1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
|
// SPDX-License-Identifier: GPL-2.0-only
#include <net/ip.h>
#include <net/tcp.h>
#include <net/netfilter/nf_tables.h>
#include <linux/netfilter/nfnetlink_osf.h>
struct nft_osf {
u8 dreg;
u8 ttl;
u32 flags;
};
static const struct nla_policy nft_osf_policy[NFTA_OSF_MAX + 1] = {
[NFTA_OSF_DREG] = { .type = NLA_U32 },
[NFTA_OSF_TTL] = { .type = NLA_U8 },
[NFTA_OSF_FLAGS] = { .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);
u32 *dest = ®s->data[priv->dreg];
struct sk_buff *skb = pkt->skb;
char os_match[NFT_OSF_MAXGENRELEN + 1];
const struct tcphdr *tcp;
struct nf_osf_data data;
struct tcphdr _tcph;
if (pkt->tprot != IPPROTO_TCP) {
regs->verdict.code = NFT_BREAK;
return;
}
tcp = skb_header_pointer(skb, ip_hdrlen(skb),
sizeof(struct tcphdr), &_tcph);
if (!tcp) {
regs->verdict.code = NFT_BREAK;
return;
}
if (!tcp->syn) {
regs->verdict.code = NFT_BREAK;
return;
}
if (!nf_osf_find(skb, nf_osf_fingers, priv->ttl, &data)) {
strncpy((char *)dest, "unknown", NFT_OSF_MAXGENRELEN);
} else {
if (priv->flags & NFT_OSF_F_VERSION)
snprintf(os_match, NFT_OSF_MAXGENRELEN, "%s:%s",
data.genre, data.version);
else
strscpy(os_match, data.genre, NFT_OSF_MAXGENRELEN);
strncpy((char *)dest, os_match, NFT_OSF_MAXGENRELEN);
}
}
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);
u32 flags;
int err;
u8 ttl;
if (!tb[NFTA_OSF_DREG])
return -EINVAL;
if (tb[NFTA_OSF_TTL]) {
ttl = nla_get_u8(tb[NFTA_OSF_TTL]);
if (ttl > 2)
return -EINVAL;
priv->ttl = ttl;
}
if (tb[NFTA_OSF_FLAGS]) {
flags = ntohl(nla_get_be32(tb[NFTA_OSF_FLAGS]));
if (flags != NFT_OSF_F_VERSION)
return -EINVAL;
priv->flags = flags;
}
err = nft_parse_register_store(ctx, tb[NFTA_OSF_DREG], &priv->dreg,
NULL, NFT_DATA_VALUE,
NFT_OSF_MAXGENRELEN);
if (err < 0)
return err;
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_u8(skb, NFTA_OSF_TTL, priv->ttl))
goto nla_put_failure;
if (nla_put_u32(skb, NFTA_OSF_FLAGS, ntohl((__force __be32)priv->flags)))
goto nla_put_failure;
if (nft_dump_register(skb, NFTA_OSF_DREG, priv->dreg))
goto nla_put_failure;
return 0;
nla_put_failure:
return -1;
}
static int nft_osf_validate(const struct nft_ctx *ctx,
const struct nft_expr *expr,
const struct nft_data **data)
{
unsigned int hooks;
switch (ctx->family) {
case NFPROTO_IPV4:
case NFPROTO_IPV6:
case NFPROTO_INET:
hooks = (1 << NF_INET_LOCAL_IN) |
(1 << NF_INET_PRE_ROUTING) |
(1 << NF_INET_FORWARD);
break;
default:
return -EOPNOTSUPP;
}
return nft_chain_validate_hooks(ctx->chain, hooks);
}
static bool nft_osf_reduce(struct nft_regs_track *track,
const struct nft_expr *expr)
{
struct nft_osf *priv = nft_expr_priv(expr);
struct nft_osf *osf;
if (!nft_reg_track_cmp(track, expr, priv->dreg)) {
nft_reg_track_update(track, expr, priv->dreg, NFT_OSF_MAXGENRELEN);
return false;
}
osf = nft_expr_priv(track->regs[priv->dreg].selector);
if (priv->flags != osf->flags ||
priv->ttl != osf->ttl) {
nft_reg_track_update(track, expr, priv->dreg, NFT_OSF_MAXGENRELEN);
return false;
}
if (!track->regs[priv->dreg].bitwise)
return true;
return false;
}
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,
.validate = nft_osf_validate,
.reduce = nft_osf_reduce,
};
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@riseup.net>");
MODULE_ALIAS_NFT_EXPR("osf");
MODULE_DESCRIPTION("nftables passive OS fingerprint support");
|
