Include Offer context in blinded payment paths
[rust-lightning] / lightning / src / offers / offer.rs
index ab7fe62cb50e073bbb67e21fb32071027dff9808..3dedc6cd35d25166263603fb58fb6173faeb8935 100644 (file)
@@ -79,7 +79,7 @@
 use bitcoin::blockdata::constants::ChainHash;
 use bitcoin::network::constants::Network;
 use bitcoin::secp256k1::{KeyPair, PublicKey, Secp256k1, self};
-use core::convert::TryFrom;
+use core::hash::{Hash, Hasher};
 use core::num::NonZeroU64;
 use core::ops::Deref;
 use core::str::FromStr;
@@ -90,14 +90,23 @@ use crate::blinded_path::BlindedPath;
 use crate::ln::channelmanager::PaymentId;
 use crate::ln::features::OfferFeatures;
 use crate::ln::inbound_payment::{ExpandedKey, IV_LEN, Nonce};
-use crate::ln::msgs::MAX_VALUE_MSAT;
-use crate::offers::invoice_request::{DerivedPayerId, ExplicitPayerId, InvoiceRequestBuilder};
-use crate::offers::merkle::TlvStream;
+use crate::ln::msgs::{DecodeError, MAX_VALUE_MSAT};
+use crate::offers::merkle::{TaggedHash, TlvStream};
 use crate::offers::parse::{Bech32Encode, Bolt12ParseError, Bolt12SemanticError, ParsedMessage};
 use crate::offers::signer::{Metadata, MetadataMaterial, self};
-use crate::util::ser::{HighZeroBytesDroppedBigSize, WithoutLength, Writeable, Writer};
+use crate::util::ser::{HighZeroBytesDroppedBigSize, Readable, WithoutLength, Writeable, Writer};
 use crate::util::string::PrintableString;
 
+#[cfg(not(c_bindings))]
+use {
+       crate::offers::invoice_request::{DerivedPayerId, ExplicitPayerId, InvoiceRequestBuilder},
+};
+#[cfg(c_bindings)]
+use {
+       crate::offers::invoice_request::{InvoiceRequestWithDerivedPayerIdBuilder, InvoiceRequestWithExplicitPayerIdBuilder},
+};
+
+#[allow(unused_imports)]
 use crate::prelude::*;
 
 #[cfg(feature = "std")]
@@ -105,6 +114,37 @@ use std::time::SystemTime;
 
 pub(super) const IV_BYTES: &[u8; IV_LEN] = b"LDK Offer ~~~~~~";
 
+/// An identifier for an [`Offer`] built using [`DerivedMetadata`].
+#[derive(Clone, Copy, Debug, Eq, PartialEq)]
+pub struct OfferId(pub [u8; 32]);
+
+impl OfferId {
+       const ID_TAG: &'static str = "LDK Offer ID";
+
+       fn from_valid_offer_tlv_stream(bytes: &[u8]) -> Self {
+               let tagged_hash = TaggedHash::from_valid_tlv_stream_bytes(Self::ID_TAG, bytes);
+               Self(tagged_hash.to_bytes())
+       }
+
+       fn from_valid_invreq_tlv_stream(bytes: &[u8]) -> Self {
+               let tlv_stream = TlvStream::new(bytes).range(OFFER_TYPES);
+               let tagged_hash = TaggedHash::from_tlv_stream(Self::ID_TAG, tlv_stream);
+               Self(tagged_hash.to_bytes())
+       }
+}
+
+impl Writeable for OfferId {
+       fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
+               self.0.write(w)
+       }
+}
+
+impl Readable for OfferId {
+       fn read<R: io::Read>(r: &mut R) -> Result<Self, DecodeError> {
+               Ok(OfferId(Readable::read(r)?))
+       }
+}
+
 /// Builds an [`Offer`] for the "offer to be paid" flow.
 ///
 /// See [module-level documentation] for usage.
@@ -118,6 +158,34 @@ pub struct OfferBuilder<'a, M: MetadataStrategy, T: secp256k1::Signing> {
        secp_ctx: Option<&'a Secp256k1<T>>,
 }
 
