Re: [bitcoin-dev] Why the BIP-72 Payment Protocol URI Standard is Insecure Against MITM Attacks

From: Aymeric Vitte <vitteaymeric@gmail•com>
To: Tomas <tomas@tomasvdw•nl>,
	Bitcoin Protocol Discussion
	<bitcoin-dev@lists•linuxfoundation.org>
Subject: Re: [bitcoin-dev] Why the BIP-72 Payment Protocol URI Standard is Insecure Against MITM Attacks
Date: Fri, 29 Sep 2017 19:40:00 +0200	[thread overview]
Message-ID: <d0855fe8-03b2-4f71-9514-7c841396aaa8@gmail.com> (raw)
In-Reply-To: <1506690843.2339068.1122431744.5A801943@webmail.messagingengine.com>

Everybody knows that https is broken and insecure, and everybody knows
that it's still better than nothing

Just reacting here because there is worse: you are quoting Kraken, did
not check for Coinbase but Kraken is proxying all of its https traffic
via Cloudflare, including the API traffic

This is crazy but that's how things are, that's what everybody is doing,
that's what we have

The https principles are obsolete, the concept of certificates tied to a
domain is a complete stupidity, because there are no concept of domains
in bitcoin for example (and webrtc, Tor, bittorrent, p2p systems, etc)
and should evolve to something like certificates tied to an entityID
managed by something like a blockchain system, and not a stupid domain or CA

Therefore specifying things for bitcoin à la web is not a good idea,
browsers can do far better than standard/usual web, and the "like
everybody is doing" argument is not a valid one


Le 29/09/2017 à 15:14, Tomas via bitcoin-dev a écrit :
> On Fri, Sep 29, 2017, at 04:55, Peter Todd via bitcoin-dev wrote:
>> The BIP-70 payment protocol used via BIP-72 URI's is insecure, as payment
>> qr
>> codes don't cryptographically commit to the identity of the merchant,
>> which
>> means a MITM attacker can redirect the payment if they can obtain a SSL
>> cert
>> that the wallet accepts.
> By that reasoning, we also shouldn't go to https://coinbase.com or
> https://kraken.com to buy any bitcoins? As a MITM can redirect the site
> _if_ they obtain the coinbase or kraken certificate.
>
> Obviously, HTTPS is secured under the assumption that certificates are
> secure.  
>
> Using the payment protocol simply means paying to a secure endpoint (eg
> https://tomasvdw.nl/pay) instead of an address.
>
>>  That wallet is also likely using an off-the-shelf SSL library,
>> with
>> nothing other than an infrequently updated set of root certificates to
>> use to
>> verify the certificate; your browser has access to a whole host of better
>> technologies, such as HSTS pinning, certificate transparency, and
>> frequently
>> updated root certificate lists with proper revocation (see Symantec).
> So we should not use HTTPS for secure transfer because the
> implementation may not be good enough? This incorrectly conflates
> implementation with specification. There is nothing stopping a developer
> from using a proper implementation.
>
>> As an ad-hoc, unstandardized, extension Android Wallet for Bitcoin at
>> least
>> supports a h= parameter with a hash commitment to what the payment
>> request
>> should be, and will reject the MITM attacker if that hash doesn't match.
>> But
>> that's not actually in the standard itself, and as far as I can tell has
>> never
>> been made into a BIP.
> Currently it is widely used by merchants, but not yet for light clients
> _receiving_ money. If it becomes more wide spread,   it offers a range
> of advantages as  the bitcoin-address of the URI can and should be
> deprecated (made impossible with "h="). A payment address just becomes a
> secure endpoint.
>
> This means no more address reuse is possible. Also, it drops the need
> for mempool synchronization among non-miners, solely as a "notification"
> mechanism. In addition it means light clients know exactly when a
> transaction is coming in, so they can efficiently rely on client-side
> filtering a small set of blocks, improving their privacy.
>
> In my opinion, the payment protocol is key to scaling.
>
>> As-is BIP-72 is very dangerous and should be depreciated, with a new BIP
>> made
>> to replace it.
> Sorry, but maybe you  could explain better how secure communication over
> HTTPS is "very dangerous"? I think some websites would like to know :)
>
> Tomas van der Wansem
> bitcrust
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