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# sslutil.py - SSL handling for mercurial
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#
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# Copyright 2005, 2006, 2007, 2008 Matt Mackall <mpm@selenic.com>
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# Copyright 2006, 2007 Alexis S. L. Carvalho <alexis@cecm.usp.br>
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# Copyright 2006 Vadim Gelfer <vadim.gelfer@gmail.com>
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#
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# This software may be used and distributed according to the terms of the
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# GNU General Public License version 2 or any later version.
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from __future__ import absolute_import
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import os
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import ssl
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import sys
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from .i18n import _
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from . import (
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error,
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util,
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)
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# Python 2.7.9+ overhauled the built-in SSL/TLS features of Python. It added
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# support for TLS 1.1, TLS 1.2, SNI, system CA stores, etc. These features are
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# all exposed via the "ssl" module.
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#
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# Depending on the version of Python being used, SSL/TLS support is either
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# modern/secure or legacy/insecure. Many operations in this module have
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# separate code paths depending on support in Python.
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hassni = getattr(ssl, 'HAS_SNI', False)
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try:
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OP_NO_SSLv2 = ssl.OP_NO_SSLv2
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OP_NO_SSLv3 = ssl.OP_NO_SSLv3
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except AttributeError:
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OP_NO_SSLv2 = 0x1000000
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OP_NO_SSLv3 = 0x2000000
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try:
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# ssl.SSLContext was added in 2.7.9 and presence indicates modern
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# SSL/TLS features are available.
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SSLContext = ssl.SSLContext
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modernssl = True
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_canloaddefaultcerts = util.safehasattr(SSLContext, 'load_default_certs')
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except AttributeError:
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modernssl = False
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_canloaddefaultcerts = False
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# We implement SSLContext using the interface from the standard library.
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class SSLContext(object):
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# ssl.wrap_socket gained the "ciphers" named argument in 2.7.
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_supportsciphers = sys.version_info >= (2, 7)
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def __init__(self, protocol):
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# From the public interface of SSLContext
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self.protocol = protocol
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self.check_hostname = False
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self.options = 0
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self.verify_mode = ssl.CERT_NONE
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# Used by our implementation.
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self._certfile = None
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self._keyfile = None
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self._certpassword = None
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self._cacerts = None
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self._ciphers = None
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def load_cert_chain(self, certfile, keyfile=None, password=None):
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self._certfile = certfile
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self._keyfile = keyfile
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self._certpassword = password
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def load_default_certs(self, purpose=None):
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pass
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def load_verify_locations(self, cafile=None, capath=None, cadata=None):
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if capath:
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raise error.Abort('capath not supported')
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if cadata:
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raise error.Abort('cadata not supported')
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self._cacerts = cafile
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def set_ciphers(self, ciphers):
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if not self._supportsciphers:
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raise error.Abort('setting ciphers not supported')
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self._ciphers = ciphers
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def wrap_socket(self, socket, server_hostname=None, server_side=False):
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# server_hostname is unique to SSLContext.wrap_socket and is used
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# for SNI in that context. So there's nothing for us to do with it
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# in this legacy code since we don't support SNI.
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args = {
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'keyfile': self._keyfile,
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'certfile': self._certfile,
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'server_side': server_side,
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'cert_reqs': self.verify_mode,
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'ssl_version': self.protocol,
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'ca_certs': self._cacerts,
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}
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if self._supportsciphers:
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args['ciphers'] = self._ciphers
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return ssl.wrap_socket(socket, **args)
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def wrapsocket(sock, keyfile, certfile, ui, cert_reqs=ssl.CERT_NONE,
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ca_certs=None, serverhostname=None):
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"""Add SSL/TLS to a socket.
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This is a glorified wrapper for ``ssl.wrap_socket()``. It makes sane
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choices based on what security options are available.
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In addition to the arguments supported by ``ssl.wrap_socket``, we allow
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the following additional arguments:
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* serverhostname - The expected hostname of the remote server. If the
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server (and client) support SNI, this tells the server which certificate
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to use.
