Limit CRYPTO buffering

quinn-proto/src/connection.rs

@@ -946,9 +946,8 @@ impl Connection {
         } else {
             SpaceId::Handshake
         };
-        if space < expected
-            && crypto.offset + crypto.data.len() as u64 > self.space(space).crypto_stream.offset()
-        {
+        let end = crypto.offset + crypto.data.len() as u64;
+        if space < expected && end > self.space(space).crypto_stream.offset() {
             warn!(
                 self.log,
                 "received new {actual:?} CRYPTO data when expecting {expected:?}",
@@ -961,6 +960,10 @@ impl Connection {
         }
 
         let space = &mut self.spaces[space as usize];
+        let max = space.crypto_stream.offset() + self.config.crypto_buffer_size as u64;
+        if end > max {
+            return Err(TransportError::CRYPTO_BUFFER_EXCEEDED(""));
+        }
         space
             .crypto_stream
             .insert(crypto.offset, crypto.data.clone());

quinn-proto/src/shared.rs

@@ -105,6 +105,8 @@ pub struct TransportConfig {
     /// enabled for the connection to be preserved. Must be set lower than the idle_timeout of both
     /// peers to be effective.
     pub keep_alive_interval: u32,
+    /// Maximum quantity of out-of-order crypto layer data to buffer
+    pub crypto_buffer_size: usize,
 }
 
 impl Default for TransportConfig {
@@ -139,6 +141,7 @@ impl Default for TransportConfig {
             loss_reduction_factor: 0x8000, // 1/2
             persistent_congestion_threshold: 3,
             keep_alive_interval: 0,
+            crypto_buffer_size: 16 * 1024,
         }
     }
 }
@@ -157,6 +160,11 @@ impl TransportConfig {
         {
             return Err(ConfigError::VarIntBounds(name));
         }
+        if self.crypto_buffer_size < 4096 {
+            return Err(ConfigError::IllegalValue(
+                "crypto_buffer_size must be at least 4096",
+            ));
+        }
         if self.idle_timeout != 0 && u64::from(self.keep_alive_interval) >= self.idle_timeout {
             warn!(
                 log,

quinn-proto/src/transport_error.rs

@@ -163,4 +163,5 @@ errors! {
     VERSION_NEGOTIATION_ERROR(0x9) "received transport parameters that contained version negotiation parameters that disagreed with the version negotiation that was performed, constituting a potential version downgrade attack";
     PROTOCOL_VIOLATION(0xA) "detected an error with protocol compliance that was not covered by more specific error codes";
     INVALID_MIGRATION(0xC) "migrated to a different address when the endpoint had disabled migration";
+    CRYPTO_BUFFER_EXCEEDED(0xD) "received more data in CRYPTO frames than can be buffered";
 }