1 use ring::digest;
2 use ring::hmac;
3
4 use std::io::Write;
5
convert_digest_to_hmac_alg(hash: &'static digest::Algorithm) -> hmac::Algorithm6 fn convert_digest_to_hmac_alg(hash: &'static digest::Algorithm) -> hmac::Algorithm {
7 if hash == &digest::SHA256 {
8 hmac::HMAC_SHA256
9 } else if hash == &digest::SHA384 {
10 hmac::HMAC_SHA384
11 } else if hash == &digest::SHA512 {
12 hmac::HMAC_SHA512
13 } else {
14 panic!("bad digest for prf");
15 }
16 }
17
concat_sign(key: &hmac::Key, a: &[u8], b: &[u8]) -> hmac::Tag18 fn concat_sign(key: &hmac::Key, a: &[u8], b: &[u8]) -> hmac::Tag {
19 let mut ctx = hmac::Context::with_key(key);
20 ctx.update(a);
21 ctx.update(b);
22 ctx.sign()
23 }
24
p(out: &mut [u8], hashalg: &'static digest::Algorithm, secret: &[u8], seed: &[u8])25 fn p(out: &mut [u8], hashalg: &'static digest::Algorithm, secret: &[u8], seed: &[u8]) {
26 let hmac_key = hmac::Key::new(convert_digest_to_hmac_alg(hashalg), secret);
27
28 // A(1)
29 let mut current_a = hmac::sign(&hmac_key, seed);
30
31 let mut offs = 0;
32
33 while offs < out.len() {
34 // P_hash[i] = HMAC_hash(secret, A(i) + seed)
35 let p_term = concat_sign(&hmac_key, current_a.as_ref(), seed);
36 offs += out[offs..]
37 .as_mut()
38 .write(p_term.as_ref())
39 .unwrap();
40
41 // A(i+1) = HMAC_hash(secret, A(i))
42 current_a = hmac::sign(&hmac_key, current_a.as_ref());
43 }
44 }
45
concat(a: &[u8], b: &[u8]) -> Vec<u8>46 fn concat(a: &[u8], b: &[u8]) -> Vec<u8> {
47 let mut ret = Vec::new();
48 ret.extend_from_slice(a);
49 ret.extend_from_slice(b);
50 ret
51 }
52
prf( out: &mut [u8], hashalg: &'static digest::Algorithm, secret: &[u8], label: &[u8], seed: &[u8], )53 pub fn prf(
54 out: &mut [u8],
55 hashalg: &'static digest::Algorithm,
56 secret: &[u8],
57 label: &[u8],
58 seed: &[u8],
59 ) {
60 let joined_seed = concat(label, seed);
61 p(out, hashalg, secret, &joined_seed);
62 }
63
64 #[cfg(test)]
65 mod tests {
66 use ring::digest::{SHA256, SHA512};
67
68 #[test]
check_sha256()69 fn check_sha256() {
70 let secret = b"\x9b\xbe\x43\x6b\xa9\x40\xf0\x17\xb1\x76\x52\x84\x9a\x71\xdb\x35";
71 let seed = b"\xa0\xba\x9f\x93\x6c\xda\x31\x18\x27\xa6\xf7\x96\xff\xd5\x19\x8c";
72 let label = b"test label";
73 let expect = include_bytes!("testdata/prf-result.1.bin");
74 let mut output = [0u8; 100];
75
76 super::prf(&mut output, &SHA256, secret, label, seed);
77 assert_eq!(expect.len(), output.len());
78 assert_eq!(expect.to_vec(), output.to_vec());
79 }
80
81 #[test]
check_sha512()82 fn check_sha512() {
83 let secret = b"\xb0\x32\x35\x23\xc1\x85\x35\x99\x58\x4d\x88\x56\x8b\xbb\x05\xeb";
84 let seed = b"\xd4\x64\x0e\x12\xe4\xbc\xdb\xfb\x43\x7f\x03\xe6\xae\x41\x8e\xe5";
85 let label = b"test label";
86 let expect = include_bytes!("testdata/prf-result.2.bin");
87 let mut output = [0u8; 196];
88
89 super::prf(&mut output, &SHA512, secret, label, seed);
90 assert_eq!(expect.len(), output.len());
91 assert_eq!(expect.to_vec(), output.to_vec());
92 }
93 }
94