close(fd);
+				return 1;
+			/* condition used to clarify danger of underflow on cast */
+			} else {
+				buf += (size_t)res;
+				total += (size_t)res;
+			}
 		}
+		close(fd);
 		return 0;
 	}
 }