fix: bound IRC state, read recording metadata from the file tail, cap the audit log

- IRC: channel state is kept only for rooms the client itself joined, so
  JOIN/PART/KICK/NAMES for other rooms can't grow it; users per channel
  are capped at 10 000 and the view keeps at most 200 conversations,
  dropping the oldest idle query (SEC-20261012-014, F14).
- Recordings: the list reads the header line and the last 64 KiB for the
  duration instead of whole files of up to 250 MiB, falling back to a
  full scan only when the final event is longer than the window
  (SEC-20261012-020, F9).
- Audit log: keeps the newest 10 000 entries (F17).

rust/core/src/clients/irc.rs

@@ -25,6 +25,8 @@ const PING_DELAY: Duration = Duration::from_secs(20);
 const PING_TIMEOUT: Duration = Duration::from_secs(60);
 const PING_GRACE: Duration = Duration::from_secs(30);
 const MAX_LINE_BYTES: usize = 1 << 20;
+/// Users tracked per channel; a hostile server can't grow the client past this.
+const MAX_CHANNEL_USERS: usize = 10_000;
 
 /// A bidirectional byte stream. Reads must not block indefinitely: they should return
 /// `WouldBlock` or `TimedOut` after a short interval (tens of milliseconds) so the client's
@@ -602,6 +604,12 @@ impl Client {
         fold(nick) == fold(&self.st().nick)
     }
 
+    /// Whether we're in `room`: state is only kept for channels the client itself joined, so a
+    /// server can't grow it with JOINs for rooms we never asked for.
+    fn tracks(&self, room: &str) -> bool {
+        self.st().channels.contains_key(&fold(room))
+    }
+
     fn handle_message(&self, m: &Message) {
         match m.command.as_str() {
             "001" => self.handle_welcome(m),
@@ -734,12 +742,16 @@ impl Client {
             return;
         }
         let from = m.source.clone();
+        let me = self.is_me(&from);
+        if !me && !self.tracks(&room) {
+            return;
+        }
         if !from.is_empty() {
             let mut st = self.st();
             let ch = st.channels.entry(fold(&room)).or_insert_with(|| Channel { name: room.clone(), topic: String::new(), users: Vec::new() });
             add_user(ch, &from);
         }
-        if self.is_me(&from) {
+        if me {
             self.remember_room_membership(&room, true);
         }
         self.emit(Event { kind: "join".into(), target: room.clone(), from: from.clone(), text: format!("{from} joined {room}"), ..Default::default() });
@@ -754,6 +766,9 @@ impl Client {
         }
         let from = m.source.clone();
         let me = self.is_me(&from);
+        if !self.tracks(&room) {
+            return;
+        }
         if !from.is_empty() {
             let mut st = self.st();
             if me {
@@ -777,6 +792,9 @@ impl Client {
         }
         let (room, kicked) = (m.param(0).to_string(), m.param(1).to_string());
         let me = self.is_me(&kicked);
+        if !self.tracks(&room) {
+            return;
+        }
         {
             let mut st = self.st();
             if me {
@@ -846,7 +864,7 @@ impl Client {
     }
 
     fn handle_names(&self, m: &Message) {
-        if m.params.len() < 4 {
+        if m.params.len() < 4 || !self.tracks(m.param(2)) {
             return;
         }
         {
@@ -943,7 +961,7 @@ fn fold(s: &str) -> String {
 }
 
 fn add_user(ch: &mut Channel, nick: &str) {
-    if !ch.users.iter().any(|u| fold(u) == fold(nick)) {
+    if ch.users.len() < MAX_CHANNEL_USERS && !ch.users.iter().any(|u| fold(u) == fold(nick)) {
         ch.users.push(nick.to_string());
     }
 }
@@ -1048,6 +1066,23 @@ mod tests {
         assert_eq!(client.st().room_names, vec!["#two"]);
     }
 
