subxt_core/tx/

mod.rs

// Copyright 2019-2024 Parity Technologies (UK) Ltd.
// This file is dual-licensed as Apache-2.0 or GPL-3.0.
// see LICENSE for license details.

//! Construct and sign transactions.
//!
//! # Example
//!
//! ```rust
//! use subxt_signer::sr25519::dev;
//! use subxt_macro::subxt;
//! use subxt_core::config::PolkadotConfig;
//! use subxt_core::config::DefaultExtrinsicParamsBuilder as Params;
//! use subxt_core::tx;
//! use subxt_core::utils::H256;
//! use subxt_core::metadata;
//!
//! // If we generate types without `subxt`, we need to point to `::subxt_core`:
//! #[subxt(
//!     crate = "::subxt_core",
//!     runtime_metadata_path = "../artifacts/polkadot_metadata_small.scale",
//! )]
//! pub mod polkadot {}
//!
//! // Gather some other information about the chain that we'll need to construct valid extrinsics:
//! let state = tx::ClientState::<PolkadotConfig> {
//!     metadata: {
//!         let metadata_bytes = include_bytes!("../../../artifacts/polkadot_metadata_small.scale");
//!         metadata::decode_from(&metadata_bytes[..]).unwrap()
//!     },
//!     genesis_hash: {
//!         let h = "91b171bb158e2d3848fa23a9f1c25182fb8e20313b2c1eb49219da7a70ce90c3";
//!         let bytes = hex::decode(h).unwrap();
//!         H256::from_slice(&bytes)
//!     },
//!     runtime_version: tx::RuntimeVersion {
//!         spec_version: 9370,
//!         transaction_version: 20,
//!     }
//! };
//!
//! // Now we can build a balance transfer extrinsic.
//! let dest = dev::bob().public_key().into();
//! let call = polkadot::tx().balances().transfer_allow_death(dest, 10_000);
//! let params = Params::new().tip(1_000).nonce(0).build();
//!
//! // We can validate that this lines up with the given metadata:
//! tx::validate(&call, &state.metadata).unwrap();
//!
//! // We can build a signed transaction:
//! let signed_call = tx::create_v4_signed(&call, &state, params)
//!     .unwrap()
//!     .sign(&dev::alice());
//!
//! // And log it:
//! println!("Tx: 0x{}", hex::encode(signed_call.encoded()));
//! ```

pub mod payload;
pub mod signer;

use crate::config::{Config, ExtrinsicParams, ExtrinsicParamsEncoder, Hasher};
use crate::error::{Error, ExtrinsicError, MetadataError};
use crate::metadata::Metadata;
use crate::utils::Encoded;
use alloc::borrow::{Cow, ToOwned};
use alloc::vec::Vec;
use codec::{Compact, Encode};
use payload::Payload;
use signer::Signer as SignerT;
use sp_crypto_hashing::blake2_256;

// Expose these here since we expect them in some calls below.
pub use crate::client::{ClientState, RuntimeVersion};

/// Run the validation logic against some extrinsic you'd like to submit. Returns `Ok(())`
/// if the call is valid (or if it's not possible to check since the call has no validation hash).
/// Return an error if the call was not valid or something went wrong trying to validate it (ie
/// the pallet or call in question do not exist at all).
pub fn validate<Call: Payload>(call: &Call, metadata: &Metadata) -> Result<(), Error> {
    if let Some(details) = call.validation_details() {
        let expected_hash = metadata
            .pallet_by_name_err(details.pallet_name)?
            .call_hash(details.call_name)
            .ok_or_else(|| MetadataError::CallNameNotFound(details.call_name.to_owned()))?;

        if details.hash != expected_hash {
            return Err(MetadataError::IncompatibleCodegen.into());
        }
    }
    Ok(())
}

/// Returns the suggested transaction versions to build for a given chain, or an error
/// if Subxt doesn't support any version expected by the chain.
///
/// If the result is [`TransactionVersion::V4`], use the `v4` methods in this module. If it's
/// [`TransactionVersion::V5`], use the `v5` ones.
pub fn suggested_version(metadata: &Metadata) -> Result<TransactionVersion, Error> {
    let versions = metadata.extrinsic().supported_versions();

    if versions.contains(&4) {
        Ok(TransactionVersion::V4)
    } else if versions.contains(&5) {
        Ok(TransactionVersion::V5)
    } else {
        Err(ExtrinsicError::UnsupportedVersion.into())
    }
}

