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Don't panic when a composite sub-handler returns Ok(None)#4709

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TheBlueMatt merged 1 commit into
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jkczyz:2026-06-composite-handler-ok-none
Jun 17, 2026
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Don't panic when a composite sub-handler returns Ok(None)#4709
TheBlueMatt merged 1 commit into
lightningdevkit:mainfrom
jkczyz:2026-06-composite-handler-ok-none

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@jkczyz

@jkczyz jkczyz commented Jun 17, 2026

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A handler built with composite_custom_message_handler! routes an incoming message type to the sub-handler whose pattern matches it and assumed the sub-handler would always decode it. But per the CustomMessageReader contract a sub-handler returns Ok(None) for a type it doesn't recognize, and a sub-handler's pattern -- a range in particular -- can be broader than the types it actually decodes.

Since the message type comes from peer input, this let a remote peer panic the message-processing thread with a single custom message whose type falls in a sub-handler's pattern but isn't decoded by it. Report such a message as unknown instead, matching how wire::do_read handles an undecoded custom message.

A handler built with `composite_custom_message_handler!` routes an incoming
message type to the sub-handler whose pattern matches it and assumed the
sub-handler would always decode it. But per the `CustomMessageReader`
contract a sub-handler returns `Ok(None)` for a type it doesn't recognize,
and a sub-handler's pattern -- a range in particular -- can be broader than
the types it actually decodes.

Since the message type comes from peer input, this let a remote peer panic
the message-processing thread with a single custom message whose type falls
in a sub-handler's pattern but isn't decoded by it. Report such a message as
unknown instead, matching how `wire::do_read` handles an undecoded custom
message.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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👋 Thanks for assigning @TheBlueMatt as a reviewer!
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Once they submit their review, I'll check if a second reviewer would be helpful.

@jkczyz jkczyz requested a review from TheBlueMatt June 17, 2026 19:49
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The change is correct and consistent with wire::do_read at lightning/src/ln/wire.rs:426-431, which treats a custom reader's Ok(None) as Message::Unknown. The fix properly removes the peer-triggerable panic, and the added test covers both the decoded and undecoded-in-range cases.

No issues found.

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might as well backport

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@TheBlueMatt TheBlueMatt merged commit 31bb3de into lightningdevkit:main Jun 17, 2026
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Backported to 0.2 in #4706

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Backported to 0.1 in #4710

TheBlueMatt added a commit that referenced this pull request Jun 19, 2026
v0.1.10 - Jun 18, 2026 - "Loupe de Loupe"

API Updates
===========

 * `DefaultMessageRouter` will now always generate blinded message paths that
   provide no privacy (where our node is the introduction node) for nodes with
   public channels. This works around an issue which will appear for any nodes
   with LND peers that enable onion messaging - such peers will refuse to
   forward BOLT 12 messages from unknown third parties, which most BOLT 12
   payers rely on today (#4647).
 * Explicit `amount_msats` of 0 is rejected in BOLT 12 `Offer`s; `OfferBuilder`
   now maps 0-amounts to an amount of `None` (#4324).

Bug Fixes
=========

 * Async `ChannelMonitorUpdate` persistence operations which complete, but are
   not marked as complete in a persisted `ChannelManager` prior to restart,
   followed immediately by a block connection and then another restart could
   result in some channel operations hanging leading for force-closures (#4377).
 * If an MPP payment is claimed but `ChannelMonitorUpdate`s for some parts are
   still being completed asynchronously, further channel updates (e.g.
   forwarding another payment) are pending and the node restarts, the channel
   could have become stuck (#4520).
 * The presence of unconfirmed transactions actually no longer causes
   `ElectrumSyncClient` to spuriously fail to sync (#4590).
 * `FilesystemStore::list_all_keys` will no longer fail if there are stale
   intermediate files lying around from a previous unclean shutdown (#4618).
 * When forwarding an HTLC while in a blinded path with proportional fees over
   200%, LDK will no longer spuriously allow a forward that pays us 1 msat too
   little in fees (#4697).
 * Fixed a rare case where a channel could get stuck on reconnect when using
   both async `ChannelMonitorUpdate` persistence and async signing (#4684).
 * `Event::PaymentSent::fee_paid_msat` is no longer `None` in cases where
   `ChannelManager::abandon_payment` was called before the payment ultimately
   completes anyway (#4651).
 * Syncing a `ChainMonitor` using the `Confirm` trait will no longer write some
   full `ChannelMonitor`s to disk several times per block (#4544).
 * `OMDomainResolver` now correctly accounts for failed queries when rate
   limiting, ensuring we continue to respond to queries after failures (#4591).
 * Calling `ChannelManager::send_payment_with_route` without a `route_params`
   and with an invalid `Route` will no longer panic (#4707).
 * `lightning-custom-message`'s handling of `peer_connected` events now ensures
   that sub-handlers will see a `peer_disconnected` event if a different
   sub-handler refused the connection by `Err`ing `peer_connected` (#4595).
 * Incomplete MPP keysend payments will no longer see their HTLCs held until
   expiry (#4558).
 * `InvoiceRequestBuilder` will no longer accept a `quantity` of `0` for a
   BOLT 12 `Offer`, allowing any quantity up to a bound (#4667).
 * `lightning-custom-message` handlers that return `Ok(None)` when asked to
   deserialize a message in their defined range no longer cause panics (#4709).
 * Several spurious debug assertions were fixed (#4537, #4618).

Security
========

0.1.10 fixes a sanitization issue and several denial-of-service vulnerabilities.
 * `Bolt11Invoice::recover_payee_pub_key` no longer panics if called on an
   invoice which set an explicit public key, rather than relying on public key
   recovery. This method is called from `payment_parameters_from_invoice` and
   `payment_parameters_from_variable_amount_invoice` (#4717).
 * Maliciously-crafted unpayable invoices which have overflowing feerates will
   no longer cause an `unwrap` failure panic (#4716).
 * `possiblyrandom` did not properly generate random data except when it was
   explicitly configured to. By default this means LDK is vulnerable to various
   HashDoS attacks (#4719).
 * `OMNameResolver` will no longer panic when looking up payment instructions
   which include unicode characters at the start of a TXT record (#4718).
 * `PrintableString` did not properly sanitize unicode format characters,
   allowing an attacker to corrupt the rendering of logs or UI (#4593, #4605).
 * RGS data is now limited in how large of a graph it is able to cause a client
   to store in memory. Note that RGS data is still considered a DoS vector in
   general and you should only use semi-trusted RGS data (#4713).
 * Counterparty-provided strings in failure messages are no longer logged in
   full, reducing the ability of such a counterparty to spam our logs (#4714).
 * Reading a corrupted `ChannelManager` or `ProbabilisticScorer` can no longer
   cause us to allocate large amounts of memory (#4712).

Thanks to Project Loupe for reporting most of the issues fixed in this release.
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4 participants