mercurial/sslutil.py

ssl: prompt passphrase of client key file via ui.getpass() (issue4648)

This is necessary to communicate with third-party tools through command-server
channel. This requires SSLContext backported to Python 2.7.9+.

It doesn't look nice to pass ui by sslkwargs, but I think it is the only way
to do without touching various client codes including httpclient (aka http2).
ui is mandatory if certfile is specified, so it has no default value.

BTW, test-check-commit-hg.t complains that ssl_wrap_socket() has foo_bar
naming. Should I bulk-replace it to sslwrapsocket() ?

# 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.
import os, sys

from mercurial import util
from mercurial.i18n import _

_canloaddefaultcerts = False
try:
    # avoid using deprecated/broken FakeSocket in python 2.6
    import ssl
    CERT_REQUIRED = ssl.CERT_REQUIRED
    try:
        ssl_context = ssl.SSLContext
        _canloaddefaultcerts = util.safehasattr(ssl_context,
                                                'load_default_certs')

        def ssl_wrap_socket(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 ssl_wrap_socket(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
except ImportError:
    CERT_REQUIRED = 2

    import socket, httplib

    def ssl_wrap_socket(sock, keyfile, certfile, ui,
                        cert_reqs=CERT_REQUIRED,
                        ca_certs=None, serverhostname=None):
        if not util.safehasattr(socket, 'ssl'):
            raise util.Abort(_('Python SSL support not found'))
        if ca_certs:
            raise util.Abort(_(
                'certificate checking requires Python 2.6'))

        ssl = socket.ssl(sock, keyfile, certfile)
        return httplib.FakeSocket(sock, ssl)

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.
#
# We COMPLETELY ignore CERT_REQUIRED on Python <= 2.5, as it's totally
# busted on those versions.

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': 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 getattr(sock, 'getpeercert', False): # python 2.5 ?
            if hostfingerprint:
                raise util.Abort(_("host fingerprint for %s can't be "
                                   "verified (Python too old)") % host)
            if strict:
                raise util.Abort(_("certificate for %s can't be verified "
                                   "(Python too old)") % host)
            if self.ui.configbool('ui', 'reportoldssl', True):
                self.ui.warn(_("warning: certificate for %s can't be verified "
                               "(Python too old)\n") % host)
            return

        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))