sslutil: add a config knob to support TLS (default) or SSLv23 (bc) (issue4038)

Prior to this change, we default to SSLv23, which is insecure because
it allows use of SSLv2. Unfortunately, there's no constant for OpenSSL
to let us use SSLv3 or TLS - we have to pick one or the other. We
expose a knob to revert to pre-TLS SSL for the user that has an
ancient server that lacks proper TLS support.

mercurial/sslutil.py

@@ -1,157 +1,170 b''
 # 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
 
 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
-    def ssl_wrap_socket(sock, keyfile, certfile,
+    PROTOCOL_SSLv23 = ssl.PROTOCOL_SSLv23
+    PROTOCOL_TLSv1 = ssl.PROTOCOL_TLSv1
+    def ssl_wrap_socket(sock, keyfile, certfile, ssl_version=PROTOCOL_TLSv1,
                 cert_reqs=ssl.CERT_NONE, ca_certs=None):
         sslsocket = ssl.wrap_socket(sock, keyfile, certfile,
-                cert_reqs=cert_reqs, ca_certs=ca_certs)
+                                    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_SSLv23 = 2
+    PROTOCOL_TLSv1 = 3
+
     import socket, httplib
 
-    def ssl_wrap_socket(sock, key_file, cert_file,
+    def ssl_wrap_socket(sock, key_file, cert_file, ssl_version=PROTOCOL_TLSv1,
                         cert_reqs=CERT_REQUIRED, ca_certs=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, key_file, cert_file)
         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 sslkwargs(ui, host):
     cacerts = ui.config('web', 'cacerts')
+    forcetls = ui.configbool('ui', 'tls', default=True)
+    if forcetls:
+        ssl_version = PROTOCOL_TLSv1
+    else:
+        ssl_version = PROTOCOL_SSLv23
     hostfingerprint = ui.config('hostfingerprints', host)
+    kws = {'ssl_version': ssl_version,
+           }
     if cacerts and not hostfingerprint:
         cacerts = util.expandpath(cacerts)
         if not os.path.exists(cacerts):
             raise util.Abort(_('could not find web.cacerts: %s') % cacerts)
-        return {'ca_certs': cacerts,
+        kws.update({'ca_certs': cacerts,
                 'cert_reqs': CERT_REQUIRED,
-                }
-    return {}
+                    })
+    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))