comparison mercurial/sslutil.py @ 52292:085cc409847d

sslutil: bump the default minimum TLS version of the client to 1.2 (BC)

TLS v1.0 and v1.1 are deprecated by RFC8996[1]:

   These versions lack support for current and recommended cryptographic
   algorithms and mechanisms, and various government and industry profiles of
   applications using TLS now mandate avoiding these old TLS versions.
   TLS version 1.2 became the recommended version for IETF protocols in
   2008 (subsequently being obsoleted by TLS version 1.3 in 2018)...

Various browsers have disabled or removed it[2][3][4], as have various internet
services, and Windows 11 has it disabled by default[5].  We should move on too.
(We should also bump it on the server side, as this config only affects clients
not allowing a server to negotiate down.  But the only server-side config is a
`devel` option to pick exactly one protocol version and is commented as a
footgun, so I'm hesitant to touch that.  See 7dec5e441bf7 for details, which
states that using `hg serve` directly isn't expected for a web service.)

I'm not knowledgeable enough in this area to know if we should follow up with
disabling certain ciphers too.  But this should provide better security on its
own.

[1] https://datatracker.ietf.org/doc/rfc8996/
[2] https://learn.microsoft.com/en-us/DeployEdge/microsoft-edge-policies#sslversionmin
[3] https://hacks.mozilla.org/2020/02/its-the-boot-for-tls-1-0-and-tls-1-1/
[4] https://security.googleblog.com/2018/10/modernizing-transport-security.html
[5] https://techcommunity.microsoft.com/blog/windows-itpro-blog/tls-1-0-and-tls-1-1-soon-to-be-disabled-in-windows/3887947

52291:b65085c6d6ff

                % (key, protocol),
                hint=_(b'valid protocols: %s')
                % b' '.join(sorted(configprotocols)),
            )

    # We default to TLS 1.1+ because TLS 1.0 has known vulnerabilities (like
    # BEAST and POODLE). We allow users to downgrade to TLS 1.0+ via config
    # options in case a legacy server is encountered.

    # setup.py checks that TLS 1.1 or TLS 1.2 is present, so the following
    # assert should not fail.
    assert supportedprotocols - {b'tls1.0'}
    defaultminimumprotocol = b'tls1.1'

    key = b'minimumprotocol'
    minimumprotocol = ui.config(b'hostsecurity', key, defaultminimumprotocol)
    validateprotocol(minimumprotocol, key)

52292:085cc409847d

                % (key, protocol),
                hint=_(b'valid protocols: %s')
                % b' '.join(sorted(configprotocols)),
            )

    # We default to TLS 1.2+ because TLS 1.0 has known vulnerabilities (like
    # BEAST and POODLE). We allow users to downgrade to TLS 1.0+ via config
    # options in case a legacy server is encountered.

    # setup.py checks that TLS 1.1 or TLS 1.2 is present, so the following
    # assert should not fail.
    assert supportedprotocols - {b'tls1.0', b'tls1.1'}
    defaultminimumprotocol = b'tls1.2'

    key = b'minimumprotocol'
    minimumprotocol = ui.config(b'hostsecurity', key, defaultminimumprotocol)
    validateprotocol(minimumprotocol, key)