+/// Builds an [`Offer`] for the "offer to be paid" flow.
+///
+/// See [module-level documentation] for usage.
+///
+/// This is not exported to bindings users as builder patterns don't map outside of move semantics.
+///
+/// [module-level documentation]: self
+#[cfg(c_bindings)]
+pub struct OfferWithExplicitMetadataBuilder<'a> {
+       offer: OfferContents,
+       metadata_strategy: core::marker::PhantomData<ExplicitMetadata>,
+       secp_ctx: Option<&'a Secp256k1<secp256k1::All>>,
+}
+
+/// Builds an [`Offer`] for the "offer to be paid" flow.
+///
+/// See [module-level documentation] for usage.
+///
+/// This is not exported to bindings users as builder patterns don't map outside of move semantics.
+///
+/// [module-level documentation]: self
+#[cfg(c_bindings)]
+pub struct OfferWithDerivedMetadataBuilder<'a> {
+       offer: OfferContents,
+       metadata_strategy: core::marker::PhantomData<DerivedMetadata>,
+       secp_ctx: Option<&'a Secp256k1<secp256k1::All>>,
+}
+
 /// Indicates how [`Offer::metadata`] may be set.
 ///
 /// This is not exported to bindings users as builder patterns don't map outside of move semantics.
@@ -134,9 +202,12 @@ pub struct ExplicitMetadata {}
 pub struct DerivedMetadata {}
 
 impl MetadataStrategy for ExplicitMetadata {}
+
 impl MetadataStrategy for DerivedMetadata {}
 
-impl<'a> OfferBuilder<'a, ExplicitMetadata, secp256k1::SignOnly> {
+macro_rules! offer_explicit_metadata_builder_methods { (
+       $self: ident, $self_type: ty, $return_type: ty, $return_value: expr
+) => {
        /// Creates a new builder for an offer setting the [`Offer::description`] and using the
        /// [`Offer::signing_pubkey`] for signing invoices. The associated secret key must be remembered
        /// while the offer is valid.
@@ -151,7 +222,7 @@ impl<'a> OfferBuilder<'a, ExplicitMetadata, secp256k1::SignOnly> {
        /// [`ChannelManager`]: crate::ln::channelmanager::ChannelManager
        /// [`ChannelManager::create_offer_builder`]: crate::ln::channelmanager::ChannelManager::create_offer_builder
        pub fn new(description: String, signing_pubkey: PublicKey) -> Self {
-               OfferBuilder {
+               Self {
                        offer: OfferContents {
                                chains: None, metadata: None, amount: None, description,
                                features: OfferFeatures::empty(), absolute_expiry: None, issuer: None, paths: None,
@@ -165,13 +236,13 @@ impl<'a> OfferBuilder<'a, ExplicitMetadata, secp256k1::SignOnly> {
        /// Sets the [`Offer::metadata`] to the given bytes.
        ///
        /// Successive calls to this method will override the previous setting.
-       pub fn metadata(mut self, metadata: Vec<u8>) -> Result<Self, Bolt12SemanticError> {
-               self.offer.metadata = Some(Metadata::Bytes(metadata));
-               Ok(self)
+       pub fn metadata(mut $self: $self_type, metadata: Vec<u8>) -> Result<$return_type, Bolt12SemanticError> {
+               $self.offer.metadata = Some(Metadata::Bytes(metadata));
+               Ok($return_value)
        }
-}
+} }
 
-impl<'a, T: secp256k1::Signing> OfferBuilder<'a, DerivedMetadata, T> {
+macro_rules! offer_derived_metadata_builder_methods { ($secp_context: ty) => {
        /// Similar to [`OfferBuilder::new`] except, if [`OfferBuilder::path`] is called, the signing
        /// pubkey is derived from the given [`ExpandedKey`] and [`EntropySource`]. This provides
        /// recipient privacy by using a different signing pubkey for each offer. Otherwise, the
@@ -185,12 +256,12 @@ impl<'a, T: secp256k1::Signing> OfferBuilder<'a, DerivedMetadata, T> {
        /// [`ExpandedKey`]: crate::ln::inbound_payment::ExpandedKey
        pub fn deriving_signing_pubkey<ES: Deref>(
                description: String, node_id: PublicKey, expanded_key: &ExpandedKey, entropy_source: ES,
-               secp_ctx: &'a Secp256k1<T>
+               secp_ctx: &'a Secp256k1<$secp_context>
        ) -> Self where ES::Target: EntropySource {
                let nonce = Nonce::from_entropy_source(entropy_source);
                let derivation_material = MetadataMaterial::new(nonce, expanded_key, IV_BYTES, None);
                let metadata = Metadata::DerivedSigningPubkey(derivation_material);
-               OfferBuilder {
+               Self {
                        offer: OfferContents {
                                chains: None, metadata: Some(metadata), amount: None, description,
                                features: OfferFeatures::empty(), absolute_expiry: None, issuer: None, paths: None,
@@ -200,17 +271,19 @@ impl<'a, T: secp256k1::Signing> OfferBuilder<'a, DerivedMetadata, T> {
                        secp_ctx: Some(secp_ctx),
                }
        }
-}
+} }
 
