Add DKIM tests

packages/helpers/package.json

@@ -1,6 +1,6 @@
 {
   "name": "@zk-email/helpers",
-  "version": "3.1.3",
+  "version": "3.2.0",
   "main": "dist",
   "scripts": {
     "build": "tsc",

packages/helpers/src/dkim/arc.ts

@@ -0,0 +1,46 @@
+export async function revertCommonARCModifications(
+  email: string
+): Promise<string> {
+  if (!email.includes("ARC-Authentication-Results")) {
+    return email;
+  }
+
+  let modified = revertGoogleModifications(email);
+
+  if (modified === email) {
+    console.log("ARC Revert: No known ARC modifications found");
+  }
+
+  return modified;
+}
+
+function revertGoogleModifications(email: string): string {
+  // Google sets their own Message-ID and put the original one
+  // in X-Google-Original-Message-ID when forwarding
+  const googleReplacedMessageId = getHeaderValue(
+    email,
+    "X-Google-Original-Message-ID"
+  );
+
+  if (googleReplacedMessageId) {
+    email = setHeaderValue(email, "Message-ID", googleReplacedMessageId);
+
+    console.info(
+      "ARC Revert: Setting X-Google-Original-Message-ID to Message-ID header..."
+    );
+  }
+
+  return email;
+}
+
+function getHeaderValue(email: string, header: string) {
+  const headerStartIndex = email.indexOf(`${header}: `) + header.length + 2;
+  const headerEndIndex = email.indexOf("\n", headerStartIndex);
+  const headerValue = email.substring(headerStartIndex, headerEndIndex);
+
+  return headerValue;
+}
+
+function setHeaderValue(email: string, header: string, value: string) {
+  return email.replace(getHeaderValue(email, header), value);
+}

packages/helpers/src/dkim/index.ts

@@ -1,6 +1,12 @@
 import { pki } from "node-forge";
 import { DkimVerifier } from "./dkim-verifier";
-import { getSigningHeaderLines, parseDkimHeaders, parseHeaders, writeToStream } from "./tools";
+import {
+  getSigningHeaderLines,
+  parseDkimHeaders,
+  parseHeaders,
+  writeToStream,
+} from "./tools";
+import { revertCommonARCModifications } from "./arc";
 
 export interface DKIMVerificationResult {
   publicKey: bigint;
@@ -22,20 +28,28 @@ export async function verifyDKIMSignature(
 ): Promise<DKIMVerificationResult> {
   let dkimResult = await tryVerifyDKIM(email, domain);
 
-  if (dkimResult.status.result !== "pass" && tryRevertARCChanges) {
-    console.info("DKIM verification failed. Trying to verify after reverting forwarder changes...");
-
-    const modified = await revertForwarderChanges(email.toString());
+  // If DKIM verification fails, revert common modifications made by ARC and try again.
+  if (dkimResult.status.comment === "bad signature" && tryRevertARCChanges) {
+    const modified = await revertCommonARCModifications(email.toString());
     dkimResult = await tryVerifyDKIM(modified, domain);
   }
 
-  if (dkimResult.status.result !== "pass") {
+  const {
+    status: { result, comment },
+    signingDomain,
+    publicKey,
+    signature,
+    status,
+    body,
+    bodyHash,
+  } = dkimResult;
+
+  if (result !== "pass") {
     throw new Error(
-      `DKIM signature verification failed for domain ${dkimResult.signingDomain}`
+      `DKIM signature verification failed for domain ${signingDomain}. Reason: ${comment}`
     );
   }
 
-  const { publicKey, signature, status, body, bodyHash } = dkimResult;
   const pubKeyData = pki.publicKeyFromPem(publicKey.toString());
 
   return {
@@ -72,7 +86,9 @@ async function tryVerifyDKIM(email: Buffer | string, domain: string = "") {
   );
 
   if (!dkimResult) {
-    throw new Error(`DKIM signature not found for domain ${domainToVerifyDKIM}`);
+    throw new Error(
+      `DKIM signature not found for domain ${domainToVerifyDKIM}`
+    );
   }
 
   if (dkimVerifier.headers) {
@@ -87,39 +103,15 @@ async function tryVerifyDKIM(email: Buffer | string, domain: string = "") {
   return dkimResult;
 }
 
