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Random number generator split
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@nyonson
nyonson committed Mar 19, 2024
1 parent d872260 commit 5ed951e
Showing 1 changed file with 65 additions and 15 deletions.
80 changes: 65 additions & 15 deletions src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -371,10 +371,9 @@ impl FSChaCha20 {
}
}

fn gen_key() -> Result<SecretKey, secp256k1::Error> {
let mut rnd = rand::thread_rng();
fn gen_key(rng: &mut impl Rng) -> Result<SecretKey, secp256k1::Error> {
let mut buffer: Vec<u8> = vec![0; 32];
rnd.fill(&mut buffer[..]);
rng.fill(&mut buffer[..]);
let sk = SecretKey::from_slice(&buffer)?;
Ok(sk)
}
Expand All @@ -386,8 +385,7 @@ fn new_elligator_swift(sk: SecretKey) -> ElligatorSwift {
ElligatorSwift::from_pubkey(pk)
}

fn gen_garbage(garbage_len: u32) -> Vec<u8> {
let mut rng = rand::thread_rng();
fn gen_garbage(garbage_len: u32, rng: &mut impl Rng) -> Vec<u8> {
let buffer: Vec<u8> = (0..garbage_len).map(|_| rng.gen()).collect();
buffer
}
Expand Down Expand Up @@ -461,13 +459,37 @@ fn initialize_session_key_material(ikm: &[u8]) -> SessionKeyMaterial {
/// # Errors
///
/// Fails if their was an error generating the keypair.
#[cfg(feature = "std")]
pub fn initialize_v2_handshake(
garbage_len: Option<u32>,
) -> Result<InitiatorHandshake, secp256k1::Error> {
let sk = gen_key()?;
let mut rng = rand::thread_rng();
initialize_v2_handshake_with_rng(garbage_len, &mut rng)
}

/// Initialize a V2 transport handshake with a peer. The `InitiatorHandshake` contains a message ready to be sent over the wire,
/// and the information necessary for completing ECDH when the peer responds.
///
/// # Arguments
///
/// `garbage_len` - The length of the additional garbage to be sent along with the encoded public key.
/// `rng` - supplied Random Number Generator.
///
/// # Returns
///
/// A partial handshake.
///
/// # Errors
///
/// Fails if their was an error generating the keypair.
pub fn initialize_v2_handshake_with_rng(
garbage_len: Option<u32>,
rng: &mut impl Rng,
) -> Result<InitiatorHandshake, secp256k1::Error> {
let sk = gen_key(rng)?;
let es = new_elligator_swift(sk);
let garbage_len = garbage_len.unwrap_or(MAX_GARBAGE_LEN);
let garbage = gen_garbage(garbage_len);
let garbage = gen_garbage(garbage_len, rng);
let point = EcdhPoint {
secret_key: sk,
elligator_swift: es,
Expand All @@ -494,8 +516,31 @@ pub fn initialize_v2_handshake(
/// # Errors
///
/// Fails if the packet was not prepared properly.
#[cfg(feature = "std")]
pub fn receive_v2_handshake(
message: Vec<u8>,
) -> Result<ResponderHandshake, ResponderHandshakeError> {
let mut rng = rand::thread_rng();
receive_v2_handshake_with_rng(message, &mut rng)
}

/// Receive a V2 handshake over the wire. The `ResponderHandshake` contains the message ready to be sent over the wire and a struct for parsing packets.
///
/// # Arguments
///
/// `message` - The message received over the wire.
/// `rng` - Supplied Random Number Generator.
///
/// # Returns
///
/// A completed handshake containing a `PacketHandler`.
///
/// # Errors
///
/// Fails if the packet was not prepared properly.
pub fn receive_v2_handshake_with_rng(
message: Vec<u8>,
rng: &mut impl Rng,
) -> Result<ResponderHandshake, ResponderHandshakeError> {
let mut network_magic = NETWORK_MAGIC.to_vec();
let mut version_bytes = "version".as_bytes().to_vec();
Expand All @@ -508,7 +553,7 @@ pub fn receive_v2_handshake(
))
} else {
let mut response: Vec<u8> = Vec::new();
let sk = gen_key().map_err(ResponderHandshakeError::ECC)?;
let sk = gen_key(rng).map_err(ResponderHandshakeError::ECC)?;
let es = new_elligator_swift(sk);
response.extend(&es.to_array());
let elliswift_message = &message[..64];
Expand All @@ -519,7 +564,7 @@ pub fn receive_v2_handshake(
let session_keys = get_shared_secrets(theirs, es, sk, ElligatorSwiftParty::B);
let initiator_garbage = message[64..].to_vec();
let initiator_garbage_len = initiator_garbage.len() as u32;
let response_garbage = gen_garbage(initiator_garbage_len);
let response_garbage = gen_garbage(initiator_garbage_len, rng);
if initiator_garbage_len > MAX_GARBAGE_LEN {
return Err(ResponderHandshakeError::IncorrectMessage(
"Garbage length is too large.".to_string(),
Expand Down Expand Up @@ -661,7 +706,8 @@ mod tests {

