Allow underscores in cnames

Author: tvlooy

src/Structure/Dns/AbstractDnsRecord.php

@@ -66,7 +66,7 @@ public function getObject(): \stdClass
         return $obj;
     }
 
-    protected function validateHostname(string $hostname, bool $allowOrigin = true): string
+    protected function validateHostname(string $hostname, bool $allowOrigin = true, bool $lax = false): string
     {
         if ($allowOrigin && in_array($hostname, ['', '@', '*'])) {
             return $hostname;
@@ -79,9 +79,12 @@ protected function validateHostname(string $hostname, bool $allowOrigin = true):
 
             // remove special characters from labels, as we consider them valid, then send through filter_var
             $filtered = preg_replace('(^\*\._|^\*\.|^_|\._|\#)', '', $ascii);
+            if ($lax) {
+                $filtered = str_replace('_', '', $filtered);
+            }
             $filtered = filter_var($filtered, FILTER_VALIDATE_DOMAIN, FILTER_FLAG_HOSTNAME);
 
-            // did the check pass and did we removed leading underscores? if so, use original value;
+            // did the check pass and did we remove leading underscores? if so, use original value;
             if (false !== $filtered && $filtered !== $hostname) {
                 $filtered = $hostname;
             }

src/Structure/Dns/DnsCNAMERecord.php

@@ -20,7 +20,7 @@ public function getContent(): string
     private function setContent(string $content): void
     {
         try {
-            $filtered = $this->validateHostname($content);
+            $filtered = $this->validateHostname($content, lax: true);
             $this->content = $filtered;
         } catch (\Exception $exception) {
             throw new \InvalidArgumentException('Invalid value for content: "'.$content.'"');

tests/Structure/Dns/DnsTest.php

@@ -162,7 +162,7 @@ public function testDNSCNAMERecord()
         $this->assertEquals($r->getContent(), $o->content);
     }
 
-    /** @dataProvider dataHostnameValues */
+    /** @dataProvider dataHostnameValuesCname */
     public function testDNSCNAMERecordContentValidation($address, $isValid)
     {
         if (!$isValid) {
@@ -450,6 +450,25 @@ public static function dataHostnameValues()
         ];
     }
 
+    public static function dataHostnameValuesCname()
+    {
+        return [
+            ['', true],
+            ['@', true],
+            ['example', true],
+            ['example.com', true],
+            ['example.com ', false],
+            [' example.com', false],
+            ['127.0.0.1', true],
+            ['2001:0db8:85a3:0000:0000:8a2e:0370:7334', false],
+            ['yellow-banana.example.com', true],
+            ['brown_banana.example.com', true],
+            ['_banana.example.com', true],
+            ['__banana.example.com', true],
+            ['-banana.example.com', false],
+        ];
+    }
+
     public static function dataHostnameValuesNoOrigin()
     {
         return [