MimePart: do not quote a display name that is MIME-encoded

docs/internals.md

@@ -66,6 +66,17 @@ Sub-parts are serialized recursively; a `boundary=` is appended to `Content-Type
   `Content-Disposition` filenames (quoted, RFC 2231 value), and plain values.
   Folding at `LineLength` (76) with tab continuation is volatile line-level
   mechanics — do not treat its exact offsets as contract.
+- **A display name is quoted on two different tests, one per path.** Emitted
+  literally, a `phrase` holding anything outside `atext` (a dot, a comma, ...) has
+  to become a `quoted-string` — that is real RFC 5322 syntax and the quotes are
+  delimiters. Emitted as an encoded-word, quotes are *not* syntax: per RFC 2047
+  §6.2 decoding happens **after** the field body is parsed into tokens, so the
+  encoding already shields whatever the name contains, and quotes added before
+  encoding land inside the base64 payload and decode as part of the name the
+  recipient sees. The encoded path therefore quotes only for receivers that
+  re-parse the decoded phrase, and only for `,;:<>@"\` — characters able to
+  restructure an address list (#102 was a Gmail DKIM failure caused by a comma).
+  Diacritics and dots cannot restructure anything, so they stay bare.
 - `Message::$defaultHeaders` is a **mutable static** (`MIME-Version`,
   `X-Mailer`), applied in the constructor — changing it affects every
   subsequently created message, and since `X-Mailer` is in DKIM's default

src/Mail/MimePart.php

@@ -10,7 +10,7 @@
 use Nette;
 use Nette\Utils\Arrays;
 use Nette\Utils\Strings;
-use function addcslashes, array_keys, base64_encode, chunk_split, iconv_mime_encode, is_array, is_string, ltrim, preg_match, preg_replace, quoted_printable_encode, rtrim, sprintf, str_ends_with, str_repeat, str_replace, strcasecmp, stripslashes, strlen, strrpos, strspn, substr;
+use function addcslashes, array_keys, base64_encode, chunk_split, iconv_mime_encode, is_array, is_string, ltrim, preg_match, preg_replace, quoted_printable_encode, rtrim, sprintf, str_ends_with, str_repeat, str_replace, strcasecmp, stripslashes, strlen, strpbrk, strrpos, strspn, substr;
 
 
 /**
@@ -303,15 +303,14 @@ public function getEncodedMessage(): string
 	 */
 	private static function encodeSequence(string $s, int &$offset = 0, ?int $type = null): string
 	{
-		$escape = fn($s) => preg_match('#[^ a-zA-Z0-9!\#$%&\'*+/?^_`{|}~-]#', $s) === 1 // RFC 2822 atext except =
-			? sprintf('"%s"', addcslashes($s, '"\\'))
-			: $s;
+		$escape = fn($s) => sprintf('"%s"', addcslashes($s, '"\\'));
 
 		if (
 			(strlen($s) < self::LineLength - 3) && // 3 is tab + quotes
 			strspn($s, "!\"#$%&\\'()*+,-./0123456789:;<>@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^`abcdefghijklmnopqrstuvwxyz{|}~=? _\r\n\t") === strlen($s)
 		) {
-			if ($type !== null) {
+			// emitted literally, so anything outside atext has to become a quoted-string
+			if ($type !== null && preg_match('#[^ a-zA-Z0-9!\#$%&\'*+/?^_`{|}~-]#', $s) === 1) { // RFC 2822 atext except =
 				$s = $escape($s);
 			}
 
@@ -324,7 +323,10 @@ private static function encodeSequence(string $s, int &$offset = 0, ?int $type =
 			$offset = 1;
 		}
 
