annotate mercurial/sslutil.py @ 23834:bf07c19b4c82

https: support tls sni (server name indication) for https urls (issue3090)

SNI is a common way of sharing servers across multiple domains using separate
SSL certificates. As of Python 2.7.9 SSLContext has been backported from
Python 3. This patch changes sslutil's ssl_wrap_socket to use SSLContext and
take a server hostname as and argument. It also changes the url module to make
use of this argument.

The new code for 2.7.9 achieves it's task by attempting to get the SSLContext
object from the ssl module. If this fails the try/except goes back to what was
there before with the exception that the ssl_wrap_socket functions take a
server_hostname argument that doesn't get used. Assuming the SSLContext
exists, the arguments to wrap_socket at the module level are emulated on the
SSLContext. The SSLContext is initialized with the specified ssl_version. If
certfile is not None load_cert_chain is called with certfile and keyfile.
keyfile being None is not a problem, load_cert_chain will simply expect the
private key to be in the certificate file. verify_mode is set to cert_reqs. If
ca_certs is not None load_verify_locations is called with ca_certs as the
cafile. Finally the wrap_socket method of the SSLContext is called with the
socket and server hostname.

Finally, this fails test-check-commit-hg.t because the "new" function
ssl_wrap_socket has underscores in its names and underscores in its arguments.
All the underscore identifiers are taken from the other functions and as such
can't be changed to match naming conventions.

# 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 _
try:
    # avoid using deprecated/broken FakeSocket in python 2.6
    import ssl
    CERT_REQUIRED = ssl.CERT_REQUIRED
    PROTOCOL_TLSv1 = ssl.PROTOCOL_TLSv1
    try:
        ssl_context = ssl.SSLContext

        def ssl_wrap_socket(sock, keyfile, certfile, ssl_version=PROTOCOL_TLSv1,
                            cert_reqs=ssl.CERT_NONE, ca_certs=None,
                            serverhostname=None):
            sslcontext = ssl.SSLContext(ssl_version)
            if certfile is not None:
                sslcontext.load_cert_chain(certfile, keyfile)
            sslcontext.verify_mode = cert_reqs
            if ca_certs is not None:
                sslcontext.load_verify_locations(cafile=ca_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, ssl_version=PROTOCOL_TLSv1,
                            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_version)
            # 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

    PROTOCOL_TLSv1 = 3

    import socket, httplib

    def ssl_wrap_socket(sock, keyfile, certfile, ssl_version=PROTOCOL_TLSv1,
                        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():
        return False
    exe = (sys.executable or '').lower()
    return (exe.startswith('/usr/bin/python') or
            exe.startswith('/system/library/frameworks/python.framework/'))

def sslkwargs(ui, host):
    kws = {'ssl_version': PROTOCOL_TLSv1,
           }
    hostfingerprint = ui.config('hostfingerprints', host)
    if hostfingerprint:
        return kws
    cacerts = ui.config('web', 'cacerts')
    if cacerts:
        cacerts = util.expandpath(cacerts)
        if not os.path.exists(cacerts):
            raise util.Abort(_('could not find web.cacerts: %s') % cacerts)
    elif cacerts is None and _plainapplepython():
        dummycert = os.path.join(os.path.dirname(__file__), 'dummycert.pem')
        if os.path.exists(dummycert):
            ui.debug('using %s to enable OS X system CA\n' % dummycert)
            ui.setconfig('web', 'cacerts', dummycert, 'dummy')
            cacerts = dummycert
    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))