Check if ACLs match before applying them

Fixes https://github.com/matrix-org/mjolnir/issues/9

src/actions/ApplyAcl.ts

@@ -46,6 +46,22 @@ export async function applyServerAcls(lists: BanList[], roomIds: string[], mjoln
     const errors: RoomUpdateError[] = [];
     for (const roomId of roomIds) {
         try {
+            if (config.verboseLogging) {
+                await mjolnir.client.sendNotice(mjolnir.managementRoomId, `Checking ACLs for ${roomId}`);
+            }
+
+            try {
+                const currentAcl = await mjolnir.client.getRoomStateEvent(roomId, "m.room.server_acl", "");
+                if (acl.matches(currentAcl)) {
+                    if (config.verboseLogging) {
+                        await mjolnir.client.sendNotice(mjolnir.managementRoomId, `Skipping ACLs for ${roomId} because they are already the right ones`);
+                    }
+                    continue;
+                }
+            } catch (e) {
+                // ignore - assume no ACL
+            }
+
             if (config.verboseLogging) {
                 // We specifically use sendNotice to avoid having to escape HTML
                 await mjolnir.client.sendNotice(mjolnir.managementRoomId, `Applying ACL in ${roomId}`);

src/models/ServerAcl.ts

@@ -76,4 +76,38 @@ export class ServerAcl {
             allow_ip_literals: this.allowIps,
         };
     }
+
+    public matches(acl: any): boolean {
+        if (!acl) return false;
+
+        const allow = acl['allow'];
+        const deny = acl['deny'];
+        const ips = acl['allow_ip_literals'];
+
+        let allowMatches = true; // until proven false
+        let denyMatches = true; // until proven false
+        let ipsMatch = ips === this.allowIps;
+
+        const currentAllowed = setToArray(this.allowedServers);
+        if (allow.length === currentAllowed.length) {
+            for (const s of allow) {
+                if (!currentAllowed.includes(s)) {
+                    allowMatches = false;
+                    break;
+                }
+            }
+        } else allowMatches = false;
+
+        const currentDenied = setToArray(this.deniedServers);
+        if (deny.length === currentDenied.length) {
+            for (const s of deny) {
+                if (!currentDenied.includes(s)) {
+                    denyMatches = false;
+                    break;
+                }
+            }
+        } else denyMatches = false;
+
+        return denyMatches && allowMatches && ipsMatch;
+    }
 }