paramiko.pkey

Package paramiko :: Module pkey |
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# Source Code for Module paramiko.pkey

      1  # Copyright (C) 2003-2007  Robey Pointer <robeypointer@gmail.com>
      2  #
      3  # This file is part of paramiko.
      4  #
      5  # Paramiko is free software; you can redistribute it and/or modify it under the
      6  # terms of the GNU Lesser General Public License as published by the Free
      7  # Software Foundation; either version 2.1 of the License, or (at your option)
      8  # any later version.
      9  #
     10  # Paramiko is distrubuted in the hope that it will be useful, but WITHOUT ANY
     11  # WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
     12  # A PARTICULAR PURPOSE.  See the GNU Lesser General Public License for more
     13  # details.
     14  #
     15  # You should have received a copy of the GNU Lesser General Public License
     16  # along with Paramiko; if not, write to the Free Software Foundation, Inc.,
     17  # 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA.
     18
     19  """
     20  Common API for all public keys.
     21  """
     22
     23  import base64
     24  from binascii import hexlify, unhexlify
     25  import os
     26
     27  from Crypto.Hash import MD5
     28  from Crypto.Cipher import DES3, AES
     29
     30  from paramiko.common import *
     31  from paramiko import util
     32  from paramiko.message import Message
     33  from paramiko.ssh_exception import SSHException, PasswordRequiredException
     34
     35
     36 -class PKey (object):
     37      """
     38      Base class for public keys.
     39      """
     40
     41      # known encryption types for private key files:
     42      _CIPHER_TABLE = {
     43          'AES-128-CBC': { 'cipher': AES, 'keysize': 16, 'blocksize': 16, 'mode': AES.MODE_CBC },
     44          'DES-EDE3-CBC': { 'cipher': DES3, 'keysize': 24, 'blocksize': 8, 'mode': DES3.MODE_CBC },
     45      }
     46
     47
     48 -    def __init__(self, msg=None, data=None):
     49          """
     50          Create a new instance of this public key type.  If C{msg} is given,
     51          the key's public part(s) will be filled in from the message.  If
     52          C{data} is given, the key's public part(s) will be filled in from
     53          the string.
     54
     55          @param msg: an optional SSH L{Message} containing a public key of this
     56          type.
     57          @type msg: L{Message}
     58          @param data: an optional string containing a public key of this type
     59          @type data: str
     60
     61          @raise SSHException: if a key cannot be created from the C{data} or
     62          C{msg} given, or no key was passed in.
     63          """
     64          pass
     65
     66 -    def __str__(self):
     67          """
     68          Return a string of an SSH L{Message} made up of the public part(s) of
     69          this key.  This string is suitable for passing to L{__init__} to
     70          re-create the key object later.
     71
     72          @return: string representation of an SSH key message.
     73          @rtype: str
     74          """
     75          return ''
     76
     77 -    def __cmp__(self, other):
     78          """
     79          Compare this key to another.  Returns 0 if this key is equivalent to
     80          the given key, or non-0 if they are different.  Only the public parts
     81          of the key are compared, so a public key will compare equal to its
     82          corresponding private key.
     83
     84          @param other: key to compare to.
     85          @type other: L{PKey}
     86          @return: 0 if the two keys are equivalent, non-0 otherwise.
     87          @rtype: int
     88          """
     89          hs = hash(self)
     90          ho = hash(other)
     91          if hs != ho:
     92              return cmp(hs, ho)
     93          return cmp(str(self), str(other))
     94
     95 -    def get_name(self):
     96          """
     97          Return the name of this private key implementation.
     98
     99          @return: name of this private key type, in SSH terminology (for
    100          example, C{"ssh-rsa"}).
    101          @rtype: str
    102          """
    103          return ''
    104
    105 -    def get_bits(self):
    106          """
    107          Return the number of significant bits in this key.  This is useful
    108          for judging the relative security of a key.
    109
    110          @return: bits in the key.
    111          @rtype: int
    112          """
    113          return 0
    114
    115 -    def can_sign(self):
    116          """
    117          Return C{True} if this key has the private part necessary for signing
    118          data.
    119
    120          @return: C{True} if this is a private key.
    121          @rtype: bool
    122          """
    123          return False
    124
    125 -    def get_fingerprint(self):
    126          """
    127          Return an MD5 fingerprint of the public part of this key.  Nothing
    128          secret is revealed.
    129
    130          @return: a 16-byte string (binary) of the MD5 fingerprint, in SSH
    131              format.
    132          @rtype: str
    133          """
    134          return MD5.new(str(self)).digest()
    135
    136 -    def get_base64(self):
    137          """
    138          Return a base64 string containing the public part of this key.  Nothing
    139          secret is revealed.  This format is compatible with that used to store
    140          public key files or recognized host keys.
    141
    142          @return: a base64 string containing the public part of the key.
