Add basic module functions into nft_osf.[ch] in order to start the
implementation of OSF module in nf_tables.
Signed-off-by: Fernando Fernandez Mancera <ffmancera@xxxxxxxxxx>
---
include/uapi/linux/netfilter/nf_osf.h | 7 ++
include/uapi/linux/netfilter/xt_osf.h | 6 +-
net/netfilter/Kconfig | 7 ++
net/netfilter/Makefile | 1 +
net/netfilter/nft_osf.c | 108 ++++++++++++++++++++++++++
5 files changed, 128 insertions(+), 1 deletion(-)
create mode 100644 net/netfilter/nft_osf.c
diff --git a/include/uapi/linux/netfilter/nf_osf.h b/include/uapi/linux/netfilter/nf_osf.h
index 8f2f2f403183..79882b2f7f8e 100644
--- a/include/uapi/linux/netfilter/nf_osf.h
+++ b/include/uapi/linux/netfilter/nf_osf.h
@@ -16,9 +16,16 @@
#define NF_OSF_TTL_TRUE 0 /* True ip and fingerprint TTL comparison */
+/* Check if ip TTL is less than fingerprint one */
+#define NF_OSF_TTL_LESS 1
+
/* Do not compare ip and fingerprint TTL at all */
#define NF_OSF_TTL_NOCHECK 2
+#define NF_OSF_FLAGMASK (NF_OSF_GENRE | \
+ NF_OSF_TTL | \
+ NF_OSF_LOG | \
+ NF_OSF_INVERT)
/* Wildcard MSS (kind of).
* It is used to implement a state machine for the different wildcard values
* of the MSS and window sizes.
diff --git a/include/uapi/linux/netfilter/xt_osf.h b/include/uapi/linux/netfilter/xt_osf.h
index 72956eceeb09..2f5d4e6d0434 100644
--- a/include/uapi/linux/netfilter/xt_osf.h
+++ b/include/uapi/linux/netfilter/xt_osf.h
@@ -37,8 +37,12 @@
#define XT_OSF_TTL_TRUE NF_OSF_TTL_TRUE
#define XT_OSF_TTL_NOCHECK NF_OSF_TTL_NOCHECK
+#define XT_OSF_TTL_LESS NF_OSF_TTL_LESS
-#define XT_OSF_TTL_LESS 1 /* Check if ip TTL is less than fingerprint one */
+#define XT_OSF_FLAGMASK (XT_OSF_GENRE | \
+ XT_OSF_TTL | \
+ XT_OSF_LOG | \
+ XT_OSF_INVERT)
#define xt_osf_wc nf_osf_wc
#define xt_osf_opt nf_osf_opt
diff --git a/net/netfilter/Kconfig b/net/netfilter/Kconfig
index dbd7d1fad277..e630aac8a081 100644
--- a/net/netfilter/Kconfig
+++ b/net/netfilter/Kconfig
@@ -631,6 +631,13 @@ 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 fingerprinting support"
+ depends on NETFILTER_ADVANCED && NETFILTER_NETLINK
+ select NF_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 44449389e527..d15bd858ecef 100644
--- a/net/netfilter/Makefile
+++ b/net/netfilter/Makefile
@@ -104,6 +104,7 @@ obj-$(CONFIG_NFT_FIB_INET) += nft_fib_inet.o
obj-$(CONFIG_NFT_FIB_NETDEV) += nft_fib_netdev.o
obj-$(CONFIG_NF_OSF) += nf_osf.o
obj-$(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..30c503f2bf53
--- /dev/null
+++ b/net/netfilter/nft_osf.c
@@ -0,0 +1,108 @@
+#include <net/netfilter/nf_tables.h>
+#include <linux/netfilter/nf_osf.h>
+
+#define OSF_GENRE_SIZE 32
+
+struct nft_osf {
+ char genre[OSF_GENRE_SIZE];
+ __u32 flags;
+ __u32 loglevel;
+ __u32 ttl;
+ __u32 len;
+};
+
+/* placeholder function WIP */
+static inline bool match_packet(struct nft_osf *priv, struct sk_buff *skb)
+{
+ return 1;
+}
+
+static const struct nla_policy nft_osf_policy[NFTA_OSF_MAX + 1] = {
+ [NFTA_OSF_GENRE] = { .type = NLA_STRING, .len = OSF_GENRE_SIZE },
+ [NFTA_OSF_FLAGS] = { .type = NLA_U32 },
+ [NFTA_OSF_LOGLEVEL] = { .type = NLA_U32 },
+ [NFTA_OSF_TTL] = { .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);
+ struct sk_buff *skb = pkt->skb;
+
+ if (!match_packet(priv, skb))
+ regs->verdict.code = NFT_BREAK;
+}
+
+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);
+
+ if (tb[NFTA_OSF_GENRE] == NULL)
+ return -EINVAL;
+ nla_strlcpy(priv->genre, tb[NFTA_OSF_GENRE], OSF_GENRE_SIZE);
+ if (ntohl(nla_get_be32(tb[NFTA_OSF_FLAGS])) & ~NF_OSF_FLAGMASK)
+ return -EINVAL;
+ priv->flags = ntohl(nla_get_be32(tb[NFTA_OSF_FLAGS]));
+ if (ntohl(nla_get_be32(tb[NFTA_OSF_LOGLEVEL])) >=
+ NF_OSF_LOGLEVEL_ALL_KNOWN)
+ return -EINVAL;
+ priv->loglevel = ntohl(nla_get_be32(tb[NFTA_OSF_LOGLEVEL]));
+ if (ntohl(nla_get_be32(tb[NFTA_OSF_TTL])) >= NF_OSF_TTL_NOCHECK)
+ return -EINVAL;
+ priv->ttl = ntohl(nla_get_be32(tb[NFTA_OSF_TTL]));
+ priv->len = strlen(priv->genre);
+ 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 (nla_put_string(skb, NFTA_OSF_GENRE, priv->genre) ||
+ nla_put_be32(skb, NFTA_OSF_FLAGS, htonl(priv->flags)) ||
+ nla_put_be32(skb, NFTA_OSF_LOGLEVEL, htonl(priv->loglevel)) ||
+ nla_put_be32(skb, NFTA_OSF_TTL, htonl(priv->ttl)))
+ 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@xxxxxxxxxx>");
+MODULE_ALIAS_NFT_EXPR("osf");
--
2.18.0
--
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