fix(dkim): Added new output property mimeStructureStart

examples/authenticate.js

@@ -8,10 +8,11 @@ const fs = require('fs');
 const main = async () => {
     let message = await fs.promises.readFile(process.argv[2] || __dirname + '/../test/fixtures/message4.eml');
     let res = await authenticate(message, {
-        ip: '217.146.67.33',
-        helo: 'uvn-67-33.tll01.zonevs.eu',
+        //ip: '217.146.67.33',
+        //helo: 'uvn-67-33.tll01.zonevs.eu',
         mta: 'mx.ethereal.email',
-        sender: '[email protected]',
+        //sender: '[email protected]',
+        trustReceived: true,
         // optional. add ARC seal if possible
         seal: {
             signingDomain: 'tahvel.info',

lib/dkim/body/relaxed.js

@@ -3,6 +3,7 @@
 'use strict';
 
 const crypto = require('crypto');
+const { MimeStructureStartFinder } = require('../mime-structure-start-finder');
 
 const CHAR_CR = 0x0d;
 const CHAR_LF = 0x0a;
@@ -39,9 +40,20 @@ class RelaxedHash {
         this.maxSizeReached = maxBodyLength === 0;
 
         this.emptyLinesQueue = [];
+
+        this.mimeStructureStartFinder = new MimeStructureStartFinder();
+    }
+
+    setContentType(contentTypeObj) {
+        if (/^multipart\//i.test(contentTypeObj.value) && contentTypeObj.params.boundary) {
+            this.mimeStructureStartFinder.setBoundary(contentTypeObj.params.boundary);
+        }
     }
 
     _updateBodyHash(chunk) {
+        // serach through the entire document, not just signed part
+        this.mimeStructureStartFinder.update(chunk);
+
         this.canonicalizedLength += chunk.length;
 
         if (this.maxSizeReached) {
@@ -270,6 +282,10 @@ class RelaxedHash {
         // finalize
         return this.bodyHash.digest(encoding);
     }
+
+    getMimeStructureStart() {
+        return this.mimeStructureStartFinder.getMimeStructureStart();
+    }
 }
 
 module.exports = { RelaxedHash };

lib/dkim/body/simple.js

@@ -1,6 +1,7 @@
 'use strict';
 
 const crypto = require('crypto');
+const { MimeStructureStartFinder } = require('../mime-structure-start-finder');
 
 /**
  * Class for calculating body hash of an email message body stream
@@ -30,9 +31,20 @@ class SimpleHash {
         this.maxSizeReached = maxBodyLength === 0;
 
         this.lastNewline = false;
+
+        this.mimeStructureStartFinder = new MimeStructureStartFinder();
+    }
+
+    setContentType(contentTypeObj) {
+        if (/^multipart\//i.test(contentTypeObj.value) && contentTypeObj.params.boundary) {
+            this.mimeStructureStartFinder.setBoundary(contentTypeObj.params.boundary);
+        }
     }
 
     _updateBodyHash(chunk) {
+        // serach through the entire document, not just signed part
+        this.mimeStructureStartFinder.update(chunk);
+
         this.canonicalizedLength += chunk.length;
 
         if (this.maxSizeReached) {
@@ -115,6 +127,10 @@ class SimpleHash {
 
         return this.bodyHash.digest(encoding);
     }
+
+    getMimeStructureStart() {
+        return this.mimeStructureStartFinder.getMimeStructureStart();
+    }
 }
 
 module.exports = { SimpleHash };

lib/dkim/dkim-verifier.js

@@ -8,6 +8,7 @@ const { getARChain } = require('../arc');
 const addressparser = require('nodemailer/lib/addressparser');
 const crypto = require('crypto');
 const { v4: uuidv4 } = require('uuid');
+const libmime = require('libmime');
 
 class DkimVerifier extends MessageParser {
     constructor(options) {
@@ -147,6 +148,18 @@ class DkimVerifier extends MessageParser {
             if (!this.bodyHashes.has(signatureHeader.bodyHashKey)) {
                 this.bodyHashes.set(signatureHeader.bodyHashKey, dkimBody(signatureHeader.bodyCanon, signatureHeader.hashAlgo, signatureHeader.maxBodyLength));
             }
+
+            let contentTypeHeader = this.headers.parsed.findLast(header => header.key === 'content-type');
+            if (contentTypeHeader) {
+                let line = contentTypeHeader.line.toString();
+                if (line.indexOf(':') >= 0) {
+                    line = line.substring(line.indexOf(':') + 1).trim();
+                }
+                const parsedContentType = libmime.parseHeaderValue(line);
+                for (let hasher of this.bodyHashes.values()) {
+                    hasher.setContentType(parsedContentType);
+                }
+            }
         }
     }
 
