feat: initial import

.gitmodules

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+[submodule "sqlite3-inet"]
+	path = sqlite3-inet
+	url = https://github.com/AlexeyPechnikov/sqlite3-inet.git

as_ban_policy_server.service

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+[Unit]
+Description=Postfix policy server that bans clients by their upstream Autonomous System
+Wants=postfix.service
+After=postfix.service
+
+[Service]
+Type=simple
+WorkingDirectory=/opt/as_ban_policy_server
+ExecStart=/usr/bin/node /opt/as_ban_policy_server/index.mjs
+User=postfix
+Restart=on-failure
+
+[Install]
+WantedBy=multi-user.target

db.mjs

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+import { DatabaseSync } from "node:sqlite";
+import { resolve } from "node:path";
+
+const MAX_TTL = 1 * 60 * 60 * 1000;
+
+const dbPath = resolve(import.meta.dirname, "data", "service.db");
+const extPath = resolve(import.meta.dirname, "data", "libsqliteipv4.so");
+console.log(`Database at ${dbPath}`);
+const db = new DatabaseSync(dbPath, { readonly: false, allowExtension: true });
+
+db.loadExtension(extPath);
+
+const schema = `
+CREATE TABLE IF NOT EXISTS "banned_as" (
+  "as" TEXT NOT NULL PRIMARY KEY,
+  "is_active" BOOLEAN NOT NULL,
+  "comment" TEXT
+  "reason" TEXT
+);
+
+CREATE TABLE IF NOT EXISTS "as_stats" (
+  "as" TEXT NOT NULL PRIMARY KEY,
+  "accepted" INT,
+  "rejected" INT
+);
+
+CREATE TABLE IF NOT EXISTS "cidr_cache" (
+  "range" TEXT NOT NULL PRIMARY KEY,
+  "as" TEXT NOT NULL,
+  "description" TEXT,
+  "date_created" TEXT NOT NULL
+);
+`;
+
+db.exec(schema);
+
+const getASFromCacheQuery = db.prepare(`SELECT range, "as", date_created FROM cidr_cache WHERE ISINNET(?, range) LIMIT 1`);
+const deleteRangeFromCacheQuery = db.prepare(`DELETE FROM cidr_cache WHERE range = ?`);
+
+export function getASFromCache(ip) {
+  const data =  getASFromCacheQuery.get(ip);
+
+  if(!data) { return null };
+
+  const { range, as, date_created } = data;
+
+  if(new Date(date_created).getTime() - new Date().getTime() > MAX_TTL) {
+    console.log(`AS Cache for ${range} is stale. Removing`);
+    deleteRangeFromCacheQuery.run(range);
+    return null;
+  }
+
+  return as;
+}
+
+const isASBannedQuery = db.prepare(`SELECT reason FROM banned_as WHERE "as" = ? AND is_active = true;`);
+export function isASBanned(as) {
+  return isASBannedQuery.get(as);
+};
+
+const updateASQuery = db.prepare(`INSERT INTO cidr_cache VALUES (?, ?, ?, datetime('now', 'localtime'));`);
+export function updateAS(as, range, description) {
+  updateASQuery.run(range, as, description);
+}
+
+const incrementAcceptedQuery = db.prepare(`INSERT INTO as_stats ("as", accepted) VALUES (?, 1) ON CONFLICT("as") DO UPDATE SET accepted = accepted + 1;`)
+const incrementRejectedQuery = db.prepare(`INSERT INTO as_stats ("as", rejected) VALUES (?, 1) ON CONFLICT("as") DO UPDATE SET rejected = rejected + 1;`)
+
+export function incrementAccepted(as) {
+  incrementAcceptedQuery.run(as);
+}
+
+export function incrementRejected(as) {
+  incrementRejectedQuery.run(as);
+}

index.mjs

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+import net from "node:net";
+import IpToAsn from "ip-to-asn";
+
+import {
+  getASFromCache,
+  updateAS,
+  isASBanned,
+  incrementRejected,
+  incrementAccepted,
+} from "./db.mjs";
+
+const asClient = new IpToAsn();
+
+// Create a server
+const server = net.createServer((socket) => {
+  // console.log(`Policy server connection established`);
+
+  socket.on("data", async (data) => {
+    const lines = data.toString().trim();
+
+    let response = "dunno"; // Default response
+
+    try {
+      const command = lines.split(/[\r\n]/).reduce((acc, i) => {
+        const [key, value] = i.split("=");
+        return { ...acc, [key]: value };
+      }, {});
+
+      const { client_address, client_name, sender, recipient } = command;
+
+      console.log(
+        `Incoming email from "${client_name}[${client_address}]. ${sender} -> ${recipient}`,
+      );
+
+      // check if IP belongs to previously cached AS records
+      let as = getASFromCache(client_address);
+
+      if (!as) {
+        // console.log(`Fetching AS for ${client_address}`);
+        const result = await query(client_address);
+        if (result) {
+          const { range, ASN, description } = result;
+          as = ASN;
+          updateAS(as, range, description);
+        }
+      }
+
+      const reason = isASBanned(as);
+      if (reason) {
+        // console.log(`AS ${as} is banned`);
+        response = `reject ${reason.reason}`;
+        incrementRejected(as);
+      } else {
+        incrementAccepted(as);
+      }
+      // Check if AS is in the ban list
+    } catch (err) {
+      console.error("Error processing command:", err);
+    }
+
+    console.log(`Verdict: ${response}`);
+    socket.write(`${response}\r\n`);
+  });
+
+  socket.on("end", () => {
+    console.log("Policy server connection ended");
+  });
+
+  socket.on("error", (err) => {
+    console.error("Policy server socket error:", err);
+  });
+});
+
+// Start the server
+server.listen(12346, "127.0.0.1", () => {
+  console.log(`Policy server running`);
+});
+
+function query(...ip) {
+  return new Promise((resolve, reject) => {
+    asClient.query(ip, (err, result) => {
+      if (err) {
+        return reject(err);
+      }
+
+      resolve(result[ip[0]]);
+    });
+  });
+}

package-lock.json

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+{
+  "name": "as_ban_policy_server",
+  "version": "1.0.0",
+  "lockfileVersion": 3,
+  "requires": true,
+  "packages": {
+    "": {
+      "name": "as_ban_policy_server",
+      "version": "1.0.0",
+      "license": "ISC",
+      "dependencies": {
+        "ip-to-asn": "github:vsviridov/ip-to-asn#0779e4c247bcf736f7adc56b730bea3dbe69500a"
+      }
+    },
+    "node_modules/ip-to-asn": {
+      "version": "1.0.1",
+      "resolved": "git+ssh://git@github.com/vsviridov/ip-to-asn.git#0779e4c247bcf736f7adc56b730bea3dbe69500a",
+      "integrity": "sha512-K986ggPV8Akw58l13tDmYoa9uB01t0ojq60qBY8q6wugsyyw3Sa9UVNN0YX7eq5z6H8CR74FvomDE4zXIQXgWQ==",
+      "license": "MIT"
+    }
+  }
+}

package.json

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+{
+  "name": "as_ban_policy_server",
+  "version": "1.0.0",
+  "description": "",
+  "main": "index.js",
+  "scripts": {
+    "test": "echo \"Error: no test specified\" && exit 1"
+  },
+  "keywords": [],
+  "author": "",
+  "license": "ISC",
+  "type": "commonjs",
+  "dependencies": {
+    "ip-to-asn": "github:vsviridov/ip-to-asn#0779e4c247bcf736f7adc56b730bea3dbe69500a"
+  }
+}