blob: 6796a2ac5978e052e6b9516b50d69ab521f4b430 [file] [log] [blame]
/// Key schedule maintenance for TLS1.3
use ring::{hmac, digest, hkdf};
use crate::msgs::codec::Codec;
use crate::error::TLSError;
/// The kinds of secret we can extract from `KeySchedule`.
#[derive(Debug, Clone, Copy, PartialEq)]
pub enum SecretKind {
ResumptionPSKBinderKey,
ClientEarlyTrafficSecret,
ClientHandshakeTrafficSecret,
ServerHandshakeTrafficSecret,
ClientApplicationTrafficSecret,
ServerApplicationTrafficSecret,
ExporterMasterSecret,
ResumptionMasterSecret,
DerivedSecret,
}
impl SecretKind {
fn to_bytes(&self) -> &'static [u8] {
match *self {
SecretKind::ResumptionPSKBinderKey => b"res binder",
SecretKind::ClientEarlyTrafficSecret => b"c e traffic",
SecretKind::ClientHandshakeTrafficSecret => b"c hs traffic",
SecretKind::ServerHandshakeTrafficSecret => b"s hs traffic",
SecretKind::ClientApplicationTrafficSecret => b"c ap traffic",
SecretKind::ServerApplicationTrafficSecret => b"s ap traffic",
SecretKind::ExporterMasterSecret => b"exp master",
SecretKind::ResumptionMasterSecret => b"res master",
SecretKind::DerivedSecret => b"derived",
}
}
}
/// This is the TLS1.3 key schedule. It stores the current secret,
/// the type of hash, plus the two current traffic keys which form their
/// own lineage of keys over successive key updates.
pub struct KeySchedule {
current: hmac::SigningKey,
need_derive_for_extract: bool,
hash: &'static digest::Algorithm,
hash_of_empty_message: [u8; digest::MAX_OUTPUT_LEN],
pub current_client_traffic_secret: Vec<u8>,
pub current_server_traffic_secret: Vec<u8>,
pub current_exporter_secret: Vec<u8>,
}
impl KeySchedule {
pub fn new(hash: &'static digest::Algorithm) -> KeySchedule {
let zeroes = [0u8; digest::MAX_OUTPUT_LEN];
let mut empty_hash = [0u8; digest::MAX_OUTPUT_LEN];
empty_hash[..hash.output_len]
.clone_from_slice(digest::digest(hash, &[]).as_ref());
KeySchedule {
current: hmac::SigningKey::new(hash, &zeroes[..hash.output_len]),
need_derive_for_extract: false,
hash,
hash_of_empty_message: empty_hash,
current_server_traffic_secret: Vec::new(),
current_client_traffic_secret: Vec::new(),
current_exporter_secret: Vec::new(),
}
}
pub fn get_hash_of_empty_message(&self) -> &[u8] {
&self.hash_of_empty_message[..self.hash.output_len]
}
/// Input the empty secret.
pub fn input_empty(&mut self) {
let zeroes = [0u8; digest::MAX_OUTPUT_LEN];
let hash_len = self.hash.output_len;
self.input_secret(&zeroes[..hash_len]);
}
/// Input the given secret.
pub fn input_secret(&mut self, secret: &[u8]) {
if self.need_derive_for_extract {
let derived = self.derive(SecretKind::DerivedSecret,
self.get_hash_of_empty_message());
self.current = hmac::SigningKey::new(self.hash, &derived);
}
self.need_derive_for_extract = true;
let new = hkdf::extract(&self.current, secret);
self.current = new
}
/// Derive a secret of given `kind`, using current handshake hash `hs_hash`.
pub fn derive(&self, kind: SecretKind, hs_hash: &[u8]) -> Vec<u8> {
debug_assert_eq!(hs_hash.len(), self.hash.output_len);
_hkdf_expand_label_vec(&self.current,
kind.to_bytes(),
hs_hash,
self.hash.output_len)
}
/// Return the current traffic secret, of given `kind`.
