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use std::{
future::Future,
io::{Error as IoError, ErrorKind as IoErrorKind},
pin::Pin,
sync::Arc,
task::Poll,
};
use anyhow::{ensure, Context, Result as AnyhowResult};
use async_lock::RwLock;
use futures::{future::poll_fn, AsyncRead, AsyncReadExt, AsyncWrite, AsyncWriteExt};
use hotshot_types::traits::{
election::Membership,
node_implementation::{ConsensusTime, NodeType},
signature_key::SignatureKey,
};
use libp2p::{
core::{
muxing::StreamMuxerExt,
transport::{DialOpts, TransportEvent},
StreamMuxer,
},
identity::PeerId,
Transport,
};
use pin_project::pin_project;
use serde::{Deserialize, Serialize};
use tokio::time::timeout;
use tracing::warn;
/// The maximum size of an authentication message. This is used to prevent
/// DoS attacks by sending large messages.
const MAX_AUTH_MESSAGE_SIZE: usize = 1024;
/// The timeout for the authentication handshake. This is used to prevent
/// attacks that keep connections open indefinitely by half-finishing the
/// handshake.
const AUTH_HANDSHAKE_TIMEOUT: std::time::Duration = std::time::Duration::from_secs(5);
/// A wrapper for a `Transport` that bidirectionally authenticates connections
/// by performing a handshake that checks if the remote peer is present in the
/// stake table.
#[pin_project]
pub struct StakeTableAuthentication<T: Transport, Types: NodeType, C: StreamMuxer + Unpin> {
#[pin]
/// The underlying transport we are wrapping
pub inner: T,
/// The stake table we check against to authenticate connections
pub stake_table: Arc<Option<Arc<RwLock<Types::Membership>>>>,
/// A pre-signed message that we send to the remote peer for authentication
pub auth_message: Arc<Option<Vec<u8>>>,
/// Phantom data for the connection type
pd: std::marker::PhantomData<C>,
}
/// A type alias for the future that upgrades a connection to perform the authentication handshake
type UpgradeFuture<T> =
Pin<Box<dyn Future<Output = Result<<T as Transport>::Output, <T as Transport>::Error>> + Send>>;
impl<T: Transport, Types: NodeType, C: StreamMuxer + Unpin> StakeTableAuthentication<T, Types, C> {
/// Create a new `StakeTableAuthentication` transport that wraps the given transport
/// and authenticates connections against the stake table.
pub fn new(
inner: T,
stake_table: Option<Arc<RwLock<Types::Membership>>>,
auth_message: Option<Vec<u8>>,
) -> Self {
Self {
inner,
stake_table: Arc::from(stake_table),
auth_message: Arc::from(auth_message),
pd: std::marker::PhantomData,
}
}
/// Prove to the remote peer that we are in the stake table by sending
/// them our authentication message.
///
/// # Errors
/// - If we fail to write the message to the stream
pub async fn authenticate_with_remote_peer<W: AsyncWrite + Unpin>(
stream: &mut W,
auth_message: Arc<Option<Vec<u8>>>,
) -> AnyhowResult<()> {
// If we have an auth message, send it to the remote peer, prefixed with
// the message length
if let Some(auth_message) = auth_message.as_ref() {
// Write the length-delimited message
write_length_delimited(stream, auth_message).await?;
}
Ok(())
}
/// Verify that the remote peer is:
/// - In the stake table
/// - Sending us a valid authentication message
/// - Sending us a valid signature
/// - Matching the peer ID we expect
///
/// # Errors
/// If the peer fails verification. This can happen if:
/// - We fail to read the message from the stream
/// - The message is too large
/// - The message is invalid
/// - The peer is not in the stake table
/// - The signature is invalid
pub async fn verify_peer_authentication<R: AsyncReadExt + Unpin>(
stream: &mut R,
stake_table: Arc<Option<Arc<RwLock<Types::Membership>>>>,
required_peer_id: &PeerId,
) -> AnyhowResult<()> {
// If we have a stake table, check if the remote peer is in it
if let Some(stake_table) = stake_table.as_ref() {
// Read the length-delimited message from the remote peer
let message = read_length_delimited(stream, MAX_AUTH_MESSAGE_SIZE).await?;
// Deserialize the authentication message
let auth_message: AuthMessage<Types::SignatureKey> = bincode::deserialize(&message)
.with_context(|| "Failed to deserialize auth message")?;
// Verify the signature on the public keys
let public_key = auth_message
.validate()
.with_context(|| "Failed to verify authentication message")?;
// Deserialize the `PeerId`
let peer_id = PeerId::from_bytes(&auth_message.peer_id_bytes)
.with_context(|| "Failed to deserialize peer ID")?;
// Verify that the peer ID is the same as the remote peer
if peer_id != *required_peer_id {
return Err(anyhow::anyhow!("Peer ID mismatch"));
}
// Check if the public key is in the stake table
if !stake_table
.read()
.await
.has_stake(&public_key, Types::Epoch::new(0))
{
return Err(anyhow::anyhow!("Peer not in stake table"));
}
}
Ok(())
}
/// Wrap the supplied future in an upgrade that performs the authentication handshake.
