SLIP: Add some bounds checks

This should fix GitHub issues #676 and #677.

(backported from commit bbe15da782 in master)

diff --git a/print-sl.c b/print-sl.c
index a02077b3773dd2aba38cb40cb189bf83ed8db603..301c86ce9a0873bac1e51ae077604c7bd81a4aa3 100644 (file)
--- a/print-sl.c
+++ b/print-sl.c
@@ -52,8 +52,8 @@ static const char tstr[] = "[|slip]";
 static u_int lastlen[2][256];
 static u_int lastconn = 255;
 
-static void sliplink_print(netdissect_options *, const u_char *, const struct ip *, u_int);
-static void compressed_sl_print(netdissect_options *, const u_char *, const struct ip *, u_int, int);
+static int sliplink_print(netdissect_options *, const u_char *, const struct ip *, u_int);
+static int compressed_sl_print(netdissect_options *, const u_char *, const struct ip *, u_int, int);
 
 u_int
 sl_if_print(netdissect_options *ndo,
@@ -74,7 +74,10 @@ sl_if_print(netdissect_options *ndo,
        ip = (const struct ip *)(p + SLIP_HDRLEN);
 
        if (ndo->ndo_eflag)
-               sliplink_print(ndo, p, ip, length);
+               if (sliplink_print(ndo, p, ip, length) == -1) {
+                       ND_PRINT((ndo, "%s", tstr));
+                       return (caplen + SLIP_HDRLEN);
+       }
 
        if (caplen < 1 || length < 1) {
                ND_PRINT((ndo, "%s", tstr));
@@ -122,7 +125,7 @@ sl_bsdos_if_print(netdissect_options *ndo,
        return (SLIP_HDRLEN);
 }
 
-static void
+static int
 sliplink_print(netdissect_options *ndo,
                register const u_char *p, register const struct ip *ip,
                register u_int length)
@@ -153,7 +156,7 @@ sliplink_print(netdissect_options *ndo,
                for (i = SLX_CHDR; i < SLX_CHDR + CHDR_LEN - 1; ++i)
                        ND_PRINT((ndo, "%02x.", p[i]));
                ND_PRINT((ndo, "%02x: ", p[SLX_CHDR + CHDR_LEN - 1]));
-               return;
+               return 0;
        }
        switch (p[SLX_CHDR] & 0xf0) {
 
@@ -171,9 +174,11 @@ sliplink_print(netdissect_options *ndo,
                ND_PRINT((ndo, "utcp %d: ", lastconn));
                if (dir == -1) {
                        /* Direction is bogus, don't use it */
-                       return;
+                       return 0;
                }
+               ND_TCHECK(*ip);
                hlen = IP_HL(ip);
+               ND_TCHECK(*((const struct tcphdr *)&((const int *)ip)[hlen]));
                hlen += TH_OFF((const struct tcphdr *)&((const int *)ip)[hlen]);
                lastlen[dir][lastconn] = length - (hlen << 2);
                break;
@@ -181,15 +186,19 @@ sliplink_print(netdissect_options *ndo,
        default:
                if (dir == -1) {
                        /* Direction is bogus, don't use it */
-                       return;
+                       return 0;
                }
                if (p[SLX_CHDR] & TYPE_COMPRESSED_TCP) {
-                       compressed_sl_print(ndo, &p[SLX_CHDR], ip,
-                           length, dir);
+                       if (compressed_sl_print(ndo, &p[SLX_CHDR], ip,
+                                               length, dir) == -1)
+                               goto trunc;
                        ND_PRINT((ndo, ": "));
                } else
                        ND_PRINT((ndo, "slip-%d!: ", p[SLX_CHDR]));
        }
+       return 0;
+trunc:
+       return -1;
 }
 
 static const u_char *
@@ -223,7 +232,7 @@ print_sl_winchange(netdissect_options *ndo,
        return (cp);
 }
 
-static void
+static int
 compressed_sl_print(netdissect_options *ndo,
                     const u_char *chdr, const struct ip *ip,
                     u_int length, int dir)
@@ -269,8 +278,13 @@ compressed_sl_print(netdissect_options *ndo,
         * 'cp - chdr' is the length of the compressed header.
         * 'length - hlen' is the amount of data in the packet.
         */
+       ND_TCHECK(*ip);
        hlen = IP_HL(ip);
+       ND_TCHECK(*((const struct tcphdr *)&((const int32_t *)ip)[hlen]));
        hlen += TH_OFF((const struct tcphdr *)&((const int32_t *)ip)[hlen]);
        lastlen[dir][lastconn] = length - (hlen << 2);
        ND_PRINT((ndo, " %d (%ld)", lastlen[dir][lastconn], (long)(cp - chdr)));
+       return 0;
+trunc:
+       return -1;
 }