Patrick McHardy | 48b1de4 | 2013-08-27 08:50:14 +0200 | [diff] [blame] | 1 | /* |
| 2 | * Copyright (c) 2013 Patrick McHardy <kaber@trash.net> |
| 3 | * |
| 4 | * This program is free software; you can redistribute it and/or modify |
| 5 | * it under the terms of the GNU General Public License version 2 as |
| 6 | * published by the Free Software Foundation. |
| 7 | */ |
| 8 | |
| 9 | #include <linux/module.h> |
| 10 | #include <linux/skbuff.h> |
| 11 | #include <asm/unaligned.h> |
| 12 | #include <net/tcp.h> |
| 13 | #include <net/netns/generic.h> |
| 14 | |
| 15 | #include <linux/netfilter_ipv4/ip_tables.h> |
| 16 | #include <linux/netfilter/x_tables.h> |
| 17 | #include <linux/netfilter/xt_tcpudp.h> |
| 18 | #include <linux/netfilter/xt_SYNPROXY.h> |
| 19 | #include <net/netfilter/nf_conntrack.h> |
| 20 | #include <net/netfilter/nf_conntrack_extend.h> |
| 21 | #include <net/netfilter/nf_conntrack_seqadj.h> |
| 22 | #include <net/netfilter/nf_conntrack_synproxy.h> |
| 23 | |
| 24 | int synproxy_net_id; |
| 25 | EXPORT_SYMBOL_GPL(synproxy_net_id); |
| 26 | |
Patrick McHardy | f4a87e7 | 2013-09-30 08:51:46 +0100 | [diff] [blame] | 27 | bool |
Patrick McHardy | 48b1de4 | 2013-08-27 08:50:14 +0200 | [diff] [blame] | 28 | synproxy_parse_options(const struct sk_buff *skb, unsigned int doff, |
| 29 | const struct tcphdr *th, struct synproxy_options *opts) |
| 30 | { |
| 31 | int length = (th->doff * 4) - sizeof(*th); |
| 32 | u8 buf[40], *ptr; |
| 33 | |
| 34 | ptr = skb_header_pointer(skb, doff + sizeof(*th), length, buf); |
Patrick McHardy | f4a87e7 | 2013-09-30 08:51:46 +0100 | [diff] [blame] | 35 | if (ptr == NULL) |
| 36 | return false; |
Patrick McHardy | 48b1de4 | 2013-08-27 08:50:14 +0200 | [diff] [blame] | 37 | |
| 38 | opts->options = 0; |
| 39 | while (length > 0) { |
| 40 | int opcode = *ptr++; |
| 41 | int opsize; |
| 42 | |
| 43 | switch (opcode) { |
| 44 | case TCPOPT_EOL: |
Patrick McHardy | f4a87e7 | 2013-09-30 08:51:46 +0100 | [diff] [blame] | 45 | return true; |
Patrick McHardy | 48b1de4 | 2013-08-27 08:50:14 +0200 | [diff] [blame] | 46 | case TCPOPT_NOP: |
| 47 | length--; |
| 48 | continue; |
| 49 | default: |
| 50 | opsize = *ptr++; |
| 51 | if (opsize < 2) |
Patrick McHardy | f4a87e7 | 2013-09-30 08:51:46 +0100 | [diff] [blame] | 52 | return true; |
Patrick McHardy | 48b1de4 | 2013-08-27 08:50:14 +0200 | [diff] [blame] | 53 | if (opsize > length) |
Patrick McHardy | f4a87e7 | 2013-09-30 08:51:46 +0100 | [diff] [blame] | 54 | return true; |
Patrick McHardy | 48b1de4 | 2013-08-27 08:50:14 +0200 | [diff] [blame] | 55 | |
| 56 | switch (opcode) { |
| 57 | case TCPOPT_MSS: |
| 58 | if (opsize == TCPOLEN_MSS) { |
