sslutil: print the fingerprint from the last hash used
Before, we would always print the unprefixed SHA-1 fingerprint when
fingerprint comparison failed. Now, we print the fingerprint of the
last hash used, including the prefix if necessary. This helps ensure
that the printed hash type matches what is in the user configuration.
There are still some cases where this can print a mismatched hash type.
e.g. if there are both SHA-1 and SHA-256 fingerprints in the config,
we could print a SHA-1 hash if it comes after the SHA-256 hash. But
I'm inclined to ignore this edge case.
While I was here, the "section" variable assignment has been moved to
just above where it is used because it is now only needed for this
error message and it makes the code easier to read.
# 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
try:
# ssl.SSLContext was added in 2.7.9 and presence indicates modern
# SSL/TLS features are available.
SSLContext = ssl.SSLContext
modernssl = True
_canloaddefaultcerts = util.safehasattr(SSLContext, 'load_default_certs')
except AttributeError:
modernssl = False
_canloaddefaultcerts = False
# We implement SSLContext using the interface from the standard library.
class SSLContext(object):
# ssl.wrap_socket gained the "ciphers" named argument in 2.7.
_supportsciphers = sys.version_info >= (2, 7)
def __init__(self, protocol):
# From the public interface of SSLContext
self.protocol = protocol
self.check_hostname = False
self.options = 0
self.verify_mode = ssl.CERT_NONE
# Used by our implementation.
self._certfile = None
self._keyfile = None
self._certpassword = None
self._cacerts = None
self._ciphers = None
def load_cert_chain(self, certfile, keyfile=None, password=None):
self._certfile = certfile
self._keyfile = keyfile
self._certpassword = password
def load_default_certs(self, purpose=None):
pass
def load_verify_locations(self, cafile=None, capath=None, cadata=None):
if capath:
raise error.Abort('capath not supported')
if cadata:
raise error.Abort('cadata not supported')
self._cacerts = cafile
def set_ciphers(self, ciphers):
if not self._supportsciphers:
raise error.Abort('setting ciphers not supported')
self._ciphers = ciphers
def wrap_socket(self, socket, server_hostname=None, server_side=False):
# server_hostname is unique to SSLContext.wrap_socket and is used
# for SNI in that context. So there's nothing for us to do with it
# in this legacy code since we don't support SNI.
args = {
'keyfile': self._keyfile,
'certfile': self._certfile,
'server_side': server_side,
'cert_reqs': self.verify_mode,
'ssl_version': self.protocol,
'ca_certs': self._cacerts,
}
if self._supportsciphers:
args['ciphers'] = self._ciphers
return ssl.wrap_socket(socket, **args)
def _hostsettings(ui, hostname):
"""Obtain security settings for a hostname.
Returns a dict of settings relevant to that hostname.
"""
s = {
# Whether we should attempt to load default/available CA certs
# if an explicit ``cafile`` is not defined.
'allowloaddefaultcerts': True,
# List of 2-tuple of (hash algorithm, hash).
'certfingerprints': [],
# Path to file containing concatenated CA certs. Used by
# SSLContext.load_verify_locations().
'cafile': None,
# Whether certificate verification should be disabled.
'disablecertverification': False,
# Whether the legacy [hostfingerprints] section has data for this host.
'legacyfingerprint': False,
# ssl.CERT_* constant used by SSLContext.verify_mode.
'verifymode': None,
}
# Look for fingerprints in [hostsecurity] section. Value is a list
# of <alg>:<fingerprint> strings.
fingerprints = ui.configlist('hostsecurity', '%s:fingerprints' % hostname,
[])
for fingerprint in fingerprints:
if not (fingerprint.startswith(('sha1:', 'sha256:', 'sha512:'))):
raise error.Abort(_('invalid fingerprint for %s: %s') % (
hostname, fingerprint),
hint=_('must begin with "sha1:", "sha256:", '
'or "sha512:"'))
alg, fingerprint = fingerprint.split(':', 1)
fingerprint = fingerprint.replace(':', '').lower()
s['certfingerprints'].append((alg, fingerprint))
# Fingerprints from [hostfingerprints] are always SHA-1.
for fingerprint in ui.configlist('hostfingerprints', hostname, []):
fingerprint = fingerprint.replace(':', '').lower()
s['certfingerprints'].append(('sha1', fingerprint))
s['legacyfingerprint'] = True
# If a host cert fingerprint is defined, it is the only thing that
# matters. No need to validate CA certs.
if s['certfingerprints']:
s['verifymode'] = ssl.CERT_NONE
# If --insecure is used, don't take CAs into consideration.
elif ui.insecureconnections:
s['disablecertverification'] = True
s['verifymode'] = ssl.CERT_NONE
if ui.configbool('devel', 'disableloaddefaultcerts'):
s['allowloaddefaultcerts'] = False
# Try to hook up CA certificate validation unless something above
# makes it not necessary.
if s['verifymode'] is None:
# Find global certificates file in config.
cafile = ui.config('web', 'cacerts')
if cafile:
cafile = util.expandpath(cafile)
if not os.path.exists(cafile):
raise error.Abort(_('could not find web.cacerts: %s') % cafile)
else:
# No global CA certs. See if we can load defaults.
cafile = _defaultcacerts()
if cafile:
ui.debug('using %s to enable OS X system CA\n' % cafile)
s['cafile'] = cafile
# Require certificate validation if CA certs are being loaded and
# verification hasn't been disabled above.
if cafile or (_canloaddefaultcerts and s['allowloaddefaultcerts']):
s['verifymode'] = ssl.CERT_REQUIRED
else:
# At this point we don't have a fingerprint, aren't being
# explicitly insecure, and can't load CA certs. Connecting
# at this point is insecure. But we do it for BC reasons.
# TODO abort here to make secure by default.
s['verifymode'] = ssl.CERT_NONE
assert s['verifymode'] is not None
return s
def wrapsocket(sock, keyfile, certfile, ui, serverhostname=None):
"""Add SSL/TLS to a socket.
