netfilter: nf_tables: implement Passive OS fingerprint module in nft_osf

Add basic module functions into nft_osf.[ch] in order to implement OSF
module in nf_tables.

Signed-off-by: Fernando Fernandez Mancera <ffmancera@riseup.net>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
This commit is contained in:
Fernando Fernandez Mancera 2018-07-25 01:32:46 +02:00 committed by Pablo Neira Ayuso
parent f932495208
commit b96af92d6e
4 changed files with 121 additions and 0 deletions

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@ -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
*

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@ -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

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@ -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

106
net/netfilter/nft_osf.c Normal file
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@ -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 = &regs->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@riseup.net>");
MODULE_ALIAS_NFT_EXPR("osf");