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Use zcash_script’s new ZcashScript trait
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This is a precursor to testing the Rust implementation of Zcash Script.
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@sellout
sellout committed Aug 30, 2024
1 parent 0ef9987 commit 8449878
Showing 1 changed file with 32 additions and 118 deletions.
150 changes: 32 additions & 118 deletions zebra-script/src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -6,19 +6,12 @@
#![allow(unsafe_code)]

use core::fmt;
use std::{
ffi::{c_int, c_uint, c_void},
sync::Arc,
};
use std::sync::Arc;

use thiserror::Error;

use zcash_script::{
zcash_script_error_t, zcash_script_error_t_zcash_script_ERR_OK,
zcash_script_error_t_zcash_script_ERR_TX_DESERIALIZE,
zcash_script_error_t_zcash_script_ERR_TX_INDEX,
zcash_script_error_t_zcash_script_ERR_TX_SIZE_MISMATCH,
};
use zcash_script;
use zcash_script::ZcashScript;

use zebra_chain::{
parameters::ConsensusBranchId,
Expand All @@ -33,46 +26,35 @@ pub enum Error {
/// script verification failed
#[non_exhaustive]
ScriptInvalid,
/// could not deserialize tx
#[non_exhaustive]
TxDeserialize,
/// input index out of bounds
#[non_exhaustive]
TxIndex,
/// tx has an invalid size
#[non_exhaustive]
TxSizeMismatch,
/// tx is a coinbase transaction and should not be verified
#[non_exhaustive]
TxCoinbase,
/// unknown error from zcash_script: {0}
#[non_exhaustive]
Unknown(zcash_script_error_t),
Unknown(zcash_script::Error),
}

impl fmt::Display for Error {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.write_str(&match self {
Error::ScriptInvalid => "script verification failed".to_owned(),
Error::TxDeserialize => "could not deserialize tx".to_owned(),
Error::TxIndex => "input index out of bounds".to_owned(),
Error::TxSizeMismatch => "tx has an invalid size".to_owned(),
Error::TxCoinbase => {
"tx is a coinbase transaction and should not be verified".to_owned()
}
Error::Unknown(e) => format!("unknown error from zcash_script: {e}"),
Error::Unknown(e) => format!("unknown error from zcash_script: {:?}", e),
})
}
}

impl From<zcash_script_error_t> for Error {
impl From<zcash_script::Error> for Error {
#[allow(non_upper_case_globals)]
fn from(err_code: zcash_script_error_t) -> Error {
fn from(err_code: zcash_script::Error) -> Error {
match err_code {
zcash_script_error_t_zcash_script_ERR_OK => Error::ScriptInvalid,
zcash_script_error_t_zcash_script_ERR_TX_DESERIALIZE => Error::TxDeserialize,
zcash_script_error_t_zcash_script_ERR_TX_INDEX => Error::TxIndex,
zcash_script_error_t_zcash_script_ERR_TX_SIZE_MISMATCH => Error::TxSizeMismatch,
zcash_script::Error::Ok => Error::ScriptInvalid,
unknown => Error::Unknown(unknown),
}
}
Expand All @@ -92,41 +74,6 @@ pub struct CachedFfiTransaction {
all_previous_outputs: Vec<transparent::Output>,
}

/// A sighash context used for the zcash_script sighash callback.
struct SigHashContext<'a> {
/// The index of the input being verified.
input_index: usize,
/// The SigHasher for the transaction being verified.
sighasher: SigHasher<'a>,
}

/// The sighash callback to use with zcash_script.
extern "C" fn sighash(
sighash_out: *mut u8,
sighash_out_len: c_uint,
ctx: *const c_void,
script_code: *const u8,
script_code_len: c_uint,
hash_type: c_int,
) {
// SAFETY: `ctx` is a valid SigHashContext because it is always passed to
// `zcash_script_verify_callback` which simply forwards it to the callback.
// `script_code` and `sighash_out` are valid buffers since they are always
// specified when the callback is called.
unsafe {
let ctx = ctx as *const SigHashContext;
let script_code_vec =
std::slice::from_raw_parts(script_code, script_code_len as usize).to_vec();
let sighash = (*ctx).sighasher.sighash(
HashType::from_bits_truncate(hash_type as u32),
Some(((*ctx).input_index, script_code_vec)),
);
// Sanity check; must always be true.
assert_eq!(sighash_out_len, sighash.0.len() as c_uint);
std::ptr::copy_nonoverlapping(sighash.0.as_ptr(), sighash_out, sighash.0.len());
}
}

impl CachedFfiTransaction {
/// Construct a `PrecomputedTransaction` from a `Transaction` and the outputs
/// from previous transactions that match each input in the transaction
Expand Down Expand Up @@ -168,27 +115,11 @@ impl CachedFfiTransaction {
} = previous_output;
let script_pub_key: &[u8] = lock_script.as_raw_bytes();

