diff mbox series

[net,1/4] netfilter: remove nf_conntrack_helper sysctl and modparam toggles

Message ID 20220901071238.3044-2-fw@strlen.de (mailing list archive)
State Accepted
Commit b118509076b39cc5e616c0680312b5caaca535fe
Delegated to: Netdev Maintainers
Headers show
Series [net,1/4] netfilter: remove nf_conntrack_helper sysctl and modparam toggles | expand

Checks

Context Check Description
netdev/tree_selection success Clearly marked for net
netdev/fixes_present success Fixes tag present in non-next series
netdev/subject_prefix success Link
netdev/cover_letter success Pull request is its own cover letter
netdev/patch_count success Link
netdev/header_inline success No static functions without inline keyword in header files
netdev/build_32bit success Errors and warnings before: 4646 this patch: 4646
netdev/cc_maintainers warning 4 maintainers not CCed: shuah@kernel.org linux-kselftest@vger.kernel.org coreteam@netfilter.org kadlec@netfilter.org
netdev/build_clang success Errors and warnings before: 1115 this patch: 1115
netdev/module_param success Was 1 now: 0
netdev/verify_signedoff success Signed-off-by tag matches author and committer
netdev/check_selftest success net selftest script(s) already in Makefile
netdev/verify_fixes success No Fixes tag
netdev/build_allmodconfig_warn success Errors and warnings before: 4804 this patch: 4804
netdev/checkpatch warning CHECK: Comparison to NULL could be written "help" WARNING: line length of 88 exceeds 80 columns WARNING: line length of 99 exceeds 80 columns
netdev/kdoc success Errors and warnings before: 0 this patch: 0
netdev/source_inline success Was 0 now: 0

Commit Message

Florian Westphal Sept. 1, 2022, 7:12 a.m. UTC
From: Pablo Neira Ayuso <pablo@netfilter.org>

__nf_ct_try_assign_helper() remains in place but it now requires a
template to configure the helper.

A toggle to disable automatic helper assignment was added by:

  a9006892643a ("netfilter: nf_ct_helper: allow to disable automatic helper assignment")

in 2012 to address the issues described in "Secure use of iptables and
connection tracking helpers". Automatic conntrack helper assignment was
disabled by:

  3bb398d925ec ("netfilter: nf_ct_helper: disable automatic helper assignment")

back in 2016.

This patch removes the sysctl and modparam toggles, users now have to
rely on explicit conntrack helper configuration via ruleset.

Update tools/testing/selftests/netfilter/nft_conntrack_helper.sh to
check that auto-assignment does not happen anymore.

Acked-by: Aaron Conole <aconole@redhat.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
---
 include/net/netfilter/nf_conntrack.h          |  2 -
 include/net/netns/conntrack.h                 |  1 -
 net/netfilter/nf_conntrack_core.c             |  7 +-
 net/netfilter/nf_conntrack_helper.c           | 80 +++----------------
 net/netfilter/nf_conntrack_netlink.c          |  5 --
 net/netfilter/nf_conntrack_standalone.c       | 10 ---
 net/netfilter/nft_ct.c                        |  3 -
 .../netfilter/nft_conntrack_helper.sh         | 36 ++++++---
 8 files changed, 37 insertions(+), 107 deletions(-)

Comments

Jakub Kicinski Sept. 2, 2022, 4:07 a.m. UTC | #1
On Thu,  1 Sep 2022 09:12:35 +0200 Florian Westphal wrote:
> From: Pablo Neira Ayuso <pablo@netfilter.org>
> 
> __nf_ct_try_assign_helper() remains in place but it now requires a
> template to configure the helper.
> 
> A toggle to disable automatic helper assignment was added by:
> 
>   a9006892643a ("netfilter: nf_ct_helper: allow to disable automatic helper assignment")
> 
> in 2012 to address the issues described in "Secure use of iptables and
> connection tracking helpers". Automatic conntrack helper assignment was
> disabled by:
> 
>   3bb398d925ec ("netfilter: nf_ct_helper: disable automatic helper assignment")
> 
> back in 2016.
> 
> This patch removes the sysctl and modparam toggles, users now have to
> rely on explicit conntrack helper configuration via ruleset.
> 
> Update tools/testing/selftests/netfilter/nft_conntrack_helper.sh to
> check that auto-assignment does not happen anymore.