/// The transaction versions supported by Subxt.
#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug)]
pub enum TransactionVersion {
    /// v4 transactions (signed and unsigned transactions)
    V4,
    /// v5 transactions (bare and general transactions)
    V5,
}

/// Return the SCALE encoded bytes representing the call data of the transaction.
pub fn call_data<Call: Payload>(call: &Call, metadata: &Metadata) -> Result<Vec<u8>, Error> {
    let mut bytes = Vec::new();
    call.encode_call_data_to(metadata, &mut bytes)?;
    Ok(bytes)
}

/// Creates a V4 "unsigned" transaction without submitting it.
pub fn create_v4_unsigned<T: Config, Call: Payload>(
    call: &Call,
    metadata: &Metadata,
) -> Result<Transaction<T>, Error> {
    create_unsigned_at_version(call, 4, metadata)
}

/// Creates a V5 "bare" transaction without submitting it.
pub fn create_v5_bare<T: Config, Call: Payload>(
    call: &Call,
    metadata: &Metadata,
) -> Result<Transaction<T>, Error> {
    create_unsigned_at_version(call, 5, metadata)
}

// Create a V4 "unsigned" transaction or V5 "bare" transaction.
fn create_unsigned_at_version<T: Config, Call: Payload>(
    call: &Call,
    tx_version: u8,
    metadata: &Metadata,
) -> Result<Transaction<T>, Error> {
    // 1. Validate this call against the current node metadata if the call comes
    // with a hash allowing us to do so.
    validate(call, metadata)?;

    // 2. Encode extrinsic
    let extrinsic = {
        let mut encoded_inner = Vec::new();
        // encode the transaction version first.
        tx_version.encode_to(&mut encoded_inner);
        // encode call data after this byte.
        call.encode_call_data_to(metadata, &mut encoded_inner)?;
        // now, prefix byte length:
        let len = Compact(
            u32::try_from(encoded_inner.len()).expect("extrinsic size expected to be <4GB"),
        );
        let mut encoded = Vec::new();
        len.encode_to(&mut encoded);
        encoded.extend(encoded_inner);
        encoded
    };

    // Wrap in Encoded to ensure that any more "encode" calls leave it in the right state.
    Ok(Transaction::from_bytes(extrinsic))
}

/// Construct a v4 extrinsic, ready to be signed.
pub fn create_v4_signed<T: Config, Call: Payload>(
    call: &Call,
    client_state: &ClientState<T>,
    params: <T::ExtrinsicParams as ExtrinsicParams<T>>::Params,
) -> Result<PartialTransactionV4<T>, Error> {
    // 1. Validate this call against the current node metadata if the call comes
    // with a hash allowing us to do so.
    validate(call, &client_state.metadata)?;

    // 2. SCALE encode call data to bytes (pallet u8, call u8, call params).
    let call_data = call_data(call, &client_state.metadata)?;

    // 3. Construct our custom additional/extra params.
    let additional_and_extra_params =
        <T::ExtrinsicParams as ExtrinsicParams<T>>::new(client_state, params)?;

    // Return these details, ready to construct a signed extrinsic from.
    Ok(PartialTransactionV4 {
        call_data,
        additional_and_extra_params,
    })
}

/// Construct a v5 "general" extrinsic, ready to be signed or emitted as is.
pub fn create_v5_general<T: Config, Call: Payload>(
    call: &Call,
    client_state: &ClientState<T>,
    params: <T::ExtrinsicParams as ExtrinsicParams<T>>::Params,
) -> Result<PartialTransactionV5<T>, Error> {
    // 1. Validate this call against the current node metadata if the call comes
    // with a hash allowing us to do so.
    validate(call, &client_state.metadata)?;

    // 2. Work out which TX extension version to target based on metadata (unless we
    // explicitly ask for a specific transaction version at a later step).
    let tx_extensions_version = client_state
        .metadata
        .extrinsic()
        .transaction_extensions_version();

    // 3. SCALE encode call data to bytes (pallet u8, call u8, call params).
    let call_data = call_data(call, &client_state.metadata)?;

