feat: add ENABLE_CHECK_JUNK_MAIL (#469)

worker/src/email/check_junk.ts

@@ -0,0 +1,44 @@
+import { Bindings } from "../types";
+import { getBooleanValue } from "../utils";
+import { commonParseMail } from "../common";
+
+export const check_if_junk_mail = async (
+    env: Bindings, address: string,
+    raw_mail: string, message_id: string | null
+): Promise<boolean> => {
+    if (!getBooleanValue(env.ENABLE_CHECK_JUNK_MAIL)) {
+        return false;
+    }
+    const parsedEmail = await commonParseMail(raw_mail);
+    if (!parsedEmail?.headers) return false;
+    const headers = parsedEmail.headers;
+    for (const header of headers) {
+        if (!header["key"]) continue;
+        if (!header["value"]) continue;
+
+        // check spf
+        if (header["key"].toLowerCase() == "received-spf"
+            &&
+            !header["value"].toLowerCase().includes("pass")
+        ) {
+            return true;
+        }
+
+        // check dkim and dmarc
+        if (header["key"].toLowerCase() == "authentication-results") {
+            if (header["value"].toLowerCase().includes("dkim=")
+                &&
+                !header["value"].toLowerCase().includes("dkim=pass")
+            ) {
+                return true;
+            }
+            if (header["value"].toLowerCase().includes("dmarc=")
+                &&
+                !header["value"].toLowerCase().includes("dmarc=pass")
+            ) {
+                return true;
+            }
+        }
+    }
+    return false;
+}

worker/src/email/index.ts

@@ -6,6 +6,7 @@ import { Bindings, HonoCustomType } from "../types";
 import { auto_reply } from "./auto_reply";
 import { isBlocked } from "./black_list";
 import { triggerWebhook } from "../common";
+import { check_if_junk_mail } from "./check_junk";
 
 
 async function email(message: ForwardableEmailMessage, env: Bindings, ctx: ExecutionContext) {
@@ -15,6 +16,19 @@ async function email(message: ForwardableEmailMessage, env: Bindings, ctx: Execu
         return;
     }
     const rawEmail = await new Response(message.raw).text();
+
+    // check if junk mail
+    try {
+        const is_junk = await check_if_junk_mail(env, message.to, rawEmail, message.headers.get("Message-ID"));
+        if (is_junk) {
+            message.setReject("Junk mail");
+            console.log(`Junk mail from ${message.from} to ${message.to}`);
+            return;
+        }
+    } catch (error) {
+        console.log("check junk mail error", error);
+    }
+
     const message_id = message.headers.get("Message-ID");
     // save email
     const { success } = await env.DB.prepare(