tests/dummysmtpd.py

sslutil: prevent CRIME

ssl.create_default_context() disables compression on the TLS channel
in order to prevent CRIME. I think we should follow CPython's lead
and attempt to disable channel compression in order to help prevent
information leakage.

Sadly, I don't think there is anything we can do on Python versions
that don't have an SSLContext, as there is no way to set channel
options with the limited ssl API.

#!/usr/bin/env python

"""dummy SMTP server for use in tests"""

from __future__ import absolute_import

import asyncore
import optparse
import smtpd
import ssl
import sys

from mercurial import (
    cmdutil,
    sslutil,
    ui as uimod,
)

def log(msg):
    sys.stdout.write(msg)
    sys.stdout.flush()

class dummysmtpserver(smtpd.SMTPServer):
    def __init__(self, localaddr):
        smtpd.SMTPServer.__init__(self, localaddr, remoteaddr=None)

    def process_message(self, peer, mailfrom, rcpttos, data):
        log('%s from=%s to=%s\n' % (peer[0], mailfrom, ', '.join(rcpttos)))

class dummysmtpsecureserver(dummysmtpserver):
    def __init__(self, localaddr, certfile):
        dummysmtpserver.__init__(self, localaddr)
        self._certfile = certfile

    def handle_accept(self):
        pair = self.accept()
        if not pair:
            return
        conn, addr = pair
        ui = uimod.ui()
        try:
            # wrap_socket() would block, but we don't care
            conn = sslutil.wrapserversocket(conn, ui, certfile=self._certfile)
        except ssl.SSLError:
            log('%s ssl error\n' % addr[0])
            conn.close()
            return
        smtpd.SMTPChannel(self, conn, addr)

def run():
    try:
        asyncore.loop()
    except KeyboardInterrupt:
        pass

def main():
    op = optparse.OptionParser()
    op.add_option('-d', '--daemon', action='store_true')
    op.add_option('--daemon-postexec', action='append')
    op.add_option('-p', '--port', type=int, default=8025)
    op.add_option('-a', '--address', default='localhost')
    op.add_option('--pid-file', metavar='FILE')
    op.add_option('--tls', choices=['none', 'smtps'], default='none')
    op.add_option('--certificate', metavar='FILE')

    opts, args = op.parse_args()
    if opts.tls == 'smtps' and not opts.certificate:
        op.error('--certificate must be specified')

    addr = (opts.address, opts.port)
    def init():
        if opts.tls == 'none':
            dummysmtpserver(addr)
        else:
            dummysmtpsecureserver(addr, opts.certificate)
        log('listening at %s:%d\n' % addr)

    cmdutil.service(vars(opts), initfn=init, runfn=run,
                    runargs=[sys.executable, __file__] + sys.argv[1:])

if __name__ == '__main__':
    main()