Fix reading large pax extended records

512 bytes isn't enough if you want to store rather large but still
useful long file names or symbolic links destinations.  The best way to
size the buffer to read those records is based upon the largest paths
pax(1) can handle, and that is PAXPATHLEN.

Reported by caspar@, input and ok millert@

1 files changed, 6 insertions, 5 deletions

diff --git a/bin/pax/tar.c b/bin/pax/tar.c
index 212961f8f44..01f4491ac6b 100644
--- a/bin/pax/tar.c
+++ b/bin/pax/tar.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: tar.c,v 1.83 2024/04/16 20:51:11 jca Exp $	*/
+/*	$OpenBSD: tar.c,v 1.84 2024/04/16 22:58:10 jca Exp $	*/
 /*	$NetBSD: tar.c,v 1.5 1995/03/21 09:07:49 cgd Exp $	*/
 
 /*-
@@ -62,9 +62,6 @@ struct xheader_record {
 /* shortest possible extended record: "5 a=\n" */
 #define MINXHDRSZ	5
 
-/* longest record we'll accept */
-#define MAXXHDRSZ	BLKMULT
-
 /*
  * Routines for reading, writing and header identify of various versions of tar
  */
@@ -1588,7 +1585,11 @@ rd_size(off_t *size, const char *keyword, char *p)
 static int
 rd_xheader(ARCHD *arcn, int global, off_t size)
 {
-	char buf[MAXXHDRSZ];
+	/*
+	 * The pax format supposedly supports arbitrarily sized extended
+	 * record headers, this implementation doesn't.
+	 */
+	char buf[sizeof("30xx linkpath=") - 1 + PAXPATHLEN + sizeof("\n")];
 	long len;
 	char *delim, *keyword;
 	char *nextp, *p, *end;