From the description itself it's unclear why this is a part of a net PR.
Could you elucidate?
Florian Westphal Sept. 2, 2022, 5:39 a.m. UTC | #2
Jakub Kicinski <kuba@kernel.org> wrote:
> On Thu,  1 Sep 2022 09:12:35 +0200 Florian Westphal wrote:
> > From: Pablo Neira Ayuso <pablo@netfilter.org>
> > 
> > __nf_ct_try_assign_helper() remains in place but it now requires a
> > template to configure the helper.
> > 
> > A toggle to disable automatic helper assignment was added by:
> > 
> >   a9006892643a ("netfilter: nf_ct_helper: allow to disable automatic helper assignment")
> > 
> > in 2012 to address the issues described in "Secure use of iptables and
> > connection tracking helpers". Automatic conntrack helper assignment was
> > disabled by:
> > 
> >   3bb398d925ec ("netfilter: nf_ct_helper: disable automatic helper assignment")
> > 
> > back in 2016.
> > 
> > This patch removes the sysctl and modparam toggles, users now have to
> > rely on explicit conntrack helper configuration via ruleset.
> > 
> > Update tools/testing/selftests/netfilter/nft_conntrack_helper.sh to
> > check that auto-assignment does not happen anymore.
> 
> From the description itself it's unclear why this is a part of a net PR.
> Could you elucidate?

Yes, there is improper checking in the irc dcc helper, its possible to
trigger the 'please do dynamic port forward' from outside by embedding
a 'DCC' in a PING request; if the client echos that back a expectation/
port forward gets added.

A fix for this will come in the next net PR, however, one part of the
issue is that point-blank-autassign is problematic and that helpers
should only be enabled for addresses that need it.

If you like I can resend the PR with an updated cover letter, or resend
with the dcc helper fix included as well.
Jakub Kicinski Sept. 3, 2022, 2:43 a.m. UTC | #3
On Fri, 2 Sep 2022 07:39:28 +0200 Florian Westphal wrote:
> > From the description itself it's unclear why this is a part of a net PR.
> > Could you elucidate?  
> 
> Yes, there is improper checking in the irc dcc helper, its possible to
> trigger the 'please do dynamic port forward' from outside by embedding
> a 'DCC' in a PING request; if the client echos that back a expectation/
> port forward gets added.

I see, thanks!

> A fix for this will come in the next net PR, however, one part of the
> issue is that point-blank-autassign is problematic and that helpers
> should only be enabled for addresses that need it.
> 
> If you like I can resend the PR with an updated cover letter, or resend
> with the dcc helper fix included as well.

No need, I'll fold more of your explanation into the merge commit,
should be good enough.
patchwork-bot+netdevbpf@kernel.org Sept. 3, 2022, 4:20 a.m. UTC | #4
Hello:

This series was applied to netdev/net.git (master)
by Pablo Neira Ayuso <pablo@netfilter.org>:

On Thu,  1 Sep 2022 09:12:35 +0200 you wrote:
> From: Pablo Neira Ayuso <pablo@netfilter.org>
> 
> __nf_ct_try_assign_helper() remains in place but it now requires a
> template to configure the helper.
> 
> A toggle to disable automatic helper assignment was added by:
> 
> [...]

