pptp: reject a malformed bind address

An unparsable bind= value went through inet_addr() unchecked and became
255.255.255.255, so the only symptom was bind() failing with "Cannot
assign requested address", which does not point at the configuration.
Parse with inet_aton() and name the offending value instead.

Also zero the address before filling it in, so the padding passed to
bind() is not stack garbage.

1 files changed, 8 insertions, 3 deletions

diff --git a/accel-pppd/ctrl/pptp/pptp.c b/accel-pppd/ctrl/pptp/pptp.c
index ec054e67..7cfccce1 100644
--- a/accel-pppd/ctrl/pptp/pptp.c
+++ b/accel-pppd/ctrl/pptp/pptp.c
@@ -911,12 +911,17 @@ static void pptp_init(void)
 
 	fcntl(serv.hnd.fd, F_SETFD, fcntl(serv.hnd.fd, F_GETFD) | FD_CLOEXEC);
 
+	memset(&addr, 0, sizeof(addr));
 	addr.sin_family = AF_INET;
 
 	opt = conf_get_opt("pptp", "bind");
-	if (opt)
-		addr.sin_addr.s_addr = inet_addr(opt);
-	else
+	if (opt) {
+		if (!inet_aton(opt, &addr.sin_addr)) {
+			log_emerg("pptp: failed to parse bind address '%s'\n", opt);
+			close(serv.hnd.fd);
+			return;
+		}
+	} else
 		addr.sin_addr.s_addr = htonl(INADDR_ANY);
 
 	opt = conf_get_opt("pptp", "port");