ipt_SYNPROXY.c 3.0 KB

123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104105106107108109110111112113114115116117118119120121
  1. // SPDX-License-Identifier: GPL-2.0-only
  2. /*
  3. * Copyright (c) 2013 Patrick McHardy <kaber@trash.net>
  4. */
  5. #include <linux/netfilter_ipv4/ip_tables.h>
  6. #include <linux/netfilter/x_tables.h>
  7. #include <linux/netfilter/xt_SYNPROXY.h>
  8. #include <net/netfilter/nf_synproxy.h>
  9. static unsigned int
  10. synproxy_tg4(struct sk_buff *skb, const struct xt_action_param *par)
  11. {
  12. const struct xt_synproxy_info *info = par->targinfo;
  13. struct net *net = xt_net(par);
  14. struct synproxy_net *snet = synproxy_pernet(net);
  15. struct synproxy_options opts = {};
  16. struct tcphdr *th, _th;
  17. if (nf_ip_checksum(skb, xt_hooknum(par), par->thoff, IPPROTO_TCP))
  18. return NF_DROP;
  19. th = skb_header_pointer(skb, par->thoff, sizeof(_th), &_th);
  20. if (th == NULL)
  21. return NF_DROP;
  22. if (!synproxy_parse_options(skb, par->thoff, th, &opts))
  23. return NF_DROP;
  24. if (th->syn && !(th->ack || th->fin || th->rst)) {
  25. /* Initial SYN from client */
  26. this_cpu_inc(snet->stats->syn_received);
  27. if (th->ece && th->cwr)
  28. opts.options |= XT_SYNPROXY_OPT_ECN;
  29. opts.options &= info->options;
  30. opts.mss_encode = opts.mss_option;
  31. opts.mss_option = info->mss;
  32. if (opts.options & XT_SYNPROXY_OPT_TIMESTAMP)
  33. synproxy_init_timestamp_cookie(info, &opts);
  34. else
  35. opts.options &= ~(XT_SYNPROXY_OPT_WSCALE |
  36. XT_SYNPROXY_OPT_SACK_PERM |
  37. XT_SYNPROXY_OPT_ECN);
  38. synproxy_send_client_synack(net, skb, th, &opts);
  39. consume_skb(skb);
  40. return NF_STOLEN;
  41. } else if (th->ack && !(th->fin || th->rst || th->syn)) {
  42. /* ACK from client */
  43. if (synproxy_recv_client_ack(net, skb, th, &opts, ntohl(th->seq))) {
  44. consume_skb(skb);
  45. return NF_STOLEN;
  46. } else {
  47. return NF_DROP;
  48. }
  49. }
  50. return XT_CONTINUE;
  51. }
  52. static int synproxy_tg4_check(const struct xt_tgchk_param *par)
  53. {
  54. struct synproxy_net *snet = synproxy_pernet(par->net);
  55. const struct ipt_entry *e = par->entryinfo;
  56. int err;
  57. if (e->ip.proto != IPPROTO_TCP ||
  58. e->ip.invflags & XT_INV_PROTO)
  59. return -EINVAL;
  60. err = nf_ct_netns_get(par->net, par->family);
  61. if (err)
  62. return err;
  63. err = nf_synproxy_ipv4_init(snet, par->net);
  64. if (err) {
  65. nf_ct_netns_put(par->net, par->family);
  66. return err;
  67. }
  68. return err;
  69. }
  70. static void synproxy_tg4_destroy(const struct xt_tgdtor_param *par)
  71. {
  72. struct synproxy_net *snet = synproxy_pernet(par->net);
  73. nf_synproxy_ipv4_fini(snet, par->net);
  74. nf_ct_netns_put(par->net, par->family);
  75. }
  76. static struct xt_target synproxy_tg4_reg __read_mostly = {
  77. .name = "SYNPROXY",
  78. .family = NFPROTO_IPV4,
  79. .hooks = (1 << NF_INET_LOCAL_IN) | (1 << NF_INET_FORWARD),
  80. .target = synproxy_tg4,
  81. .targetsize = sizeof(struct xt_synproxy_info),
  82. .checkentry = synproxy_tg4_check,
  83. .destroy = synproxy_tg4_destroy,
  84. .me = THIS_MODULE,
  85. };
  86. static int __init synproxy_tg4_init(void)
  87. {
  88. return xt_register_target(&synproxy_tg4_reg);
  89. }
  90. static void __exit synproxy_tg4_exit(void)
  91. {
  92. xt_unregister_target(&synproxy_tg4_reg);
  93. }
  94. module_init(synproxy_tg4_init);
  95. module_exit(synproxy_tg4_exit);
  96. MODULE_LICENSE("GPL");
  97. MODULE_AUTHOR("Patrick McHardy <kaber@trash.net>");
  98. MODULE_DESCRIPTION("Intercept TCP connections and establish them using syncookies");