Here is the summary with links:
  - [net,1/4] netfilter: remove nf_conntrack_helper sysctl and modparam toggles
    https://git.kernel.org/netdev/net/c/b118509076b3
  - [net,2/4] netfilter: br_netfilter: Drop dst references before setting.
    https://git.kernel.org/netdev/net/c/d047283a7034
  - [net,3/4] netfilter: nf_tables: clean up hook list when offload flags check fails
    https://git.kernel.org/netdev/net/c/77972a36ecc4
  - [net,4/4] netfilter: nf_conntrack_irc: Fix forged IP logic
    https://git.kernel.org/netdev/net/c/0efe125cfb99

You are awesome, thank you!
diff mbox series

Patch

diff --git a/include/net/netfilter/nf_conntrack.h b/include/net/netfilter/nf_conntrack.h
index a32be8aa7ed2..6a2019aaa464 100644
--- a/include/net/netfilter/nf_conntrack.h
+++ b/include/net/netfilter/nf_conntrack.h
@@ -53,8 +53,6 @@  struct nf_conntrack_net {
 	/* only used when new connection is allocated: */
 	atomic_t count;
 	unsigned int expect_count;
-	u8 sysctl_auto_assign_helper;
-	bool auto_assign_helper_warned;
 
 	/* only used from work queues, configuration plane, and so on: */
 	unsigned int users4;
diff --git a/include/net/netns/conntrack.h b/include/net/netns/conntrack.h
index c396a3862e80..e1290c159184 100644
--- a/include/net/netns/conntrack.h
+++ b/include/net/netns/conntrack.h
@@ -101,7 +101,6 @@  struct netns_ct {
 	u8			sysctl_log_invalid; /* Log invalid packets */
 	u8			sysctl_events;
 	u8			sysctl_acct;
-	u8			sysctl_auto_assign_helper;
 	u8			sysctl_tstamp;
 	u8			sysctl_checksum;
 
diff --git a/net/netfilter/nf_conntrack_core.c b/net/netfilter/nf_conntrack_core.c
index 71c2f4f95d36..1357a2729a4b 100644
--- a/net/netfilter/nf_conntrack_core.c
+++ b/net/netfilter/nf_conntrack_core.c
@@ -1782,7 +1782,7 @@  init_conntrack(struct net *net, struct nf_conn *tmpl,
 		}
 		spin_unlock_bh(&nf_conntrack_expect_lock);
 	}
-	if (!exp)
+	if (!exp && tmpl)
 		__nf_ct_try_assign_helper(ct, tmpl, GFP_ATOMIC);
 
 	/* Other CPU might have obtained a pointer to this object before it was
@@ -2068,10 +2068,6 @@  void nf_conntrack_alter_reply(struct nf_conn *ct,
 	ct->tuplehash[IP_CT_DIR_REPLY].tuple = *newreply;
 	if (ct->master || (help && !hlist_empty(&help->expectations)))
 		return;
-
-	rcu_read_lock();
-	__nf_ct_try_assign_helper(ct, NULL, GFP_ATOMIC);
-	rcu_read_unlock();
 }
 EXPORT_SYMBOL_GPL(nf_conntrack_alter_reply);
 
@@ -2797,7 +2793,6 @@  int nf_conntrack_init_net(struct net *net)
 	nf_conntrack_acct_pernet_init(net);
 	nf_conntrack_tstamp_pernet_init(net);
 	nf_conntrack_ecache_pernet_init(net);
-	nf_conntrack_helper_pernet_init(net);
 	nf_conntrack_proto_pernet_init(net);
 
 	return 0;
diff --git a/net/netfilter/nf_conntrack_helper.c b/net/netfilter/nf_conntrack_helper.c
index e96b32221444..ff737a76052e 100644
--- a/net/netfilter/nf_conntrack_helper.c
+++ b/net/netfilter/nf_conntrack_helper.c
@@ -35,11 +35,6 @@  unsigned int nf_ct_helper_hsize __read_mostly;
 EXPORT_SYMBOL_GPL(nf_ct_helper_hsize);
 static unsigned int nf_ct_helper_count __read_mostly;
 
