// Written in 2014 by Andrew Poelstra // SPDX-License-Identifier: CC0-1.0 //! Bitcoin blocks. //! //! A block is a bundle of transactions with a proof-of-work attached, //! which commits to an earlier block to form the blockchain. This //! module describes structures and functions needed to describe //! these blocks and the blockchain. //! use crate::prelude::*; use core::fmt; use crate::util; use crate::util::Error::{BlockBadTarget, BlockBadProofOfWork}; use crate::merkle_tree::bitcoin_merkle_root; use crate::hashes::{Hash, HashEngine}; use crate::hash_types::{Wtxid, BlockHash, TxMerkleNode, WitnessMerkleNode, WitnessCommitment}; use crate::consensus::{encode, Encodable, Decodable}; use crate::blockdata::transaction::Transaction; use crate::blockdata::constants::WITNESS_SCALE_FACTOR; use crate::blockdata::script; use crate::pow::{CompactTarget, Target, Work}; use crate::VarInt; use crate::internal_macros::impl_consensus_encoding; use crate::io; /// Bitcoin block header. /// /// Contains all the block's information except the actual transactions, but /// including a root of a [merkle tree] commiting to all transactions in the block. /// /// [merkle tree]: https://en.wikipedia.org/wiki/Merkle_tree /// /// ### Bitcoin Core References /// /// * [CBlockHeader definition](https://github.com/bitcoin/bitcoin/blob/345457b542b6a980ccfbc868af0970a6f91d1b82/src/primitives/block.h#L20) #[derive(Copy, PartialEq, Eq, Clone, Debug, PartialOrd, Ord, Hash)] #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))] #[cfg_attr(feature = "serde", serde(crate = "actual_serde"))] pub struct BlockHeader { /// Block version, now repurposed for soft fork signalling. pub version: BlockVersion, /// Reference to the previous block in the chain. pub prev_blockhash: BlockHash, /// The root hash of the merkle tree of transactions in the block. pub merkle_root: TxMerkleNode, /// The timestamp of the block, as claimed by the miner. pub time: u32, /// The target value below which the blockhash must lie. pub bits: CompactTarget, /// The nonce, selected to obtain a low enough blockhash. pub nonce: u32, } impl_consensus_encoding!(BlockHeader, version, prev_blockhash, merkle_root, time, bits, nonce); impl BlockHeader { /// Returns the block hash. pub fn block_hash(&self) -> BlockHash { let mut engine = BlockHash::engine(); self.consensus_encode(&mut engine).expect("engines don't error"); BlockHash::from_engine(engine) } /// Computes the target (range [0, T] inclusive) that a blockhash must land in to be valid. pub fn target(&self) -> Target { self.bits.into() } /// Computes the popular "difficulty" measure for mining. pub fn difficulty(&self) -> u128 { self.target().difficulty() } /// Checks that the proof-of-work for the block is valid, returning the block hash. pub fn validate_pow(&self, required_target: Target) -> Result { let target = self.target(); if target != required_target { return Err(BlockBadTarget); } let block_hash = self.block_hash(); if target.is_met_by(block_hash) { Ok(block_hash) } else { Err(BlockBadProofOfWork) } } /// Returns the total work of the block. pub fn work(&self) -> Work { self.target().to_work() } } /// Bitcoin block version number /// /// Originally used as a protocol version, but repurposed for soft-fork signaling. /// /// The inner value is a signed integer in Bitcoin Core for historical reasons, if version bits is /// being used the top three bits must be 001, this gives us a useful range of [0x20000000...0x3FFFFFFF]. /// /// > When a block nVersion does not have top bits 001, it is treated as if all bits are 0 for the purposes of deployments. /// /// ### Relevant BIPs /// /// * [BIP9 - Version bits with timeout and delay](https://github.com/bitcoin/bips/blob/master/bip-0009.mediawiki) (current usage) /// * [BIP34 - Block v2, Height in Coinbase](https://github.com/bitcoin/bips/blob/master/bip-0034.mediawiki) #[derive(Copy, PartialEq, Eq, Clone, Debug, PartialOrd, Ord, Hash)] #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))] #[cfg_attr(feature = "serde", serde(crate = "actual_serde"))] pub struct BlockVersion(pub i32); impl BlockVersion { /// BIP-9 compatible version number that does not signal for any softforks. pub const NO_SOFT_FORK_SIGNALLING: Self = Self(Self::USE_VERSION_BITS as i32); /// BIP-9 soft fork signal bits mask. const VERSION_BITS_MASK: u32 = 0x1FFF_FFFF; /// 32bit value starting with `001` to use version bits. /// /// The value has the top three bits `001` which enables the use of version bits to signal for soft forks. const USE_VERSION_BITS: u32 = 0x2000_0000; /// Check whether the version number is signalling a soft fork at the given bit. /// /// A block is signalling for a soft fork under BIP-9 if the first 3 bits are `001` and /// the version bit for the specific soft fork is toggled on. pub fn is_signalling_soft_fork(&self, bit: u8) -> bool { // Only bits [0, 28] inclusive are used for signalling. if bit > 28 { return false; } // To signal using version bits, the first three bits must be `001`. if (self.0 as u32) & !Self::VERSION_BITS_MASK != Self::USE_VERSION_BITS { return false; } // The bit is set if signalling a soft fork. (self.0 as u32 & Self::VERSION_BITS_MASK) & (1 << bit) > 0 } } impl Default for BlockVersion { fn default() -> BlockVersion { Self::NO_SOFT_FORK_SIGNALLING } } impl Encodable for BlockVersion { fn consensus_encode(&self, w: &mut W) -> Result { self.0.consensus_encode(w) } } impl Decodable for BlockVersion { fn consensus_decode(r: &mut R) -> Result { Decodable::consensus_decode(r).map(BlockVersion) } } /// Bitcoin block. /// /// A collection of transactions with an attached proof of work. /// /// See [Bitcoin Wiki: Block][wiki-block] for more information. /// /// [wiki-block]: https://en.bitcoin.it/wiki/Block /// /// ### Bitcoin Core References /// /// * [CBlock definition](https://github.com/bitcoin/bitcoin/blob/345457b542b6a980ccfbc868af0970a6f91d1b82/src/primitives/block.h#L62) #[derive(PartialEq, Eq, Clone, Debug)] #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))] #[cfg_attr(feature = "serde", serde(crate = "actual_serde"))] pub struct Block { /// The block header pub header: BlockHeader, /// List of transactions contained in the block pub txdata: Vec } impl_consensus_encoding!(Block, header, txdata); impl Block { /// Returns the block hash. pub fn block_hash(&self) -> BlockHash { self.header.block_hash() } /// check if merkle root of header matches merkle root of the transaction list pub fn check_merkle_root(&self) -> bool { match self.compute_merkle_root() { Some(merkle_root) => self.header.merkle_root == merkle_root, None => false, } } /// Checks if witness commitment in coinbase matches the transaction list. pub fn check_witness_commitment(&self) -> bool { const MAGIC: [u8; 6] = [0x6a, 0x24, 0xaa, 0x21, 0xa9, 0xed]; // Witness commitment is optional if there are no transactions using SegWit in the block. if self.txdata.iter().all(|t| t.input.iter().all(|i| i.witness.is_empty())) { return true; } if self.txdata.is_empty() { return false; } let coinbase = &self.txdata[0]; if !coinbase.is_coin_base() { return false; } // Commitment is in the last output that starts with magic bytes. if let Some(pos) = coinbase.output.iter() .rposition(|o| o.script_pubkey.len () >= 38 && o.script_pubkey[0..6] == MAGIC) { let commitment = WitnessCommitment::from_slice(&coinbase.output[pos].script_pubkey.as_bytes()[6..38]).unwrap(); // Witness reserved value is in coinbase input witness. let witness_vec: Vec<_> = coinbase.input[0].witness.iter().collect(); if witness_vec.len() == 1 && witness_vec[0].len() == 32 { if let Some(witness_root) = self.witness_root() { return commitment == Self::compute_witness_commitment(&witness_root, witness_vec[0]); } } } false } /// Computes the transaction merkle root. pub fn compute_merkle_root(&self) -> Option { let hashes = self.txdata.iter().map(|obj| obj.txid().as_hash()); bitcoin_merkle_root(hashes).map(|h| h.into()) } /// Computes the witness commitment for the block's transaction list. pub fn compute_witness_commitment(witness_root: &WitnessMerkleNode, witness_reserved_value: &[u8]) -> WitnessCommitment { let mut encoder = WitnessCommitment::engine(); witness_root.consensus_encode(&mut encoder).expect("engines don't error"); encoder.input(witness_reserved_value); WitnessCommitment::from_engine(encoder) } /// Computes the merkle root of transactions hashed for witness. pub fn witness_root(&self) -> Option { let hashes = self.txdata.iter().enumerate().map(|(i, t)| { if i == 0 { // Replace the first hash with zeroes. Wtxid::all_zeros().as_hash() } else { t.wtxid().as_hash() } }); bitcoin_merkle_root(hashes).map(|h| h.into()) } /// base_size == size of header + size of encoded transaction count. fn base_size(&self) -> usize { 80 + VarInt(self.txdata.len() as u64).len() } /// Returns the size of the block. /// /// size == size of header + size of encoded transaction count + total size of transactions. pub fn size(&self) -> usize { let txs_size: usize = self.txdata.iter().map(Transaction::size).sum(); self.base_size() + txs_size } /// Returns the strippedsize of the block. pub fn strippedsize(&self) -> usize { let txs_size: usize = self.txdata.iter().map(Transaction::strippedsize).sum(); self.base_size() + txs_size } /// Returns the weight of the block. pub fn weight(&self) -> usize { let base_weight = WITNESS_SCALE_FACTOR * self.base_size(); let txs_weight: usize = self.txdata.iter().map(Transaction::weight).sum(); base_weight + txs_weight } /// Returns the coinbase transaction, if one is present. pub fn coinbase(&self) -> Option<&Transaction> { self.txdata.first() } /// Returns the block height, as encoded in the coinbase transaction according to BIP34. pub fn bip34_block_height(&self) -> Result { // Citing the spec: // Add height as the first item in the coinbase transaction's scriptSig, // and increase block version to 2. The format of the height is // "minimally encoded serialized CScript"" -- first byte is number of bytes in the number // (will be 0x03 on main net for the next 150 or so years with 2^23-1 // blocks), following bytes are little-endian representation of the // number (including a sign bit). Height is the height of the mined // block in the block chain, where the genesis block is height zero (0). if self.header.version < BlockVersion(2) { return Err(Bip34Error::Unsupported); } let cb = self.coinbase().ok_or(Bip34Error::NotPresent)?; let input = cb.input.first().ok_or(Bip34Error::NotPresent)?; let push = input.script_sig.instructions_minimal().next().ok_or(Bip34Error::NotPresent)?; match push.map_err(|_| Bip34Error::NotPresent)? { script::Instruction::PushBytes(b) => { // Check that the number is encoded in the minimal way. let h = script::read_scriptint(b).map_err(|_e| Bip34Error::UnexpectedPush(b.to_vec()))?; if h < 0 { Err(Bip34Error::NegativeHeight) } else { Ok(h as u64) } } _ => Err(Bip34Error::NotPresent), } } } /// An error when looking up a BIP34 block height. #[derive(Debug, Clone, PartialEq, Eq)] #[non_exhaustive] pub enum Bip34Error { /// The block does not support BIP34 yet. Unsupported, /// No push was present where the BIP34 push was expected. NotPresent, /// The BIP34 push was larger than 8 bytes. UnexpectedPush(Vec), /// The BIP34 push was negative. NegativeHeight, } impl fmt::Display for Bip34Error { fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { match *self { Bip34Error::Unsupported => write!(f, "block doesn't support BIP34"), Bip34Error::NotPresent => write!(f, "BIP34 push not present in block's coinbase"), Bip34Error::UnexpectedPush(ref p) => { write!(f, "unexpected byte push of > 8 bytes: {:?}", p) } Bip34Error::NegativeHeight => write!