+    #[test]
+    fn only_joined_channels_are_tracked_and_users_are_capped() {
+        let client = Client::new(Config::default());
+        client.st().nick = "me".into();
+        let feed = |l: &str| client.handle_message(&parse_line(l).unwrap());
+        for n in 0..20_000 {
+            feed(&format!(":x{n}!u@h JOIN #room-{n}"));
+        }
+        assert!(client.st().channels.is_empty(), "JOINs by others for rooms we're not in are ignored");
+        feed(":me!u@h JOIN #ours");
+        feed(":other!u@h JOIN #ours");
+        assert_eq!(client.st().channels[&fold("#ours")].users, vec!["me", "other"]);
+        let mut ch = Channel { name: "#big".into(), topic: String::new(), users: (0..MAX_CHANNEL_USERS).map(|n| format!("u{n}")).collect() };
+        add_user(&mut ch, "one-too-many");
+        assert_eq!(ch.users.len(), MAX_CHANNEL_USERS);
+    }
+
     #[test]
     fn parses_and_encodes_lines() {
         let m = parse_line("@time=x :nick!u@h PRIVMSG #chan :hello there").unwrap();

rust/core/src/recording.rs

@@ -7,7 +7,7 @@ use parking_lot::Mutex;
 use serde::{Deserialize, Serialize};
 use std::collections::BTreeMap;
 use std::fs::File;
-use std::io::{Read, Write};
+use std::io::{BufRead, BufReader, Read, Seek, SeekFrom, Write};
 use std::path::{Path, PathBuf};
 use std::time::Instant;
 
@@ -328,22 +328,32 @@ impl Store {
         Ok(self.dir.join(format!("{id}.cast")))
     }
 
-    /// Header fields plus the last event's timestamp as the duration.
+    /// Header fields plus the last event's timestamp as the duration. Reads the header line and
+    /// the file's tail rather than the whole recording (they can be hundreds of MiB).
     fn read_meta(&self, filename: &str) -> Result<RecordingMeta> {
+        const TAIL: u64 = 64 << 10;
         let path = self.dir.join(filename);
-        let mut f = File::open(&path)?;
-        let size = f.metadata()?.len();
-        let mut raw = Vec::new();
-        f.read_to_end(&mut raw)?;
-        let mut values = serde_json::Deserializer::from_slice(&raw).into_iter::<serde_json::Value>();
-        let hdr: Header = serde_json::from_value(values.next().ok_or("recording: empty file")??)?;
-        let mut duration = 0.0;
-        for v in values {
-            let Ok(v) = v else { break };
-            if let Some(e) = v.get(0).and_then(|e| e.as_f64()) {
-                duration = e;
+        let mut f = BufReader::new(File::open(&path)?);
+        let size = f.get_ref().metadata()?.len();
+        let mut head = Vec::new();
+        f.by_ref().take(1 << 20).read_until(b'\n', &mut head)?;
+        if head.iter().all(u8::is_ascii_whitespace) {
+            return Err("recording: empty file".into());
+        }
+        let hdr: Header = serde_json::from_slice(&head)?;
+        let body = head.len() as u64;
+        let mut duration = None;
+        // The tail first; if one event is longer than the window, fall back to the whole body.
+        for start in [size.saturating_sub(TAIL).max(body), body] {
+            let mut tail = Vec::new();
+            f.seek(SeekFrom::Start(start))?;
+            f.read_to_end(&mut tail)?;
+            duration = tail.split(|b| *b == b'\n').rev().find_map(|l| serde_json::from_slice::<serde_json::Value>(l).ok()?.get(0)?.as_f64());
+            if duration.is_some() || start == body {
+                break;
             }
         }
+        let duration = duration.unwrap_or(0.0);
         let id = filename.trim_end_matches(".cast").to_string();
         let created_at = chrono::DateTime::from_timestamp(hdr.timestamp, 0).ok_or("recording: invalid timestamp")?.with_timezone(&chrono::Local).fixed_offset();
         Ok(RecordingMeta {
@@ -431,6 +441,25 @@ mod tests {
         std::fs::remove_dir_all(dir).unwrap();
     }
 
