aldabra/crates/aldabra-dao/examples/repro_script_corruption.rs

//! Standalone reproducer for the large-bytestring reference-script
//! corruption observed in pallas-txbuilder.
//!
//! Usage:
//!   ALDABRA_REPRO_HEX=/path/to/governorValidator.rawhex \
//!     cargo run --example repro_script_corruption -p aldabra-dao --release
//!
//! The reproducer:
//!   1. Reads a hex-encoded Plutus V2 script (rawHex) from a file.
//!   2. Builds a minimal Conway tx with one output that carries the
//!      script as an inline reference script.
//!   3. Calls `build_conway_raw()` to produce the tx body bytes.
//!   4. Searches the tx body for the input script bytes verbatim. If
//!      it finds them: pallas's encode is byte-clean (bug is downstream
//!      — chain transport, Koios, MCP transport, etc). If it doesn't:
//!      pallas mutated the bytes during encoding, prints the diff.
//!
//! No chain query, no MCP, no JSON-RPC. Pure local serialization.

use std::env;
use std::fs;

use pallas_addresses::Address;
use pallas_txbuilder::{BuildConway, Input, Output as TxOutput, ScriptKind, StagingTransaction};
use pallas_crypto::hash::Hash;

fn hex_to_bytes(s: &str) -> Vec<u8> {
    let s = s.trim();
    let mut v = Vec::with_capacity(s.len() / 2);
    let bytes = s.as_bytes();
    let mut i = 0;
    while i + 1 < bytes.len() {
        let hi = (bytes[i] as char).to_digit(16).expect("invalid hex hi") as u8;
        let lo = (bytes[i + 1] as char).to_digit(16).expect("invalid hex lo") as u8;
        v.push((hi << 4) | lo);
        i += 2;
    }
    v
}

fn find_subseq(haystack: &[u8], needle: &[u8]) -> Option<usize> {
    if needle.is_empty() || needle.len() > haystack.len() {
        return None;
    }
    haystack
        .windows(needle.len())
        .position(|w| w == needle)
}

fn main() {
    let path = env::var("ALDABRA_REPRO_HEX")
        .expect("set ALDABRA_REPRO_HEX to a file containing the script hex");
    let hex = fs::read_to_string(&path).expect("read hex file");
    let script_bytes = hex_to_bytes(&hex);
    println!(
        "input script: {} bytes ({} hex chars)",
        script_bytes.len(),
        hex.trim().len()
    );

    let dummy_tx_hash: Hash<32> = Hash::new([0u8; 32]);
    let input = Input::new(dummy_tx_hash, 0);

    // A throwaway preprod testnet enterprise script address (just for
    // shape — no funds, no real chain interaction).
    let dest_addr = Address::from_bech32(
        "addr_test1wptadvtl64h74jmhwuda595j40ss3rgh0p9jam0ejwgz6mcnzvusa",
    )
    .expect("decode addr");

    let mut output = TxOutput::new(dest_addr, 5_000_000);
    output = output.set_inline_script(ScriptKind::PlutusV2, script_bytes.clone());

    let staging = StagingTransaction::new()
        .input(input)
        .output(output)
        .fee(2_000_000)
        .network_id(0);

    let built = staging
        .build_conway_raw()
        .expect("build_conway_raw failed");

    let tx_bytes = built.tx_bytes.0;
    println!("built tx body: {} bytes", tx_bytes.len());

    // Sanity: the script bytes should appear somewhere inside the tx
    // body. The output's script_ref encodes as `tag(24) bytes(...)`
    // wrapping the inner array `[2, bytes]`. The actual script bytes
    // are then nested inside that. Search for them verbatim.
    if let Some(pos) = find_subseq(&tx_bytes, &script_bytes) {
        println!("✅ FOUND input script bytes verbatim at tx-body offset {}", pos);
        println!("   pallas-txbuilder serialized them clean.");
    } else {
        println!("❌ DID NOT find input script bytes verbatim in tx body.");
        println!("   pallas-txbuilder mutated the bytes during encoding.");
        // Try to locate the ApproxRegion that contains them. Search
        // for the first 64 bytes of input — if THAT prefix is found,
        // the bytes start there but corrupt later. If not, the start
        // is also mutated.
        let prefix = &script_bytes[..64.min(script_bytes.len())];
        match find_subseq(&tx_bytes, prefix) {
            Some(start) => {
                println!(
                    "   Found {} -byte prefix at tx-body offset {} — mutation is later in the bytestring",
                    prefix.len(),
                    start
                );
                let region = &tx_bytes[start..(start + script_bytes.len()).min(tx_bytes.len())];
                let mut diffs = 0usize;
                let mut first_diff = None;
                for (i, (a, b)) in script_bytes.iter().zip(region.iter()).enumerate() {
                    if a != b {
                        diffs += 1;
                        if first_diff.is_none() {
                            first_diff = Some(i);
                        }
                    }
                }
                println!(
                    "   {} byte-positions differ; first diff at byte {} of script",
                    diffs,
                    first_diff.map(|x| x as i32).unwrap_or(-1)
                );
            }
            None => {
                println!("   Even the first 64 bytes don't match — corruption starts at offset 0.");
            }
        }
    }

    // Also search for the known on-chain corrupt fingerprint: at
    // bytes 2390..=2424 the on-chain version has the two 9-byte
    // blocks SWAPPED relative to input. Build the swapped version
    // and check if THAT appears in the tx body.
    if script_bytes.len() >= 2425 {
        let mut corrupted = script_bytes.clone();
        let block_a = corrupted[2390..2399].to_vec();
        let block_b = corrupted[2416..2425].to_vec();
        corrupted[2390..2399].copy_from_slice(&block_b);
        corrupted[2416..2425].copy_from_slice(&block_a);

        if find_subseq(&tx_bytes, &corrupted).is_some() {
            println!("⚠️  found CORRUPTED variant (block-swap @ 2390↔2416) in tx body.");
            println!("    pallas-txbuilder is producing the same corruption we see on chain.");
        } else {
            println!("    block-swap variant NOT found in tx body either.");
        }
    }
}