-		if ($type === self::SequenceWord) {
+		// RFC 2047 decoding happens after the field is parsed, so the encoding already shields
+		// the phrase. Quote it only for receivers that re-parse the decoded text, and only for
+		// characters able to restructure the address list - quotes added here stay visible.
+		if ($type === self::SequenceWord && strpbrk($s, ',;:<>@"\\') !== false) {
 			$s = $escape($s);
 		}
 

tests/Mail/Mail.email.encodedName.phpt

@@ -0,0 +1,81 @@
+<?php declare(strict_types=1);
+
+/**
+ * Test: Nette\Mail\Message quotes an encoded display name only when it could be re-parsed.
+ */
+
+use Nette\Mail\Message;
+use Tester\Assert;
+
+
+require __DIR__ . '/../bootstrap.php';
+
+
+test('ASCII name outside atext is a real quoted-string', function () {
+	$mail = new Message;
+	$mail->setFrom('doe@example.com', 'John.Doe');
+
+	Assert::same('"John.Doe" <doe@example.com>', $mail->getEncodedHeader('From'));
+});
+
+
+test('ASCII name within atext is left alone', function () {
+	$mail = new Message;
+	$mail->setFrom('doe@example.com', 'John Doe');
+
+	Assert::same('John Doe <doe@example.com>', $mail->getEncodedHeader('From'));
+});
+
+
+test('encoded name carries no quotes', function () {
+	$mail = new Message;
+	$mail->setFrom('doe@example.com', 'Jan Nováček');
+
+	$header = $mail->getEncodedHeader('From');
+	Assert::same('=?UTF-8?B?SmFuIE5vdsOhxI1law==?= <doe@example.com>', $header);
+	Assert::same('Jan Nováček <doe@example.com>', iconv_mime_decode($header, 0, 'UTF-8'));
+});
+
+
+test('a dot does not make an encoded name quoted', function () {
+	$mail = new Message;
+	$mail->setFrom('doe@example.com', 'Objednávky domena.cz');
+
+	Assert::same(
+		'Objednávky domena.cz <doe@example.com>',
+		iconv_mime_decode($mail->getEncodedHeader('From'), 0, 'UTF-8'),
+	);
+});
+
+
+test('a comma keeps the encoded name quoted', function () {
+	$mail = new Message;
+	$mail->setFrom('doe@example.com', 'Nováček, Jan');
+
+	Assert::same(
+		'"Nováček, Jan" <doe@example.com>',
+		iconv_mime_decode($mail->getEncodedHeader('From'), 0, 'UTF-8'),
+	);
+});
+
+
+test('a quote in an encoded name is escaped', function () {
+	$mail = new Message;
+	$mail->setFrom('doe@example.com', 'Jan "Honza" Nováček');
+
+	Assert::same(
+		'"Jan \"Honza\" Nováček" <doe@example.com>',
+		iconv_mime_decode($mail->getEncodedHeader('From'), 0, 'UTF-8'),
+	);
+});
+
+
+test('an address-like name stays quoted', function () {
+	$mail = new Message;
+	$mail->setFrom('doe@example.com', 'Nováček <spoof@example.com>');
+
+	Assert::contains(
+		'"Nováček <spoof@example.com>"',
+		iconv_mime_decode($mail->getEncodedHeader('From'), 0, 'UTF-8'),
+	);
+});

tests/Mail/Mail.email.multiple.phpt

@@ -32,9 +32,9 @@ Assert::match(<<<'EOD'
 	X-Mailer: Nette Framework
 	Date: %a%
 	From: John Doe <doe@example.com>
-	To: Lady Jane <jane@example.foo>,williams@example.foo,=?UTF-8?B?Ig==?=
-		=?UTF-8?B?xZhlaG/FmSDFmMOtemVrIg==?= <rizek@example.foo>,
-		=?UTF-8?B?Ikx1Ym/FoSBTbWHFvsOhayI=?= <smazak@example.foo>
+	To: Lady Jane <jane@example.foo>,williams@example.foo,=?UTF-8?B?xZg=?=
+		=?UTF-8?B?ZWhvxZkgxZjDrXplaw==?= <rizek@example.foo>,
+		=?UTF-8?B?THVib8WhIFNtYcW+w6Fr?= <smazak@example.foo>
 	Subject: Hello Jane!
 	Message-ID: <%S%@%S%>
 	Content-Type: text/plain; charset=UTF-8

