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<title>[56186] trunk: Filesystem API: Ensure `wp_tempnam()` does not produce file names longer than 255 characters as this is the limit on most filesystems.</title>
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<dt style="float: left; width: 6em; font-weight: bold">Revision</dt> <dd><a style="font-weight: bold" href="https://core.trac.wordpress.org/changeset/56186">56186</a><script type="application/ld+json">{"@context":"http://schema.org","@type":"EmailMessage","description":"Review this Commit","action":{"@type":"ViewAction","url":"https://core.trac.wordpress.org/changeset/56186","name":"Review Commit"}}</script></dd>
<dt style="float: left; width: 6em; font-weight: bold">Author</dt> <dd>azaozz</dd>
<dt style="float: left; width: 6em; font-weight: bold">Date</dt> <dd>2023-07-10 20:31:35 +0000 (Mon, 10 Jul 2023)</dd>
</dl>
<pre style='padding-left: 1em; margin: 2em 0; border-left: 2px solid #ccc; line-height: 1.25; font-size: 105%; font-family: sans-serif'>Filesystem API: Ensure `wp_tempnam()` does not produce file names longer than 255 characters as this is the limit on most filesystems.
Props: costdev, doems, mikeschroder, oglekler, mrinal013.
Fixes: <a href="https://core.trac.wordpress.org/ticket/35755">#35755</a>.</pre>
<h3>Modified Paths</h3>
<ul>
<li><a href="#trunksrcwpadminincludesfilephp">trunk/src/wp-admin/includes/file.php</a></li>
<li><a href="#trunktestsphpunittestsfilephp">trunk/tests/phpunit/tests/file.php</a></li>
</ul>
</div>
<div id="patch">
<h3>Diff</h3>
<a id="trunksrcwpadminincludesfilephp"></a>
<div class="modfile"><h4 style="background-color: #eee; color: inherit; margin: 1em 0; padding: 1.3em; font-size: 115%">Modified: trunk/src/wp-admin/includes/file.php</h4>
<pre class="diff"><span>
<span class="info" style="display: block; padding: 0 10px; color: #888">--- trunk/src/wp-admin/includes/file.php 2023-07-10 19:15:36 UTC (rev 56185)
+++ trunk/src/wp-admin/includes/file.php 2023-07-10 20:31:35 UTC (rev 56186)
</span><span class="lines" style="display: block; padding: 0 10px; color: #888">@@ -689,8 +689,26 @@
</span><span class="cx" style="display: block; padding: 0 10px"> // Suffix some random data to avoid filename conflicts.
</span><span class="cx" style="display: block; padding: 0 10px"> $temp_filename .= '-' . wp_generate_password( 6, false );
</span><span class="cx" style="display: block; padding: 0 10px"> $temp_filename .= '.tmp';
</span><del style="background-color: #fdd; text-decoration:none; display:block; padding: 0 10px">- $temp_filename = $dir . wp_unique_filename( $dir, $temp_filename );
</del><ins style="background-color: #dfd; text-decoration:none; display:block; padding: 0 10px">+ $temp_filename = wp_unique_filename( $dir, $temp_filename );
</ins><span class="cx" style="display: block; padding: 0 10px">
</span><ins style="background-color: #dfd; text-decoration:none; display:block; padding: 0 10px">+ /*
+ * Filesystems typically have a limit of 255 characters for a filename.
+ *
+ * If the generated unique filename exceeds this, truncate the initial
+ * filename and try again.
+ *
+ * As it's possible that the truncated filename may exist, producing a
+ * suffix of "-1" or "-10" which could exceed the limit again, truncate
+ * it to 252 instead.
