use nonce in handshake

To prevent stale hello replies to cause joins and thus stale sessions,
each run gets a random ID, which used as nonce in the handshake.

2 files changed, 21 insertions, 0 deletions

diff --git a/src/transport/mod.rs b/src/transport/mod.rs
index 83c4e8d..e8d654d 100644
--- a/src/transport/mod.rs
+++ b/src/transport/mod.rs
@@ -12,6 +12,9 @@ pub use crate::document::replica::Epoch;
 pub mod firewall;
 pub mod mycelium;
 
+/// Random identifier of one run of a node (from start to exit).
+pub type RunId = [u8; 16];
+
 /// Most heads listed in a keepalive; more are sent as a digest. A head takes 34 bytes on
 /// the wire, so 32 of them keep a keepalive within one Mycelium chunk (1300 bytes; see
 /// the size test in `mycelium`). There are rarely more heads than nodes that wrote
@@ -120,6 +123,8 @@ pub struct HelloRequest {
     pub auth: Vec<u8>,
     /// The sender is ready (same meaning as `SyncEnvelope::ready`).
     pub ready: bool,
+    /// Random per run of the sender; the reply echoes it.
+    pub run_id: RunId,
 }
 
 #[derive(Debug, Clone)]
@@ -131,6 +136,9 @@ pub struct HelloReply {
     pub auth: Vec<u8>,
     /// The sender is ready.
     pub ready: bool,
+    /// The `run_id` of the HELLO answered. A reply to a HELLO from an earlier run of the
+    /// recipient (delivered late, or queued while it was down) is ignored.
+    pub run_id: RunId,
 }
 
 #[derive(Debug, Clone)]
diff --git a/src/transport/mycelium.rs b/src/transport/mycelium.rs
index 4c03839..51bbfab 100644
--- a/src/transport/mycelium.rs
+++ b/src/transport/mycelium.rs
@@ -877,6 +877,7 @@ pub struct HelloRequestShadow {
     epoch: EpochShadow,
     auth: ByteBuf,
     ready: bool,
+    run_id: ByteBuf,
 }
 
 #[derive(Serialize, Deserialize)]
@@ -890,6 +891,7 @@ pub struct HelloReplyShadow<'a> {
     #[serde(default)]
     auth: ByteBuf,
     ready: bool,
+    run_id: ByteBuf,
 }
 
 #[derive(Serialize, Deserialize)]
@@ -940,6 +942,7 @@ pub fn hello_request_to_bytes(msg: &HelloRequest) -> Result<Vec<u8>, rmp_serde::
         epoch: epoch_to_shadow(&msg.epoch),
         auth: ByteBuf::from(msg.auth.clone()),
         ready: msg.ready,
+        run_id: ByteBuf::from(msg.run_id.to_vec()),
     })
 }
 pub fn bytes_to_hello_request(bytes: &[u8]) -> Result<HelloRequest, TransportError> {
@@ -949,9 +952,17 @@ pub fn bytes_to_hello_request(bytes: &[u8]) -> Result<HelloRequest, TransportErr
         epoch: epoch_from_shadow(shadow.epoch)?,
         auth: shadow.auth.into_vec(),
         ready: shadow.ready,
+        run_id: run_id_from_shadow(&shadow.run_id)?,
     })
 }
 
+fn run_id_from_shadow(bytes: &ByteBuf) -> Result<crate::transport::RunId, TransportError> {
+    bytes
+        .as_slice()
+        .try_into()
+        .map_err(|_| TransportError::InvalidPayload("run id must be 16 bytes".into()))
+}
+
 // --- HelloReply ---
 pub fn hello_reply_to_bytes(msg: &HelloReply) -> Result<Vec<u8>, rmp_serde::encode::Error> {
     let shadow = HelloReplyShadow {
@@ -960,6 +971,7 @@ pub fn hello_reply_to_bytes(msg: &HelloReply) -> Result<Vec<u8>, rmp_serde::enco
         epoch: epoch_to_shadow(&msg.epoch),
         auth: ByteBuf::from(msg.auth.clone()),
         ready: msg.ready,
+        run_id: ByteBuf::from(msg.run_id.to_vec()),
     };
     rmp_serde::to_vec(&shadow)
 }
@@ -971,6 +983,7 @@ pub fn bytes_to_hello_reply(bytes: &[u8]) -> Result<HelloReply, TransportError>
         epoch: epoch_from_shadow(shadow.epoch)?,
         auth: shadow.auth.into_vec(),
         ready: shadow.ready,
+        run_id: run_id_from_shadow(&shadow.run_id)?,
     })
 }