Date: Thu, 14 Sep 2017 15:27:40 +1000
From: Anthony Towns <aj@erisian.com.au>
To: Bitcoin Protocol Discussion <bitcoin-dev@lists.linuxfoundation.org>
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Subject: Re: [bitcoin-dev] Responsible disclosure of bugs
Precedence: list

On Tue, Sep 12, 2017 at 09:10:18AM -0700, Simon Liu wrote:
> It would be a good starting point if the current policy could be
> clarified, so everyone is on the same page, and there is no confusion.

Collecting various commentary from here and reddit, I think current de
facto policy is something like:

 * Vulnerabilities should be reported via security@bitcoincore.org [0]

 * A critical issue (that can be exploited immediately or is already
   being exploited causing large harm) will be dealt with by:
     * a released patch ASAP
     * wide notification of the need to upgrade (or to disable affected
       systems)
     * minimal disclosure of the actual problem, to delay attacks
   [1] [2]

 * A non-critical vulnerability (because it is difficult or expensive to
   exploit) will be dealt with by:
     * patch and review undertaken in the ordinary flow of development
     * backport of a fix or workaround from master to the current
       released version [2]

 * Devs will attempt to ensure that publication of the fix does not
   reveal the nature of the vulnerability by providing the proposed fix
   to experienced devs who have not been informed of the vulnerability,
   telling them that it fixes a vulnerability, and asking them to identify
   the vulnerability. [2]

 * Devs may recommend other bitcoin implementations adopt vulnerability
   fixes prior to the fix being released and widely deployed, if they
   can do so without revealing the vulnerability; eg, if the fix has
   significant performance benefits that would justify its inclusion. [3]

 * Prior to a vulnerability becoming public, devs will generally recommend
   to friendly altcoin devs that they should catch up with fixes. But this
   is only after the fixes are widely deployed in the bitcoin network. [4]

 * Devs will generally not notify altcoin developers who have behaved
   in a hostile manner (eg, using vulnerabilities to attack others, or
   who violate embargoes). [5]

 * Bitcoin devs won't disclose vulnerability details until >80% of bitcoin
   nodes have deployed the fixes. Vulnerability discovers are encouraged
   and requested to follow the same policy. [1] [6]

Those seem like pretty good policies to me, for what it's worth.

I haven't seen anything that indicates bitcoin devs will *ever* encourage
public disclosure of vulnerabilities (as opposed to tolerating other
people publishing them [6]). So I'm guessing current de facto policy is
more along the lines of:

 * Where possible, Bitcoin devs will never disclose vulnerabilities
   publically while affected code may still be in use (including by
   altcoins).

rather than something like:

 * Bitcoin devs will disclose vulnerabilities publically after 99% of the
   bitcoin network has upgraded [7], and fixes have been released for
   at least 12 months.


Instinctively, I'd say documenting this policy (or whatever it actually
is) would be good, and having all vulnerabilities get publically released
eventually would also be good; that's certainly the more "open source"
approach. But arguing the other side:

 - documenting security policy gives attackers a better handle on where
   to find weak points; this may be more harm than there is benefit to
   improving legitimate users' understanding of and confidence in the
   development process

 - the main benefit of public vulnerability disclosure is a better
   working relationship with security researchers and perhaps better
   understanding of what sort of bugs happen in practice in general;
   but if most of your security research is effectively in house [6],
   maybe those benefits aren't as great as the harm done by revealing
   even old vulnerabilities to attackers

If the first of those arguments holds, well, hopefully this message has
egregious errors that no one will correct, or it will quickly get lost
in this list's archives...

Cheers,
aj

[0] http://bitcoincore.org/en/contact
    referenced from .github/ISSUE_TEMPLATE.md in git

[1] https://lists.linuxfoundation.org/pipermail/bitcoin-dev/2017-September/014986.html

[2] https://lists.linuxfoundation.org/pipermail/bitcoin-dev/2017-September/014990.html

[3] https://www.reddit.com/r/btc/comments/6zf1qo/peter_todd_nicely_pulled_away_attention_from_jjs/dmxcw70/

[4] https://www.reddit.com/r/btc/comments/6z827o/chris_jeffrey_jj_discloses_bitcoin_attack_vector/dmxdg83/

[5] https://www.reddit.com/r/btc/comments/6zb3lp/maxwell_admits_core_sat_on_vulnerability/dmv4y7g/

[6] https://lists.linuxfoundation.org/pipermail/bitcoin-dev/2017-September/014991.html 

[7] Per http://luke.dashjr.org/programs/bitcoin/files/charts/branches.html
    it seems like 1.7% of the network is running known-vulnerable versions
    0.8 and 0.9; but only 0.37% are running 0.10 or 0.11, so that might argue
    revealing any vulnerabilities fixed since 0.12.0 would be fine...
    (bitnodes.21.co doesn't seem to break down anything earlier than 0.12)