Static invoice encoding and parsing

Define an interface for BOLT 12 static invoice messages. The underlying
format consists of the original bytes and the parsed contents.

The bytes are later needed for serialization. This is because it must
mirror all the offer TLV records, including unknown ones, which aren't
represented in the contents.

Invoices may be created from an offer.

Author: valentinewallace

lightning/src/offers/mod.rs

@@ -24,5 +24,6 @@ pub mod parse;
 mod payer;
 pub mod refund;
 pub(crate) mod signer;
+pub mod static_invoice;
 #[cfg(test)]
 pub(crate) mod test_utils;

lightning/src/offers/static_invoice.rs

@@ -0,0 +1,327 @@
+// This file is Copyright its original authors, visible in version control
+// history.
+//
+// This file is licensed under the Apache License, Version 2.0 <LICENSE-APACHE
+// or http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your option.
+// You may not use this file except in accordance with one or both of these
+// licenses.
+
+//! Data structures and encoding for static BOLT 12 invoices.
+
+use crate::blinded_path::BlindedPath;
+use crate::io;
+use crate::ln::features::{Bolt12InvoiceFeatures, OfferFeatures};
+use crate::ln::msgs::DecodeError;
+use crate::offers::invoice::{
+	construct_payment_paths, filter_fallbacks, is_expired, BlindedPathIter, BlindedPayInfo,
+	BlindedPayInfoIter, FallbackAddress, SIGNATURE_TAG,
+};
+use crate::offers::invoice_macros::invoice_accessors_common;
+use crate::offers::merkle::{self, SignatureTlvStream, TaggedHash};
+use crate::offers::offer::{Amount, OfferContents, OfferTlvStream, Quantity};
+use crate::offers::parse::{Bolt12ParseError, Bolt12SemanticError, ParsedMessage};
+use crate::util::ser::{
+	HighZeroBytesDroppedBigSize, Iterable, SeekReadable, WithoutLength, Writeable, Writer,
+};
+use crate::util::string::PrintableString;
+use bitcoin::address::Address;
+use bitcoin::blockdata::constants::ChainHash;
+use bitcoin::secp256k1::schnorr::Signature;
+use bitcoin::secp256k1::PublicKey;
+use core::time::Duration;
+
+/// Static invoices default to expiring after 24 hours.
+const DEFAULT_RELATIVE_EXPIRY: Duration = Duration::from_secs(3600 * 24);
+
+/// A `StaticInvoice` is a reusable payment request corresponding to an [`Offer`].
+///
+/// A static invoice may be sent in response to an [`InvoiceRequest`] and includes all the
+/// information needed to pay the recipient. However, unlike [`Bolt12Invoice`]s, static invoices do
+/// not provide proof-of-payment. Therefore, [`Bolt12Invoice`]s should be preferred when the
+/// recipient is online to provide one.
+///
+/// [`Offer`]: crate::offers::offer::Offer
+/// [`InvoiceRequest`]: crate::offers::invoice_request::InvoiceRequest
+/// [`Bolt12Invoice`]: crate::offers::invoice::Bolt12Invoice
+pub struct StaticInvoice {
+	bytes: Vec<u8>,
+	contents: InvoiceContents,
+	signature: Signature,
+	tagged_hash: TaggedHash,
+}
+
+/// The contents of a [`StaticInvoice`] for responding to an [`Offer`].
+///
+/// [`Offer`]: crate::offers::offer::Offer
+struct InvoiceContents {
+	offer: OfferContents,
+	payment_paths: Vec<(BlindedPayInfo, BlindedPath)>,
+	created_at: Duration,
+	relative_expiry: Option<Duration>,
+	fallbacks: Option<Vec<FallbackAddress>>,
+	features: Bolt12InvoiceFeatures,
+	signing_pubkey: PublicKey,
+}
+
+macro_rules! invoice_accessors { ($self: ident, $contents: expr) => {
+	/// The chain that must be used when paying the invoice. [`StaticInvoice`]s currently can only be
+	/// created from offers that support a single chain.
+	pub fn chain(&$self) -> ChainHash {
+		$contents.chain()
+	}
+
+	/// Opaque bytes set by the originating [`Offer::metadata`].
+	///
+	/// [`Offer::metadata`]: crate::offers::offer::Offer::metadata