tests/Mail/Mail.email.phpt

@@ -39,17 +39,21 @@ Assert::match(<<<'EOD'
 	MIME-Version: 1.0
 	X-Mailer: Nette Framework
 	Date: %a%
-	From: =?UTF-8?B?IsW9bHXFpW91xI1rw70ga8WvxYgi?= <kun1@example.com>
-	Reply-To: =?UTF-8?B?IsW9bHXFpW91xI1rw70ga8WvxYgi?= <kun2@example.com>,
+	From: =?UTF-8?B?xb1sdcWlb3XEjWvDvSBrxa/FiA==?= <kun1@example.com>
+	Reply-To: =?UTF-8?B?xb1sdcWlb3XEjWvDvSBrxa/FiA==?= <kun2@example.com>,
 		John Doe <doe2@example.com>
 	To: =?UTF-8?B?IsW9bHXFpW91xI1rw70gXCJrxa/FiFwiIg==?= <kun3@example.com>,
 		John 'jd' Doe <doe3@example.com>
 	Cc: TheMail <nette@example.com>,John Doe <doe4@example.com>,"The.Mail"
 		 <nette2@example.com>
-	Bcc: =?UTF-8?B?IsW9bHXFpW91xI1rw70ga8WvxYgi?= <kun5@example.com>,
+	Bcc: =?UTF-8?B?xb1sdcWlb3XEjWvDvSBrxa/FiA==?= <kun5@example.com>,
 		doe5@example.com
 	Return-Path: doe@example.com
 	Message-ID: <%a%@%a%>
 	Content-Type: text/plain; charset=UTF-8
 	Content-Transfer-Encoding: 7bit
 	EOD, TestMailer::$output);
+
+// a plain diacritic name decodes bare, one holding a quote keeps the quoted-string
+Assert::match('Žluťoučký kůň', iconv_mime_decode('=?UTF-8?B?xb1sdcWlb3XEjWvDvSBrxa/FiA==?='));
+Assert::match('"Žluťoučký \"kůň\""', iconv_mime_decode('=?UTF-8?B?IsW9bHXFpW91xI1rw70gXCJrxa/FiFwiIg==?='));

tests/Mail/Mail.headers.002.phpt

@@ -49,4 +49,6 @@ Assert::match(<<<'EOD'
 	Content-Transfer-Encoding: 7bit
 	EOD, TestMailer::$output);
 
+// the comma could restructure the address list for a receiver that re-parses the decoded
+// phrase, so this name keeps its quotes (see #102)
 Assert::match('"Kdo uteče, obědvá"', iconv_mime_decode('=?UTF-8?B?IktkbyB1dGXEjWUsIG9ixJtkdsOhIg==?='));

tests/Mail/Mail.longLines.phpt

@@ -32,9 +32,9 @@ Assert::match(<<<'EOD'
 	X-Mailer: Nette Framework
 	Date: %a%
 	From: John Doe <doe@example.com>
-	To: Lady Jane <jane@example.foo>,williams@example.foo,=?UTF-8?B?Ig==?=
-		=?UTF-8?B?xZhlaG/FmSDFmMOtemVrIg==?= <rizek@example.foo>,
-		=?UTF-8?B?Ikx1Ym/FoSBTbWHFvsOhayI=?= <smazak@example.foo>
+	To: Lady Jane <jane@example.foo>,williams@example.foo,=?UTF-8?B?xZg=?=
+		=?UTF-8?B?ZWhvxZkgxZjDrXplaw==?= <rizek@example.foo>,
+		=?UTF-8?B?THVib8WhIFNtYcW+w6Fr?= <smazak@example.foo>
 	Subject: Hello Jane!
 	Message-ID: <%S%@%S%>
 	Content-Type: text/plain; charset=UTF-8