Introduce Verification trait.

- The trait defines the public method one may define for creating and
  verifying the HMAC.
- Using a pub trait to define these method allows the flexibility for
  other `OffersMessageHandler` construct to construct the HMAC and
authenticate the message.

diff --git a/lightning/src/ln/channelmanager.rs b/lightning/src/ln/channelmanager.rs
index b14369c432a42273e168220c2f6617b339994bee..56457e79cba9f9418d9c95ace2fe36e9c33cbdde 100644 (file)
--- a/lightning/src/ln/channelmanager.rs
+++ b/lightning/src/ln/channelmanager.rs
@@ -409,6 +409,38 @@ impl From<&ClaimableHTLC> for events::ClaimedHTLC {
        }
 }
 
+/// A trait defining behavior for creating and verifing the HMAC for authenticating a given data.
+pub trait Verification {
+       /// Constructs an HMAC to include in [`OffersContext`] for the data along with the given
+       /// [`Nonce`].
+       fn hmac_for_offer_payment(
+               &self, nonce: Nonce, expanded_key: &inbound_payment::ExpandedKey,
+       ) -> Hmac<Sha256>;
+
+       /// Authenticates the data using an HMAC and a [`Nonce`] taken from an [`OffersContext`].
+       fn verify(
+               &self, hmac: Hmac<Sha256>, nonce: Nonce, expanded_key: &inbound_payment::ExpandedKey,
+       ) -> Result<(), ()>;
+}
+
+impl Verification for PaymentHash {
+       /// Constructs an HMAC to include in [`OffersContext::InboundPayment`] for the payment hash
+       /// along with the given [`Nonce`].
+       fn hmac_for_offer_payment(
+               &self, nonce: Nonce, expanded_key: &inbound_payment::ExpandedKey,
+       ) -> Hmac<Sha256> {
+               signer::hmac_for_payment_hash(*self, nonce, expanded_key)
+       }
+
+       /// Authenticates the payment id using an HMAC and a [`Nonce`] taken from an
+       /// [`OffersContext::InboundPayment`].
+       fn verify(
+               &self, hmac: Hmac<Sha256>, nonce: Nonce, expanded_key: &inbound_payment::ExpandedKey,
+       ) -> Result<(), ()> {
+               signer::verify_payment_hash(*self, hmac, nonce, expanded_key)
+       }
+}
+
 /// A user-provided identifier in [`ChannelManager::send_payment`] used to uniquely identify
 /// a payment and ensure idempotency in LDK.
 ///
@@ -419,10 +451,12 @@ pub struct PaymentId(pub [u8; Self::LENGTH]);
 impl PaymentId {
        /// Number of bytes in the id.
        pub const LENGTH: usize = 32;
+}
 
+impl Verification for PaymentId {
        /// Constructs an HMAC to include in [`OffersContext::OutboundPayment`] for the payment id
        /// along with the given [`Nonce`].
-       pub fn hmac_for_offer_payment(
+       fn hmac_for_offer_payment(
                &self, nonce: Nonce, expanded_key: &inbound_payment::ExpandedKey,
        ) -> Hmac<Sha256> {
                signer::hmac_for_payment_id(*self, nonce, expanded_key)
@@ -430,7 +464,7 @@ impl PaymentId {
 
        /// Authenticates the payment id using an HMAC and a [`Nonce`] taken from an
        /// [`OffersContext::OutboundPayment`].
-       pub fn verify(
+       fn verify(
                &self, hmac: Hmac<Sha256>, nonce: Nonce, expanded_key: &inbound_payment::ExpandedKey,
        ) -> Result<(), ()> {
                signer::verify_payment_id(*self, hmac, nonce, expanded_key)