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WASM Reproducibility

Credence treats Soroban WASM output as a supply-chain artifact. The goal is that a clean build of the bond and delegation contracts produces the same bytes every time when the source, lockfile, and toolchain are unchanged.

What CI checks

The workflow at .github/workflows/wasm-repro.yml performs two clean builds with --locked and compares SHA-256 digests for:

  • target/wasm32-unknown-unknown/release/credence_bond.wasm
  • target/wasm32-unknown-unknown/release/credence_delegation.wasm

If either hash differs between the two passes, the workflow fails immediately.

Toolchain pin

The repository pins Rust in rust-toolchain.toml to keep CI and local builds on the same compiler and target set:

  • channel = "1.85.1"
  • targets = ["wasm32-unknown-unknown"]
  • components = ["rustfmt", "clippy", "llvm-tools-preview"]

That pin is the first line of defense against drift from a moving stable toolchain.

Local reproduction

Run the same build twice from a clean working tree:

cargo build --release --target wasm32-unknown-unknown --locked -p credence_bond -p credence_delegation
sha256sum target/wasm32-unknown-unknown/release/credence_bond.wasm \
  target/wasm32-unknown-unknown/release/credence_delegation.wasm

Then clean the target directory, rebuild, and compare the digests. A passing CI run ends with the hash comparison step succeeding and no diff output.

Security notes

  • A hash mismatch is treated as a build-integrity failure, not a warning.
  • The check is designed to catch accidental nondeterminism and build-time injection before deployment.
  • Use the pinned toolchain and --locked builds when validating contract changes locally.

CI output shape

A successful run should show the two build passes completing and the final diff step exiting cleanly. A failure should surface a mismatched digest for one or both WASM artifacts and stop the merge.