sslutil: use saner TLS settings on Python 2.7.9

Asking for TLSv1 locks us out of TLSv1_2 etc. This is at least less
bad. Ideally we'd use ssl.create_default_context(), but that causes
more mayhem in the testsuite than I really want to deal with right
now.

mercurial/sslutil.py

@@ -1,207 +1,217
 # 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, cert_reqs=ssl.CERT_NONE,
                             ca_certs=None, serverhostname=None):
-            sslcontext = ssl.SSLContext(PROTOCOL_TLSv1)
+            # 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:
                 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, 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=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
 
     PROTOCOL_TLSv1 = 3
 
     import socket, httplib
 
     def ssl_wrap_socket(sock, keyfile, certfile, 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 = {}
     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))