(f, "negative BIP34 height"), } } } #[cfg(feature = "std")] #[cfg_attr(docsrs, doc(cfg(feature = "std")))] impl std::error::Error for Bip34Error { fn source(&self) -> Option<&(dyn std::error::Error + 'static)> { use self::Bip34Error::*; match self { Unsupported | NotPresent | UnexpectedPush(_) | NegativeHeight => None, } } } impl From for BlockHash { fn from(header: BlockHeader) -> BlockHash { header.block_hash() } } impl From<&BlockHeader> for BlockHash { fn from(header: &BlockHeader) -> BlockHash { header.block_hash() } } impl From for BlockHash { fn from(block: Block) -> BlockHash { block.block_hash() } } impl From<&Block> for BlockHash { fn from(block: &Block) -> BlockHash { block.block_hash() } } #[cfg(test)] mod tests { use super::*; use crate::hashes::hex::FromHex; use crate::blockdata::block::{Block, BlockHeader, BlockVersion}; use crate::consensus::encode::{deserialize, serialize}; use crate::util::Error::{BlockBadTarget, BlockBadProofOfWork}; #[test] fn test_coinbase_and_bip34() { // testnet block 100,000 let block_hex = "0200000035ab154183570282ce9afc0b494c9fc6a3cfea05aa8c1add2ecc56490000000038ba3d78e4500a5a7570dbe61960398add4410d278b21cd9708e6d9743f374d544fc055227f1001c29c1ea3b0101000000010000000000000000000000000000000000000000000000000000000000000000ffffffff3703a08601000427f1001c046a510100522cfabe6d6d0000000000000000000068692066726f6d20706f6f6c7365727665726aac1eeeed88ffffffff0100f2052a010000001976a914912e2b234f941f30b18afbb4fa46171214bf66c888ac00000000"; let block: Block = deserialize(&Vec::::from_hex(block_hex).unwrap()).unwrap(); let cb_txid = "d574f343976d8e70d91cb278d21044dd8a396019e6db70755a0a50e4783dba38"; assert_eq!(block.coinbase().unwrap().txid().to_string(), cb_txid); assert_eq!(block.bip34_block_height(), Ok(100_000)); // block with 9-byte bip34 push let bad_hex = "0200000035ab154183570282ce9afc0b494c9fc6a3cfea05aa8c1add2ecc56490000000038ba3d78e4500a5a7570dbe61960398add4410d278b21cd9708e6d9743f374d544fc055227f1001c29c1ea3b0101000000010000000000000000000000000000000000000000000000000000000000000000ffffffff3d09a08601112233445566000427f1001c046a510100522cfabe6d6d0000000000000000000068692066726f6d20706f6f6c7365727665726aac1eeeed88ffffffff0100f2052a010000001976a914912e2b234f941f30b18afbb4fa46171214bf66c888ac00000000"; let bad: Block = deserialize(&Vec::::from_hex(bad_hex).unwrap()).unwrap(); let push = Vec::::from_hex("a08601112233445566").unwrap(); assert_eq!(bad.bip34_block_height(), Err(super::Bip34Error::UnexpectedPush(push))); } #[test] fn block_test() { // Mainnet block 00000000b0c5a240b2a61d2e75692224efd4cbecdf6eaf4cc2cf477ca7c270e7 let some_block = Vec::from_hex("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").unwrap(); let cutoff_block = Vec::from_hex("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").unwrap(); let prevhash = Vec::from_hex("4ddccd549d28f385ab457e98d1b11ce80bfea2c5ab93015ade4973e400000000").unwrap(); let merkle = Vec::from_hex("bf4473e53794beae34e64fccc471dace6ae544180816f89591894e0f417a914c").unwrap(); let work = Work::from(0x100010001_u128); let decode: Result = deserialize(&some_block); let bad_decode: Result = deserialize(&cutoff_block); assert!(decode.is_ok()); assert!(bad_decode.is_err()); let real_decode = decode.unwrap(); assert_eq!(real_decode.header.version, BlockVersion(1)); assert_eq!(serialize(&real_decode.header.prev_blockhash), prevhash); assert_eq!(real_decode.header.merkle_root, real_decode.compute_merkle_root().unwrap()); assert_eq!(serialize(&real_decode.header.merkle_root), merkle); assert_eq!(real_decode.header.time, 1231965655); assert_eq!(real_decode.header.bits, CompactTarget::from_consensus(486604799)); assert_eq!(real_decode.header.nonce, 2067413810); assert_eq!(real_decode.header.work(), work); assert_eq!(real_decode.header.validate_pow(real_decode.header.target()).unwrap(), real_decode.block_hash()); assert_eq!(real_decode.header.difficulty(), 1); // [test] TODO: check the transaction data assert_eq!