// SPDX-License-Identifier: CC0-1.0
//! BIP152 Compact Blocks
//!
//! Implementation of compact blocks data structure and algorithms.
//!
use crate::prelude::*;
use crate::io;
use core::{convert, convert::TryFrom, fmt, mem};
#[cfg(feature = "std")]
use std::error;
use crate::consensus::encode::{self, Decodable, Encodable, VarInt};
use crate::hashes::{sha256, siphash24, Hash};
use crate::internal_macros::{impl_array_newtype, impl_bytes_newtype, impl_consensus_encoding};
use crate::util::endian;
use crate::{Block, BlockHash, BlockHeader, Transaction};
/// A BIP-152 error
#[derive(Clone, PartialEq, Eq, Debug, Copy, PartialOrd, Ord, Hash)]
pub enum Error {
/// An unknown version number was used.
UnknownVersion,
/// The prefill slice provided was invalid.
InvalidPrefill,
}
impl fmt::Display for Error {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
match *self {
Error::UnknownVersion => write!(f, "an unknown version number was used"),
Error::InvalidPrefill => write!(f, "the prefill slice provided was invalid"),
}
}
}
#[cfg(feature = "std")]
impl error::Error for Error {}
/// A [PrefilledTransaction] structure is used in [HeaderAndShortIds] to
/// provide a list of a few transactions explicitly.
#[derive(PartialEq, Eq, Clone, Debug, PartialOrd, Ord, Hash)]
pub struct PrefilledTransaction {
/// The index of the transaction in the block.
///
/// This field is differentially encoded relative to the previous
/// prefilled transaction as described as follows:
///
/// > Several uses of CompactSize below are "differentially encoded". For
/// > these, instead of using raw indexes, the number encoded is the
/// > difference between the current index and the previous index, minus one.
/// > For example, a first index of 0 implies a real index of 0, a second
/// > index of 0 thereafter refers to a real index of 1, etc.
pub idx: u16,
/// The actual transaction.
pub tx: Transaction,
}
impl convert::AsRef<Transaction> for PrefilledTransaction {
fn as_ref(&self) -> &Transaction {
&self.tx
}
}
impl Encodable for PrefilledTransaction {
#[inline]
fn consensus_encode<S: io::Write + ?Sized>(&self, mut s: &mut S) -> Result<usize, io::Error> {
Ok(VarInt(self.idx as u64).consensus_encode(&mut s)? + self.tx.consensus_encode(&mut s)?)
}
}
impl Decodable for PrefilledTransaction {
#[inline]
fn consensus_decode<D: io::Read + ?Sized>(
mut d: &mut D,
) -> Result<PrefilledTransaction, encode::Error> {
let idx = VarInt::consensus_decode(&mut d)?.0;
let idx = u16::try_from(idx)
.map_err(|_| encode::Error::ParseFailed("BIP152 prefilled tx index out of bounds"))?;
let tx = Transaction::consensus_decode(&mut d)?;
Ok(PrefilledTransaction { idx, tx })
}
}
/// Short transaction IDs are used to represent a transaction without sending a full 256-bit hash.
#[derive(PartialEq, Eq, Clone, Copy, Hash, Default, PartialOrd, Ord)]
pub struct ShortId([u8; 6]);
impl_array_newtype!(ShortId, u8, 6);
impl_bytes_newtype!(ShortId, 6);
impl ShortId {
/// Calculate the SipHash24 keys used to calculate short IDs.
pub fn calculate_siphash_keys(header: &BlockHeader, nonce: u64) -> (u64, u64) {
// 1. single-SHA256 hashing the block header with the nonce appended (in little-endian)
let h = {
let mut engine = sha256::Hash::engine();
header.consensus_encode(&mut engine).expect("engines don't error");
nonce.consensus_encode(&mut engine).expect("engines don't error");
sha256::Hash::from_engine(engine)
};
// 2. Running SipHash-2-4 with the input being the transaction ID and the keys (k0/k1)
// set to the first two little-endian 64-bit integers from the above hash, respectively.
(endian::slice_to_u64_le(&h[0..8]), endian::slice_to_u64_le(&h[8..16]))
}
/// Calculate the short ID with the given (w)txid and using the provided SipHash keys.
pub fn with_siphash_keys<T: AsRef<[u8]>>(txid: &T, siphash_keys: (u64, u64)) -> ShortId {
// 2. Running SipHash-2-4 with the input being the transaction ID and the keys (k0/k1)
// set to the first two little-endian 64-bit integers from the above hash, respectively.
let hash = siphash24::Hash::hash_with_keys(siphash_keys.0, siphash_keys.1, txid.as_ref());
// 3. Dropping the 2 most significant bytes from the SipHash output to make it 6 bytes.
let mut id = ShortId([0; 6]);
id.0.copy_from_slice(&hash[0..6]);
id
}
}
impl Encodable for ShortId {
#[inline]
fn consensus_encode<S: io::Write + ?Sized>(&self, s: &mut S) -> Result<usize, io::Error> {
self.0.consensus_encode(s)
}
}
impl Decodable for ShortId {
#[inline]
fn consensus_decode<D: io::Read + ?Sized>(d: &mut D) -> Result<ShortId, encode::Error> {
Ok(ShortId(Decodable::consensus_decode(d)?))