+	pub fn metadata(&$self) -> Option<&Vec<u8>> {
+		$contents.metadata()
+	}
+
+	/// The minimum amount required for a successful payment of a single item.
+	///
+	/// From [`Offer::amount`].
+	///
+	/// [`Offer::amount`]: crate::offers::offer::Offer::amount
+	pub fn amount(&$self) -> Option<Amount> {
+		$contents.amount()
+	}
+
+	/// Features pertaining to the originating [`Offer`], from [`Offer::offer_features`].
+	///
+	/// [`Offer`]: crate::offers::offer::Offer
+	/// [`Offer::offer_features`]: crate::offers::offer::Offer::offer_features
+	pub fn offer_features(&$self) -> &OfferFeatures {
+		$contents.offer_features()
+	}
+
+	/// A complete description of the purpose of the originating offer, from [`Offer::description`].
+	///
+	/// [`Offer::description`]: crate::offers::offer::Offer::description
+	pub fn description(&$self) -> Option<PrintableString> {
+		$contents.description()
+	}
+
+	/// Duration since the Unix epoch when an invoice should no longer be requested, from
+	/// [`Offer::absolute_expiry`].
+	///
+	/// [`Offer::absolute_expiry`]: crate::offers::offer::Offer::absolute_expiry
+	pub fn absolute_expiry(&$self) -> Option<Duration> {
+		$contents.absolute_expiry()
+	}
+
+	/// The issuer of the offer, from [`Offer::issuer`].
+	///
+	/// [`Offer::issuer`]: crate::offers::offer::Offer::issuer
+	pub fn issuer(&$self) -> Option<PrintableString> {
+		$contents.issuer()
+	}
+
+	/// Paths to the recipient originating from publicly reachable nodes, from [`Offer::paths`].
+	///
+	/// [`Offer::paths`]: crate::offers::offer::Offer::paths
+	pub fn message_paths(&$self) -> &[BlindedPath] {
+		$contents.message_paths()
+	}
+
+	/// The quantity of items supported, from [`Offer::supported_quantity`].
+	///
+	/// [`Offer::supported_quantity`]: crate::offers::offer::Offer::supported_quantity
+	pub fn supported_quantity(&$self) -> Quantity {
+		$contents.supported_quantity()
+	}
+} }
+
+impl StaticInvoice {
+	invoice_accessors_common!(self, self.contents, StaticInvoice);
+	invoice_accessors!(self, self.contents);
+
+	/// Signature of the invoice verified using [`StaticInvoice::signing_pubkey`].
+	pub fn signature(&self) -> Signature {
+		self.signature
+	}
+
+	/// Hash that was used for signing the invoice.
+	pub fn signable_hash(&self) -> [u8; 32] {
+		self.tagged_hash.as_digest().as_ref().clone()
+	}
+}
+
+impl InvoiceContents {
+	fn chain(&self) -> ChainHash {
+		debug_assert_eq!(self.offer.chains().len(), 1);
+		self.offer.chains().first().cloned().unwrap_or_else(|| self.offer.implied_chain())
+	}
+
+	fn metadata(&self) -> Option<&Vec<u8>> {
+		self.offer.metadata()
+	}
+
+	fn amount(&self) -> Option<Amount> {
+		self.offer.amount()
+	}
+
+	fn offer_features(&self) -> &OfferFeatures {
+		self.offer.features()
+	}
+
+	fn description(&self) -> Option<PrintableString> {
+		self.offer.description()
+	}
+
+	fn absolute_expiry(&self) -> Option<Duration> {
+		self.offer.absolute_expiry()
+	}
+
+	fn issuer(&self) -> Option<PrintableString> {
+		self.offer.issuer()
+	}
+
+	fn message_paths(&self) -> &[BlindedPath] {
+		self.offer.paths()
+	}
+
+	fn supported_quantity(&self) -> Quantity {
+		self.offer.supported_quantity()
+	}
+
+	fn payment_paths(&self) -> &[(BlindedPayInfo, BlindedPath)] {
+		&self.payment_paths[..]
+	}
+
+	fn created_at(&self) -> Duration {
+		self.created_at
+	}
+
+	fn relative_expiry(&self) -> Duration {
+		self.relative_expiry.unwrap_or(DEFAULT_RELATIVE_EXPIRY)
+	}
+
+	#[cfg(feature = "std")]
+	fn is_expired(&self) -> bool {
+		is_expired(self.created_at(), self.relative_expiry())
+	}
+
+	fn fallbacks(&self) -> Vec<Address> {
+		let chain =
+			self.offer.chains().first().cloned().unwrap_or_else(|| self.offer.implied_chain());
