relaymsg/showfile: reject whitespace/control chars in a RELAYMSG spoofed nick (defence-in-depth on top of the denylist), and cap the showfile read at 256 KiB so a large /RULES-style file can't stall the core loop

src/modules/relaymsg.rs

@@ -71,7 +71,7 @@ impl Command for RelayMsg {
         if s.find_nick(nick).is_some() || s.remote_nick.contains_key(&nick.to_ascii_lowercase()) {
             return bad(s, "RELAYMSG spoofed nick is already in use");
         }
-        if nick.chars().any(|c| FORBIDDEN.contains(c)) {
+        if nick.chars().any(|c| FORBIDDEN.contains(c) || c.is_whitespace() || c.is_control()) {
             return bad(s, "Invalid characters in spoofed nick");
         }
         let seps = s

src/modules/showfile.rs

@@ -24,13 +24,19 @@ pub fn maybe_show(s: &mut Server, uid: Uid, cmd: &str) -> bool {
         return false;
     };
     let nick = s.users.get(&uid).map(|u| u.nick.clone()).unwrap_or_default();
-    match std::fs::read_to_string(&path) {
+    // cap the blocking read so a huge (mis)configured file can't stall the core loop
-        Ok(body) => {
+    let body = std::fs::File::open(&path).ok().and_then(|f| {
+        use std::io::Read;
+        let mut buf = String::new();
+        f.take(256 * 1024).read_to_string(&mut buf).ok().map(|_| buf)
+    });
+    match body {
+        Some(body) => {
             for line in body.lines() {
                 s.send(uid, format!(":{} NOTICE {nick} :{line}", s.name));
             }
         }
-        Err(_) => s.send(
+        None => s.send(
             uid,
             format!(":{} NOTICE {nick} :*** {cmd}: file not available.", s.name),
         ),