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README
ssh_decoder.rb

README

ssh_decoder v1.0

This tool can decipher captured SSH sessions where one of the two ends uses a vulnerable OpenSSL (debian OpenSSL PRNG vuln).

You will need ssh_kex_keygen (>= 1.1) to recover the DH shared secret.

How to use :
	- get a capture (PCAP)
	- use tcpick -wRC -wRS session.pcap 
	- ruby ssh_decoder.rb *.dat
	- ???
	- profit.

Common options (in fact ssh_kex_keygen options, see its README) :
	-v : verbose (dump all ssh packets)
	-s : consider the server as vulnerable (default)
	-c : consider the client as vulnerable
	-n : number of processes to bruteforce with (number of CPUs of your machine)

Example session :
$ ruby ssh_decoder.rb data/full_openssh*.dat -n 4
 * read handshake
cipher: aes128-cbc, mac: hmac-md5, kex_hash: sha1, compr: none
 * bruteforce DH
DH shared secret : 00c1eb39032ffcbfded4fd74b6884027419944dd72f5f2ca7acaec6ac7f4b46bb66765fd0ca073c1ccb6e7ec9cd8be91560f907818097c240e44b26025cdfd307298db51420da8793750da008233b92ac68e32d619cf739b1a8d31add5a787217741b7e6436eaf0fb4a33054f30f0d07cf571c24d583a6ed53fafe849203d82bd1
 * derive keys
 * decipher streams
 * successful authentication packet
{:change=>0,
 :password=>"toto",
 :username=>"toto",
 :nextservice=>"ssh-connection",
 :auth_method=>"password"}
 * deciphered streams saved to "sshdecrypt.0.client.dat" & "sshdecrypt.0.server.dat"


Known limitations :
	- A few exotic ciphers are not implemented (quite unlikely to be used)
	- Communications without group exchange (eg dropbear server) are not supported, but
	  shouldn't be hard to add (opensource at its best)
	- Compression support is not tested, but should work
	- `first_kex_follows' field ignored

Contact : 
Raphaël Rigo : devel-ssh _!at!_ syscall.eu
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