miden_protocol/transaction/kernel/

mod.rs

use alloc::sync::Arc;
use alloc::vec::Vec;

use miden_core_lib::CoreLibrary;

use crate::account::{AccountHeader, AccountId};
#[cfg(any(feature = "testing", test))]
use crate::assembly::Library;
use crate::assembly::debuginfo::SourceManagerSync;
use crate::assembly::{Assembler, DefaultSourceManager, KernelLibrary};
use crate::asset::FungibleAsset;
use crate::block::BlockNumber;
use crate::crypto::SequentialCommit;
use crate::errors::TransactionOutputError;
use crate::protocol::ProtocolLib;
use crate::transaction::{RawOutputNote, RawOutputNotes, TransactionInputs, TransactionOutputs};
use crate::utils::serde::Deserializable;
use crate::utils::sync::LazyLock;
use crate::vm::{AdviceInputs, Program, ProgramInfo, StackInputs, StackOutputs};
use crate::{Felt, Hasher, Word};

mod procedures {
    include!(concat!(env!("OUT_DIR"), "/procedures.rs"));
}

pub mod memory;

mod advice_inputs;
mod tx_event_id;

pub use advice_inputs::TransactionAdviceInputs;
pub use tx_event_id::TransactionEventId;

// CONSTANTS
// ================================================================================================

// Initialize the kernel library only once
static KERNEL_LIB: LazyLock<KernelLibrary> = LazyLock::new(|| {
    let kernel_lib_bytes =
        include_bytes!(concat!(env!("OUT_DIR"), "/assets/kernels/tx_kernel.masl"));
    KernelLibrary::read_from_bytes(kernel_lib_bytes)
        .expect("failed to deserialize transaction kernel library")
});

// Initialize the kernel main program only once
static KERNEL_MAIN: LazyLock<Program> = LazyLock::new(|| {
    let kernel_main_bytes =
        include_bytes!(concat!(env!("OUT_DIR"), "/assets/kernels/tx_kernel.masb"));
    Program::read_from_bytes(kernel_main_bytes)
        .expect("failed to deserialize transaction kernel runtime")
});

// Initialize the transaction script executor program only once
static TX_SCRIPT_MAIN: LazyLock<Program> = LazyLock::new(|| {
    let tx_script_main_bytes =
        include_bytes!(concat!(env!("OUT_DIR"), "/assets/kernels/tx_script_main.masb"));
    Program::read_from_bytes(tx_script_main_bytes)
        .expect("failed to deserialize tx script executor runtime")
});

// TRANSACTION KERNEL
// ================================================================================================

pub struct TransactionKernel;

impl TransactionKernel {
    // CONSTANTS
    // --------------------------------------------------------------------------------------------

    /// Array of kernel procedures.
    pub const PROCEDURES: &'static [Word] = &procedures::KERNEL_PROCEDURES;

    // KERNEL SOURCE CODE
    // --------------------------------------------------------------------------------------------

    /// Returns a library with the transaction kernel system procedures.
    ///
    /// # Panics
    /// Panics if the transaction kernel source is not well-formed.
    pub fn kernel() -> KernelLibrary {
        KERNEL_LIB.clone()
    }

    /// Returns an AST of the transaction kernel executable program.
    ///
    /// # Panics
    /// Panics if the transaction kernel source is not well-formed.
    pub fn main() -> Program {
        KERNEL_MAIN.clone()
    }

    /// Returns an AST of the transaction script executor program.
    ///
    /// # Panics
    /// Panics if the transaction kernel source is not well-formed.
    pub fn tx_script_main() -> Program {
        TX_SCRIPT_MAIN.clone()
    }

    /// Returns [ProgramInfo] for the transaction kernel executable program.
    ///
    /// # Panics
    /// Panics if the transaction kernel source is not well-formed.
    pub fn program_info() -> ProgramInfo {
        // TODO: make static
        let program_hash = Self::main().hash();
        let kernel = Self::kernel().kernel().clone();

