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authorPablo Neira Ayuso <pablo@netfilter.org>2012-05-13 21:44:54 +0200
committerPablo Neira Ayuso <pablo@netfilter.org>2012-06-16 15:40:02 +0200
commit12f7a505331e6b2754684b509f2ac8f0011ce644 (patch)
treeda127aa83f0fdf0fc6be32c6386a304d5087c858 /include
parentae243bee397102c51fbf9db440eca3b077e0e702 (diff)
netfilter: add user-space connection tracking helper infrastructure
There are good reasons to supports helpers in user-space instead: * Rapid connection tracking helper development, as developing code in user-space is usually faster. * Reliability: A buggy helper does not crash the kernel. Moreover, we can monitor the helper process and restart it in case of problems. * Security: Avoid complex string matching and mangling in kernel-space running in privileged mode. Going further, we can even think about running user-space helpers as a non-root process. * Extensibility: It allows the development of very specific helpers (most likely non-standard proprietary protocols) that are very likely not to be accepted for mainline inclusion in the form of kernel-space connection tracking helpers. This patch adds the infrastructure to allow the implementation of user-space conntrack helpers by means of the new nfnetlink subsystem `nfnetlink_cthelper' and the existing queueing infrastructure (nfnetlink_queue). I had to add the new hook NF_IP6_PRI_CONNTRACK_HELPER to register ipv[4|6]_helper which results from splitting ipv[4|6]_confirm into two pieces. This change is required not to break NAT sequence adjustment and conntrack confirmation for traffic that is enqueued to our user-space conntrack helpers. Basic operation, in a few steps: 1) Register user-space helper by means of `nfct': nfct helper add ftp inet tcp [ It must be a valid existing helper supported by conntrack-tools ] 2) Add rules to enable the FTP user-space helper which is used to track traffic going to TCP port 21. For locally generated packets: iptables -I OUTPUT -t raw -p tcp --dport 21 -j CT --helper ftp For non-locally generated packets: iptables -I PREROUTING -t raw -p tcp --dport 21 -j CT --helper ftp 3) Run the test conntrackd in helper mode (see example files under doc/helper/conntrackd.conf conntrackd 4) Generate FTP traffic going, if everything is OK, then conntrackd should create expectations (you can check that with `conntrack': conntrack -E expect [NEW] 301 proto=6 src=192.168.1.136 dst=130.89.148.12 sport=0 dport=54037 mask-src=255.255.255.255 mask-dst=255.255.255.255 sport=0 dport=65535 master-src=192.168.1.136 master-dst=130.89.148.12 sport=57127 dport=21 class=0 helper=ftp [DESTROY] 301 proto=6 src=192.168.1.136 dst=130.89.148.12 sport=0 dport=54037 mask-src=255.255.255.255 mask-dst=255.255.255.255 sport=0 dport=65535 master-src=192.168.1.136 master-dst=130.89.148.12 sport=57127 dport=21 class=0 helper=ftp This confirms that our test helper is receiving packets including the conntrack information, and adding expectations in kernel-space. The user-space helper can also store its private tracking information in the conntrack structure in the kernel via the CTA_HELP_INFO. The kernel will consider this a binary blob whose layout is unknown. This information will be included in the information that is transfered to user-space via glue code that integrates nfnetlink_queue and ctnetlink. Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Diffstat (limited to 'include')
-rw-r--r--include/linux/netfilter/Kbuild1
-rw-r--r--include/linux/netfilter/nfnetlink.h3
-rw-r--r--include/linux/netfilter/nfnetlink_cthelper.h55
-rw-r--r--include/linux/netfilter_ipv4.h1
-rw-r--r--include/linux/netfilter_ipv6.h1
-rw-r--r--include/net/netfilter/nf_conntrack_helper.h11
6 files changed, 71 insertions, 1 deletions
diff --git a/include/linux/netfilter/Kbuild b/include/linux/netfilter/Kbuild
index 1697036336b..874ae8f2706 100644
--- a/include/linux/netfilter/Kbuild
+++ b/include/linux/netfilter/Kbuild
