Fix buffer mismanagement in phar_dir_read()

Fixes GHSA-jqcx-ccgc-xwhv.

Author: ndossche

ext/phar/dirstream.c

@@ -91,25 +91,28 @@ static int phar_dir_seek(php_stream *stream, zend_off_t offset, int whence, zend
  */
 static ssize_t phar_dir_read(php_stream *stream, char *buf, size_t count) /* {{{ */
 {
-	size_t to_read;
 	HashTable *data = (HashTable *)stream->abstract;
 	zend_string *str_key;
 	zend_ulong unused;
 
+	if (count != sizeof(php_stream_dirent)) {
+		return -1;
+	}
+
 	if (HASH_KEY_NON_EXISTENT == zend_hash_get_current_key(data, &str_key, &unused)) {
 		return 0;
 	}
 
 	zend_hash_move_forward(data);
-	to_read = MIN(ZSTR_LEN(str_key), count);
 
-	if (to_read == 0 || count < ZSTR_LEN(str_key)) {
+	php_stream_dirent *dirent = (php_stream_dirent *) buf;
+
+	if (sizeof(dirent->d_name) <= ZSTR_LEN(str_key)) {
 		return 0;
 	}
 
-	memset(buf, 0, sizeof(php_stream_dirent));
-	memcpy(((php_stream_dirent *) buf)->d_name, ZSTR_VAL(str_key), to_read);
-	((php_stream_dirent *) buf)->d_name[to_read + 1] = '\0';
+	memset(dirent, 0, sizeof(php_stream_dirent));
+	PHP_STRLCPY(dirent->d_name, ZSTR_VAL(str_key), sizeof(dirent->d_name), ZSTR_LEN(str_key));
 
 	return sizeof(php_stream_dirent);
 }

ext/phar/tests/GHSA-jqcx-ccgc-xwhv.phpt

@@ -0,0 +1,27 @@
+--TEST--
+GHSA-jqcx-ccgc-xwhv (Buffer overflow and overread in phar_dir_read())
+--SKIPIF--
+<?php if (!extension_loaded("phar")) die("skip"); ?>
+--INI--
+phar.readonly=0
+--FILE--
+<?php
+$phar = new Phar(__DIR__. '/GHSA-jqcx-ccgc-xwhv.phar');
+$phar->startBuffering();
+$phar->addFromString(str_repeat('A', PHP_MAXPATHLEN - 1), 'This is the content of file 1.');
+$phar->addFromString(str_repeat('B', PHP_MAXPATHLEN - 1).'C', 'This is the content of file 2.');
+$phar->stopBuffering();
+
+$handle = opendir('phar://' . __DIR__ . '/GHSA-jqcx-ccgc-xwhv.phar');
+var_dump(strlen(readdir($handle)));
+// Must not be a string of length PHP_MAXPATHLEN+1
+var_dump(readdir($handle));
+closedir($handle);
+?>
+--CLEAN--
+<?php
+unlink(__DIR__. '/GHSA-jqcx-ccgc-xwhv.phar');
+?>
+--EXPECTF--
+int(%d)
+bool(false)