    143          @rtype: str
    144          """
    145          return base64.encodestring(str(self)).replace('\n', '')
    146
    147 -    def sign_ssh_data(self, rng, data):
    148          """
    149          Sign a blob of data with this private key, and return a L{Message}
    150          representing an SSH signature message.
    151
    152          @param rng: a secure random number generator.
    153          @type rng: L{Crypto.Util.rng.RandomPool}
    154          @param data: the data to sign.
    155          @type data: str
    156          @return: an SSH signature message.
    157          @rtype: L{Message}
    158          """
    159          return ''
    160
    161 -    def verify_ssh_sig(self, data, msg):
    162          """
    163          Given a blob of data, and an SSH message representing a signature of
    164          that data, verify that it was signed with this key.
    165
    166          @param data: the data that was signed.
    167          @type data: str
    168          @param msg: an SSH signature message
    169          @type msg: L{Message}
    170          @return: C{True} if the signature verifies correctly; C{False}
    171              otherwise.
    172          @rtype: boolean
    173          """
    174          return False
    175
    176 -    def from_private_key_file(cls, filename, password=None):
    177          """
    178          Create a key object by reading a private key file.  If the private
    179          key is encrypted and C{password} is not C{None}, the given password
    180          will be used to decrypt the key (otherwise L{PasswordRequiredException}
    181          is thrown).  Through the magic of python, this factory method will
    182          exist in all subclasses of PKey (such as L{RSAKey} or L{DSSKey}), but
    183          is useless on the abstract PKey class.
    184
    185          @param filename: name of the file to read
    186          @type filename: str
    187          @param password: an optional password to use to decrypt the key file,
    188              if it's encrypted
    189          @type password: str
    190          @return: a new key object based on the given private key
    191          @rtype: L{PKey}
    192
    193          @raise IOError: if there was an error reading the file
    194          @raise PasswordRequiredException: if the private key file is
    195              encrypted, and C{password} is C{None}
    196          @raise SSHException: if the key file is invalid
    197          """
    198          key = cls(filename=filename, password=password)
    199          return key
    200      from_private_key_file = classmethod(from_private_key_file)
    201
    202 -    def from_private_key(cls, file_obj, password=None):
    203          """
    204          Create a key object by reading a private key from a file (or file-like)
    205          object.  If the private key is encrypted and C{password} is not C{None},
    206          the given password will be used to decrypt the key (otherwise
    207          L{PasswordRequiredException} is thrown).
    208
    209          @param file_obj: the file to read from
    210          @type file_obj: file
    211          @param password: an optional password to use to decrypt the key, if it's
    212              encrypted
    213          @type password: str
    214          @return: a new key object based on the given private key
    215          @rtype: L{PKey}
    216
    217          @raise IOError: if there was an error reading the key
    218          @raise PasswordRequiredException: if the private key file is encrypted,
    219              and C{password} is C{None}
    220          @raise SSHException: if the key file is invalid
    221          """
    222          key = cls(file_obj=file_obj, password=password)
    223          return key
    224      from_private_key = classmethod(from_private_key)
    225
    226 -    def write_private_key_file(self, filename, password=None):
    227          """
    228          Write private key contents into a file.  If the password is not
    229          C{None}, the key is encrypted before writing.
    230
    231          @param filename: name of the file to write
    232          @type filename: str
    233          @param password: an optional password to use to encrypt the key file
    234          @type password: str
    235
    236          @raise IOError: if there was an error writing the file
    237          @raise SSHException: if the key is invalid
    238          """
    239          raise Exception('Not implemented in PKey')
    240
    241 -    def write_private_key(self, file_obj, password=None):
    242          """
    243          Write private key contents into a file (or file-like) object.  If the
    244          password is not C{None}, the key is encrypted before writing.
    245
    246          @param file_obj: the file object to write into
    247          @type file_obj: file
    248          @param password: an optional password to use to encrypt the key
    249          @type password: str
    250
    251          @raise IOError: if there was an error writing to the file
    252          @raise SSHException: if the key is invalid
    253          """
    254          raise Exception('Not implemented in PKey')
    255
    256 -    def _read_private_key_file(self, tag, filename, password=None):
    257          """
    258          Read an SSH2-format private key file, looking for a string of the type
    259          C{"BEGIN xxx PRIVATE KEY"} for some C{xxx}, base64-decode the text we
    260          find, and return it as a string.  If the private key is encrypted and
    261          C{password} is not C{None}, the given password will be used to decrypt
    262          the key (otherwise L{PasswordRequiredException} is thrown).
    263
    264          @param tag: C{"RSA"} or C{"DSA"}, the tag used to mark the data block.
    265          @type tag: str
    266          @param filename: name of the file to read.
    267          @type filename: str
    268          @param password: an optional password to use to decrypt the key file,
    269              if it's encrypted.
    270          @type password: str
    271          @return: data blob that makes up the private key.
    272          @rtype: str
    273
    274          @raise IOError: if there was an error reading the file.
    275          @raise PasswordRequiredException: if the private key file is
    276              encrypted, and C{password} is C{None}.
    277          @raise SSHException: if the key file is invalid.
