def __init__(self, key):
"""@param key the ASCII string from id_rsa.pub from ssh-keygen"""
if key.startswith("ssh-rsa"):
self.decoded = key.split(" ")[1]
self.encoded = base64.b64decode(self.decoded)
else:
self.encoded = key
self.decoded = base64.b64encode(self.encoded)
self.fp = hashlib.sha1(self.encoded).digest()[:6]
fields = read_fields(self.encoded)
sigtype = fields.next()
if sigtype != "ssh-rsa":
raise exceptions.KeyError("Unknown key type %s. This code "
"currently only supports ssh-rsa" %
sigtype)
self.exp = _str_to_int(fields.next())
self.mod = _str_to_int(fields.next())
# it turns out that ssh writes leading zeroes, which we get rid of
# by roundtripping to bignum.
self.mod_size = len(_int_to_str(self.mod))
def encrypt(self, data):
if len(data) > self.mod_size:
raise exceptions.KeyError("Key size too small, more than %d bytes "
"of data can not be encrypted" %
self.mod_size)
return _int_to_str(pow(_str_to_int(data), self.private_exp, self.mod))