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"""
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if not serverhostname:
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raise error.Abort('serverhostname argument is required')
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# Despite its name, PROTOCOL_SSLv23 selects the highest protocol
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# that both ends support, including TLS protocols. On legacy stacks,
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# the highest it likely goes in TLS 1.0. On modern stacks, it can
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# support TLS 1.2.
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#
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# The PROTOCOL_TLSv* constants select a specific TLS version
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# only (as opposed to multiple versions). So the method for
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# supporting multiple TLS versions is to use PROTOCOL_SSLv23 and
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# disable protocols via SSLContext.options and OP_NO_* constants.
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# However, SSLContext.options doesn't work unless we have the
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# full/real SSLContext available to us.
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#
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# SSLv2 and SSLv3 are broken. We ban them outright.
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if modernssl:
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protocol = ssl.PROTOCOL_SSLv23
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else:
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protocol = ssl.PROTOCOL_TLSv1
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# TODO use ssl.create_default_context() on modernssl.
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sslcontext = SSLContext(protocol)
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# This is a no-op on old Python.
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sslcontext.options |= OP_NO_SSLv2 | OP_NO_SSLv3
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# This still works on our fake SSLContext.
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sslcontext.verify_mode = cert_reqs
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if certfile is not None:
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def password():
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f = keyfile or certfile
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return ui.getpass(_('passphrase for %s: ') % f, '')
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sslcontext.load_cert_chain(certfile, keyfile, password)
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if ca_certs is not None:
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sslcontext.load_verify_locations(cafile=ca_certs)
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caloaded = True
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else:
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# This is a no-op on old Python.
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sslcontext.load_default_certs()
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caloaded = _canloaddefaultcerts
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sslsocket = sslcontext.wrap_socket(sock, server_hostname=serverhostname)
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# check if wrap_socket failed silently because socket had been
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# closed
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# - see http://bugs.python.org/issue13721
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if not sslsocket.cipher():
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raise error.Abort(_('ssl connection failed'))
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sslsocket._hgstate = {
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'caloaded': caloaded,
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}
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return sslsocket
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def _verifycert(cert, hostname):
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'''Verify that cert (in socket.getpeercert() format) matches hostname.
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CRLs is not handled.
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Returns error message if any problems are found and None on success.
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'''
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if not cert:
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return _('no certificate received')
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dnsname = hostname.lower()
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def matchdnsname(certname):
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return (certname == dnsname or
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'.' in dnsname and certname == '*.' + dnsname.split('.', 1)[1])
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san = cert.get('subjectAltName', [])
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if san:
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certnames = [value.lower() for key, value in san if key == 'DNS']
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for name in certnames:
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if matchdnsname(name):
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return None
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if certnames:
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return _('certificate is for %s') % ', '.join(certnames)
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# subject is only checked when subjectAltName is empty
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for s in cert.get('subject', []):
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key, value = s[0]
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if key == 'commonName':
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try:
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# 'subject' entries are unicode
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certname = value.lower().encode('ascii')
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except UnicodeEncodeError:
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return _('IDN in certificate not supported')
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if matchdnsname(certname):
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return None
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return _('certificate is for %s') % certname
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return _('no commonName or subjectAltName found in certificate')
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# CERT_REQUIRED means fetch the cert from the server all the time AND
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# validate it against the CA store provided in web.cacerts.
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def _plainapplepython():
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"""return true if this seems to be a pure Apple Python that
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* is unfrozen and presumably has the whole mercurial module in the file
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system
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* presumably is an Apple Python that uses Apple OpenSSL which has patches
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for using system certificate store CAs in addition to the provided
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cacerts file
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"""
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if sys.platform != 'darwin' or util.mainfrozen() or not sys.executable:
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return False
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exe = os.path.realpath(sys.executable).lower()
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return (exe.startswith('/usr/bin/python') or
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exe.startswith('/system/library/frameworks/python.framework/'))
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def _defaultcacerts():
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"""return path to default CA certificates or None."""
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if _plainapplepython():
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dummycert = os.path.join(os.path.dirname(__file__), 'dummycert.pem')
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if os.path.exists(dummycert):
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return dummycert
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return None
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def sslkwargs(ui, host):
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"""Determine arguments to pass to wrapsocket().
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``host`` is the hostname being connected to.