+		self.fallbacks
+			.as_ref()
+			.map(|fallbacks| filter_fallbacks(chain, fallbacks))
+			.unwrap_or_else(Vec::new)
+	}
+
+	fn features(&self) -> &Bolt12InvoiceFeatures {
+		&self.features
+	}
+
+	fn signing_pubkey(&self) -> PublicKey {
+		self.signing_pubkey
+	}
+}
+
+impl Writeable for StaticInvoice {
+	fn write<W: Writer>(&self, writer: &mut W) -> Result<(), io::Error> {
+		WithoutLength(&self.bytes).write(writer)
+	}
+}
+
+impl TryFrom<Vec<u8>> for StaticInvoice {
+	type Error = Bolt12ParseError;
+
+	fn try_from(bytes: Vec<u8>) -> Result<Self, Self::Error> {
+		let parsed_invoice = ParsedMessage::<FullInvoiceTlvStream>::try_from(bytes)?;
+		StaticInvoice::try_from(parsed_invoice)
+	}
+}
+
+tlv_stream!(InvoiceTlvStream, InvoiceTlvStreamRef, 160..240, {
+	(160, paths: (Vec<BlindedPath>, WithoutLength, Iterable<'a, BlindedPathIter<'a>, BlindedPath>)),
+	(162, blindedpay: (Vec<BlindedPayInfo>, WithoutLength, Iterable<'a, BlindedPayInfoIter<'a>, BlindedPayInfo>)),
+	(164, created_at: (u64, HighZeroBytesDroppedBigSize)),
+	(166, relative_expiry: (u32, HighZeroBytesDroppedBigSize)),
+	(172, fallbacks: (Vec<FallbackAddress>, WithoutLength)),
+	(174, features: (Bolt12InvoiceFeatures, WithoutLength)),
+	(176, node_id: PublicKey),
+});
+
+type FullInvoiceTlvStream = (OfferTlvStream, InvoiceTlvStream, SignatureTlvStream);
+
+impl SeekReadable for FullInvoiceTlvStream {
+	fn read<R: io::Read + io::Seek>(r: &mut R) -> Result<Self, DecodeError> {
+		let offer = SeekReadable::read(r)?;
+		let invoice = SeekReadable::read(r)?;
+		let signature = SeekReadable::read(r)?;
+
+		Ok((offer, invoice, signature))
+	}
+}
+
+impl TryFrom<ParsedMessage<FullInvoiceTlvStream>> for StaticInvoice {
+	type Error = Bolt12ParseError;
+
+	fn try_from(invoice: ParsedMessage<FullInvoiceTlvStream>) -> Result<Self, Self::Error> {
+		let ParsedMessage { bytes, tlv_stream } = invoice;
+		let (offer_tlv_stream, invoice_tlv_stream, SignatureTlvStream { signature }) = tlv_stream;
+		let contents = InvoiceContents::try_from((offer_tlv_stream, invoice_tlv_stream))?;
+
+		let signature = match signature {
+			None => {
+				return Err(Bolt12ParseError::InvalidSemantics(
+					Bolt12SemanticError::MissingSignature,
+				))
+			},
+			Some(signature) => signature,
+		};
+		let tagged_hash = TaggedHash::from_valid_tlv_stream_bytes(SIGNATURE_TAG, &bytes);
+		let pubkey = contents.signing_pubkey;
+		merkle::verify_signature(&signature, &tagged_hash, pubkey)?;
+
+		Ok(StaticInvoice { bytes, contents, signature, tagged_hash })
+	}
+}
+
+impl TryFrom<(OfferTlvStream, InvoiceTlvStream)> for InvoiceContents {
+	type Error = Bolt12SemanticError;
+
+	fn try_from(tlv_stream: (OfferTlvStream, InvoiceTlvStream)) -> Result<Self, Self::Error> {
+		let (
+			offer_tlv_stream,
+			InvoiceTlvStream {
+				paths,
+				blindedpay,
+				created_at,
+				relative_expiry,
+				fallbacks,
+				features,
+				node_id,
+			},
+		) = tlv_stream;
+
+		let payment_paths = construct_payment_paths(blindedpay, paths)?;
+
+		let created_at = match created_at {
+			None => return Err(Bolt12SemanticError::MissingCreationTime),
+			Some(timestamp) => Duration::from_secs(timestamp),
+		};
+
+		let relative_expiry = relative_expiry.map(Into::<u64>::into).map(Duration::from_secs);
+
+		let features = features.unwrap_or_else(Bolt12InvoiceFeatures::empty);
+
+		let signing_pubkey = match node_id {
+			None => return Err(Bolt12SemanticError::MissingSigningPubkey),
+			Some(node_id) => node_id,
+		};
+
+		Ok(InvoiceContents {
+			offer: OfferContents::try_from(offer_tlv_stream)?,
+			payment_paths,
+			created_at,
+			relative_expiry,
+			fallbacks,
+			features,
+			signing_pubkey,
+		})
+	}
+}