Support comments inside comments up to a recursion of 3 (#466)

CHANGELOG.md

@@ -15,6 +15,7 @@ All notable changes to this project will be documented in this file.
 ### Fixes
 
 - Fixed potential parsing error when extracting the received time from the last Received header (#455).
+- When parsing now support comments inside comments up to a recursion of 3 (#466).
 
 ### Other
 

modules/rfcParser.mjs.js

@@ -1,7 +1,7 @@
 /**
  * RegExp pattern for ABNF definitions in various RFCs.
  *
- * Copyright (c) 2020-2023 Philippe Lieser
+ * Copyright (c) 2020-2025 Philippe Lieser
  *
  * This software is licensed under the terms of the MIT License.
  *
@@ -43,8 +43,13 @@ export default class RfcParser {
 	static get FWS_op() { return `${this.FWS}?`; }
 	// Note: this is incomplete (obs-ctext is missing)
 	static get ctext() { return "[!-'*-[\\]-~]"; }
-	// Note: this is incomplete (comment is missing)
-	static get ccontent() { return `(?:${this.ctext}|${this.quoted_pair})`; }
+	// Note: There is a recursion in ccontent/comment, which is not supported by the RegExp in JavaScript.
+	// We currently unroll it to support a depth of up to 3 comments.
+	static get ccontent_2() { return `(?:${this.ctext}|${this.quoted_pair})`; }
+	static get comment_2() { return `\\((?:${this.FWS_op}${this.ccontent_2})*${this.FWS_op}\\)`; }
+	static get ccontent_1() { return `(?:${this.ctext}|${this.quoted_pair}|${this.comment_2})`; }
+	static get comment_1() { return `\\((?:${this.FWS_op}${this.ccontent_1})*${this.FWS_op}\\)`; }
+	static get ccontent() { return `(?:${this.ctext}|${this.quoted_pair}|${this.comment_1})`; }
 	static get comment() { return `\\((?:${this.FWS_op}${this.ccontent})*${this.FWS_op}\\)`; }
 	static get CFWS() { return `(?:(?:(?:${this.FWS_op}${this.comment})+${this.FWS_op})|${this.FWS})`; }
 	// Note: helper only, not part of the RFC

test/unittest/arhParserSpec.mjs.js

@@ -1,5 +1,5 @@
 /**
- * Copyright (c) 2020-2023 Philippe Lieser
+ * Copyright (c) 2020-2023;2025 Philippe Lieser
  *
  * This software is licensed under the terms of the MIT License.
  *
@@ -167,6 +167,15 @@ describe("ARH Parser [unittest]", function () {
 			expect(res.resinfo[0]?.method).to.be.equal("unknown");
 			expect(res.resinfo[0]?.result).to.be.equal("foo");
 		});
+		it("Comments in comments", function () {
+			const res = ArhParser.parse(
+				"Authentication-Results: example.com;\r\n" +
+				"          dkim=pass (good (comment (another)) signature(s)) header.d=example.com\r\n");
+			expect(res.authserv_id).to.be.equal("example.com");
+			expect(res.resinfo.length).to.be.equal(1);
+			expect(res.resinfo[0]?.method).to.be.equal("dkim");
+			expect(res.resinfo[0]?.result).to.be.equal("pass");
+		});
 	});
 	describe("Relaxed parsing", function () {
 		it("Trailing ;", function () {
@@ -235,6 +244,16 @@ describe("ARH Parser [unittest]", function () {
 				"Authentication-Results: example.com; dmarc=foo\r\n"
 			)).to.throw();
 		});
+		it("Comments with mismatching number of brackets", function () {
+			expect(() => ArhParser.parse(
+				"Authentication-Results: example.com;\r\n" +
+				"          dkim=pass (good (comment (another))) signature(s)) header.d=example.com\r\n"
+			)).to.throw();
+			expect(() => ArhParser.parse(
+				"Authentication-Results: example.com;\r\n" +
+				"          dkim=pass ((good (comment (another)) signature(s)) header.d=example.com\r\n"
+			)).to.throw();
+		});
 	});
 	describe("DKIM results", function () {
 		it("AUID with local part", function () {