Move Payment{Hash,Preimage,Secret} into a new crate

`lightning-invoice` currently has a dependency on the entire
`lightning` crate just because it wants to use some of the useful
types from it. This is obviously backwards and leads to some
awkwardness like the BOLT 11 invoice signing API in the `lightning`
crate taking a `[u5]` rather than a `Bolt11Invoice`.

This is the first step towards fixing that - moving the common
types we need into a new `lightning-types` crate which both can
depend on.

Since we're using a new crate and can't depend on the existing
`lightning` hex utility to implement `Display`, we also take this
opportunity to switch to the new `Display` impl macro in
`hex_conservative`.

Author: TheBlueMatt

Cargo.toml

@@ -3,6 +3,7 @@ resolver = "2"
 
 members = [
     "lightning",
+    "lightning-types",
     "lightning-block-sync",
     "lightning-invoice",
     "lightning-net-tokio",

fuzz/src/chanmon_consistency.rs

@@ -56,7 +56,7 @@ use lightning::ln::msgs::{
 	self, ChannelMessageHandler, CommitmentUpdate, DecodeError, Init, UpdateAddHTLC,
 };
 use lightning::ln::script::ShutdownScript;
-use lightning::ln::{ChannelId, PaymentHash, PaymentPreimage, PaymentSecret};
+use lightning::ln::types::{ChannelId, PaymentHash, PaymentPreimage, PaymentSecret};
 use lightning::offers::invoice::{BlindedPayInfo, UnsignedBolt12Invoice};
 use lightning::offers::invoice_request::UnsignedInvoiceRequest;
 use lightning::onion_message::messenger::{Destination, MessageRouter, OnionMessagePath};

fuzz/src/full_stack.rs

@@ -49,7 +49,7 @@ use lightning::ln::peer_handler::{
 	IgnoringMessageHandler, MessageHandler, PeerManager, SocketDescriptor,
 };
 use lightning::ln::script::ShutdownScript;
-use lightning::ln::{ChannelId, PaymentHash, PaymentPreimage, PaymentSecret};
+use lightning::ln::types::{ChannelId, PaymentHash, PaymentPreimage, PaymentSecret};
 use lightning::offers::invoice::{BlindedPayInfo, UnsignedBolt12Invoice};
 use lightning::offers::invoice_request::UnsignedInvoiceRequest;
 use lightning::onion_message::messenger::{Destination, MessageRouter, OnionMessagePath};

fuzz/src/router.rs

@@ -18,7 +18,7 @@ use lightning::ln::channel_state::{ChannelCounterparty, ChannelDetails, ChannelS
 use lightning::ln::channelmanager;
 use lightning::ln::features::{BlindedHopFeatures, Bolt12InvoiceFeatures};
 use lightning::ln::msgs;
-use lightning::ln::ChannelId;
+use lightning::ln::types::ChannelId;
 use lightning::offers::invoice::BlindedPayInfo;
 use lightning::routing::gossip::{NetworkGraph, RoutingFees};
 use lightning::routing::router::{

lightning-types/Cargo.toml

@@ -0,0 +1,24 @@
+[package]
+name = "lightning-types"
+version = "0.1.0"
+authors = ["Matt Corallo"]
+license = "MIT OR Apache-2.0"
+repository = "https://github.com/lightningdevkit/rust-lightning/"
+description = """
+Basic types which are used in the lightning network
+"""
+edition = "2021"
+
+[package.metadata.docs.rs]
+rustdoc-args = ["--cfg", "docsrs"]
+
+[features]
+
+[dependencies]
+bitcoin = { version = "0.31", default-features = false }
+# TODO: Once we switch to bitcoin 0.32 drop this explicit dep:
+hex-conservative = { version = "0.2", default-features = false }
+bech32 = { version = "0.9", default-features = false }
+
+[lints]
+workspace = true

lightning-types/src/lib.rs

@@ -0,0 +1,26 @@
+// 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.
+
+#![crate_name = "lightning_types"]
+
+//! Various types which are used in the lightning network.
+//!
+//! See the `lightning` crate for usage of these.
+
+#![cfg_attr(not(test), no_std)]
+#![deny(missing_docs)]
+#![forbid(unsafe_code)]
+#![deny(rustdoc::broken_intra_doc_links)]
+#![deny(rustdoc::private_intra_doc_links)]
+#![cfg_attr(docsrs, feature(doc_auto_cfg))]
+
+extern crate alloc;
+extern crate core;
+
+pub mod payment;

