Move invoice signing behind KeysInterface

fuzz/src/chanmon_consistency.rs

@@ -56,6 +56,7 @@ use utils::test_logger;
 use utils::test_persister::TestPersister;
 
 use bitcoin::secp256k1::key::{PublicKey,SecretKey};
+use bitcoin::secp256k1::recovery::RecoverableSignature;
 use bitcoin::secp256k1::Secp256k1;
 
 use std::mem;
@@ -206,6 +207,10 @@ impl KeysInterface for KeyProvider {
 			disable_revocation_policy_check: false,
 		})
 	}
+
+	fn sign_invoice(&self, _invoice_preimage: Vec<u8>) -> Result<RecoverableSignature, ()> {
+		unreachable!()
+	}
 }
 
 impl KeyProvider {

fuzz/src/full_stack.rs

@@ -48,6 +48,7 @@ use utils::test_logger;
 use utils::test_persister::TestPersister;
 
 use bitcoin::secp256k1::key::{PublicKey,SecretKey};
+use bitcoin::secp256k1::recovery::RecoverableSignature;
 use bitcoin::secp256k1::Secp256k1;
 
 use std::cell::RefCell;
@@ -313,6 +314,10 @@ impl KeysInterface for KeyProvider {
 	fn read_chan_signer(&self, data: &[u8]) -> Result<EnforcingSigner, DecodeError> {
 		EnforcingSigner::read(&mut std::io::Cursor::new(data))
 	}
+
+	fn sign_invoice(&self, _invoice_preimage: Vec<u8>) -> Result<RecoverableSignature, ()> {
+		unreachable!()
+	}
 }
 
 #[inline]

lightning/src/chain/keysinterface.rs

@@ -26,6 +26,7 @@ use bitcoin::hash_types::WPubkeyHash;
 
 use bitcoin::secp256k1::key::{SecretKey, PublicKey};
 use bitcoin::secp256k1::{Secp256k1, Signature, Signing};
+use bitcoin::secp256k1::recovery::RecoverableSignature;
 use bitcoin::secp256k1;
 
 use util::{byte_utils, transaction_utils};
@@ -391,6 +392,12 @@ pub trait KeysInterface {
 	/// contain no versioning scheme. You may wish to include your own version prefix and ensure
 	/// you've read all of the provided bytes to ensure no corruption occurred.
 	fn read_chan_signer(&self, reader: &[u8]) -> Result<Self::Signer, DecodeError>;
+
+	/// Sign an invoice's preimage (note that this is the preimage of the invoice, not the HTLC's
+	/// preimage). By parameterizing by the preimage instead of the hash, we allow implementors of
+	/// this trait to parse the invoice and make sure they're signing what they expect, rather than
+	/// blindly signing the hash.
+	fn sign_invoice(&self, invoice_preimage: Vec<u8>) -> Result<RecoverableSignature, ()>;
 }
 
 #[derive(Clone)]
@@ -1047,6 +1054,10 @@ impl KeysInterface for KeysManager {
 	fn read_chan_signer(&self, reader: &[u8]) -> Result<Self::Signer, DecodeError> {
 		InMemorySigner::read(&mut std::io::Cursor::new(reader))
 	}
+
+	fn sign_invoice(&self, invoice_preimage: Vec<u8>) -> Result<RecoverableSignature, ()> {
+		Ok(self.secp_ctx.sign_recoverable(&hash_to_message!(&Sha256::hash(&invoice_preimage)), &self.get_node_secret()))
+	}
 }
 
 // Ensure that BaseSign can have a vtable

lightning/src/ln/channel.rs

@@ -4843,6 +4843,7 @@ mod tests {
 	use bitcoin::secp256k1::{Secp256k1, Message, Signature, All};
 	use bitcoin::secp256k1::ffi::Signature as FFISignature;
 	use bitcoin::secp256k1::key::{SecretKey,PublicKey};
+	use bitcoin::secp256k1::recovery::RecoverableSignature;
 	use bitcoin::hashes::sha256::Hash as Sha256;
 	use bitcoin::hashes::Hash;
 	use bitcoin::hash_types::{Txid, WPubkeyHash};
@@ -4888,6 +4889,7 @@ mod tests {
 		}
 		fn get_secure_random_bytes(&self) -> [u8; 32] { [0; 32] }
 		fn read_chan_signer(&self, _data: &[u8]) -> Result<Self::Signer, DecodeError> { panic!(); }
+		fn sign_invoice(&self, _invoice_preimage: Vec<u8>) -> Result<RecoverableSignature, ()> { panic!(); }
 	}
 
 	fn public_from_secret_hex(secp_ctx: &Secp256k1<All>, hex: &str) -> PublicKey {

lightning/src/util/test_utils.rs

@@ -32,6 +32,7 @@ use bitcoin::network::constants::Network;
 use bitcoin::hash_types::{BlockHash, Txid};
 
 use bitcoin::secp256k1::{SecretKey, PublicKey, Secp256k1, Signature};
+use bitcoin::secp256k1::recovery::RecoverableSignature;
 
 use regex;
 
@@ -75,6 +76,7 @@ impl keysinterface::KeysInterface for OnlyReadsKeysInterface {
 	fn read_chan_signer(&self, reader: &[u8]) -> Result<Self::Signer, msgs::DecodeError> {
 		EnforcingSigner::read(&mut std::io::Cursor::new(reader))
 	}
+	fn sign_invoice(&self, _invoice_preimage: Vec<u8>) -> Result<RecoverableSignature, ()> { unreachable!(); }
 }
 
 pub struct TestChainMonitor<'a> {
@@ -483,6 +485,10 @@ impl keysinterface::KeysInterface for TestKeysInterface {
 			disable_revocation_policy_check: self.disable_revocation_policy_check,
 		})
 	}
+
+	fn sign_invoice(&self, invoice_preimage: Vec<u8>) -> Result<RecoverableSignature, ()> {
+		self.backing.sign_invoice(invoice_preimage)
+	}
 }