[PATCH] ping.c : fix min/max packet size usage

[Florian Fainelli]

Hi all,

An OpenWrt user reported that using packet size lower than 15, you could
trigger the following bug :

ping -s 1 -c 1 192.168.0.1
PING 192.168.0.1 (192.168.0.1): 1 data bytes
9 bytes from 192.168.0.1: icmp_seq=0 ttl=64 time=291869364.5 ms


The following patch adds maximum length checking for ICMP packets, as
well as minimum usable size. Also, I noticed that datalen was not used
when generating packets, when not specified, datalen is initialized to
DEFDATALEN.

Thanks.

--- busybox-1.4.1/networking/ping.c     2007-01-24 22:34:34.000000000 +0100
+++ busybox-1.4.1.new/networking/ping.c 2007-02-28 20:35:59.000000000 +0100
@@ -70,7 +70,7 @@
        struct sockaddr_in pingaddr;
        struct icmp *pkt;
        int pingsock, c;
-       char packet[DEFDATALEN + MAXIPLEN + MAXICMPLEN];
+       char packet[datalen + MAXIPLEN + MAXICMPLEN];

        pingsock = create_icmp_socket();

@@ -86,7 +86,7 @@
        pkt->icmp_type = ICMP_ECHO;
        pkt->icmp_cksum = in_cksum((unsigned short *) pkt, sizeof(packet));

-       c = sendto(pingsock, packet, DEFDATALEN + ICMP_MINLEN, 0,
+       c = sendto(pingsock, packet, datalen + ICMP_MINLEN, 0,
                           (struct sockaddr *) &pingaddr, sizeof(struct
sockaddr_in));

        if (c < 0) {
@@ -257,8 +257,8 @@

        gettimeofday(&tv, NULL);

-       /* discard if too short */
-       if (sz < (datalen + ICMP_MINLEN))
+       /* discard if too short / long */
+       if (sz < (datalen + ICMP_MINLEN) || sz > (MAXICMPLEN))
                return;

        /* check IP header */
@@ -274,6 +274,10 @@
                ++nreceived;
                tp = (struct timeval *) icmppkt->icmp_data;

+               /* If packet is too short, results will be truncated */
+               if (sz < (ICMP_MINLEN + sizeof(tv.tv_sec) +
sizeof(tv.tv_usec)))
+                       return;
+
                if ((tv.tv_usec -= tp->tv_usec) < 0) {
                        --tv.tv_sec;
                        tv.tv_usec += 1000000;