-static bool nf_ct_auto_assign_helper __read_mostly = false;
-module_param_named(nf_conntrack_helper, nf_ct_auto_assign_helper, bool, 0644);
-MODULE_PARM_DESC(nf_conntrack_helper,
-		 "Enable automatic conntrack helper assignment (default 0)");
-
 static DEFINE_MUTEX(nf_ct_nat_helpers_mutex);
 static struct list_head nf_ct_nat_helpers __read_mostly;
 
@@ -51,24 +46,6 @@  static unsigned int helper_hash(const struct nf_conntrack_tuple *tuple)
 		(__force __u16)tuple->src.u.all) % nf_ct_helper_hsize;
 }
 
-static struct nf_conntrack_helper *
-__nf_ct_helper_find(const struct nf_conntrack_tuple *tuple)
-{
-	struct nf_conntrack_helper *helper;
-	struct nf_conntrack_tuple_mask mask = { .src.u.all = htons(0xFFFF) };
-	unsigned int h;
-
-	if (!nf_ct_helper_count)
-		return NULL;
-
-	h = helper_hash(tuple);
-	hlist_for_each_entry_rcu(helper, &nf_ct_helper_hash[h], hnode) {
-		if (nf_ct_tuple_src_mask_cmp(tuple, &helper->tuple, &mask))
-			return helper;
-	}
-	return NULL;
-}
-
 struct nf_conntrack_helper *
 __nf_conntrack_helper_find(const char *name, u16 l3num, u8 protonum)
 {
@@ -209,33 +186,11 @@  nf_ct_helper_ext_add(struct nf_conn *ct, gfp_t gfp)
 }
 EXPORT_SYMBOL_GPL(nf_ct_helper_ext_add);
 
-static struct nf_conntrack_helper *
-nf_ct_lookup_helper(struct nf_conn *ct, struct net *net)
-{
-	struct nf_conntrack_net *cnet = nf_ct_pernet(net);
-
-	if (!cnet->sysctl_auto_assign_helper) {
-		if (cnet->auto_assign_helper_warned)
-			return NULL;
-		if (!__nf_ct_helper_find(&ct->tuplehash[IP_CT_DIR_REPLY].tuple))
-			return NULL;
-		pr_info("nf_conntrack: default automatic helper assignment "
-			"has been turned off for security reasons and CT-based "
-			"firewall rule not found. Use the iptables CT target "
-			"to attach helpers instead.\n");
-		cnet->auto_assign_helper_warned = true;
-		return NULL;
-	}
-
-	return __nf_ct_helper_find(&ct->tuplehash[IP_CT_DIR_REPLY].tuple);
-}
-
 int __nf_ct_try_assign_helper(struct nf_conn *ct, struct nf_conn *tmpl,
 			      gfp_t flags)
 {
 	struct nf_conntrack_helper *helper = NULL;
 	struct nf_conn_help *help;
-	struct net *net = nf_ct_net(ct);
 
 	/* We already got a helper explicitly attached. The function
 	 * nf_conntrack_alter_reply - in case NAT is in use - asks for looking
@@ -246,23 +201,21 @@  int __nf_ct_try_assign_helper(struct nf_conn *ct, struct nf_conn *tmpl,
 	if (test_bit(IPS_HELPER_BIT, &ct->status))
 		return 0;
 
-	if (tmpl != NULL) {
-		help = nfct_help(tmpl);
-		if (help != NULL) {
-			helper = rcu_dereference(help->helper);
-			set_bit(IPS_HELPER_BIT, &ct->status);
-		}
+	if (WARN_ON_ONCE(!tmpl))
+		return 0;
+
+	help = nfct_help(tmpl);
+	if (help != NULL) {
+		helper = rcu_dereference(help->helper);
+		set_bit(IPS_HELPER_BIT, &ct->status);
 	}
 
 	help = nfct_help(ct);
 
 	if (helper == NULL) {
-		helper = nf_ct_lookup_helper(ct, net);
-		if (helper == NULL) {
-			if (help)
-				RCU_INIT_POINTER(help->helper, NULL);
-			return 0;
-		}
+		if (help)
+			RCU_INIT_POINTER(help->helper, NULL);
+		return 0;
 	}
 
 	if (help == NULL) {
@@ -545,19 +498,6 @@  void nf_nat_helper_unregister(struct nf_conntrack_nat_helper *nat)
 }
 EXPORT_SYMBOL_GPL(nf_nat_helper_unregister);
 
