Fix error when trying to persist non-utf-8 title

Author: acelaya

CHANGELOG.md

@@ -41,7 +41,12 @@ The format is based on [Keep a Changelog](https://keepachangelog.com), and this
 * [#2565](https://github.com/shlinkio/shlink/issues/2565) Remove explicit dependency in ext-json, since it's part of PHP since v8.0
 
 ### Fixed
-* *Nothing*
+* [#2564](https://github.com/shlinkio/shlink/issues/2564) Fix error when trying to persist non-utf-8 title without being able to determine its original charset for parsing.
+
+  Now, when resolving a website's charset, two improvements have been introduced:
+
+  1. If the `Content-Type` header does not define the charset, we fall back to `<meta charset>` or `<meta http-equiv="Content-Type">`.
+  2. If it's still not possible to determine the charset, we ignore the auto-resolved title, to avoid other encoding errors further down the line.
 
 
 ## [4.6.0] - 2025-11-01

module/Core/src/ShortUrl/Helper/ShortUrlTitleResolutionHelper.php

@@ -10,6 +10,7 @@
 use GuzzleHttp\RequestOptions;
 use Laminas\Stdlib\ErrorHandler;
 use Psr\Http\Message\ResponseInterface;
+use Psr\Http\Message\StreamInterface;
 use Psr\Log\LoggerInterface;
 use Shlinkio\Shlink\Core\Config\Options\UrlShortenerOptions;
 use Throwable;
@@ -30,10 +31,12 @@
     public const string CHROME_USER_AGENT = 'Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) '
         . 'Chrome/121.0.0.0 Safari/537.36';
 
-    // Matches the value inside a html title tag
+    /** Matches the value inside a html title tag */
     private const string TITLE_TAG_VALUE = '/<title[^>]*>(.*?)<\/title>/i';
-    // Matches the charset inside a Content-Type header
+    /** Matches the charset inside a Content-Type header */
     private const string CHARSET_VALUE = '/charset=([^;]+)/i';
+    /** Matches the charset from charset-related <meta /> tags */
+    private const string CHARSET_FROM_META = '/<meta\b[^>]*\bcharset\s*=\s*(?:["\']?)([^"\'\s>;]+)/i';
 
     /**
      * @param (Closure(): bool)|null $isIconvInstalled
@@ -83,7 +86,8 @@ private function fetchUrl(string $url): ResponseInterface|null
                 RequestOptions::IDN_CONVERSION => true,
                 // Making the request with a browser's user agent results in responses closer to a real user
                 RequestOptions::HEADERS => ['User-Agent' => self::CHROME_USER_AGENT],
-                RequestOptions::STREAM => true, // This ensures large files are not fully downloaded if not needed
+                // This ensures large files are not fully downloaded if not needed
+                RequestOptions::STREAM => true,
             ]);
         } catch (Throwable) {
             return null;
@@ -102,24 +106,56 @@ private function tryToResolveTitle(ResponseInterface $response, string $contentT
 
         // Try to match the title from the <title /> tag
         preg_match(self::TITLE_TAG_VALUE, $collectedBody, $titleMatches);
-        if (! isset($titleMatches[1])) {
+        $titleInOriginalEncoding = $titleMatches[1] ?? null;
+        if ($titleInOriginalEncoding === null) {
             return null;
         }
-
-        $titleInOriginalEncoding = $titleMatches[1];
-
-        // Get the page's charset from Content-Type header, or return title as is if not found
-        preg_match(self::CHARSET_VALUE, $contentType, $charsetMatches);
-        if (! isset($charsetMatches[1])) {
-            return $titleInOriginalEncoding;
+        ;
+        $pageCharset = $this->resolvePageCharset($contentType, $body, $collectedBody);
+        if ($pageCharset === null) {
+            // If it was not possible to determine the page's charset, ignore the title to avoid the risk of encoding
+            // errors when the value is persisted
+            return null;
         }
 
-        $pageCharset = $charsetMatches[1];
         return $this->encodeToUtf8WithMbString($titleInOriginalEncoding, $pageCharset)
             ?? $this->encodeToUtf8WithIconv($titleInOriginalEncoding, $pageCharset)
             ?? $titleInOriginalEncoding;
     }
 
