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

[tcpdump] / util-print.c

diff --git a/util-print.c b/util-print.c
index 7071ee8a41e401e7c840eb27ad5db91b1ed02a29..281ecd767d1a2d9cb518f829eac0c3bf62e8aa1e 100644 (file)
--- a/util-print.c
+++ b/util-print.c
@@ -21,7 +21,7 @@
 
 /*
  * txtproto_print() derived from original code by Hannes Gredler
- * (hannes@juniper.net):
+ * (hannes@gredler.at):
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that: (1) source code
@@ -387,27 +387,23 @@ ts_print(netdissect_options *ndo,
 }
 
 /*
- * Print a relative number of seconds (e.g. hold time, prune timer)
+ * Print an unsigned relative number of seconds (e.g. hold time, prune timer)
  * in the form 5m1s.  This does no truncation, so 32230861 seconds
  * is represented as 1y1w1d1h1m1s.
  */
 void
-relts_print(netdissect_options *ndo,
-            int secs)
+unsigned_relts_print(netdissect_options *ndo,
+                     uint32_t secs)
 {
        static const char *lengths[] = {"y", "w", "d", "h", "m", "s"};
-       static const int seconds[] = {31536000, 604800, 86400, 3600, 60, 1};
+       static const u_int seconds[] = {31536000, 604800, 86400, 3600, 60, 1};
        const char **l = lengths;
-       const int *s = seconds;
+       const u_int *s = seconds;
 
        if (secs == 0) {
                ND_PRINT((ndo, "0s"));
                return;
        }
-       if (secs < 0) {
-               ND_PRINT((ndo, "-"));
-               secs = -secs;
-       }
        while (secs > 0) {
                if (secs >= *s) {
                        ND_PRINT((ndo, "%d%s", secs / *s, *l));
@@ -418,6 +414,42 @@ relts_print(netdissect_options *ndo,
        }
 }
 
+/*
+ * Print a signed relative number of seconds (e.g. hold time, prune timer)
+ * in the form 5m1s.  This does no truncation, so 32230861 seconds
+ * is represented as 1y1w1d1h1m1s.
+ */
+void
+signed_relts_print(netdissect_options *ndo,
+                   int32_t secs)
+{
+       if (secs < 0) {
+               ND_PRINT((ndo, "-"));
+               if (secs == INT32_MIN) {
+                       /*
+                        * -2^31; you can't fit its absolute value into
+                        * a 32-bit signed integer.
+                        *
+                        * Just directly pass said absolute value to
+                        * unsigned_relts_print() directly.
+                        *
+                        * (XXX - does ISO C guarantee that -(-2^n),
+                        * when calculated and cast to an n-bit unsigned
+                        * integer type, will have the value 2^n?)
+                        */
+                       unsigned_relts_print(ndo, 2147483648U);
+               } else {
+                       /*
+                        * We now know -secs will fit into an int32_t;
+                        * negate it and pass that to unsigned_relts_print().
+                        */
+                       unsigned_relts_print(ndo, -secs);
+               }
+               return;
+       }
+       unsigned_relts_print(ndo, secs);
+}
+
 /*
  *  this is a generic routine for printing unknown data;
  *  we pass on the linefeed plus indentation string to
@@ -870,7 +902,7 @@ safeputs(netdissect_options *ndo,
 {
        u_int idx = 0;
 
-       while (*s && idx < maxlen) {
+       while (idx < maxlen && *s) {
                safeputchar(ndo, *s);
                idx++;
                s++;