-function getHeaderValue(email: string, header: string) {
-  const headerStartIndex = email.indexOf(`${header}: `) + header.length + 2;
-  const headerEndIndex = email.indexOf('\n', headerStartIndex);
-  const headerValue = email.substring(headerStartIndex, headerEndIndex);
-
-  return headerValue;
-}
-
-function setHeaderValue(email: string, header: string, value: string) {
-  return email.replace(getHeaderValue(email, header), value);
-}
-
-async function revertForwarderChanges(email: string) {
-  // Google sets their own Message-ID and put the original one in X-Google-Original-Message-ID when forwarding
-  const googleReplacedMessageId = getHeaderValue(email, "X-Google-Original-Message-ID");
-  if (googleReplacedMessageId) {
-    console.info("Setting X-Google-Original-Message-ID to Message-ID header...");
-    email = setHeaderValue(email, "Message-ID", googleReplacedMessageId);
-  }
-
-  return email;
-}
-
-
-export type SignatureType = 'DKIM' | 'ARC' | 'AS';
+export type SignatureType = "DKIM" | "ARC" | "AS";
 
 export type ParsedHeaders = ReturnType<typeof parseHeaders>;
 
-export type Parsed = ParsedHeaders['parsed'][0];
+export type Parsed = ParsedHeaders["parsed"][0];
 
-export type ParseDkimHeaders = ReturnType<typeof parseDkimHeaders>
+export type ParseDkimHeaders = ReturnType<typeof parseDkimHeaders>;
 
-export type SigningHeaderLines = ReturnType<typeof getSigningHeaderLines>
+export type SigningHeaderLines = ReturnType<typeof getSigningHeaderLines>;
 
 export interface Options {
   signatureHeaderLine: string;

packages/helpers/tests/__mocks__/localforage.ts

@@ -2,7 +2,6 @@ import fs from 'fs';
 import path from 'path';
 
 const getUncompressedTestFile = (): ArrayBuffer => {
-  console.log("__dirname", __dirname)
   const buffer = fs.readFileSync(path.join(__dirname, `../test-data/compressed-files/uncompressed-value.txt`));
   return buffer;
 }

packages/helpers/tests/dkim.test.ts

@@ -0,0 +1,88 @@
+import { verifyDKIMSignature } from "../src/dkim";
+import fs from "fs";
+import path from "path";
+
+jest.setTimeout(10000);
+
+describe("DKIM signature verification", () => {
+  it("should pass for valid email", async () => {
+    const email = fs.readFileSync(
+      path.join(__dirname, `test-data/email-good.eml`)
+    );
+
+    const result = await verifyDKIMSignature(email);
+
+    expect(result.signingDomain).toBe("icloud.com");
+  });
+
+  it("should fail for invalid selector", async () => {
+    const email = fs.readFileSync(
+      path.join(__dirname, `test-data/email-invalid-selector.eml`)
+    );
+
+    expect.assertions(1);
+
+    try {
+      await verifyDKIMSignature(email);
+    } catch (e) {
+      expect(e.message).toBe(
+        "DKIM signature verification failed for domain icloud.com. Reason: no key"
+      );
+    }
+  });
+
+  it("should fail for tampered body", async () => {
+    const email = fs.readFileSync(
+      path.join(__dirname, `test-data/email-body-tampered.eml`)
+    );
+
+    expect.assertions(1);
+
+    try {
+      await verifyDKIMSignature(email);
+    } catch (e) {
+      expect(e.message).toBe(
+        "DKIM signature verification failed for domain icloud.com. Reason: body hash did not verify"
+      );
+    }
+  });
+
+  it("should fail for when DKIM signature is not present for domain", async () => {
+    // In this email From address is [email protected], but the DKIM signature is only for icloud.com
+    const email = fs.readFileSync(
+      path.join(__dirname, `test-data/email-invalid-domain.eml`)
+    );
+
+    expect.assertions(1);
+
+    try {
+      await verifyDKIMSignature(email);
+    } catch (e) {
+      expect(e.message).toBe(
+        "DKIM signature not found for domain gmail.com"
+      );
+    }
+  });
+
+  it("should be able to override domain", async () => {
+    // From address domain is icloud.com
+    const email = fs.readFileSync(
+      path.join(__dirname, `test-data/email-different-domain.eml`)
+    );
+
+    // Should pass with default domain
+    await verifyDKIMSignature(email);
+
+    // Should fail because the email wont have a DKIM signature with the overridden domain
+    // Can be replaced with a better test email where signer is actually 
+    // different from From domain and the below check pass.
+    expect.assertions(1);
+    try {
+      await verifyDKIMSignature(email, "domain.com");
+    } catch (e) {
+      expect(e.message).toBe(
+        "DKIM signature not found for domain domain.com"
+      );
+    }
+  });
+});