    // 4. Construct our custom additional/extra params.
    let additional_and_extra_params =
        <T::ExtrinsicParams as ExtrinsicParams<T>>::new(client_state, params)?;

    // Return these details, ready to construct a signed extrinsic from.
    Ok(PartialTransactionV5 {
        call_data,
        additional_and_extra_params,
        tx_extensions_version,
    })
}

/// A partially constructed V4 extrinsic, ready to be signed.
pub struct PartialTransactionV4<T: Config> {
    call_data: Vec<u8>,
    additional_and_extra_params: T::ExtrinsicParams,
}

impl<T: Config> PartialTransactionV4<T> {
    /// Return the bytes representing the call data for this partially constructed
    /// extrinsic.
    pub fn call_data(&self) -> &[u8] {
        &self.call_data
    }

    // Obtain bytes representing the signer payload and run call some function
    // with them. This can avoid an allocation in some cases.
    fn with_signer_payload<F, R>(&self, f: F) -> R
    where
        F: for<'a> FnOnce(Cow<'a, [u8]>) -> R,
    {
        let mut bytes = self.call_data.clone();
        self.additional_and_extra_params
            .encode_signer_payload_value_to(&mut bytes);
        self.additional_and_extra_params
            .encode_implicit_to(&mut bytes);

        if bytes.len() > 256 {
            f(Cow::Borrowed(&blake2_256(&bytes)))
        } else {
            f(Cow::Owned(bytes))
        }
    }

    /// Return the V4 signer payload for this extrinsic. These are the bytes that must
    /// be signed in order to produce a valid signature for the extrinsic.
    pub fn signer_payload(&self) -> Vec<u8> {
        self.with_signer_payload(|bytes| bytes.to_vec())
    }

    /// Convert this [`PartialTransactionV4`] into a V4 signed [`Transaction`], ready to submit.
    /// The provided `signer` is responsible for providing the "from" address for the transaction,
    /// as well as providing a signature to attach to it.
    pub fn sign<Signer>(&self, signer: &Signer) -> Transaction<T>
    where
        Signer: SignerT<T>,
    {
        // Given our signer, we can sign the payload representing this extrinsic.
        let signature = self.with_signer_payload(|bytes| signer.sign(&bytes));
        // Now, use the signature and "from" address to build the extrinsic.
        self.sign_with_account_and_signature(signer.account_id(), &signature)
    }

    /// Convert this [`PartialTransactionV4`] into a V4 signed [`Transaction`], ready to submit.
    /// The provided `address` and `signature` will be used.
    pub fn sign_with_account_and_signature(
        &self,
        account_id: T::AccountId,
        signature: &T::Signature,
    ) -> Transaction<T> {
        let extrinsic = {
            let mut encoded_inner = Vec::new();
            // "is signed" + transaction protocol version (4)
            (0b10000000 + 4u8).encode_to(&mut encoded_inner);
            // from address for signature
            let address: T::Address = account_id.into();
            address.encode_to(&mut encoded_inner);
            // the signature
            signature.encode_to(&mut encoded_inner);
            // attach custom extra params
            self.additional_and_extra_params
                .encode_value_to(&mut encoded_inner);
            // and now, call data (remembering that it's been encoded already and just needs appending)
            encoded_inner.extend(&self.call_data);
            // now, prefix byte length:
            let len = Compact(
                u32::try_from(encoded_inner.len()).expect("extrinsic size expected to be <4GB"),
            );
            let mut encoded = Vec::new();
            len.encode_to(&mut encoded);
            encoded.extend(encoded_inner);
            encoded
        };

        // Return an extrinsic ready to be submitted.
        Transaction::from_bytes(extrinsic)
    }
}

/// A partially constructed V5 general extrinsic, ready to be signed or emitted as-is.
pub struct PartialTransactionV5<T: Config> {
    call_data: Vec<u8>,
    additional_and_extra_params: T::ExtrinsicParams,
    tx_extensions_version: u8,
}

impl<T: Config> PartialTransactionV5<T> {
    /// Return the bytes representing the call data for this partially constructed
    /// extrinsic.
    pub fn call_data(&self) -> &[u8] {
        &self.call_data
    }

