Actual no_std support
[rust-lightning] / lightning / src / ln / chan_utils.rs
index b698558e1b26b5a6c7a18cd142f4c8bce6e341b5..4690d298aedee2a7f16b18adf09ffee8ac202c4e 100644 (file)
@@ -31,6 +31,7 @@ use bitcoin::secp256k1::{Secp256k1, Signature, Message};
 use bitcoin::secp256k1::Error as SecpError;
 use bitcoin::secp256k1;
 
+use io;
 use prelude::*;
 use core::cmp;
 use ln::chan_utils;
@@ -167,23 +168,23 @@ impl CounterpartyCommitmentSecrets {
 }
 
 impl Writeable for CounterpartyCommitmentSecrets {
-       fn write<W: Writer>(&self, writer: &mut W) -> Result<(), ::std::io::Error> {
+       fn write<W: Writer>(&self, writer: &mut W) -> Result<(), io::Error> {
                for &(ref secret, ref idx) in self.old_secrets.iter() {
                        writer.write_all(secret)?;
                        writer.write_all(&byte_utils::be64_to_array(*idx))?;
                }
-               write_tlv_fields!(writer, {}, {});
+               write_tlv_fields!(writer, {});
                Ok(())
        }
 }
 impl Readable for CounterpartyCommitmentSecrets {
-       fn read<R: ::std::io::Read>(reader: &mut R) -> Result<Self, DecodeError> {
+       fn read<R: io::Read>(reader: &mut R) -> Result<Self, DecodeError> {
                let mut old_secrets = [([0; 32], 1 << 48); 49];
                for &mut (ref mut secret, ref mut idx) in old_secrets.iter_mut() {
                        *secret = Readable::read(reader)?;
                        *idx = Readable::read(reader)?;
                }
-               read_tlv_fields!(reader, {}, {});
+               read_tlv_fields!(reader, {});
                Ok(Self { old_secrets })
        }
 }
@@ -318,12 +319,12 @@ pub struct TxCreationKeys {
 }
 
 impl_writeable_tlv_based!(TxCreationKeys, {
-       (0, per_commitment_point),
-       (2, revocation_key),
-       (4, broadcaster_htlc_key),
-       (6, countersignatory_htlc_key),
-       (8, broadcaster_delayed_payment_key),
-}, {}, {});
+       (0, per_commitment_point, required),
+       (2, revocation_key, required),
+       (4, broadcaster_htlc_key, required),
+       (6, countersignatory_htlc_key, required),
+       (8, broadcaster_delayed_payment_key, required),
+});
 
 /// One counterparty's public keys which do not change over the life of a channel.
 #[derive(Clone, PartialEq)]
@@ -350,12 +351,12 @@ pub struct ChannelPublicKeys {
 }
 
 impl_writeable_tlv_based!(ChannelPublicKeys, {
-       (0, funding_pubkey),
-       (2, revocation_basepoint),
-       (4, payment_point),
-       (6, delayed_payment_basepoint),
-       (8, htlc_basepoint),
-}, {}, {});
+       (0, funding_pubkey, required),
+       (2, revocation_basepoint, required),
+       (4, payment_point, required),
+       (6, delayed_payment_basepoint, required),
+       (8, htlc_basepoint, required),
+});
 
 impl TxCreationKeys {
        /// Create per-state keys from channel base points and the per-commitment point.
@@ -429,13 +430,12 @@ pub struct HTLCOutputInCommitment {
 }
 
 impl_writeable_tlv_based!(HTLCOutputInCommitment, {
-       (0, offered),
-       (2, amount_msat),
-       (4, cltv_expiry),
-       (6, payment_hash),
-}, {
-       (8, transaction_output_index)
-}, {});
+       (0, offered, required),
+       (2, amount_msat, required),
+       (4, cltv_expiry, required),
+       (6, payment_hash, required),
+       (8, transaction_output_index, option),
+});
 
 #[inline]
 pub(crate) fn get_htlc_redeemscript_with_explicit_keys(htlc: &HTLCOutputInCommitment, broadcaster_htlc_key: &PublicKey, countersignatory_htlc_key: &PublicKey, revocation_key: &PublicKey) -> Script {
@@ -525,12 +525,18 @@ pub fn make_funding_redeemscript(broadcaster: &PublicKey, countersignatory: &Pub
        }.push_opcode(opcodes::all::OP_PUSHNUM_2).push_opcode(opcodes::all::OP_CHECKMULTISIG).into_script()
 }
 