-void nf_ct_set_auto_assign_helper_warned(struct net *net)
-{
-	nf_ct_pernet(net)->auto_assign_helper_warned = true;
-}
-EXPORT_SYMBOL_GPL(nf_ct_set_auto_assign_helper_warned);
-
-void nf_conntrack_helper_pernet_init(struct net *net)
-{
-	struct nf_conntrack_net *cnet = nf_ct_pernet(net);
-
-	cnet->sysctl_auto_assign_helper = nf_ct_auto_assign_helper;
-}
-
 int nf_conntrack_helper_init(void)
 {
 	nf_ct_helper_hsize = 1; /* gets rounded up to use one page */
diff --git a/net/netfilter/nf_conntrack_netlink.c b/net/netfilter/nf_conntrack_netlink.c
index 04169b54f2a2..7562b215b932 100644
--- a/net/netfilter/nf_conntrack_netlink.c
+++ b/net/netfilter/nf_conntrack_netlink.c
@@ -2298,11 +2298,6 @@  ctnetlink_create_conntrack(struct net *net,
 			ct->status |= IPS_HELPER;
 			RCU_INIT_POINTER(help->helper, helper);
 		}
-	} else {
-		/* try an implicit helper assignation */
-		err = __nf_ct_try_assign_helper(ct, NULL, GFP_ATOMIC);
-		if (err < 0)
-			goto err2;
 	}
 
 	err = ctnetlink_setup_nat(ct, cda);
diff --git a/net/netfilter/nf_conntrack_standalone.c b/net/netfilter/nf_conntrack_standalone.c
index 05895878610c..4ffe84c5a82c 100644
--- a/net/netfilter/nf_conntrack_standalone.c
+++ b/net/netfilter/nf_conntrack_standalone.c
@@ -561,7 +561,6 @@  enum nf_ct_sysctl_index {
 	NF_SYSCTL_CT_LOG_INVALID,
 	NF_SYSCTL_CT_EXPECT_MAX,
 	NF_SYSCTL_CT_ACCT,
-	NF_SYSCTL_CT_HELPER,
 #ifdef CONFIG_NF_CONNTRACK_EVENTS
 	NF_SYSCTL_CT_EVENTS,
 #endif
@@ -680,14 +679,6 @@  static struct ctl_table nf_ct_sysctl_table[] = {
 		.extra1 	= SYSCTL_ZERO,
 		.extra2 	= SYSCTL_ONE,
 	},
-	[NF_SYSCTL_CT_HELPER] = {
-		.procname	= "nf_conntrack_helper",
-		.maxlen		= sizeof(u8),
-		.mode		= 0644,
-		.proc_handler	= proc_dou8vec_minmax,
-		.extra1 	= SYSCTL_ZERO,
-		.extra2 	= SYSCTL_ONE,
-	},
 #ifdef CONFIG_NF_CONNTRACK_EVENTS
 	[NF_SYSCTL_CT_EVENTS] = {
 		.procname	= "nf_conntrack_events",
@@ -1100,7 +1091,6 @@  static int nf_conntrack_standalone_init_sysctl(struct net *net)
 	table[NF_SYSCTL_CT_CHECKSUM].data = &net->ct.sysctl_checksum;
 	table[NF_SYSCTL_CT_LOG_INVALID].data = &net->ct.sysctl_log_invalid;
 	table[NF_SYSCTL_CT_ACCT].data = &net->ct.sysctl_acct;
-	table[NF_SYSCTL_CT_HELPER].data = &cnet->sysctl_auto_assign_helper;
 #ifdef CONFIG_NF_CONNTRACK_EVENTS
 	table[NF_SYSCTL_CT_EVENTS].data = &net->ct.sysctl_events;
 #endif
diff --git a/net/netfilter/nft_ct.c b/net/netfilter/nft_ct.c
index b04995c3e17f..a3f01f209a53 100644
--- a/net/netfilter/nft_ct.c
+++ b/net/netfilter/nft_ct.c
@@ -1089,9 +1089,6 @@  static int nft_ct_helper_obj_init(const struct nft_ctx *ctx,
 	if (err < 0)
 		goto err_put_helper;
 