        ProgramInfo::new(program_hash, kernel)
    }

    /// Transforms the provided [`TransactionInputs`] into stack and advice
    /// inputs needed to execute a transaction kernel for a specific transaction.
    pub fn prepare_inputs(tx_inputs: &TransactionInputs) -> (StackInputs, TransactionAdviceInputs) {
        let account = tx_inputs.account();

        let stack_inputs = TransactionKernel::build_input_stack(
            account.id(),
            account.initial_commitment(),
            tx_inputs.input_notes().commitment(),
            tx_inputs.block_header().commitment(),
            tx_inputs.block_header().block_num(),
        );

        let tx_advice_inputs = TransactionAdviceInputs::new(tx_inputs);

        (stack_inputs, tx_advice_inputs)
    }

    // ASSEMBLER CONSTRUCTOR
    // --------------------------------------------------------------------------------------------

    /// Returns a new Miden assembler instantiated with the transaction kernel and loaded with the
    /// core lib as well as with miden-lib.
    pub fn assembler() -> Assembler {
        Self::assembler_with_source_manager(Arc::new(DefaultSourceManager::default()))
    }

    /// Returns a new assembler instantiated with the transaction kernel and loaded with the
    /// core lib as well as with miden-lib.
    pub fn assembler_with_source_manager(source_manager: Arc<dyn SourceManagerSync>) -> Assembler {
        #[cfg(all(any(feature = "testing", test), feature = "std"))]
        source_manager_ext::load_masm_source_files(&source_manager);

        Assembler::with_kernel(source_manager, Self::kernel())
            .with_dynamic_library(CoreLibrary::default())
            .expect("failed to load std-lib")
            .with_dynamic_library(ProtocolLib::default())
            .expect("failed to load miden-lib")
    }

    // STACK INPUTS / OUTPUTS
    // --------------------------------------------------------------------------------------------

    /// Returns the stack with the public inputs required by the transaction kernel.
    ///
    /// The initial stack is defined:
    ///
    /// ```text
    /// [
    ///     BLOCK_COMMITMENT,
    ///     INITIAL_ACCOUNT_COMMITMENT,
    ///     INPUT_NOTES_COMMITMENT,
    ///     account_id_suffix, account_id_prefix, block_num
    /// ]
    /// ```
    ///
    /// Where:
    /// - BLOCK_COMMITMENT is the commitment to the reference block of the transaction.
    /// - block_num is the reference block number.
    /// - account_id_{prefix,suffix} are the prefix and suffix felts of the account that the
    ///   transaction is being executed against.
    /// - INITIAL_ACCOUNT_COMMITMENT is the account state prior to the transaction, EMPTY_WORD for
    ///   new accounts.
    /// - INPUT_NOTES_COMMITMENT, see `transaction::api::get_input_notes_commitment`.
    pub fn build_input_stack(
        account_id: AccountId,
        initial_account_commitment: Word,
        input_notes_commitment: Word,
        block_commitment: Word,
        block_num: BlockNumber,
    ) -> StackInputs {
        // Note: Must be kept in sync with the transaction's kernel prepare_transaction procedure
        let mut inputs: Vec<Felt> = Vec::with_capacity(14);
        inputs.extend_from_slice(block_commitment.as_elements());
        inputs.extend_from_slice(initial_account_commitment.as_elements());
        inputs.extend(input_notes_commitment);
        inputs.push(account_id.suffix());
        inputs.push(account_id.prefix().as_felt());
        inputs.push(Felt::from(block_num));

        StackInputs::new(&inputs).expect("number of stack inputs should be <= 16")
    }

    /// Builds the stack for expected transaction execution outputs.
    /// The transaction kernel's output stack is formed like so:
    ///
    /// ```text
    /// [
    ///     OUTPUT_NOTES_COMMITMENT,
    ///     ACCOUNT_UPDATE_COMMITMENT,
    ///     native_asset_id_suffix, native_asset_id_prefix, fee_amount, expiration_block_num
    /// ]
    /// ```
    ///
    /// Where:
    /// - OUTPUT_NOTES_COMMITMENT is a commitment to the output notes.
    /// - ACCOUNT_UPDATE_COMMITMENT is the hash of the the final account commitment and account
    ///   delta commitment.
    /// - FEE_ASSET is the fungible asset used as the transaction fee.
    /// - expiration_block_num is the block number at which the transaction will expire.
    pub fn build_output_stack(
        final_account_commitment: Word,
        account_delta_commitment: Word,
        output_notes_commitment: Word,
        fee: FungibleAsset,
        expiration_block_num: BlockNumber,
    ) -> StackOutputs {
        let account_update_commitment =
            Hasher::merge(&[final_account_commitment, account_delta_commitment]);

