mercurial/sslutil.py

chgserver: invalidate the server if extensions fail to load

Previously, if extensions fail to load, chg server will just keep working
without those extensions. It will print a warning message but only if a new
server starts.

This patch invalidates the server if any extension failed to load, but still
serve the client (hopefully just) once. It will help chg pass some test cases
of test-bad-extension.t.

# sslutil.py - SSL handling for mercurial
#
# Copyright 2005, 2006, 2007, 2008 Matt Mackall <[e-mail]>
# Copyright 2006, 2007 Alexis S. L. Carvalho <[e-mail]>
# Copyright 2006 Vadim Gelfer <[e-mail]>
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.

from __future__ import absolute_import

import os
import ssl
import sys

from .i18n import _
from . import error, util

hassni = getattr(ssl, 'HAS_SNI', False)

_canloaddefaultcerts = False
try:
    ssl_context = ssl.SSLContext
    _canloaddefaultcerts = util.safehasattr(ssl_context, 'load_default_certs')

    def wrapsocket(sock, keyfile, certfile, ui, cert_reqs=ssl.CERT_NONE,
                   ca_certs=None, serverhostname=None):
        # Allow any version of SSL starting with TLSv1 and
        # up. Note that specifying TLSv1 here prohibits use of
        # newer standards (like TLSv1_2), so this is the right way
        # to do this. Note that in the future it'd be better to
        # support using ssl.create_default_context(), which sets
        # up a bunch of things in smart ways (strong ciphers,
        # protocol versions, etc) and is upgraded by Python
        # maintainers for us, but that breaks too many things to
        # do it in a hurry.
        sslcontext = ssl.SSLContext(ssl.PROTOCOL_SSLv23)
        sslcontext.options |= ssl.OP_NO_SSLv2 | ssl.OP_NO_SSLv3
        if certfile is not None:
            def password():
                f = keyfile or certfile
                return ui.getpass(_('passphrase for %s: ') % f, '')
            sslcontext.load_cert_chain(certfile, keyfile, password)
        sslcontext.verify_mode = cert_reqs
        if ca_certs is not None:
            sslcontext.load_verify_locations(cafile=ca_certs)
        elif _canloaddefaultcerts:
            sslcontext.load_default_certs()

        sslsocket = sslcontext.wrap_socket(sock, server_hostname=serverhostname)
        # check if wrap_socket failed silently because socket had been
        # closed
        # - see http://bugs.python.org/issue13721
        if not sslsocket.cipher():
            raise error.Abort(_('ssl connection failed'))
        return sslsocket
except AttributeError:
    def wrapsocket(sock, keyfile, certfile, ui, cert_reqs=ssl.CERT_NONE,
                   ca_certs=None, serverhostname=None):
        sslsocket = ssl.wrap_socket(sock, keyfile, certfile,
                                    cert_reqs=cert_reqs, ca_certs=ca_certs,
                                    ssl_version=ssl.PROTOCOL_TLSv1)
        # check if wrap_socket failed silently because socket had been
        # closed
        # - see http://bugs.python.org/issue13721
        if not sslsocket.cipher():
            raise error.Abort(_('ssl connection failed'))
        return sslsocket

def _verifycert(cert, hostname):
    '''Verify that cert (in socket.getpeercert() format) matches hostname.
    CRLs is not handled.

    Returns error message if any problems are found and None on success.
    '''
    if not cert:
        return _('no certificate received')
    dnsname = hostname.lower()
    def matchdnsname(certname):
        return (certname == dnsname or
                '.' in dnsname and certname == '*.' + dnsname.split('.', 1)[1])

    san = cert.get('subjectAltName', [])
    if san:
        certnames = [value.lower() for key, value in san if key == 'DNS']
        for name in certnames:
            if matchdnsname(name):
                return None
        if certnames:
            return _('certificate is for %s') % ', '.join(certnames)

    # subject is only checked when subjectAltName is empty
    for s in cert.get('subject', []):
        key, value = s[0]
        if key == 'commonName':
            try:
                # 'subject' entries are unicode
                certname = value.lower().encode('ascii')
            except UnicodeEncodeError:
                return _('IDN in certificate not supported')
            if matchdnsname(certname):
                return None
            return _('certificate is for %s') % certname
    return _('no commonName or subjectAltName found in certificate')