///
/// `outgoing` is a boolean that indicates if the connection is incoming or outgoing.
/// This is needed because the flow of the handshake is different for each.
fn gen_handshake<F: Future<Output = Result<T::Output, T::Error>> + Send + 'static>(
original_future: F,
outgoing: bool,
stake_table: Arc<Option<Arc<RwLock<Types::Membership>>>>,
auth_message: Arc<Option<Vec<u8>>>,
) -> UpgradeFuture<T>
where
T::Error: From<<C as StreamMuxer>::Error> + From<IoError>,
T::Output: AsOutput<C> + Send,
C::Substream: Unpin + Send,
{
// Create a new upgrade that performs the authentication handshake on top
Box::pin(async move {
// Wait for the original future to resolve
let mut stream = original_future.await?;
// Time out the authentication block
timeout(AUTH_HANDSHAKE_TIMEOUT, async {
// Open a substream for the handshake.
// The handshake order depends on whether the connection is incoming or outgoing.
let mut substream = if outgoing {
poll_fn(|cx| stream.as_connection().poll_outbound_unpin(cx)).await?
} else {
poll_fn(|cx| stream.as_connection().poll_inbound_unpin(cx)).await?
};
if outgoing {
// If the connection is outgoing, authenticate with the remote peer first
Self::authenticate_with_remote_peer(&mut substream, auth_message)
.await
.map_err(|e| {
warn!("Failed to authenticate with remote peer: {:?}", e);
IoError::new(IoErrorKind::Other, e)
})?;
// Verify the remote peer's authentication
Self::verify_peer_authentication(
&mut substream,
stake_table,
stream.as_peer_id(),
)
.await
.map_err(|e| {
warn!("Failed to verify remote peer: {:?}", e);
IoError::new(IoErrorKind::Other, e)
})?;
} else {
// If it is incoming, verify the remote peer's authentication first
Self::verify_peer_authentication(
&mut substream,
stake_table,
stream.as_peer_id(),
)
.await
.map_err(|e| {
warn!("Failed to verify remote peer: {:?}", e);
IoError::new(IoErrorKind::Other, e)
})?;
// Authenticate with the remote peer
Self::authenticate_with_remote_peer(&mut substream, auth_message)
.await
.map_err(|e| {
warn!("Failed to authenticate with remote peer: {:?}", e);
IoError::new(IoErrorKind::Other, e)
})?;
}
Ok(stream)
})
.await
.map_err(|e| {
warn!("Timed out performing authentication handshake: {:?}", e);
IoError::new(IoErrorKind::TimedOut, e)
})?
})
}
}
/// The deserialized form of an authentication message that is sent to the remote peer
#[derive(Clone, Serialize, Deserialize)]
struct AuthMessage<S: SignatureKey> {
/// The encoded (stake table) public key of the sender. This, along with the peer ID, is
/// signed. It is still encoded here to enable easy verification.
public_key_bytes: Vec<u8>,
/// The encoded peer ID of the sender. This is appended to the public key before signing.
/// It is still encoded here to enable easy verification.
