onepass 2.3.4

// Copyright 2025 Steven Dee
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

use anyhow::Result;
use argon2::{Algorithm, Argon2, Params, Version};
use rand_chacha::ChaCha20Rng;
use rand_core::{RngCore, SeedableRng};
use zeroize::{ZeroizeOnDrop, Zeroizing, zeroize_flat_type};

/// Rng wraps a `ChaCha20Rng` but zeroizes it on drop. It also supports creation from a password
/// and salt via argon2id with our chosen parameters.
pub(crate) struct Rng(ChaCha20Rng);

impl Rng {
    pub fn from_password_salt(password: &str, salt: &str) -> Result<Self> {
        let mut key_material = Zeroizing::new([0u8; 32]);
        let params =
            Params::new(32 * 1024, 3, 1, None).map_err(|e| anyhow::anyhow!("Params::new: {e}"))?;
        Argon2::new(Algorithm::Argon2id, Version::V0x13, params)
            .hash_password_into(password.as_bytes(), salt.as_bytes(), &mut *key_material)
            .map_err(|e| anyhow::anyhow!("argon2 failed: {e}"))?;
        Ok(Rng(ChaCha20Rng::from_seed(*key_material)))
    }
}

impl RngCore for Rng {
    fn next_u32(&mut self) -> u32 {
        self.0.next_u32()
    }
    fn next_u64(&mut self) -> u64 {
        self.0.next_u64()
    }
    fn fill_bytes(&mut self, dst: &mut [u8]) {
        self.0.fill_bytes(dst);
    }
    fn try_fill_bytes(&mut self, dst: &mut [u8]) -> std::result::Result<(), rand_core::Error> {
        self.0.try_fill_bytes(dst)
    }
}

impl Drop for Rng {
    fn drop(&mut self) {
        unsafe { zeroize_flat_type(self) }
    }
}
impl ZeroizeOnDrop for Rng {}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_vectors() -> Result<()> {
        let mut rng = Rng::from_password_salt("test", "testsalt")?;
        let res = rng.next_u64();
        assert_eq!(0xfa6a0c49ba644eb2, res, "{res:x}");
        Ok(())
    }
}