# CERT_REQUIRED means fetch the cert from the server all the time AND
# validate it against the CA store provided in web.cacerts.

def _plainapplepython():
    """return true if this seems to be a pure Apple Python that
    * is unfrozen and presumably has the whole mercurial module in the file
      system
    * presumably is an Apple Python that uses Apple OpenSSL which has patches
      for using system certificate store CAs in addition to the provided
      cacerts file
    """
    if sys.platform != 'darwin' or util.mainfrozen() or not sys.executable:
        return False
    exe = os.path.realpath(sys.executable).lower()
    return (exe.startswith('/usr/bin/python') or
            exe.startswith('/system/library/frameworks/python.framework/'))

def _defaultcacerts():
    """return path to CA certificates; None for system's store; ! to disable"""
    if _plainapplepython():
        dummycert = os.path.join(os.path.dirname(__file__), 'dummycert.pem')
        if os.path.exists(dummycert):
            return dummycert
    if _canloaddefaultcerts:
        return None
    return '!'

def sslkwargs(ui, host):
    kws = {'ui': ui}
    hostfingerprint = ui.config('hostfingerprints', host)
    if hostfingerprint:
        return kws
    cacerts = ui.config('web', 'cacerts')
    if cacerts == '!':
        pass
    elif cacerts:
        cacerts = util.expandpath(cacerts)
        if not os.path.exists(cacerts):
            raise error.Abort(_('could not find web.cacerts: %s') % cacerts)
    else:
        cacerts = _defaultcacerts()
        if cacerts and cacerts != '!':
            ui.debug('using %s to enable OS X system CA\n' % cacerts)
        ui.setconfig('web', 'cacerts', cacerts, 'defaultcacerts')
    if cacerts != '!':
        kws.update({'ca_certs': cacerts,
                    'cert_reqs': ssl.CERT_REQUIRED,
                    })
    return kws

class validator(object):
    def __init__(self, ui, host):
        self.ui = ui
        self.host = host

    def __call__(self, sock, strict=False):
        host = self.host
        cacerts = self.ui.config('web', 'cacerts')
        hostfingerprints = self.ui.configlist('hostfingerprints', host)

        if not sock.cipher(): # work around http://bugs.python.org/issue13721
            raise error.Abort(_('%s ssl connection error') % host)
        try:
            peercert = sock.getpeercert(True)
            peercert2 = sock.getpeercert()
        except AttributeError:
            raise error.Abort(_('%s ssl connection error') % host)

        if not peercert:
            raise error.Abort(_('%s certificate error: '
                               'no certificate received') % host)
        peerfingerprint = util.sha1(peercert).hexdigest()
        nicefingerprint = ":".join([peerfingerprint[x:x + 2]
            for x in xrange(0, len(peerfingerprint), 2)])
        if hostfingerprints:
            fingerprintmatch = False
            for hostfingerprint in hostfingerprints:
                if peerfingerprint.lower() == \
                        hostfingerprint.replace(':', '').lower():
                    fingerprintmatch = True
                    break
            if not fingerprintmatch:
                raise error.Abort(_('certificate for %s has unexpected '
                                   'fingerprint %s') % (host, nicefingerprint),
                                 hint=_('check hostfingerprint configuration'))
            self.ui.debug('%s certificate matched fingerprint %s\n' %
                          (host, nicefingerprint))
        elif cacerts != '!':
            msg = _verifycert(peercert2, host)
            if msg:
                raise error.Abort(_('%s certificate error: %s') % (host, msg),
                                 hint=_('configure hostfingerprint %s or use '
                                        '--insecure to connect insecurely') %
                                      nicefingerprint)
            self.ui.debug('%s certificate successfully verified\n' % host)
        elif strict:
            raise error.Abort(_('%s certificate with fingerprint %s not '
                               'verified') % (host, nicefingerprint),
                             hint=_('check hostfingerprints or web.cacerts '
                                     'config setting'))
        else:
            self.ui.warn(_('warning: %s certificate with fingerprint %s not '
                           'verified (check hostfingerprints or web.cacerts '
                           'config setting)\n') %
                         (host, nicefingerprint))