CVE-2017-13687/CHDLC: Improve bounds and length checks.

[tcpdump] / print-sl.c

diff --git a/print-sl.c b/print-sl.c
index b69a07d5627be1673863ba43e0365d2b5802ae40..a02077b3773dd2aba38cb40cb189bf83ed8db603 100644 (file)
--- a/print-sl.c
+++ b/print-sl.c
@@ -19,6 +19,8 @@
  * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
  */
 
+/* \summary: Compressed Serial Line Internet Protocol printer */
+
 #ifdef HAVE_CONFIG_H
 #include "config.h"
 #endif
@@ -66,6 +68,7 @@ sl_if_print(netdissect_options *ndo,
                return (caplen);
        }
 
+       caplen -= SLIP_HDRLEN;
        length -= SLIP_HDRLEN;
 
        ip = (const struct ip *)(p + SLIP_HDRLEN);
@@ -73,6 +76,11 @@ sl_if_print(netdissect_options *ndo,
        if (ndo->ndo_eflag)
                sliplink_print(ndo, p, ip, length);
 
+       if (caplen < 1 || length < 1) {
+               ND_PRINT((ndo, "%s", tstr));
+               return (caplen + SLIP_HDRLEN);
+       }
+
        switch (IP_V(ip)) {
        case 4:
                ip_print(ndo, (const u_char *)ip, length);
@@ -123,8 +131,21 @@ sliplink_print(netdissect_options *ndo,
        u_int hlen;
 
        dir = p[SLX_DIR];
-       ND_PRINT((ndo, dir == SLIPDIR_IN ? "I " : "O "));
+       switch (dir) {
 
+       case SLIPDIR_IN:
+               ND_PRINT((ndo, "I "));
+               break;
+
+       case SLIPDIR_OUT:
+               ND_PRINT((ndo, "O "));
+               break;
+
+       default:
+               ND_PRINT((ndo, "Invalid direction %d ", dir));
+               dir = -1;
+               break;
+       }
        if (ndo->ndo_nflag) {
                /* XXX just dump the header */
                register int i;
@@ -147,13 +168,21 @@ sliplink_print(netdissect_options *ndo,
                 * has restored the IP header copy to IPPROTO_TCP.
                 */
                lastconn = ((const struct ip *)&p[SLX_CHDR])->ip_p;
+               ND_PRINT((ndo, "utcp %d: ", lastconn));
+               if (dir == -1) {
+                       /* Direction is bogus, don't use it */
+                       return;
+               }
                hlen = IP_HL(ip);
                hlen += TH_OFF((const struct tcphdr *)&((const int *)ip)[hlen]);
                lastlen[dir][lastconn] = length - (hlen << 2);
-               ND_PRINT((ndo, "utcp %d: ", lastconn));
                break;
 
        default:
+               if (dir == -1) {
+                       /* Direction is bogus, don't use it */
+                       return;
+               }
                if (p[SLX_CHDR] & TYPE_COMPRESSED_TCP) {
                        compressed_sl_print(ndo, &p[SLX_CHDR], ip,
                            length, dir);