+    /**
+     * Tries to resolve the page's charset by looking into the:
+     * 1. Content-Type header
+     * 2. <meta charset="???"> tag
+     * 3. <meta http-equiv="Content-Type" content="text/html; charset=???"> tag
+     *
+     * @param StreamInterface $body - The body stream, in case we need to continue reading from it
+     * @param string $collectedBody - The part of the body that has already been read while looking for the title
+     */
+    private function resolvePageCharset(string $contentType, StreamInterface $body, string $collectedBody): string|null
+    {
+        // First try to resolve the charset from the `Content-Type` header
+        preg_match(self::CHARSET_VALUE, $contentType, $charsetMatches);
+        $pageCharset = $charsetMatches[1] ?? null;
+        if ($pageCharset !== null) {
+            return $pageCharset;
+        }
+
+        $readCharsetFromMeta = static function (string $collectedBody): string|null {
+            preg_match(self::CHARSET_FROM_META, $collectedBody, $charsetFromMetaMatches);
+            return $charsetFromMetaMatches[1] ?? null;
+        };
+
+        // Continue reading the body, looking for any of the charset meta tags
+        $charsetFromMeta = $readCharsetFromMeta($collectedBody);
+        while ($charsetFromMeta === null && ! $body->eof()) {
+            $collectedBody .= $body->read(1024);
+            $charsetFromMeta = $readCharsetFromMeta($collectedBody);
+        }
+
+        return $charsetFromMeta;
+    }
+
     private function encodeToUtf8WithMbString(string $titleInOriginalEncoding, string $pageCharset): string|null
     {
         try {

module/Core/test/ShortUrl/Helper/ShortUrlTitleResolutionHelperTest.php

@@ -11,6 +11,7 @@
 use Laminas\Diactoros\Response;
 use Laminas\Diactoros\Response\JsonResponse;
 use Laminas\Diactoros\Stream;
+use PHPUnit\Framework\Attributes\AllowMockObjectsWithoutExpectations;
 use PHPUnit\Framework\Attributes\Test;
 use PHPUnit\Framework\Attributes\TestWith;
 use PHPUnit\Framework\MockObject\InvocationStubber;
@@ -23,7 +24,7 @@
 
 class ShortUrlTitleResolutionHelperTest extends TestCase
 {
-    private const string LONG_URL = 'http://foobar.com/12345/hello?foo=bar';
+    private const string LONG_URL = 'https://foobar.com/12345/hello?foo=bar';
 
     private MockObject & ClientInterface $httpClient;
     private MockObject & LoggerInterface $logger;
@@ -98,7 +99,6 @@ public function dataIsReturnedAsIsWhenTitleCannotBeResolvedFromResponse(): void
     }
 
     #[Test]
-    #[TestWith(['TEXT/html', false], 'no charset')]
     #[TestWith(['TEXT/html; charset=utf-8', false], 'mbstring-supported charset')]
     #[TestWith(['TEXT/html; charset=Windows-1255', true], 'mbstring-unsupported charset')]
     public function titleIsUpdatedWhenItCanBeResolvedFromResponse(string $contentType, bool $expectsWarning): void
@@ -120,6 +120,37 @@ public function titleIsUpdatedWhenItCanBeResolvedFromResponse(string $contentTyp
         self::assertEquals('Resolved "title"', $result->title);
     }
 
+    #[Test, AllowMockObjectsWithoutExpectations]
+    public function resolvedTitleIsIgnoredWhenCharsetCannotBeResolved(): void
+    {
+        $this->expectRequestToBeCalled()->willReturn($this->respWithTitle('text/html'));
+
+        $data = ShortUrlCreation::fromRawData(['longUrl' => self::LONG_URL]);
+        $result = $this->helper(autoResolveTitles: true, iconvEnabled: true)->processTitle($data);
+
+        self::assertSame($data, $result);
+        self::assertNull($result->title);
+    }
+
+    #[Test, AllowMockObjectsWithoutExpectations]
+    #[TestWith(['<meta charset="utf-8">'])]
+    #[TestWith(['<meta charset="utf-8" />'])]
+    #[TestWith(['<meta http-equiv="Content-Type" content="text/html; charset=utf-8">'])]
+    #[TestWith(['<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />'])]
+    public function pageCharsetCanBeReadFromMeta(string $extraContent): void
+    {
+        $this->expectRequestToBeCalled()->willReturn($this->respWithTitle(
+            contentType: 'text/html',
+            extraContent: $extraContent,
+        ));
+
+        $data = ShortUrlCreation::fromRawData(['longUrl' => self::LONG_URL]);
+        $result = $this->helper(autoResolveTitles: true, iconvEnabled: true)->processTitle($data);
+
+        self::assertNotSame($data, $result);
+        self::assertEquals('Resolved "title"', $result->title);
+    }
+
     #[Test]
     #[TestWith([
         'contentType' => 'text/html; charset=Windows-1255',
@@ -178,9 +209,14 @@ private function respWithoutTitle(): Response
         return new Response($body, 200, ['Content-Type' => 'text/html']);
     }
 
-    private function respWithTitle(string $contentType): Response
+    private function respWithTitle(string $contentType, string|null $extraContent = null): Response
     {
-        $body = $this->createStreamWithContent('<title data-foo="bar">  Resolved &quot;title&quot; </title>');
+        $content = '<title data-foo="bar">  Resolved &quot;title&quot; </title>';
+        if ($extraContent !== null) {
+            $content .= $extraContent;
+        }
+
+        $body = $this->createStreamWithContent($content);
         return new Response($body, 200, ['Content-Type' => $contentType]);
     }