// SPDX-License-Identifier: GPL-2.0-only
|
#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)
|
{
|
struct in_device *in_dev = __in_dev_get_rcu(skb->dev);
|
const struct iphdr *ip = ip_hdr(skb);
|
const struct in_ifaddr *ifa;
|
int ret = 0;
|
|
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;
|
|
in_dev_for_each_ifa_rcu(ifa, in_dev) {
|
if (inet_ifa_match(ip->saddr, ifa)) {
|
ret = (ip->ttl == f_ttl);
|
break;
|
}
|
}
|
|
return ret;
|
}
|
|
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)
|
{
|
const __u8 *optpinit = ctx->optp;
|
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;
|
}
|
}
|
|
if (fmatch != FMATCH_OK)
|
ctx->optp = optpinit;
|
|
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,
|
struct tcphdr *_tcph)
|
{
|
const struct tcphdr *tcp;
|
|
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);
|
if (!ctx->optp)
|
return NULL;
|
}
|
|
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;
|
struct tcphdr _tcph;
|
|
memset(&ctx, 0, sizeof(ctx));
|
|
tcp = nf_osf_hdr_ctx_init(&ctx, skb, ip, opts, &_tcph);
|
if (!tcp)
|
return false;
|
|
ttl_check = (info->flags & NF_OSF_TTL) ? info->ttl : 0;
|
|
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);
|
|
bool nf_osf_find(const struct sk_buff *skb,
|
const struct list_head *nf_osf_fingers,
|
const int ttl_check, struct nf_osf_data *data)
|
{
|
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;
|
struct tcphdr _tcph;
|
bool found = false;
|
|
memset(&ctx, 0, sizeof(ctx));
|
|
tcp = nf_osf_hdr_ctx_init(&ctx, skb, ip, opts, &_tcph);
|
if (!tcp)
|
return false;
|
|
list_for_each_entry_rcu(kf, &nf_osf_fingers[ctx.df], finger_entry) {
|
f = &kf->finger;
|
if (!nf_osf_match_one(skb, f, ttl_check, &ctx))
|
continue;
|
|
data->genre = f->genre;
|
data->version = f->version;
|
found = true;
|
break;
|
}
|
|
return found;
|
}
|
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");
|