peer_id_bytes: Vec<u8>,
/// The signature on the public key
signature: S::PureAssembledSignatureType,
}
impl<S: SignatureKey> AuthMessage<S> {
/// Validate the signature on the public key and return it if valid
pub fn validate(&self) -> AnyhowResult<S> {
// Deserialize the stake table public key
let public_key = S::from_bytes(&self.public_key_bytes)
.with_context(|| "Failed to deserialize public key")?;
// Reconstruct the signed message from the public key and peer ID
let mut signed_message = public_key.to_bytes();
signed_message.extend(self.peer_id_bytes.clone());
// Check if the signature is valid across both
if !public_key.validate(&self.signature, &signed_message) {
return Err(anyhow::anyhow!("Invalid signature"));
}
Ok(public_key)
}
}
/// Create an sign an authentication message to be sent to the remote peer
///
/// # Errors
/// - If we fail to sign the public key
/// - If we fail to serialize the authentication message
pub fn construct_auth_message<S: SignatureKey + 'static>(
public_key: &S,
peer_id: &PeerId,
private_key: &S::PrivateKey,
) -> AnyhowResult<Vec<u8>> {
// Serialize the stake table public key
let mut public_key_bytes = public_key.to_bytes();
// Serialize the peer ID and append it
let peer_id_bytes = peer_id.to_bytes();
public_key_bytes.extend_from_slice(&peer_id_bytes);
// Sign our public key
let signature =
S::sign(private_key, &public_key_bytes).with_context(|| "Failed to sign public key")?;
// Create the auth message
let auth_message = AuthMessage::<S> {
public_key_bytes,
peer_id_bytes,
signature,
};
// Serialize the auth message
bincode::serialize(&auth_message).with_context(|| "Failed to serialize auth message")
}
impl<T: Transport, Types: NodeType, C: StreamMuxer + Unpin> Transport
for StakeTableAuthentication<T, Types, C>
where
T::Dial: Future<Output = Result<T::Output, T::Error>> + Send + 'static,
T::ListenerUpgrade: Send + 'static,
T::Output: AsOutput<C> + Send,
T::Error: From<<C as StreamMuxer>::Error> + From<IoError>,
C::Substream: Unpin + Send,
{
// `Dial` is for connecting out, `ListenerUpgrade` is for accepting incoming connections
type Dial = Pin<Box<dyn Future<Output = Result<T::Output, T::Error>> + Send>>;
type ListenerUpgrade = Pin<Box<dyn Future<Output = Result<T::Output, T::Error>> + Send>>;
// These are just passed through
type Output = T::Output;
type Error = T::Error;
/// Dial a remote peer. This function is changed to perform an authentication handshake
/// on top.
fn dial(
&mut self,
addr: libp2p::Multiaddr,
opts: DialOpts,
) -> Result<Self::Dial, libp2p::TransportError<Self::Error>> {
// Perform the inner dial
let res = self.inner.dial(addr, opts);
// Clone the necessary fields
let auth_message = Arc::clone(&self.auth_message);
let stake_table = Arc::clone(&self.stake_table);
// If the dial was successful, perform the authentication handshake on top
match res {
Ok(dial) => Ok(Self::gen_handshake(dial, true, stake_table, auth_message)),
Err(err) => Err(err),
}
}
/// This function is where we perform the authentication handshake for _incoming_ connections.
/// The flow in this case is the reverse of the `dial` function: we first verify the remote peer's
/// authentication, and then authenticate with them.
fn poll(
mut self: std::pin::Pin<&mut Self>,
cx: &mut std::task::Context<'_>,
) -> std::task::Poll<libp2p::core::transport::TransportEvent<Self::ListenerUpgrade, Self::Error>>
{
match self.as_mut().project().inner.poll(cx) {
Poll::Ready(event) => Poll::Ready(match event {
// If we have an incoming connection, we need to perform the authentication handshake
TransportEvent::Incoming {
listener_id,
upgrade,
local_addr,
send_back_addr,
} => {
// Clone the necessary fields
let auth_message = Arc::clone(&self.auth_message);
let stake_table = Arc::clone(&self.stake_table);
// Generate the handshake upgrade future (inbound)
let auth_upgrade =
Self::gen_handshake(upgrade, false, stake_table, auth_message);
// Return the new event
TransportEvent::Incoming {
listener_id,
upgrade: auth_upgrade,
local_addr,
send_back_addr,
}
}
// We need to re-map the other events because we changed the type of the upgrade
TransportEvent::AddressExpired {
listener_id,
listen_addr,
} => TransportEvent::AddressExpired {
listener_id,
listen_addr,
},
TransportEvent::ListenerClosed {
listener_id,
reason,
} => TransportEvent::ListenerClosed {
listener_id,
reason,
},
TransportEvent::ListenerError { listener_id, error } => {
TransportEvent::ListenerError { listener_id, error }
}
TransportEvent::NewAddress {
listener_id,
listen_addr,
} => TransportEvent::NewAddress {
listener_id,
listen_addr,
},
}),
Poll::Pending => Poll::Pending,
}
}
/// The below functions just pass through to the inner transport, but we had
/// to define them
fn remove_listener(&mut self, id: libp2p::core::transport::ListenerId) -> bool {
self.inner.remove_listener(id)
}
fn listen_on(
&mut self,
id: libp2p::core::transport::ListenerId,
addr: libp2p::Multiaddr,
) -> Result<(), libp2p::TransportError<Self::Error>> {
self.inner.listen_on(id, addr)
}
}
/// A helper trait that allows us to access the underlying connection
/// and `PeerId` from a transport output
trait AsOutput<C: StreamMuxer + Unpin> {
/// Get a mutable reference to the underlying connection
fn as_connection(&mut self) -> &mut C;
/// Get a mutable reference to the underlying `PeerId`
fn as_peer_id(&mut self) -> &mut PeerId;
}
/// The implementation of the `AsConnection` trait for a tuple of a `PeerId`
/// and a connection.
