[Savannah-hackers] Re: lsh dying

[Niels Möller]

Loic Dachary <address@hidden> writes:

> Sep 10 10:24:19 subversions lshd[31748]: io.c: accept on fd 4
> Sep 10 10:24:19 subversions lshd[31748]: Accepting connection from 
> 195.149.37.160, port 42154
> Sep 10 10:24:19 subversions lshd[31748]: Initiating handshake with 
> 195.149.37.160
> Sep 10 10:24:19 subversions lshd[31748]: io.c: Preparing fd 4 for reading and 
> writing
> Sep 10 10:24:19 subversions lshd[31748]: Client version: SSH-2.0-lsh_1.1.5 
> lsh - a free ssh Server version: SSH-1.99-lshd_1.2.1 lsh - a free ssh
> Sep 10 10:24:19 subversions lshd[31748]: Selected keyexchange algorithm: 
> diffie-hellman-group1-sha1   with hostkey algorithm:       ssh-dss
> Sep 10 10:24:19 subversions lshd[31748]: Selected bulk algorithms: (client to 
> server, server to client)   Encryption:             (3des-cbc, 3des-cbc)   
> Message authentication: (hmac-sha1, hmac-sha1)   Compression:            
> (none, none)
> Sep 10 10:24:19 subversions lshd[31748]: handle_dh_init
> Sep 10 10:24:19 subversions lshd[31748]: do_dsa_sign: Signing according to 
> ssh-dss

Thanks for the info. Does it happen randomly, or is there any pattern?

One hypothesis is that the dsa_blob_write crashes in some unusual
case, e.g. if r and s are of different size.

Could you try dumping out the values of r and s in dsa signatures?
If you change a few debug() calls to trace(), you will get the info
with --trace, without enabling full packet dumps with --debug.

--- src/dsa.c   2001/06/11 23:06:03     1.28
+++ src/dsa.c   2001/09/11 11:35:16
@@ -435,7 +435,7 @@

   mpz_fdiv_r(r, r, self->verifier->q);

-  debug("generic_dsa_sign, r: %xn\n", r);
+  trace("generic_dsa_sign, r: %xn\n", r);

   /* Compute hash */
   dsa_hash(tmp, length, msg);
@@ -453,7 +453,7 @@
   mpz_mul(s, s, k);
   mpz_fdiv_r(s, s, self->verifier->q);

-  debug("generic_dsa_sign, s: %xn\n", s);
+  trace("generic_dsa_sign, s: %xn\n", s);

   mpz_clear(k);
   mpz_clear(tmp);

And of course, a core dump from a crash would also be helpful.

/Niels