+ */
+ $characters_over_limit = strlen( $temp_filename ) - 252;
+ if ( $characters_over_limit > 0 ) {
+ $filename = substr( $filename, 0, -$characters_over_limit );
+ return wp_tempnam( $filename, $dir );
+ }
+
+ $temp_filename = $dir . $temp_filename;
+
</ins><span class="cx" style="display: block; padding: 0 10px"> $fp = @fopen( $temp_filename, 'x' );
</span><span class="cx" style="display: block; padding: 0 10px">
</span><span class="cx" style="display: block; padding: 0 10px"> if ( ! $fp && is_writable( $dir ) && file_exists( $temp_filename ) ) {
</span></span></pre></div>
<a id="trunktestsphpunittestsfilephp"></a>
<div class="modfile"><h4 style="background-color: #eee; color: inherit; margin: 1em 0; padding: 1.3em; font-size: 115%">Modified: trunk/tests/phpunit/tests/file.php</h4>
<pre class="diff"><span>
<span class="info" style="display: block; padding: 0 10px; color: #888">--- trunk/tests/phpunit/tests/file.php 2023-07-10 19:15:36 UTC (rev 56185)
+++ trunk/tests/phpunit/tests/file.php 2023-07-10 20:31:35 UTC (rev 56186)
</span><span class="lines" style="display: block; padding: 0 10px; color: #888">@@ -206,6 +206,199 @@
</span><span class="cx" style="display: block; padding: 0 10px"> }
</span><span class="cx" style="display: block; padding: 0 10px">
</span><span class="cx" style="display: block; padding: 0 10px"> /**
</span><ins style="background-color: #dfd; text-decoration:none; display:block; padding: 0 10px">+ * Tests that `wp_tempnam()` limits the filename's length to 252 characters.
+ *
+ * @ticket 35755
+ *
+ * @covers ::wp_tempnam
+ *
+ * @dataProvider data_wp_tempnam_should_limit_filename_length_to_252_characters
+ */
+ public function test_wp_tempnam_should_limit_filename_length_to_252_characters( $filename ) {
+ $file = wp_tempnam( $filename );
+
+ if ( file_exists( $file ) ) {
+ self::unlink( $file );
+ }
+
+ $this->assertLessThanOrEqual( 252, strlen( basename( $file ) ) );
+ }
+
+ /**
+ * Data provider.
+ *
+ * @return array[]
+ */
+ public function data_wp_tempnam_should_limit_filename_length_to_252_characters() {
+ return array(
+ 'the limit before adding characters for uniqueness' => array( 'filename' => str_pad( '', 241, 'filename' ) ),
+ 'one more than the limit before adding characters for uniqueness' => array( 'filename' => str_pad( '', 242, 'filename' ) ),
+ '251 characters' => array( 'filename' => str_pad( '', 251, 'filename' ) ),
+ '252 characters' => array( 'filename' => str_pad( '', 252, 'filename' ) ),
+ '253 characters' => array( 'filename' => str_pad( '', 253, 'filename' ) ),
+ );
+ }
+
+ /**
+ * Tests that `wp_tempnam()` limits the filename's length to 252 characters
+ * when there is a name conflict.
+ *
+ * @ticket 35755
+ *
+ * @covers ::wp_tempnam
+ */
+ public function test_wp_tempnam_should_limit_filename_length_to_252_characters_with_name_conflict() {
+ // Create a conflict by removing the randomness of the generated password.
+ add_filter(
+ 'random_password',
+ static function() {
+ return '123456';
+ },
+ 10,
+ 0
+ );
+
+ // A filename at the limit.
+ $filename = str_pad( '', 252, 'filename' );
+
+ // Create the initial file.
+ $existing_file = wp_tempnam( $filename );
+
+ // Try creating a file with the same name.
+ $actual = wp_tempnam( basename( $existing_file ) );
+
+ self::unlink( $existing_file );
+ self::unlink( $actual );
+
+ $this->assertLessThanOrEqual( 252, strlen( basename( $actual ) ) );
+ }
+
+ /**
+ * Tests that `wp_tempnam()` limits the filename's length to 252 characters
+ * when a 'random_password' filter returns passwords longer than 6 characters.
+ *
+ * @ticket 35755
+ *
+ * @covers ::wp_tempnam
+ */
+ public function test_wp_tempnam_should_limit_filename_length_to_252_characters_when_random_password_is_filtered() {
+ // Force random passwords to 12 characters.
+ add_filter(
+ 'random_password',
+ static function() {
+ return '1a2b3c4d5e6f';
+ },
+ 10,
+ 0
+ );
+
+ // A filename at the limit.