This is a glorified wrapper for ``ssl.wrap_socket()``. It makes sane
choices based on what security options are available.
In addition to the arguments supported by ``ssl.wrap_socket``, we allow
the following additional arguments:
* serverhostname - The expected hostname of the remote server. If the
server (and client) support SNI, this tells the server which certificate
to use.
"""
if not serverhostname:
raise error.Abort('serverhostname argument is required')
settings = _hostsettings(ui, serverhostname)
# Despite its name, PROTOCOL_SSLv23 selects the highest protocol
# that both ends support, including TLS protocols. On legacy stacks,
# the highest it likely goes in TLS 1.0. On modern stacks, it can
# support TLS 1.2.
#
# The PROTOCOL_TLSv* constants select a specific TLS version
# only (as opposed to multiple versions). So the method for
# supporting multiple TLS versions is to use PROTOCOL_SSLv23 and
# disable protocols via SSLContext.options and OP_NO_* constants.
# However, SSLContext.options doesn't work unless we have the
# full/real SSLContext available to us.
#
# SSLv2 and SSLv3 are broken. We ban them outright.
if modernssl:
protocol = ssl.PROTOCOL_SSLv23
else:
protocol = ssl.PROTOCOL_TLSv1
# TODO use ssl.create_default_context() on modernssl.
sslcontext = SSLContext(protocol)
# This is a no-op on old Python.
sslcontext.options |= OP_NO_SSLv2 | OP_NO_SSLv3
# This still works on our fake SSLContext.
sslcontext.verify_mode = settings['verifymode']
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)
if settings['cafile'] is not None:
sslcontext.load_verify_locations(cafile=settings['cafile'])
caloaded = True
elif settings['allowloaddefaultcerts']:
# This is a no-op on old Python.
sslcontext.load_default_certs()
caloaded = True
else:
caloaded = False
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'))
sslsocket._hgstate = {
'caloaded': caloaded,
'hostname': serverhostname,
'settings': settings,
'ui': ui,
}
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 default CA certificates or None."""
if _plainapplepython():
dummycert = os.path.join(os.path.dirname(__file__), 'dummycert.pem')
if os.path.exists(dummycert):
return dummycert
return None
def validatesocket(sock):
"""Validate a socket meets security requiremnets.
The passed socket must have been created with ``wrapsocket()``.
"""
host = sock._hgstate['hostname']
ui = sock._hgstate['ui']
settings = sock._hgstate['settings']
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)
if settings['disablecertverification']:
# We don't print the certificate fingerprint because it shouldn't
# be necessary: if the user requested certificate verification be
# disabled, they presumably already saw a message about the inability
# to verify the certificate and this message would have printed the
# fingerprint. So printing the fingerprint here adds little to no
# value.
ui.warn(_('warning: connection security to %s is disabled per current '
'settings; communication is susceptible to eavesdropping '
'and tampering\n') % host)
return
# If a certificate fingerprint is pinned, use it and only it to
# validate the remote cert.
peerfingerprints = {
'sha1': util.sha1(peercert).hexdigest(),
'sha256': util.sha256(peercert).hexdigest(),
'sha512': util.sha512(peercert).hexdigest(),
}
def fmtfingerprint(s):
return ':'.join([s[x:x + 2] for x in range(0, len(s), 2)])
nicefingerprint = 'sha256:%s' % fmtfingerprint(peerfingerprints['sha256'])
if settings['certfingerprints']:
for hash, fingerprint in settings['certfingerprints']:
if peerfingerprints[hash].lower() == fingerprint:
ui.debug('%s certificate matched fingerprint %s:%s\n' %
(host, hash, fmtfingerprint(fingerprint)))
return
# Pinned fingerprint didn't match. This is a fatal error.
if settings['legacyfingerprint']:
section = 'hostfingerprint'
nice = fmtfingerprint(peerfingerprints['sha1'])
else:
section = 'hostsecurity'
nice = '%s:%s' % (hash, fmtfingerprint(peerfingerprints[hash]))
raise error.Abort(_('certificate for %s has unexpected '
'fingerprint %s') % (host, nice),
hint=_('check %s configuration') % section)
if not sock._hgstate['caloaded']:
ui.warn(_('warning: certificate for %s not verified '
'(set hostsecurity.%s:certfingerprints=%s or web.cacerts '
'config settings)\n') % (host, host, nicefingerprint))
return
msg = _verifycert(peercert2, host)
if msg:
raise error.Abort(_('%s certificate error: %s') % (host, msg),
hint=_('set hostsecurity.%s:certfingerprints=%s '
'config setting or use --insecure to connect '
'insecurely') %
(host, nicefingerprint))