Ausgabe der neuen DB Einträge
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hubobel
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2399 changed files with 843193 additions and 43 deletions
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# -*- test-case-name: twisted.conch.test.test_knownhosts -*-
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# Copyright (c) Twisted Matrix Laboratories.
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# See LICENSE for details.
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"""
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An implementation of the OpenSSH known_hosts database.
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@since: 8.2
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"""
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from __future__ import absolute_import, division
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import hmac
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from binascii import Error as DecodeError, b2a_base64, a2b_base64
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from contextlib import closing
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from hashlib import sha1
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import sys
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from zope.interface import implementer
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from twisted.conch.interfaces import IKnownHostEntry
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from twisted.conch.error import HostKeyChanged, UserRejectedKey, InvalidEntry
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from twisted.conch.ssh.keys import Key, BadKeyError, FingerprintFormats
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from twisted.internet import defer
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from twisted.python import log
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from twisted.python.compat import nativeString, unicode
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from twisted.python.randbytes import secureRandom
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from twisted.python.util import FancyEqMixin
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def _b64encode(s):
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"""
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Encode a binary string as base64 with no trailing newline.
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@param s: The string to encode.
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@type s: L{bytes}
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@return: The base64-encoded string.
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@rtype: L{bytes}
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"""
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return b2a_base64(s).strip()
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def _extractCommon(string):
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"""
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Extract common elements of base64 keys from an entry in a hosts file.
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@param string: A known hosts file entry (a single line).
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@type string: L{bytes}
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@return: a 4-tuple of hostname data (L{bytes}), ssh key type (L{bytes}), key
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(L{Key}), and comment (L{bytes} or L{None}). The hostname data is
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simply the beginning of the line up to the first occurrence of
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whitespace.
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@rtype: L{tuple}
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"""
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elements = string.split(None, 2)
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if len(elements) != 3:
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raise InvalidEntry()
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hostnames, keyType, keyAndComment = elements
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splitkey = keyAndComment.split(None, 1)
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if len(splitkey) == 2:
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keyString, comment = splitkey
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comment = comment.rstrip(b"\n")
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else:
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keyString = splitkey[0]
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comment = None
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key = Key.fromString(a2b_base64(keyString))
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return hostnames, keyType, key, comment
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class _BaseEntry(object):
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"""
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Abstract base of both hashed and non-hashed entry objects, since they
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represent keys and key types the same way.
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@ivar keyType: The type of the key; either ssh-dss or ssh-rsa.
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@type keyType: L{bytes}
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@ivar publicKey: The server public key indicated by this line.
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@type publicKey: L{twisted.conch.ssh.keys.Key}
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@ivar comment: Trailing garbage after the key line.
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@type comment: L{bytes}
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"""
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def __init__(self, keyType, publicKey, comment):
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self.keyType = keyType
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self.publicKey = publicKey
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self.comment = comment
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def matchesKey(self, keyObject):
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"""
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Check to see if this entry matches a given key object.
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@param keyObject: A public key object to check.
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@type keyObject: L{Key}
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@return: C{True} if this entry's key matches C{keyObject}, C{False}
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otherwise.
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@rtype: L{bool}
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"""
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return self.publicKey == keyObject
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@implementer(IKnownHostEntry)
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class PlainEntry(_BaseEntry):
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"""
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A L{PlainEntry} is a representation of a plain-text entry in a known_hosts
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file.
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@ivar _hostnames: the list of all host-names associated with this entry.
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@type _hostnames: L{list} of L{bytes}
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"""
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def __init__(self, hostnames, keyType, publicKey, comment):
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self._hostnames = hostnames
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super(PlainEntry, self).__init__(keyType, publicKey, comment)
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@classmethod
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def fromString(cls, string):
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"""
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Parse a plain-text entry in a known_hosts file, and return a
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corresponding L{PlainEntry}.
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@param string: a space-separated string formatted like "hostname
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key-type base64-key-data comment".
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@type string: L{bytes}
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@raise DecodeError: if the key is not valid encoded as valid base64.
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@raise InvalidEntry: if the entry does not have the right number of
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elements and is therefore invalid.
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@raise BadKeyError: if the key, once decoded from base64, is not
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actually an SSH key.
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@return: an IKnownHostEntry representing the hostname and key in the
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input line.
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@rtype: L{PlainEntry}
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"""
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hostnames, keyType, key, comment = _extractCommon(string)
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self = cls(hostnames.split(b","), keyType, key, comment)
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return self
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def matchesHost(self, hostname):
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"""
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Check to see if this entry matches a given hostname.
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@param hostname: A hostname or IP address literal to check against this
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entry.
