[2/3]: Support Forwarding of Blinded Payments #8160

carlaKC · 2023-11-08T19:43:33Z

This PR is the second in a series to add the ability for LND to forward payments to blinded routes.

Reviewer Notes:

This PR does not signal the route blinding feature yet because it does not include error handling for blinded forwards, which is critical to receiver privacy so LND should not advertise the feature until it fully support it.
Itests can be squashed, they're broken into multiple commits to aid readability.

Replaces #7376
Fixes #7298

Roasbeef · 2024-01-18T16:14:37Z

Will this be the last in the series to support forwarding?

carlaKC · 2024-01-18T16:17:13Z

Will this be the last in the series to support forwarding?

One more (WIP) to add and test error handling - it's quite delicate so I want to separate it out.

coderabbitai · 2024-01-25T14:13:17Z

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carlaKC · 2024-03-22T17:53:58Z

Added a469087 disable route blinding so that this can merge independently of #8485 (which will re-enable it + advertise feature).

carlaKC · 2024-03-27T13:48:57Z

Rebase! Also re-confirmed interop testing here.

Roasbeef · 2024-03-28T22:13:19Z

Needs a rebase!

htlcswitch/hop/iterator.go

Roasbeef · 2024-03-28T23:28:26Z

htlcswitch/hop/iterator.go

+	// route forwarding. Payloads will simply be rejected as invalid if
+	// they contain blinding points, as our node does not want to forward
+	// them.
+	DisableBlindedFwd bool


Same comment about if we can lift this up to a higher layer. So we never even try to decrypt/decode something when we don't support it.

I think not yet in the scope of these PRs, but we should also have path finding logic to not attempt to include a node in our blinded path if they don't support it.

Eg: we don't even need to call MakeBlindingKit (just for it to reject the payload) if we don't support the feature.

but we should also have path finding logic to not attempt to include a node in our blinded path if they don't support it.

Def, I imagine that would be for blinded path creation? Filter by feature bit and then make a path seems to be the norm.

htlcswitch/hop/payload.go

itest/lnd_route_blinding_test.go

Co-authored-by: Calvin Zachman <calvin.zachman@protonmail.com>

carlaKC · 2024-04-02T20:21:23Z

Thanks for the review @Roasbeef, the suggested interface makes things much cleaner 🧹

Addressed some of your post-merge review of #8159 here (where relevant to the existing changes) and will follow with the rest either in #8485 or an independent followup.

Add an option to disable route blinding, failing back any HTLC with a blinding point set when we haven't got the feature enabled. Note that this commit only handles the case where we're chosen as the relaying node (where the blinding point is in update_add_htlc), we'll add handling for the introduction node case once we get to handling of blinded payloads).

This commit introduces a blinding kits which abstracts over the operations required to decrypt, deserialize and reconstruct forwarding data from an encrypted blob of data included for nodes in blinded routes.

When we have a HTLC that is part of a blinded route, we need to include the next ephemeral blinding point in UpdateAddHtlc for the next hop. The way that we handle the addition of this key is the same for introduction nodes and relaying nodes within the route.

To separate blinded route parsing from payload parsing, we need to return the parsed types map so that we can properly validate blinded data payloads against what we saw in the onion.

If we received a payload with a encrypted data point set, our forwarding information should be set from the information in our encrypted blob. This behavior is the same for introduction and relying nodes in a blinded route.

Reject any HTLCs that use us as an introduction point in a blinded route if we have disabled route blinding. We have to do this after we've processed the payload, because we only know we're an introduction point once we've processed the payload itself.

Note: the itest is broken up into multiple commits to make it more readable, they can be squashed post-review.

We don't support receiving blinded in this PR - just intercept and settle instead. The HTLC's arrival on the interceptor indicates that it was successfully forwarded on a blinded hop.

This commit turns off route blinding for the daemon while we're waiting on full handling for blinded errors. The feature remains on for itests so that tests covering blinding can run as usual.

