hidemode: hide configured mode changes from members below a rank (per-recipient MODE)

src/coremods/core_mode.rs

@@ -113,6 +113,8 @@ pub fn apply_mode(s: &mut Server, uid: Uid, params: &[String]) -> CmdResult {
     let mut applied = String::new();
     let mut last = ' ';
     let mut echoed: Vec<String> = Vec::new();
+    // (sign, letter, displayed-param) per applied change — for hidemode filtering
+    let mut changes: Vec<(char, char, Option<String>)> = Vec::new();
     for c in modestring.chars() {
         if c == '+' || c == '-' {
             sign = c;
@@ -138,6 +140,7 @@ pub fn apply_mode(s: &mut Server, uid: Uid, params: &[String]) -> CmdResult {
         };
         if let Applied::Yes(echo) = handler.apply(s, target, &key, uid, adding, param.as_deref()) {
             emit(&mut applied, &mut last, sign, c);
+            changes.push((sign, c, echo.clone()));
             if let Some(p) = echo {
                 echoed.push(p);
             }
@@ -150,11 +153,21 @@ pub fn apply_mode(s: &mut Server, uid: Uid, params: &[String]) -> CmdResult {
         } else {
             format!(" {}", echoed.join(" "))
         };
-        s.to_channel(
-            &key,
-            &format!(":{prefix} MODE {target} {applied}{pstr}"),
-            None,
-        );
+        // hidemode: if any changed mode is configured hidden, deliver per-recipient
+        // so members below the required rank don't see it; the setter, opers and
+        // linked servers always get the full line.
+        if changes
+            .iter()
+            .any(|(_, c, _)| crate::modules::hidemode::hidden_rank(s, *c).is_some())
+        {
+            crate::modules::hidemode::broadcast(s, &key, target, uid, &prefix, &changes);
+        } else {
+            s.to_channel(
+                &key,
+                &format!(":{prefix} MODE {target} {applied}{pstr}"),
+                None,
+            );
+        }
         s.propagate_from_user(uid, &format!("MODE {target} {applied}{pstr}"));
         // links
     }

src/modules/hidemode.rs

@@ -0,0 +1,90 @@
+//! hidemode — hide specific mode changes from channel members below a rank, so
+//! ordinary users don't see e.g. bans being set/removed. Config, repeatable:
+//! `hidemode = <modechar> <rank>` (rank: owner|admin|op|halfop|voice). The setter,
+//! opers and linked servers always see the full change. Reference: InspIRCd's
+//! `m_hidemode`. Original native Rust.
+
+use crate::channels::{RANK_ADMIN, RANK_HALFOP, RANK_OP, RANK_OWNER, RANK_VOICE};
+use crate::server::Server;
+use crate::Uid;
+
+fn rank_value(name: &str) -> u8 {
+    match name.to_ascii_lowercase().as_str() {
+        "owner" | "founder" | "q" => RANK_OWNER,
+        "admin" | "protect" | "a" => RANK_ADMIN,
+        "op" | "o" => RANK_OP,
+        "halfop" | "h" => RANK_HALFOP,
+        "voice" | "v" => RANK_VOICE,
+        _ => RANK_OP,
+    }
+}
+
+/// The minimum rank needed to *see* changes to `modechar`, if it's configured
+/// hidden. `None` ⇒ the mode is visible to everyone (the common case).
+pub fn hidden_rank(s: &Server, modechar: char) -> Option<u8> {
+    for line in s.conf_all("hidemode") {
+        let mut it = line.split_whitespace();
+        if let (Some(mc), Some(rank)) = (it.next(), it.next()) {
+            if mc.chars().next() == Some(modechar) {
+                return Some(rank_value(rank));
+            }
+        }
+    }
+    None
+}
+
+/// Render a subset of changes back into a `<modes> <params…>` pair.
+fn render(changes: &[&(char, char, Option<String>)]) -> (String, Vec<String>) {
+    let mut modes = String::new();
+    let mut last = ' ';
+    let mut params = Vec::new();
+    for (sign, letter, param) in changes {
+        if *sign != last {
+            modes.push(*sign);
+            last = *sign;
+        }
+        modes.push(*letter);
+        if let Some(p) = param {
+            params.push(p.clone());
+        }
+    }
+    (modes, params)
+}
+
+/// Deliver a MODE change per-recipient, dropping any hidden mode from the line sent
+/// to members below its required rank. Called from `apply_mode` only when at least
+/// one changed mode is hidden.
+pub fn broadcast(
+    s: &Server,
+    key: &str,
+    target: &str,
+    setter: Uid,
+    prefix: &str,
+    changes: &[(char, char, Option<String>)],
+) {
+    let members: Vec<Uid> = s
+        .channels
+        .get(key)
+        .map(|c| c.members.keys().copied().collect())
+        .unwrap_or_default();
+    for m in members {
+        let privileged = m == setter || s.is_oper(m);
+        let visible: Vec<&(char, char, Option<String>)> = changes
+            .iter()
+            .filter(|(_, c, _)| match hidden_rank(s, *c) {
+                None => true,
+                Some(req) => privileged || s.rank(m, key) >= req,
+            })
+            .collect();
+        if visible.is_empty() {
+            continue;
+        }
+        let (modes, params) = render(&visible);
+        let pstr = if params.is_empty() {
+            String::new()
+        } else {
+            format!(" {}", params.join(" "))
+        };
+        s.send(m, format!(":{prefix} MODE {target} {modes}{pstr}"));
+    }
+}

src/modules/mod.rs

@@ -34,6 +34,7 @@ pub mod geoip;
 pub mod globops;
 pub mod hashident;
 pub mod hidelist;
+pub mod hidemode;
 pub mod hidewhois;
 pub mod irccloudtags;
 pub mod jsonlog;