def __init__(self, msg=None, data=None, filename=None, password=None, vals=None, file_obj=None):
self.p = None
self.q = None
self.g = None
self.y = None
self.x = None
if file_obj is not None:
self._from_private_key(file_obj, password)
return
if filename is not None:
self._from_private_key_file(filename, password)
return
if (msg is None) and (data is not None):
msg = Message(data)
if vals is not None:
self.p, self.q, self.g, self.y = vals
else:
if msg is None:
raise SSHException('Key object may not be empty')
if msg.get_string() != 'ssh-dss':
raise SSHException('Invalid key')
self.p = msg.get_mpint()
self.q = msg.get_mpint()
self.g = msg.get_mpint()
self.y = msg.get_mpint()
self.size = util.bit_length(self.p)
def _parse_modulus(self, line):
timestamp, mod_type, tests, tries, size, generator, modulus = line.split(
)
mod_type = int(mod_type)
tests = int(tests)
tries = int(tries)
size = int(size)
generator = int(generator)
modulus = long(modulus, 16)
# weed out primes that aren't at least:
# type 2 (meets basic structural requirements)
# test 4 (more than just a small-prime sieve)
# tries < 100 if test & 4 (at least 100 tries of miller-rabin)
if (mod_type < 2) or (tests < 4) or ((tests & 4) and (tests < 8) and
(tries < 100)):
self.discarded.append(
(modulus, 'does not meet basic requirements'))
return
if generator == 0:
generator = 2
# there's a bug in the ssh "moduli" file (yeah, i know: shock! dismay!
# call cnn!) where it understates the bit lengths of these primes by 1.
# this is okay.
bl = util.bit_length(modulus)
if (bl != size) and (bl != size + 1):
self.discarded.append(
(modulus, 'incorrectly reported bit length %d' % size))
return
if bl not in self.pack:
self.pack[bl] = []
self.pack[bl].append((generator, modulus))
def _generate_prime(bits, randpool):
"primtive attempt at prime generation"
hbyte_mask = pow(2, bits % 8) - 1
while True:
# loop catches the case where we increment n into a higher bit-range
x = randpool.get_bytes((bits + 7) // 8)
if hbyte_mask > 0:
x = chr(ord(x[0]) & hbyte_mask) + x[1:]
n = util.inflate_long(x, 1)
n |= 1
n |= (1 << (bits - 1))
while not number.isPrime(n):
n += 2
if util.bit_length(n) == bits:
break
return n
def _decode_key(self, data):
# private key file contains:
# RSAPrivateKey = { version = 0, n, e, d, p, q, d mod p-1, d mod q-1, q**-1 mod p }
try:
keylist = BER(data).decode()
except BERException:
raise SSHException('Unable to parse key file')
if (type(keylist)
is not list) or (len(keylist) < 4) or (keylist[0] != 0):
raise SSHException(
'Not a valid RSA private key file (bad ber encoding)')
self.n = keylist[1]
self.e = keylist[2]
self.d = keylist[3]
# not really needed
self.p = keylist[4]
self.q = keylist[5]
self.size = util.bit_length(self.n)
def _parse_kexdh_gex_group(self, m):
self.p = m.get_mpint()
self.g = m.get_mpint()
# reject if p's bit length < 1024 or > 8192
bitlen = util.bit_length(self.p)
if (bitlen < 1024) or (bitlen > 8192):
raise SSHException(
'Server-generated gex p (don\'t ask) is out of range (%d bits)'
% bitlen)
self.transport._log(DEBUG, 'Got server p (%d bits)' % bitlen)
self._generate_x()
# now compute e = g^x mod p
self.e = pow(self.g, self.x, self.p)
m = Message()
m.add_byte(chr(_MSG_KEXDH_GEX_INIT))
m.add_mpint(self.e)
self.transport._send_message(m)
self.transport._expect_packet(_MSG_KEXDH_GEX_REPLY)
def _roll_random(rpool, n):
"returns a random # from 0 to N-1"
bits = util.bit_length(n - 1)
bytes = (bits + 7) // 8
hbyte_mask = pow(2, bits % 8) - 1
# so here's the plan:
# we fetch as many random bits as we'd need to fit N-1, and if the
# generated number is >= N, we try again. in the worst case (N-1 is a
# power of 2), we have slightly better than 50% odds of getting one that
# fits, so i can't guarantee that this loop will ever finish, but the odds
# of it looping forever should be infinitesimal.
while True:
x = rpool.get_bytes(bytes)
if hbyte_mask > 0:
x = chr(ord(x[0]) & hbyte_mask) + x[1:]
num = util.inflate_long(x, 1)
if num < n:
break
return num
class DSSKey (PKey):
"""
Representation of a DSS key which can be used to sign an verify SSH2
data.
