Ok((block << 40) | (tx_index << 16) | vout_index)
}
+/// LDK has multiple reasons to generate fake short channel ids:
+/// 1) zero-conf channels that don't have a confirmed channel id yet
+/// 2) phantom node payments, to get an scid for the phantom node's phantom channel
+pub(crate) mod fake_scid {
+ use bitcoin::hash_types::BlockHash;
+ use bitcoin::hashes::hex::FromHex;
+ use chain::keysinterface::{Sign, KeysInterface};
+ use util::chacha20::ChaCha20;
+ use util::scid_utils;
+
+ use core::convert::TryInto;
+ use core::ops::Deref;
+
+ const TEST_SEGWIT_ACTIVATION_HEIGHT: u32 = 0;
+ const MAINNET_SEGWIT_ACTIVATION_HEIGHT: u32 = 481_824;
+ const MAX_TX_INDEX: u32 = 2_500;
+ const MAX_NAMESPACES: u8 = 8; // We allocate 3 bits for the namespace identifier.
+ const NAMESPACE_ID_BITMASK: u8 = 0b111;
+
+ /// Fake scids are divided into namespaces, with each namespace having its own identifier between
+ /// [0..7]. This allows us to identify what namespace a fake scid corresponds to upon HTLC
+ /// receipt, and handle the HTLC accordingly. The namespace identifier is encrypted when encoded
+ /// into the fake scid.
+ #[derive(Copy, Clone)]
+ pub(super) enum Namespace {
+ Phantom,
+ // Coming soon: a variant for the zero-conf scid namespace
+ }
+
+ impl Namespace {
+ /// We generate "realistic-looking" random scids here, meaning the scid's block height is
+ /// between segwit activation and the current best known height, and the tx index and output
+ /// index are also selected from a "reasonable" range. We add this logic because it makes it
+ /// non-obvious at a glance that the scid is fake, e.g. if it appears in invoice route hints.
+ pub(super) fn get_fake_scid<Signer: Sign, K: Deref>(&self, highest_seen_blockheight: u32, genesis_hash: &BlockHash, fake_scid_rand_bytes: &[u8; 32], keys_manager: &K) -> u64
+ where K::Target: KeysInterface<Signer = Signer>,
+ {
+ // Ensure we haven't created a namespace that doesn't fit into the 3 bits we've allocated for
+ // namespaces.
+ assert!((*self as u8) < MAX_NAMESPACES);
+ const BLOCKS_PER_MONTH: u32 = 144 /* blocks per day */ * 30 /* days per month */;
+ let rand_bytes = keys_manager.get_secure_random_bytes();
+
+ let segwit_activation_height = segwit_activation_height(genesis_hash);
+ let mut valid_block_range = if highest_seen_blockheight > segwit_activation_height {
+ highest_seen_blockheight - segwit_activation_height
+ } else {
+ 1
+ };
+ // We want to ensure that this fake channel won't conflict with any transactions we haven't
+ // seen yet, in case `highest_seen_blockheight` is updated before we get full information
+ // about transactions confirmed in the given block.
+ if valid_block_range > BLOCKS_PER_MONTH { valid_block_range -= BLOCKS_PER_MONTH; }
+
+ let rand_for_height = u32::from_be_bytes(rand_bytes[..4].try_into().unwrap());
+ let fake_scid_height = segwit_activation_height + rand_for_height % valid_block_range;
+
+ let rand_for_tx_index = u32::from_be_bytes(rand_bytes[4..8].try_into().unwrap());
+ let fake_scid_tx_index = rand_for_tx_index % MAX_TX_INDEX;
+
+ // Put the scid in the given namespace.
+ let fake_scid_vout = self.get_encrypted_vout(fake_scid_height, fake_scid_tx_index, fake_scid_rand_bytes);
+ scid_utils::scid_from_parts(fake_scid_height as u64, fake_scid_tx_index as u64, fake_scid_vout as u64).unwrap()
+ }
+
+ /// We want to ensure that a 3rd party can't identify a payment as belong to a given
+ /// `Namespace`. Therefore, we encrypt it using a random bytes provided by `ChannelManager`.
+ fn get_encrypted_vout(&self, block_height: u32, tx_index: u32, fake_scid_rand_bytes: &[u8; 32]) -> u8 {
+ let mut salt = [0 as u8; 8];
+ let block_height_bytes = block_height.to_be_bytes();
+ salt[0..4].copy_from_slice(&block_height_bytes);
+ let tx_index_bytes = tx_index.to_be_bytes();
+ salt[4..8].copy_from_slice(&tx_index_bytes);
+
+ let mut chacha = ChaCha20::new(fake_scid_rand_bytes, &salt);
+ let mut vout_byte = [*self as u8];
+ chacha.process_in_place(&mut vout_byte);
+ vout_byte[0] & NAMESPACE_ID_BITMASK
+ }
+ }
+
+ pub fn get_phantom_scid<Signer: Sign, K: Deref>(fake_scid_rand_bytes: &[u8; 32], highest_seen_blockheight: u32, genesis_hash: &BlockHash, keys_manager: &K) -> u64
+ where K::Target: KeysInterface<Signer = Signer>,
+ {
+ let namespace = Namespace::Phantom;
+ namespace.get_fake_scid(highest_seen_blockheight, genesis_hash, fake_scid_rand_bytes, keys_manager)
+ }
+
+ fn segwit_activation_height(genesis: &BlockHash) -> u32 {
+ const MAINNET_GENESIS_STR: &'static str = "000000000019d6689c085ae165831e934ff763ae46a2a6c172b3f1b60a8ce26f";
+ if BlockHash::from_hex(MAINNET_GENESIS_STR).unwrap() == *genesis {
+ MAINNET_SEGWIT_ACTIVATION_HEIGHT
+ } else {
+ TEST_SEGWIT_ACTIVATION_HEIGHT
+ }
+ }
+
+ /// Returns whether the given fake scid falls into the given namespace.
