bitwarden_crypto/
util.rs

1use std::pin::Pin;
2
3use hmac::digest::OutputSizeUser;
4use hybrid_array::{Array, ArraySize};
5use rand::{
6    RngExt,
7    distr::{Alphanumeric, Distribution, SampleString, StandardUniform},
8};
9use typenum::Unsigned;
10use zeroize::{Zeroize, Zeroizing};
11
12use crate::Result;
13
14pub(crate) type PbkdfSha256Hmac = hmac::Hmac<sha2::Sha256>;
15pub(crate) const PBKDF_SHA256_HMAC_OUT_SIZE: usize =
16    <<PbkdfSha256Hmac as OutputSizeUser>::OutputSize as Unsigned>::USIZE;
17
18#[derive(Debug)]
19pub(crate) enum HkdfExpandError {
20    InvalidInputLegth,
21    InvalidOutputLength,
22}
23
24/// [RFC5869](https://datatracker.ietf.org/doc/html/rfc5869) HKDF-Expand operation
25pub(crate) fn hkdf_expand<T: ArraySize>(
26    prk: &[u8],
27    info: Option<&str>,
28) -> Result<Pin<Box<Array<u8, T>>>, HkdfExpandError> {
29    let hkdf = hkdf::Hkdf::<sha2::Sha256>::from_prk(prk)
30        .map_err(|_| HkdfExpandError::InvalidInputLegth)?;
31    let mut key = Box::<Array<u8, T>>::default();
32
33    let i = info.map(|i| i.as_bytes()).unwrap_or(&[]);
34    hkdf.expand(i, key.as_mut_slice())
35        .map_err(|_| HkdfExpandError::InvalidOutputLength)?;
36
37    Ok(Box::into_pin(key))
38}
39
40/// Generate random bytes that are cryptographically secure
41pub fn generate_random_bytes<T>() -> Zeroizing<T>
42where
43    StandardUniform: Distribution<T>,
44    T: Zeroize,
45{
46    Zeroizing::new(rand::rng().random::<T>())
47}
48
49/// Generate a random alphanumeric string of a given length
50///
51/// Note: Do not use this generating user facing passwords. Use the `bitwarden-generator` crate for
52/// that.
53pub fn generate_random_alphanumeric(len: usize) -> String {
54    Alphanumeric.sample_string(&mut rand::rng(), len)
55}
56
57/// Derive pbkdf2 of a given password and salt
58pub fn pbkdf2(password: &[u8], salt: &[u8], rounds: u32) -> [u8; PBKDF_SHA256_HMAC_OUT_SIZE] {
59    pbkdf2::pbkdf2_array::<PbkdfSha256Hmac, PBKDF_SHA256_HMAC_OUT_SIZE>(password, salt, rounds)
60        .expect("hash is a valid fixed size")
61}
62
63#[cfg(test)]
64mod tests {
65    use typenum::U64;
66
67    use super::*;
68
69    #[test]
70    fn test_hkdf_expand() {
71        let prk = &[
72            23, 152, 120, 41, 214, 16, 156, 133, 71, 226, 178, 135, 208, 255, 66, 101, 189, 70,
73            173, 30, 39, 215, 175, 236, 38, 180, 180, 62, 196, 4, 159, 70,
74        ];
75        let info = Some("info");
76
77        let result: Pin<Box<Array<u8, U64>>> = hkdf_expand(prk, info).unwrap();
78
79        let expected_output: [u8; 64] = [
80            6, 114, 42, 38, 87, 231, 30, 109, 30, 255, 104, 129, 255, 94, 92, 108, 124, 145, 215,
81            208, 17, 60, 135, 22, 70, 158, 40, 53, 45, 182, 8, 63, 65, 87, 239, 234, 185, 227, 153,
82            122, 115, 205, 144, 56, 102, 149, 92, 139, 217, 102, 119, 57, 37, 57, 251, 178, 18, 52,
83            94, 77, 132, 215, 239, 100,
84        ];
85
86        assert_eq!(result.as_slice(), expected_output);
87    }
88
89    #[test]
90    fn test_hkdf_expand_invalid_input_length() {
91        // PRK must be at least HashLen (32 bytes for SHA-256), using a too-short key
92        let prk = &[1, 2, 3, 4, 5];
93        let info = Some("info");
94
95        let result: Result<Pin<Box<Array<u8, U64>>>, HkdfExpandError> = hkdf_expand(prk, info);
96
97        assert!(matches!(result, Err(HkdfExpandError::InvalidInputLegth)));
98    }
99
100    #[test]
101    fn test_hkdf_expand_invalid_output_length() {
102        let prk = &[
103            23, 152, 120, 41, 214, 16, 156, 133, 71, 226, 178, 135, 208, 255, 66, 101, 189, 70,
104            173, 30, 39, 215, 175, 236, 38, 180, 180, 62, 196, 4, 159, 70,
105        ];
106        let info = Some("info");
107
108        // HKDF-SHA256 can produce at most 255 * 32 = 8160 bytes, requesting more should fail
109        type TooLarge = typenum::U8192;
110        let result: Result<Pin<Box<Array<u8, TooLarge>>>, HkdfExpandError> = hkdf_expand(prk, info);
111
112        assert!(matches!(result, Err(HkdfExpandError::InvalidOutputLength)));
113    }
114}
bitwarden_crypto/util.rs

bitwarden_crypto/
util.rs
