feat: reject events that are too large

A new configuration setting controls the maximum size of event
messages, and sends a notice to the client if they exceed it.

Fixes https://todo.sr.ht/~gheartsfield/nostr-rs-relay/14

config.toml

@@ -3,7 +3,7 @@
 # Directory for SQLite files.  Defaults to the current directory.  Can
 # also be specified (and overriden) with the "--db dirname" command
 # line option.
-data_directory = "data"
+data_directory = "."
 
 [network]
 # Bind to this network address
@@ -15,17 +15,21 @@ port = 8080
 # Reject events that have timestamps greater than this many seconds in
 # the future.  Defaults to rejecting anything greater than 30 minutes
 # from the current time.
-#reject_future_seconds = 1800
+reject_future_seconds = 1800
 
 [limits]
 # Limit events created per second, averaged over one minute.  Must be
 # an integer.  If not set (or set to 0), defaults to unlimited.
 messages_per_sec = 0
 
-# Maximum WebSocket message in bytes.  Defaults to 128k.
+# Limit the maximum size of an EVENT message.  Defaults to 128 KB.
+# Set to 0 for unlimited.
+max_event_bytes = 131072
+
+# Maximum WebSocket message in bytes.  Defaults to 128 KB.
 max_ws_message_bytes = 131072
 
-# Maximum WebSocket frame size in bytes.  Defaults to 128k.
+# Maximum WebSocket frame size in bytes.  Defaults to 128 KB.
 max_ws_frame_bytes = 131072
 
 # Broadcast buffer size, in number of events.  This prevents slow

src/config.rs

@@ -42,7 +42,7 @@ pub struct Retention {
 #[allow(unused)]
 pub struct Limits {
     pub messages_per_sec: Option<u32>, // Artificially slow down event writing to limit disk consumption (averaged over 1 minute)
-    pub max_event_bytes: Option<usize>,
+    pub max_event_bytes: Option<usize>, // Maximum size of an EVENT message
     pub max_ws_message_bytes: Option<usize>,
     pub max_ws_frame_bytes: Option<usize>,
     pub broadcast_buffer: usize, // events to buffer for subscribers (prevents slow readers from consuming memory)

src/db.rs

@@ -145,7 +145,7 @@ pub async fn db_writer(
             }
         }
         loop {
-            if let Ok(_) = shutdown.try_recv() {
+            if shutdown.try_recv().is_ok() {
                 info!("shutting down database writer");
                 break;
             }

src/error.rs

@@ -21,6 +21,8 @@ pub enum Error {
     CloseParseFailed,
     #[error("Event validation failed")]
     EventInvalid,
+    #[error("Event too large")]
+    EventMaxLengthError(usize),
     #[error("Subscription identifier max length exceeded")]
     SubIdMaxLengthError,
     #[error("Maximum concurrent subscription count reached")]

src/main.rs

@@ -23,11 +23,9 @@ use tokio::sync::oneshot;
 use tungstenite::protocol::WebSocketConfig;
 
 fn db_from_args(args: Vec<String>) -> Option<String> {
-    if args.len() == 3 {
-        if args.get(1) == Some(&"--db".to_owned()) {
+    if args.len() == 3 && args.get(1) == Some(&"--db".to_owned()) {
         return args.get(2).map(|x| x.to_owned());
     }
-    }
     None
 }
 
@@ -44,7 +42,7 @@ fn main() -> Result<(), Error> {
         let mut c = config::Settings::new();
         // update with database location
         if let Some(db) = db_dir {
-            c.database.data_directory = db.to_owned();
+            c.database.data_directory = db;
         }
         *settings = c;
     }
@@ -253,6 +251,10 @@ async fn nostr_server(
                         debug!("got connection close/error, disconnecting client: {}",cid);
                         break;
                     }
+                    Some(Err(Error::EventMaxLengthError(s))) => {
+                        info!("client {} sent event larger ({} bytes) than max size", cid, s);
+                        nostr_stream.send(NoticeRes("event exceeded max size".to_owned())).await.ok();
+                    },
                     Some(Err(e)) => {
                         info!("got non-fatal error from client: {}, error: {:?}", cid, e);
                     },

src/protostream.rs

@@ -1,5 +1,6 @@
 //! Nostr protocol layered over WebSocket
 use crate::close::CloseCmd;
+use crate::config;
 use crate::error::{Error, Result};
 use crate::event::EventCmd;
 use crate::subscription::Subscription;
@@ -51,14 +52,23 @@ pub fn wrap_ws_in_nostr(ws: WebSocketStream<TcpStream>) -> NostrStream {
 impl Stream for NostrStream {
     type Item = Result<NostrMessage>;
     fn poll_next(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
+        // get the configuration
         /// Convert Message to NostrMessage
         fn convert(msg: String) -> Result<NostrMessage> {
-            debug!("raw msg: {}", msg);
-            let event_size = msg.len();
-            debug!("event size is {} bytes", event_size);
+            let config = config::SETTINGS.read().unwrap();
             let parsed_res: Result<NostrMessage> = serde_json::from_str(&msg).map_err(|e| e.into());
             match parsed_res {
-                Ok(m) => Ok(m),
+                Ok(m) => {
+                    if let NostrMessage::EventMsg(_) = m {
+                        if let Some(max_size) = config.limits.max_event_bytes {
+                            // check length, ensure that some max size is set.
+                            if msg.len() > max_size && max_size > 0 {
+                                return Err(Error::EventMaxLengthError(msg.len()));
+                            }
+                        }
+                    }
+                    Ok(m)
+                }
                 Err(e) => {
                     debug!("proto parse error: {:?}", e);
                     Err(Error::ProtoParseError)