impl<C: StreamMuxer + Unpin> AsOutput<C> for (PeerId, C) {
/// Get a mutable reference to the underlying connection
fn as_connection(&mut self) -> &mut C {
&mut self.1
}
/// Get a mutable reference to the underlying `PeerId`
fn as_peer_id(&mut self) -> &mut PeerId {
&mut self.0
}
}
/// A helper function to read a length-delimited message from a stream. Takes into
/// account the maximum message size.
///
/// # Errors
/// - If the message is too big
/// - If we fail to read from the stream
pub async fn read_length_delimited<S: AsyncRead + Unpin>(
stream: &mut S,
max_size: usize,
) -> AnyhowResult<Vec<u8>> {
// Receive the first 8 bytes of the message, which is the length
let mut len_bytes = [0u8; 4];
stream
.read_exact(&mut len_bytes)
.await
.with_context(|| "Failed to read message length")?;
// Parse the length of the message as a `u32`
let len = usize::try_from(u32::from_be_bytes(len_bytes))?;
// Quit if the message is too large
ensure!(len <= max_size, "Message too large");
// Read the actual message
let mut message = vec![0u8; len];
stream
.read_exact(&mut message)
.await
.with_context(|| "Failed to read message")?;
Ok(message)
}
/// A helper function to write a length-delimited message to a stream.
///
/// # Errors
/// - If we fail to write to the stream
pub async fn write_length_delimited<S: AsyncWrite + Unpin>(
stream: &mut S,
message: &[u8],
) -> AnyhowResult<()> {
// Write the length of the message
stream
.write_all(&u32::try_from(message.len())?.to_be_bytes())
.await
.with_context(|| "Failed to write message length")?;
// Write the actual message
stream
.write_all(message)
.await
.with_context(|| "Failed to write message")?;
Ok(())
}
#[cfg(test)]
mod test {
use std::sync::Arc;
use hotshot_example_types::node_types::TestTypes;
use hotshot_types::{
light_client::StateVerKey, signature_key::BLSPubKey, traits::signature_key::SignatureKey,
PeerConfig,
};
use libp2p::{core::transport::dummy::DummyTransport, quic::Connection};
use rand::Rng;
use super::*;
/// A mock type to help with readability
type MockStakeTableAuth = StakeTableAuthentication<DummyTransport, TestTypes, Connection>;
// Helper macro for generating a new identity and authentication message
macro_rules! new_identity {
() => {{
// Gen a new seed
let seed = rand::rngs::OsRng.gen::<[u8; 32]>();
// Create a new keypair
let keypair = BLSPubKey::generated_from_seed_indexed(seed, 1337);
// Create a peer ID
let peer_id = libp2p::identity::Keypair::generate_ed25519()
.public()
.to_peer_id();
// Construct an authentication message
let auth_message =
super::construct_auth_message(&keypair.0, &peer_id, &keypair.1).unwrap();
(keypair, peer_id, auth_message)
}};
}
// Helper macro to generator a cursor from a length-delimited message
macro_rules! cursor_from {
($auth_message:expr) => {{
let mut stream = futures::io::Cursor::new(vec![]);
write_length_delimited(&mut stream, &$auth_message)
.await
.expect("Failed to write message");
stream.set_position(0);
stream
}};
}
/// Test valid construction and verification of an authentication message
#[test]
fn signature_verify() {
// Create a new identity
let (_, _, auth_message) = new_identity!();
// Verify the authentication message
let public_key = super::AuthMessage::<BLSPubKey>::validate(
&bincode::deserialize(&auth_message).unwrap(),
);
assert!(public_key.is_ok());
}
/// Test invalid construction and verification of an authentication message with
/// an invalid public key. This ensures we are signing over it correctly.