}
}
/// A [HeaderAndShortIds] structure is used to relay a block header, the short
/// transactions IDs used for matching already-available transactions, and a
/// select few transactions which we expect a peer may be missing.
#[derive(PartialEq, Eq, Clone, Debug, PartialOrd, Ord, Hash)]
pub struct HeaderAndShortIds {
/// The header of the block being provided.
pub header: BlockHeader,
/// A nonce for use in short transaction ID calculations.
pub nonce: u64,
/// The short transaction IDs calculated from the transactions
/// which were not provided explicitly in prefilled_txs.
pub short_ids: Vec<ShortId>,
/// Used to provide the coinbase transaction and a select few
/// which we expect a peer may be missing.
pub prefilled_txs: Vec<PrefilledTransaction>,
}
impl_consensus_encoding!(HeaderAndShortIds, header, nonce, short_ids, prefilled_txs);
impl HeaderAndShortIds {
/// Create a new [HeaderAndShortIds] from a full block.
///
/// The version number must be either 1 or 2.
///
/// The `prefill` slice indicates which transactions should be prefilled in
/// the block. It should contain the indexes in the block of the txs to
/// prefill. It must be ordered. 0 should not be included as the
/// coinbase tx is always prefilled.
///
/// > Nodes SHOULD NOT use the same nonce across multiple different blocks.
pub fn from_block(
block: &Block,
nonce: u64,
version: u32,
mut prefill: &[usize],
) -> Result<HeaderAndShortIds, Error> {
if version != 1 && version != 2 {
return Err(Error::UnknownVersion);
}
let siphash_keys = ShortId::calculate_siphash_keys(&block.header, nonce);
let mut prefilled = Vec::with_capacity(prefill.len() + 1); // +1 for coinbase tx
let mut short_ids = Vec::with_capacity(block.txdata.len() - prefill.len());
let mut last_prefill = 0;
for (idx, tx) in block.txdata.iter().enumerate() {
// Check if we should prefill this tx.
let prefill_tx = if prefill.first() == Some(&idx) {
prefill = &prefill[1..];
true
} else {
idx == 0 // Always prefill coinbase.
};
if prefill_tx {
let diff_idx = idx - last_prefill;
last_prefill = idx + 1;
prefilled.push(PrefilledTransaction {
idx: diff_idx as u16,
tx: match version {
// > As encoded in "tx" messages sent in response to getdata MSG_TX
1 => {
// strip witness for version 1
let mut no_witness = tx.clone();
no_witness.input.iter_mut().for_each(|i| i.witness.clear());
no_witness
}
// > Transactions inside cmpctblock messages (both those used as direct
// > announcement and those in response to getdata) and in blocktxn should
// > include witness data, using the same format as responses to getdata
// > MSG_WITNESS_TX, specified in BIP144.
2 => tx.clone(),
_ => unreachable!(),
},
});
} else {
short_ids.push(ShortId::with_siphash_keys(
&match version {
1 => tx.txid().as_hash(),
2 => tx.wtxid().as_hash(),
_ => unreachable!(),
},
siphash_keys,
));
}
}
if !prefill.is_empty() {
return Err(Error::InvalidPrefill);
}
Ok(HeaderAndShortIds {
header: block.header,
nonce,
// Provide coinbase prefilled.
prefilled_txs: prefilled,
short_ids,
})
}
}
/// A [BlockTransactionsRequest] structure is used to list transaction indexes
/// in a block being requested.
#[derive(PartialEq, Eq, Clone, Debug, PartialOrd, Ord, Hash)]
pub struct BlockTransactionsRequest {
/// The blockhash of the block which the transactions being requested are in.
pub block_hash: BlockHash,
/// The indexes of the transactions being requested in the block.
