view contrib/check-config.py @ 29560:303e9300772a

sslutil: require TLS 1.1+ when supported

Currently, Mercurial will use TLS 1.0 or newer when connecting to
remote servers, selecting the highest TLS version supported by both
peers. On older Pythons, only TLS 1.0 is available. On newer Pythons,
TLS 1.1 and 1.2 should be available.

Security professionals recommend avoiding TLS 1.0 if possible.
PCI DSS 3.1 "strongly encourages" the use of TLS 1.2.

Known attacks like BEAST and POODLE exist against TLS 1.0 (although
mitigations are available and properly configured servers aren't
vulnerable).

I asked Eric Rescorla - Mozilla's resident crypto expert - whether
Mercurial should drop support for TLS 1.0. His response was
"if you can get away with it." Essentially, a number of servers on
the Internet don't support TLS 1.1+. This is why web browsers
continue to support TLS 1.0 despite desires from security experts.

This patch changes Mercurial's default behavior on modern Python
versions to require TLS 1.1+, thus avoiding known security issues
with TLS 1.0 and making Mercurial more secure by default. Rather
than drop TLS 1.0 support wholesale, we still allow TLS 1.0 to be
used if configured. This is a compromise solution - ideally we'd
disallow TLS 1.0. However, since we're not sure how many Mercurial
servers don't support TLS 1.1+ and we're not sure how much user
inconvenience this change will bring, I think it is prudent to ship
an escape hatch that still allows usage of TLS 1.0. In the default
case our users get better security. In the worst case, they are no
worse off than before this patch.

This patch has no effect when running on Python versions that don't
support TLS 1.1+.

As the added test shows, connecting to a server that doesn't
support TLS 1.1+ will display a warning message with a link to
our wiki, where we can guide people to configure their client to
allow less secure connections.

#!/usr/bin/env python
#
# check-config - a config flag documentation checker for Mercurial
#
# Copyright 2015 Matt Mackall <[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.

from __future__ import absolute_import, print_function
import re
import sys

foundopts = {}
documented = {}

configre = (r"""ui\.config(|int|bool|list)\(['"](\S+)['"],\s*"""
            r"""['"](\S+)['"](,\s+(?:default=)?(\S+?))?\)""")
configpartialre = (r"""ui\.config""")

def main(args):
    for f in args:
        sect = ''
        prevname = ''
        confsect = ''
        carryover = ''
        for l in open(f):

            # check topic-like bits
            m = re.match('\s*``(\S+)``', l)
            if m:
                prevname = m.group(1)
            if re.match('^\s*-+$', l):
                sect = prevname
                prevname = ''

            if sect and prevname:
                name = sect + '.' + prevname
                documented[name] = 1

            # check docstring bits
            m = re.match(r'^\s+\[(\S+)\]', l)
            if m:
                confsect = m.group(1)
                continue
            m = re.match(r'^\s+(?:#\s*)?(\S+) = ', l)
            if m:
                name = confsect + '.' + m.group(1)
                documented[name] = 1

            # like the bugzilla extension
            m = re.match(r'^\s*(\S+\.\S+)$', l)
            if m:
                documented[m.group(1)] = 1

            # like convert
            m = re.match(r'^\s*:(\S+\.\S+):\s+', l)
            if m:
                documented[m.group(1)] = 1

            # quoted in help or docstrings
            m = re.match(r'.*?``(\S+\.\S+)``', l)
            if m:
                documented[m.group(1)] = 1

            # look for ignore markers
            m = re.search(r'# (?:internal|experimental|deprecated|developer)'
                          ' config: (\S+\.\S+)$', l)
            if m:
                documented[m.group(1)] = 1

            # look for code-like bits
            line = carryover + l
            m = re.search(configre, line, re.MULTILINE)
            if m:
                ctype = m.group(1)
                if not ctype:
                    ctype = 'str'
                name = m.group(2) + "." + m.group(3)
                default = m.group(5)
                if default in (None, 'False', 'None', '0', '[]', '""', "''"):
                    default = ''
                if re.match('[a-z.]+$', default):
                    default = '<variable>'
                if name in foundopts and (ctype, default) != foundopts[name]:
                    print(l)
                    print("conflict on %s: %r != %r" % (name, (ctype, default),
                                                        foundopts[name]))
                foundopts[name] = (ctype, default)
                carryover = ''
            else:
                m = re.search(configpartialre, line)
                if m:
                    carryover = line
                else:
                    carryover = ''

    for name in sorted(foundopts):
        if name not in documented:
            if not (name.startswith("devel.") or
                    name.startswith("experimental.") or
                    name.startswith("debug.")):
                ctype, default = foundopts[name]
                if default:
                    default = ' [%s]' % default
                print("undocumented: %s (%s)%s" % (name, ctype, default))

if __name__ == "__main__":
    if len(sys.argv) > 1:
        sys.exit(main(sys.argv[1:]))
    else:
        sys.exit(main([l.rstrip() for l in sys.stdin]))