Edit File: hostkeys.py
# Copyright (C) 2006-2007 Robey Pointer <robeypointer@gmail.com> # # This file is part of paramiko. # # Paramiko is free software; you can redistribute it and/or modify it under the # terms of the GNU Lesser General Public License as published by the Free # Software Foundation; either version 2.1 of the License, or (at your option) # any later version. # # Paramiko is distributed in the hope that it will be useful, but WITHOUT ANY # WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR # A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more # details. # # You should have received a copy of the GNU Lesser General Public License # along with Paramiko; if not, write to the Free Software Foundation, Inc., # 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA. import binascii import os from hashlib import sha1 from hmac import HMAC from paramiko.py3compat import b, u, encodebytes, decodebytes try: from collections import MutableMapping except ImportError: # noinspection PyUnresolvedReferences from UserDict import DictMixin as MutableMapping from paramiko.dsskey import DSSKey from paramiko.rsakey import RSAKey from paramiko.util import get_logger, constant_time_bytes_eq from paramiko.ecdsakey import ECDSAKey from paramiko.ssh_exception import SSHException class HostKeys (MutableMapping): """ Representation of an OpenSSH-style "known hosts" file. Host keys can be read from one or more files, and then individual hosts can be looked up to verify server keys during SSH negotiation. A `.HostKeys` object can be treated like a dict; any dict lookup is equivalent to calling `lookup`. .. versionadded:: 1.5.3 """ def __init__(self, filename=None): """ Create a new HostKeys object, optionally loading keys from an OpenSSH style host-key file. :param str filename: filename to load host keys from, or ``None`` """ # emulate a dict of { hostname: { keytype: PKey } } self._entries = [] if filename is not None: self.load(filename) def add(self, hostname, keytype, key): """ Add a host key entry to the table. Any existing entry for a ``(hostname, keytype)`` pair will be replaced. :param str hostname: the hostname (or IP) to add :param str keytype: key type (``"ssh-rsa"`` or ``"ssh-dss"``) :param .PKey key: the key to add """ for e in self._entries: if (hostname in e.hostnames) and (e.key.get_name() == keytype): e.key = key return self._entries.append(HostKeyEntry([hostname], key)) def load(self, filename): """ Read a file of known SSH host keys, in the format used by OpenSSH. This type of file unfortunately doesn't exist on Windows, but on posix, it will usually be stored in ``os.path.expanduser("~/.ssh/known_hosts")``. If this method is called multiple times, the host keys are merged, not cleared. So multiple calls to `load` will just call `add`, replacing any existing entries and adding new ones. :param str filename: name of the file to read host keys from :raises IOError: if there was an error reading the file """ with open(filename, 'r') as f: for lineno, line in enumerate(f, 1): line = line.strip() if (len(line) == 0) or (line[0] == '#'): continue try: e = HostKeyEntry.from_line(line, lineno) except SSHException: continue if e is not None: _hostnames = e.hostnames for h in _hostnames: if self.check(h, e.key): e.hostnames.remove(h) if len(e.hostnames): self._entries.append(e) def save(self, filename): """ Save host keys into a file, in the format used by OpenSSH. The order of keys in the file will be preserved when possible (if these keys were loaded from a file originally). The single exception is that combined lines will be split into individual key lines, which is arguably a bug. :param str filename: name of the file to write :raises IOError: if there was an error writing the file .. versionadded:: 1.6.1 """ with open(filename, 'w') as f: for e in self._entries: line = e.to_line() if line: f.write(line) def lookup(self, hostname): """ Find a hostkey entry for a given hostname or IP. If no entry is found, ``None`` is returned. Otherwise a dictionary of keytype to key is returned. The keytype will be either ``"ssh-rsa"`` or ``"ssh-dss"``. :param str hostname: the hostname (or IP) to lookup :return: dict of `str` -> `.PKey` keys associated with this host (or ``None``) """ class SubDict (MutableMapping): def __init__(self, hostname, entries, hostkeys): self._hostname = hostname self._entries = entries self._hostkeys = hostkeys def __iter__(self): for k in self.keys(): yield k def __len__(self): return len(self.keys()) def __delitem__(self, key): for e in list(self._entries): if e.key.get_name() == key: self._entries.remove(e) else: raise KeyError(key) def __getitem__(self, key): for e in self._entries: if e.key.get_name() == key: