1 files changed, 436 insertions, 0 deletions

diff --git a/net/netfilter/nfnetlink_osf.c b/net/netfilter/nfnetlink_osf.c
new file mode 100644
index 000000000000..00db27dfd2ff
--- /dev/null
+++ b/net/netfilter/nfnetlink_osf.c
@@ -0,0 +1,436 @@
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+#include <linux/module.h>
+#include <linux/kernel.h>
+
+#include <linux/capability.h>
+#include <linux/if.h>
+#include <linux/inetdevice.h>
+#include <linux/ip.h>
+#include <linux/list.h>
+#include <linux/rculist.h>
+#include <linux/skbuff.h>
+#include <linux/slab.h>
+#include <linux/tcp.h>
+
+#include <net/ip.h>
+#include <net/tcp.h>
+
+#include <linux/netfilter/nfnetlink.h>
+#include <linux/netfilter/x_tables.h>
+#include <net/netfilter/nf_log.h>
+#include <linux/netfilter/nfnetlink_osf.h>
+
+/*
+ * Indexed by dont-fragment bit.
+ * It is the only constant value in the fingerprint.
+ */
+struct list_head nf_osf_fingers[2];
+EXPORT_SYMBOL_GPL(nf_osf_fingers);
+
+static inline int nf_osf_ttl(const struct sk_buff *skb,
+			     int ttl_check, unsigned char f_ttl)
+{
+	const struct iphdr *ip = ip_hdr(skb);
+
+	if (ttl_check != -1) {
+		if (ttl_check == NF_OSF_TTL_TRUE)
+			return ip->ttl == f_ttl;
+		if (ttl_check == NF_OSF_TTL_NOCHECK)
+			return 1;
+		else if (ip->ttl <= f_ttl)
+			return 1;
+		else {
+			struct in_device *in_dev = __in_dev_get_rcu(skb->dev);
+			int ret = 0;
+
+			for_ifa(in_dev) {
+				if (inet_ifa_match(ip->saddr, ifa)) {
+					ret = (ip->ttl == f_ttl);
+					break;
+				}
+			}
+			endfor_ifa(in_dev);
+
+			return ret;
+		}
+	}
+
+	return ip->ttl == f_ttl;
+}
+
+struct nf_osf_hdr_ctx {
+	bool			df;
+	u16			window;
+	u16			totlen;
+	const unsigned char	*optp;
+	unsigned int		optsize;
+};
+
+static bool nf_osf_match_one(const struct sk_buff *skb,
+			     const struct nf_osf_user_finger *f,
+			     int ttl_check,
+			     struct nf_osf_hdr_ctx *ctx)
+{
+	unsigned int check_WSS = 0;
+	int fmatch = FMATCH_WRONG;
+	int foptsize, optnum;
+	u16 mss = 0;
+
+	if (ctx->totlen != f->ss || !nf_osf_ttl(skb, ttl_check, f->ttl))
+		return false;
+
+	/*
+	 * Should not happen if userspace parser was written correctly.
