From: tobias <tobias@openbsd.org>
Date: Wed, 14 Aug 2024 15:40:30 +0000 (+0000)
Subject: Extend sshbuf validation
X-Git-Url: http://artulab.com/gitweb/?a=commitdiff_plain;h=2afef00e724a2c816f2f2ac10fcb2ac7e824afbc;p=openbsd

Extend sshbuf validation

Multiple sshbuf structs can be linked through a parent/child relationship.
Make sure that a single sshbuf cannot be its own parent. If this would ever
happen, it would result in reference counting issues.

This is a cheap way of testing this with very little overhead. It does not
detect A->B->A linkages though for performance reason and the fact that it
takes a programming error for this to occur anyway.

Authored with Benny Baumann (BenBE at geshi dot org).

ok djm@
---

diff --git a/usr.bin/ssh/sshbuf.c b/usr.bin/ssh/sshbuf.c
index 97568679cb5..d0422d95fa7 100644
--- a/usr.bin/ssh/sshbuf.c
+++ b/usr.bin/ssh/sshbuf.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: sshbuf.c,v 1.21 2024/08/14 15:37:11 tobias Exp $	*/
+/*	$OpenBSD: sshbuf.c,v 1.22 2024/08/14 15:40:30 tobias Exp $	*/
 /*
  * Copyright (c) 2011 Damien Miller
  *
@@ -55,6 +55,7 @@ sshbuf_check_sanity(const struct sshbuf *buf)
 	SSHBUF_TELL("sanity");
 	if (__predict_false(buf == NULL ||
 	    (!buf->readonly && buf->d != buf->cd) ||
+	    buf->parent == buf ||
 	    buf->refcount < 1 || buf->refcount > SSHBUF_REFS_MAX ||
 	    buf->cd == NULL ||
 	    buf->max_size > SSHBUF_SIZE_MAX ||
@@ -130,7 +131,8 @@ sshbuf_set_parent(struct sshbuf *child, struct sshbuf *parent)
 	if ((r = sshbuf_check_sanity(child)) != 0 ||
 	    (r = sshbuf_check_sanity(parent)) != 0)
 		return r;
-	if (child->parent != NULL && child->parent != parent)
+	if ((child->parent != NULL && child->parent != parent) ||
+	    child == parent)
 		return SSH_ERR_INTERNAL_ERROR;
 	child->parent = parent;
 	child->parent->refcount++;