-impl<'a, M: MetadataStrategy, T: secp256k1::Signing> OfferBuilder<'a, M, T> {
+macro_rules! offer_builder_methods { (
+       $self: ident, $self_type: ty, $return_type: ty, $return_value: expr $(, $self_mut: tt)?
+) => {
        /// Adds the chain hash of the given [`Network`] to [`Offer::chains`]. If not called,
        /// the chain hash of [`Network::Bitcoin`] is assumed to be the only one supported.
        ///
        /// See [`Offer::chains`] on how this relates to the payment currency.
        ///
        /// Successive calls to this method will add another chain hash.
-       pub fn chain(self, network: Network) -> Self {
-               self.chain_hash(ChainHash::using_genesis_block(network))
+       pub fn chain($self: $self_type, network: Network) -> $return_type {
+               $self.chain_hash(ChainHash::using_genesis_block(network))
        }
 
        /// Adds the [`ChainHash`] to [`Offer::chains`]. If not called, the chain hash of
@@ -219,45 +292,45 @@ impl<'a, M: MetadataStrategy, T: secp256k1::Signing> OfferBuilder<'a, M, T> {
        /// See [`Offer::chains`] on how this relates to the payment currency.
        ///
        /// Successive calls to this method will add another chain hash.
-       pub(crate) fn chain_hash(mut self, chain: ChainHash) -> Self {
-               let chains = self.offer.chains.get_or_insert_with(Vec::new);
+       pub(crate) fn chain_hash($($self_mut)* $self: $self_type, chain: ChainHash) -> $return_type {
+               let chains = $self.offer.chains.get_or_insert_with(Vec::new);
                if !chains.contains(&chain) {
                        chains.push(chain);
                }
 
-               self
+               $return_value
        }
 
        /// Sets the [`Offer::amount`] as an [`Amount::Bitcoin`].
        ///
        /// Successive calls to this method will override the previous setting.
-       pub fn amount_msats(self, amount_msats: u64) -> Self {
-               self.amount(Amount::Bitcoin { amount_msats })
+       pub fn amount_msats($self: $self_type, amount_msats: u64) -> $return_type {
+               $self.amount(Amount::Bitcoin { amount_msats })
        }
 
        /// Sets the [`Offer::amount`].
        ///
        /// Successive calls to this method will override the previous setting.
-       pub(super) fn amount(mut self, amount: Amount) -> Self {
-               self.offer.amount = Some(amount);
-               self
+       pub(super) fn amount($($self_mut)* $self: $self_type, amount: Amount) -> $return_type {
+               $self.offer.amount = Some(amount);
+               $return_value
        }
 
        /// Sets the [`Offer::absolute_expiry`] as seconds since the Unix epoch. Any expiry that has
        /// already passed is valid and can be checked for using [`Offer::is_expired`].
        ///
        /// Successive calls to this method will override the previous setting.
-       pub fn absolute_expiry(mut self, absolute_expiry: Duration) -> Self {
-               self.offer.absolute_expiry = Some(absolute_expiry);
-               self
+       pub fn absolute_expiry($($self_mut)* $self: $self_type, absolute_expiry: Duration) -> $return_type {
+               $self.offer.absolute_expiry = Some(absolute_expiry);
+               $return_value
        }
 
        /// Sets the [`Offer::issuer`].
        ///
        /// Successive calls to this method will override the previous setting.
-       pub fn issuer(mut self, issuer: String) -> Self {
-               self.offer.issuer = Some(issuer);
-               self
+       pub fn issuer($($self_mut)* $self: $self_type, issuer: String) -> $return_type {
+               $self.offer.issuer = Some(issuer);
+               $return_value
        }
 
        /// Adds a blinded path to [`Offer::paths`]. Must include at least one path if only connected by
@@ -265,23 +338,23 @@ impl<'a, M: MetadataStrategy, T: secp256k1::Signing> OfferBuilder<'a, M, T> {
        ///
        /// Successive calls to this method will add another blinded path. Caller is responsible for not
        /// adding duplicate paths.
-       pub fn path(mut self, path: BlindedPath) -> Self {
-               self.offer.paths.get_or_insert_with(Vec::new).push(path);
-               self
+       pub fn path($($self_mut)* $self: $self_type, path: BlindedPath) -> $return_type {
+               $self.offer.paths.get_or_insert_with(Vec::new).push(path);
+               $return_value
        }
 
        /// Sets the quantity of items for [`Offer::supported_quantity`]. If not called, defaults to
        /// [`Quantity::One`].
        ///
        /// Successive calls to this method will override the previous setting.
-       pub fn supported_quantity(mut self, quantity: Quantity) -> Self {
-               self.offer.supported_quantity = quantity;
-               self
+       pub fn supported_quantity($($self_mut)* $self: $self_type, quantity: Quantity) -> $return_type {
+               $self.offer.supported_quantity = quantity;
+               $return_value
        }
 