+ pub fn is_valid_phantom(fake_scid_rand_bytes: &[u8; 32], scid: u64) -> bool {
+ let block_height = scid_utils::block_from_scid(&scid);
+ let tx_index = scid_utils::tx_index_from_scid(&scid);
+ let namespace = Namespace::Phantom;
+ let valid_vout = namespace.get_encrypted_vout(block_height, tx_index, fake_scid_rand_bytes);
+ valid_vout == scid_utils::vout_from_scid(&scid) as u8
+ }
+
+ #[cfg(test)]
+ mod tests {
+ use bitcoin::blockdata::constants::genesis_block;
+ use bitcoin::network::constants::Network;
+ use util::scid_utils::fake_scid::{is_valid_phantom, MAINNET_SEGWIT_ACTIVATION_HEIGHT, MAX_TX_INDEX, MAX_NAMESPACES, Namespace, NAMESPACE_ID_BITMASK, segwit_activation_height, TEST_SEGWIT_ACTIVATION_HEIGHT};
+ use util::scid_utils;
+ use util::test_utils;
+ use sync::Arc;
+
+ #[test]
+ fn namespace_identifier_is_within_range() {
+ let phantom_namespace = Namespace::Phantom;
+ assert!((phantom_namespace as u8) < MAX_NAMESPACES);
+ assert!((phantom_namespace as u8) <= NAMESPACE_ID_BITMASK);
+ }
+
+ #[test]
+ fn test_segwit_activation_height() {
+ let mainnet_genesis = genesis_block(Network::Bitcoin).header.block_hash();
+ assert_eq!(segwit_activation_height(&mainnet_genesis), MAINNET_SEGWIT_ACTIVATION_HEIGHT);
+
+ let testnet_genesis = genesis_block(Network::Testnet).header.block_hash();
+ assert_eq!(segwit_activation_height(&testnet_genesis), TEST_SEGWIT_ACTIVATION_HEIGHT);
+
+ let signet_genesis = genesis_block(Network::Signet).header.block_hash();
+ assert_eq!(segwit_activation_height(&signet_genesis), TEST_SEGWIT_ACTIVATION_HEIGHT);
+
+ let regtest_genesis = genesis_block(Network::Regtest).header.block_hash();
+ assert_eq!(segwit_activation_height(®test_genesis), TEST_SEGWIT_ACTIVATION_HEIGHT);
+ }
+
+ #[test]
+ fn test_is_valid_phantom() {
+ let namespace = Namespace::Phantom;
+ let fake_scid_rand_bytes = [0; 32];
+ let valid_encrypted_vout = namespace.get_encrypted_vout(0, 0, &fake_scid_rand_bytes);
+ let valid_fake_scid = scid_utils::scid_from_parts(0, 0, valid_encrypted_vout as u64).unwrap();
+ assert!(is_valid_phantom(&fake_scid_rand_bytes, valid_fake_scid));
+ let invalid_fake_scid = scid_utils::scid_from_parts(0, 0, 12).unwrap();
+ assert!(!is_valid_phantom(&fake_scid_rand_bytes, invalid_fake_scid));
+ }
+
+ #[test]
+ fn test_get_fake_scid() {
+ let mainnet_genesis = genesis_block(Network::Bitcoin).header.block_hash();
+ let seed = [0; 32];
+ let fake_scid_rand_bytes = [1; 32];
+ let keys_manager = Arc::new(test_utils::TestKeysInterface::new(&seed, Network::Testnet));
+ let namespace = Namespace::Phantom;
+ let fake_scid = namespace.get_fake_scid(500_000, &mainnet_genesis, &fake_scid_rand_bytes, &keys_manager);
+
+ let fake_height = scid_utils::block_from_scid(&fake_scid);
+ assert!(fake_height >= MAINNET_SEGWIT_ACTIVATION_HEIGHT);
+ assert!(fake_height <= 500_000);
+
+ let fake_tx_index = scid_utils::tx_index_from_scid(&fake_scid);
+ assert!(fake_tx_index <= MAX_TX_INDEX);
+
+ let fake_vout = scid_utils::vout_from_scid(&fake_scid);
+ assert!(fake_vout < MAX_NAMESPACES as u16);
+ }
+ }
+}
+
#[cfg(test)]
mod tests {
use super::*;
projects / rust-lightning / blobdiff