The implementation does not enforce alignment requirements on input slices while incorrectly assuming 4-byte alignment through an unsafe call to std::slice::from_raw_parts_mut, which breaks the contract and introduces undefined behavior.

This affects Chacha20 encryption and decryption in crypto2.

References

• shadowsocks/crypto2#27
• https://rustsec.org/advisories/RUSTSEC-2021-0121.html