lightning-types/src/payment.rs

@@ -0,0 +1,115 @@
+// 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.
+
+//! Types which describe payments in lightning.
+
+use alloc::vec::Vec;
+
+use core::borrow::Borrow;
+
+use bitcoin::hashes::{
+	Hash as _,
+	sha256::Hash as Sha256,
+};
+
+// TODO: Once we switch to rust-bitcoin 0.32, import this as bitcoin::hex
+use hex_conservative::display::impl_fmt_traits;
+
+/// The payment hash is the hash of the [`PaymentPreimage`] which is the value used to lock funds
+/// in HTLCs while they transit the lightning network.
+///
+/// This is not exported to bindings users as we just use [u8; 32] directly
+#[derive(Hash, Copy, Clone, PartialEq, Eq, Ord, PartialOrd)]
+pub struct PaymentHash(pub [u8; 32]);
+
+impl Borrow<[u8]> for PaymentHash {
+	fn borrow(&self) -> &[u8] {
+		&self.0[..]
+	}
+}
+
+impl_fmt_traits! {
+	impl fmt_traits for PaymentHash {
+		const LENGTH: usize = 32;
+	}
+}
+
+/// The payment preimage is the "secret key" which is used to claim the funds of an HTLC on-chain
+/// or in a lightning channel.
+///
+/// This is not exported to bindings users as we just use [u8; 32] directly
+#[derive(Hash, Copy, Clone, PartialEq, Eq, Ord, PartialOrd)]
+pub struct PaymentPreimage(pub [u8; 32]);
+
+impl Borrow<[u8]> for PaymentPreimage {
+	fn borrow(&self) -> &[u8] {
+		&self.0[..]
+	}
+}
+
+impl_fmt_traits! {
+	impl fmt_traits for PaymentPreimage {
+		const LENGTH: usize = 32;
+	}
+}
+
+/// Converts a `PaymentPreimage` into a `PaymentHash` by hashing the preimage with SHA256.
+impl From<PaymentPreimage> for PaymentHash {
+	fn from(value: PaymentPreimage) -> Self {
+		PaymentHash(Sha256::hash(&value.0).to_byte_array())
+	}
+}
+
+/// The payment secret is used to authenticate the sender of an HTLC to the recipient and tie
+/// multi-part HTLCs together into a single payment.
+///
+/// This is not exported to bindings users as we just use [u8; 32] directly
+#[derive(Hash, Copy, Clone, PartialEq, Eq, Ord, PartialOrd)]
+pub struct PaymentSecret(pub [u8; 32]);
+
+impl Borrow<[u8]> for PaymentSecret {
+	fn borrow(&self) -> &[u8] {
+		&self.0[..]
+	}
+}
+
+impl_fmt_traits! {
+	impl fmt_traits for PaymentSecret {
+		const LENGTH: usize = 32;
+	}
+}
+
+use bech32::{Base32Len, FromBase32, ToBase32, WriteBase32, u5};
+
+impl FromBase32 for PaymentSecret {
+	type Err = bech32::Error;
+
+	fn from_base32(field_data: &[u5]) -> Result<PaymentSecret, bech32::Error> {
+		if field_data.len() != 52 {
+			return Err(bech32::Error::InvalidLength)
+		} else {
+			let data_bytes = Vec::<u8>::from_base32(field_data)?;
+			let mut payment_secret = [0; 32];
+			payment_secret.copy_from_slice(&data_bytes);
+			Ok(PaymentSecret(payment_secret))
+		}
+	}
+}
+
+impl ToBase32 for PaymentSecret {
+	fn write_base32<W: WriteBase32>(&self, writer: &mut W) -> Result<(), <W as WriteBase32>::Err> {
+		(&self.0[..]).write_base32(writer)
+	}
+}
+
+impl Base32Len for PaymentSecret {
+	fn base32_len(&self) -> usize {
+		52
+	}
+}

lightning/Cargo.toml

@@ -40,6 +40,8 @@ grind_signatures = []
 default = ["std", "grind_signatures"]
 
 [dependencies]
+lightning-types = { version = "0.1", path = "../lightning-types", default-features = false }
+
 bech32 = { version = "0.9.1", default-features = false }
 bitcoin = { version = "0.31.2", default-features = false, features = ["secp-recovery"] }
 

lightning/src/lib.rs

@@ -61,6 +61,9 @@ compile_error!("Tests will always fail with cfg=fuzzing");
 
 #[macro_use]
 extern crate alloc;
+
+extern crate lightning_types;
+
 pub extern crate bitcoin;
 #[cfg(any(test, feature = "std"))]
 extern crate core;

lightning/src/ln/mod.rs

@@ -25,7 +25,7 @@ pub mod features;
 pub mod script;
 pub mod types;
 
-pub use types::{ChannelId, PaymentHash, PaymentPreimage, PaymentSecret};
+pub use lightning_types::payment::{PaymentHash, PaymentPreimage, PaymentSecret};
 
 #[cfg(fuzzing)]
 pub mod peer_channel_encryptor;