From 4ef300ff5ee309394e78bd92d6cb9cd47cf4195a Mon Sep 17 00:00:00 2001
From: "Christoph M. Becker" <cmbecker69@gmx.de>
Date: Mon, 25 Jul 2022 15:58:59 +0200
Subject: [PATCH] Fix #81726: phar wrapper: DOS when using quine gzip file

The phar wrapper needs to uncompress the file; the uncompressed file
might be compressed, so the wrapper implementation loops. This raises
potential DOS issues regarding too deep or even infinite recursion (the
latter are called compressed file quines[1]). We avoid that by
introducing a recursion limit; we choose the somewhat arbitrary limit
`3`.

This issue has been reported by real_as3617 and gPayl0ad.

[1] <https://honno.dev/gzip-quine/>
---
 NEWS                         |   2 ++
 ext/phar/phar.c              |  16 +++++++++++-----
 ext/phar/tests/bug81726.gz   | Bin 0 -> 204 bytes
 ext/phar/tests/bug81726.phpt |  14 ++++++++++++++
 4 files changed, 27 insertions(+), 5 deletions(-)
 create mode 100644 ext/phar/tests/bug81726.gz
 create mode 100644 ext/phar/tests/bug81726.phpt

diff --git a/NEWS b/NEWS
index 94c8fea4ef7..415628f2dcb 100644
--- a/NEWS
+++ b/NEWS
@@ -3,6 +3,8 @@ PHP                                                                        NEWS
 ?? ??? ????, PHP 8.1.11
 
 - Core:
+  . Fixed bug #81726: phar wrapper: DOS when using quine gzip file.
+    (CVE-2022-31628). (cmb)
   . Fixed bug GH-9323 (Crash in ZEND_RETURN/GC/zend_call_function)
     (Tim Starling)
   . Fixed bug GH-9361 (Segmentation fault on script exit #9379). (cmb,
diff --git a/ext/phar/phar.c b/ext/phar/phar.c
index bc08e4edde0..1d5815c6d55 100644
--- a/ext/phar/phar.c
+++ b/ext/phar/phar.c
@@ -1626,7 +1626,8 @@ static int phar_open_from_fp(php_stream* fp, char *fname, size_t fname_len, char
 	const char zip_magic[] = "PK\x03\x04";
 	const char gz_magic[] = "\x1f\x8b\x08";
 	const char bz_magic[] = "BZh";
-	char *pos, test = '\0';
+	char *pos;
+	int recursion_count = 3; // arbitrary limit to avoid too deep or even infinite recursion
 	const int window_size = 1024;
 	char buffer[1024 + sizeof(token)]; /* a 1024 byte window + the size of the halt_compiler token (moving window) */
 	const zend_long readsize = sizeof(buffer) - sizeof(token);
@@ -1654,8 +1655,7 @@ static int phar_open_from_fp(php_stream* fp, char *fname, size_t fname_len, char
 			MAPPHAR_ALLOC_FAIL("internal corruption of phar \"%s\" (truncated entry)")
 		}
 
-		if (!test) {
-			test = '\1';
+		if (recursion_count) {
 			pos = buffer+tokenlen;
 			if (!memcmp(pos, gz_magic, 3)) {
 				char err = 0;
@@ -1715,7 +1715,10 @@ static int phar_open_from_fp(php_stream* fp, char *fname, size_t fname_len, char
 				compression = PHAR_FILE_COMPRESSED_GZ;
 
 				/* now, start over */
-				test = '\0';
+				if (!--recursion_count) {
+					MAPPHAR_ALLOC_FAIL("unable to decompress gzipped phar archive \"%s\"");
+					break;
+				}
 				continue;
 			} else if (!memcmp(pos, bz_magic, 3)) {
 				php_stream_filter *filter;
@@ -1753,7 +1756,10 @@ static int phar_open_from_fp(php_stream* fp, char *fname, size_t fname_len, char
 				compression = PHAR_FILE_COMPRESSED_BZ2;
 
 				/* now, start over */
-				test = '\0';
+				if (!--recursion_count) {
+					MAPPHAR_ALLOC_FAIL("unable to decompress bzipped phar archive \"%s\"");
+					break;
+				}
 				continue;
 			}
 
diff --git a/ext/phar/tests/bug81726.gz b/ext/phar/tests/bug81726.gz
new file mode 100644
index 0000000000000000000000000000000000000000..67b41ba3b6567fb242296fbb5db1504dd562c285
GIT binary patch
literal 204
zcmb2|=HOref&Yc2nR%&t=~WC25)9A(%i|Dt5_1=0XJBRc^&i0ka~VV!USk*QP&~o_
nktKo!bjW{@YyLCvGJN{)1lEBn)?BbahT(tZ|CMKe>QFcU?_ozX

literal 0
HcmV?d00001

diff --git a/ext/phar/tests/bug81726.phpt b/ext/phar/tests/bug81726.phpt
new file mode 100644
index 00000000000..11a148c28ea
--- /dev/null
+++ b/ext/phar/tests/bug81726.phpt
@@ -0,0 +1,14 @@
+--TEST--
+Bug #81726 (phar wrapper: DOS when using quine gzip file)
+--SKIPIF--
+<?php
+if (!extension_loaded("phar")) die("skip phar extension not available");
+if (!extension_loaded("zlib")) die("skip zlib extension not available");
+?>
+--FILE--
+<?php
+var_dump(fopen("phar://" . __DIR__ . "/bug81726.gz", "r"));
+?>
+--EXPECTF--
+Warning: fopen(phar://%s): failed to open stream: unable to decompress gzipped phar archive "%s" in %s on line %d
+bool(false)