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"""
M2Crypto wrapper for OpenSSL DSA API.
Copyright (c) 1999-2003 Ng Pheng Siong. All rights reserved.
Portions created by Open Source Applications Foundation (OSAF) are
Copyright (C) 2004 OSAF. All Rights Reserved.
"""
import sys
import util, BIO, m2
class DSAError(Exception): pass
m2.dsa_init(DSAError)
class DSA:
"""
This class is a context supporting DSA key and parameter
values, signing and verifying.
Simple example:
from M2Crypto import EVP, DSA, util
message = 'Kilroy was here!'
md = EVP.MessageDigest('sha1')
md.update(message)
digest = md.final()
dsa = DSA.gen_params(1024)
dsa.gen_key()
r, s = dsa.sign(digest)
good = dsa.verify(digest, r, s)
if good:
print ' ** success **'
else:
print ' ** verification failed **'
"""
m2_dsa_free = m2.dsa_free
def __init__(self, dsa, _pyfree=0):
"""
Use one of the factory functions to create an instance.
"""
assert m2.dsa_type_check(dsa), "'dsa' type error"
self.dsa = dsa
self._pyfree = _pyfree
def __del__(self):
if getattr(self, '_pyfree', 0):
self.m2_dsa_free(self.dsa)
def __len__(self):
"""
Return the key length.
@rtype: int
@return: the DSA key length in bits
"""
assert m2.dsa_type_check(self.dsa), "'dsa' type error"
return m2.dsa_keylen(self.dsa)
def __getattr__(self, name):
"""
Return specified DSA parameters and key values.
@type name: str
@param name: name of variable to be returned. Must be
one of 'p', 'q', 'g', 'pub', 'priv'.
@rtype: str
@return: value of specified variable (a "byte string")
"""
if name in ['p', 'q', 'g', 'pub', 'priv']:
method = getattr(m2, 'dsa_get_%s' % (name,))
assert m2.dsa_type_check(self.dsa), "'dsa' type error"
return method(self.dsa)
else:
raise AttributeError
def __setattr__(self, name, value):
if name in ['p', 'q', 'g']:
raise DSAError('set (p, q, g) via set_params()')
elif name in ['pub','priv']:
raise DSAError('generate (pub, priv) via gen_key()')
else:
self.__dict__[name] = value
def set_params(self, p, q, g):
"""
Set new parameters.
@warning: This does not change the private key, so it may be
unsafe to use this method. It is better to use
gen_params function to create a new DSA object.
"""
m2.dsa_set_p(self.dsa, p)
m2.dsa_set_q(self.dsa, q)
m2.dsa_set_g(self.dsa, g)
def gen_key(self):
"""
Generate a key pair.
"""
assert m2.dsa_type_check(self.dsa), "'dsa' type error"
m2.dsa_gen_key(self.dsa)
def save_params(self, filename):
"""
Save the DSA parameters to a file.
@type filename: str
@param filename: Save the DSA parameters to this file.
@return: 1 (true) if successful
"""
bio = BIO.openfile(filename, 'wb')
ret = m2.dsa_write_params_bio(self.dsa, bio._ptr())
bio.close()
return ret
def save_params_bio(self, bio):
"""
Save DSA parameters to a BIO object.
@type bio: M2Crypto.BIO object
@param bio: Save DSA parameters to this object.
@return: 1 (true) if successful
"""
return m2.dsa_write_params_bio(self.dsa, bio._ptr())
def save_key(self, filename, cipher='aes_128_cbc',
callback=util.passphrase_callback):
"""
Save the DSA key pair to a file.
@type filename: str
@param filename: Save the DSA key pair to this file.
@type cipher: str
@param cipher: name of symmetric key algorithm and mode
to encrypt the private key.
@return: 1 (true) if successful
"""
bio = BIO.openfile(filepath, 'wb')
ret = self.save_key_bio(bio, cipher, callback)
bio.close()
return ret
def save_key_bio(self, bio, cipher='aes_128_cbc',
callback=util.passphrase_callback):
"""
Save DSA key pair to a BIO object.
