From 5bee20e2375a8e0ef9dc9e229f5d1f6997901e46 Mon Sep 17 00:00:00 2001 From: Jeffrey Czyz Date: Wed, 14 Aug 2024 17:39:13 -0500 Subject: [PATCH] Add PaymentId authentication to public API When receiving an InvoiceError message, it should be authenticated before using it to abandon the payment. Add methods to PaymentId's public API for constructing and verifying an HMAC for use in OffersContext::OutboundPayment. This allows other implementations of OffersMessageHandler to construct the HMAC and authenticate the message. --- lightning/src/ln/channelmanager.rs | 21 +++++++++++++++++++-- 1 file changed, 19 insertions(+), 2 deletions(-) diff --git a/lightning/src/ln/channelmanager.rs b/lightning/src/ln/channelmanager.rs index 303c0d59e..316148b1c 100644 --- a/lightning/src/ln/channelmanager.rs +++ b/lightning/src/ln/channelmanager.rs @@ -24,6 +24,7 @@ use bitcoin::key::constants::SECRET_KEY_SIZE; use bitcoin::network::Network; use bitcoin::hashes::Hash; +use bitcoin::hashes::hmac::Hmac; use bitcoin::hashes::sha256::Hash as Sha256; use bitcoin::hash_types::{BlockHash, Txid}; @@ -413,6 +414,22 @@ pub struct PaymentId(pub [u8; Self::LENGTH]); impl PaymentId { /// Number of bytes in the id. pub const LENGTH: usize = 32; + + /// Constructs an HMAC to include in [`OffersContext::OutboundPayment`] for the payment id + /// along with the given [`Nonce`]. + pub fn hmac_for_offer_payment( + &self, nonce: Nonce, expanded_key: &inbound_payment::ExpandedKey, + ) -> Hmac { + signer::hmac_for_payment_id(*self, nonce, expanded_key) + } + + /// Authenticates the payment id using an HMAC and a [`Nonce`] taken from an + /// [`OffersContext::OutboundPayment`]. + pub fn verify( + &self, hmac: Hmac, nonce: Nonce, expanded_key: &inbound_payment::ExpandedKey, + ) -> Result<(), ()> { + signer::verify_payment_id(*self, hmac, nonce, expanded_key) + } } impl Writeable for PaymentId { @@ -9024,7 +9041,7 @@ where }; let invoice_request = builder.build_and_sign()?; - let hmac = signer::hmac_for_payment_id(payment_id, nonce, expanded_key); + let hmac = payment_id.hmac_for_offer_payment(nonce, expanded_key); let context = OffersContext::OutboundPayment { payment_id, nonce, hmac: Some(hmac) }; let reply_paths = self.create_blinded_paths(context) .map_err(|_| Bolt12SemanticError::MissingPaths)?; @@ -10900,7 +10917,7 @@ where match context { Some(OffersContext::OutboundPayment { payment_id, nonce, hmac: Some(hmac) }) => { - if let Ok(()) = signer::verify_payment_id(payment_id, hmac, nonce, expanded_key) { + if let Ok(()) = payment_id.verify(hmac, nonce, expanded_key) { self.abandon_payment_with_reason( payment_id, PaymentFailureReason::InvoiceRequestRejected, ); -- 2.39.5