        /// Builds an [`Offer`] from the builder's settings.
-       pub fn build(mut self) -> Result<Offer, Bolt12SemanticError> {
-               match self.offer.amount {
+       pub fn build($($self_mut)* $self: $self_type) -> Result<Offer, Bolt12SemanticError> {
+               match $self.offer.amount {
                        Some(Amount::Bitcoin { amount_msats }) => {
                                if amount_msats > MAX_VALUE_MSAT {
                                        return Err(Bolt12SemanticError::InvalidAmount);
@@ -291,56 +364,142 @@ impl<'a, M: MetadataStrategy, T: secp256k1::Signing> OfferBuilder<'a, M, T> {
                        None => {},
                }
 
-               if let Some(chains) = &self.offer.chains {
-                       if chains.len() == 1 && chains[0] == self.offer.implied_chain() {
-                               self.offer.chains = None;
+               if let Some(chains) = &$self.offer.chains {
+                       if chains.len() == 1 && chains[0] == $self.offer.implied_chain() {
+                               $self.offer.chains = None;
                        }
                }
 
-               Ok(self.build_without_checks())
+               Ok($self.build_without_checks())
        }
 
-       fn build_without_checks(mut self) -> Offer {
+       fn build_without_checks($($self_mut)* $self: $self_type) -> Offer {
                // Create the metadata for stateless verification of an InvoiceRequest.
-               if let Some(mut metadata) = self.offer.metadata.take() {
+               if let Some(mut metadata) = $self.offer.metadata.take() {
                        if metadata.has_derivation_material() {
-                               if self.offer.paths.is_none() {
+                               if $self.offer.paths.is_none() {
                                        metadata = metadata.without_keys();
                                }
 
-                               let mut tlv_stream = self.offer.as_tlv_stream();
+                               let mut tlv_stream = $self.offer.as_tlv_stream();
                                debug_assert_eq!(tlv_stream.metadata, None);
                                tlv_stream.metadata = None;
                                if metadata.derives_recipient_keys() {
                                        tlv_stream.node_id = None;
                                }
 
-                               let (derived_metadata, keys) = metadata.derive_from(tlv_stream, self.secp_ctx);
+                               let (derived_metadata, keys) = metadata.derive_from(tlv_stream, $self.secp_ctx);
                                metadata = derived_metadata;
                                if let Some(keys) = keys {
-                                       self.offer.signing_pubkey = keys.public_key();
+                                       $self.offer.signing_pubkey = keys.public_key();
                                }
                        }
 
-                       self.offer.metadata = Some(metadata);
+                       $self.offer.metadata = Some(metadata);
                }
 
                let mut bytes = Vec::new();
-               self.offer.write(&mut bytes).unwrap();
+               $self.offer.write(&mut bytes).unwrap();
+
+               let id = OfferId::from_valid_offer_tlv_stream(&bytes);
 
-               Offer { bytes, contents: self.offer }
+               Offer {
+                       bytes,
+                       #[cfg(not(c_bindings))]
+                       contents: $self.offer,
+                       #[cfg(c_bindings)]
+                       contents: $self.offer.clone(),
+                       id,
+               }
        }
-}
+} }
 
