Fix #81211: Symlinks are followed when creating PHAR archive

It is insufficient to check whether the `base` is contained in `fname`;
we also need to ensure that `fname` is properly separated.  And of
course, `fname` has to start with `base`.

ext/phar/phar_object.c

@@ -1405,6 +1405,7 @@ static int phar_build(zend_object_iterator *iter, void *puser) /* {{{ */
 	zend_class_entry *ce = p_obj->c;
 	phar_archive_object *phar_obj = p_obj->p;
 	php_stream_statbuf ssb;
+	char ch;
 
 	value = iter->funcs->get_current_data(iter);
 
@@ -1528,7 +1529,7 @@ phar_spl_fileinfo:
 		base = temp;
 		base_len = strlen(base);
 
-		if (strstr(fname, base)) {
+		if (fname_len >= base_len && strncmp(fname, base, base_len) == 0 && ((ch = fname[base_len - IS_SLASH(base[base_len - 1])]) == '\0' || IS_SLASH(ch))) {
 			str_key_len = fname_len - base_len;
 
 			if (str_key_len <= 0) {

ext/phar/tests/bug81211.phpt

@@ -0,0 +1,45 @@
+--TEST--
+Bug #81211 (Symlinks are followed when creating PHAR archive)
+--SKIPIF--
+<?php
+if (!extension_loaded('phar')) die('skip phar extension is not available');
+if (PHP_OS_FAMILY === 'Windows') {
+    if (false === include __DIR__ . '/../../standard/tests/file/windows_links/common.inc') {
+        die('skip windows_links/common.inc is not available');
+    }
+    skipIfSeCreateSymbolicLinkPrivilegeIsDisabled(__FILE__);
+}
+?>
+--FILE--
+<?php
+mkdir(__DIR__ . '/bug81211');
+mkdir(__DIR__ . '/bug81211/foobar');
+mkdir(__DIR__ . '/bug81211/foo');
+
+file_put_contents(__DIR__ . '/bug81211/foobar/file', 'this file should NOT be included in the archive!');
+symlink(__DIR__ . '/bug81211/foobar/file', __DIR__ . '/bug81211/foo/symlink');
+
+$archive = new PharData(__DIR__ . '/bug81211/archive.tar');
+try {
+    $archive->buildFromDirectory(__DIR__ . '/bug81211/foo');
+} catch (UnexpectedValueException $ex) {
+    echo $ex->getMessage(), PHP_EOL;
+}
+try {
+    $archive->buildFromIterator(new RecursiveDirectoryIterator(__DIR__ . '/bug81211/foo', FilesystemIterator::SKIP_DOTS), __DIR__ . '/bug81211/foo');
+} catch (UnexpectedValueException $ex) {
+    echo $ex->getMessage(), PHP_EOL;
+}
+?>
+--CLEAN--
+<?php
+@unlink(__DIR__ . '/bug81211/archive.tar');
+@unlink(__DIR__ . '/bug81211/foo/symlink');
+@unlink(__DIR__ . '/bug81211/foobar/file');
+@rmdir(__DIR__ . '/bug81211/foo');
+@rmdir(__DIR__ . '/bug81211/foobar');
+@rmdir(__DIR__ . '/bug81211');
+?>
+--EXPECTF--
+Iterator RecursiveIteratorIterator returned a path "%s%ebug81211\foobar\file" that is not in the base directory "%s%ebug81211\foo"
+Iterator RecursiveDirectoryIterator returned a path "%s%ebug81211\foobar\file" that is not in the base directory "%s%ebug81211\foo"

ext/standard/tests/file/windows_links/common.inc

@@ -20,4 +20,11 @@ function get_mountvol() {
 	return "$sysroot\\System32\\mountvol.exe";
 }
 
-?>
+function skipIfSeCreateSymbolicLinkPrivilegeIsDisabled(string $filename) {
+	$ln = "$filename.lnk";
+	$ret = exec("mklink $ln " . __FILE__ .' 2>&1', $out);
+	@unlink($ln);
+	if (strpos($ret, 'privilege') !== false) {
+		die('skip SeCreateSymbolicLinkPrivilege not enabled');
+	}
+}