fn current_traffic_secret(&self, kind: SecretKind) -> &[u8] {
match kind {
SecretKind::ServerHandshakeTrafficSecret |
SecretKind::ServerApplicationTrafficSecret => &self.current_server_traffic_secret,
SecretKind::ClientEarlyTrafficSecret |
SecretKind::ClientHandshakeTrafficSecret |
SecretKind::ClientApplicationTrafficSecret => &self.current_client_traffic_secret,
_ => unreachable!(),
}
}
/// Sign the finished message consisting of `hs_hash` using the current
/// traffic secret.
pub fn sign_finish(&self, kind: SecretKind, hs_hash: &[u8]) -> Vec<u8> {
let base_key = self.current_traffic_secret(kind);
self.sign_verify_data(base_key, hs_hash)
}
/// Sign the finished message consisting of `hs_hash` using the key material
/// `base_key`.
pub fn sign_verify_data(&self, base_key: &[u8], hs_hash: &[u8]) -> Vec<u8> {
debug_assert_eq!(hs_hash.len(), self.hash.output_len);
let hmac_key = _hkdf_expand_label_vec(&hmac::SigningKey::new(self.hash, base_key),
b"finished",
&[],
self.hash.output_len);
hmac::sign(&hmac::SigningKey::new(self.hash, &hmac_key), hs_hash)
.as_ref()
.to_vec()
}
/// Derive the next application traffic secret of given `kind`, returning
/// it.
pub fn derive_next(&self, kind: SecretKind) -> Vec<u8> {
let base_key = self.current_traffic_secret(kind);
_hkdf_expand_label_vec(&hmac::SigningKey::new(self.hash, base_key),
b"traffic upd",
&[],
self.hash.output_len)
}
/// Derive the PSK to use given a resumption_master_secret and
/// ticket_nonce.
pub fn derive_ticket_psk(&self, rms: &[u8], nonce: &[u8]) -> Vec<u8> {
_hkdf_expand_label_vec(&hmac::SigningKey::new(self.hash, rms),
b"resumption",
nonce,
self.hash.output_len)
}
pub fn export_keying_material(&self, out: &mut [u8],
label: &[u8],
context: Option<&[u8]>) -> Result<(), TLSError> {
if self.current_exporter_secret.is_empty() {
return Err(TLSError::HandshakeNotComplete);
}
let h_empty = digest::digest(self.hash, &[]);
let mut secret = [0u8; digest::MAX_OUTPUT_LEN];
_hkdf_expand_label(&mut secret[..self.hash.output_len],
&hmac::SigningKey::new(self.hash,
&self.current_exporter_secret),
label,
h_empty.as_ref());
let mut h_context = [0u8; digest::MAX_OUTPUT_LEN];
h_context[..self.hash.output_len]
.clone_from_slice(digest::digest(self.hash,
context.unwrap_or(&[]))
.as_ref());
_hkdf_expand_label(out,
&hmac::SigningKey::new(self.hash, &secret[..self.hash.output_len]),
b"exporter",
&h_context[..self.hash.output_len]);
Ok(())
}
}
fn _hkdf_expand_label_vec(secret: &hmac::SigningKey,
label: &[u8],
context: &[u8],
len: usize) -> Vec<u8> {
let mut v = Vec::new();
v.resize(len, 0u8);
_hkdf_expand_label(&mut v,
secret,
label,
context);
v
}
fn _hkdf_expand_label(output: &mut [u8],
secret: &hmac::SigningKey,
label: &[u8],
context: &[u8]) {