// This conversion is useful on some platforms, but not others.
#[allow(clippy::useless_conversion)]
let n_in = input_index
.try_into()
.expect("transaction indexes are much less than c_uint::MAX");

let flags = zcash_script::zcash_script_SCRIPT_FLAGS_VERIFY_P2SH
| zcash_script::zcash_script_SCRIPT_FLAGS_VERIFY_CHECKLOCKTIMEVERIFY;
// This conversion is useful on some platforms, but not others.
#[allow(clippy::useless_conversion)]
let flags = flags
.try_into()
.expect("zcash_script_SCRIPT_FLAGS_VERIFY_* enum values fit in a c_uint");

let mut err = 0;
let flags = zcash_script::VerificationFlags::P2SH
| zcash_script::VerificationFlags::CHECKLOCKTIMEVERIFY;

let lock_time = self.transaction.raw_lock_time() as i64;
let is_final = if self.transaction.inputs()[input_index].sequence() == u32::MAX {
1
} else {
0
};
let is_final = self.transaction.inputs()[input_index].sequence() == u32::MAX;
let signature_script = match &self.transaction.inputs()[input_index] {
transparent::Input::PrevOut {
outpoint: _,
Expand All @@ -198,31 +129,26 @@ impl CachedFfiTransaction {
transparent::Input::Coinbase { .. } => Err(Error::TxCoinbase)?,
};

let ctx = Box::new(SigHashContext {
input_index: n_in,
sighasher: SigHasher::new(&self.transaction, branch_id, &self.all_previous_outputs),
});
// SAFETY: The `script_*` fields are created from a valid Rust `slice`.
let ret = unsafe {
zcash_script::zcash_script_verify_callback(
(&*ctx as *const SigHashContext) as *const c_void,
Some(sighash),
lock_time,
is_final,
script_pub_key.as_ptr(),
script_pub_key.len() as u32,
signature_script.as_ptr(),
signature_script.len() as u32,
flags,
&mut err,
let calculate_sighash = |script_code: &[u8], hash_type: zcash_script::HashType| {
let script_code_vec = script_code.to_vec();
Some(
SigHasher::new(&self.transaction, branch_id, &self.all_previous_outputs)
.sighash(
HashType::from_bits_truncate(hash_type.bits() as u32),
Some((input_index, script_code_vec)),
)
.0,
)
};

if ret == 1 {
Ok(())
} else {
Err(Error::from(err))
}
zcash_script::Cxx::verify_callback(
&calculate_sighash,
lock_time,
is_final,
script_pub_key,
signature_script,
flags,
)
.map_err(Error::from)
}

/// Returns the number of transparent signature operations in the
Expand All @@ -239,27 +165,15 @@ impl CachedFfiTransaction {
sequence: _,
} => {
let script = unlock_script.as_raw_bytes();
// SAFETY: `script` is created from a valid Rust `slice`.
unsafe {
zcash_script::zcash_script_legacy_sigop_count_script(
script.as_ptr(),
script.len() as u32,
)
}
zcash_script::Cxx::legacy_sigop_count_script(script).map_err(Error::from)?
}
transparent::Input::Coinbase { .. } => 0,
} as u64;
}

for output in self.transaction.outputs() {
let script = output.lock_script.as_raw_bytes();
// SAFETY: `script` is created from a valid Rust `slice`.
let ret = unsafe {
zcash_script::zcash_script_legacy_sigop_count_script(
script.as_ptr(),
script.len() as u32,
)
};
let ret = zcash_script::Cxx::legacy_sigop_count_script(script).map_err(Error::from)?;
count += ret as u64;
}
Ok(count)
Expand Down

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