feat: initial import

index.mjs

@@ -0,0 +1,89 @@
+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]]);
+    });
+  });
+}