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 8 struct nft_osf { 9 u8 dreg; 10 u8 ttl; 11 u32 flags; 12 }; 13 14 static 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 20 static 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 60 static 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 90 static 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; 105 106 nla_put_failure: 107 return -1; 108 } 109 110 static int nft_osf_validate(const struct nft_ctx *ctx, 111 const struct nft_expr *expr, 112 const struct nft_data **data) 113 { 114 unsigned int hooks; 115 116 switch (ctx->family) { 117 case NFPROTO_IPV4: 118 case NFPROTO_IPV6: 119 case NFPROTO_INET: 120 hooks = (1 << NF_INET_LOCAL_IN) | 121 (1 << NF_INET_PRE_ROUTING) | 122 (1 << NF_INET_FORWARD); 123 break; 124 default: 125 return -EOPNOTSUPP; 126 } 127 128 return nft_chain_validate_hooks(ctx->chain, hooks); 129 } 130 131 static bool nft_osf_reduce(struct nft_regs_track *track, 132 const struct nft_expr *expr) 133 { 134 struct nft_osf *priv = nft_expr_priv(expr); 135 struct nft_osf *osf; 136 137 if (!nft_reg_track_cmp(track, expr, priv->dreg)) { 138 nft_reg_track_update(track, expr, priv->dreg, NFT_OSF_MAXGENRELEN); 139 return false; 140 } 141 142 osf = nft_expr_priv(track->regs[priv->dreg].selector); 143 if (priv->flags != osf->flags || 144 priv->ttl != osf->ttl) { 145 nft_reg_track_update(track, expr, priv->dreg, NFT_OSF_MAXGENRELEN); 146 return false; 147 } 148 149 if (!track->regs[priv->dreg].bitwise) 150 return true; 151 152 return false; 153 } 154 155 static struct nft_expr_type nft_osf_type; 156 static const struct nft_expr_ops nft_osf_op = { 157 .eval = nft_osf_eval, 158 .size = NFT_EXPR_SIZE(sizeof(struct nft_osf)), 159 .init = nft_osf_init, 160 .dump = nft_osf_dump, 161 .type = &nft_osf_type, 162 .validate = nft_osf_validate, 163 .reduce = nft_osf_reduce, 164 }; 165 166 static struct nft_expr_type nft_osf_type __read_mostly = { 167 .ops = &nft_osf_op, 168 .name = "osf", 169 .owner = THIS_MODULE, 170 .policy = nft_osf_policy, 171 .maxattr = NFTA_OSF_MAX, 172 }; 173 174 static int __init nft_osf_module_init(void) 175 { 176 return nft_register_expr(&nft_osf_type); 177 } 178 179 static void __exit nft_osf_module_exit(void) 180 { 181 return nft_unregister_expr(&nft_osf_type); 182 } 183 184 module_init(nft_osf_module_init); 185 module_exit(nft_osf_module_exit); 186 187 MODULE_LICENSE("GPL"); 188 MODULE_AUTHOR("Fernando Fernandez <ffmancera@riseup.net>"); 189 MODULE_ALIAS_NFT_EXPR("osf"); 190 MODULE_DESCRIPTION("nftables passive OS fingerprint support"); 191