1 use ring::hmac;
2
concat_sign(key: &hmac::Key, a: &[u8], b: &[u8]) -> hmac::Tag3 fn concat_sign(key: &hmac::Key, a: &[u8], b: &[u8]) -> hmac::Tag {
4 let mut ctx = hmac::Context::with_key(key);
5 ctx.update(a);
6 ctx.update(b);
7 ctx.sign()
8 }
9
p(out: &mut [u8], alg: hmac::Algorithm, secret: &[u8], seed: &[u8])10 fn p(out: &mut [u8], alg: hmac::Algorithm, secret: &[u8], seed: &[u8]) {
11 let hmac_key = hmac::Key::new(alg, secret);
12
13 // A(1)
14 let mut current_a = hmac::sign(&hmac_key, seed);
15 let chunk_size = alg.digest_algorithm().output_len;
16 for chunk in out.chunks_mut(chunk_size) {
17 // P_hash[i] = HMAC_hash(secret, A(i) + seed)
18 let p_term = concat_sign(&hmac_key, current_a.as_ref(), seed);
19 chunk.copy_from_slice(&p_term.as_ref()[..chunk.len()]);
20
21 // A(i+1) = HMAC_hash(secret, A(i))
22 current_a = hmac::sign(&hmac_key, current_a.as_ref());
23 }
24 }
25
concat(a: &[u8], b: &[u8]) -> Vec<u8>26 fn concat(a: &[u8], b: &[u8]) -> Vec<u8> {
27 let mut ret = Vec::new();
28 ret.extend_from_slice(a);
29 ret.extend_from_slice(b);
30 ret
31 }
32
prf(out: &mut [u8], alg: hmac::Algorithm, secret: &[u8], label: &[u8], seed: &[u8])33 pub(crate) fn prf(out: &mut [u8], alg: hmac::Algorithm, secret: &[u8], label: &[u8], seed: &[u8]) {
34 let joined_seed = concat(label, seed);
35 p(out, alg, secret, &joined_seed);
36 }
37
38 #[cfg(test)]
39 mod tests {
40 use ring::hmac::{HMAC_SHA256, HMAC_SHA512};
41
42 #[test]
check_sha256()43 fn check_sha256() {
44 let secret = b"\x9b\xbe\x43\x6b\xa9\x40\xf0\x17\xb1\x76\x52\x84\x9a\x71\xdb\x35";
45 let seed = b"\xa0\xba\x9f\x93\x6c\xda\x31\x18\x27\xa6\xf7\x96\xff\xd5\x19\x8c";
46 let label = b"test label";
47 let expect = include_bytes!("../testdata/prf-result.1.bin");
48 let mut output = [0u8; 100];
49
50 super::prf(&mut output, HMAC_SHA256, secret, label, seed);
51 assert_eq!(expect.len(), output.len());
52 assert_eq!(expect.to_vec(), output.to_vec());
53 }
54
55 #[test]
check_sha512()56 fn check_sha512() {
57 let secret = b"\xb0\x32\x35\x23\xc1\x85\x35\x99\x58\x4d\x88\x56\x8b\xbb\x05\xeb";
58 let seed = b"\xd4\x64\x0e\x12\xe4\xbc\xdb\xfb\x43\x7f\x03\xe6\xae\x41\x8e\xe5";
59 let label = b"test label";
60 let expect = include_bytes!("../testdata/prf-result.2.bin");
61 let mut output = [0u8; 196];
62
63 super::prf(&mut output, HMAC_SHA512, secret, label, seed);
64 assert_eq!(expect.len(), output.len());
65 assert_eq!(expect.to_vec(), output.to_vec());
66 }
67 }
68