@@ -10,6 +10,7 @@ header-y += nfnetlink.h
header-y += nfnetlink_acct.h
header-y += nfnetlink_compat.h
header-y += nfnetlink_conntrack.h
+header-y += nfnetlink_cthelper.h
header-y += nfnetlink_cttimeout.h
header-y += nfnetlink_log.h
header-y += nfnetlink_queue.h
diff --git a/include/linux/netfilter/nfnetlink.h b/include/linux/netfilter/nfnetlink.h
index a1048c1587d..18341cdb244 100644
--- a/include/linux/netfilter/nfnetlink.h
+++ b/include/linux/netfilter/nfnetlink.h
@@ -50,7 +50,8 @@ struct nfgenmsg {
#define NFNL_SUBSYS_IPSET 6
#define NFNL_SUBSYS_ACCT 7
#define NFNL_SUBSYS_CTNETLINK_TIMEOUT 8
-#define NFNL_SUBSYS_COUNT 9
+#define NFNL_SUBSYS_CTHELPER 9
+#define NFNL_SUBSYS_COUNT 10
#ifdef __KERNEL__
diff --git a/include/linux/netfilter/nfnetlink_cthelper.h b/include/linux/netfilter/nfnetlink_cthelper.h
new file mode 100644
index 00000000000..33659f6fad3
--- /dev/null
+++ b/include/linux/netfilter/nfnetlink_cthelper.h
@@ -0,0 +1,55 @@
+#ifndef _NFNL_CTHELPER_H_
+#define _NFNL_CTHELPER_H_
+
+#define NFCT_HELPER_STATUS_DISABLED 0
+#define NFCT_HELPER_STATUS_ENABLED 1
+
+enum nfnl_acct_msg_types {
+ NFNL_MSG_CTHELPER_NEW,
+ NFNL_MSG_CTHELPER_GET,
+ NFNL_MSG_CTHELPER_DEL,
+ NFNL_MSG_CTHELPER_MAX
+};
+
+enum nfnl_cthelper_type {
+ NFCTH_UNSPEC,
+ NFCTH_NAME,
+ NFCTH_TUPLE,
+ NFCTH_QUEUE_NUM,
+ NFCTH_POLICY,
+ NFCTH_PRIV_DATA_LEN,
+ NFCTH_STATUS,
+ __NFCTH_MAX
+};
+#define NFCTH_MAX (__NFCTH_MAX - 1)
+
+enum nfnl_cthelper_policy_type {
+ NFCTH_POLICY_SET_UNSPEC,
+ NFCTH_POLICY_SET_NUM,
+ NFCTH_POLICY_SET,
+ NFCTH_POLICY_SET1 = NFCTH_POLICY_SET,
+ NFCTH_POLICY_SET2,
+ NFCTH_POLICY_SET3,
+ NFCTH_POLICY_SET4,
+ __NFCTH_POLICY_SET_MAX
+};
+#define NFCTH_POLICY_SET_MAX (__NFCTH_POLICY_SET_MAX - 1)
+
+enum nfnl_cthelper_pol_type {
+ NFCTH_POLICY_UNSPEC,
+ NFCTH_POLICY_NAME,
+ NFCTH_POLICY_EXPECT_MAX,
+ NFCTH_POLICY_EXPECT_TIMEOUT,
+ __NFCTH_POLICY_MAX
+};
+#define NFCTH_POLICY_MAX (__NFCTH_POLICY_MAX - 1)
+
+enum nfnl_cthelper_tuple_type {
+ NFCTH_TUPLE_UNSPEC,
+ NFCTH_TUPLE_L3PROTONUM,
+ NFCTH_TUPLE_L4PROTONUM,
+ __NFCTH_TUPLE_MAX,
+};
+#define NFCTH_TUPLE_MAX (__NFCTH_TUPLE_MAX - 1)
+
+#endif /* _NFNL_CTHELPER_H */
diff --git a/include/linux/netfilter_ipv4.h b/include/linux/netfilter_ipv4.h
index fa0946c549d..e2b12801378 100644
--- a/include/linux/netfilter_ipv4.h
+++ b/include/linux/netfilter_ipv4.h
@@ -66,6 +66,7 @@ enum nf_ip_hook_priorities {
NF_IP_PRI_SECURITY = 50,
NF_IP_PRI_NAT_SRC = 100,
NF_IP_PRI_SELINUX_LAST = 225,
+ NF_IP_PRI_CONNTRACK_HELPER = 300,
NF_IP_PRI_CONNTRACK_CONFIRM = INT_MAX,
NF_IP_PRI_LAST = INT_MAX,
};
diff --git a/include/linux/netfilter_ipv6.h b/include/linux/netfilter_ipv6.h
index 57c025127f1..7c8a513ce7a 100644
--- a/include/linux/netfilter_ipv6.h
+++ b/include/linux/netfilter_ipv6.h
@@ -71,6 +71,7 @@ enum nf_ip6_hook_priorities {
NF_IP6_PRI_SECURITY = 50,
NF_IP6_PRI_NAT_SRC = 100,
NF_IP6_PRI_SELINUX_LAST = 225,
+ NF_IP6_PRI_CONNTRACK_HELPER = 300,
NF_IP6_PRI_LAST = INT_MAX,
};
diff --git a/include/net/netfilter/nf_conntrack_helper.h b/include/net/netfilter/nf_conntrack_helper.h
index 84b24c3a383..9aad956d100 100644
--- a/include/net/netfilter/nf_conntrack_helper.h
+++ b/include/net/netfilter/nf_conntrack_helper.h
@@ -15,6 +15,11 @@
struct module;
+enum nf_ct_helper_flags {
+ NF_CT_HELPER_F_USERSPACE = (1 << 0),
+ NF_CT_HELPER_F_CONFIGURED = (1 << 1),
+};
+
#define NF_CT_HELPER_NAME_LEN 16
struct nf_conntrack_helper {
@@ -42,6 +47,9 @@ struct nf_conntrack_helper {
int (*from_nlattr)(struct nlattr *attr, struct nf_conn *ct);
int (*to_nlattr)(struct sk_buff *skb, const struct nf_conn *ct);
unsigned int expect_class_max;
+
+ unsigned int flags;
+ unsigned int queue_num; /* For user-space helpers. */
};
extern struct nf_conntrack_helper *
@@ -96,4 +104,7 @@ nf_ct_helper_expectfn_find_by_name(const char *name);
struct nf_ct_helper_expectfn *
nf_ct_helper_expectfn_find_by_symbol(const void *symbol);
+extern struct hlist_head *nf_ct_helper_hash;
+extern unsigned int nf_ct_helper_hsize;
+
#endif /*_NF_CONNTRACK_HELPER_H*/