+ $filename = str_pad( '', 252, 'filename' );
+ $actual = wp_tempnam( $filename );
+
+ self::unlink( $actual );
+
+ $this->assertLessThanOrEqual( 252, strlen( basename( $actual ) ) );
+ }
+
+ /**
+ * Tests that `wp_tempnam()` limits the filename's length to 252 characters
+ * when a 'wp_unique_filename' filter returns a filename longer than 252 characters.
+ *
+ * @ticket 35755
+ *
+ * @covers ::wp_tempnam
+ */
+ public function test_wp_tempnam_should_limit_filename_length_to_252_characters_when_wp_unique_filename_is_filtered() {
+ // Determine the number of additional characters added by `wp_tempnam()`.
+ $temp_dir = get_temp_dir();
+ $additional_chars_filename = wp_unique_filename( $temp_dir, 'filename' );
+ $additional_chars_generated = wp_tempnam( $additional_chars_filename, $temp_dir );
+ $additional_chars_difference = strlen( basename( $additional_chars_generated ) ) - strlen( $additional_chars_filename );
+
+ $filenames_over_limit = 0;
+
+ // Make the filter send the filename over the limit.
+ add_filter(
+ 'wp_unique_filename',
+ static function( $filename ) use ( &$filenames_over_limit ) {
+ if ( strlen( $filename ) === 252 ) {
+ $filename .= '1';
+ ++$filenames_over_limit;
+ }
+
+ return $filename;
+ },
+ 10,
+ 1
+ );
+
+ // A filename that will hit the limit when `wp_tempnam()` adds characters.
+ $filename = str_pad( '', 252 - $additional_chars_difference, 'filename' );
+ $actual = wp_tempnam( $filename );
+
+ self::unlink( $additional_chars_generated );
+ self::unlink( $actual );
+
+ $this->assertLessThanOrEqual( 252, strlen( basename( $actual ) ), 'The final filename was over the limit.' );
+ $this->assertSame( 1, $filenames_over_limit, 'One filename should have been over the limit.' );
+ }
+
+ /**
+ * Tests that `wp_tempnam()` limits the filename's length to 252 characters
+ * when both a 'random_password' filter and a 'wp_unique_filename' filter
+ * cause the filename to be greater than 252 characters.
+ *
+ * @ticket 35755
+ *
+ * @covers ::wp_tempnam
+ */
+ public function test_wp_tempnam_should_limit_filename_length_to_252_characters_when_random_password_and_wp_unique_filename_are_filtered() {
+ // Force random passwords to 12 characters.
+ add_filter(
+ 'random_password',
+ static function() {
+ return '1a2b3c4d5e6f';
+ },
+ 10,
+ 0
+ );
+
+ // Determine the number of additional characters added by `wp_tempnam()`.
+ $temp_dir = get_temp_dir();
+ $additional_chars_filename = wp_unique_filename( $temp_dir, 'filename' );
+ $additional_chars_generated = wp_tempnam( $additional_chars_filename, $temp_dir );
+ $additional_chars_difference = strlen( basename( $additional_chars_generated ) ) - strlen( $additional_chars_filename );
+
+ $filenames_over_limit = 0;
+
+ // Make the filter send the filename over the limit.
+ add_filter(
+ 'wp_unique_filename',
+ static function( $filename ) use ( &$filenames_over_limit ) {
+ if ( strlen( $filename ) === 252 ) {
+ $filename .= '1';
+ ++$filenames_over_limit;
+ }
+
+ return $filename;
+ },
+ 10,
+ 1
+ );
+
+ // A filename that will hit the limit when `wp_tempnam()` adds characters.
+ $filename = str_pad( '', 252 - $additional_chars_difference, 'filename' );
+ $actual = wp_tempnam( $filename );
+
+ self::unlink( $additional_chars_generated );
+ self::unlink( $actual );
+
+ $this->assertLessThanOrEqual( 252, strlen( basename( $actual ) ), 'The final filename was over the limit.' );
+ $this->assertSame( 1, $filenames_over_limit, 'One filename should have been over the limit.' );
+ }
+
+ /**
</ins><span class="cx" style="display: block; padding: 0 10px"> * @ticket 47186
</span><span class="cx" style="display: block; padding: 0 10px"> */
</span><span class="cx" style="display: block; padding: 0 10px"> public function test_file_signature_functions_as_expected() {
</span></span></pre>
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