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 + 1]; 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 strncpy((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 strlcpy(os_match, data.genre, NFT_OSF_MAXGENRELEN); 55 56 strncpy((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 int err; 67 u8 ttl; 68 69 if (!tb[NFTA_OSF_DREG]) 70 return -EINVAL; 71 72 if (tb[NFTA_OSF_TTL]) { 73 ttl = nla_get_u8(tb[NFTA_OSF_TTL]); 74 if (ttl > 2) 75 return -EINVAL; 76 priv->ttl = ttl; 77 } 78 79 if (tb[NFTA_OSF_FLAGS]) { 80 flags = ntohl(nla_get_be32(tb[NFTA_OSF_FLAGS])); 81 if (flags != NFT_OSF_F_VERSION) 82 return -EINVAL; 83 priv->flags = flags; 84 } 85 86 err = nft_parse_register_store(ctx, tb[NFTA_OSF_DREG], &priv->dreg, 87 NULL, NFT_DATA_VALUE, 88 NFT_OSF_MAXGENRELEN); 89 if (err < 0) 90 return err; 91 92 return 0; 93 } 94 95 static int nft_osf_dump(struct sk_buff *skb, const struct nft_expr *expr) 96 { 97 const struct nft_osf *priv = nft_expr_priv(expr); 98 99 if (nla_put_u8(skb, NFTA_OSF_TTL, priv->ttl)) 100 goto nla_put_failure; 101 102 if (nla_put_be32(skb, NFTA_OSF_FLAGS, ntohl(priv->flags))) 103 goto nla_put_failure; 104 105 if (nft_dump_register(skb, NFTA_OSF_DREG, priv->dreg)) 106 goto nla_put_failure; 107 108 return 0; 109 110 nla_put_failure: 111 return -1; 112 } 113 114 static int nft_osf_validate(const struct nft_ctx *ctx, 115 const struct nft_expr *expr, 116 const struct nft_data **data) 117 { 118 return nft_chain_validate_hooks(ctx->chain, (1 << NF_INET_LOCAL_IN) | 119 (1 << NF_INET_PRE_ROUTING) | 120 (1 << NF_INET_FORWARD)); 121 } 122 123 static struct nft_expr_type nft_osf_type; 124 static const struct nft_expr_ops nft_osf_op = { 125 .eval = nft_osf_eval, 126 .size = NFT_EXPR_SIZE(sizeof(struct nft_osf)), 127 .init = nft_osf_init, 128 .dump = nft_osf_dump, 129 .type = &nft_osf_type, 130 .validate = nft_osf_validate, 131 }; 132 133 static struct nft_expr_type nft_osf_type __read_mostly = { 134 .ops = &nft_osf_op, 135 .name = "osf", 136 .owner = THIS_MODULE, 137 .policy = nft_osf_policy, 138 .maxattr = NFTA_OSF_MAX, 139 }; 140 141 static int __init nft_osf_module_init(void) 142 { 143 return nft_register_expr(&nft_osf_type); 144 } 145 146 static void __exit nft_osf_module_exit(void) 147 { 148 return nft_unregister_expr(&nft_osf_type); 149 } 150 151 module_init(nft_osf_module_init); 152 module_exit(nft_osf_module_exit); 153 154 MODULE_LICENSE("GPL"); 155 MODULE_AUTHOR("Fernando Fernandez <ffmancera@riseup.net>"); 156 MODULE_ALIAS_NFT_EXPR("osf"); 157 MODULE_DESCRIPTION("nftables passive OS fingerprint support"); 158