# sslutil.py - SSL handling for mercurial

#

# Copyright 2005, 2006, 2007, 2008 Matt Mackall <mpm@selenic.com>

# Copyright 2006, 2007 Alexis S. L. Carvalho <alexis@cecm.usp.br>

# Copyright 2006 Vadim Gelfer <vadim.gelfer@gmail.com>

#

# 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 (

    error,

    util,

)

# Python 2.7.9+ overhauled the built-in SSL/TLS features of Python. It added

# support for TLS 1.1, TLS 1.2, SNI, system CA stores, etc. These features are

# all exposed via the "ssl" module.

#

# Depending on the version of Python being used, SSL/TLS support is either

# modern/secure or legacy/insecure. Many operations in this module have

# separate code paths depending on support in Python.

hassni = getattr(ssl, 'HAS_SNI', False)

try:

    OP_NO_SSLv2 = ssl.OP_NO_SSLv2

    OP_NO_SSLv3 = ssl.OP_NO_SSLv3

except AttributeError:

    OP_NO_SSLv2 = 0x1000000

    OP_NO_SSLv3 = 0x2000000

_canloaddefaultcerts = False

try:

    # ssl.SSLContext was added in 2.7.9 and presence indicates modern

    # SSL/TLS features are available.

    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 |= OP_NO_SSLv2 | 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 error.Abort(_('ssl connection failed'))

        return sslsocket

except AttributeError:

    # We don't have a modern version of the "ssl" module and are running

    # Python <2.7.9.

    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 error.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 error.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')

        hostfingerprints = self.ui.configlist('hostfingerprints', host)

        if not sock.cipher(): # work around http://bugs.python.org/issue13721

            raise error.Abort(_('%s ssl connection error') % host)

        try:

            peercert = sock.getpeercert(True)

            peercert2 = sock.getpeercert()

        except AttributeError:

            raise error.Abort(_('%s ssl connection error') % host)

        if not peercert:

            raise error.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 hostfingerprints:

            fingerprintmatch = False

            for hostfingerprint in hostfingerprints:

                if peerfingerprint.lower() == \

                        hostfingerprint.replace(':', '').lower():

                    fingerprintmatch = True

                    break

            if not fingerprintmatch:

                raise error.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 error.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 error.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))