        let mut outputs: Vec<Felt> = Vec::with_capacity(12);
        outputs.extend(output_notes_commitment);
        outputs.extend(account_update_commitment);
        outputs.push(fee.faucet_id().suffix());
        outputs.push(fee.faucet_id().prefix().as_felt());
        outputs.push(Felt::try_from(fee.amount()).expect("amount should fit into felt"));
        outputs.push(Felt::from(expiration_block_num));

        StackOutputs::new(&outputs).expect("number of stack inputs should be <= 16")
    }

    /// Extracts transaction output data from the provided stack outputs.
    ///
    /// The data on the stack is expected to be arranged as follows:
    ///
    /// ```text
    /// [
    ///     OUTPUT_NOTES_COMMITMENT,
    ///     ACCOUNT_UPDATE_COMMITMENT,
    ///     FEE_ASSET,
    ///     expiration_block_num,
    /// ]
    /// ```
    ///
    /// Where:
    /// - OUTPUT_NOTES_COMMITMENT is the commitment of the output notes.
    /// - ACCOUNT_UPDATE_COMMITMENT is the hash of the the final account commitment and account
    ///   delta commitment.
    /// - FEE_ASSET is the fungible asset used as the transaction fee.
    /// - tx_expiration_block_num is the block height at which the transaction will become expired,
    ///   defined by the sum of the execution block ref and the transaction's block expiration delta
    ///   (if set during transaction execution).
    ///
    /// # Errors
    ///
    /// Returns an error if:
    /// - Indices 13..16 on the stack are not zeroes.
    /// - Overflow addresses are not empty.
    pub fn parse_output_stack(
        stack: &StackOutputs, // FIXME TODO add an extension trait for this one
    ) -> Result<(Word, Word, FungibleAsset, BlockNumber), TransactionOutputError> {
        let output_notes_commitment = stack
            .get_word(TransactionOutputs::OUTPUT_NOTES_COMMITMENT_WORD_IDX)
            .expect("output_notes_commitment (first word) missing");

        let account_update_commitment = stack
            .get_word(TransactionOutputs::ACCOUNT_UPDATE_COMMITMENT_WORD_IDX)
            .expect("account_update_commitment (second word) missing");

        let native_asset_id_prefix = stack
            .get_element(TransactionOutputs::NATIVE_ASSET_ID_PREFIX_ELEMENT_IDX)
            .expect("native_asset_id_prefix missing");
        let native_asset_id_suffix = stack
            .get_element(TransactionOutputs::NATIVE_ASSET_ID_SUFFIX_ELEMENT_IDX)
            .expect("native_asset_id_suffix missing");
        let fee_amount = stack
            .get_element(TransactionOutputs::FEE_AMOUNT_ELEMENT_IDX)
            .expect("fee_amount missing");

        let expiration_block_num = stack
            .get_element(TransactionOutputs::EXPIRATION_BLOCK_ELEMENT_IDX)
            .expect("tx_expiration_block_num missing");

        let expiration_block_num = u32::try_from(expiration_block_num.as_canonical_u64())
            .map_err(|_| {
                TransactionOutputError::OutputStackInvalid(
                    "expiration block number should be smaller than u32::MAX".into(),
                )
            })?
            .into();

