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Re: [libvirt] [PATCH] proxy: Fix use of uninitalized memory



"Rasputin" <rasputin email ru> wrote:

> On short read, members of packet header are checked before actually read.
> If uninitialized values can pass the test, they can be set to arbitrary
> values while reading remaining portion of a packet.
>
> Buffer overflow is possible. libvirt_proxy is suid-root.
>
> diff -urp libvirt-0.5.1/proxy/libvirt_proxy.c libvirt-dev/proxy/libvirt_proxy.c
> --- libvirt-0.5.1/proxy/libvirt_proxy.c 2008-11-20 08:58:43.000000000 +0100
> +++ libvirt-dev/proxy/libvirt_proxy.c   2009-01-25 12:51:33.000000000 +0100
> @@ -385,7 +385,8 @@ retry:
>         fprintf(stderr, "read %d bytes from client %d on socket %d\n",
>                 ret, nr, pollInfos[nr].fd);
>
> -    if ((req->version != PROXY_PROTO_VERSION) ||
> +    if ((ret != sizeof(virProxyPacket)) ||
> +        (req->version != PROXY_PROTO_VERSION) ||
>         (req->len < sizeof(virProxyPacket)) ||
>         (req->len > sizeof(virProxyFullPacket)))
>         goto comm_error;

Thanks again.
Here's what I expect to commit.
If you would like different attribution, let me know.

>From 0abc169e868d7b7b5d1edd75aec0e021b1e67c53 Mon Sep 17 00:00:00 2001
From: Jim Meyering <meyering redhat com>
Date: Wed, 28 Jan 2009 14:27:11 +0100
Subject: [PATCH] libvirt_proxy: avoid potential buffer overflow

* proxy/libvirt_proxy.c (proxyReadClientSocket): Ensure that
we've read an entire virProxyPacket before dereferencing "req".
Analysis and patch by "Rasputin" <rasputin email ru>.  Details in
<http://thread.gmane.org/gmane.comp.emulators.libvirt/11459>.
---
 proxy/libvirt_proxy.c |    5 +++--
 1 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/proxy/libvirt_proxy.c b/proxy/libvirt_proxy.c
index f3d9ede..863dc32 100644
--- a/proxy/libvirt_proxy.c
+++ b/proxy/libvirt_proxy.c
@@ -2,7 +2,7 @@
  * proxy_svr.c: root suid proxy server for Xen access to APIs with no
  *              side effects from unauthenticated clients.
  *
- * Copyright (C) 2006, 2007, 2008 Red Hat, Inc.
+ * Copyright (C) 2006, 2007, 2008, 2009 Red Hat, Inc.
  *
  * See COPYING.LIB for the License of this software
  *
@@ -382,7 +382,8 @@ retry:
         fprintf(stderr, "read %d bytes from client %d on socket %d\n",
                 ret, nr, pollInfos[nr].fd);

-    if ((req->version != PROXY_PROTO_VERSION) ||
+    if ((ret != sizeof(virProxyPacket)) ||
+        (req->version != PROXY_PROTO_VERSION) ||
         (req->len < sizeof(virProxyPacket)) ||
         (req->len > sizeof(virProxyFullPacket)))
         goto comm_error;
--
1.6.1.1.374.g0d9d7


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