339 lines
13 KiB
Python
339 lines
13 KiB
Python
#!/usr/bin/python
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# Copyright (C) 2003-2004 Robey Pointer <robey@lag.net>
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#
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# This file is part of paramiko.
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#
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# Paramiko is free software; you can redistribute it and/or modify it under the
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# terms of the GNU Lesser General Public License as published by the Free
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# Software Foundation; either version 2.1 of the License, or (at your option)
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# any later version.
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#
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# Paramiko is distrubuted in the hope that it will be useful, but WITHOUT ANY
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# WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
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# A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more
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# details.
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#
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# You should have received a copy of the GNU Lesser General Public License
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# along with Foobar; if not, write to the Free Software Foundation, Inc.,
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# 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
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"""
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Common API for all public keys.
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"""
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import os, base64
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from Crypto.Hash import MD5
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from Crypto.Cipher import DES3
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from common import *
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from message import Message
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from ssh_exception import SSHException, PasswordRequiredException
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import util
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class PKey (object):
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"""
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Base class for public keys.
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"""
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# known encryption types for private key files:
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_CIPHER_TABLE = {
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'DES-EDE3-CBC': { 'cipher': DES3, 'keysize': 24, 'blocksize': 8, 'mode': DES3.MODE_CBC }
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}
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def __init__(self, msg=None, data=None):
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"""
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Create a new instance of this public key type. If C{msg} is given,
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the key's public part(s) will be filled in from the message. If
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C{data} is given, the key's public part(s) will be filled in from
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the string.
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@param msg: an optional SSH L{Message} containing a public key of this
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type.
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@type msg: L{Message}
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@param data: an optional string containing a public key of this type
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@type data: string
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"""
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pass
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def __str__(self):
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"""
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Return a string of an SSH L{Message} made up of the public part(s) of
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this key. This string is suitable for passing to L{__init__} to
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re-create the key object later.
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@return: string representation of an SSH key message.
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@rtype: string
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"""
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return ''
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def __cmp__(self, other):
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"""
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Compare this key to another. Returns 0 if this key is equivalent to
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the given key, or non-0 if they are different. Only the public parts
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of the key are compared, so a public key will compare equal to its
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corresponding private key.
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@param other: key to compare to.
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@type other: L{PKey}
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@return: 0 if the two keys are equivalent, non-0 otherwise.
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@rtype: int
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"""
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hs = hash(self)
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ho = hash(other)
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if hs != ho:
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return cmp(hs, ho)
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return cmp(str(self), str(other))
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def get_name(self):
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"""
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Return the name of this private key implementation.
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@return: name of this private key type, in SSH terminology (for
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example, C{"ssh-rsa"}).
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@rtype: string
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"""
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return ''
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def get_fingerprint(self):
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"""
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Return an MD5 fingerprint of the public part of this key. Nothing
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secret is revealed.
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@return: a 16-byte string (binary) of the MD5 fingerprint, in SSH
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format.
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@rtype: string
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"""
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return MD5.new(str(self)).digest()
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def get_base64(self):
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"""
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Return a base64 string containing the public part of this key. Nothing
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secret is revealed. This format is compatible with that used to store
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public key files or recognized host keys.
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@return: a base64 string containing the public part of the key.
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@rtype: string
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@since: fearow
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"""
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return ''.join(base64.encodestring(str(self)).split('\n'))
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def sign_ssh_data(self, randpool, data):
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"""
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Sign a blob of data with this private key, and return a L{Message}
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representing an SSH signature message.
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@param randpool: a secure random number generator.
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@type randpool: L{Crypto.Util.randpool.RandomPool}
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@param data: the data to sign.
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@type data: string
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@return: an SSH signature message.
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@rtype: L{Message}
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"""
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return ''
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def verify_ssh_sig(self, data, msg):
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"""
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Given a blob of data, and an SSH message representing a signature of
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that data, verify that it was signed with this key.
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@param data: the data that was signed.
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@type data: string
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@param msg: an SSH signature message
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@type msg: L{Message}
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@return: C{True} if the signature verifies correctly; C{False}
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otherwise.
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@rtype: boolean
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"""
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return False
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def read_private_key_file(self, filename, password=None):
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"""
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Read private key contents from a file into this object. If the private
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key is encrypted and C{password} is not C{None}, the given password
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will be used to decrypt the key (otherwise L{PasswordRequiredException}
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is thrown).
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@param filename: name of the file to read.
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@type filename: string
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@param password: an optional password to use to decrypt the key file,
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if it's encrypted.
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@type password: string
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@raise IOError: if there was an error reading the file.
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@raise PasswordRequiredException: if the private key file is
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encrypted, and C{password} is C{None}.
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@raise SSHException: if the key file is invalid.
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"""
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raise exception('Not implemented in PKey')
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def from_private_key_file(cl, filename, password=None):
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"""
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Create a key object by reading a private key file. This is roughly
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equivalent to creating a new key object and then calling
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L{read_private_key_file} on it. Through the magic of python, this
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factory method will exist in all subclasses of PKey (such as L{RSAKey}
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or L{DSSKey}), but is useless on the abstract PKey class.
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@param filename: name of the file to read.
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@type filename: string
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@param password: an optional password to use to decrypt the key file,
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if it's encrypted
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@type password: string
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@return: a new key object based on the given private key.
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@rtype: L{PKey}
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@raise IOError: if there was an error reading the file.
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@raise PasswordRequiredException: if the private key file is
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encrypted, and C{password} is C{None}.
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@raise SSHException: if the key file is invalid.
