Re: [bitcoin-dev] L2s Onchain Support IRC Workshop

[Gloria Zhao <gloriajzhao@gmail.com>]

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Hi Antoine,

Thanks for initiating this! I'm interested in joining. Since I mostly live
in L1, my primary goal is to understand what simplest version of package
relay would be sufficient to support transaction relay assumptions made by
L2 applications. For example, if a parent + child package covers the vast
majority of cases and a package limit of 2 is considered acceptable, that
could simplify things quite a bit.

A small note - I believe package relay and sponsorship (or other
fee-bumping primitive) should be separate discussions.

Re: L2-zoology... In general, for the purpose of creating a stable API /
set of assumptions between layers, I'd like to be as concrete as possible.
Speaking for myself, if I'm TDDing for a specific L2 attack, I need test
vectors. A simple description of mempool contents + p2p messages sent is
fine, but pubkeys + transaction hex would be appreciated because we don't
(and probably shouldn't, for the purpose of maintainability) have a lot of
tooling to build L2 transactions in Bitcoin Core. In the other direction,
it's hard to make any guarantees given the complexity of mempool policy,
but perhaps it could be helpful to expose a configurable RPC (e.g. #21413
<https://github.com/bitcoin/bitcoin/pull/21413>) to test a range of
scenarios?

Anyway, looking forward to discussions :)

Best,
Gloria

On Fri, Apr 23, 2021 at 8:51 AM Antoine Riard via bitcoin-dev <
bitcoin-dev@lists.linuxfoundation.org> wrote:

> Hi,
>
> During the lastest years, tx-relay and mempool acceptances rules of the
> base layer have been sources of major security and operational concerns for
> Lightning and other Bitcoin second-layers [0]. I think those areas require
> significant improvements to ease design and deployment of higher Bitcoin
> layers and I believe this opinion is shared among the L2 dev community. In
> order to make advancements, it has been discussed a few times in the last
> months to organize in-person workshops to discuss those issues with the
> presence of both L1/L2 devs to make exchange fruitful.
>
> Unfortunately, I don't think we'll be able to organize such in-person
> workshops this year (because you know travel is hard those days...) As a
> substitution, I'm proposing a series of one or more irc meetings. That
> said, this substitution has the happy benefit to gather far more folks
> interested by those issues that you can fit in a room.
>
> # Scope
>
> I would like to propose the following 4 items as topics of discussion.
>
> 1) Package relay design or another generic L2 fee-bumping primitive like
> sponsorship [0]. IMHO, this primitive should at least solve mempools spikes
> making obsolete propagation of transactions with pre-signed feerate, solve
> pinning attacks compromising Lightning/multi-party contract protocol
> safety, offer an usable and stable API to L2 software stack, stay
> compatible with miner and full-node operators incentives and obviously
> minimize CPU/memory DoS vectors.
>
> 2) Deprecation of opt-in RBF toward full-rbf. Opt-in RBF makes it trivial
> for an attacker to partition network mempools in divergent subsets and from
> then launch advanced security or privacy attacks against a Lightning node.
> Note, it might also be a concern for bandwidth bleeding attacks against L1
> nodes.
>
> 3) Guidelines about coordinated cross-layers security disclosures.
> Mitigating a security issue around tx-relay or the mempool in Core might
> have harmful implications for downstream projects. Ideally, L2 projects
> maintainers should be ready to upgrade their protocols in emergency in
> coordination with base layers developers.
>
> 4) Guidelines about L2 protocols onchain security design. Currently
> deployed like Lightning are making a bunch of assumptions on tx-relay and
> mempool acceptances rules. Those rules are non-normative, non-reliable and
> lack documentation. Further, they're devoid of tooling to enforce them at
> runtime [2]. IMHO, it could be preferable to identify a subset of them on
> which second-layers protocols can do assumptions without encroaching too
> much on nodes's policy realm or making the base layer development in those
> areas too cumbersome.
>
> I'm aware that some folks are interested in other topics such as extension
> of Core's mempools package limits or better pricing of RBF replacement. So
> l propose a 2-week concertation period to submit other topics related to
> tx-relay or mempools improvements towards L2s before to propose a finalized
> scope and agenda.
>
> # Goals
>
> 1) Reaching technical consensus.
> 2) Reaching technical consensus, before seeking community consensus as it
> likely has ecosystem-wide implications.
> 3) Establishing a security incident response policy which can be applied
> by dev teams in the future.
> 4) Establishing a philosophy design and associated documentations (BIPs,
> best practices, ...)
>
> # Timeline
>
> 2021-04-23: Start of concertation period
> 2021-05-07: End of concertation period
> 2021-05-10: Proposition of workshop agenda and schedule
> late 2021-05/2021-06: IRC meetings
>
> As the problem space is savagely wide, I've started a collection of
> documents to assist this workshop : https://github.com/ariard/L2-zoology
> Still wip, but I'll have them in a good shape at agenda publication, with
> reading suggestions and open questions to structure discussions.
> Also working on transaction pinning and mempool partitions attacks
> simulations.
>
> If L2s security/p2p/mempool is your jam, feel free to get involved :)
>
> Cheers,
> Antoine
>
> [0] For e.g see optech section on transaction pinning attacks :
> https://bitcoinops.org/en/topics/transaction-pinning/
> [1]
> https://lists.linuxfoundation.org/pipermail/bitcoin-dev/2020-September/018168.html
> [2] Lack of reference tooling make it easier to have bug slip in like
> https://lists.linuxfoundation.org/pipermail/lightning-dev/2020-October/002858.html
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