packages/helpers/tests/test-data/email-body-tampered.eml

@@ -0,0 +1,18 @@
+DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=icloud.com; s=1a1hai; t=1693038337; bh=7xQMDuoVVU4m0W0WRVSrVXMeGSIASsnucK9dJsrc+vU=; h=from:Content-Type:Mime-Version:Subject:Message-Id:Date:to; b=EhLyVPpKD7d2/+h1nrnu+iEEBDfh6UWiAf9Y5UK+aPNLt3fAyEKw6Ic46v32NOcZD
+	 M/zhXWucN0FXNiS0pz/QVIEy8Bcdy7eBZA0QA1fp8x5x5SugDELSRobQNbkOjBg7Mx
+	 VXy7h4pKZMm/hKyhvMZXK4AX9fSoXZt4VGlAFymFNavfdAeKgg/SHXLds4lOPJV1wR
+	 2E21g853iz5m/INq3uK6SQKzTnz/wDkdyiq90gC0tHQe8HpDRhPIqgL5KSEpuvUYmJ
+	 wjEOwwHqP6L3JfEeROOt6wyuB1ah7wgRvoABOJ81+qLYRn3bxF+y1BC+PwFd5yFWH5
+	 Ry43lwp1/3+sA==
+from: [email protected]
+Content-Type: text/plain; charset=us-ascii
+Content-Transfer-Encoding: 7bit
+Mime-Version: 1.0 (Mac OS X Mail 16.0 \(3731.500.231\))
+Subject: Hello
+Message-Id: <[email protected]>
+Date: Sat, 26 Aug 2023 12:25:22 +0400
+to: [email protected]
+
+Hello,
+
+bla bla bla

packages/helpers/tests/test-data/email-different-domain.eml

@@ -0,0 +1,18 @@
+DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=icloud.com; s=1a1hai; t=1693038337; bh=7xQMDuoVVU4m0W0WRVSrVXMeGSIASsnucK9dJsrc+vU=; h=from:Content-Type:Mime-Version:Subject:Message-Id:Date:to; b=EhLyVPpKD7d2/+h1nrnu+iEEBDfh6UWiAf9Y5UK+aPNLt3fAyEKw6Ic46v32NOcZD
+	 M/zhXWucN0FXNiS0pz/QVIEy8Bcdy7eBZA0QA1fp8x5x5SugDELSRobQNbkOjBg7Mx
+	 VXy7h4pKZMm/hKyhvMZXK4AX9fSoXZt4VGlAFymFNavfdAeKgg/SHXLds4lOPJV1wR
+	 2E21g853iz5m/INq3uK6SQKzTnz/wDkdyiq90gC0tHQe8HpDRhPIqgL5KSEpuvUYmJ
+	 wjEOwwHqP6L3JfEeROOt6wyuB1ah7wgRvoABOJ81+qLYRn3bxF+y1BC+PwFd5yFWH5
+	 Ry43lwp1/3+sA==
+from: [email protected]
+Content-Type: text/plain; charset=us-ascii
+Content-Transfer-Encoding: 7bit
+Mime-Version: 1.0 (Mac OS X Mail 16.0 \(3731.500.231\))
+Subject: Hello
+Message-Id: <[email protected]>
+Date: Sat, 26 Aug 2023 12:25:22 +0400
+to: [email protected]
+
+Hello,
+
+How are you?

