[or-cvs] help avoid overflow from len_in + (len_in/n)*len_ins

[Roger Dingledine]

Update of /home2/or/cvsroot/tor/src/common
In directory moria.mit.edu:/home2/arma/work/onion/cvs/tor/src/common

Modified Files:
	util.c 
Log Message:
help avoid overflow from len_in + (len_in/n)*len_ins
nick, do you think this does it? if so, we should maybe backport too.


Index: util.c
===================================================================
RCS file: /home2/or/cvsroot/tor/src/common/util.c,v
retrieving revision 1.196
retrieving revision 1.197
diff -u -d -r1.196 -r1.197
--- util.c	22 Dec 2004 05:28:15 -0000	1.196
+++ util.c	10 Jan 2005 16:30:51 -0000	1.197
@@ -215,6 +215,8 @@
   tor_assert(dest_len < SIZE_T_CEILING);
   len_in = strlen(s);
   len_ins = strlen(insert);
+  tor_assert(len_in < SIZE_T_CEILING);
+  tor_assert(len_in/n < SIZE_T_CEILING/len_ins); /* avoid overflow */
   len_out = len_in + (len_in/n)*len_ins;
   is_even = (len_in%n) == 0;
   switch (rule)