+	 */
+	if (f->wss.wc >= OSF_WSS_MAX)
+		return false;
+
+	/* Check options */
+
+	foptsize = 0;
+	for (optnum = 0; optnum < f->opt_num; ++optnum)
+		foptsize += f->opt[optnum].length;
+
+	if (foptsize > MAX_IPOPTLEN ||
+	    ctx->optsize > MAX_IPOPTLEN ||
+	    ctx->optsize != foptsize)
+		return false;
+
+	check_WSS = f->wss.wc;
+
+	for (optnum = 0; optnum < f->opt_num; ++optnum) {
+		if (f->opt[optnum].kind == *ctx->optp) {
+			__u32 len = f->opt[optnum].length;
+			const __u8 *optend = ctx->optp + len;
+
+			fmatch = FMATCH_OK;
+
+			switch (*ctx->optp) {
+			case OSFOPT_MSS:
+				mss = ctx->optp[3];
+				mss <<= 8;
+				mss |= ctx->optp[2];
+
+				mss = ntohs((__force __be16)mss);
+				break;
+			case OSFOPT_TS:
+				break;
+			}
+
+			ctx->optp = optend;
+		} else
+			fmatch = FMATCH_OPT_WRONG;
+
+		if (fmatch != FMATCH_OK)
+			break;
+	}
+
+	if (fmatch != FMATCH_OPT_WRONG) {
+		fmatch = FMATCH_WRONG;
+
+		switch (check_WSS) {
+		case OSF_WSS_PLAIN:
+			if (f->wss.val == 0 || ctx->window == f->wss.val)
+				fmatch = FMATCH_OK;
+			break;
+		case OSF_WSS_MSS:
+			/*
+			 * Some smart modems decrease mangle MSS to
+			 * SMART_MSS_2, so we check standard, decreased
+			 * and the one provided in the fingerprint MSS
+			 * values.
+			 */
+#define SMART_MSS_1	1460
+#define SMART_MSS_2	1448
+			if (ctx->window == f->wss.val * mss ||
+			    ctx->window == f->wss.val * SMART_MSS_1 ||
+			    ctx->window == f->wss.val * SMART_MSS_2)
+				fmatch = FMATCH_OK;
+			break;
+		case OSF_WSS_MTU:
+			if (ctx->window == f->wss.val * (mss + 40) ||
+			    ctx->window == f->wss.val * (SMART_MSS_1 + 40) ||
+			    ctx->window == f->wss.val * (SMART_MSS_2 + 40))
+				fmatch = FMATCH_OK;
+			break;
+		case OSF_WSS_MODULO:
+			if ((ctx->window % f->wss.val) == 0)
+				fmatch = FMATCH_OK;
+			break;
+		}
+	}
+
+	return fmatch == FMATCH_OK;
+}
+
+static const struct tcphdr *nf_osf_hdr_ctx_init(struct nf_osf_hdr_ctx *ctx,
+						const struct sk_buff *skb,
+						const struct iphdr *ip,
+						unsigned char *opts)
+{
+	const struct tcphdr *tcp;
+	struct tcphdr _tcph;
+
+	tcp = skb_header_pointer(skb, ip_hdrlen(skb), sizeof(struct tcphdr), &_tcph);
+	if (!tcp)
+		return NULL;
+
+	if (!tcp->syn)
+		return NULL;
+
+	ctx->totlen = ntohs(ip->tot_len);
+	ctx->df = ntohs(ip->frag_off) & IP_DF;
+	ctx->window = ntohs(tcp->window);
+
+	if (tcp->doff * 4 > sizeof(struct tcphdr)) {
+		ctx->optsize = tcp->doff * 4 - sizeof(struct tcphdr);
+
+		ctx->optp = skb_header_pointer(skb, ip_hdrlen(skb) +
+				sizeof(struct tcphdr), ctx->optsize, opts);
+	}
+
+	return tcp;
+}
+
+bool
+nf_osf_match(const struct sk_buff *skb, u_int8_t family,
+	     int hooknum, struct net_device *in, struct net_device *out,
+	     const struct nf_osf_info *info, struct net *net,
+	     const struct list_head *nf_osf_fingers)
+{
+	const struct iphdr *ip = ip_hdr(skb);
+	const struct nf_osf_user_finger *f;
+	unsigned char opts[MAX_IPOPTLEN];
+	const struct nf_osf_finger *kf;
+	int fcount = 0, ttl_check;
+	int fmatch = FMATCH_WRONG;
+	struct nf_osf_hdr_ctx ctx;
