fuzzer_lib.cpp

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#include "barretenberg/avm_fuzzer/fuzzer_lib.hpp"
 
#include <cstdint>
#include <string>
#include <unordered_set>
#include <vector>
 
#include "barretenberg/api/file_io.hpp"
#include "barretenberg/avm_fuzzer/common/interfaces/dbs.hpp"
#include "barretenberg/avm_fuzzer/fuzz_lib/constants.hpp"
#include "barretenberg/avm_fuzzer/fuzz_lib/control_flow.hpp"
#include "barretenberg/avm_fuzzer/fuzzer_comparison_helper.hpp"
#include "barretenberg/avm_fuzzer/mutations/basic_types/field.hpp"
#include "barretenberg/avm_fuzzer/mutations/basic_types/uint64_t.hpp"
#include "barretenberg/avm_fuzzer/mutations/configuration.hpp"
#include "barretenberg/avm_fuzzer/mutations/fuzzer_data.hpp"
#include "barretenberg/avm_fuzzer/mutations/protocol_contracts.hpp"
#include "barretenberg/avm_fuzzer/mutations/tx_data.hpp"
#include "barretenberg/avm_fuzzer/mutations/tx_types/gas.hpp"
#include "barretenberg/common/log.hpp"
#include "barretenberg/vm2/avm_api.hpp"
#include "barretenberg/vm2/common/avm_io.hpp"
#include "barretenberg/vm2/common/aztec_types.hpp"
#include "barretenberg/vm2/simulation/lib/contract_crypto.hpp"
#include "barretenberg/vm2/simulation_helper.hpp"
#include "barretenberg/vm2/tooling/stats.hpp"
#include "barretenberg/vm2/tracegen_helper.hpp"
 
using namespace bb::avm2::fuzzer;
using namespace bb::avm2::simulation;
using namespace bb::world_state;
 
extern size_t LLVMFuzzerMutate(uint8_t* Data, size_t Size, size_t MaxSize);
 
void setup_fuzzer_state(FuzzerWorldStateManager& ws_mgr, FuzzerContractDB& contract_db, const FuzzerTxData& tx_data)
{
    // Add all contract classes and instances to the contract DB
    // There may be more classes than instances because of the possibility of mutated bytecodes that are used in
    // upgrades - these are not directly instantiated
    for (size_t i = 0; i < tx_data.contract_classes.size(); ++i) {
        const auto& contract_class = tx_data.contract_classes[i];
        contract_db.add_contract_class(contract_class.id, contract_class);
    }
 
    // Add contract instances to the contract DB
    for (size_t i = 0; i < tx_data.contract_instances.size(); ++i) {
        const auto& contract_instance = tx_data.contract_instances[i];
        auto contract_address = tx_data.contract_addresses[i];
        contract_db.add_contract_instance(contract_address, contract_instance);
    }
 
    // For protocol contracts, also add instances keyed by canonical address (1-11).
    // This is needed because protocol contracts are looked up by canonical address,
    // but the derived address in protocol_contracts.derived_addresses maps to the actual instance.
    for (size_t i = 0; i < tx_data.protocol_contracts.derived_addresses.size(); ++i) {
        const auto& derived_address = tx_data.protocol_contracts.derived_addresses[i];
        if (!derived_address.is_zero()) {
            // Canonical address is index + 1 (addresses 1-11 map to indices 0-10)
            AztecAddress canonical_address(static_cast<uint256_t>(i + 1));
            // Find the instance for this derived address and also add it by canonical address
            auto maybe_instance = contract_db.get_contract_instance(derived_address);
            if (maybe_instance.has_value()) {
                contract_db.add_contract_instance(canonical_address, maybe_instance.value());
            }
        }
    }
 
    // Register contract addresses in the world state
    for (const auto& addr : tx_data.contract_addresses) {
        ws_mgr.register_contract_address(addr);
    }
 
    // Apply public data tree writes (e.g., for contract instance upgrades)
    for (const auto& write : tx_data.public_data_writes) {
        ws_mgr.public_data_write(write);
    }
 
    ws_mgr.append_note_hashes(tx_data.note_hashes);
}
 
void fund_fee_payer(FuzzerWorldStateManager& ws_mgr, const Tx& tx)
{
    // Compute fee from gas limits and max fees per gas (upper bound on fee)
    FF fee_required_da = FF(tx.gas_settings.gas_limits.da_gas) * FF(tx.gas_settings.max_fees_per_gas.fee_per_da_gas);
    FF fee_required_l2 = FF(tx.gas_settings.gas_limits.l2_gas) * FF(tx.gas_settings.max_fees_per_gas.fee_per_l2_gas);
 