Roasbeef

LGTM 🥕

Thanks for considering those late-ish review comments, we're super close, let's keep this momentum going!

carlaKC added the blinded paths label Nov 8, 2023

carlaKC mentioned this pull request Nov 8, 2023

multi: Forward Blinded Payments #7376

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carlaKC self-assigned this Nov 8, 2023

carlaKC force-pushed the 7298-2-forwardblindedroutes branch from b0f5ca8 to 2096b96 Compare November 8, 2023 20:48

saubyk added this to the v0.18.0 milestone Nov 9, 2023

carlaKC force-pushed the 7298-2-forwardblindedroutes branch from 2096b96 to 23df342 Compare January 25, 2024 14:13

carlaKC force-pushed the 7298-2-forwardblindedroutes branch from 23df342 to 0683a2e Compare February 14, 2024 14:14

carlaKC requested review from guggero, ProofOfKeags, Crypt-iQ, morehouse, ellemouton, Roasbeef and yyforyongyu as code owners February 14, 2024 14:14

carlaKC removed request for Roasbeef, guggero, ProofOfKeags, yyforyongyu, Crypt-iQ, morehouse and ellemouton February 14, 2024 14:25

carlaKC force-pushed the 7298-2-forwardblindedroutes branch 3 times, most recently from 1892855 to 5fe3bb5 Compare February 17, 2024 22:54

carlaKC requested a review from bitromortac as a code owner February 17, 2024 22:54

carlaKC changed the title ~~[2/n]: Support Forwarding of Blinded Payments~~ [2/3]: Support Forwarding of Blinded Payments Feb 17, 2024

carlaKC mentioned this pull request Feb 17, 2024

[3/3]: Blinded Route Error Handling #8485

Merged

carlaKC force-pushed the 7298-2-forwardblindedroutes branch from eb4b8d8 to 8ddafed Compare March 22, 2024 17:47

carlaKC force-pushed the 7298-2-forwardblindedroutes branch from 8ddafed to a5c3bb4 Compare March 27, 2024 13:47

carlaKC force-pushed the 7298-2-forwardblindedroutes branch from a5c3bb4 to 9c2efac Compare March 28, 2024 22:20

Roasbeef requested changes Mar 28, 2024

View reviewed changes

carlaKC and others added 2 commits April 2, 2024 15:44

multi: use some record for payment descriptor blinding point

7fd9c2a

hop: add function for calculating forwarding amount

019b8fa

Co-authored-by: Calvin Zachman <calvin.zachman@protonmail.com>

carlaKC force-pushed the 7298-2-forwardblindedroutes branch from 9c2efac to 59d817f Compare April 2, 2024 20:17

carlaKC requested a review from Roasbeef April 2, 2024 20:21

carlaKC added 14 commits April 3, 2024 08:35

htlcswitch: add blinding kit to handle encrypted data in blinded routes

03f6c5c

This commit introduces a blinding kits which abstracts over the operations required to decrypt, deserialize and reconstruct forwarding data from an encrypted blob of data included for nodes in blinded routes.

multi: validate contents in blinded data against payload

ca6d414

htlcswitch: add blinding point to sphinx iterator for decoding

1e6fae3

multi: return parsed types from payload

2029a06

To separate blinded route parsing from payload parsing, we need to return the parsed types map so that we can properly validate blinded data payloads against what we saw in the onion.

htlcswitch: set forwarding information from encrypted data

6d41037

If we received a payload with a encrypted data point set, our forwarding information should be set from the information in our encrypted blob. This behavior is the same for introduction and relying nodes in a blinded route.

lntest: add setup for blinded route forwarding itest

a72aaa3

Note: the itest is broken up into multiple commits to make it more readable, they can be squashed post-review.

lntest: add helper to create blinded route

58dda83

lntest: add route construction to blinded forwarding test

69e1162

lntest: dispatch and intercept payment to blinded route

0d9a184

We don't support receiving blinded in this PR - just intercept and settle instead. The HTLC's arrival on the interceptor indicates that it was successfully forwarded on a blinded hop.

lncfg: disable allowing blinded routes in daemon but not itests

6e5eead

This commit turns off route blinding for the daemon while we're waiting on full handling for blinded errors. The feature remains on for itests so that tests covering blinding can run as usual.

docs: release notes 18.0

2188dd9

carlaKC force-pushed the 7298-2-forwardblindedroutes branch from 59d817f to 2188dd9 Compare April 3, 2024 14:54

Roasbeef approved these changes Apr 3, 2024

View reviewed changes

Roasbeef merged commit 9bafcb2 into lightningnetwork:master Apr 3, 2024
25 of 27 checks passed

carlaKC mentioned this pull request Apr 12, 2024

Newsletters: add 297 (2024-04-10) bitcoinops/bitcoinops.github.io#1608

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[2/3]: Support Forwarding of Blinded Payments #8160

[2/3]: Support Forwarding of Blinded Payments #8160

carlaKC commented Nov 8, 2023 •

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[2/3]: Support Forwarding of Blinded Payments #8160

[2/3]: Support Forwarding of Blinded Payments #8160

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