@@ -165,6 +178,7 @@ class DkimVerifier extends MessageParser {
             // convert bodyHashes from hash objects to base64 strings
             for (let [key, bodyHash] of this.bodyHashes.entries()) {
                 this.bodyHashes.get(key).hash = bodyHash.digest('base64');
+                this.bodyHashes.get(key).mimeStructureStart = bodyHash.getMimeStructureStart();
             }
 
             for (let signatureHeader of this.signatureHeaders) {
@@ -210,7 +224,9 @@ class DkimVerifier extends MessageParser {
                         : false;
                 }
 
-                let bodyHash = this.bodyHashes.get(signatureHeader.bodyHashKey)?.hash;
+                const bodyHash = this.bodyHashes.get(signatureHeader.bodyHashKey)?.hash;
+                const mimeStructureStart = this.bodyHashes.get(signatureHeader.bodyHashKey)?.mimeStructureStart;
+
                 if (signatureHeader.parsed?.bh?.value !== bodyHash) {
                     status.result = 'neutral';
                     status.comment = `body hash did not verify`;
@@ -344,6 +360,10 @@ class DkimVerifier extends MessageParser {
                     result.canonBodyLengthLimited = false;
                 }
 
+                if (typeof mimeStructureStart === 'number') {
+                    result.mimeStructureStart = mimeStructureStart;
+                }
+
                 if (publicKey) {
                     result.publicKey = publicKey.toString();
                 }

lib/dkim/mime-structure-start-finder.js

@@ -0,0 +1,85 @@
+'use strict';
+
+class MimeStructureStartFinder {
+    constructor() {
+        this.byteCache = [];
+
+        this.matchFound = false;
+        this.noMatch = false;
+        this.lineStart = -1;
+
+        this.prevChunks = 0;
+
+        this.mimeStructureStart = -1;
+    }
+
+    setBoundary(boundary) {
+        this.boundary = (boundary || '').toString().trim();
+
+        this.boundaryBuf = Array.from(Buffer.from(`--${this.boundary}`));
+        this.boundaryBufLen = this.boundaryBuf.length;
+    }
+
+    update(chunk) {
+        if (this.matchFound || !this.boundary) {
+            return;
+        }
+
+        for (let i = 0, bufLen = chunk.length; i < bufLen; i++) {
+            let c = chunk[i];
+
+            // check ending
+            if (c === 0x0a || c === 0x0d) {
+                if (!this.noMatch && this.byteCache.length === this.boundaryBufLen) {
+                    // match found
+                    this.matchFound = true;
+                    this.mimeStructureStart = this.lineStart;
+                    break;
+                }
+                // reset counter
+                this.lineStart = -1;
+                this.noMatch = false;
+                this.byteCache = [];
+                continue;
+            }
+
+            if (this.noMatch) {
+                // no need to look
+                continue;
+            }
+
+            if (this.lineStart < 0) {
+                this.lineStart = this.prevChunks + i;
+            }
+
+            if (this.byteCache.length >= this.boundaryBufLen) {
+                this.noMatch = true;
+                continue;
+            }
+
+            const expectingByte = this.boundaryBuf[this.byteCache.length];
+            if (expectingByte !== c) {
+                this.noMatch = true;
+                continue;
+            }
+            this.byteCache[this.byteCache.length] = c;
+        }
+
+        this.prevChunks += chunk.length;
+    }
+
+    getMimeStructureStart() {
+        if (!this.boundary) {
+            return 0;
+        }
+
+        if (!this.matchFound && !this.noMatch && this.byteCache.length === this.boundaryBufLen) {
+            this.matchFound = true;
+            this.mimeStructureStart = this.lineStart;
+        }
+
+        return this.mimeStructureStart;
+    }
+}
+
+module.exports = { MimeStructureStartFinder };