Added initiation flood protection

src/handshake/device.rs

@@ -17,6 +17,8 @@ use super::peer::Peer;
 use super::ratelimiter::RateLimiter;
 use super::types::*;
 
+const MAX_PEER_PER_DEVICE: usize = 1 << 20;
+
 pub struct Device<T> {
     pub sk: StaticSecret,                   // static secret key
     pub pk: PublicKey,                      // static public key
@@ -59,21 +61,23 @@ where
     /// * `identifier` - Associated identifier which can be used to distinguish the peers
     pub fn add(&mut self, pk: PublicKey, identifier: T) -> Result<(), ConfigError> {
         // check that the pk is not added twice
-
         if let Some(_) = self.pk_map.get(pk.as_bytes()) {
             return Err(ConfigError::new("Duplicate public key"));
         };
 
         // check that the pk is not that of the device
-
         if *self.pk.as_bytes() == *pk.as_bytes() {
             return Err(ConfigError::new(
                 "Public key corresponds to secret key of interface",
             ));
         }
 
-        // map : pk -> new index
+        // ensure less than 2^20 peers
+        if self.pk_map.len() > MAX_PEER_PER_DEVICE {
+            return Err(ConfigError::new("Too many peers for device"));
+        }
 
+        // map the public key to the peer state
         self.pk_map.insert(
             *pk.as_bytes(),
             Peer::new(identifier, pk, self.sk.diffie_hellman(&pk)),
@@ -353,6 +357,8 @@ mod tests {
     use super::*;
     use hex;
     use rand::rngs::OsRng;
+    use std::thread;
+    use std::time::Duration;
 
     #[test]
     fn handshake() {
@@ -419,6 +425,9 @@ mod tests {
 
             dev1.release(ks_i.send.id);
             dev2.release(ks_r.send.id);
+
+            // to avoid flood detection
+            thread::sleep(Duration::from_millis(20));
         }
 
         assert_eq!(dev1.get_psk(pk2).unwrap(), psk);

src/handshake/noise.rs

@@ -306,7 +306,7 @@ pub fn consume_initiation<'a, T: Copy>(
 
     // check and update timestamp
 
-    peer.check_timestamp(device, &ts)?;
+    peer.check_replay_flood(device, &ts)?;
 
     // H := Hash(H || msg.timestamp)
 

src/handshake/peer.rs

@@ -1,4 +1,6 @@
+use lazy_static::lazy_static;
 use spin::Mutex;
+use std::time::{Duration, Instant};
 
 use generic_array::typenum::U32;
 use generic_array::GenericArray;
@@ -8,15 +10,18 @@ use x25519_dalek::SharedSecret;
 use x25519_dalek::StaticSecret;
 
 use super::device::Device;
+use super::macs;
 use super::timestamp;
 use super::types::*;
-use super::macs;
+
+lazy_static! {
+    pub static ref TIME_BETWEEN_INITIATIONS: Duration = Duration::from_millis(20);
+}
 
 /* Represents the recomputation and state of a peer.
  *
  * This type is only for internal use and not exposed.
  */
-
 pub struct Peer<T> {
     // external identifier
     pub(crate) identifier: T,
@@ -24,6 +29,7 @@ pub struct Peer<T> {
     // mutable state
     state: Mutex<State>,
     timestamp: Mutex<Option<timestamp::TAI64N>>,
+    last_initiation_consumption: Mutex<Option<Instant>>,
 
     // state related to DoS mitigation fields
     pub(crate) macs: Mutex<macs::Generator>,
@@ -77,6 +83,7 @@ where
             identifier: identifier,
             state: Mutex::new(State::Reset),
             timestamp: Mutex::new(None),
+            last_initiation_consumption: Mutex::new(None),
             pk: pk,
             ss: ss,
             psk: [0u8; 32],
@@ -104,38 +111,45 @@ where
     ///
     /// * st_new - The updated state of the peer
     /// * ts_new - The associated timestamp
-    pub fn check_timestamp(
+    pub fn check_replay_flood(
         &self,
         device: &Device<T>,
         timestamp_new: &timestamp::TAI64N,
     ) -> Result<(), HandshakeError> {
         let mut state = self.state.lock();
         let mut timestamp = self.timestamp.lock();
+        let mut last_initiation_consumption = self.last_initiation_consumption.lock();
 
-        let update = match *timestamp {
-            None => true,
+        // check replay attack
+        match *timestamp {
             Some(timestamp_old) => {
-                if timestamp::compare(&timestamp_old, &timestamp_new) {
-                    true
-                } else {
-                    false
+                if !timestamp::compare(&timestamp_old, &timestamp_new) {
+                    return Err(HandshakeError::OldTimestamp);
                 }
             }
+            _ => (),
         };
 
-        if update {
-            // release existing identifier
+        // check flood attack
+        match *last_initiation_consumption {
+            Some(last) => {
+                if last.elapsed() < *TIME_BETWEEN_INITIATIONS {
+                    return Err(HandshakeError::InitiationFlood);
+                }
+            }
+            _ => (),
+        }
+
+        // reset state
         match *state {
             State::InitiationSent { sender, .. } => device.release(sender),
             _ => (),
         }
 
-            // reset state and update timestamp
+        // update replay & flood protection
         *state = State::Reset;
         *timestamp = Some(*timestamp_new);
+        *last_initiation_consumption = Some(Instant::now());
         Ok(())
-        } else {
-            Err(HandshakeError::OldTimestamp)
-        }
     }
 }

src/handshake/types.rs

@@ -43,7 +43,8 @@ pub enum HandshakeError {
     OldTimestamp,
     InvalidState,
     InvalidMac1,
-    RateLimited
+    RateLimited,
+    InitiationFlood,
 }
 
 impl fmt::Display for HandshakeError {
@@ -58,7 +59,10 @@ impl fmt::Display for HandshakeError {
             HandshakeError::OldTimestamp => write!(f, "Timestamp is less/equal to the newest"),
             HandshakeError::InvalidState => write!(f, "Message does not apply to handshake state"),
             HandshakeError::InvalidMac1 => write!(f, "Message has invalid mac1 field"),
-            HandshakeError::RateLimited => write!(f, "Message was dropped by rate limiter")
+            HandshakeError::RateLimited => write!(f, "Message was dropped by rate limiter"),
+            HandshakeError::InitiationFlood => {
+                write!(f, "Message was dropped because of initiation flood")
+            }
         }
     }
 }