 #[cfg(test)]
+macro_rules! offer_builder_test_methods { (
+       $self: ident, $self_type: ty, $return_type: ty, $return_value: expr $(, $self_mut: tt)?
+) => {
+       #[cfg_attr(c_bindings, allow(dead_code))]
+       fn features_unchecked($($self_mut)* $self: $self_type, features: OfferFeatures) -> $return_type {
+               $self.offer.features = features;
+               $return_value
+       }
+
+       #[cfg_attr(c_bindings, allow(dead_code))]
+       pub(crate) fn clear_chains($($self_mut)* $self: $self_type) -> $return_type {
+               $self.offer.chains = None;
+               $return_value
+       }
+
+       #[cfg_attr(c_bindings, allow(dead_code))]
+       pub(crate) fn clear_paths($($self_mut)* $self: $self_type) -> $return_type {
+               $self.offer.paths = None;
+               $return_value
+       }
+
+       #[cfg_attr(c_bindings, allow(dead_code))]
+       pub(super) fn build_unchecked($self: $self_type) -> Offer {
+               $self.build_without_checks()
+       }
+} }
+
 impl<'a, M: MetadataStrategy, T: secp256k1::Signing> OfferBuilder<'a, M, T> {
-       fn features_unchecked(mut self, features: OfferFeatures) -> Self {
-               self.offer.features = features;
-               self
+       offer_builder_methods!(self, Self, Self, self, mut);
+
+       #[cfg(test)]
+       offer_builder_test_methods!(self, Self, Self, self, mut);
+}
+
+impl<'a> OfferBuilder<'a, ExplicitMetadata, secp256k1::SignOnly> {
+       offer_explicit_metadata_builder_methods!(self, Self, Self, self);
+}
+
+impl<'a, T: secp256k1::Signing> OfferBuilder<'a, DerivedMetadata, T> {
+       offer_derived_metadata_builder_methods!(T);
+}
+
+#[cfg(all(c_bindings, not(test)))]
+impl<'a> OfferWithExplicitMetadataBuilder<'a> {
+       offer_explicit_metadata_builder_methods!(self, &mut Self, (), ());
+       offer_builder_methods!(self, &mut Self, (), ());
+}
+
+#[cfg(all(c_bindings, test))]
+impl<'a> OfferWithExplicitMetadataBuilder<'a> {
+       offer_explicit_metadata_builder_methods!(self, &mut Self, &mut Self, self);
+       offer_builder_methods!(self, &mut Self, &mut Self, self);
+       offer_builder_test_methods!(self, &mut Self, &mut Self, self);
+}
+
+#[cfg(all(c_bindings, not(test)))]
+impl<'a> OfferWithDerivedMetadataBuilder<'a> {
+       offer_derived_metadata_builder_methods!(secp256k1::All);
+       offer_builder_methods!(self, &mut Self, (), ());
+}
+
+#[cfg(all(c_bindings, test))]
+impl<'a> OfferWithDerivedMetadataBuilder<'a> {
+       offer_derived_metadata_builder_methods!(secp256k1::All);
+       offer_builder_methods!(self, &mut Self, &mut Self, self);
+       offer_builder_test_methods!(self, &mut Self, &mut Self, self);
+}
+
+#[cfg(c_bindings)]
+impl<'a> From<OfferBuilder<'a, DerivedMetadata, secp256k1::All>>
+for OfferWithDerivedMetadataBuilder<'a> {
+       fn from(builder: OfferBuilder<'a, DerivedMetadata, secp256k1::All>) -> Self {
+               let OfferBuilder { offer, metadata_strategy, secp_ctx } = builder;
+
+               Self { offer, metadata_strategy, secp_ctx }
        }
+}
 
-       pub(super) fn build_unchecked(self) -> Offer {
-               self.build_without_checks()
+#[cfg(c_bindings)]
+impl<'a> From<OfferWithDerivedMetadataBuilder<'a>>
+for OfferBuilder<'a, DerivedMetadata, secp256k1::All> {
+       fn from(builder: OfferWithDerivedMetadataBuilder<'a>) -> Self {
+               let OfferWithDerivedMetadataBuilder { offer, metadata_strategy, secp_ctx } = builder;
+
+               Self { offer, metadata_strategy, secp_ctx }
        }
 }
 
@@ -358,12 +517,12 @@ impl<'a, M: MetadataStrategy, T: secp256k1::Signing> OfferBuilder<'a, M, T> {
 /// [`InvoiceRequest`]: crate::offers::invoice_request::InvoiceRequest
 /// [`Bolt12Invoice`]: crate::offers::invoice::Bolt12Invoice
 #[derive(Clone, Debug)]
-#[cfg_attr(test, derive(PartialEq))]
 pub struct Offer {
        // The serialized offer. Needed when creating an `InvoiceRequest` if the offer contains unknown
        // fields.
        pub(super) bytes: Vec<u8>,
        pub(super) contents: OfferContents,
+       id: OfferId,
 }
 
 /// The contents of an [`Offer`], which may be shared with an [`InvoiceRequest`] or a
@@ -453,6 +612,11 @@ macro_rules! offer_accessors { ($self: ident, $contents: expr) => {
 impl Offer {
        offer_accessors!(self, self.contents);
 
+       /// Returns the id of the offer.
+       pub fn id(&self) -> OfferId {
+               self.id
+       }
+
        pub(super) fn implied_chain(&self) -> ChainHash {
                self.contents.implied_chain()
        }
@@ -484,7 +648,9 @@ impl Offer {
        pub fn expects_quantity(&self) -> bool {
                self.contents.expects_quantity()
        }
+}
 
