Handle PeerStorageRetrieval in ChannelManager

Ensure ChannelManager properly handles peer_storage_retrieval.

 - Write internal_peer_storage_retreival to verify if we recv correct peer storage.
 - Send error if we get invalid peer_storage data.

Author: Aditya Sharma

lightning/src/ln/channelmanager.rs

@@ -52,6 +52,7 @@ use crate::ln::types::ChannelId;
 use crate::types::payment::{PaymentHash, PaymentPreimage, PaymentSecret};
 use crate::ln::channel::{self, Channel, ChannelError, ChannelUpdateStatus, FundedChannel, ShutdownResult, UpdateFulfillCommitFetch, OutboundV1Channel, ReconnectionMsg, InboundV1Channel, WithChannelContext};
 use crate::ln::channel::PendingV2Channel;
+use crate::ln::our_peer_storage::OurPeerStorage;
 use crate::ln::channel_state::ChannelDetails;
 use crate::types::features::{Bolt12InvoiceFeatures, ChannelFeatures, ChannelTypeFeatures, InitFeatures, NodeFeatures};
 #[cfg(any(feature = "_test_utils", test))]
@@ -8322,15 +8323,40 @@ This indicates a bug inside LDK. Please report this error at https://github.com/
 		}
 	}
 
-	fn internal_peer_storage_retrieval(&self, counterparty_node_id: PublicKey, _msg: msgs::PeerStorageRetrieval) -> Result<(), MsgHandleErrInternal> {
-		// TODO: Decrypt and check if have any stale or missing ChannelMonitor.
+	fn internal_peer_storage_retrieval(&self, counterparty_node_id: PublicKey, msg: msgs::PeerStorageRetrieval) -> Result<(), MsgHandleErrInternal> {
+		// TODO: Check if have any stale or missing ChannelMonitor.
 		let logger = WithContext::from(&self.logger, Some(counterparty_node_id), None, None);
 
-		log_debug!(logger, "Received unexpected peer_storage_retrieval from {}. This is unusual since we do not yet distribute peer storage. Sending a warning.", log_pubkey!(counterparty_node_id));
+		// `MIN_CYPHERTEXT_LEN` is 16 bytes because the mandatory authentication tag length is 16 bytes.
+		const MIN_CYPHERTEXT_LEN: usize = 16;
 
-		Err(MsgHandleErrInternal::from_chan_no_close(ChannelError::Warn(
-			"Invalid peer_storage_retrieval message received.".into(),
-		), ChannelId([0; 32])))
+		if msg.data.len() < MIN_CYPHERTEXT_LEN {
+			log_debug!(logger, "Invalid YourPeerStorage received from {}", log_pubkey!(counterparty_node_id));
+			return Err(MsgHandleErrInternal::from_chan_no_close(ChannelError::Warn(
+				"Invalid peer_storage_retrieval message received.".into(),
+			), ChannelId([0; 32])));
+		}
+
+		let our_peerstorage_encryption_key = self.node_signer.get_peer_storage_key();
+		let our_peer_storage = OurPeerStorage::new(msg.data);
+
+		match our_peer_storage.decrypt_our_peer_storage(our_peerstorage_encryption_key) {
+			Ok(decrypted_data) => {
+				// Decryption successful.
+				if decrypted_data.len() == 0 {
+					log_trace!(logger, "Received a peer storage from peer {} with 0 channels.", log_pubkey!(counterparty_node_id));
+				}
+			}
+			Err(_) => {
+				log_debug!(logger, "Invalid YourPeerStorage received from {}", log_pubkey!(counterparty_node_id));
+
+				return Err(MsgHandleErrInternal::from_chan_no_close(ChannelError::Ignore(
+					"Invalid peer_storage_retrieval message received.".into(),
+				), ChannelId([0; 32])));
+			}
+		}
+
+		Ok(())
 	}
 
 	fn internal_peer_storage(&self, counterparty_node_id: PublicKey, msg: msgs::PeerStorage) -> Result<(), MsgHandleErrInternal> {
@@ -16299,7 +16325,7 @@ mod tests {
 pub mod bench {
 	use crate::chain::Listen;
 	use crate::chain::chainmonitor::{ChainMonitor, Persist};
-	use crate::sign::{KeysManager, InMemorySigner};
+	use crate::sign::{KeysManager, InMemorySigner, NodeSigner};
 	use crate::events::Event;
 	use crate::ln::channelmanager::{BestBlock, ChainParameters, ChannelManager, PaymentHash, PaymentPreimage, PaymentId, RecipientOnionFields, Retry};
 	use crate::ln::functional_test_utils::*;