@type bio: M2Crypto.BIO object
@param bio: Save DSA parameters to this object.
@type cipher: str
@param cipher: name of symmetric key algorithm and mode
to encrypt the private key.
@return: 1 (true) if successful
"""
if cipher is None:
return m2.dsa_write_key_bio_no_cipher(self.dsa,
bio._ptr(), callback)
else:
ciph = getattr(m2, cipher, None)
if ciph is None:
raise DSAError('no such cipher: %s' % cipher)
else:
ciph = ciph()
return m2.dsa_write_key_bio(self.dsa, bio._ptr(), ciph, callback)
def save_pub_key(self, filename):
"""
Save the DSA public key (with parameters) to a file.
@type filename: str
@param filename: Save DSA public key (with parameters)
to this file.
@return: 1 (true) if successful
"""
bio = BIO.openfile(filepath, 'wb')
ret = self.save_pub_key_bio(bio)
bio.close()
return ret
def save_pub_key_bio(self, bio):
"""
Save DSA public key (with parameters) to a BIO object.
@type bio: M2Crypto.BIO object
@param bio: Save DSA public key (with parameters)
to this object.
@return: 1 (true) if successful
"""
return m2.dsa_write_pub_key_bio(self.dsa, bio._ptr())
def sign(self, digest):
"""
Sign the digest.
@type digest: str
@param digest: SHA-1 hash of message (same as output
from MessageDigest, a "byte string")
@rtype: tuple
@return: DSA signature, a tuple of two values, r and s,
both "byte strings".
"""
assert self.check_key(), 'key is not initialised'
return m2.dsa_sign(self.dsa, digest)
def verify(self, digest, r, s):
"""
Verify a newly calculated digest against the signature
values r and s.
@type digest: str
@param digest: SHA-1 hash of message (same as output
from MessageDigest, a "byte string")
@type r: str
@param r: r value of the signature, a "byte string"
@type s: str
@param s: s value of the signature, a "byte string"
@rtype: int
@return: 1 (true) if verify succeeded, 0 if failed
"""
assert self.check_key(), 'key is not initialised'
return m2.dsa_verify(self.dsa, digest, r, s)
def sign_asn1(self, digest):
assert self.check_key(), 'key is not initialised'
return m2.dsa_sign_asn1(self.dsa, digest)
def verify_asn1(self, digest, blob):
assert self.check_key(), 'key is not initialised'
return m2.dsa_verify_asn1(self.dsa, digest, blob)
def check_key(self):
"""
Check to be sure the DSA object has a valid private key.
@rtype: int
@return: 1 (true) if a valid private key
"""
assert m2.dsa_type_check(self.dsa), "'dsa' type error"
return m2.dsa_check_key(self.dsa)
class DSA_pub(DSA):
"""
This class is a DSA context that only supports a public key
and verification. It does NOT support a private key or
signing.
"""
def sign(self, *argv):
raise DSAError('DSA_pub object has no private key')
sign_asn1 = sign
def check_key(self):
return m2.dsa_check_pub_key(self.dsa)
save_key = DSA.save_pub_key
save_key_bio = DSA.save_pub_key_bio
#---------------------------------------------------------------
# factories and other functions
def gen_params(bits, callback=util.genparam_callback):
"""
Factory function that generates DSA parameters and
instantiates a DSA object from the output.
@type bits: int
@param bits: The length of the prime to be generated. If
'bits' < 512, it is set to 512.
@type callback: function
@param callback: A Python callback object that will be
invoked during parameter generation; it usual
purpose is to provide visual feedback.
@rtype: DSA
@return: instance of DSA.
"""
dsa = m2.dsa_generate_parameters(bits, callback)
if dsa is None:
raise DSAError('problem generating DSA parameters')
return DSA(dsa, 1)
def set_params(p, q, g):
"""
Factory function that instantiates a DSA object with DSA
parameters.