packages/helpers/tests/test-data/email-good.eml

@@ -0,0 +1,18 @@
+DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=icloud.com; s=1a1hai; t=1693038337; bh=7xQMDuoVVU4m0W0WRVSrVXMeGSIASsnucK9dJsrc+vU=; h=from:Content-Type:Mime-Version:Subject:Message-Id:Date:to; b=EhLyVPpKD7d2/+h1nrnu+iEEBDfh6UWiAf9Y5UK+aPNLt3fAyEKw6Ic46v32NOcZD
+	 M/zhXWucN0FXNiS0pz/QVIEy8Bcdy7eBZA0QA1fp8x5x5SugDELSRobQNbkOjBg7Mx
+	 VXy7h4pKZMm/hKyhvMZXK4AX9fSoXZt4VGlAFymFNavfdAeKgg/SHXLds4lOPJV1wR
+	 2E21g853iz5m/INq3uK6SQKzTnz/wDkdyiq90gC0tHQe8HpDRhPIqgL5KSEpuvUYmJ
+	 wjEOwwHqP6L3JfEeROOt6wyuB1ah7wgRvoABOJ81+qLYRn3bxF+y1BC+PwFd5yFWH5
+	 Ry43lwp1/3+sA==
+from: [email protected]
+Content-Type: text/plain; charset=us-ascii
+Content-Transfer-Encoding: 7bit
+Mime-Version: 1.0 (Mac OS X Mail 16.0 \(3731.500.231\))
+Subject: Hello
+Message-Id: <[email protected]>
+Date: Sat, 26 Aug 2023 12:25:22 +0400
+to: [email protected]
+
+Hello,
+
+How are you?

packages/helpers/tests/test-data/email-invalid-domain.eml

@@ -0,0 +1,18 @@
+DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=icloud.com; s=1a1hai; t=1693038337; bh=7xQMDuoVVU4m0W0WRVSrVXMeGSIASsnucK9dJsrc+vU=; h=from:Content-Type:Mime-Version:Subject:Message-Id:Date:to; b=EhLyVPpKD7d2/+h1nrnu+iEEBDfh6UWiAf9Y5UK+aPNLt3fAyEKw6Ic46v32NOcZD
+	 M/zhXWucN0FXNiS0pz/QVIEy8Bcdy7eBZA0QA1fp8x5x5SugDELSRobQNbkOjBg7Mx
+	 VXy7h4pKZMm/hKyhvMZXK4AX9fSoXZt4VGlAFymFNavfdAeKgg/SHXLds4lOPJV1wR
+	 2E21g853iz5m/INq3uK6SQKzTnz/wDkdyiq90gC0tHQe8HpDRhPIqgL5KSEpuvUYmJ
+	 wjEOwwHqP6L3JfEeROOt6wyuB1ah7wgRvoABOJ81+qLYRn3bxF+y1BC+PwFd5yFWH5
+	 Ry43lwp1/3+sA==
+from: [email protected]
+Content-Type: text/plain; charset=us-ascii
+Content-Transfer-Encoding: 7bit
+Mime-Version: 1.0 (Mac OS X Mail 16.0 \(3731.500.231\))
+Subject: Hello
+Message-Id: <[email protected]>
+Date: Sat, 26 Aug 2023 12:25:22 +0400
+to: [email protected]
+
+Hello,
+
+How are you?

packages/helpers/tests/test-data/email-invalid-selector.eml

@@ -0,0 +1,18 @@
+DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=icloud.com; s=2a1hai; t=1693038337; bh=7xQMDuoVVU4m0W0WRVSrVXMeGSIASsnucK9dJsrc+vU=; h=from:Content-Type:Mime-Version:Subject:Message-Id:Date:to; b=EhLyVPpKD7d2/+h1nrnu+iEEBDfh6UWiAf9Y5UK+aPNLt3fAyEKw6Ic46v32NOcZD
+	 M/zhXWucN0FXNiS0pz/QVIEy8Bcdy7eBZA0QA1fp8x5x5SugDELSRobQNbkOjBg7Mx
+	 VXy7h4pKZMm/hKyhvMZXK4AX9fSoXZt4VGlAFymFNavfdAeKgg/SHXLds4lOPJV1wR
+	 2E21g853iz5m/INq3uK6SQKzTnz/wDkdyiq90gC0tHQe8HpDRhPIqgL5KSEpuvUYmJ
+	 wjEOwwHqP6L3JfEeROOt6wyuB1ah7wgRvoABOJ81+qLYRn3bxF+y1BC+PwFd5yFWH5
+	 Ry43lwp1/3+sA==
+from: [email protected]
+Content-Type: text/plain; charset=us-ascii
+Content-Transfer-Encoding: 7bit
+Mime-Version: 1.0 (Mac OS X Mail 16.0 \(3731.500.231\))
+Subject: Hello
+Message-Id: <[email protected]>
+Date: Sat, 26 Aug 2023 12:25:22 +0400
+to: [email protected]
+
+Hello,
+
+How are you?