#[test]
fn signature_verify_invalid_public_key() {
// Create a new identity
let (_, _, auth_message) = new_identity!();
// Deserialize the authentication message
let mut auth_message: super::AuthMessage<BLSPubKey> =
bincode::deserialize(&auth_message).unwrap();
// Change the public key
auth_message.public_key_bytes[0] ^= 0x01;
// Serialize the message again
let auth_message = bincode::serialize(&auth_message).unwrap();
// Verify the authentication message
let public_key = super::AuthMessage::<BLSPubKey>::validate(
&bincode::deserialize(&auth_message).unwrap(),
);
assert!(public_key.is_err());
}
/// Test invalid construction and verification of an authentication message with
/// an invalid peer ID. This ensures we are signing over it correctly.
#[test]
fn signature_verify_invalid_peer_id() {
// Create a new identity
let (_, _, auth_message) = new_identity!();
// Deserialize the authentication message
let mut auth_message: super::AuthMessage<BLSPubKey> =
bincode::deserialize(&auth_message).unwrap();
// Change the peer ID
auth_message.peer_id_bytes[0] ^= 0x01;
// Serialize the message again
let auth_message = bincode::serialize(&auth_message).unwrap();
// Verify the authentication message
let public_key = super::AuthMessage::<BLSPubKey>::validate(
&bincode::deserialize(&auth_message).unwrap(),
);
assert!(public_key.is_err());
}
#[tokio::test(flavor = "multi_thread")]
async fn valid_authentication() {
// Create a new identity
let (keypair, peer_id, auth_message) = new_identity!();
// Create a stream and write the message to it
let mut stream = cursor_from!(auth_message);
// Create a stake table with the key
let peer_config = PeerConfig {
stake_table_entry: keypair.0.stake_table_entry(1),
state_ver_key: StateVerKey::default(),
};
let stake_table =
<TestTypes as NodeType>::Membership::new(vec![peer_config.clone()], vec![peer_config]);
// Verify the authentication message
let result = MockStakeTableAuth::verify_peer_authentication(
&mut stream,
Arc::new(Some(Arc::new(RwLock::new(stake_table)))),
&peer_id,
)
.await;
assert!(
result.is_ok(),
"Should have passed authentication but did not"
);
}
#[tokio::test(flavor = "multi_thread")]
async fn key_not_in_stake_table() {
// Create a new identity
let (_, peer_id, auth_message) = new_identity!();
// Create a stream and write the message to it
let mut stream = cursor_from!(auth_message);
// Create an empty stake table
let stake_table = Arc::new(RwLock::new(<TestTypes as NodeType>::Membership::new(
vec![],
vec![],
)));
// Verify the authentication message
let result = MockStakeTableAuth::verify_peer_authentication(
&mut stream,
Arc::new(Some(stake_table)),
&peer_id,
)
.await;
// Make sure it errored for the right reason
assert!(
result
.expect_err("Should have failed authentication but did not")
.to_string()
.contains("Peer not in stake table"),
"Did not fail with the correct error"
);
}
#[tokio::test(flavor = "multi_thread")]
async fn peer_id_mismatch() {
// Create a new identity and authentication message
let (keypair, _, auth_message) = new_identity!();
// Create a second (malicious) identity
let (_, malicious_peer_id, _) = new_identity!();
// Create a stream and write the message to it
let mut stream = cursor_from!(auth_message);
// Create a stake table with the key
let peer_config = PeerConfig {
stake_table_entry: keypair.0.stake_table_entry(1),
state_ver_key: StateVerKey::default(),
};
let stake_table = Arc::new(RwLock::new(<TestTypes as NodeType>::Membership::new(
vec![peer_config.clone()],
vec![peer_config],
)));
// Check against the malicious peer ID
let result = MockStakeTableAuth::verify_peer_authentication(
&mut stream,
Arc::new(Some(stake_table)),
&malicious_peer_id,
)
.await;
// Make sure it errored for the right reason
assert!(
result
.expect_err("Should have failed authentication but did not")
.to_string()
.contains("Peer ID mismatch"),
"Did not fail with the correct error"
);
}
#[tokio::test(flavor = "multi_thread")]
async fn read_and_write_length_delimited() {
// Create a message
let message = b"Hello, world!";
// Write the message to a buffer
let mut buffer = Vec::new();
write_length_delimited(&mut buffer, message).await.unwrap();
// Read the message from the buffer
let read_message = read_length_delimited(&mut buffer.as_slice(), 1024)
.await
.unwrap();
// Check if the messages are the same
assert_eq!(message, read_message.as_slice());
}
}