(real_decode.size(), some_block.len()); assert_eq!(real_decode.strippedsize(), some_block.len()); assert_eq!(real_decode.weight(), some_block.len() * 4); // should be also ok for a non-witness block as commitment is optional in that case assert!(real_decode.check_witness_commitment()); assert_eq!(serialize(&real_decode), some_block); } // Check testnet block 000000000000045e0b1660b6445b5e5c5ab63c9a4f956be7e1e69be04fa4497b #[test] fn segwit_block_test() { let segwit_block = include_bytes!("../../tests/data/testnet_block_000000000000045e0b1660b6445b5e5c5ab63c9a4f956be7e1e69be04fa4497b.raw").to_vec(); let decode: Result = deserialize(&segwit_block); let prevhash = Vec::from_hex("2aa2f2ca794ccbd40c16e2f3333f6b8b683f9e7179b2c4d74906000000000000").unwrap(); let merkle = Vec::from_hex("10bc26e70a2f672ad420a6153dd0c28b40a6002c55531bfc99bf8994a8e8f67e").unwrap(); let work = Work::from(0x257c3becdacc64_u64); assert!(decode.is_ok()); let real_decode = decode.unwrap(); assert_eq!(real_decode.header.version, BlockVersion(BlockVersion::USE_VERSION_BITS as i32)); // VERSIONBITS but no bits set assert_eq!(serialize(&real_decode.header.prev_blockhash), prevhash); assert_eq!(serialize(&real_decode.header.merkle_root), merkle); assert_eq!(real_decode.header.merkle_root, real_decode.compute_merkle_root().unwrap()); assert_eq!(real_decode.header.time, 1472004949); assert_eq!(real_decode.header.bits, CompactTarget::from_consensus(0x1a06d450)); assert_eq!(real_decode.header.nonce, 1879759182); assert_eq!(real_decode.header.work(), work); assert_eq!(real_decode.header.validate_pow(real_decode.header.target()).unwrap(), real_decode.block_hash()); assert_eq!(real_decode.header.difficulty(), 2456598); // [test] TODO: check the transaction data assert_eq!(real_decode.size(), segwit_block.len()); assert_eq!(real_decode.strippedsize(), 4283); assert_eq!(real_decode.weight(), 17168); assert!(real_decode.check_witness_commitment()); assert_eq!(serialize(&real_decode), segwit_block); } #[test] fn block_version_test() { let block = Vec::from_hex("ffffff7f0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000").unwrap(); let decode: Result = deserialize(&block); assert!(decode.is_ok()); let real_decode = decode.unwrap(); assert_eq!(real_decode.header.version, BlockVersion(2147483647)); let block2 = Vec::from_hex("000000800000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000").unwrap(); let decode2: Result = deserialize(&block2); assert!(decode2.is_ok()); let real_decode2 = decode2.unwrap(); assert_eq!(real_decode2.header.version, BlockVersion(-2147483648)); } #[test] fn validate_pow_test() { let some_header = Vec::from_hex("010000004ddccd549d28f385ab457e98d1b11ce80bfea2c5ab93015ade4973e400000000bf4473e53794beae34e64fccc471dace6ae544180816f89591894e0f417a914cd74d6e49ffff001d323b3a7b").unwrap(); let some_header: BlockHeader = deserialize(&some_header).expect("Can't deserialize correct block header"); assert_eq!(some_header.validate_pow(some_header.target()).unwrap(), some_header.block_hash()); // test with zero target match some_header.validate_pow(Target::ZERO) { Err(BlockBadTarget) => (), _ => panic!("unexpected result from validate_pow"), } // test with modified header let mut invalid_header: BlockHeader = some_header; invalid_header.version.0 += 1; match invalid_header.validate_pow(invalid_header.target()) { Err(BlockBadProofOfWork) => (), _ => panic!("unexpected result from validate_pow"), } } #[test] fn compact_roundrtip_test() { let some_header = Vec::from_hex("010000004ddccd549d28f385ab457e98d1b11ce80bfea2c5ab93015ade4973e400000000bf4473e53794beae34e64fccc471dace6ae544180816f89591894e0f417a914cd74d6e49ffff001d323b3a7b").unwrap(); let header: BlockHeader = deserialize(&some_header).expect("Can't deserialize correct block header"); assert_eq!(header.bits, header.target().to_compact_lossy()); } #[test] fn soft_fork_signalling() { for i in 0..31 { let version_int = (0x20000000u32 ^ 1<