+macro_rules! request_invoice_derived_payer_id { ($self: ident, $builder: ty) => {
        /// Similar to [`Offer::request_invoice`] except it:
        /// - derives the [`InvoiceRequest::payer_id`] such that a different key can be used for each
        ///   request,
@@ -496,50 +662,52 @@ impl Offer {
        ///
        /// Useful to protect the sender's privacy.
        ///
-       /// This is not exported to bindings users as builder patterns don't map outside of move semantics.
-       ///
        /// [`InvoiceRequest::payer_id`]: crate::offers::invoice_request::InvoiceRequest::payer_id
        /// [`InvoiceRequest::payer_metadata`]: crate::offers::invoice_request::InvoiceRequest::payer_metadata
        /// [`Bolt12Invoice::verify`]: crate::offers::invoice::Bolt12Invoice::verify
        /// [`ExpandedKey`]: crate::ln::inbound_payment::ExpandedKey
-       pub fn request_invoice_deriving_payer_id<'a, 'b, ES: Deref, T: secp256k1::Signing>(
-               &'a self, expanded_key: &ExpandedKey, entropy_source: ES, secp_ctx: &'b Secp256k1<T>,
+       pub fn request_invoice_deriving_payer_id<
+               'a, 'b, ES: Deref,
+               #[cfg(not(c_bindings))]
+               T: secp256k1::Signing
+       >(
+               &'a $self, expanded_key: &ExpandedKey, entropy_source: ES,
+               #[cfg(not(c_bindings))]
+               secp_ctx: &'b Secp256k1<T>,
+               #[cfg(c_bindings)]
+               secp_ctx: &'b Secp256k1<secp256k1::All>,
                payment_id: PaymentId
-       ) -> Result<InvoiceRequestBuilder<'a, 'b, DerivedPayerId, T>, Bolt12SemanticError>
+       ) -> Result<$builder, Bolt12SemanticError>
        where
                ES::Target: EntropySource,
        {
-               if self.offer_features().requires_unknown_bits() {
+               if $self.offer_features().requires_unknown_bits() {
                        return Err(Bolt12SemanticError::UnknownRequiredFeatures);
                }
 
-               Ok(InvoiceRequestBuilder::deriving_payer_id(
-                       self, expanded_key, entropy_source, secp_ctx, payment_id
-               ))
+               Ok(<$builder>::deriving_payer_id($self, expanded_key, entropy_source, secp_ctx, payment_id))
        }
+} }
 
+macro_rules! request_invoice_explicit_payer_id { ($self: ident, $builder: ty) => {
        /// Similar to [`Offer::request_invoice_deriving_payer_id`] except uses `payer_id` for the
        /// [`InvoiceRequest::payer_id`] instead of deriving a different key for each request.
        ///
        /// Useful for recurring payments using the same `payer_id` with different invoices.
        ///
-       /// This is not exported to bindings users as builder patterns don't map outside of move semantics.
-       ///
        /// [`InvoiceRequest::payer_id`]: crate::offers::invoice_request::InvoiceRequest::payer_id
        pub fn request_invoice_deriving_metadata<ES: Deref>(
-               &self, payer_id: PublicKey, expanded_key: &ExpandedKey, entropy_source: ES,
+               &$self, payer_id: PublicKey, expanded_key: &ExpandedKey, entropy_source: ES,
                payment_id: PaymentId
-       ) -> Result<InvoiceRequestBuilder<ExplicitPayerId, secp256k1::SignOnly>, Bolt12SemanticError>
+       ) -> Result<$builder, Bolt12SemanticError>
        where
                ES::Target: EntropySource,
        {
-               if self.offer_features().requires_unknown_bits() {
+               if $self.offer_features().requires_unknown_bits() {
                        return Err(Bolt12SemanticError::UnknownRequiredFeatures);
                }
 
-               Ok(InvoiceRequestBuilder::deriving_metadata(
-                       self, payer_id, expanded_key, entropy_source, payment_id
-               ))
+               Ok(<$builder>::deriving_metadata($self, payer_id, expanded_key, entropy_source, payment_id))
        }
 
        /// Creates an [`InvoiceRequestBuilder`] for the offer with the given `metadata` and `payer_id`,
@@ -554,20 +722,32 @@ impl Offer {
        ///
        /// Errors if the offer contains unknown required features.
        ///
-       /// This is not exported to bindings users as builder patterns don't map outside of move semantics.
-       ///
        /// [`InvoiceRequest`]: crate::offers::invoice_request::InvoiceRequest
        pub fn request_invoice(
-               &self, metadata: Vec<u8>, payer_id: PublicKey
-       ) -> Result<InvoiceRequestBuilder<ExplicitPayerId, secp256k1::SignOnly>, Bolt12SemanticError> {
-               if self.offer_features().requires_unknown_bits() {
+               &$self, metadata: Vec<u8>, payer_id: PublicKey
+       ) -> Result<$builder, Bolt12SemanticError> {
+               if $self.offer_features().requires_unknown_bits() {
                        return Err(Bolt12SemanticError::UnknownRequiredFeatures);
                }
 
-               Ok(InvoiceRequestBuilder::new(self, metadata, payer_id))
+               Ok(<$builder>::new($self, metadata, payer_id))
        }
+} }
 
