From info at AndySchroder.com Fri Nov 17 16:28:46 2023 From: info at AndySchroder.com (Andy Schroder) Date: Fri, 17 Nov 2023 11:28:46 -0500 Subject: [Lightning-dev] Lightning Address in a Bolt 12 world In-Reply-To: References: Message-ID: <409d3008-8d26-3cab-55b0-a8bfb42b6c63@AndySchroder.com> #Comments ## General - I agree that option 3 and 1 should be used. However, you say "clients (mobile wallets) would first make a DNS request corresponding to option 3, and if that fails, they would fallback to option 1. Domain owners would implement only one of those two options, depending on their DNS capabilities." . However, it seems to me like if we query for a specific user at the domain and it exists, use Option 3, but if it doesn't, then fall back to Option 1. So, they can actually implement both, depending on the user. - I would omit suggesting to use DoH from the spec. DoH seems a bit centralized to me and that's up to the client to decide what to do. DNS itself is a hierarchically distributed system, so there is redundancy built into it (which has its flaw at the root nameserver / ICANN level) and it seems to me like DoH is taking much of that distributed design away. It seems like if you are concerned about your ISP snooping your traffic, you should use a tunnel so that your traffic is obfuscated that way, that way things are done at the IP level and not way up at the HTTPS level. Are you resorting to DoH because many ISP block traffic for DNSSEC records traffic through their networks? Either way, how you query DNS seems like that should be left up to the client and not really part of the spec. - Is there a minimum path/offer expiry? Wondering if those might be way lower than the DNS record expiry? Seems like we want the expiry of the DNS record to be less than the path expiry because there will be some latency in propagating a record with a new blinded path or offer through an organization's redundant nameservers. Also, when you create the offer with an expiry and add it to the DNS record, that expiry is part of the offer data itself and relative to when it was *created*, but your local computer will have an expiry that starts at the time you *fetched* that DNS record. - Will we hit any DNS record length limits with the blinded path or offer that need to be considered? ## Option 1 I think you should also add an option for a type that allows different users to have different blinded paths. From a scalability perspective, one may not want to serve all users on the same node. Also, the user may use their own lightning node instead of the domain operators. | hostname | record type | value | TTL | |------------------------|-------------|---------------------|-------------| | bob._lnaddress.domain.com. | TXT | path: | path expiry | The statement "Note that Alice cannot verify that the offer she receives is really from Bob: she has to TOFU (trust on first use). But that's something we fundamentally cannot fix if the only information Alice has is `bob at domain.com`. However, Alice obtains a signed statement from Bob's LSP that attests that `bob at domain.com` is associated with the Bolt12 offer she receives. If she later discovers that this was invalid, she can publish that proof to show the world that Bob's LSP is malicious" - I think should be revised to not use "LSP". We don't necessarily know if it is an LSP or a self hosted domain and node. It could be an LSP, but maybe not. - I think we should say that we cannot verify the offer *if* Bob does not self host and uses an LSP. If Bob self hosts, we know it's from Bob if DNSSEC validates and the root nameservers and the tld nameservers are honest. - I think there should be a QR code format that accompanies this so that phone apps can easily validate the path (or for option 3 below the offer). ## Option 2 - Seems to be a bad idea to me. You are relying on certificate authorities to prove the ownership of a domain? The certificate authorities are not an authority on domain ownership. Also, it seems to me like certificate authorities are a major weak link because if *any* certificate authority in your local trust database becomes faulty, *all* certificates can no longer be trusted. - This approach seems *very* unscalable because it requires the announcements for all domains to be gossiped to everyone? I think that there needs to be a decentralized DNS that is created, but this seems to be headed in the wrong direction. We should be able to learn from some of the hierarchical features of legacy DNS and build a truly decentralized "root", which will be more efficient. ## Option 3 - "The statement "Note that Alice cannot verify that the offer she receives is really from Bob" can apply to this option too, right? Andy Schroder On 11/16/23 08:51, Bastien TEINTURIER wrote: > Good morning