# Security Policy

## Reporting a Vulnerability

**Critical or high severity** (key leakage, authentication bypass, ratchet desync
that leaks plaintext, FFI memory corruption):

> **security@lo.sh**

Use this for anything an attacker could exploit. If you have our public key,
encrypt the report. We will acknowledge within 72 hours and aim to ship a fix
within 14 days of confirmation.

**Medium or low severity** (interoperability bugs, non-exploitable logic errors,
documentation issues):

> Open an issue at **https://git.lo.sh/lo/libsoliton**

When in doubt, use the email. We would rather triage a false alarm than miss a
real vulnerability.

## Supported Versions

| Version | Supported |
|---------|-----------|
| 0.1.x   | Yes       |

Only the latest release is supported. Security fixes are not backported.

## Threat Model

### In scope

- **Protocol logic** in LO-KEX, LO-Ratchet, KEM authentication, and storage
  encryption. Bugs here (wrong KDF inputs, missing domain separation, ratchet
  state corruption) are the primary risk.
- **Memory safety** in the Rust code and the `unsafe` FFI boundary
  (`libsoliton_capi`). Unsound pointer handling, use-after-free in opaque state
  objects, buffer overflows in slice construction.
- **Wrapper binding correctness** (`soliton_py`, `soliton_wasm`, `soliton_zig`).
  Incorrect type marshaling, use-after-free of opaque handles, missing zeroization
  at the binding layer, header serialization mismatches. The Python and WASM
  bindings wrap the core Rust API via PyO3 and wasm-bindgen respectively (no
  `unsafe` in the bindings themselves). The Zig wrapper consumes the C ABI
  directly.
- **Key management** — failure to zeroize secrets, key material leaking into
  logs or error messages, nonce reuse.
- **Cryptographic misuse** — wrong algorithm parameters, truncated hashes,
  clamping errors, incorrect domain separators.

### Out of scope

- **Side-channel attacks in upstream Rust crates.** Timing, power, or EM side
  channels in ML-KEM-768 (`ml-kem`), ML-DSA-65 (`ml-dsa`), X25519
  (`x25519-dalek`), or Ed25519 (`ed25519-dalek`) are upstream concerns.
  Report those to the relevant [RustCrypto](https://github.com/RustCrypto)
  or [dalek-cryptography](https://github.com/dalek-cryptography) project.
  XChaCha20-Poly1305 and Ed25519 are constant-time by construction (ARX
  operations only, no table lookups).
- **WASM linear memory.** Secret key material in WASM cannot be reliably
  zeroized — the linear memory is GC-managed by the JS engine and may be
  copied, paged, or retained after `free()`. This is inherent to the WASM
  execution model, not a library bug.
- **Python GC.** `bytes` objects returned by the Python binding are
  GC-managed. The Rust side zeroizes its copy, but the Python object persists
  until collected. Context managers (`with`) minimize the window.
- **Compression oracle (CRIME/BREACH-style).** When streaming AEAD compression
  is enabled and an attacker controls partial plaintext, ciphertext length may
  leak information about co-resident secret content. File transfer (the primary
  use case) does not have attacker-controlled plaintext injection, so this is
  not exploitable in the intended deployment. Applications mixing
  attacker-controlled and secret data in a single compressed stream should
  disable compression.
- **Hardware faults** — rowhammer, fault injection, glitching.
- **Denial of service** — resource exhaustion from large inputs is a bug, but
  not a security vulnerability in a library context.

### Known limitations

- **PQ crates are pre-1.0.** ML-KEM and ML-DSA are NIST FIPS 203/204 final,
  but the RustCrypto implementations (`ml-kem`, `ml-dsa`) have not undergone
  the same decades of scrutiny as, say, OpenSSL's AES. This is inherent to
  post-quantum cryptography in 2026.
- **X-Wing is a draft.** We implement draft-connolly-cfrg-xwing-kem-09. The
  combiner and encoding may change before the RFC is finalized.
- **Ed25519 (RFC 8032)** is used for classical signing via `ed25519-dalek`.
  Strict verification mode rejects non-canonical signatures and small-order
  public keys, preventing malleability attacks.
- **XChaCha20-Poly1305** is constant-time by construction (ARX operations
  only — no table lookups or secret-dependent branches). No hardware
  acceleration is required; it runs at full speed on all platforms including
  RISC-V.

## Dependencies

All dependencies are pure Rust — no C libraries, no cmake, no system linker
dependencies.

| Dependency | Role |
|------------|------|
| [ml-kem](https://crates.io/crates/ml-kem) | ML-KEM-768 (inside X-Wing) |
| [ml-dsa](https://crates.io/crates/ml-dsa) | ML-DSA-65 hybrid signatures |
| [ed25519-dalek](https://crates.io/crates/ed25519-dalek) | Ed25519 signing/verification |
| [x25519-dalek](https://crates.io/crates/x25519-dalek) | X25519 (inside X-Wing) |
| [chacha20poly1305](https://crates.io/crates/chacha20poly1305) | XChaCha20-Poly1305 AEAD |
| [sha3](https://crates.io/crates/sha3) | SHA3-256 (HMAC, HKDF, fingerprints, X-Wing combiner) |
| [hmac](https://crates.io/crates/hmac) | HMAC-SHA3-256 |
| [hkdf](https://crates.io/crates/hkdf) | HKDF-SHA3-256 key derivation |
| [argon2](https://crates.io/crates/argon2) | Argon2id password hashing |
| [ruzstd](https://crates.io/crates/ruzstd) | Zstd decompression (storage blobs, streaming AEAD chunks) |
| [zeroize](https://crates.io/crates/zeroize) | Secret wiping |

**Binding-specific dependencies** (not part of the core library):

| Dependency | Role |
|------------|------|
| [pyo3](https://crates.io/crates/pyo3) | Python FFI bridge (`soliton_py`) |
| [wasm-bindgen](https://crates.io/crates/wasm-bindgen) | WASM/JS interop (`soliton_wasm`) |

Vulnerabilities in these dependencies may affect libsoliton. We track upstream
advisories and update pins accordingly.