-       #[cfg(test)]
+#[cfg(not(c_bindings))]
+impl Offer {
+       request_invoice_derived_payer_id!(self, InvoiceRequestBuilder<'a, 'b, DerivedPayerId, T>);
+       request_invoice_explicit_payer_id!(self, InvoiceRequestBuilder<ExplicitPayerId, secp256k1::SignOnly>);
+}
+
+#[cfg(c_bindings)]
+impl Offer {
+       request_invoice_derived_payer_id!(self, InvoiceRequestWithDerivedPayerIdBuilder<'a, 'b>);
+       request_invoice_explicit_payer_id!(self, InvoiceRequestWithExplicitPayerIdBuilder);
+}
+
+#[cfg(test)]
+impl Offer {
        pub(super) fn as_tlv_stream(&self) -> OfferTlvStreamRef {
                self.contents.as_tlv_stream()
        }
@@ -579,6 +759,20 @@ impl AsRef<[u8]> for Offer {
        }
 }
 
+impl PartialEq for Offer {
+       fn eq(&self, other: &Self) -> bool {
+               self.bytes.eq(&other.bytes)
+       }
+}
+
+impl Eq for Offer {}
+
+impl Hash for Offer {
+       fn hash<H: Hasher>(&self, state: &mut H) {
+               self.bytes.hash(state);
+       }
+}
+
 impl OfferContents {
        pub fn chains(&self) -> Vec<ChainHash> {
                self.chains.as_ref().cloned().unwrap_or_else(|| vec![self.implied_chain()])
@@ -699,7 +893,7 @@ impl OfferContents {
        /// Verifies that the offer metadata was produced from the offer in the TLV stream.
        pub(super) fn verify<T: secp256k1::Signing>(
                &self, bytes: &[u8], key: &ExpandedKey, secp_ctx: &Secp256k1<T>
-       ) -> Result<Option<KeyPair>, ()> {
+       ) -> Result<(OfferId, Option<KeyPair>), ()> {
                match self.metadata() {
                        Some(metadata) => {
                                let tlv_stream = TlvStream::new(bytes).range(OFFER_TYPES).filter(|record| {
@@ -711,9 +905,13 @@ impl OfferContents {
                                                _ => true,
                                        }
                                });
-                               signer::verify_recipient_metadata(
+                               let keys = signer::verify_recipient_metadata(
                                        metadata, key, IV_BYTES, self.signing_pubkey(), tlv_stream, secp_ctx
-                               )
+                               )?;
+
+                               let offer_id = OfferId::from_valid_invreq_tlv_stream(bytes);
+
+                               Ok((offer_id, keys))
                        },
                        None => Err(()),
                }
@@ -848,7 +1046,9 @@ impl TryFrom<Vec<u8>> for Offer {
                let offer = ParsedMessage::<OfferTlvStream>::try_from(bytes)?;
                let ParsedMessage { bytes, tlv_stream } = offer;
                let contents = OfferContents::try_from(tlv_stream)?;
-               Ok(Offer { bytes, contents })
+               let id = OfferId::from_valid_offer_tlv_stream(&bytes);
+
+               Ok(Offer { bytes, contents, id })
        }
 }
 
@@ -909,15 +1109,22 @@ impl core::fmt::Display for Offer {
 
 #[cfg(test)]
 mod tests {
-       use super::{Amount, Offer, OfferBuilder, OfferTlvStreamRef, Quantity};
+       use super::{Amount, Offer, OfferTlvStreamRef, Quantity};
+       #[cfg(not(c_bindings))]
+       use {
+               super::OfferBuilder,
+       };
+       #[cfg(c_bindings)]
+       use {
+               super::OfferWithExplicitMetadataBuilder as OfferBuilder,
+       };
 
        use bitcoin::blockdata::constants::ChainHash;
        use bitcoin::network::constants::Network;
        use bitcoin::secp256k1::Secp256k1;
-       use core::convert::TryFrom;
        use core::num::NonZeroU64;
        use core::time::Duration;
-       use crate::blinded_path::{BlindedHop, BlindedPath};
+       use crate::blinded_path::{BlindedHop, BlindedPath, IntroductionNode};
        use crate::sign::KeyMaterial;
        use crate::ln::features::OfferFeatures;
        use crate::ln::inbound_payment::ExpandedKey;
@@ -1038,6 +1245,8 @@ mod tests {
                let entropy = FixedEntropy {};
                let secp_ctx = Secp256k1::new();
 
