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from __future__ import with_statement
'''
Created on Jul 20, 2011
@author: steger
'''
from M2Crypto import RSA
from base64 import b64encode
from os import chmod, path
import stat
# paramiko provides this functionality, so maybe we don't need this class. see paramiko.PKey
class CannotSet(Exception):
pass
class SshKeygen(object):
'''
Generates a pair of RSA keys.
Enables saving the keys to the file system.
'''
def __init__(self, bits = 1024, e = 65337):
'''
Initiates the pair of RSA keys
@param bits: the length of the keys in bits
@type bits: integer
@param e: the exponent
@type e: integer
'''
self.rsa = RSA.gen_key(bits, e, lambda: None)
def _check_filename(self, filename):
if path.exists(filename):
raise Exception("File exists: %s" % filename)
def _get_private(self):
'''
@summary: return the private key in PEM format
@return: the private key in PEM format
@rtype: string
'''
return self.rsa.as_pem(cipher = None)
def _set_private(self, value):
raise CannotSet
def _del_private(self):
raise CannotSet
@staticmethod
def _convert(rsa):
return b64encode('\x00\x00\x00\x07ssh-rsa%s%s' % (rsa.pub()[0], rsa.pub()[1]))
def _get_public(self):
'''
@summary: return the public key in base64 format conforming to the content of authorized_keys
@return: the public key in base64 format
@rtype: string
'''
return self._convert(self.rsa)
def _set_public(self, value):
raise CannotSet
def _del_public(self):
raise CannotSet
def save_private_key(self, filename):
'''
@summary: save the private key in the file system in a named file.
@param filename: the filename to store the private key.
@type filename: string
'''
self._check_filename(filename)
self.rsa.save_key(filename, cipher = None)
chmod(filename, stat.S_IRUSR)
def save_public_key(self, filename):
'''
@summary: save the public key in the file system in a named file.
@param filename: the filename to store the public key.
@type filename: string
'''
self._check_filename(filename)
with open(filename, "w") as f:
f.write("ssh-rsa %s" % self.public)
@staticmethod
def convert_key_from_file(filename):
'''
@summary: convert a private key stored in a file in PEM format and return the public key in base64 format conforming to the content of authorized_keys
@return: the public key in base64 format
@rtype: string
'''
return SshKeygen._convert( RSA.load_key(file = filename) )
public = property(_get_public,_set_public,_del_public)
private = property(_get_private,_set_private,_del_private)
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