[pycrypto] ERROR: testRsaUnversionedSignAndVerify failed

[Hans-Peter Jansen]

Hi Sébastien, hi Steve,

first of all, thanks for the instant feedback.

Am Donnerstag, 20. August 2009 schrieb Sébastien Martini:
> Hi Hans-Peter,
>
> > /usr/lib/python2.6/site-packages/Crypto/Hash/SHA.py:6:
> > DeprecationWarning: the sha module is deprecated; use the hashlib
> > module instead
> >   from sha import *
>
> Strange, with pycrypto 2.0.1 on Ubuntu 9.04 (and with Python 2.6.1) I
> do not have this warning. Are you sure your system use pycrypto
> 2.0.1 ?

Yes, I am:
$ rpm -qf /usr/lib/python2.6/site-packages/Crypto/PublicKey/RSA.py
python-crypto-2.0.1-28.115.1

Let me note, that I always generate rpm packages (at least with "python 
setup.py bdist_rpm"), rather then installing from source directly. 

Probably, Ubuntu incorporates some patches from Dwaynes trunk, does it?
I got rid of the Deprecation warning with updating to Dwaynes version, by 
the price of a new one. See below.

Please let me turn around the question: are you sure, that Ubuntus version 
isn't a hybrid of Andrews and Dwaynes at least? May I ask you to show me 
your patches? I show you mine ;-)

openSUSE incorporated two patches to 2.0.1:

This one, I ported to trunk:
--- src/hash_template.c~	2009-08-16 23:39:34.053841534 +0200
+++ src/hash_template.c	2009-08-20 10:16:05.877840748 +0200
@@ -111,13 +111,15 @@ ALG_hexdigest(ALGobject *self, PyObject
 	PyObject *value, *retval;
 	unsigned char *raw_digest, *hex_digest;
 	int i, j, size;
+	Py_ssize_t ssize;
 
 	if (!PyArg_ParseTuple(args, ""))
 		return NULL;
 
 	/* Get the raw (binary) digest value */
 	value = (PyObject *)hash_digest(&(self->st));
-	size = PyString_Size(value);
+	ssize = PyString_Size(value);
+	size = (ssize > INT_MAX) ? INT_MAX : ssize;
 	raw_digest = (unsigned char *) PyString_AsString(value);
 
 	/* Create a new string */

Dwayne, is this in order or just plain silly?

The other is the already applied ARC2 fix to check of oversized keys.

> > ............................E.
> > ======================================================================
> > ERROR: testRsaUnversionedSignAndVerify (signer_test.SignerTest)
> > ----------------------------------------------------------------------
> > Traceback (most recent call last):
> >   File ".../keyczar/tests/keyczar/signer_test.py", line 125, in
> > testRsaUnversionedSignAndVerify
> > self.__testUnversionedSignAndVerify("rsa-sign")
> >   File ".../keyczar/tests/keyczar/signer_test.py", line 67, in
> > __testUnversionedSignAndVerify
> > self.assertFalse(unversioned_signer.Verify("Wrong string", sig)) File
> > "/usr/local/lib/python2.6/site-packages/keyczar/keyczar.py", line 404,
> > in Verify result = key.Verify(data, sig_bytes)
> >   File "/usr/local/lib/python2.6/site-packages/keyczar/keys.py", line
> > 622, in Verify return self.public_key.Verify(msg, sig)
> >   File "/usr/local/lib/python2.6/site-packages/keyczar/keys.py", line
> > 787, in Verify (util.BytesToLong(sig),))
> >   File "/usr/lib/python2.6/site-packages/Crypto/PublicKey/pubkey.py",
> > line 84, in verify return self._verify(M, signature)
> >   File "/usr/lib/python2.6/site-packages/Crypto/PublicKey/RSA.py", line
> > 103, in _verify m2=self._encrypt(sig[0])
> >   File "/usr/lib/python2.6/site-packages/Crypto/PublicKey/RSA.py", line
> > 89, in _encrypt raise error, 'Plaintext too large'
> > error: Plaintext too large
>
> I think this error is related somehow to the hash computation (which
> also could be related to the deprecation warning) because this is the
> hash value which is signed with a private_encrypt() RSA method. I
> might be wrong but I really think this is not currently pycrypto 2.0.1
> that your keyczar install calls.

No, it _wasn't_ related to SHA.py, since in a first test, I just updated to 
Dwaynes current SHA.py, which tries to import hashlib.SHA first and got rid 
of the deprecation, but this error persisted. 

After updating my python-crypto package to Dwaynes trunk, the tests 
succeeded:

$ python alltests.py 
./usr/lib/python2.6/site-packages/Crypto/Util/randpool.py:72: 
RandomPool_DeprecationWarning: RandomPool is deprecated.  Use Random.new() 
or Random.RandomPoolCompat instead.
  warnings.warn("RandomPool is deprecated.  Use Random.new() or 
Random.RandomPoolCompat instead.", RandomPool_DeprecationWarning)
.............................
----------------------------------------------------------------------
Ran 30 tests in 1.010s

OK

I fixed it with this patch:

--- util.py.orig	2009-08-20 10:40:19.248702303 +0200
+++ util.py	2009-08-20 10:57:27.765198430 +0200
@@ -30,7 +30,12 @@ except ImportError:
   from sha import sha as sha1
   from Crypto.Hash.SHA256 import new as sha256
 
-from Crypto.Util import randpool
+try:
+  # Import RandomPoolCompat, if available
+  from Crypto.Random import RandomPoolCompat as RandomPool
+except ImportError:
+  from Crypto.Util.randpool import RandomPool
+
 from pyasn1.codec.der import decoder
 from pyasn1.codec.der import encoder
 from pyasn1.type import univ
@@ -291,7 +296,7 @@ def TrimBytes(bytes):
 
 def RandBytes(n):
   """Return n random bytes."""
-  return randpool.RandomPool(512).get_bytes(n)
+  return RandomPool(512).get_bytes(n)
 
 def Hash(digest, *inputs):
   """Return a SHA-1 hash over a variable number of inputs."""

BTW, is there any reason to fetch 512 bytes always, and use a subset only 
(if I read the code correctly)? What happens, if n is > 512?

> > ----------------------------------------------------------------------
> > Ran 30 tests in 3.179s
> >
> > FAILED (errors=1)
> >
> > Since I wanted to use RSA signing and encryption, I'm concerned about
> > it.
> >
> > System:
> > openSUSE 11.1, python 2.6.0, python-crypto-2.0.1, pyasn1-0.0.8a
>
> Cordially,
>
> Sébastien

Thanks,
Pete