+    #[test]
+    fn duration_comes_from_the_tail_even_with_long_events() {
+        let dir = tmp("tail");
+        std::fs::create_dir_all(&dir).unwrap();
+        let hdr = r#"{"version":2,"width":80,"height":24,"timestamp":1791633486}"#;
+        let mut many = format!("{hdr}\n");
+        for i in 0..20_000 {
+            many.push_str(&format!("[{}.5, \"o\", \"line {i}\\r\\n\"]\n", i));
+        }
+        std::fs::write(dir.join("many.cast"), many).unwrap();
+        // The last event alone is bigger than the tail window.
+        std::fs::write(dir.join("long.cast"), format!("{hdr}\n[1.0, \"o\", \"a\"]\n[7.25, \"o\", \"{}\"]\n", "x".repeat(200 << 10))).unwrap();
+        std::fs::write(dir.join("bare.cast"), format!("{hdr}\n")).unwrap();
+        let metas = Store::new(&dir).list().unwrap();
+        let d = |id: &str| metas.iter().find(|m| m.id == id).unwrap().duration;
+        assert_eq!((d("many"), d("long"), d("bare")), (19_999.5, 7.25, 0.0));
+        std::fs::remove_dir_all(dir).unwrap();
+    }
+
     #[test]
     fn stops_at_size_limit() {
         let dir = tmp("limit");

rust/core/src/storage.rs

@@ -34,6 +34,9 @@ pub fn parse_time(s: &str) -> Time {
     DateTime::parse_from_rfc3339(s).unwrap_or_else(|_| zero_time())
 }
 
+/// Audit-log entries kept; older ones are pruned as new ones arrive.
+pub const MAX_AUDIT_ROWS: i64 = 10_000;
+
 pub struct Store {
     db: Mutex<Connection>,
 }
@@ -318,11 +321,14 @@ impl Store {
         Ok(())
     }
 
+    /// Records an action; the log keeps the newest [`MAX_AUDIT_ROWS`] entries.
     pub fn add_audit(&self, action: &str, profile_id: &str, session_id: &str, details: &str) {
-        let _ = self.db.lock().execute(
+        let db = self.db.lock();
+        let _ = db.execute(
             "INSERT INTO audit_log (id, timestamp, action, profile_id, session_id, details) VALUES (?, ?, ?, ?, ?, ?)",
             params![new_id(), fmt_time(&now()), action, profile_id, session_id, details],
         );
+        let _ = db.execute("DELETE FROM audit_log WHERE rowid <= (SELECT MAX(rowid) FROM audit_log) - ?", [MAX_AUDIT_ROWS]);
     }
 
     pub fn list_audit(&self, limit: i64) -> Result<Vec<AuditEntry>> {
@@ -433,6 +439,29 @@ pub fn dedup_rooms(groups: &[&[String]]) -> Vec<String> {
 mod tests {
     use super::*;
 
+    #[test]
+    fn audit_log_keeps_the_newest_entries() {
+        let tmp = std::env::temp_dir().join(format!("nexus-audit-{}.db", std::process::id()));
+        let s = Store::open(&tmp).unwrap();
+        {
+            let mut db = s.db.lock();
+            let tx = db.transaction().unwrap();
+            for n in 0..MAX_AUDIT_ROWS {
+                tx.execute("INSERT INTO audit_log (id, timestamp, action) VALUES (?, '2020-01-01T00:00:00Z', 'old')", [n.to_string()]).unwrap();
+            }
+            tx.commit().unwrap();
+        }
+        for _ in 0..3 {
+            s.add_audit("new", "", "", "");
+        }
+        let count = |action: &str| s.db.lock().query_row("SELECT COUNT(*) FROM audit_log WHERE action = ?", [action], |r| r.get::<_, i64>(0)).unwrap();
+        assert_eq!((count("old"), count("new")), (MAX_AUDIT_ROWS - 3, 3));
+        drop(s);
+        for ext in ["", "-wal", "-shm"] {
+            let _ = std::fs::remove_file(format!("{}{ext}", tmp.display()));
+        }
+    }
+
     #[test]
     fn opens_go_database_and_migrates() {
         let fx = std::path::PathBuf::from(env!("CARGO_MANIFEST_DIR")).join("tests/fixtures/link.db");