Enforce a maximum key length.

linera-execution/src/lib.rs

@@ -73,6 +73,9 @@ pub use crate::{
     },
 };
 
+/// The maximum length of an event key in bytes.
+const MAX_EVENT_KEY_LEN: usize = 64;
+
 /// An implementation of [`UserContractModule`].
 pub type UserContractCode = Arc<dyn UserContractModule + Send + Sync + 'static>;
 
@@ -165,6 +168,8 @@ pub enum ExecutionError {
 
     #[error("Blob not found on storage read: {0}")]
     BlobNotFoundOnRead(BlobId),
+    #[error("Event keys can be at most {MAX_EVENT_KEY_LEN} bytes.")]
+    EventKeyTooLong,
 }
 
 /// The public entry points provided by the contract part of an application.

linera-execution/src/runtime.rs

@@ -32,6 +32,7 @@ use crate::{
     BaseRuntime, ContractRuntime, ExecutionError, ExecutionOutcome, FinalizeContext,
     MessageContext, OperationContext, QueryContext, RawExecutionOutcome, ServiceRuntime,
     UserApplicationDescription, UserApplicationId, UserContractInstance, UserServiceInstance,
+    MAX_EVENT_KEY_LEN,
 };
 
 #[cfg(test)]
@@ -1266,6 +1267,10 @@ impl ContractRuntime for ContractSyncRuntimeHandle {
         value: Vec<u8>,
     ) -> Result<(), ExecutionError> {
         let mut this = self.inner();
+        ensure!(
+            key.len() <= MAX_EVENT_KEY_LEN,
+            ExecutionError::EventKeyTooLong
+        );
         let application = this.current_application_mut();
         application.outcome.events.push((name, key, value));
         Ok(())

linera-service-graphql-client/src/service.rs

@@ -7,7 +7,7 @@ use linera_base::{
     data_types::{Amount, BlockHeight, OracleResponse, Timestamp},
     identifiers::{
         Account, ChainDescription, ChainId, ChannelName, Destination, GenericApplicationId, Owner,
-        StreamId, StreamName,
+        StreamName,
     },
 };
 
@@ -132,6 +132,7 @@ pub struct Transfer;
 
 #[cfg(not(target_arch = "wasm32"))]
 mod from {
+    use linera_base::identifiers::StreamId;
     use linera_chain::data_types::{
         BlockExecutionOutcome, EventRecord, ExecutedBlock, HashedCertificateValue, IncomingMessage,
         OutgoingMessage,