+	const struct tcphdr *tcp;
+
+	memset(&ctx, 0, sizeof(ctx));
+
+	tcp = nf_osf_hdr_ctx_init(&ctx, skb, ip, opts);
+	if (!tcp)
+		return false;
+
+	ttl_check = (info->flags & NF_OSF_TTL) ? info->ttl : -1;
+
+	list_for_each_entry_rcu(kf, &nf_osf_fingers[ctx.df], finger_entry) {
+
+		f = &kf->finger;
+
+		if (!(info->flags & NF_OSF_LOG) && strcmp(info->genre, f->genre))
+			continue;
+
+		if (!nf_osf_match_one(skb, f, ttl_check, &ctx))
+			continue;
+
+		fmatch = FMATCH_OK;
+
+		fcount++;
+
+		if (info->flags & NF_OSF_LOG)
+			nf_log_packet(net, family, hooknum, skb,
+				      in, out, NULL,
+				      "%s [%s:%s] : %pI4:%d -> %pI4:%d hops=%d\n",
+				      f->genre, f->version, f->subtype,
+				      &ip->saddr, ntohs(tcp->source),
+				      &ip->daddr, ntohs(tcp->dest),
+				      f->ttl - ip->ttl);
+
+		if ((info->flags & NF_OSF_LOG) &&
+		    info->loglevel == NF_OSF_LOGLEVEL_FIRST)
+			break;
+	}
+
+	if (!fcount && (info->flags & NF_OSF_LOG))
+		nf_log_packet(net, family, hooknum, skb, in, out, NULL,
+			      "Remote OS is not known: %pI4:%u -> %pI4:%u\n",
+			      &ip->saddr, ntohs(tcp->source),
+			      &ip->daddr, ntohs(tcp->dest));
+
+	if (fcount)
+		fmatch = FMATCH_OK;
+
+	return fmatch == FMATCH_OK;
+}
+EXPORT_SYMBOL_GPL(nf_osf_match);
+
+const char *nf_osf_find(const struct sk_buff *skb,
+			const struct list_head *nf_osf_fingers)
+{
+	const struct iphdr *ip = ip_hdr(skb);
+	const struct nf_osf_user_finger *f;
+	unsigned char opts[MAX_IPOPTLEN];
+	const struct nf_osf_finger *kf;
+	struct nf_osf_hdr_ctx ctx;
+	const struct tcphdr *tcp;
+	const char *genre = NULL;
+
+	memset(&ctx, 0, sizeof(ctx));
+
+	tcp = nf_osf_hdr_ctx_init(&ctx, skb, ip, opts);
+	if (!tcp)
+		return NULL;
+
+	list_for_each_entry_rcu(kf, &nf_osf_fingers[ctx.df], finger_entry) {
+		f = &kf->finger;
+		if (!nf_osf_match_one(skb, f, -1, &ctx))
+			continue;
+
+		genre = f->genre;
+		break;
+	}
+
+	return genre;
+}
+EXPORT_SYMBOL_GPL(nf_osf_find);
+
+static const struct nla_policy nfnl_osf_policy[OSF_ATTR_MAX + 1] = {
+	[OSF_ATTR_FINGER]	= { .len = sizeof(struct nf_osf_user_finger) },
+};
+
+static int nfnl_osf_add_callback(struct net *net, struct sock *ctnl,
+				 struct sk_buff *skb, const struct nlmsghdr *nlh,
+				 const struct nlattr * const osf_attrs[],
+				 struct netlink_ext_ack *extack)
+{
+	struct nf_osf_user_finger *f;
+	struct nf_osf_finger *kf = NULL, *sf;
+	int err = 0;
+
+	if (!capable(CAP_NET_ADMIN))
+		return -EPERM;
+
+	if (!osf_attrs[OSF_ATTR_FINGER])
+		return -EINVAL;
+
+	if (!(nlh->nlmsg_flags & NLM_F_CREATE))
+		return -EINVAL;
+
+	f = nla_data(osf_attrs[OSF_ATTR_FINGER]);
+
+	kf = kmalloc(sizeof(struct nf_osf_finger), GFP_KERNEL);
+	if (!kf)
+		return -ENOMEM;
+
+	memcpy(&kf->finger, f, sizeof(struct nf_osf_user_finger));
+
+	list_for_each_entry(sf, &nf_osf_fingers[!!f->df], finger_entry) {
+		if (memcmp(&sf->finger, f, sizeof(struct nf_osf_user_finger)))
+			continue;
+
+		kfree(kf);
+		kf = NULL;
+
+		if (nlh->nlmsg_flags & NLM_F_EXCL)
+			err = -EEXIST;
+		break;
+	}
+
+	/*
+	 * We are protected by nfnl mutex.