"""
def __init__(self, msg=None, data=None, filename=None, password=None, vals=None, file_obj=None):
self.p = None
self.q = None
self.g = None
self.y = None
self.x = None
if file_obj is not None:
self._from_private_key(file_obj, password)
return
if filename is not None:
self._from_private_key_file(filename, password)
return
if (msg is None) and (data is not None):
msg = Message(data)
if vals is not None:
self.p, self.q, self.g, self.y = vals
else:
if msg is None:
raise SSHException('Key object may not be empty')
if msg.get_string() != 'ssh-dss':
raise SSHException('Invalid key')
self.p = msg.get_mpint()
self.q = msg.get_mpint()
self.g = msg.get_mpint()
self.y = msg.get_mpint()
self.size = util.bit_length(self.p)
def __str__(self):
m = Message()
m.add_string('ssh-dss')
m.add_mpint(self.p)
m.add_mpint(self.q)
m.add_mpint(self.g)
m.add_mpint(self.y)
return str(m)
def __hash__(self):
h = hash(self.get_name())
h = h * 37 + hash(self.p)
h = h * 37 + hash(self.q)
h = h * 37 + hash(self.g)
h = h * 37 + hash(self.y)
# h might be a long by now...
return hash(h)
def get_name(self):
return 'ssh-dss'
def get_bits(self):
return self.size
def can_sign(self):
return self.x is not None
def sign_ssh_data(self, rpool, data):
digest = SHA.new(data).digest()
dss = DSA.construct((long(self.y), long(self.g), long(self.p), long(self.q), long(self.x)))
# generate a suitable k
qsize = len(util.deflate_long(self.q, 0))
while True:
k = util.inflate_long(rpool.get_bytes(qsize), 1)
if (k > 2) and (k < self.q):
break
r, s = dss.sign(util.inflate_long(digest, 1), k)
m = Message()
m.add_string('ssh-dss')
# apparently, in rare cases, r or s may be shorter than 20 bytes!
rstr = util.deflate_long(r, 0)
sstr = util.deflate_long(s, 0)
if len(rstr) < 20:
rstr = '\x00' * (20 - len(rstr)) + rstr
if len(sstr) < 20:
sstr = '\x00' * (20 - len(sstr)) + sstr
m.add_string(rstr + sstr)
return m
def verify_ssh_sig(self, data, msg):
if len(str(msg)) == 40:
# spies.com bug: signature has no header
sig = str(msg)
else:
kind = msg.get_string()
if kind != 'ssh-dss':
return 0
sig = msg.get_string()
# pull out (r, s) which are NOT encoded as mpints
sigR = util.inflate_long(sig[:20], 1)
sigS = util.inflate_long(sig[20:], 1)
sigM = util.inflate_long(SHA.new(data).digest(), 1)
dss = DSA.construct((long(self.y), long(self.g), long(self.p), long(self.q)))
return dss.verify(sigM, (sigR, sigS))
def _encode_key(self):
if self.x is None:
raise SSHException('Not enough key information')
keylist = [ 0, self.p, self.q, self.g, self.y, self.x ]
try:
b = BER()
b.encode(keylist)
except BERException:
raise SSHException('Unable to create ber encoding of key')
return str(b)
def write_private_key_file(self, filename, password=None):
self._write_private_key_file('DSA', filename, self._encode_key(), password)
def write_private_key(self, file_obj, password=None):
self._write_private_key('DSA', file_obj, self._encode_key(), password)
def generate(bits=1024, progress_func=None):
"""
Generate a new private DSS key. This factory function can be used to
generate a new host key or authentication key.
@param bits: number of bits the generated key should be.
@type bits: int
@param progress_func: an optional function to call at key points in
key generation (used by C{pyCrypto.PublicKey}).
@type progress_func: function
@return: new private key
@rtype: L{DSSKey}
"""
randpool.stir()
dsa = DSA.generate(bits, randpool.get_bytes, progress_func)
key = DSSKey(vals=(dsa.p, dsa.q, dsa.g, dsa.y))
key.x = dsa.x
return key
generate = staticmethod(generate)
### internals...
def _from_private_key_file(self, filename, password):
data = self._read_private_key_file('DSA', filename, password)
self._decode_key(data)
def _from_private_key(self, file_obj, password):
data = self._read_private_key('DSA', file_obj, password)
self._decode_key(data)
def _decode_key(self, data):
# private key file contains:
# DSAPrivateKey = { version = 0, p, q, g, y, x }
try:
keylist = BER(data).decode()
except BERException, x:
raise SSHException('Unable to parse key file: ' + str(x))
if (type(keylist) is not list) or (len(keylist) < 6) or (keylist[0] != 0):
raise SSHException('not a valid DSA private key file (bad ber encoding)')
self.p = keylist[1]
self.q = keylist[2]
self.g = keylist[3]
self.y = keylist[4]
self.x = keylist[5]
self.size = util.bit_length(self.p)