        // Make sure that indices 13, 14 and 15 are zeroes (i.e. the fourth word without the
        // expiration block number).
        if stack.get_word(12).expect("fourth word missing").as_elements()[..3]
            != Word::empty().as_elements()[..3]
        {
            return Err(TransactionOutputError::OutputStackInvalid(
                "indices 13, 14 and 15 on the output stack should be ZERO".into(),
            ));
        }

        let native_asset_id =
            AccountId::try_from_elements(native_asset_id_suffix, native_asset_id_prefix)
                .expect("native asset ID should be validated by the tx kernel");
        let fee = FungibleAsset::new(native_asset_id, fee_amount.as_canonical_u64())
            .map_err(TransactionOutputError::FeeAssetNotFungibleAsset)?;

        Ok((output_notes_commitment, account_update_commitment, fee, expiration_block_num))
    }

    // TRANSACTION OUTPUT PARSER
    // --------------------------------------------------------------------------------------------

    /// Returns [TransactionOutputs] constructed from the provided output stack and advice map.
    ///
    /// The output stack is expected to be arranged as follows:
    ///
    /// ```text
    /// [
    ///     OUTPUT_NOTES_COMMITMENT,
    ///     ACCOUNT_UPDATE_COMMITMENT,
    ///     FEE_ASSET,
    ///     expiration_block_num,
    /// ]
    /// ```
    ///
    /// Where:
    /// - OUTPUT_NOTES_COMMITMENT is the commitment of the output notes.
    /// - ACCOUNT_UPDATE_COMMITMENT is the hash of the final account commitment and the account
    ///   delta commitment of the account that the transaction is being executed against.
    /// - FEE_ASSET is the fungible asset used as the transaction fee.
    /// - tx_expiration_block_num is the block height at which the transaction will become expired,
    ///   defined by the sum of the execution block ref and the transaction's block expiration delta
    ///   (if set during transaction execution).
    ///
    /// The actual data describing the new account state and output notes is expected to be located
    /// in the provided advice map under keys `OUTPUT_NOTES_COMMITMENT` and
    /// `ACCOUNT_UPDATE_COMMITMENT`, where the final data for the account state is located under
    /// `FINAL_ACCOUNT_COMMITMENT`.
    pub fn from_transaction_parts(
        stack: &StackOutputs,
        advice_inputs: &AdviceInputs,
        output_notes: Vec<RawOutputNote>,
    ) -> Result<TransactionOutputs, TransactionOutputError> {
        let (output_notes_commitment, account_update_commitment, fee, expiration_block_num) =
            Self::parse_output_stack(stack)?;

        let (final_account_commitment, account_delta_commitment) =
            Self::parse_account_update_commitment(account_update_commitment, advice_inputs)?;

        // parse final account state
        let final_account_data = advice_inputs
            .map
            .get(&final_account_commitment)
            .ok_or(TransactionOutputError::FinalAccountCommitmentMissingInAdviceMap)?;

        let account = AccountHeader::try_from_elements(final_account_data)
            .map_err(TransactionOutputError::FinalAccountHeaderParseFailure)?;

        // validate output notes
        let output_notes = RawOutputNotes::new(output_notes)?;
        if output_notes_commitment != output_notes.commitment() {
            return Err(TransactionOutputError::OutputNotesCommitmentInconsistent {
                actual: output_notes.commitment(),
                expected: output_notes_commitment,
            });
        }

        Ok(TransactionOutputs {
            account,
            account_delta_commitment,
            output_notes,
            fee,
            expiration_block_num,
        })
    }

    /// Returns the final account commitment and account delta commitment extracted from the account
    /// update commitment.
    fn parse_account_update_commitment(
        account_update_commitment: Word,
        advice_inputs: &AdviceInputs,
    ) -> Result<(Word, Word), TransactionOutputError> {
        let account_update_data =
            advice_inputs.map.get(&account_update_commitment).ok_or_else(|| {
                TransactionOutputError::AccountUpdateCommitment(
                    "failed to find ACCOUNT_UPDATE_COMMITMENT in advice map".into(),
                )
            })?;

        if account_update_data.len() != 8 {
            return Err(TransactionOutputError::AccountUpdateCommitment(
                "expected account update commitment advice map entry to contain exactly 8 elements"
                    .into(),
            ));
        }