    // Fund fee payer with required fee
    ws_mgr.write_fee_payer_balance(tx.fee_payer, fee_required_da + fee_required_l2);
}
 
SimulatorResult fuzz_tx(FuzzerWorldStateManager& ws_mgr, FuzzerContractDB& contract_db, FuzzerTxData& tx_data)
{
    auto cpp_simulator = CppSimulator();
    SimulatorResult cpp_result;
 
    try {
        ws_mgr.checkpoint();
        cpp_result = cpp_simulator.simulate(ws_mgr,
                                            contract_db,
                                            tx_data.tx,
                                            tx_data.global_variables,
                                            tx_data.public_data_writes,
                                            tx_data.note_hashes,
                                            tx_data.protocol_contracts);
        fuzz_info("CppSimulator completed without exception");
        fuzz_info("CppSimulator result: ", cpp_result);
        ws_mgr.revert();
    } catch (const std::exception& e) {
        fuzz_info("CppSimulator threw an exception: ", e.what());
        cpp_result = SimulatorResult{
            .reverted = true,
            .output = {},
            .end_tree_snapshots = TreeSnapshots(),
            .revert_reason = e.what(),
        };
        ws_mgr.revert();
    }
 
    return cpp_result;
}
 
TxSimulationResult fuzz_prover(FuzzerWorldStateManager& ws_mgr, FuzzerContractDB& contract_db, FuzzerTxData& tx_data)
{
    ProtocolContracts& protocol_contracts = tx_data.protocol_contracts;
    WorldState& ws = ws_mgr.get_world_state();
    WorldStateRevision ws_rev = ws_mgr.get_current_revision();
    AvmSimulationHelper helper;
 
    // Reset stats for this iteration
    bb::avm2::Stats::get().reset();
 
    const PublicSimulatorConfig sim_fast_config{
        .skip_fee_enforcement = false,
        .collect_call_metadata = true,
        .collect_public_inputs = true,
    };
 
    const PublicSimulatorConfig sim_hint_config{
        .skip_fee_enforcement = false,
        .collect_call_metadata = true,
        .collect_hints = true,
        .collect_public_inputs = true,
    };
 
    // 1. Run simulate_fast_with_existing_ws
    // It is the only one that may throw, so we wrap it in try-catch. If it fails, we do not proceed
    TxSimulationResult fast_result;
    try {
        ws_mgr.checkpoint();
        fast_result = AVM_TRACK_TIME_V(
            "fuzzer/simulate_fast",
            helper.simulate_fast_with_existing_ws(
                contract_db, ws_rev, ws, sim_fast_config, tx_data.tx, tx_data.global_variables, protocol_contracts));
        ws_mgr.revert();
    } catch (const std::exception& e) {
        ws_mgr.revert();
        fuzz_info("simulate_fast_with_existing_ws threw an exception: ", e.what());
        return {};
    }
 
    // 2. Run simulate_for_hint_collection
    ws_mgr.checkpoint();
    TxSimulationResult hint_result = AVM_TRACK_TIME_V(
        "fuzzer/simulate_hints",
        helper.simulate_for_hint_collection(
            contract_db, ws_rev, ws, sim_hint_config, tx_data.tx, tx_data.global_variables, protocol_contracts));
    ws_mgr.revert();
 
    // 2a. Construct proving inputs from hint result
    bb::avm2::AvmProvingInputs proving_inputs{
        .public_inputs = hint_result.public_inputs.value(),
        .hints = hint_result.hints.value(),
    };
 
    // 3. (optional) Simulate Fast with hinted db
    TxSimulationResult sim_fast_hinted_result =
        helper.simulate_fast_with_hinted_dbs(proving_inputs.hints, sim_fast_config);
 
    // 4. Compare results from all 3 simulations
    bool result = compare_cpp_simulator_results({ fast_result, hint_result, sim_fast_hinted_result });
    BB_ASSERT(result,
              "Simulation results do not match between simulate_fast, simulate_for_hint_collection, "
              "and simulate_fast_with_hinted_dbs");
 
    // 5. Run check_circuit (skip in coverage builds since it's slow and not needed for coverage measurement)
 
