[tor-bugs] #4413 [Tor Relay]: Non-triggerable integer overflow in crypto_random_hostname()

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#4413: Non-triggerable integer overflow in crypto_random_hostname()
-----------------------+----------------------------------------------------
 Reporter:  asn        |          Owner:     
     Type:  defect     |         Status:  new
 Priority:  normal     |      Milestone:     
Component:  Tor Relay  |        Version:     
 Keywords:             |         Parent:     
   Points:             |   Actualpoints:     
-----------------------+----------------------------------------------------
 {{{
 char *
 crypto_random_hostname(int min_rand_len, int max_rand_len, const char
 *prefix,
                        const char *suffix)
 ...
   randlen = min_rand_len + crypto_rand_int(max_rand_len - min_rand_len +
 1);
 ...
   rand_bytes_len = ((randlen*5)+7)/8;
   if (rand_bytes_len % 5)
     rand_bytes_len += 5 - (rand_bytes_len%5);
   rand_bytes = tor_malloc(rand_bytes_len);
 }}}

 If `randlen` overflows in `rand_bytes_len = ((randlen*5)+7)/8;` we pass a
 negative value to `tor_malloc()`.

 I don't see this happening any time soon, since  all the currently  used
 crypto_random_hostname() arguments are very small, but it might be good to
 fix it for completeness.

-- 
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/4413>
Tor Bug Tracker & Wiki <https://trac.torproject.org/>
The Tor Project: anonymity online
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