    278          """
    279          f = open(filename, 'r')
    280          data = self._read_private_key(tag, f, password)
    281          f.close()
    282          return data
    283
    284 -    def _read_private_key(self, tag, f, password=None):
    285          lines = f.readlines()
    286          start = 0
    287          while (start < len(lines)) and (lines[start].strip() != '-----BEGIN ' + tag + ' PRIVATE KEY-----'):
    288              start += 1
    289          if start >= len(lines):
    290              raise SSHException('not a valid ' + tag + ' private key file')
    291          # parse any headers first
    292          headers = {}
    293          start += 1
    294          while start < len(lines):
    295              l = lines[start].split(': ')
    296              if len(l) == 1:
    297                  break
    298              headers[l[0].lower()] = l[1].strip()
    299              start += 1
    300          # find end
    301          end = start
    302          while (lines[end].strip() != '-----END ' + tag + ' PRIVATE KEY-----') and (end < len(lines)):
    303              end += 1
    304          # if we trudged to the end of the file, just try to cope.
    305          try:
    306              data = base64.decodestring(''.join(lines[start:end]))
    307          except base64.binascii.Error, e:
    308              raise SSHException('base64 decoding error: ' + str(e))
    309          if 'proc-type' not in headers:
    310              # unencryped: done
    311              return data
    312          # encrypted keyfile: will need a password
    313          if headers['proc-type'] != '4,ENCRYPTED':
    314              raise SSHException('Unknown private key structure "%s"' % headers['proc-type'])
    315          try:
    316              encryption_type, saltstr = headers['dek-info'].split(',')
    317          except:
    318              raise SSHException('Can\'t parse DEK-info in private key file')
    319          if encryption_type not in self._CIPHER_TABLE:
    320              raise SSHException('Unknown private key cipher "%s"' % encryption_type)
    321          # if no password was passed in, raise an exception pointing out that we need one
    322          if password is None:
    323              raise PasswordRequiredException('Private key file is encrypted')
    324          cipher = self._CIPHER_TABLE[encryption_type]['cipher']
    325          keysize = self._CIPHER_TABLE[encryption_type]['keysize']
    326          mode = self._CIPHER_TABLE[encryption_type]['mode']
    327          salt = unhexlify(saltstr)
    328          key = util.generate_key_bytes(MD5, salt, password, keysize)
    329          return cipher.new(key, mode, salt).decrypt(data)
    330
    331 -    def _write_private_key_file(self, tag, filename, data, password=None):
    332          """
    333          Write an SSH2-format private key file in a form that can be read by
    334          paramiko or openssh.  If no password is given, the key is written in
    335          a trivially-encoded format (base64) which is completely insecure.  If
    336          a password is given, DES-EDE3-CBC is used.
    337
    338          @param tag: C{"RSA"} or C{"DSA"}, the tag used to mark the data block.
    339          @type tag: str
    340          @param filename: name of the file to write.
    341          @type filename: str
    342          @param data: data blob that makes up the private key.
    343          @type data: str
    344          @param password: an optional password to use to encrypt the file.
    345          @type password: str
    346
    347          @raise IOError: if there was an error writing the file.
    348          """
    349          f = open(filename, 'w', 0600)
    350          # grrr... the mode doesn't always take hold
    351          os.chmod(filename, 0600)
    352          self._write_private_key(tag, f, data, password)
    353          f.close()
    354
    355 -    def _write_private_key(self, tag, f, data, password=None):
    356          f.write('-----BEGIN %s PRIVATE KEY-----\n' % tag)
    357          if password is not None:
    358              # since we only support one cipher here, use it
    359              cipher_name = self._CIPHER_TABLE.keys()[0]
    360              cipher = self._CIPHER_TABLE[cipher_name]['cipher']
    361              keysize = self._CIPHER_TABLE[cipher_name]['keysize']
    362              blocksize = self._CIPHER_TABLE[cipher_name]['blocksize']
    363              mode = self._CIPHER_TABLE[cipher_name]['mode']
    364              salt = rng.read(8)
    365              key = util.generate_key_bytes(MD5, salt, password, keysize)
    366              if len(data) % blocksize != 0:
    367                  n = blocksize - len(data) % blocksize
    368                  #data += rng.read(n)
    369                  # that would make more sense ^, but it confuses openssh.
    370                  data += '\0' * n
    371              data = cipher.new(key, mode, salt).encrypt(data)
    372              f.write('Proc-Type: 4,ENCRYPTED\n')
    373              f.write('DEK-Info: %s,%s\n' % (cipher_name, hexlify(salt).upper()))
    374              f.write('\n')
    375          s = base64.encodestring(data)
    376          # re-wrap to 64-char lines
    377          s = ''.join(s.split('\n'))
    378          s = '\n'.join([s[i : i+64] for i in range(0, len(s), 64)])
    379          f.write(s)
    380          f.write('\n')
    381          f.write('-----END %s PRIVATE KEY-----\n' % tag)
    382