mercurial/sslutil.py

hgweb: move some config options to requestcontext

Various config options from the repository were stored on the
hgweb instance. While unlikely, there could be race conditions between
a new request updating these values and an in-flight request seeing both
old and new values, leading to weird results.

We move some of options/attributes from hgweb to requestcontext.

As part of this, we establish config* helpers on requestcontext. As
part of the move, we changed int() casts to configint() calls. The
int() usage likely predates the existence of configint().

We also removed config option updating from once every refresh to every
request. I don't believe obtaining config options is expensive enough to
warrant only doing when the repository has changed.

The excessive use of object.__setattr__ is unfortunate. But it will
eventually disappear once the proxy is no longer necessary.

# 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 util

_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 util.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 util.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 util.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')
        hostfingerprint = self.ui.config('hostfingerprints', host)

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

        if not peercert:
            raise util.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 hostfingerprint:
            if peerfingerprint.lower() != \
                    hostfingerprint.replace(':', '').lower():
                raise util.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 util.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 util.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))