bitwarden_crypto/keys/
shareable_key.rs

1use std::pin::Pin;
2
3use hmac::{KeyInit, Mac};
4use hybrid_array::Array;
5use typenum::U64;
6use zeroize::Zeroizing;
7
8use super::Aes256CbcHmacKey;
9use crate::util::{PbkdfSha256Hmac, hkdf_expand};
10
11/// Derive a shareable key using hkdf from secret and name.
12///
13/// A specialized variant of this function was called `CryptoService.makeSendKey` in the Bitwarden
14/// `clients` repository.
15pub fn derive_shareable_key(
16    secret: Zeroizing<[u8; 16]>,
17    name: &str,
18    info: Option<&str>,
19) -> Aes256CbcHmacKey {
20    // Because all inputs are fixed size, we can unwrap all errors here without issue
21    let res = Zeroizing::new(
22        PbkdfSha256Hmac::new_from_slice(format!("bitwarden-{name}").as_bytes())
23            .expect("hmac new_from_slice should not fail")
24            .chain_update(secret)
25            .finalize()
26            .into_bytes(),
27    );
28
29    // HKDF already produces the `enc_key || mac_key` layout the key stores internally.
30    let key: Pin<Box<Array<u8, U64>>> = hkdf_expand(&res, info).expect("Input is a valid size");
31    Aes256CbcHmacKey { key }
32}
33
34#[cfg(test)]
35mod tests {
36    use zeroize::Zeroizing;
37
38    use super::derive_shareable_key;
39    use crate::SymmetricCryptoKey;
40
41    #[test]
42    fn test_derive_shareable_key() {
43        let key = derive_shareable_key(Zeroizing::new(*b"&/$%F1a895g67HlX"), "test_key", None);
44        assert_eq!(
45            SymmetricCryptoKey::Aes256CbcHmacKey(key)
46                .to_base64()
47                .to_string(),
48            "4PV6+PcmF2w7YHRatvyMcVQtI7zvCyssv/wFWmzjiH6Iv9altjmDkuBD1aagLVaLezbthbSe+ktR+U6qswxNnQ=="
49        );
50
51        let key = derive_shareable_key(
52            Zeroizing::new(*b"67t9b5g67$%Dh89n"),
53            "test_key",
54            Some("test"),
55        );
56        assert_eq!(
57            SymmetricCryptoKey::Aes256CbcHmacKey(key)
58                .to_base64()
59                .to_string(),
60            "F9jVQmrACGx9VUPjuzfMYDjr726JtL300Y3Yg+VYUnVQtQ1s8oImJ5xtp1KALC9h2nav04++1LDW4iFD+infng=="
61        );
62    }
63}
bitwarden_crypto/keys/shareable_key.rs

bitwarden_crypto/keys/
shareable_key.rs