list, > > Most of you already know and love lightning addresses [1]. > I wanted to revisit that protocol, to see how we could improve it and > fix its privacy drawbacks, while preserving the nice UX improvements > that it brings. > > I have prepared a gist with three different designs that achieve those > goals [2]. I'm attaching the contents of that gist below. I'd like to > turn it into a bLIP once I collect enough feedback from the community. > > I don't think we should select and implement all three options. They > show that we have a large enough design space, but I think we should > aim for simplicity of implementation and deployment. My personal choice > would be to do options 1 and 3: clients (mobile wallets) would first > make a DNS request corresponding to option 3, and if that fails, they > would fallback to option 1. Domain owners would implement only one of > those two options, depending on their DNS capabilities. > > Curious to hear your thoughts! > > Many thanks to Rusty and Matt who reviewed early drafts of that gist. > > [1] https://lightningaddress.com/ > [2] https://gist.github.com/t-bast/78fd797a7da570d293a8663908d3339b > > # Lightning Address > > [Lightning Address](https://lightningaddress.com/) is a very popular protocol that brings UX improvements that users love. > We'd like to provide those UX benefits without its privacy and security drawbacks. > > ## Issues with the current lightning address protocol > > As described [here](https://github.com/andrerfneves/lightning-address/blob/master/README.md), the lightning address protocol requires payment senders to make an HTTP request to the recipient's domain owner. > This has some inconvenient side effects: > > 1. The payment sender reveals their IP address to the recipient's domain owner, who knows both the sender and the recipient. > 2. The domain owner can swap invoices to steal some of the payment. > 3. It introduces a dependency on DNS servers and the need for an HTTP stack on the sender side. > > We can do better and fix or mitigate some of these issues, without compromising on UX. > We need two somewhat distinct mechanisms: > > 1. A way to privately obtain the `node_id` associated with a given domain. > 2. A way to privately contact that domain to obtain the recipient's payment details. > > ## User story > > Alice wants to pay `bob at domain.com` without any other prior information. > She doesn't want to reveal: > > * her identity to Bob (payment sender privacy) > * her identity to the manager of `domain.com ` (payment sender privacy) > * the fact that she wants to pay `bob at domain.com` to her LSP (payment recipient privacy) > > ## Option 1: use DNS records to link domains to nodes > > A first proposal would be to use a DNS record to obtain the `node_id` associated with a given domain. > > ### Obtain a blinded path to the node associated with a domain > > Domain owners add a DNS `TXT` record for their domain containing a blinded path to their node. > They may include an empty path if they wish to directly reveal their `node_id`. > > | hostname | record type | value | TTL | > |------------------------|-------------|---------------------|-------------| > | _lnaddress.domain.com . | TXT | path: | path expiry | > > Alice can then make a DNS query to obtain that blinded path. > > ```text > Alice DNS server > | | > | dig TXT _lnaddress.domain.com | > |-------------------------------------------------------------------->| > | _lnaddress.domain.com . IN TXT "path:c3056fb73aa623..." | > |<--------------------------------------------------------------------| > ``` > > :question: What encoding should we use for the blinded path option? Bech32m with the `lnp` prefix? > > :warning: Alice should query that DNS record using [DoH](https://datatracker.ietf.org/doc/html/rfc8484) for privacy. > She should also query multiple DoH servers to protect from malicious ones. > > :warning: Alice should check the AD flag is correctly set (DNSSEC). > > ### Obtain a Bolt 12 offer from the recipient > > Now that Alice has a way to reach the node that owns Bob's domain, she needs to contact them to obtain a Bolt 12 offer from Bob. > We use an `onion_message` for that, which has the following benefits: > > * Alice doesn't reveal her identity (IP address or `node_id`) to Bob or Bob's domain > * Alice doesn't reveal Bob's identity (IP address or `node_id`) to her LSP > * Alice doesn't even need to know the IP address for Bob's domain's lightning node > > ```text > Alice Alice's LSP Bob's LSP Bob > | | | | > | onion_message | | | > |-------------------------------->| onion_message | | > | | get_offer_from =bob at domain.com | | > | |---------------------------------->| | > | | | wake_up | > | | |-------------------------------->| > | | | offer | > | | |<--------------------------------| > | | onion_message | | > | |<----------------------------------| | > | onion_message | | | > | bob's bolt12 offer | | | > | bob's LSP signature | | | > |<--------------------------------| | | > ``` > > Note that Alice cannot verify that the offer she receives is really from Bob: she has to TOFU (trust on first use). > But that's something we fundamentally cannot fix if the only information Alice has is `bob at domain.com`. > However, Alice obtains a signed statement from Bob's LSP that attests that `bob at domain.com` is associated with the Bolt12 offer she receives. > If she later discovers that this was invalid, she can publish that proof to show the world that Bob's LSP is malicious. > > Otherwise, since there needs to be some out-of-band communication where the recipient advertizes their lightning address (e.g. on social media), some kind of verification code could be attached (hash of the `node_id`?). > The sender's wallet could optionally add a manual verification step of that verification code. > This would only need to be done once, since Alice can then reuse the same offer to fetch new invoices. > > ### Advantages and drawbacks > > The main advantage of this proposal is that it is simple, inexpensive and relies on standard mechanisms. > Its drawback is that domain owners need to be able to publish DNS `TXT` records, but that is widely supported. > > ## Option 2: use `node_announcement` to link nodes to specific domains > > This proposal is only based on the lightning network, without any dependency on DNS or HTTP stacks (apart from certificate validation). > > ### Obtain the `node_id` associated with a domain > > We add fields to `node_announcement` to let nodes advertize which domains they own. > Those fields would typically contain a signature of the `node_id` using the private key for the corresponding domain TLS certificate, along with its certificate chain. > Alice can then simply sync `node_announcement`s that contain domain links with her LSP: > > ```text > Alice LSP > | | > | node_announcement(foobar.com ) | > |<-----------------------------------------------| > | node_announcement(domain.xyz ) | > |<-----------------------------------------------| > | node_announcement(ln.stuff) | > |<-----------------------------------------------| > | ... | > |<-----------------------------------------------| > ``` > > ### Obtain a Bolt 12 offer from the recipient > > This uses exactly the same onion message mechanism as the previous proposal. > > ### Advantages and drawbacks > > The main advantage of this proposal is that it relies entirely on lightning protocol messages. > Its drawback is that Alice needs to sync some `node_announcement`s to obtain the domain owner's `node_id`. > Alice also needs to validate the certificate chain, which is old school annoying crypto. > It also doesn't allow domain owners to keep their `node_id` private (which may be useful for small community-based nodes). > > ## Option 3: use DNS records to directly store Bolt 12 offers > > Another option would be to make domain owners create one DNS `TXT` record for each of their user, directly containing their Bolt 12 offer: > > | hostname | record type | value | TTL | > |----------------------------|-------------|---------------------|--------------| > | bob._lnaddress.domain.com . | TXT | lno1qqx2n6mw2fh2... | offer expiry | > > ```text > Alice DNS server > | | > | dig TXT bob._lnaddress.domain.com | > |-------------------------------------------------------------------->| > | bob._lnaddress.domain.com . IN TXT "lno1qqx2n6mw2fh2..." | > |<--------------------------------------------------------------------| > ``` > > :warning: Alice should query that DNS record using [DoH](https://datatracker.ietf.org/doc/html/rfc8484) for privacy. > She should also query multiple DoH servers to protect from malicious ones. > > :warning: Alice should check the AD flag is correctly set (DNSSEC). > > ### Advantages and drawbacks > > The main advantage of this proposal is that it is straightforward for the sender and doesn't require any addition to the lightning protocol. > > There are some drawbacks though, mostly for the domain owner, because they will need to create a lot of DNS records (one per user). > If they're using a cloud provider, there will be limitations in the number of records they are allowed to create. > They may not have programmatic access to perform that operation automatically (when a user creates their lightning address). > Cheers, > Bastien > > > _______________________________________________ > Lightning-dev mailing list > Lightning-dev at lists.linuxfoundation.org > https://lists.linuxfoundation.org/mailman/listinfo/lightning-dev -------------- next part -------------- An HTML attachment was scrubbed... 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