        // SAFETY: We just asserted that the data is of length 8 so slicing the data into two words
        // is fine.
        let final_account_commitment = Word::from(
            <[Felt; 4]>::try_from(&account_update_data[0..4])
                .expect("we should have sliced off exactly four elements"),
        );
        let account_delta_commitment = Word::from(
            <[Felt; 4]>::try_from(&account_update_data[4..8])
                .expect("we should have sliced off exactly four elements"),
        );

        let computed_account_update_commitment =
            Hasher::merge(&[final_account_commitment, account_delta_commitment]);

        if computed_account_update_commitment != account_update_commitment {
            let err_message = format!(
                "transaction outputs account update commitment {account_update_commitment} but commitment computed from its advice map entries was {computed_account_update_commitment}"
            );
            return Err(TransactionOutputError::AccountUpdateCommitment(err_message.into()));
        }

        Ok((final_account_commitment, account_delta_commitment))
    }

    // UTILITY METHODS
    // --------------------------------------------------------------------------------------------

    /// Computes the sequential hash of all kernel procedures.
    pub fn to_commitment(&self) -> Word {
        <Self as SequentialCommit>::to_commitment(self)
    }
}

#[cfg(any(feature = "testing", test))]
impl TransactionKernel {
    const KERNEL_TESTING_LIB_BYTES: &'static [u8] =
        include_bytes!(concat!(env!("OUT_DIR"), "/assets/kernels/kernel_library.masl"));

    /// Returns the kernel library.
    pub fn library() -> Library {
        Library::read_from_bytes(Self::KERNEL_TESTING_LIB_BYTES)
            .expect("failed to deserialize transaction kernel library")
    }
}

impl SequentialCommit for TransactionKernel {
    type Commitment = Word;

    /// Returns kernel procedures as vector of Felts.
    fn to_elements(&self) -> Vec<Felt> {
        Word::words_as_elements(Self::PROCEDURES).to_vec()
    }
}

#[cfg(all(any(feature = "testing", test), feature = "std"))]
pub(crate) mod source_manager_ext {
    use std::path::{Path, PathBuf};
    use std::vec::Vec;
    use std::{fs, io};

    use crate::assembly::SourceManager;
    use crate::assembly::debuginfo::SourceManagerExt;

    /// Loads all files with a .masm extension in the `asm` directory into the provided source
    /// manager.
    ///
    /// This source manager is passed to the [`super::TransactionKernel::assembler`] from which it
    /// can be passed on to the VM processor. If an error occurs, the sources can be used to provide
    /// a pointer to the failed location.
    pub fn load_masm_source_files(source_manager: &dyn SourceManager) {
        if let Err(err) = load(source_manager) {
            // Stringifying the error is not ideal (we may loose some source errors) but this
            // should never really error anyway.
            std::eprintln!("failed to load MASM sources into source manager: {err}");
        }
    }

    /// Implements the logic of the above function with error handling.
    fn load(source_manager: &dyn SourceManager) -> io::Result<()> {
        for file in get_masm_files(concat!(env!("OUT_DIR"), "/asm"))? {
            source_manager.load_file(&file).map_err(io::Error::other)?;
        }

        Ok(())
    }

    /// Returns a vector with paths to all MASM files in the specified directory and recursive
    /// directories.
    ///
    /// All non-MASM files are skipped.
    fn get_masm_files<P: AsRef<Path>>(dir_path: P) -> io::Result<Vec<PathBuf>> {
        let mut files = Vec::new();

        match fs::read_dir(dir_path) {
            Ok(entries) => {
                for entry in entries {
                    match entry {
                        Ok(entry) => {
                            let entry_path = entry.path();
                            if entry_path.is_dir() {
                                files.extend(get_masm_files(entry_path)?);
                            } else if entry_path
                                .extension()
                                .map(|ext| ext == "masm")
                                .unwrap_or(false)
                            {
                                files.push(entry_path);
                            }
                        },
                        Err(e) => {
                            return Err(io::Error::other(format!(
                                "error reading directory entry: {e}",
                            )));
                        },
                    }
                }
            },
            Err(e) => {
                return Err(io::Error::other(format!("error reading directory: {e}")));
            },
        }

        Ok(files)
    }
}