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@type hostname: L{bytes}
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@return: C{True} if this entry is for the given hostname or IP address,
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C{False} otherwise.
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@rtype: L{bool}
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"""
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if isinstance(hostname, unicode):
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hostname = hostname.encode("utf-8")
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return hostname in self._hostnames
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def toString(self):
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"""
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Implement L{IKnownHostEntry.toString} by recording the comma-separated
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hostnames, key type, and base-64 encoded key.
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@return: The string representation of this entry, with unhashed hostname
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information.
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@rtype: L{bytes}
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"""
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fields = [b','.join(self._hostnames),
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self.keyType,
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_b64encode(self.publicKey.blob())]
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if self.comment is not None:
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fields.append(self.comment)
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return b' '.join(fields)
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@implementer(IKnownHostEntry)
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class UnparsedEntry(object):
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"""
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L{UnparsedEntry} is an entry in a L{KnownHostsFile} which can't actually be
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parsed; therefore it matches no keys and no hosts.
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"""
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def __init__(self, string):
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"""
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Create an unparsed entry from a line in a known_hosts file which cannot
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otherwise be parsed.
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"""
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self._string = string
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def matchesHost(self, hostname):
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"""
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Always returns False.
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"""
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return False
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def matchesKey(self, key):
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"""
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Always returns False.
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"""
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return False
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def toString(self):
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"""
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Returns the input line, without its newline if one was given.
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@return: The string representation of this entry, almost exactly as was
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used to initialize this entry but without a trailing newline.
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@rtype: L{bytes}
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"""
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return self._string.rstrip(b"\n")
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def _hmacedString(key, string):
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"""
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Return the SHA-1 HMAC hash of the given key and string.
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@param key: The HMAC key.
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@type key: L{bytes}
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@param string: The string to be hashed.
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@type string: L{bytes}
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@return: The keyed hash value.
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@rtype: L{bytes}
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"""
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hash = hmac.HMAC(key, digestmod=sha1)
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if isinstance(string, unicode):
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string = string.encode("utf-8")
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hash.update(string)
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return hash.digest()
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@implementer(IKnownHostEntry)
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class HashedEntry(_BaseEntry, FancyEqMixin):
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"""
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A L{HashedEntry} is a representation of an entry in a known_hosts file
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where the hostname has been hashed and salted.
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@ivar _hostSalt: the salt to combine with a hostname for hashing.
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@ivar _hostHash: the hashed representation of the hostname.
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@cvar MAGIC: the 'hash magic' string used to identify a hashed line in a
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known_hosts file as opposed to a plaintext one.
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"""
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MAGIC = b'|1|'
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compareAttributes = (
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"_hostSalt", "_hostHash", "keyType", "publicKey", "comment")
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def __init__(self, hostSalt, hostHash, keyType, publicKey, comment):
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self._hostSalt = hostSalt
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self._hostHash = hostHash
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super(HashedEntry, self).__init__(keyType, publicKey, comment)
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@classmethod
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def fromString(cls, string):
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"""
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Load a hashed entry from a string representing a line in a known_hosts
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file.
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@param string: A complete single line from a I{known_hosts} file,
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formatted as defined by OpenSSH.
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@type string: L{bytes}
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@raise DecodeError: if the key, the hostname, or the is not valid
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encoded as valid base64
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@raise InvalidEntry: if the entry does not have the right number of
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elements and is therefore invalid, or the host/hash portion contains
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more items than just the host and hash.
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@raise BadKeyError: if the key, once decoded from base64, is not
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actually an SSH key.
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@return: The newly created L{HashedEntry} instance, initialized with the
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information from C{string}.
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"""
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stuff, keyType, key, comment = _extractCommon(string)
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saltAndHash = stuff[len(cls.MAGIC):].split(b"|")
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if len(saltAndHash) != 2:
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raise InvalidEntry()
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hostSalt, hostHash = saltAndHash
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self = cls(a2b_base64(hostSalt), a2b_base64(hostHash),
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keyType, key, comment)
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return self
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def matchesHost(self, hostname):
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"""
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Implement L{IKnownHostEntry.matchesHost} to compare the hash of the
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input to the stored hash.
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@param hostname: A hostname or IP address literal to check against this
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entry.
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@type hostname: L{bytes}
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@return: C{True} if this entry is for the given hostname or IP address,
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C{False} otherwise.
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@rtype: L{bool}
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"""
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return (_hmacedString(self._hostSalt, hostname) == self._hostHash)
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def toString(self):
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"""
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Implement L{IKnownHostEntry.toString} by base64-encoding the salt, host
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hash, and key.
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@return: The string representation of this entry, with the hostname part
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hashed.
