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