+               #[cfg(c_bindings)]
+               use super::OfferWithDerivedMetadataBuilder as OfferBuilder;
                let offer = OfferBuilder
                        ::deriving_signing_pubkey(desc, node_id, &expanded_key, &entropy, &secp_ctx)
                        .amount_msats(1000)
@@ -1047,7 +1256,10 @@ mod tests {
                let invoice_request = offer.request_invoice(vec![1; 32], payer_pubkey()).unwrap()
                        .build().unwrap()
                        .sign(payer_sign).unwrap();
-               assert!(invoice_request.verify(&expanded_key, &secp_ctx).is_ok());
+               match invoice_request.verify(&expanded_key, &secp_ctx) {
+                       Ok(invoice_request) => assert_eq!(invoice_request.offer_id, offer.id()),
+                       Err(_) => panic!("unexpected error"),
+               }
 
                // Fails verification with altered offer field
                let mut tlv_stream = offer.as_tlv_stream();
@@ -1086,7 +1298,7 @@ mod tests {
                let secp_ctx = Secp256k1::new();
 
                let blinded_path = BlindedPath {
-                       introduction_node_id: pubkey(40),
+                       introduction_node: IntroductionNode::NodeId(pubkey(40)),
                        blinding_point: pubkey(41),
                        blinded_hops: vec![
                                BlindedHop { blinded_node_id: pubkey(42), encrypted_payload: vec![0; 43] },
@@ -1094,6 +1306,8 @@ mod tests {
                        ],
                };
 
+               #[cfg(c_bindings)]
+               use super::OfferWithDerivedMetadataBuilder as OfferBuilder;
                let offer = OfferBuilder
                        ::deriving_signing_pubkey(desc, node_id, &expanded_key, &entropy, &secp_ctx)
                        .amount_msats(1000)
@@ -1104,7 +1318,10 @@ mod tests {
                let invoice_request = offer.request_invoice(vec![1; 32], payer_pubkey()).unwrap()
                        .build().unwrap()
                        .sign(payer_sign).unwrap();
-               assert!(invoice_request.verify(&expanded_key, &secp_ctx).is_ok());
+               match invoice_request.verify(&expanded_key, &secp_ctx) {
+                       Ok(invoice_request) => assert_eq!(invoice_request.offer_id, offer.id()),
+                       Err(_) => panic!("unexpected error"),
+               }
 
                // Fails verification with altered offer field
                let mut tlv_stream = offer.as_tlv_stream();
@@ -1148,8 +1365,13 @@ mod tests {
                assert_eq!(tlv_stream.amount, Some(1000));
                assert_eq!(tlv_stream.currency, None);
 
+               #[cfg(not(c_bindings))]
                let builder = OfferBuilder::new("foo".into(), pubkey(42))
                        .amount(currency_amount.clone());
+               #[cfg(c_bindings)]
+               let mut builder = OfferBuilder::new("foo".into(), pubkey(42));
+               #[cfg(c_bindings)]
+               builder.amount(currency_amount.clone());
                let tlv_stream = builder.offer.as_tlv_stream();
                assert_eq!(builder.offer.amount, Some(currency_amount.clone()));
                assert_eq!(tlv_stream.amount, Some(10));
@@ -1225,7 +1447,7 @@ mod tests {
        fn builds_offer_with_paths() {
                let paths = vec![
                        BlindedPath {
-                               introduction_node_id: pubkey(40),
+                               introduction_node: IntroductionNode::NodeId(pubkey(40)),
                                blinding_point: pubkey(41),
                                blinded_hops: vec![
                                        BlindedHop { blinded_node_id: pubkey(43), encrypted_payload: vec![0; 43] },
@@ -1233,7 +1455,7 @@ mod tests {
                                ],
                        },
                        BlindedPath {
-                               introduction_node_id: pubkey(40),
+                               introduction_node: IntroductionNode::NodeId(pubkey(40)),
                                blinding_point: pubkey(41),
                                blinded_hops: vec![
                                        BlindedHop { blinded_node_id: pubkey(45), encrypted_payload: vec![0; 45] },
@@ -1415,7 +1637,7 @@ mod tests {
        fn parses_offer_with_paths() {
                let offer = OfferBuilder::new("foo".into(), pubkey(42))
                        .path(BlindedPath {
-                               introduction_node_id: pubkey(40),
+                               introduction_node: IntroductionNode::NodeId(pubkey(40)),
                                blinding_point: pubkey(41),
                                blinded_hops: vec![
                                        BlindedHop { blinded_node_id: pubkey(43), encrypted_payload: vec![0; 43] },
@@ -1423,7 +1645,7 @@ mod tests {
                                ],
                        })
                        .path(BlindedPath {
-                               introduction_node_id: pubkey(40),
+                               introduction_node: IntroductionNode::NodeId(pubkey(40)),
                                blinding_point: pubkey(41),
                                blinded_hops: vec![
                                        BlindedHop { blinded_node_id: pubkey(45), encrypted_payload: vec![0; 45] },