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#!/usr/bin/python
from message import Message
from transport import MSG_USERAUTH_REQUEST
from Crypto.PublicKey import RSA
from Crypto.Hash import SHA
from ber import BER
from util import format_binary, inflate_long, deflate_long
import base64
class RSAKey(object):
def __init__(self, msg=None):
self.valid = 0
if (msg == None) or (msg.get_string() != 'ssh-rsa'):
return
self.e = msg.get_mpint()
self.n = msg.get_mpint()
self.size = len(deflate_long(self.n, 0))
self.valid = 1
def __str__(self):
if not self.valid:
return ''
m = Message()
m.add_string('ssh-rsa')
m.add_mpint(self.e)
m.add_mpint(self.n)
return str(m)
def get_name(self):
return 'ssh-rsa'
def get_fingerprint(self):
return MD5.new(str(self)).digest()
def pkcs1imify(self, data):
"""
turn a 20-byte SHA1 hash into a blob of data as large as the key's N,
using PKCS1's \"emsa-pkcs1-v1_5\" encoding. totally bizarre.
"""
SHA1_DIGESTINFO = '\x30\x21\x30\x09\x06\x05\x2b\x0e\x03\x02\x1a\x05\x00\x04\x14'
filler = '\xff' * (self.size - len(SHA1_DIGESTINFO) - len(data) - 3)
return '\x00\x01' + filler + '\x00' + SHA1_DIGESTINFO + data
def verify_ssh_sig(self, data, msg):
if (not self.valid) or (msg.get_string() != 'ssh-rsa'):
return 0
sig = inflate_long(msg.get_string(), 1)
# verify the signature by SHA'ing the data and encrypting it using the
# public key. some wackiness ensues where we "pkcs1imify" the 20-byte
# hash into a string as long as the RSA key.
hash = inflate_long(self.pkcs1imify(SHA.new(data).digest()), 1)
rsa = RSA.construct((long(self.n), long(self.e)))
return rsa.verify(hash, (sig,))
def sign_ssh_data(self, randpool, data):
hash = SHA.new(data).digest()
rsa = RSA.construct((long(self.n), long(self.e), long(self.d)))
sig = deflate_long(rsa.sign(self.pkcs1imify(hash), '')[0], 0)
m = Message()
m.add_string('ssh-rsa')
m.add_string(sig)
return str(m)
def read_private_key_file(self, filename):
"throws a file exception, or SSHException (on invalid key), or base64 decoding exception"
# private key file contains:
# RSAPrivateKey = { version = 0, n, e, d, p, q, d mod p-1, d mod q-1, q**-1 mod p }
self.valid = 0
f = open(filename, 'r')
lines = f.readlines()
f.close()
if lines[0].strip() != '-----BEGIN RSA PRIVATE KEY-----':
raise SSHException('not a valid DSA private key file')
data = base64.decodestring(''.join(lines[1:-1]))
keylist = BER(data).decode()
if (type(keylist) != type([])) or (len(keylist) < 4) or (keylist[0] != 0):
raise SSHException('not a valid DSA 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 = len(deflate_long(self.n, 0))
self.valid = 1
def sign_ssh_session(self, randpool, sid, username):
m = Message()
m.add_string(sid)
m.add_byte(chr(MSG_USERAUTH_REQUEST))
m.add_string(username)
m.add_string('ssh-connection')
m.add_string('publickey')
m.add_boolean(1)
m.add_string('ssh-rsa')
m.add_string(str(self))
return self.sign_ssh_data(randpool, str(m))
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