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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>
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4 changed files with 121 additions and 0 deletions
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@ -1463,6 +1463,13 @@ enum nft_flowtable_hook_attributes {
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};
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#define NFTA_FLOWTABLE_HOOK_MAX (__NFTA_FLOWTABLE_HOOK_MAX - 1)
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enum nft_osf_attributes {
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NFTA_OSF_UNSPEC,
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NFTA_OSF_DREG,
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__NFTA_OSF_MAX,
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};
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#define NFTA_OSF_MAX (__NFTA_OSF_MAX - 1)
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/**
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* enum nft_device_attributes - nf_tables device netlink attributes
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*
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@ -627,6 +627,13 @@ config NFT_SOCKET
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This option allows matching for the presence or absence of a
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corresponding socket and its attributes.
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config NFT_OSF
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tristate "Netfilter nf_tables passive OS fingerprint support"
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depends on NETFILTER_ADVANCED
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select NETFILTER_NETLINK_OSF
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help
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This option allows matching packets from an specific OS.
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if NF_TABLES_NETDEV
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config NF_DUP_NETDEV
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@ -110,6 +110,7 @@ obj-$(CONFIG_NFT_FIB) += nft_fib.o
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obj-$(CONFIG_NFT_FIB_INET) += nft_fib_inet.o
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obj-$(CONFIG_NFT_FIB_NETDEV) += nft_fib_netdev.o
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obj-$(CONFIG_NFT_SOCKET) += nft_socket.o
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obj-$(CONFIG_NFT_OSF) += nft_osf.o
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# nf_tables netdev
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obj-$(CONFIG_NFT_DUP_NETDEV) += nft_dup_netdev.o
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106
net/netfilter/nft_osf.c
Normal file
106
net/netfilter/nft_osf.c
Normal file
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@ -0,0 +1,106 @@
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#include <net/ip.h>
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#include <net/tcp.h>
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#include <net/netfilter/nf_tables.h>
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#include <linux/netfilter/nf_osf.h>
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#define OSF_GENRE_SIZE 32
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struct nft_osf {
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enum nft_registers dreg:8;
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};
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static const struct nla_policy nft_osf_policy[NFTA_OSF_MAX + 1] = {
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[NFTA_OSF_DREG] = { .type = NLA_U32 },
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};
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static void nft_osf_eval(const struct nft_expr *expr, struct nft_regs *regs,
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const struct nft_pktinfo *pkt)
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{
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struct nft_osf *priv = nft_expr_priv(expr);
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u32 *dest = ®s->data[priv->dreg];
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struct sk_buff *skb = pkt->skb;
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const struct tcphdr *tcp;
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struct tcphdr _tcph;
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const char *os_name;
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tcp = skb_header_pointer(skb, ip_hdrlen(skb),
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sizeof(struct tcphdr), &_tcph);
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if (!tcp) {
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regs->verdict.code = NFT_BREAK;
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return;
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}
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if (!tcp->syn) {
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regs->verdict.code = NFT_BREAK;
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return;
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}
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os_name = nf_osf_find(skb, nf_osf_fingers);
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if (!os_name)
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strncpy((char *)dest, "unknown", IFNAMSIZ);
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else
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strncpy((char *)dest, os_name, IFNAMSIZ);
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}
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static int nft_osf_init(const struct nft_ctx *ctx,
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const struct nft_expr *expr,
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const struct nlattr * const tb[])
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{
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struct nft_osf *priv = nft_expr_priv(expr);
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int err;
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priv->dreg = nft_parse_register(tb[NFTA_OSF_DREG]);
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err = nft_validate_register_store(ctx, priv->dreg, NULL,
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NFTA_DATA_VALUE, OSF_GENRE_SIZE);
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if (err < 0)
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return err;
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return 0;
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}
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static int nft_osf_dump(struct sk_buff *skb, const struct nft_expr *expr)
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{
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const struct nft_osf *priv = nft_expr_priv(expr);
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if (nft_dump_register(skb, NFTA_OSF_DREG, priv->dreg))
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goto nla_put_failure;
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return 0;
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nla_put_failure:
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return -1;
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}
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static struct nft_expr_type nft_osf_type;
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static const struct nft_expr_ops nft_osf_op = {
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.eval = nft_osf_eval,
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.size = NFT_EXPR_SIZE(sizeof(struct nft_osf)),
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.init = nft_osf_init,
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.dump = nft_osf_dump,
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.type = &nft_osf_type,
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};
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static struct nft_expr_type nft_osf_type __read_mostly = {
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.ops = &nft_osf_op,
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.name = "osf",
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.owner = THIS_MODULE,
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.policy = nft_osf_policy,
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.maxattr = NFTA_OSF_MAX,
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};
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static int __init nft_osf_module_init(void)
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{
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return nft_register_expr(&nft_osf_type);
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}
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static void __exit nft_osf_module_exit(void)
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{
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return nft_unregister_expr(&nft_osf_type);
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}
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module_init(nft_osf_module_init);
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module_exit(nft_osf_module_exit);
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MODULE_LICENSE("GPL");
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MODULE_AUTHOR("Fernando Fernandez <ffmancera@riseup.net>");
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MODULE_ALIAS_NFT_EXPR("osf");
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