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@rtype: L{bytes}
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"""
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fields = [self.MAGIC + b'|'.join([_b64encode(self._hostSalt),
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_b64encode(self._hostHash)]),
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self.keyType,
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_b64encode(self.publicKey.blob())]
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if self.comment is not None:
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fields.append(self.comment)
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return b' '.join(fields)
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class KnownHostsFile(object):
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"""
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A structured representation of an OpenSSH-format ~/.ssh/known_hosts file.
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@ivar _added: A list of L{IKnownHostEntry} providers which have been added
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to this instance in memory but not yet saved.
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@ivar _clobber: A flag indicating whether the current contents of the save
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path will be disregarded and potentially overwritten or not. If
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C{True}, this will be done. If C{False}, entries in the save path will
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be read and new entries will be saved by appending rather than
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overwriting.
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@type _clobber: L{bool}
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@ivar _savePath: See C{savePath} parameter of L{__init__}.
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"""
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def __init__(self, savePath):
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"""
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Create a new, empty KnownHostsFile.
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Unless you want to erase the current contents of C{savePath}, you want
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to use L{KnownHostsFile.fromPath} instead.
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@param savePath: The L{FilePath} to which to save new entries.
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@type savePath: L{FilePath}
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"""
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self._added = []
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self._savePath = savePath
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self._clobber = True
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@property
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def savePath(self):
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"""
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@see: C{savePath} parameter of L{__init__}
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"""
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return self._savePath
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def iterentries(self):
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"""
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Iterate over the host entries in this file.
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@return: An iterable the elements of which provide L{IKnownHostEntry}.
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There is an element for each entry in the file as well as an element
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for each added but not yet saved entry.
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@rtype: iterable of L{IKnownHostEntry} providers
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"""
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for entry in self._added:
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yield entry
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if self._clobber:
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return
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try:
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fp = self._savePath.open()
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except IOError:
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return
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with fp:
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for line in fp:
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try:
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if line.startswith(HashedEntry.MAGIC):
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entry = HashedEntry.fromString(line)
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else:
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entry = PlainEntry.fromString(line)
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except (DecodeError, InvalidEntry, BadKeyError):
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entry = UnparsedEntry(line)
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yield entry
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def hasHostKey(self, hostname, key):
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"""
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Check for an entry with matching hostname and key.
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@param hostname: A hostname or IP address literal to check for.
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@type hostname: L{bytes}
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@param key: The public key to check for.
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@type key: L{Key}
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@return: C{True} if the given hostname and key are present in this file,
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C{False} if they are not.
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@rtype: L{bool}
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@raise HostKeyChanged: if the host key found for the given hostname
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does not match the given key.
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"""
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for lineidx, entry in enumerate(self.iterentries(), -len(self._added)):
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if entry.matchesHost(hostname) and entry.keyType == key.sshType():
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if entry.matchesKey(key):
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return True
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else:
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# Notice that lineidx is 0-based but HostKeyChanged.lineno
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# is 1-based.
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if lineidx < 0:
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line = None
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path = None
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else:
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line = lineidx + 1
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path = self._savePath
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raise HostKeyChanged(entry, path, line)
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return False
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def verifyHostKey(self, ui, hostname, ip, key):
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"""
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Verify the given host key for the given IP and host, asking for
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confirmation from, and notifying, the given UI about changes to this
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file.
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@param ui: The user interface to request an IP address from.
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@param hostname: The hostname that the user requested to connect to.
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@param ip: The string representation of the IP address that is actually
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being connected to.
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@param key: The public key of the server.
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@return: a L{Deferred} that fires with True when the key has been
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verified, or fires with an errback when the key either cannot be
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verified or has changed.
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@rtype: L{Deferred}
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"""
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hhk = defer.maybeDeferred(self.hasHostKey, hostname, key)
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def gotHasKey(result):
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if result:
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if not self.hasHostKey(ip, key):
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ui.warn("Warning: Permanently added the %s host key for "
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"IP address '%s' to the list of known hosts." %
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(key.type(), nativeString(ip)))
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self.addHostKey(ip, key)
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self.save()
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return result
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else:
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def promptResponse(response):
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if response:
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self.addHostKey(hostname, key)
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self.addHostKey(ip, key)
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self.save()
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return response
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else:
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raise UserRejectedKey()
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keytype = key.type()
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if keytype == "EC":
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keytype = "ECDSA"
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prompt = (
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"The authenticity of host '%s (%s)' "
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"can't be established.\n"
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"%s key fingerprint is SHA256:%s.\n"
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"Are you sure you want to continue connecting (yes/no)? " %
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(nativeString(hostname), nativeString(ip), keytype,
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key.fingerprint(format=FingerprintFormats.SHA256_BASE64)))
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proceed = ui.prompt(prompt.encode(sys.getdefaultencoding()))
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return proceed.addCallback(promptResponse)
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return hhk.addCallback(gotHasKey)
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def addHostKey(self, hostname, key):
|
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"""
|
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Add a new L{HashedEntry} to the key database.
