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Date: Thu, 24 Jan 2013 21:38:58 +0530
From: Dhiru Kholia <dhiru.kholia@...il.com>
To: john-dev@...ts.openwall.com
Subject: Re: Formats ssh and ssh-ng
On Thu, Jan 24, 2013 at 8:50 PM, Frank Dittrich
<frank_dittrich@...mail.com> wrote:
> I think ssh and/or ssh-ng formats need at least some documentation, but
> preferably even some code changes.
Good point. I can quickly write a "README.ssh" file explaining the
usage of and the difference between these two formats.
> $ ./sshng2john.py id_rsa > sshng-test
>
> (BTW: I had to install python-crypto on Fedora 18 to make the script work.)
Can you please test the following patch to see if it makes things better?
diff --git a/run/sshng2john.py b/run/sshng2john.py
index 12a6f60..b08a85e 100755
--- a/run/sshng2john.py
+++ b/run/sshng2john.py
@@ -31,10 +31,16 @@ from hashlib import md5 as MD5
limited = False
+
+class Object(object):
+ pass
+
try:
- from Crypto.Cipher import DES3, AES
+ from Crypto.Cipher import DES3, AES1
except ImportError:
print >> sys.stderr, "PyCrypto is missing in your Python
installation, %s is operating is limited features mode!" % sys.argv[0]
+ AES = Object()
+ AES.MODE_CBC = ""
limited = True
@@ -639,7 +645,8 @@ class PKey (object):
if 'proc-type' not in headers:
# unencryped: done
- return data
+ print >> sys.stderr, "%s has no password!" % f.name
+ return None
# encrypted keyfile: will need a password
if headers['proc-type'] != '4,ENCRYPTED':
raise SSHException('Unknown private key structure "%s"' %
headers['proc-type'])
@@ -674,7 +681,7 @@ class PKey (object):
return ddata
except ValueError: # incorrect password
return data
- return None
+ return self.hash # dummy value
def chunks(l, n):
@@ -717,6 +724,8 @@ class RSADSSKey (PKey):
def _from_private_key_file(self, filename, password):
data = self._read_private_key_file('RSA', filename, password)
+ if not data:
+ return
if limited:
print self.hash
return
> Apparently, both formats are able to crack the same input file after
> converting it using the right tool. But ssh-ng is much faster.
Yes, ssh-ng is fast :-)
> Why does ssh-ng have the "False positives possible" flag set?
ssh-ng does partial decryption and partial ASN decoding, hence it can
have false positives.
> If ssh can avoid false positives, ssh-ng should be able to avoid false
> positives as well, no?
You are right. We can have a 100% solid verification check in ssh-ng
format as well (and then remove FMT_NOT_EXACT from ssh-ng format).
> This:
> $ ls -l ssh*test
> -rw-rw-r--. 1 fd fd 2425 Jan 24 15:51 sshng-test
> -rw-rw-r--. 1 fd fd 3505 Jan 24 15:51 ssh-test
> doesn't look like ssh2john is extracting less information from the
> keyfile than sshng2john is.
> So, shouldn't ssh-ng be able to "understand" and convert $ssh2$ hashes?
> What about ssh understanding the $sshng$ hashes?
IMO, we only care about ssh-ng being able to "understand" old-style
$ssh2$ hashes. Yes, this is possible and at some point I might have
promised Solar to implement such a feature ;)
> Why do we even need two different tags?
> Why different format names?
ssh format is well tested and been proven to work whereas ssh-ng is
highly experimental (but faster). So both formats currently co-exist.
> Can't ssh-ng report "SSH RSA / DSA" instead of "ssh-ng SSH RSA / DSA"?
> This would allow to pick the fastest of several benchmarks for
> performance comparison in relbench.
> (Of course, the format name should only be changed if both formats
> understand the same canonical hash representation and if ssh-ng doesn't
> produce false positives.)
ssh-ng *might* produce false positives (but it hasn't so far!) and
making ssh-ng understand old-style hashes requires more work (i.e.
patches welcome).
Hence, for now, it is better to treat them as separate formats.
> What am I missing here?
I hope that I have answered your questions. Thanks for the feedback.
--
Dhiru
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