netdev - [PATCH 2/4] netfilter: nf_ct_helper: disable automatic helper re-assignment of different type

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Tue, 19 Jun 2012 05:16:27 +0200
From:	pablo@...filter.org
To:	netfilter-devel@...r.kernel.org
Cc:	davem@...emloft.net, netdev@...r.kernel.org
Subject: [PATCH 2/4] netfilter: nf_ct_helper: disable automatic helper re-assignment of different type

From: Pablo Neira Ayuso <pablo@...filter.org>

This patch modifies __nf_ct_try_assign_helper in a way that invalidates support
for the following scenario:

1) attach the helper A for first time when the conntrack is created
2) attach new (different) helper B due to changes the reply tuple caused by NAT

eg. port redirection from TCP/21 to TCP/5060 with both FTP and SIP helpers
loaded, which seems to be a quite unorthodox scenario.

I can provide a more elaborated patch to support this scenario but explicit
helper attachment provides a better solution for this since now the use can
attach the helpers consistently, without relying on the automatic helper
lookup magic.

This patch fixes a possible out of bound zeroing of the conntrack helper
extension if the helper B uses more memory for its private data than
helper A.

Signed-off-by: Pablo Neira Ayuso <pablo@...filter.org>
---
 net/netfilter/nf_conntrack_helper.c |    8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/net/netfilter/nf_conntrack_helper.c b/net/netfilter/nf_conntrack_helper.c
index 2918ec2..c4bc637 100644
--- a/net/netfilter/nf_conntrack_helper.c
+++ b/net/netfilter/nf_conntrack_helper.c
@@ -229,7 +229,13 @@ int __nf_ct_try_assign_helper(struct nf_conn *ct, struct nf_conn *tmpl,
 			goto out;
 		}
 	} else {
-		memset(help->data, 0, helper->data_len);
+		/* We only allow helper re-assignment of the same sort since
+		 * we cannot reallocate the helper extension area.
+		 */
+		if (help->helper != helper) {
+			RCU_INIT_POINTER(help->helper, NULL);
+			goto out;
+		}
 	}

 	rcu_assign_pointer(help->helper, helper);
-- 
1.7.10

--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html