On 06/27/2018 07:19 PM, Pablo Neira Ayuso wrote:
On Wed, Jun 27, 2018 at 07:11:39PM +0200, Fernando Fernandez Mancera wrote:
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/net/netfilter/nft_osf.h | 15 +++++
net/netfilter/Kconfig | 7 +++
net/netfilter/Makefile | 1 +
net/netfilter/nft_osf.c | 104 ++++++++++++++++++++++++++++++++
4 files changed, 127 insertions(+)
create mode 100644 include/net/netfilter/nft_osf.h
create mode 100644 net/netfilter/nft_osf.c
diff --git a/include/net/netfilter/nft_osf.h b/include/net/netfilter/nft_osf.h
new file mode 100644
index 000000000000..af6c8550f564
--- /dev/null
+++ b/include/net/netfilter/nft_osf.h
@@ -0,0 +1,15 @@
+#ifndef _NFT_OSF_H
+#define _NFT_OSF_H
+
+enum nft_osf_attributes {
+ NFTA_OSF_UNSPEC,
+ NFTA_OSF_GENRE,
+ NFTA_OSF_FLAGS,
+ NFTA_OSF_LOGLEVEL,
+ NFTA_OSF_TTL,
+ __NFTA_OSF_MAX,
+};
+
+#define NFTA_OSF_MAX (__NFTA_OSF_MAX - 1)
+
+#endif /* _NFT_OSF_H */
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.
+
I am not completly sure if NFT_OSF depends on NETFILTER_INET too.
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..008e3484f3da
--- /dev/null
+++ b/net/netfilter/nft_osf.c
@@ -0,0 +1,104 @@
+#include <net/netfilter/nf_tables.h>
+#include <linux/tcp.h>
+#include <net/netfilter/nft_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;
OK, so your follow up step is to support this, right?
Yes, my next step is to add _ADD and _REMOVE commands to
net/netfilter/nf_tables_api.c in order to use the nf_tables interface to
add osf signatures in nft.
+}
+
+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_CONTINUE;
NFT_CONTINUE is implicit, so not needed.
+ else
+ regs->verdict.code = NFT_BREAK;
So you can simplify this to:
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);
+ priv->flags = ntohl(nla_get_be32(tb[NFTA_OSF_FLAGS]));
I guess you have to check for invalid flags here, eg.
if (priv->flags & ~MASK_WITH_SUPPORT_FLAGS)
return -EOPNOTSUPP;
+ priv->loglevel = ntohl(nla_get_be32(tb[NFTA_OSF_LOGLEVEL]));
Probably same thing here?
+ 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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