#ifndef COVERAGE_AVM
    avm2::AvmAPI avm_api;
    bool check_circuit_result = avm_api.check_circuit(proving_inputs);
    BB_ASSERT(check_circuit_result,
              "check_circuit returned false in fuzzer with no exception, this indicates a failure");
 
    // 6. Prove and verify
    auto proof = avm_api.prove(proving_inputs);
    bool verified = avm_api.verify(proof, proving_inputs.public_inputs);
    BB_ASSERT(verified, "Proof verification failed");
#else
    // In coverage builds, run simulate_for_witgen and tracegen instead of check_circuit
    // This gives us coverage the the event and tracegen code paths without the overhead of check_circuit
    vinfo("Running simulate_for_witgen in coverage build (skipping check_circuit)");
    avm2::AvmSimulationHelper simulation_helper;
    auto events = simulation_helper.simulate_for_witgen(proving_inputs.hints);
    AvmTraceGenHelper tracegen_helper;
    tracegen::TraceContainer trace;
    tracegen_helper.fill_trace_columns(trace, std::move(events), hint_result.public_inputs.value());
#endif
 
    return fast_result;
}
 
// Initialize FuzzerTxData with sensible defaults
FuzzerTxData create_default_tx_data(std::mt19937_64& rng, FuzzerContext& context)
{
    FuzzerTxData tx_data = {
        .tx = create_default_tx(MSG_SENDER, MSG_SENDER, {}, TRANSACTION_FEE, IS_STATIC_CALL, GAS_LIMIT),
        .global_variables = { .chain_id = CHAIN_ID,
                              .version = VERSION,
                              .block_number = BLOCK_NUMBER,
                              .slot_number = SLOT_NUMBER,
                              .timestamp = TIMESTAMP,
                              .coinbase = COINBASE,
                              .fee_recipient = FEE_RECIPIENT,
                              .gas_fees =
                                  GasFees{ .fee_per_da_gas = FEE_PER_DA_GAS, .fee_per_l2_gas = FEE_PER_L2_GAS } },
        .protocol_contracts = {},
        // We can write proper mutations for this. However it might not be of much value since we have variability from
        // nonrevertible note hashes.
        .note_hashes = { generate_random_field(rng), generate_random_field(rng), generate_random_field(rng) }
    };
 
    // TODO(alvaro): This is messy, we mutate when creating default tx data. Maybe we should just remove the mutation
    // from generate_fuzzer_data altogether.
    populate_context_from_tx_data(context, tx_data);
    FuzzerData fuzzer_data = generate_fuzzer_data(rng, context);
    tx_data.input_programs.push_back(fuzzer_data);
 
    return tx_data;
}
 
FuzzerTxData create_default_tx_data(FuzzerContext& context)
{
    std::mt19937_64 rng(0);
    return create_default_tx_data(rng, context);
}
 
ContractArtifacts build_bytecode_and_artifacts(FuzzerData& fuzzer_data)
{
    fuzz_info("Building bytecode from fuzzer data: ", fuzzer_data.instruction_blocks);
    auto control_flow = ControlFlow(fuzzer_data.instruction_blocks);
    for (const auto& cfg_instruction : fuzzer_data.cfg_instructions) {
        control_flow.process_cfg_instruction(cfg_instruction);
    }
    auto bytecode = control_flow.build_bytecode(fuzzer_data.return_options);
 
    auto bytecode_commitment = compute_public_bytecode_commitment(bytecode);
    auto class_id = compute_contract_class_id(/*artifact_hash=*/0, /*private_fn_root=*/0, bytecode_commitment);
    ContractClassWithCommitment contract_class{
        .id = class_id,
        .artifact_hash = 0,
        .private_functions_root = 0,
        .packed_bytecode = bytecode,
        .public_bytecode_commitment = bytecode_commitment,
    };
    ContractInstance contract_instance{
        .salt = 0,
        .deployer = MSG_SENDER,
        .current_contract_class_id = class_id, // Initial and current are the same
        .original_contract_class_id = class_id,
        .public_keys = {
            .nullifier_key_hash = 0,
            .incoming_viewing_key = grumpkin::g1::element::one(),
            .outgoing_viewing_key_hash = 0,
            .tagging_key_hash =  0,
        },
    };
    return { bytecode, contract_class, contract_instance };
}
 
