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Date: Sun, 5 Aug 2018 23:21:26 +0200
From: Pablo Neira Ayuso <pablo@...filter.org>
To: netfilter-devel@...r.kernel.org
Cc: davem@...emloft.net, netdev@...r.kernel.org
Subject: [PATCH 06/21] netfilter: nf_tables: implement Passive OS fingerprint module in nft_osf
From: Fernando Fernandez Mancera <ffmancera@...eup.net>
Add basic module functions into nft_osf.[ch] in order to implement OSF
module in nf_tables.
Signed-off-by: Fernando Fernandez Mancera <ffmancera@...eup.net>
Signed-off-by: Pablo Neira Ayuso <pablo@...filter.org>
---
include/uapi/linux/netfilter/nf_tables.h | 7 ++
net/netfilter/Kconfig | 7 ++
net/netfilter/Makefile | 1 +
net/netfilter/nft_osf.c | 106 +++++++++++++++++++++++++++++++
4 files changed, 121 insertions(+)
create mode 100644 net/netfilter/nft_osf.c
diff --git a/include/uapi/linux/netfilter/nf_tables.h b/include/uapi/linux/netfilter/nf_tables.h
index f466860bcf75..382c32d630e9 100644
--- a/include/uapi/linux/netfilter/nf_tables.h
+++ b/include/uapi/linux/netfilter/nf_tables.h
@@ -1463,6 +1463,13 @@ enum nft_flowtable_hook_attributes {
};
#define NFTA_FLOWTABLE_HOOK_MAX (__NFTA_FLOWTABLE_HOOK_MAX - 1)
+enum nft_osf_attributes {
+ NFTA_OSF_UNSPEC,
+ NFTA_OSF_DREG,
+ __NFTA_OSF_MAX,
+};
+#define NFTA_OSF_MAX (__NFTA_OSF_MAX - 1)
+
/**
* enum nft_device_attributes - nf_tables device netlink attributes
*
diff --git a/net/netfilter/Kconfig b/net/netfilter/Kconfig
index 85333431e524..16fdfb75efb5 100644
--- a/net/netfilter/Kconfig
+++ b/net/netfilter/Kconfig
@@ -627,6 +627,13 @@ config NFT_SOCKET
This option allows matching for the presence or absence of a
corresponding socket and its attributes.
+config NFT_OSF
+ tristate "Netfilter nf_tables passive OS fingerprint support"
+ depends on NETFILTER_ADVANCED
+ select NETFILTER_NETLINK_OSF
+ help
+ This option allows matching packets from an specific OS.
+
if NF_TABLES_NETDEV
config NF_DUP_NETDEV
diff --git a/net/netfilter/Makefile b/net/netfilter/Makefile
index e684f9b8a9c3..5cbbf6978b55 100644
--- a/net/netfilter/Makefile
+++ b/net/netfilter/Makefile
@@ -110,6 +110,7 @@ obj-$(CONFIG_NFT_FIB) += nft_fib.o
obj-$(CONFIG_NFT_FIB_INET) += nft_fib_inet.o
obj-$(CONFIG_NFT_FIB_NETDEV) += nft_fib_netdev.o
obj-$(CONFIG_NFT_SOCKET) += nft_socket.o
+obj-$(CONFIG_NFT_OSF) += nft_osf.o
# nf_tables netdev
obj-$(CONFIG_NFT_DUP_NETDEV) += nft_dup_netdev.o
diff --git a/net/netfilter/nft_osf.c b/net/netfilter/nft_osf.c
new file mode 100644
index 000000000000..bdacc4cffba4
--- /dev/null
+++ b/net/netfilter/nft_osf.c
@@ -0,0 +1,106 @@
+#include <net/ip.h>
+#include <net/tcp.h>
+
+#include <net/netfilter/nf_tables.h>
+#include <linux/netfilter/nf_osf.h>
+
+#define OSF_GENRE_SIZE 32
+
+struct nft_osf {
+ enum nft_registers dreg:8;
+};
+
+static const struct nla_policy nft_osf_policy[NFTA_OSF_MAX + 1] = {
+ [NFTA_OSF_DREG] = { .type = NLA_U32 },
+};
+
+static void nft_osf_eval(const struct nft_expr *expr, struct nft_regs *regs,
+ const struct nft_pktinfo *pkt)
+{
+ struct nft_osf *priv = nft_expr_priv(expr);
+ u32 *dest = ®s->data[priv->dreg];
+ struct sk_buff *skb = pkt->skb;
+ const struct tcphdr *tcp;
+ struct tcphdr _tcph;
+ const char *os_name;
+
+ tcp = skb_header_pointer(skb, ip_hdrlen(skb),
+ sizeof(struct tcphdr), &_tcph);
+ if (!tcp) {
+ regs->verdict.code = NFT_BREAK;
+ return;
+ }
+ if (!tcp->syn) {
+ regs->verdict.code = NFT_BREAK;
+ return;
+ }
+
+ os_name = nf_osf_find(skb, nf_osf_fingers);
+ if (!os_name)
+ strncpy((char *)dest, "unknown", IFNAMSIZ);
+ else
+ strncpy((char *)dest, os_name, IFNAMSIZ);
+}
+
+static int nft_osf_init(const struct nft_ctx *ctx,
+ const struct nft_expr *expr,
+ const struct nlattr * const tb[])
+{
+ struct nft_osf *priv = nft_expr_priv(expr);
+ int err;
+
+ priv->dreg = nft_parse_register(tb[NFTA_OSF_DREG]);
+ err = nft_validate_register_store(ctx, priv->dreg, NULL,
+ NFTA_DATA_VALUE, OSF_GENRE_SIZE);
+ if (err < 0)
+ return err;
+
+ return 0;
+}
+
+static int nft_osf_dump(struct sk_buff *skb, const struct nft_expr *expr)
+{
+ const struct nft_osf *priv = nft_expr_priv(expr);
+
+ if (nft_dump_register(skb, NFTA_OSF_DREG, priv->dreg))
+ goto nla_put_failure;
+
+ return 0;
+
+nla_put_failure:
+ return -1;
+}
+
+static struct nft_expr_type nft_osf_type;
+static const struct nft_expr_ops nft_osf_op = {
+ .eval = nft_osf_eval,
+ .size = NFT_EXPR_SIZE(sizeof(struct nft_osf)),
+ .init = nft_osf_init,
+ .dump = nft_osf_dump,
+ .type = &nft_osf_type,
+};
+
+static struct nft_expr_type nft_osf_type __read_mostly = {
+ .ops = &nft_osf_op,
+ .name = "osf",
+ .owner = THIS_MODULE,
+ .policy = nft_osf_policy,
+ .maxattr = NFTA_OSF_MAX,
+};
+
+static int __init nft_osf_module_init(void)
+{
+ return nft_register_expr(&nft_osf_type);
+}
+
+static void __exit nft_osf_module_exit(void)
+{
+ return nft_unregister_expr(&nft_osf_type);
+}
+
+module_init(nft_osf_module_init);
+module_exit(nft_osf_module_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Fernando Fernandez <ffmancera@...eup.net>");
+MODULE_ALIAS_NFT_EXPR("osf");
--
2.11.0
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