    /// Return the V5 signer payload for this extrinsic. These are the bytes that must
    /// be signed in order to produce a valid signature for the extrinsic.
    pub fn signer_payload(&self) -> [u8; 32] {
        let mut bytes = self.call_data.clone();

        self.additional_and_extra_params
            .encode_signer_payload_value_to(&mut bytes);
        self.additional_and_extra_params
            .encode_implicit_to(&mut bytes);

        blake2_256(&bytes)
    }

    /// Convert this [`PartialTransactionV5`] into a V5 "general" [`Transaction`].
    ///
    /// This transaction has not been explicitly signed. Use [`Self::sign`]
    /// or [`Self::sign_with_account_and_signature`] if you wish to provide a
    /// signature (this is usually a necessary step).
    pub fn to_transaction(&self) -> Transaction<T> {
        let extrinsic = {
            let mut encoded_inner = Vec::new();
            // "is general" + transaction protocol version (5)
            (0b01000000 + 5u8).encode_to(&mut encoded_inner);
            // Encode versions for the transaction extensions
            self.tx_extensions_version.encode_to(&mut encoded_inner);
            // Encode the actual transaction extensions values
            self.additional_and_extra_params
                .encode_value_to(&mut encoded_inner);
            // and now, call data (remembering that it's been encoded already and just needs appending)
            encoded_inner.extend(&self.call_data);
            // now, prefix byte length:
            let len = Compact(
                u32::try_from(encoded_inner.len()).expect("extrinsic size expected to be <4GB"),
            );
            let mut encoded = Vec::new();
            len.encode_to(&mut encoded);
            encoded.extend(encoded_inner);
            encoded
        };

        // Return an extrinsic ready to be submitted.
        Transaction::from_bytes(extrinsic)
    }

    /// Convert this [`PartialTransactionV5`] into a V5 "general" [`Transaction`] with a signature.
    ///
    /// Signing the transaction injects the signature into the transaction extension data, which is why
    /// this method borrows self mutably. Signing repeatedly will override the previous signature.
    pub fn sign<Signer>(&mut self, signer: &Signer) -> Transaction<T>
    where
        Signer: SignerT<T>,
    {
        // Given our signer, we can sign the payload representing this extrinsic.
        let signature = signer.sign(&self.signer_payload());
        // Now, use the signature and "from" account to build the extrinsic.
        self.sign_with_account_and_signature(&signer.account_id(), &signature)
    }

    /// Convert this [`PartialTransactionV5`] into a V5 "general" [`Transaction`] with a signature.
    /// Prefer [`Self::sign`] if you have a [`SignerT`] instance to use.
    ///
    /// Signing the transaction injects the signature into the transaction extension data, which is why
    /// this method borrows self mutably. Signing repeatedly will override the previous signature.
    pub fn sign_with_account_and_signature(
        &mut self,
        account_id: &T::AccountId,
        signature: &T::Signature,
    ) -> Transaction<T> {
        // Inject the signature into the transaction extensions
        // before constructing it.
        self.additional_and_extra_params
            .inject_signature(account_id, signature);

        self.to_transaction()
    }
}

/// This represents a signed transaction that's ready to be submitted.
/// Use [`Transaction::encoded()`] or [`Transaction::into_encoded()`] to
/// get the bytes for it, or [`Transaction::hash()`] to get the hash.
pub struct Transaction<T> {
    encoded: Encoded,
    marker: core::marker::PhantomData<T>,
}

impl<T: Config> Transaction<T> {
    /// Create a [`Transaction`] from some already-signed and prepared
    /// extrinsic bytes,
    pub fn from_bytes(tx_bytes: Vec<u8>) -> Self {
        Self {
            encoded: Encoded(tx_bytes),
            marker: core::marker::PhantomData,
        }
    }

    /// Calculate and return the hash of the extrinsic, based on the configured hasher.
    pub fn hash(&self) -> T::Hash {
        T::Hasher::hash_of(&self.encoded)
    }

    /// Returns the SCALE encoded extrinsic bytes.
    pub fn encoded(&self) -> &[u8] {
        &self.encoded.0
    }

    /// Consumes this [`Transaction`] and returns the SCALE encoded
    /// extrinsic bytes.
    pub fn into_encoded(self) -> Vec<u8> {
        self.encoded.0
    }
}