-	/* Avoid the bogus warning, helper will be assigned after CT init */
-	nf_ct_set_auto_assign_helper_warned(ctx->net);
-
 	return 0;
 
 err_put_helper:
diff --git a/tools/testing/selftests/netfilter/nft_conntrack_helper.sh b/tools/testing/selftests/netfilter/nft_conntrack_helper.sh
index bf6b9626c7dd..faa7778d7bd1 100755
--- a/tools/testing/selftests/netfilter/nft_conntrack_helper.sh
+++ b/tools/testing/selftests/netfilter/nft_conntrack_helper.sh
@@ -102,26 +102,42 @@  check_for_helper()
 
 	ip netns exec ${netns} conntrack -L -f $family -p tcp --dport $port 2> /dev/null |grep -q 'helper=ftp'
 	if [ $? -ne 0 ] ; then
-		echo "FAIL: ${netns} did not show attached helper $message" 1>&2
-		ret=1
+		if [ $autoassign -eq 0 ] ;then
+			echo "FAIL: ${netns} did not show attached helper $message" 1>&2
+			ret=1
+		else
+			echo "PASS: ${netns} did not show attached helper $message" 1>&2
+		fi
+	else
+		if [ $autoassign -eq 0 ] ;then
+			echo "PASS: ${netns} connection on port $port has ftp helper attached" 1>&2
+		else
+			echo "FAIL: ${netns} connection on port $port has ftp helper attached" 1>&2
+			ret=1
+		fi
 	fi
 
-	echo "PASS: ${netns} connection on port $port has ftp helper attached" 1>&2
 	return 0
 }
 
 test_helper()
 {
 	local port=$1
-	local msg=$2
+	local autoassign=$2
+
+	if [ $autoassign -eq 0 ] ;then
+		msg="set via ruleset"
+	else
+		msg="auto-assign"
+	fi
 
 	sleep 3 | ip netns exec ${ns2} nc -w 2 -l -p $port > /dev/null &
 
 	sleep 1 | ip netns exec ${ns1} nc -w 2 10.0.1.2 $port > /dev/null &
 	sleep 1
 
-	check_for_helper "$ns1" "ip $msg" $port
-	check_for_helper "$ns2" "ip $msg" $port
+	check_for_helper "$ns1" "ip $msg" $port $autoassign
+	check_for_helper "$ns2" "ip $msg" $port $autoassign
 
 	wait
 
@@ -173,9 +189,9 @@  if [ $? -ne 0 ];then
 	fi
 fi
 
-test_helper 2121 "set via ruleset"
-ip netns exec ${ns1} sysctl -q 'net.netfilter.nf_conntrack_helper=1'
-ip netns exec ${ns2} sysctl -q 'net.netfilter.nf_conntrack_helper=1'
-test_helper 21 "auto-assign"
+test_helper 2121 0
+ip netns exec ${ns1} sysctl -qe 'net.netfilter.nf_conntrack_helper=1'
+ip netns exec ${ns2} sysctl -qe 'net.netfilter.nf_conntrack_helper=1'
+test_helper 21 1
 
 exit $ret