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@since: fearow
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"""
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key = cl()
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key.read_private_key_file(filename, password)
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return key
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from_private_key_file = classmethod(from_private_key_file)
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def write_private_key_file(self, filename, password=None):
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"""
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Write private key contents into a file. If the password is not
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C{None}, the key is encrypted before writing.
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@param filename: name of the file to write.
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@type filename: string
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@param password: an optional password to use to encrypt the key file.
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@type password: string
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@raise IOError: if there was an error writing the file.
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@raise SSHException: if the key is invalid.
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@since: fearow
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"""
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raise exception('Not implemented in PKey')
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def _read_private_key_file(self, tag, filename, password=None):
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"""
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Read an SSH2-format private key file, looking for a string of the type
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C{"BEGIN xxx PRIVATE KEY"} for some C{xxx}, base64-decode the text we
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find, and return it as a string. If the private key is encrypted and
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C{password} is not C{None}, the given password will be used to decrypt
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the key (otherwise L{PasswordRequiredException} is thrown).
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@param tag: C{"RSA"} or C{"DSA"}, the tag used to mark the data block.
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@type tag: string
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@param filename: name of the file to read.
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@type filename: string
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@param password: an optional password to use to decrypt the key file,
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if it's encrypted.
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@type password: string
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@return: data blob that makes up the private key.
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@rtype: string
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@raise IOError: if there was an error reading the file.
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@raise PasswordRequiredException: if the private key file is
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encrypted, and C{password} is C{None}.
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@raise SSHException: if the key file is invalid.
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"""
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f = open(filename, 'r')
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lines = f.readlines()
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f.close()
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start = 0
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while (start < len(lines)) and (lines[start].strip() != '-----BEGIN ' + tag + ' PRIVATE KEY-----'):
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start += 1
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if start >= len(lines):
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raise SSHException('not a valid ' + tag + ' private key file')
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# parse any headers first
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headers = {}
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start += 1
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while start < len(lines):
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l = lines[start].split(': ')
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if len(l) == 1:
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break
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headers[l[0].lower()] = l[1].strip()
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start += 1
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# find end
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end = start
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while (lines[end].strip() != '-----END ' + tag + ' PRIVATE KEY-----') and (end < len(lines)):
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end += 1
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# if we trudged to the end of the file, just try to cope.
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try:
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data = base64.decodestring(''.join(lines[start:end]))
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except binascii.Error, e:
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raise SSHException('base64 decoding error: ' + str(e))
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if not headers.has_key('proc-type'):
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# unencryped: done
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return data
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# encrypted keyfile: will need a password
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if headers['proc-type'] != '4,ENCRYPTED':
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raise SSHException('Unknown private key structure "%s"' % headers['proc-type'])
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try:
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encryption_type, saltstr = headers['dek-info'].split(',')
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except:
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raise SSHException('Can\'t parse DEK-info in private key file')
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if not self._CIPHER_TABLE.has_key(encryption_type):
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raise SSHException('Unknown private key cipher "%s"' % encryption_type)
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# if no password was passed in, raise an exception pointing out that we need one
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if password is None:
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raise PasswordRequiredException('Private key file is encrypted')
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cipher = self._CIPHER_TABLE[encryption_type]['cipher']
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keysize = self._CIPHER_TABLE[encryption_type]['keysize']
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mode = self._CIPHER_TABLE[encryption_type]['mode']
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# this confusing line turns something like '2F91' into '/\x91' (sorry, was feeling clever)
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salt = util.unhexify(saltstr)
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key = util.generate_key_bytes(MD5, salt, password, keysize)
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return cipher.new(key, mode, salt).decrypt(data)
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def _write_private_key_file(self, tag, filename, data, password=None):
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"""
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Write an SSH2-format private key file in a form that can be read by
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paramiko or openssh. If no password is given, the key is written in
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a trivially-encoded format (base64) which is completely insecure. If
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a password is given, DES-EDE3-CBC is used.
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@param tag: C{"RSA"} or C{"DSA"}, the tag used to mark the data block.
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@type tag: string
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@param filename: name of the file to write.
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@type filename: string
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@param data: data blob that makes up the private key.
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@type data: string
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@param password: an optional password to use to encrypt the file.
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@type password: string
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@raise IOError: if there was an error writing the file.
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"""
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f = open(filename, 'w', 0600)
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# grrr... the mode doesn't always take hold
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os.chmod(filename, 0600)
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f.write('-----BEGIN %s PRIVATE KEY-----\n' % tag)
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if password is not None:
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# since we only support one cipher here, use it
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cipher_name = self._CIPHER_TABLE.keys()[0]
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cipher = self._CIPHER_TABLE[cipher_name]['cipher']
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keysize = self._CIPHER_TABLE[cipher_name]['keysize']
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blocksize = self._CIPHER_TABLE[cipher_name]['blocksize']
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mode = self._CIPHER_TABLE[cipher_name]['mode']
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salt = randpool.get_bytes(8)
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key = util.generate_key_bytes(MD5, salt, password, keysize)
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if len(data) % blocksize != 0:
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n = blocksize - len(data) % blocksize
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#data += randpool.get_bytes(n)
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# that would make more sense ^, but it confuses openssh.
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data += '\0' * n
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data = cipher.new(key, mode, salt).encrypt(data)
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f.write('Proc-Type: 4,ENCRYPTED\n')
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f.write('DEK-Info: %s,%s\n' % (cipher_name, util.hexify(salt)))
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f.write('\n')
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s = base64.encodestring(data)
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# re-wrap to 64-char lines
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s = ''.join(s.split('\n'))
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s = '\n'.join([s[i : i+64] for i in range(0, len(s), 64)])
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f.write(s)
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f.write('\n')
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f.write('-----END %s PRIVATE KEY-----\n' % tag)
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f.close()
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