interpreter.rs

use std::cmp;
use keys::{Public, Signature};
use hash::H256;
use transaction::{Transaction, SEQUENCE_LOCKTIME_DISABLE_FLAG};
use crypto::{sha1, sha256, dhash160, dhash256, ripemd160};
use script::{script, Script, Num, VerificationFlags, Opcode, Error, Instruction};

#[derive(Debug, PartialEq, Clone, Copy)]
#[repr(u8)]
pub enum SignatureHash {
	All = 1,
	None = 2,
	Single = 3,
	AnyoneCanPay = 0x80,
}

#[derive(Debug, PartialEq, Clone, Copy)]
pub enum SignatureVersion {
	Base,
	WitnessV0,
}

pub trait SignatureChecker {
	fn check_signature(
		&self,
		script_signature: &[u8],
		public: &Public,
		script: &Script,
		version: SignatureVersion
	) -> bool;

	fn check_lock_time(&self, lock_time: Num) -> bool;

	fn check_sequence(&self, sequence: Num) -> bool;
}

pub struct NoopSignatureChecker;

impl SignatureChecker for NoopSignatureChecker {
	fn check_signature(&self, _: &[u8], _: &Public, _: &Script, _: SignatureVersion) -> bool {
		false
	}

	fn check_lock_time(&self, _: Num) -> bool {
		false
	}

	fn check_sequence(&self, _: Num) -> bool {
		false
	}
}

pub struct TransactionSignatureChecker {
	transaction: Transaction,
	i: u32,
	amount: i64,
}

impl TransactionSignatureChecker {
	fn verify_signature(&self, _signature: &[u8], _public: &Public, _hash: &H256) -> bool {
		unimplemented!();
	}
}

impl SignatureChecker for TransactionSignatureChecker {
	fn check_signature(
		&self,
		_script_signature: &[u8],
		_public: &Public,
		_script: &Script,
		_version: SignatureVersion
	) -> bool {
		unimplemented!();
	}

	fn check_lock_time(&self, _lock_time: Num) -> bool {
		unimplemented!();
	}

	fn check_sequence(&self, _sequence: Num) -> bool {
		unimplemented!();
	}

}

fn is_public_key(v: &[u8]) -> bool {
	match v.len() {
		33 if v[0] == 2 || v[0] == 3 => true,
		65 if v[0] == 4 => true,
		_ => false,
	}
}

/// A canonical signature exists of: <30> <total len> <02> <len R> <R> <02> <len S> <S> <hashtype>
/// Where R and S are not negative (their first byte has its highest bit not set), and not
/// excessively padded (do not start with a 0 byte, unless an otherwise negative number follows,
/// in which case a single 0 byte is necessary and even required).
///
/// See https://bitcointalk.org/index.php?topic=8392.msg127623#msg127623
///
/// This function is consensus-critical since BIP66.
fn is_valid_signature_encoding(sig: &[u8]) -> bool {
	// Format: 0x30 [total-length] 0x02 [R-length] [R] 0x02 [S-length] [S] [sighash]
	// * total-length: 1-byte length descriptor of everything that follows,
	//   excluding the sighash byte.
	// * R-length: 1-byte length descriptor of the R value that follows.
	// * R: arbitrary-length big-endian encoded R value. It must use the shortest
	//   possible encoding for a positive integers (which means no null bytes at
	//   the start, except a single one when the next byte has its highest bit set).
	// * S-length: 1-byte length descriptor of the S value that follows.
	// * S: arbitrary-length big-endian encoded S value. The same rules apply.
	// * sighash: 1-byte value indicating what data is hashed (not part of the DER
	//   signature)

	// Minimum and maximum size constraints
	if sig.len() < 9 || sig.len() > 73 {
		return false;
	}

	// A signature is of type 0x30 (compound)
	if sig[0] != 0x30 {
		return false;
	}

	// Make sure the length covers the entire signature.
	if sig[1] as usize != sig.len() - 3 {
		return false;
	}

	// Extract the length of the R element.
	let len_r = sig[3] as usize;

	// Make sure the length of the S element is still inside the signature.
	if len_r + 5 >= sig.len() {
		return false;
	}

	// Extract the length of the S element.
	let len_s = sig[len_r + 5] as usize;

	// Verify that the length of the signature matches the sum of the length
	if len_r + len_s + 7 != sig.len() {
		return false;
	}

	// Check whether the R element is an integer.
	if sig[2] != 2 {
		return false;
	}

	// Zero-length integers are not allowed for R.
	if len_r == 0 {
		return false;
	}

	// Negative numbers are not allowed for R.
	if (sig[4] & 0x80) != 0 {
		return false;
	}

	// Null bytes at the start of R are not allowed, unless R would
	// otherwise be interpreted as a negative number.
	if len_r > 1 && sig[4] == 0 && (!(sig[5] & 0x80)) != 0 {
		return false;
	}

	// Check whether the S element is an integer.
	if sig[len_r + 4] != 2 {
		return false;
	}

	// Zero-length integers are not allowed for S.
	if len_s == 0 {
		return false;
	}

	// Negative numbers are not allowed for S.
	if (sig[len_r + 6] & 0x80) != 0 {
		return false;
	}

	// Null bytes at the start of S are not allowed, unless S would otherwise be
	// interpreted as a negative number.
	if len_s > 1 && (sig[len_r + 6] == 0) && (!(sig[len_r + 7] & 0x80)) != 0 {
		return false;
	}

	true
}

fn is_low_der_signature(sig: &[u8]) -> Result<bool, Error> {
	if !is_valid_signature_encoding(sig) {
		return Err(Error::SignatureDer);
	}

	let signature: Signature = sig.into();
	if !signature.check_low_s() {
		return Err(Error::SignatureHighS);
	}