Do bounds checking when unescaping PPP.

Clean up a const issue while we're at it.

diff --git a/print-ppp.c b/print-ppp.c
index 8e098f05a953e3230bfa97f726ed2cc144db9c79..9a983e6179cd282a61b33880cdf650db02c2dc2a 100644 (file)
--- a/print-ppp.c
+++ b/print-ppp.c
@@ -1351,14 +1351,15 @@ static void
 ppp_hdlc(netdissect_options *ndo,
          const u_char *p, int length)
 {
-       u_char *b, *s, *t, c;
+       u_char *b, *t, c;
+       const u_char *s;
        int i, proto;
        const void *se;
 
         if (length <= 0)
                 return;
 
-       b = (uint8_t *)malloc(length);
+       b = (u_char *)malloc(length);
        if (b == NULL)
                return;
 
@@ -1367,14 +1368,13 @@ ppp_hdlc(netdissect_options *ndo,
         * Do this so that we dont overwrite the original packet
         * contents.
         */
-       for (s = (u_char *)p, t = b, i = length; i > 0; i--) {
+       for (s = p, t = b, i = length; i > 0 && ND_TTEST(*s); i--) {
                c = *s++;
                if (c == 0x7d) {
-                       if (i > 1) {
-                               i--;
-                               c = *s++ ^ 0x20;
-                       } else
-                               continue;
+                       if (i <= 1 || !ND_TTEST(*s))
+                               break;
+                       i--;
+                       c = *s++ ^ 0x20;
                }
                *t++ = c;
        }