zebra_consensus/
script.rs

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1use std::{future::Future, pin::Pin, sync::Arc};
2
3use tracing::Instrument;
4
5use zebra_chain::{parameters::NetworkUpgrade, transparent};
6use zebra_script::CachedFfiTransaction;
7
8use crate::BoxError;
9
10/// Asynchronous script verification.
11///
12/// The verifier asynchronously requests the UTXO a transaction attempts
13/// to use as an input, and verifies the script as soon as it becomes
14/// available.  This allows script verification to be performed
15/// asynchronously, rather than requiring that the entire chain up to
16/// the previous block is ready.
17///
18/// The asynchronous script verification design is documented in [RFC4].
19///
20/// [RFC4]: https://zebra.zfnd.org/dev/rfcs/0004-asynchronous-script-verification.html
21#[derive(Debug, Clone, Default, Copy, PartialEq, Eq)]
22pub struct Verifier;
23
24/// A script verification request.
25#[derive(Debug)]
26pub struct Request {
27    /// A cached transaction, in the format required by the script verifier FFI interface.
28    pub cached_ffi_transaction: Arc<CachedFfiTransaction>,
29    /// The index of an input in `cached_ffi_transaction`, used for verifying this request
30    ///
31    /// Coinbase inputs are rejected by the script verifier, because they do not spend a UTXO.
32    pub input_index: usize,
33    /// The network upgrade active in the context of this verification request.
34    ///
35    /// Because the consensus branch ID changes with each network upgrade,
36    /// it has to be specified on a per-request basis.
37    pub upgrade: NetworkUpgrade,
38}
39
40impl tower::Service<Request> for Verifier {
41    type Response = ();
42    type Error = BoxError;
43    type Future =
44        Pin<Box<dyn Future<Output = Result<Self::Response, Self::Error>> + Send + 'static>>;
45
46    fn poll_ready(
47        &mut self,
48        _cx: &mut std::task::Context<'_>,
49    ) -> std::task::Poll<Result<(), Self::Error>> {
50        std::task::Poll::Ready(Ok(()))
51    }
52
53    fn call(&mut self, req: Request) -> Self::Future {
54        use futures_util::FutureExt;
55
56        let Request {
57            cached_ffi_transaction,
58            input_index,
59            upgrade,
60        } = req;
61        let input = &cached_ffi_transaction.inputs()[input_index];
62        match input {
63            transparent::Input::PrevOut { outpoint, .. } => {
64                let outpoint = *outpoint;
65
66                // Avoid calling the state service if the utxo is already known
67                let span = tracing::trace_span!("script", ?outpoint);
68
69                async move {
70                    cached_ffi_transaction.is_valid(upgrade, input_index)?;
71                    tracing::trace!("script verification succeeded");
72
73                    Ok(())
74                }
75                .instrument(span)
76                .boxed()
77            }
78            transparent::Input::Coinbase { .. } => {
79                async { Err("unexpected coinbase input".into()) }.boxed()
80            }
81        }
82    }
83}
zebra_consensus/script.rs

zebra_consensus/
script.rs