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"""
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kws = {'ui': ui}
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# If a host key fingerprint is on file, it is the only thing that matters
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# and CA certs don't come into play.
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hostfingerprint = ui.config('hostfingerprints', host)
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if hostfingerprint:
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return kws
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# The code below sets up CA verification arguments. If --insecure is
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# used, we don't take CAs into consideration, so return early.
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if ui.insecureconnections:
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return kws
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cacerts = ui.config('web', 'cacerts')
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# If a value is set in the config, validate against a path and load
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# and require those certs.
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if cacerts:
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cacerts = util.expandpath(cacerts)
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if not os.path.exists(cacerts):
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raise error.Abort(_('could not find web.cacerts: %s') % cacerts)
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kws.update({'ca_certs': cacerts,
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'cert_reqs': ssl.CERT_REQUIRED})
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return kws
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# No CAs in config. See if we can load defaults.
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cacerts = _defaultcacerts()
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# We found an alternate CA bundle to use. Load it.
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if cacerts:
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ui.debug('using %s to enable OS X system CA\n' % cacerts)
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ui.setconfig('web', 'cacerts', cacerts, 'defaultcacerts')
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kws.update({'ca_certs': cacerts,
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'cert_reqs': ssl.CERT_REQUIRED})
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return kws
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# FUTURE this can disappear once wrapsocket() is secure by default.
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if _canloaddefaultcerts:
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kws['cert_reqs'] = ssl.CERT_REQUIRED
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return kws
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return kws
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class validator(object):
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def __init__(self, ui, host):
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self.ui = ui
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self.host = host
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def __call__(self, sock, strict=False):
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host = self.host
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if not sock.cipher(): # work around http://bugs.python.org/issue13721
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raise error.Abort(_('%s ssl connection error') % host)
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try:
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peercert = sock.getpeercert(True)
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peercert2 = sock.getpeercert()
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except AttributeError:
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raise error.Abort(_('%s ssl connection error') % host)
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if not peercert:
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raise error.Abort(_('%s certificate error: '
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'no certificate received') % host)
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# If a certificate fingerprint is pinned, use it and only it to
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# validate the remote cert.
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hostfingerprints = self.ui.configlist('hostfingerprints', host)
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peerfingerprint = util.sha1(peercert).hexdigest()
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nicefingerprint = ":".join([peerfingerprint[x:x + 2]
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for x in xrange(0, len(peerfingerprint), 2)])
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if hostfingerprints:
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fingerprintmatch = False
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for hostfingerprint in hostfingerprints:
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if peerfingerprint.lower() == \
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hostfingerprint.replace(':', '').lower():
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fingerprintmatch = True
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break
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if not fingerprintmatch:
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raise error.Abort(_('certificate for %s has unexpected '
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'fingerprint %s') % (host, nicefingerprint),
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hint=_('check hostfingerprint configuration'))
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self.ui.debug('%s certificate matched fingerprint %s\n' %
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(host, nicefingerprint))
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return
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# If insecure connections were explicitly requested via --insecure,
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# print a warning and do no verification.
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#
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# It may seem odd that this is checked *after* host fingerprint pinning.
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# This is for backwards compatibility (for now). The message is also
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# the same as below for BC.
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if self.ui.insecureconnections:
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self.ui.warn(_('warning: %s certificate with fingerprint %s not '
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'verified (check hostfingerprints or web.cacerts '
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'config setting)\n') %
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(host, nicefingerprint))
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return
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if not sock._hgstate['caloaded']:
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if strict:
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raise error.Abort(_('%s certificate with fingerprint %s not '
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'verified') % (host, nicefingerprint),
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hint=_('check hostfingerprints or '
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'web.cacerts config setting'))
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else:
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self.ui.warn(_('warning: %s certificate with fingerprint %s '
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'not verified (check hostfingerprints or '
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'web.cacerts config setting)\n') %
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(host, nicefingerprint))
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return
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msg = _verifycert(peercert2, host)
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if msg:
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raise error.Abort(_('%s certificate error: %s') % (host, msg),
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hint=_('configure hostfingerprint %s or use '
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'--insecure to connect insecurely') %
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nicefingerprint)
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