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|
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Note that you still need to call L{KnownHostsFile.save} if you wish
|
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these changes to be persisted.
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|
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@param hostname: A hostname or IP address literal to associate with the
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new entry.
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@type hostname: L{bytes}
|
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|
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@param key: The public key to associate with the new entry.
|
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@type key: L{Key}
|
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|
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@return: The L{HashedEntry} that was added.
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@rtype: L{HashedEntry}
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"""
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salt = secureRandom(20)
|
||||
keyType = key.sshType()
|
||||
entry = HashedEntry(salt, _hmacedString(salt, hostname),
|
||||
keyType, key, None)
|
||||
self._added.append(entry)
|
||||
return entry
|
||||
|
||||
|
||||
def save(self):
|
||||
"""
|
||||
Save this L{KnownHostsFile} to the path it was loaded from.
|
||||
"""
|
||||
p = self._savePath.parent()
|
||||
if not p.isdir():
|
||||
p.makedirs()
|
||||
|
||||
if self._clobber:
|
||||
mode = "wb"
|
||||
else:
|
||||
mode = "ab"
|
||||
|
||||
with self._savePath.open(mode) as hostsFileObj:
|
||||
if self._added:
|
||||
hostsFileObj.write(
|
||||
b"\n".join([entry.toString() for entry in self._added]) +
|
||||
b"\n")
|
||||
self._added = []
|
||||
self._clobber = False
|
||||
|
||||
|
||||
@classmethod
|
||||
def fromPath(cls, path):
|
||||
"""
|
||||
Create a new L{KnownHostsFile}, potentially reading existing known
|
||||
hosts information from the given file.
|
||||
|
||||
@param path: A path object to use for both reading contents from and
|
||||
later saving to. If no file exists at this path, it is not an
|
||||
error; a L{KnownHostsFile} with no entries is returned.
|
||||
@type path: L{FilePath}
|
||||
|
||||
@return: A L{KnownHostsFile} initialized with entries from C{path}.
|
||||
@rtype: L{KnownHostsFile}
|
||||
"""
|
||||
knownHosts = cls(path)
|
||||
knownHosts._clobber = False
|
||||
return knownHosts
|
||||
|
||||
|
||||
|
||||
class ConsoleUI(object):
|
||||
"""
|
||||
A UI object that can ask true/false questions and post notifications on the
|
||||
console, to be used during key verification.
|
||||
"""
|
||||
def __init__(self, opener):
|
||||
"""
|
||||
@param opener: A no-argument callable which should open a console
|
||||
binary-mode file-like object to be used for reading and writing.
|
||||
This initializes the C{opener} attribute.
|
||||
@type opener: callable taking no arguments and returning a read/write
|
||||
file-like object
|
||||
"""
|
||||
self.opener = opener
|
||||
|
||||
|
||||
def prompt(self, text):
|
||||
"""
|
||||
Write the given text as a prompt to the console output, then read a
|
||||
result from the console input.
|
||||
|
||||
@param text: Something to present to a user to solicit a yes or no
|
||||
response.
|
||||
@type text: L{bytes}
|
||||
|
||||
@return: a L{Deferred} which fires with L{True} when the user answers
|
||||
'yes' and L{False} when the user answers 'no'. It may errback if
|
||||
there were any I/O errors.
|
||||
"""
|
||||
d = defer.succeed(None)
|
||||
def body(ignored):
|
||||
with closing(self.opener()) as f:
|
||||
f.write(text)
|
||||
while True:
|
||||
answer = f.readline().strip().lower()
|
||||
if answer == b'yes':
|
||||
return True
|
||||
elif answer == b'no':
|
||||
return False
|
||||
else:
|
||||
f.write(b"Please type 'yes' or 'no': ")
|
||||
return d.addCallback(body)
|
||||
|
||||
|
||||
def warn(self, text):
|
||||
"""
|
||||
Notify the user (non-interactively) of the provided text, by writing it
|
||||
to the console.
|
||||
|
||||
@param text: Some information the user is to be made aware of.
|
||||
@type text: L{bytes}
|
||||
"""
|
||||
try:
|
||||
with closing(self.opener()) as f:
|
||||
f.write(text)
|
||||
except:
|
||||
log.err()
|
||||
Loading…
Add table
Add a link
Reference in a new issue