#[test]
fn test_sec_keygen() {
gen_key().unwrap();
let mut rng = rand::thread_rng();
gen_key(&mut rng).unwrap();
}

#[test]
Expand Down Expand Up @@ -777,6 +823,7 @@ mod tests {

#[test]
fn test_fuzz_packets() {
let mut rng = rand::thread_rng();
let alice =
SecretKey::from_str("61062ea5071d800bbfd59e2e8b53d47d194b095ae5a4df04936b49772ef0d4d7")
.unwrap();
Expand All @@ -792,7 +839,7 @@ mod tests {
PacketHandler::new(session_keys.clone(), HandshakeRole::Initiator);
let mut bob_packet_handler = PacketHandler::new(session_keys, HandshakeRole::Responder);
for _ in 0..REKEY_INTERVAL + 100 {
let message = gen_garbage(4095);
let message = gen_garbage(4095, &mut rng);
let enc_packet = alice_packet_handler
.prepare_v2_packet(message.clone(), None, false)
.unwrap();
Expand All @@ -801,7 +848,7 @@ mod tests {
.unwrap();
let secret_message = dec_packet.first().unwrap().message.clone().unwrap();
assert_eq!(message, secret_message);
let message = gen_garbage(420);
let message = gen_garbage(420, &mut rng);
let enc_packet = bob_packet_handler
.prepare_v2_packet(message.clone(), None, false)
.unwrap();
Expand All @@ -815,6 +862,7 @@ mod tests {

#[test]
fn test_authenticated_garbage() {
let mut rng = rand::thread_rng();
let alice =
SecretKey::from_str("61062ea5071d800bbfd59e2e8b53d47d194b095ae5a4df04936b49772ef0d4d7")
.unwrap();
Expand All @@ -829,7 +877,7 @@ mod tests {
let mut alice_packet_handler =
PacketHandler::new(session_keys.clone(), HandshakeRole::Initiator);
let mut bob_packet_handler = PacketHandler::new(session_keys, HandshakeRole::Responder);
let auth_garbage = gen_garbage(200);
let auth_garbage = gen_garbage(200, &mut rng);
let enc_packet = alice_packet_handler
.prepare_v2_packet(Vec::new(), Some(auth_garbage.clone()), false)
.unwrap();
Expand Down Expand Up @@ -897,6 +945,7 @@ mod tests {

#[test]
fn test_fuzz_decode_multiple_messages() {
let mut rng = rand::thread_rng();
let handshake_init = initialize_v2_handshake(None).unwrap();
let mut handshake_response = receive_v2_handshake(handshake_init.message.clone()).unwrap();
let alice_completion =
Expand All @@ -911,7 +960,7 @@ mod tests {
let mut bob = handshake_response.packet_handler;
let mut message_to_bob = Vec::new();
for _ in 0..REKEY_INTERVAL + 100 {
let message = gen_garbage(420);
let message = gen_garbage(420, &mut rng);
let enc_packet = alice
.prepare_v2_packet(message.clone(), None, false)
.unwrap();
Expand All @@ -924,6 +973,7 @@ mod tests {

#[test]
fn test_vector_1() {
let mut rng = rand::thread_rng();
let alice =
SecretKey::from_str("61062ea5071d800bbfd59e2e8b53d47d194b095ae5a4df04936b49772ef0d4d7")
.unwrap();
Expand All @@ -938,7 +988,7 @@ mod tests {
let mut alice_packet_handler =
PacketHandler::new(session_keys.clone(), HandshakeRole::Initiator);
let mut bob_packet_handler = PacketHandler::new(session_keys, HandshakeRole::Responder);
let first = gen_garbage(100);
let first = gen_garbage(100, &mut rng);
let enc = alice_packet_handler
.prepare_v2_packet(first.clone(), None, false)
.unwrap();
Expand Down

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