-/// panics if htlc.transaction_output_index.is_none()!
-pub fn build_htlc_transaction(prev_hash: &Txid, feerate_per_kw: u32, contest_delay: u16, htlc: &HTLCOutputInCommitment, broadcaster_delayed_payment_key: &PublicKey, revocation_key: &PublicKey) -> Transaction {
+/// Builds an unsigned HTLC-Success or HTLC-Timeout transaction from the given channel and HTLC
+/// parameters. This is used by [`TrustedCommitmentTransaction::get_htlc_sigs`] to fetch the
+/// transaction which needs signing, and can be used to construct an HTLC transaction which is
+/// broadcastable given a counterparty HTLC signature.
+///
+/// Panics if htlc.transaction_output_index.is_none() (as such HTLCs do not appear in the
+/// commitment transaction).
+pub fn build_htlc_transaction(commitment_txid: &Txid, feerate_per_kw: u32, contest_delay: u16, htlc: &HTLCOutputInCommitment, broadcaster_delayed_payment_key: &PublicKey, revocation_key: &PublicKey) -> Transaction {
        let mut txins: Vec<TxIn> = Vec::new();
        txins.push(TxIn {
                previous_output: OutPoint {
-                       txid: prev_hash.clone(),
+                       txid: commitment_txid.clone(),
                        vout: htlc.transaction_output_index.expect("Can't build an HTLC transaction for a dust output"),
                },
                script_sig: Script::new(),
@@ -620,18 +626,17 @@ impl ChannelTransactionParameters {
 }
 
 impl_writeable_tlv_based!(CounterpartyChannelTransactionParameters, {
-       (0, pubkeys),
-       (2, selected_contest_delay),
-}, {}, {});
+       (0, pubkeys, required),
+       (2, selected_contest_delay, required),
+});
 
 impl_writeable_tlv_based!(ChannelTransactionParameters, {
-       (0, holder_pubkeys),
-       (2, holder_selected_contest_delay),
-       (4, is_outbound_from_holder),
-}, {
-       (6, counterparty_parameters),
-       (8, funding_outpoint),
-}, {});
+       (0, holder_pubkeys, required),
+       (2, holder_selected_contest_delay, required),
+       (4, is_outbound_from_holder, required),
+       (6, counterparty_parameters, option),
+       (8, funding_outpoint, option),
+});
 
 /// Static channel fields used to build transactions given per-commitment fields, organized by
 /// broadcaster/countersignatory.
@@ -714,11 +719,10 @@ impl PartialEq for HolderCommitmentTransaction {
 }
 
 impl_writeable_tlv_based!(HolderCommitmentTransaction, {
-       (0, inner),
-       (2, counterparty_sig),
-       (4, holder_sig_first),
-}, {}, {
-       (6, counterparty_htlc_sigs),
+       (0, inner, required),
+       (2, counterparty_sig, required),
+       (4, holder_sig_first, required),
+       (6, counterparty_htlc_sigs, vec_type),
 });
 
 impl HolderCommitmentTransaction {
@@ -803,9 +807,9 @@ pub struct BuiltCommitmentTransaction {
 }
 
 impl_writeable_tlv_based!(BuiltCommitmentTransaction, {
-       (0, transaction),
-       (2, txid)
-}, {}, {});
+       (0, transaction, required),
+       (2, txid, required),
+});
 
 impl BuiltCommitmentTransaction {
        /// Get the SIGHASH_ALL sighash value of the transaction.
@@ -860,14 +864,13 @@ impl PartialEq for CommitmentTransaction {
 }
 
 impl_writeable_tlv_based!(CommitmentTransaction, {
-       (0, commitment_number),
-       (2, to_broadcaster_value_sat),
-       (4, to_countersignatory_value_sat),
-       (6, feerate_per_kw),
-       (8, keys),
-       (10, built),
-}, {}, {
-       (12, htlcs),
+       (0, commitment_number, required),
+       (2, to_broadcaster_value_sat, required),
+       (4, to_countersignatory_value_sat, required),
+       (6, feerate_per_kw, required),
+       (8, keys, required),
+       (10, built, required),
+       (12, htlcs, vec_type),
 });
 
 impl CommitmentTransaction {
@@ -1177,7 +1180,12 @@ impl<'a> TrustedCommitmentTransaction<'a> {
        }
 }
 
-/// Get the transaction number obscure factor
+/// Commitment transaction numbers which appear in the transactions themselves are XOR'd with a
+/// shared secret first. This prevents on-chain observers from discovering how many commitment
+/// transactions occurred in a channel before it was closed.
+///
+/// This function gets the shared secret from relevant channel public keys and can be used to
+/// "decrypt" the commitment transaction number given a commitment transaction on-chain.
 pub fn get_commitment_transaction_number_obscure_factor(
        broadcaster_payment_basepoint: &PublicKey,
        countersignatory_payment_basepoint: &PublicKey,