All, This is a very very horrible bit of code (stupid undocumented RCP junk), but a basic single-file remote -> local SCP can be done using the attached code. It's clearly as dumb as a box of rocks, but seems to work against OpenSSH and Cisco IOS, so is fine for what we need. If anyone knows why the sftp stuff in it doesn't work that would be useful. Anyway, hope it's helpful to someone. If I get time over or after xmas I'll clean it up - it seems pretty clear to me how to make the code pretty modular without it descending into the mess that OpenSSH and Putty's SCP/SFTP code has become (with the greatest of respect to the developers involved of course) #!/usr/bin/env python from twisted.conch.ssh import transport, userauth, connection, channel from twisted.conch.ssh.common import NS from twisted.internet import defer, protocol, reactor from twisted.python import log import sys, os, getpass USER, PASS, HOST, CMD, SRC, DST = None, None, None, None, None, None # The "Transport" is the crypto layer on top of port 22 class Transport(transport.SSHClientTransport): def verifyHostKey(self, hostKey, fingerprint): # For info only log.msg('host key fingerprint: %s' % fingerprint) # FIXME: this is insecure return defer.succeed(1) def connectionSecure(self): # Once we're secure (server key valid) we ask for userauth service # on a new "connection" object self.requestService(UserAuth(USER, Connection())) class UserAuth(userauth.SSHUserAuthClient): def getPassword(self): # Ack! Globals! return defer.succeed(PASS) def getPublicKey(self): # returning None means always use username/password auth return class Connection(connection.SSHConnection): def serviceStarted(self): # Once userauth has succeeded we ask for a channel on this # connection self.openChannel(ScpChannel(2**16, 2**15, self)) class XferChannelBase(channel.SSHChannel): name = 'session' state = None todo = 0 buf = '' def openFailed(self, reason): log.err(reason) def channelOpen(self, data): # Might display/process welcome screen self.welcome = data # We might be an SCP or SFTP requests if 'scp' in CMD or CMD.startswith('/'): kind = 'exec' else: kind = 'subsystem' # Call our handler d = self.conn.sendRequest(self, kind, NS(CMD), wantReply=1) d.addCallbacks(self.channelOpened, log.err) def closed(self): self.loseConnection() reactor.stop() class SftpChannel(XferChannelBase): def channelOpened(self, data): log.msg("channelOpened: %r" % (data,)) self.client = filetransfer.FileTransferClient() self.client.makeConnection(self) self.dataReceived = self.client.dataReceived d = self.client.openFile(SRC, filetransfer.FXF_READ, {}) d.addCallbacks(self.fileOpened, log.err) def fileOpened(self, rfile): rfile.getAttrs().addCallbacks(self.fileStatted, log.err, (rfile,)) def fileStatted(self, attrs, rfile): rfile.readChunk(0, 4096).addCallbacks(self.did_read, log.err, (rfile, 0, attrs['size'])).addCallback(self.done) def did_read(self, data, f, pos, todo): if len(data)>todo: log.msg("got %i bytes more than expected, trimming" % (len(data)-todo,)) data = data[:todo] DST.write(data) todo -= len(data) pos += len(data) if todo<=0: return pos return f.readChunk(pos, 4096).addCallbacks(self.did_read, log.err, (f, pos, todo)) def done(self, l): log.msg("done %i bytes" % (l,)) self.loseConnection() class ScpChannel(XferChannelBase): def channelOpened(self, data): # once the scp is exec'ed, start the SCP transfer self.write('\0') # we're a state machine self.state = 'waiting' def dataReceived(self, data): #log.msg('dataReceived: %s %r' % (self.state, data)) # What we do with the data depends on where we are if self.state=='waiting': # we've started the transfer, and are expecting a C # Coctalperms size filename\n # might not get it all at once, buffer self.buf += data if not self.buf.endswith('\n'): return b = self.buf self.buf = '' # Must be a C if not b.startswith('C'): log.msg("expecting C command: %r" % (self.buf,)) self.loseConnection() return # Get the file info p, l, n = b[1:-1].split(' ') perms = int(p, 8) self.todo = int(l) log.msg("getting file %s mode %s len %i" % (n, oct(perms), self.todo)) # Tell the far end to start sending the content self.state = 'receiving' self.write('\0') elif self.state=='receiving': # we've started the file body #log.msg('got %i bytes' % (len(data),)) if len(data)>self.todo: extra = data[self.todo:] data = data[:self.todo] if extra!='\0': log.msg("got %i more bytes than we expected, ignoring: %r" % (len(extra), extra)) DST.write(data) self.todo -= len(data) if self.todo<=0: log.msg('done') self.loseConnection() else: log.err("dataReceived in unknown state: %r" % (self.state,)) def usage(ex): print >>sys.stderr, """%s: [user[:pass]@]hostname:sourcefile destfile""" % (sys.argv[0],) if ex: sys.exit(ex) if __name__=='__main__': args = sys.argv[1:] if len(args)<2: usage(1) SRC = args[0] DST = args[1] if '@' in SRC: USER, SRC = SRC.split('@', 1) else: USER = os.environ['USERNAME'] if not ':' in SRC: usage(1) HOST, SRC = SRC.split(':', 1) if ':' in USER: USER, PASS = USER.split(':', 1) else: PASS = getpass.getpass('password for %s@%s: ' % (USER, HOST)) DST = open(DST, 'wb') if 'sftp' in sys.argv[0]: CMD = 'sftp' else: CMD = 'scp -f %s' % (SRC,) protocol.ClientCreator(reactor, Transport).connectTCP(HOST, 22) log.startLogging(sys.stderr) reactor.run()