@type p: str
@param p: value of p, a "byte string"
@type q: str
@param q: value of q, a "byte string"
@type g: str
@param g: value of g, a "byte string"
@rtype: DSA
@return: instance of DSA.
"""
dsa = m2.dsa_new()
m2.dsa_set_p(dsa, p)
m2.dsa_set_q(dsa, q)
m2.dsa_set_g(dsa, g)
return DSA(dsa, 1)
def load_params(file, callback=util.passphrase_callback):
"""
Factory function that instantiates a DSA object with DSA
parameters from a file.
@type file: str
@param file: Names the file (a path) that contains the PEM
representation of the DSA parameters.
@type callback: A Python callable
@param callback: A Python callback object that will be
invoked if the DSA parameters file is
passphrase-protected.
@rtype: DSA
@return: instance of DSA.
"""
bio = BIO.openfile(file)
ret = load_params_bio(bio, callback)
bio.close()
return ret
def load_params_bio(bio, callback=util.passphrase_callback):
"""
Factory function that instantiates a DSA object with DSA
parameters from a M2Crypto.BIO object.
@type bio: M2Crypto.BIO object
@param bio: Contains the PEM representation of the DSA
parameters.
@type callback: A Python callable
@param callback: A Python callback object that will be
invoked if the DSA parameters file is
passphrase-protected.
@rtype: DSA
@return: instance of DSA.
"""
dsa = m2.dsa_read_params(bio._ptr(), callback)
if dsa is None:
raise DSAError('problem loading DSA parameters')
return DSA(dsa, 1)
def load_key(file, callback=util.passphrase_callback):
"""
Factory function that instantiates a DSA object from a
PEM encoded DSA key pair.
@type file: str
@param file: Names the file (a path) that contains the PEM
representation of the DSA key pair.
@type callback: A Python callable
@param callback: A Python callback object that will be
invoked if the DSA key pair is
passphrase-protected.
@rtype: DSA
@return: instance of DSA.
"""
bio = BIO.openfile(file)
ret = load_key_bio(bio, callback)
bio.close()
return ret
def load_key_bio(bio, callback=util.passphrase_callback):
"""
Factory function that instantiates a DSA object from a
PEM encoded DSA key pair.
@type bio: M2Crypto.BIO object
@param bio: Contains the PEM representation of the DSA
key pair.
@type callback: A Python callable
@param callback: A Python callback object that will be
invoked if the DSA key pair is
passphrase-protected.
@rtype: DSA
@return: instance of DSA.
"""
dsa = m2.dsa_read_key(bio._ptr(), callback)
if not dsa:
raise DSAError('problem loading DSA key pair')
return DSA(dsa, 1)
def load_pub_key(file, callback=util.passphrase_callback):
"""
Factory function that instantiates a DSA_pub object using
a DSA public key contained in PEM file. The PEM file
must contain the parameters in addition to the public key.
@type file: str
@param file: Names the file (a path) that contains the PEM
representation of the DSA public key.
@type callback: A Python callable
@param callback: A Python callback object that will be
invoked should the DSA public key be
passphrase-protected.
@rtype: DSA_pub
@return: instance of DSA_pub.
"""
bio = BIO.openfile(file)
ret = load_pub_key_bio(bio, callback)
bio.close()
return ret
def load_pub_key_bio(bio, callback=util.passphrase_callback):
"""
Factory function that instantiates a DSA_pub object using
a DSA public key contained in PEM format. The PEM
must contain the parameters in addition to the public key.
@type bio: M2Crypto.BIO object
@param bio: Contains the PEM representation of the DSA
public key (with params).
@type callback: A Python callable
@param callback: A Python callback object that will be
invoked should the DSA public key be
passphrase-protected.
@rtype: DSA_pub
@return: instance of DSA_pub.
"""
dsapub = m2.dsa_read_pub_key(bio._ptr(), callback)
if not dsapub:
raise DSAError('problem loading DSA public key')
return DSA_pub(dsapub, 1)
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