+	 */
+	if (kf)
+		list_add_tail_rcu(&kf->finger_entry, &nf_osf_fingers[!!f->df]);
+
+	return err;
+}
+
+static int nfnl_osf_remove_callback(struct net *net, struct sock *ctnl,
+				    struct sk_buff *skb,
+				    const struct nlmsghdr *nlh,
+				    const struct nlattr * const osf_attrs[],
+				    struct netlink_ext_ack *extack)
+{
+	struct nf_osf_user_finger *f;
+	struct nf_osf_finger *sf;
+	int err = -ENOENT;
+
+	if (!capable(CAP_NET_ADMIN))
+		return -EPERM;
+
+	if (!osf_attrs[OSF_ATTR_FINGER])
+		return -EINVAL;
+
+	f = nla_data(osf_attrs[OSF_ATTR_FINGER]);
+
+	list_for_each_entry(sf, &nf_osf_fingers[!!f->df], finger_entry) {
+		if (memcmp(&sf->finger, f, sizeof(struct nf_osf_user_finger)))
+			continue;
+
+		/*
+		 * We are protected by nfnl mutex.
+		 */
+		list_del_rcu(&sf->finger_entry);
+		kfree_rcu(sf, rcu_head);
+
+		err = 0;
+		break;
+	}
+
+	return err;
+}
+
+static const struct nfnl_callback nfnl_osf_callbacks[OSF_MSG_MAX] = {
+	[OSF_MSG_ADD]	= {
+		.call		= nfnl_osf_add_callback,
+		.attr_count	= OSF_ATTR_MAX,
+		.policy		= nfnl_osf_policy,
+	},
+	[OSF_MSG_REMOVE]	= {
+		.call		= nfnl_osf_remove_callback,
+		.attr_count	= OSF_ATTR_MAX,
+		.policy		= nfnl_osf_policy,
+	},
+};
+
+static const struct nfnetlink_subsystem nfnl_osf_subsys = {
+	.name			= "osf",
+	.subsys_id		= NFNL_SUBSYS_OSF,
+	.cb_count		= OSF_MSG_MAX,
+	.cb			= nfnl_osf_callbacks,
+};
+
+static int __init nfnl_osf_init(void)
+{
+	int err = -EINVAL;
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(nf_osf_fingers); ++i)
+		INIT_LIST_HEAD(&nf_osf_fingers[i]);
+
+	err = nfnetlink_subsys_register(&nfnl_osf_subsys);
+	if (err < 0) {
+		pr_err("Failed to register OSF nsfnetlink helper (%d)\n", err);
+		goto err_out_exit;
+	}
+	return 0;
+
+err_out_exit:
+	return err;
+}
+
+static void __exit nfnl_osf_fini(void)
+{
+	struct nf_osf_finger *f;
+	int i;
+
+	nfnetlink_subsys_unregister(&nfnl_osf_subsys);
+
+	rcu_read_lock();
+	for (i = 0; i < ARRAY_SIZE(nf_osf_fingers); ++i) {
+		list_for_each_entry_rcu(f, &nf_osf_fingers[i], finger_entry) {
+			list_del_rcu(&f->finger_entry);
+			kfree_rcu(f, rcu_head);
+		}
+	}
+	rcu_read_unlock();
+
+	rcu_barrier();
+}
+
+module_init(nfnl_osf_init);
+module_exit(nfnl_osf_fini);
+
+MODULE_LICENSE("GPL");