///
/// Warning: Encoding panics with [`u64::MAX`] values. See [`BlockTransactionsRequest::consensus_encode()`]
pub indexes: Vec<u64>,
}
impl Encodable for BlockTransactionsRequest {
/// # Panics
///
/// Panics if the index overflows [`u64::MAX`]. This happens when [`BlockTransactionsRequest::indexes`]
/// contains an entry with the value [`u64::MAX`] as `u64` overflows during differential encoding.
fn consensus_encode<S: io::Write + ?Sized>(&self, mut s: &mut S) -> Result<usize, io::Error> {
let mut len = self.block_hash.consensus_encode(&mut s)?;
// Manually encode indexes because they are differentially encoded VarInts.
len += VarInt(self.indexes.len() as u64).consensus_encode(&mut s)?;
let mut last_idx = 0;
for idx in &self.indexes {
len += VarInt(*idx - last_idx).consensus_encode(&mut s)?;
last_idx = *idx + 1; // can panic here
}
Ok(len)
}
}
impl Decodable for BlockTransactionsRequest {
fn consensus_decode<D: io::Read + ?Sized>(
mut d: &mut D,
) -> Result<BlockTransactionsRequest, encode::Error> {
Ok(BlockTransactionsRequest {
block_hash: BlockHash::consensus_decode(&mut d)?,
indexes: {
// Manually decode indexes because they are differentially encoded VarInts.
let nb_indexes = VarInt::consensus_decode(&mut d)?.0 as usize;
// Since the number of indices ultimately represent transactions,
// we can limit the number of indices to the maximum number of
// transactions that would be allowed in a vector.
let byte_size = (nb_indexes as usize)
.checked_mul(mem::size_of::<Transaction>())
.ok_or(encode::Error::ParseFailed("Invalid length"))?;
if byte_size > encode::MAX_VEC_SIZE {
return Err(encode::Error::OversizedVectorAllocation {
requested: byte_size,
max: encode::MAX_VEC_SIZE,
});
}
let mut indexes = Vec::with_capacity(nb_indexes);
let mut last_index: u64 = 0;
for _ in 0..nb_indexes {
let differential: VarInt = Decodable::consensus_decode(&mut d)?;
last_index = match last_index.checked_add(differential.0) {
Some(r) => r,
None => return Err(encode::Error::ParseFailed("block index overflow")),
};
indexes.push(last_index);
last_index = match last_index.checked_add(1) {
Some(r) => r,
None => return Err(encode::Error::ParseFailed("block index overflow")),
};
}
indexes
},
})
}
}
/// A transaction index is requested that is out of range from the
/// corresponding block.
#[derive(Clone, PartialEq, Eq, Debug, Copy, PartialOrd, Ord, Hash)]
pub struct TxIndexOutOfRangeError(u64);
impl fmt::Display for TxIndexOutOfRangeError {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
write!(
f,
"a transaction index is requested that is \
out of range from the corresponding block: {}",
self.0,
)
}
}
#[cfg(feature = "std")]
impl error::Error for TxIndexOutOfRangeError {}
/// A [BlockTransactions] structure is used to provide some of the transactions
/// in a block, as requested.
#[derive(PartialEq, Eq, Clone, Debug, PartialOrd, Ord, Hash)]
pub struct BlockTransactions {
/// The blockhash of the block which the transactions being provided are in.
pub block_hash: BlockHash,
/// The transactions provided.
pub transactions: Vec<Transaction>,
}
impl_consensus_encoding!(BlockTransactions, block_hash, transactions);
impl BlockTransactions {
/// Construct a [BlockTransactions] from a [BlockTransactionsRequest] and
/// the corresponsing full [Block] by providing all requested transactions.
