123 lines
3.7 KiB
Python
123 lines
3.7 KiB
Python
# Copyright (c) Twisted Matrix Laboratories.
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# See LICENSE for details.
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"""
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A Factory for SSH servers.
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See also L{twisted.conch.openssh_compat.factory} for OpenSSH compatibility.
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Maintainer: Paul Swartz
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"""
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from __future__ import division, absolute_import
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from twisted.internet import protocol
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from twisted.python import log
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from twisted.conch import error
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from twisted.conch.ssh import (_kex, transport, userauth, connection)
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import random
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class SSHFactory(protocol.Factory):
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"""
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A Factory for SSH servers.
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"""
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protocol = transport.SSHServerTransport
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services = {
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b'ssh-userauth':userauth.SSHUserAuthServer,
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b'ssh-connection':connection.SSHConnection
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}
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def startFactory(self):
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"""
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Check for public and private keys.
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"""
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if not hasattr(self,'publicKeys'):
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self.publicKeys = self.getPublicKeys()
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if not hasattr(self,'privateKeys'):
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self.privateKeys = self.getPrivateKeys()
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if not self.publicKeys or not self.privateKeys:
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raise error.ConchError('no host keys, failing')
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if not hasattr(self,'primes'):
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self.primes = self.getPrimes()
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def buildProtocol(self, addr):
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"""
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Create an instance of the server side of the SSH protocol.
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@type addr: L{twisted.internet.interfaces.IAddress} provider
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@param addr: The address at which the server will listen.
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@rtype: L{twisted.conch.ssh.transport.SSHServerTransport}
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@return: The built transport.
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"""
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t = protocol.Factory.buildProtocol(self, addr)
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t.supportedPublicKeys = self.privateKeys.keys()
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if not self.primes:
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log.msg('disabling non-fixed-group key exchange algorithms '
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'because we cannot find moduli file')
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t.supportedKeyExchanges = [
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kexAlgorithm for kexAlgorithm in t.supportedKeyExchanges
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if _kex.isFixedGroup(kexAlgorithm) or
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_kex.isEllipticCurve(kexAlgorithm)]
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return t
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def getPublicKeys(self):
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"""
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Called when the factory is started to get the public portions of the
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servers host keys. Returns a dictionary mapping SSH key types to
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public key strings.
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@rtype: L{dict}
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"""
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raise NotImplementedError('getPublicKeys unimplemented')
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def getPrivateKeys(self):
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"""
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Called when the factory is started to get the private portions of the
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servers host keys. Returns a dictionary mapping SSH key types to
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L{twisted.conch.ssh.keys.Key} objects.
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@rtype: L{dict}
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"""
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raise NotImplementedError('getPrivateKeys unimplemented')
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def getPrimes(self):
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"""
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Called when the factory is started to get Diffie-Hellman generators and
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primes to use. Returns a dictionary mapping number of bits to lists
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of tuple of (generator, prime).
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@rtype: L{dict}
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"""
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def getDHPrime(self, bits):
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"""
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Return a tuple of (g, p) for a Diffe-Hellman process, with p being as
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close to bits bits as possible.
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@type bits: L{int}
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@rtype: L{tuple}
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"""
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primesKeys = sorted(self.primes.keys(), key=lambda i: abs(i - bits))
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realBits = primesKeys[0]
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return random.choice(self.primes[realBits])
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def getService(self, transport, service):
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"""
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Return a class to use as a service for the given transport.
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@type transport: L{transport.SSHServerTransport}
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@type service: L{bytes}
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@rtype: subclass of L{service.SSHService}
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"""
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if service == b'ssh-userauth' or hasattr(transport, 'avatar'):
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return self.services[service]
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