1 use ring::hmac; 2 3 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 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 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 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] 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] 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