size_t mutate_tx_data(FuzzerContext& context,
                      uint8_t* serialized_fuzzer_data,
                      size_t serialized_fuzzer_data_size,
                      size_t max_size,
                      unsigned int seed)
{
    auto rng = std::mt19937_64(seed);
    FuzzerTxData tx_data;
    try {
        msgpack::unpack((reinterpret_cast<const char*>(serialized_fuzzer_data)), serialized_fuzzer_data_size)
            .get()
            .convert(tx_data);
    } catch (const std::exception&) {
        fuzz_info("Failed to deserialize input in CustomMutator, creating default FuzzerTxData");
        tx_data = create_default_tx_data(rng, context);
    }
 
    populate_context_from_tx_data(context, tx_data);
 
    // Build up bytecodes, contract classes and instances from the fuzzer data
    tx_data.contract_classes.clear();
    tx_data.contract_instances.clear();
    tx_data.contract_addresses.clear();
    tx_data.public_data_writes.clear();
    std::vector<AztecAddress> contract_addresses;
 
    std::unordered_set<AztecAddress> seen_addresses;
    for (auto& fuzzer_data : tx_data.input_programs) {
        const auto [bytecode, contract_class, contract_instance] = build_bytecode_and_artifacts(fuzzer_data);
 
        auto contract_address = simulation::compute_contract_address(contract_instance);
 
        // Skip duplicate addresses - multiple input_programs can generate the same address
        if (seen_addresses.contains(contract_address)) {
            fuzz_info("Skipping duplicate contract address: ", contract_address);
            continue;
        }
        seen_addresses.insert(contract_address);
 
        contract_addresses.push_back(contract_address);
        tx_data.contract_classes.push_back(contract_class);
        tx_data.contract_instances.push_back(contract_instance);
    }
 
    tx_data.contract_addresses = contract_addresses;
 
    // Ensure all enqueued calls have valid contract addresses (not placeholders)
    // We may add more advanced mutation to change contract addresses later, right now we just ensure they are valid
    if (!contract_addresses.empty()) {
        auto idx_dist = std::uniform_int_distribution<size_t>(0, contract_addresses.size() - 1);
        for (auto& call : tx_data.tx.setup_enqueued_calls) {
            call.request.contract_address = contract_addresses[idx_dist(rng)];
        }
        for (auto& call : tx_data.tx.app_logic_enqueued_calls) {
            call.request.contract_address = contract_addresses[idx_dist(rng)];
        }
    }
 
    // Select mutation type (weighted against bytecode mutations) -- todo
    FuzzerTxDataMutationType mutation_choice = FUZZER_TX_DATA_MUTATION_CONFIGURATION.select(rng);
 
    switch (mutation_choice) {
    case FuzzerTxDataMutationType::TxFuzzerDataMutation:
        mutate_fuzzer_data_vec(context, tx_data.input_programs, rng, 64);
        break;
    case FuzzerTxDataMutationType::TxMutation:
        mutate_tx(tx_data.tx, contract_addresses, rng);
        break;
    case FuzzerTxDataMutationType::BytecodeMutation:
        mutate_bytecode(tx_data.contract_classes,
                        tx_data.contract_instances,
                        tx_data.contract_addresses,
                        tx_data.public_data_writes,
                        rng);
        break;
 
    case FuzzerTxDataMutationType::ContractClassMutation:
        mutate_contract_classes(tx_data.contract_classes, tx_data.contract_instances, tx_data.contract_addresses, rng);
        break;
    case FuzzerTxDataMutationType::ContractInstanceMutation:
        mutate_contract_instances(tx_data.contract_instances, tx_data.contract_addresses, rng);
        break;
    case FuzzerTxDataMutationType::GlobalVariablesMutation:
        // This is just mutating the gas values and timestamp
        mutate_uint64_t(tx_data.global_variables.timestamp, rng, BASIC_UINT64_T_MUTATION_CONFIGURATION);
        mutate_gas_fees(tx_data.global_variables.gas_fees, rng);
        break;
    case FuzzerTxDataMutationType::ProtocolContractsMutation:
        mutate_protocol_contracts(tx_data.protocol_contracts, tx_data.tx, tx_data.contract_addresses, rng);
        break;
    }
 