pub fn from_request(
request: &BlockTransactionsRequest,
block: &Block,
) -> Result<BlockTransactions, TxIndexOutOfRangeError> {
Ok(BlockTransactions {
block_hash: request.block_hash,
transactions: {
let mut txs = Vec::with_capacity(request.indexes.len());
for idx in &request.indexes {
if *idx >= block.txdata.len() as u64 {
return Err(TxIndexOutOfRangeError(*idx));
}
txs.push(block.txdata[*idx as usize].clone());
}
txs
},
})
}
}
#[cfg(test)]
mod test {
use super::*;
use crate::consensus::encode::{deserialize, serialize};
use crate::hashes::hex::FromHex;
use crate::{
Block, BlockHash, BlockHeader, OutPoint, Script, Sequence, Transaction, TxIn, TxMerkleNode,
TxOut, Txid, Witness, LockTime,
};
fn dummy_tx(nonce: &[u8]) -> Transaction {
Transaction {
version: 1,
lock_time: LockTime::from_consensus(2).into(),
input: vec![TxIn {
previous_output: OutPoint::new(Txid::hash(nonce), 0),
script_sig: Script::new(),
sequence: Sequence(1),
witness: Witness::new(),
}],
output: vec![TxOut { value: 1, script_pubkey: Script::new() }],
}
}
fn dummy_block() -> Block {
Block {
header: BlockHeader {
version: 1,
prev_blockhash: BlockHash::hash(&[0]),
merkle_root: TxMerkleNode::hash(&[1]),
time: 2,
bits: 3,
nonce: 4,
},
txdata: vec![dummy_tx(&[2]), dummy_tx(&[3]), dummy_tx(&[4])],
}
}
#[test]
fn test_header_and_short_ids_from_block() {
let block = dummy_block();
let compact = HeaderAndShortIds::from_block(&block, 42, 2, &[]).unwrap();
assert_eq!(compact.nonce, 42);
assert_eq!(compact.short_ids.len(), 2);
assert_eq!(compact.prefilled_txs.len(), 1);
assert_eq!(compact.prefilled_txs[0].idx, 0);
assert_eq!(&compact.prefilled_txs[0].tx, &block.txdata[0]);
let compact = HeaderAndShortIds::from_block(&block, 42, 2, &[0, 1, 2]).unwrap();
let idxs = compact.prefilled_txs.iter().map(|t| t.idx).collect::<Vec<_>>();
assert_eq!(idxs, vec![0, 0, 0]);
let compact = HeaderAndShortIds::from_block(&block, 42, 2, &[2]).unwrap();
let idxs = compact.prefilled_txs.iter().map(|t| t.idx).collect::<Vec<_>>();
assert_eq!(idxs, vec![0, 1]);
}
#[test]
fn test_compact_block_vector() {
// Tested with Elements implementation of compact blocks.
let raw_block = Vec::<u8>::from_hex("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").unwrap();
let raw_compact = Vec::<u8>::from_hex("000000206c750a364035aefd5f81508a08769975116d9195312ee4520dceac39e1fdc62c4dc67473b8e354358c1e610afeaff7410858bd45df43e2940f8a62bd3d5e3ac943c2975cffff7f2000000000a4df3c3744da89fa012656c015196f0100020000000001010000000000000000000000000000000000000000000000000000000000000000ffffffff04016b0101ffffffff020006062a0100000001510000000000000000266a24aa21a9ed4a3d9f3343dafcc0d6f6d4310f2ee5ce273ed34edca6c75db3a73e7f368734200120000000000000000000000000000000000000000000000000000000000000000000000000").unwrap();
let block: Block = deserialize(&raw_block).unwrap();
let nonce = 18053200567810711460;
let compact = HeaderAndShortIds::from_block(&block, nonce, 2, &[]).unwrap();
let compact_expected = deserialize(&raw_compact).unwrap();
assert_eq!(compact, compact_expected);
}
#[test]
fn test_getblocktx_differential_encoding_de_and_serialization() {
let testcases = vec![
// differentially encoded VarInts, indicies
(vec![4, 0, 5, 1, 10], vec![0, 6, 8, 19]),
(vec![1, 0], vec![0]),
(vec![5, 0, 0, 0, 0, 0], vec![0, 1, 2, 3, 4]),
(vec![3, 1, 1, 1], vec![1, 3, 5]),
(vec![3, 0, 0, 253, 0, 1], vec![0, 1, 258]), // .., 253, 0, 1] == VarInt(256)
];
let deser_errorcases = vec![
vec![2, 255, 254, 255, 255, 255, 255, 255, 255, 255, 0], // .., 255, 254, .., 255] == VarInt(u64::MAX-1)
vec![1, 255, 255, 255, 255, 255, 255, 255, 255, 255], // .., 255, 255, .., 255] == VarInt(u64::MAX)
];
for testcase in testcases {
{
// test deserialization
let mut raw: Vec<u8> = [0u8; 32].to_vec();
raw.extend(testcase.0.clone());
let btr: BlockTransactionsRequest = deserialize(&raw.to_vec()).unwrap();
assert_eq!(testcase.1, btr.indexes);
}
{
// test serialization
let raw: Vec<u8> = serialize(&BlockTransactionsRequest {
block_hash: Hash::all_zeros(),
indexes: testcase.1,
});
let mut expected_raw: Vec<u8> = [0u8; 32].to_vec();
expected_raw.extend(testcase.0);
assert_eq!(expected_raw, raw);
}
}
for errorcase in deser_errorcases {
{
// test that we return Err() if deserialization fails (and don't panic)
let mut raw: Vec<u8> = [0u8; 32].to_vec();
raw.extend(errorcase);
assert!(deserialize::<BlockTransactionsRequest>(&raw.to_vec()).is_err());
}
}
}
#[test]
#[should_panic] // 'attempt to add with overflow' in consensus_encode()
fn test_getblocktx_panic_when_encoding_u64_max() {
serialize(&BlockTransactionsRequest {
block_hash: Hash::all_zeros(),
indexes: vec![core::u64::MAX],
});
}
}