let label_prefix = b"tls13 ";
let mut hkdflabel = Vec::new();
(output.len() as u16).encode(&mut hkdflabel);
((label.len() + label_prefix.len()) as u8).encode(&mut hkdflabel);
hkdflabel.extend_from_slice(label_prefix);
hkdflabel.extend_from_slice(label);
(context.len() as u8).encode(&mut hkdflabel);
hkdflabel.extend_from_slice(context);
hkdf::expand(secret, &hkdflabel, output)
}
pub fn derive_traffic_key(hash: &'static digest::Algorithm, secret: &[u8], len: usize) -> Vec<u8> {
_hkdf_expand_label_vec(&hmac::SigningKey::new(hash, secret), b"key", &[], len)
}
pub fn derive_traffic_iv(hash: &'static digest::Algorithm, secret: &[u8], len: usize) -> Vec<u8> {
_hkdf_expand_label_vec(&hmac::SigningKey::new(hash, secret), b"iv", &[], len)
}
#[cfg(test)]
mod test {
use super::{KeySchedule, SecretKind, derive_traffic_key, derive_traffic_iv};
use ring::digest;
#[test]
fn smoke_test() {
let fake_handshake_hash = [0u8; 32];
let mut ks = KeySchedule::new(&digest::SHA256);
ks.input_empty(); // no PSK
ks.derive(SecretKind::ResumptionPSKBinderKey, &fake_handshake_hash);
ks.input_secret(&[1u8, 2u8, 3u8, 4u8]);
ks.derive(SecretKind::ClientHandshakeTrafficSecret,
&fake_handshake_hash);
ks.derive(SecretKind::ServerHandshakeTrafficSecret,
&fake_handshake_hash);
ks.input_empty();
ks.derive(SecretKind::ClientApplicationTrafficSecret,
&fake_handshake_hash);
ks.derive(SecretKind::ServerApplicationTrafficSecret,
&fake_handshake_hash);
ks.derive(SecretKind::ResumptionMasterSecret, &fake_handshake_hash);
}
#[test]
fn test_vectors() {
/* These test vectors generated with OpenSSL. */
let hs_start_hash = [
0xec, 0x14, 0x7a, 0x06, 0xde, 0xa3, 0xc8, 0x84, 0x6c, 0x02, 0xb2, 0x23, 0x8e,
0x41, 0xbd, 0xdc, 0x9d, 0x89, 0xf9, 0xae, 0xa1, 0x7b, 0x5e, 0xfd, 0x4d, 0x74,
0x82, 0xaf, 0x75, 0x88, 0x1c, 0x0a
];
let hs_full_hash = [
0x75, 0x1a, 0x3d, 0x4a, 0x14, 0xdf, 0xab, 0xeb, 0x68, 0xe9, 0x2c, 0xa5, 0x91,
0x8e, 0x24, 0x08, 0xb9, 0xbc, 0xb0, 0x74, 0x89, 0x82, 0xec, 0x9c, 0x32, 0x30,
0xac, 0x30, 0xbb, 0xeb, 0x23, 0xe2
];
let ecdhe_secret = [
0xe7, 0xb8, 0xfe, 0xf8, 0x90, 0x3b, 0x52, 0x0c, 0xb9, 0xa1, 0x89, 0x71, 0xb6,
0x9d, 0xd4, 0x5d, 0xca, 0x53, 0xce, 0x2f, 0x12, 0xbf, 0x3b, 0xef, 0x93, 0x15,
0xe3, 0x12, 0x71, 0xdf, 0x4b, 0x40
];
let client_hts = [
0x61, 0x7b, 0x35, 0x07, 0x6b, 0x9d, 0x0e, 0x08, 0xcf, 0x73, 0x1d, 0x94, 0xa8,
0x66, 0x14, 0x78, 0x41, 0x09, 0xef, 0x25, 0x55, 0x51, 0x92, 0x1d, 0xd4, 0x6e,
0x04, 0x01, 0x35, 0xcf, 0x46, 0xab
];
let client_hts_key = [
0x62, 0xd0, 0xdd, 0x00, 0xf6, 0x96, 0x19, 0xd3, 0xb8, 0x19, 0x3a, 0xb4, 0xa0,
0x95, 0x85, 0xa7
];
let client_hts_iv = [
0xff, 0xf7, 0x5d, 0xf5, 0xad, 0x35, 0xd5, 0xcb, 0x3c, 0x53, 0xf3, 0xa9
];
let server_hts = [
0xfc, 0xf7, 0xdf, 0xe6, 0x4f, 0xa2, 0xc0, 0x4f, 0x62, 0x35, 0x38, 0x7f, 0x43,
