libsoliton/soliton/fuzz/fuzz_targets/fuzz_stream_decrypt.rs

#![no_main]
use libfuzzer_sys::fuzz_target;
use soliton::streaming::stream_decrypt_init;

const FUZZ_KEY: [u8; 32] = [0x42; 32];

fuzz_target!(|data: &[u8]| {
    // Fuzz the streaming decryptor with adversarial header + chunk data.
    // Exercises header parsing (version, flags, reserved-bit rejection),
    // AEAD authentication, decompression bounds, and tag-byte validation.
    if data.len() < 26 + 2 {
        return;
    }
    let header: [u8; 26] = data[..26].try_into().unwrap();
    let rest = &data[26..];

    let mut dec = match stream_decrypt_init(&FUZZ_KEY, &header, b"fuzz-aad") {
        Ok(d) => d,
        Err(_) => return,
    };

    // Variable-length chunk splitting: each iteration consumes a 2-byte BE
    // length prefix followed by that many bytes as a chunk. This allows the
    // fuzzer to discover valid chunk sizes (including STREAM_CHUNK_SIZE + 17
    // for non-final chunks) through mutation, unlike fixed-size splitting.
    let mut cursor = 0;
    while cursor + 2 <= rest.len() {
        let chunk_len =
            u16::from_be_bytes([rest[cursor], rest[cursor + 1]]) as usize;
        cursor += 2;
        if cursor + chunk_len > rest.len() {
            break;
        }
        let chunk_data = &rest[cursor..cursor + chunk_len];
        cursor += chunk_len;

        match dec.decrypt_chunk(chunk_data) {
            Ok((_, true)) => return, // finalized
            Ok((_, false)) => {}
            Err(_) => return,
        }
    }
});