view tests/test-ui-color.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.

from __future__ import absolute_import, print_function

import os
from hgext import (
    color,
)
from mercurial import (
    dispatch,
    ui as uimod,
)

# ensure errors aren't buffered
testui = color.colorui()
testui.pushbuffer()
testui.write(('buffered\n'))
testui.warn(('warning\n'))
testui.write_err('error\n')
print(repr(testui.popbuffer()))

# test dispatch.dispatch with the same ui object
hgrc = open(os.environ["HGRCPATH"], 'w')
hgrc.write('[extensions]\n')
hgrc.write('color=\n')
hgrc.close()

ui_ = uimod.ui()
ui_.setconfig('ui', 'formatted', 'True')

# we're not interested in the output, so write that to devnull
ui_.fout = open(os.devnull, 'w')

# call some arbitrary command just so we go through
# color's wrapped _runcommand twice.
def runcmd():
    dispatch.dispatch(dispatch.request(['version', '-q'], ui_))

runcmd()
print("colored? " + str(issubclass(ui_.__class__, color.colorui)))
runcmd()
print("colored? " + str(issubclass(ui_.__class__, color.colorui)))