return e.key raise KeyError(key) def __setitem__(self, key, val): for e in self._entries: if e.key is None: continue if e.key.get_name() == key: # replace e.key = val break else: # add a new one e = HostKeyEntry([hostname], val) self._entries.append(e) self._hostkeys._entries.append(e) def keys(self): return [e.key.get_name() for e in self._entries if e.key is not None] entries = [] for e in self._entries: for h in e.hostnames: if h.startswith('|1|') and not hostname.startswith('|1|') and constant_time_bytes_eq(self.hash_host(hostname, h), h) or h == hostname: entries.append(e) if len(entries) == 0: return None return SubDict(hostname, entries, self) def check(self, hostname, key): """ Return True if the given key is associated with the given hostname in this dictionary. :param str hostname: hostname (or IP) of the SSH server :param .PKey key: the key to check :return: ``True`` if the key is associated with the hostname; else ``False`` """ k = self.lookup(hostname) if k is None: return False host_key = k.get(key.get_name(), None) if host_key is None: return False return host_key.asbytes() == key.asbytes() def clear(self): """ Remove all host keys from the dictionary. """ self._entries = [] def __iter__(self): for k in self.keys(): yield k def __len__(self): return len(self.keys()) def __delitem__(self, key): k = self[key] def __getitem__(self, key): ret = self.lookup(key) if ret is None: raise KeyError(key) return ret def __setitem__(self, hostname, entry): # don't use this please. if len(entry) == 0: self._entries.append(HostKeyEntry([hostname], None)) return for key_type in entry.keys(): found = False for e in self._entries: if (hostname in e.hostnames) and (e.key.get_name() == key_type): # replace e.key = entry[key_type] found = True if not found: self._entries.append(HostKeyEntry([hostname], entry[key_type])) def keys(self): # Python 2.4 sets would be nice here. ret = [] for e in self._entries: for h in e.hostnames: if h not in ret: ret.append(h) return ret def values(self): ret = [] for k in self.keys(): ret.append(self.lookup(k)) return ret @staticmethod def hash_host(hostname, salt=None): """ Return a "hashed" form of the hostname, as used by OpenSSH when storing hashed hostnames in the known_hosts file. :param str hostname: the hostname to hash :param str salt: optional salt to use when hashing (must be 20 bytes long) :return: the hashed hostname as a `str` """ if salt is None: salt = os.urandom(sha1().digest_size) else: if salt.startswith('|1|'): salt = salt.split('|')[2] salt = decodebytes(b(salt)) assert len(salt) == sha1().digest_size hmac = HMAC(salt, b(hostname), sha1).digest() hostkey = '|1|%s|%s' % (u(encodebytes(salt)), u(encodebytes(hmac))) return hostkey.replace('\n', '') class InvalidHostKey(Exception): def __init__(self, line, exc): self.line = line self.exc = exc self.args = (line, exc) class HostKeyEntry: """ Representation of a line in an OpenSSH-style "known hosts" file. """ def __init__(self, hostnames=None, key=None): self.valid = (hostnames is not None) and (key is not None) self.hostnames = hostnames self.key = key @classmethod def from_line(cls, line, lineno=None): """ Parses the given line of text to find the names for the host, the type of key, and the key data. The line is expected to be in the format used by the OpenSSH known_hosts file. Lines are expected to not have leading or trailing whitespace. We don't bother to check for comments or empty lines. All of that should be taken care of before sending the line to us. :param str line: a line from an OpenSSH known_hosts file """ log = get_logger('paramiko.hostkeys') fields = line.split(' ') if len(fields) < 3: # Bad number of fields log.info("Not enough fields found in known_hosts in line %s (%r)" % (lineno, line)) return None fields = fields[:3] names, keytype, key = fields names = names.split(',') # Decide what kind of key we're looking at and create an object # to hold it accordingly. try: key = b(key) if keytype == 'ssh-rsa': key = RSAKey(data=decodebytes(key)) elif keytype == 'ssh-dss': key = DSSKey(data=decodebytes(key)) elif keytype in ECDSAKey.supported_key_format_identifiers(): key = ECDSAKey(data=decodebytes(key), validate_point=False) else: log.info("Unable to handle key of type %s" % (keytype,)) return None except binascii.Error as e: raise InvalidHostKey(line, e) return cls(names, key) def to_line(self): """ Returns a string in OpenSSH known_hosts file format, or None if the object is not in a valid state. A trailing newline is included. """ if self.valid: return '%s %s %s\n' % (','.join(self.hostnames), self.key.get_name(), self.key.get_base64()) return None def __repr__(self): return '<HostKeyEntry %r: %r>' % (self.hostnames, self.key)