Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
tjh.dev
kernel
os
linux
1// SPDX-License-Identifier: GPL-2.0-only
2#include <net/ip.h>
3#include <net/tcp.h>
4
5#include <net/netfilter/nf_tables.h>
6#include <linux/netfilter/nfnetlink_osf.h>
7
8struct nft_osf {
9 u8 dreg;
10 u8 ttl;
11 u32 flags;
12};
13
14static const struct nla_policy nft_osf_policy[NFTA_OSF_MAX + 1] = {
15 [NFTA_OSF_DREG] = { .type = NLA_U32 },
16 [NFTA_OSF_TTL] = { .type = NLA_U8 },
17 [NFTA_OSF_FLAGS] = { .type = NLA_U32 },
18};
19
20static void nft_osf_eval(const struct nft_expr *expr, struct nft_regs *regs,
21 const struct nft_pktinfo *pkt)
22{
23 struct nft_osf *priv = nft_expr_priv(expr);
24 u32 *dest = ®s->data[priv->dreg];
25 struct sk_buff *skb = pkt->skb;
26 char os_match[NFT_OSF_MAXGENRELEN];
27 const struct tcphdr *tcp;
28 struct nf_osf_data data;
29 struct tcphdr _tcph;
30
31 if (pkt->tprot != IPPROTO_TCP) {
32 regs->verdict.code = NFT_BREAK;
33 return;
34 }
35
36 tcp = skb_header_pointer(skb, ip_hdrlen(skb),
37 sizeof(struct tcphdr), &_tcph);
38 if (!tcp) {
39 regs->verdict.code = NFT_BREAK;
40 return;
41 }
42 if (!tcp->syn) {
43 regs->verdict.code = NFT_BREAK;
44 return;
45 }
46
47 if (!nf_osf_find(skb, nf_osf_fingers, priv->ttl, &data)) {
48 strscpy_pad((char *)dest, "unknown", NFT_OSF_MAXGENRELEN);
49 } else {
50 if (priv->flags & NFT_OSF_F_VERSION)
51 snprintf(os_match, NFT_OSF_MAXGENRELEN, "%s:%s",
52 data.genre, data.version);
53 else
54 strscpy(os_match, data.genre, NFT_OSF_MAXGENRELEN);
55
56 strscpy_pad((char *)dest, os_match, NFT_OSF_MAXGENRELEN);
57 }
58}
59
60static int nft_osf_init(const struct nft_ctx *ctx,
61 const struct nft_expr *expr,
62 const struct nlattr * const tb[])
63{
64 struct nft_osf *priv = nft_expr_priv(expr);
65 u32 flags;
66 u8 ttl;
67
68 if (!tb[NFTA_OSF_DREG])
69 return -EINVAL;
70
71 if (tb[NFTA_OSF_TTL]) {
72 ttl = nla_get_u8(tb[NFTA_OSF_TTL]);
73 if (ttl > 2)
74 return -EINVAL;
75 priv->ttl = ttl;
76 }
77
78 if (tb[NFTA_OSF_FLAGS]) {
79 flags = ntohl(nla_get_be32(tb[NFTA_OSF_FLAGS]));
80 if (flags != NFT_OSF_F_VERSION)
81 return -EINVAL;
82 priv->flags = flags;
83 }
84
85 return nft_parse_register_store(ctx, tb[NFTA_OSF_DREG], &priv->dreg,
86 NULL, NFT_DATA_VALUE,
87 NFT_OSF_MAXGENRELEN);
88}
89
90static int nft_osf_dump(struct sk_buff *skb,
91 const struct nft_expr *expr, bool reset)
92{
93 const struct nft_osf *priv = nft_expr_priv(expr);
94
95 if (nla_put_u8(skb, NFTA_OSF_TTL, priv->ttl))
96 goto nla_put_failure;
97
98 if (nla_put_u32(skb, NFTA_OSF_FLAGS, ntohl((__force __be32)priv->flags)))
99 goto nla_put_failure;
100
101 if (nft_dump_register(skb, NFTA_OSF_DREG, priv->dreg))
102 goto nla_put_failure;
103
104 return 0;
105
106nla_put_failure:
107 return -1;
108}
109
110static int nft_osf_validate(const struct nft_ctx *ctx,
111 const struct nft_expr *expr)
112{
113 unsigned int hooks;
114
115 switch (ctx->family) {
116 case NFPROTO_IPV4:
117 case NFPROTO_IPV6:
118 case NFPROTO_INET:
119 hooks = (1 << NF_INET_LOCAL_IN) |
120 (1 << NF_INET_PRE_ROUTING) |
121 (1 << NF_INET_FORWARD);
122 break;
123 default:
124 return -EOPNOTSUPP;
125 }
126
127 return nft_chain_validate_hooks(ctx->chain, hooks);
128}
129
130static bool nft_osf_reduce(struct nft_regs_track *track,
131 const struct nft_expr *expr)
132{
133 struct nft_osf *priv = nft_expr_priv(expr);
134 struct nft_osf *osf;
135
136 if (!nft_reg_track_cmp(track, expr, priv->dreg)) {
137 nft_reg_track_update(track, expr, priv->dreg, NFT_OSF_MAXGENRELEN);
138 return false;
139 }
140
141 osf = nft_expr_priv(track->regs[priv->dreg].selector);
142 if (priv->flags != osf->flags ||
143 priv->ttl != osf->ttl) {
144 nft_reg_track_update(track, expr, priv->dreg, NFT_OSF_MAXGENRELEN);
145 return false;
146 }
147
148 if (!track->regs[priv->dreg].bitwise)
149 return true;
150
151 return false;
152}
153
154static struct nft_expr_type nft_osf_type;
155static const struct nft_expr_ops nft_osf_op = {
156 .eval = nft_osf_eval,
157 .size = NFT_EXPR_SIZE(sizeof(struct nft_osf)),
158 .init = nft_osf_init,
159 .dump = nft_osf_dump,
160 .type = &nft_osf_type,
161 .validate = nft_osf_validate,
162 .reduce = nft_osf_reduce,
163};
164
165static struct nft_expr_type nft_osf_type __read_mostly = {
166 .ops = &nft_osf_op,
167 .name = "osf",
168 .owner = THIS_MODULE,
169 .policy = nft_osf_policy,
170 .maxattr = NFTA_OSF_MAX,
171};
172
173static int __init nft_osf_module_init(void)
174{
175 return nft_register_expr(&nft_osf_type);
176}
177
178static void __exit nft_osf_module_exit(void)
179{
180 return nft_unregister_expr(&nft_osf_type);
181}
182
183module_init(nft_osf_module_init);
184module_exit(nft_osf_module_exit);
185
186MODULE_LICENSE("GPL");
187MODULE_AUTHOR("Fernando Fernandez <ffmancera@riseup.net>");
188MODULE_ALIAS_NFT_EXPR("osf");
189MODULE_DESCRIPTION("nftables passive OS fingerprint support");