0x4e, 0x01, 0x42, 0x23, 0x36, 0xd9, 0xc0, 0x39, 0xde, 0x68, 0x47, 0xa0, 0xb9,
0xdd, 0xcf, 0x29, 0xa8, 0x87, 0x59
];
let server_hts_key = [
0x04, 0x67, 0xf3, 0x16, 0xa8, 0x05, 0xb8, 0xc4, 0x97, 0xee, 0x67, 0x04, 0x7b,
0xbc, 0xbc, 0x54
];
let server_hts_iv = [
0xde, 0x83, 0xa7, 0x3e, 0x9d, 0x81, 0x4b, 0x04, 0xc4, 0x8b, 0x78, 0x09
];
let client_ats = [
0xc1, 0x4a, 0x6d, 0x79, 0x76, 0xd8, 0x10, 0x2b, 0x5a, 0x0c, 0x99, 0x51, 0x49,
0x3f, 0xee, 0x87, 0xdc, 0xaf, 0xf8, 0x2c, 0x24, 0xca, 0xb2, 0x14, 0xe8, 0xbe,
0x71, 0xa8, 0x20, 0x6d, 0xbd, 0xa5
];
let client_ats_key = [
0xcc, 0x9f, 0x5f, 0x98, 0x0b, 0x5f, 0x10, 0x30, 0x6c, 0xba, 0xd7, 0xbe, 0x98,
0xd7, 0x57, 0x2e
];
let client_ats_iv = [
0xb8, 0x09, 0x29, 0xe8, 0xd0, 0x2c, 0x70, 0xf6, 0x11, 0x62, 0xed, 0x6b
];
let server_ats = [
0x2c, 0x90, 0x77, 0x38, 0xd3, 0xf8, 0x37, 0x02, 0xd1, 0xe4, 0x59, 0x8f, 0x48,
0x48, 0x53, 0x1d, 0x9f, 0x93, 0x65, 0x49, 0x1b, 0x9f, 0x7f, 0x52, 0xc8, 0x22,
0x29, 0x0d, 0x4c, 0x23, 0x21, 0x92
];
let server_ats_key = [
0x0c, 0xb2, 0x95, 0x62, 0xd8, 0xd8, 0x8f, 0x48, 0xb0, 0x2c, 0xbf, 0xbe, 0xd7,
0xe6, 0x2b, 0xb3
];
let server_ats_iv = [
0x0d, 0xb2, 0x8f, 0x98, 0x85, 0x86, 0xa1, 0xb7, 0xe4, 0xd5, 0xc6, 0x9c
];
let hash = &digest::SHA256;
let mut ks = KeySchedule::new(hash);
ks.input_empty();
ks.input_secret(&ecdhe_secret);
let got_client_hts = ks.derive(SecretKind::ClientHandshakeTrafficSecret,
&hs_start_hash);
assert_eq!(got_client_hts,
client_hts.to_vec());
assert_eq!(derive_traffic_key(hash, &got_client_hts, client_hts_key.len()),
client_hts_key.to_vec());
assert_eq!(derive_traffic_iv(hash, &got_client_hts, client_hts_iv.len()),
client_hts_iv.to_vec());
let got_server_hts = ks.derive(SecretKind::ServerHandshakeTrafficSecret,
&hs_start_hash);
assert_eq!(got_server_hts,
server_hts.to_vec());
assert_eq!(derive_traffic_key(hash, &got_server_hts, server_hts_key.len()),
server_hts_key.to_vec());
assert_eq!(derive_traffic_iv(hash, &got_server_hts, server_hts_iv.len()),
server_hts_iv.to_vec());
ks.input_empty();
let got_client_ats = ks.derive(SecretKind::ClientApplicationTrafficSecret,
&hs_full_hash);
assert_eq!(got_client_ats,
client_ats.to_vec());
assert_eq!(derive_traffic_key(hash, &got_client_ats, client_ats_key.len()),
client_ats_key.to_vec());
assert_eq!(derive_traffic_iv(hash, &got_client_ats, client_ats_iv.len()),
client_ats_iv.to_vec());
let got_server_ats = ks.derive(SecretKind::ServerApplicationTrafficSecret,
&hs_full_hash);
assert_eq!(got_server_ats,
server_ats.to_vec());
assert_eq!(derive_traffic_key(hash, &got_server_ats, server_ats_key.len()),
server_ats_key.to_vec());
assert_eq!(derive_traffic_iv(hash, &got_server_ats, server_ats_iv.len()),
server_ats_iv.to_vec());
}
}