    // Clear any protocol contract derived addresses that reference addresses no longer in the contract set.
    // This can happen when mutations (e.g., ContractClassMutation, ContractInstanceMutation) change contract addresses.
    // Must run AFTER all mutations since some mutations modify contract_addresses.
    std::unordered_set<AztecAddress> valid_addresses(tx_data.contract_addresses.begin(),
                                                     tx_data.contract_addresses.end());
    for (auto& derived_address : tx_data.protocol_contracts.derived_addresses) {
        if (!derived_address.is_zero() && !valid_addresses.contains(derived_address)) {
            derived_address = AztecAddress(0);
        }
    }
 
    // Ensure at least 1 app_logic enqueued call exists (mutations may have deleted all), the public base kernel circuit
    // guarantees that there is at least 1 enqueued call in an public tx (so this is a valid assumption)
    if (tx_data.tx.app_logic_enqueued_calls.empty() && !contract_addresses.empty()) {
        auto idx = std::uniform_int_distribution<size_t>(0, contract_addresses.size() - 1)(rng);
        std::vector<FF> calldata = {};
        auto calldata_hash = compute_calldata_hash(calldata);
        tx_data.tx.app_logic_enqueued_calls.push_back(
            PublicCallRequestWithCalldata{ .request = PublicCallRequest{ .msg_sender = MSG_SENDER,
                                                                         .contract_address = contract_addresses[idx],
                                                                         .is_static_call = false,
                                                                         .calldata_hash = calldata_hash },
                                           .calldata = calldata });
    }
 
    // Ensure global gas_fees <= max_fees_per_gas (required for compute_effective_gas_fees)
    // This must run after ANY mutation since TxMutation can reduce max_fees_per_gas
    tx_data.global_variables.gas_fees.fee_per_da_gas = std::min(
        tx_data.global_variables.gas_fees.fee_per_da_gas, tx_data.tx.gas_settings.max_fees_per_gas.fee_per_da_gas);
    tx_data.global_variables.gas_fees.fee_per_l2_gas = std::min(
        tx_data.global_variables.gas_fees.fee_per_l2_gas, tx_data.tx.gas_settings.max_fees_per_gas.fee_per_l2_gas);
 
    // Compute effective gas fees matching TS computeEffectiveGasFees
    // This must be done after any mutation that could affect gas settings or global variables
    tx_data.tx.effective_gas_fees =
        compute_effective_gas_fees(tx_data.global_variables.gas_fees, tx_data.tx.gas_settings);
 
    auto [mutated_serialized_fuzzer_data, mutated_serialized_fuzzer_data_size] = msgpack_encode_buffer(tx_data);
    if (mutated_serialized_fuzzer_data_size > max_size) {
        delete[] mutated_serialized_fuzzer_data;
        return 0; // Can't fit mutated data in buffer, skip this mutation
    }
    memcpy(serialized_fuzzer_data, mutated_serialized_fuzzer_data, mutated_serialized_fuzzer_data_size);
    delete[] mutated_serialized_fuzzer_data;
 
    return mutated_serialized_fuzzer_data_size;
}
 
void populate_context_from_tx_data(FuzzerContext& context, const FuzzerTxData& tx_data)
{
    std::vector<std::pair<FF, uint64_t>> note_hash_leaf_index_pairs;
    note_hash_leaf_index_pairs.reserve(tx_data.note_hashes.size() +
                                       tx_data.tx.non_revertible_accumulated_data.note_hashes.size());
 
    // For note hashes we assume we start from an empty tree. We could read size everytime but it'd slow things down.
    // If you're having trouble with that check initialization on FuzzerWorldStateManager::initialize()
    uint64_t leaf_offset = 0;
 
    for (uint64_t i = 0; i < tx_data.note_hashes.size(); ++i) {
        note_hash_leaf_index_pairs.push_back({ tx_data.note_hashes[i], leaf_offset + i });
    }
 
    uint64_t padding_leaves = MAX_NOTE_HASHES_PER_TX - (tx_data.note_hashes.size() % MAX_NOTE_HASHES_PER_TX);
    leaf_offset += tx_data.note_hashes.size() + padding_leaves;
 
    for (uint64_t i = 0; i < tx_data.tx.non_revertible_accumulated_data.note_hashes.size(); ++i) {
        note_hash_leaf_index_pairs.push_back(
            { tx_data.tx.non_revertible_accumulated_data.note_hashes[i], leaf_offset + i });
    }
 
    context.set_existing_note_hashes(note_hash_leaf_index_pairs);
 
    context.set_existing_contract_addresses(tx_data.contract_addresses);
}