| 59 | opts->mss = get_unaligned_be16(ptr); |
| 60 | opts->options |= XT_SYNPROXY_OPT_MSS; |
| 61 | } |
| 62 | break; |
| 63 | case TCPOPT_WINDOW: |
| 64 | if (opsize == TCPOLEN_WINDOW) { |
| 65 | opts->wscale = *ptr; |
| 66 | if (opts->wscale > 14) |
| 67 | opts->wscale = 14; |
| 68 | opts->options |= XT_SYNPROXY_OPT_WSCALE; |
| 69 | } |
| 70 | break; |
| 71 | case TCPOPT_TIMESTAMP: |
| 72 | if (opsize == TCPOLEN_TIMESTAMP) { |
| 73 | opts->tsval = get_unaligned_be32(ptr); |
| 74 | opts->tsecr = get_unaligned_be32(ptr + 4); |
| 75 | opts->options |= XT_SYNPROXY_OPT_TIMESTAMP; |
| 76 | } |
| 77 | break; |
| 78 | case TCPOPT_SACK_PERM: |
| 79 | if (opsize == TCPOLEN_SACK_PERM) |
| 80 | opts->options |= XT_SYNPROXY_OPT_SACK_PERM; |
| 81 | break; |
| 82 | } |
| 83 | |
| 84 | ptr += opsize - 2; |
| 85 | length -= opsize; |
| 86 | } |
| 87 | } |
Patrick McHardy | f4a87e7 | 2013-09-30 08:51:46 +0100 | [diff] [blame] | 88 | return true; |
Patrick McHardy | 48b1de4 | 2013-08-27 08:50:14 +0200 | [diff] [blame] | 89 | } |
| 90 | EXPORT_SYMBOL_GPL(synproxy_parse_options); |
| 91 | |
| 92 | unsigned int synproxy_options_size(const struct synproxy_options *opts) |
| 93 | { |
| 94 | unsigned int size = 0; |
| 95 | |
| 96 | if (opts->options & XT_SYNPROXY_OPT_MSS) |
| 97 | size += TCPOLEN_MSS_ALIGNED; |
| 98 | if (opts->options & XT_SYNPROXY_OPT_TIMESTAMP) |
| 99 | size += TCPOLEN_TSTAMP_ALIGNED; |
| 100 | else if (opts->options & XT_SYNPROXY_OPT_SACK_PERM) |
| 101 | size += TCPOLEN_SACKPERM_ALIGNED; |
| 102 | if (opts->options & XT_SYNPROXY_OPT_WSCALE) |
| 103 | size += TCPOLEN_WSCALE_ALIGNED; |
| 104 | |
| 105 | return size; |
| 106 | } |
| 107 | EXPORT_SYMBOL_GPL(synproxy_options_size); |
| 108 | |
| 109 | void |
| 110 | synproxy_build_options(struct tcphdr *th, const struct synproxy_options *opts) |
| 111 | { |
| 112 | __be32 *ptr = (__be32 *)(th + 1); |
| 113 | u8 options = opts->options; |
| 114 | |
| 115 | if (options & XT_SYNPROXY_OPT_MSS) |
| 116 | *ptr++ = htonl((TCPOPT_MSS << 24) | |
| 117 | (TCPOLEN_MSS << 16) | |
| 118 | opts->mss); |
| 119 | |
| 120 | if (options & XT_SYNPROXY_OPT_TIMESTAMP) { |
| 121 | if (options & XT_SYNPROXY_OPT_SACK_PERM) |
| 122 | *ptr++ = htonl((TCPOPT_SACK_PERM << 24) | |
| 123 | (TCPOLEN_SACK_PERM << 16) | |
| 124 | (TCPOPT_TIMESTAMP << 8) | |
| 125 | TCPOLEN_TIMESTAMP); |
| 126 | else |
| 127 | *ptr++ = htonl((TCPOPT_NOP << 24) | |
| 128 | (TCPOPT_NOP << 16) | |
| 129 | (TCPOPT_TIMESTAMP << 8) | |
| 130 | TCPOLEN_TIMESTAMP); |
| 131 | |
| 132 | *ptr++ = htonl(opts->tsval); |
| 133 | *ptr++ = htonl(opts->tsecr); |
| 134 | } else if (options & XT_SYNPROXY_OPT_SACK_PERM) |
| 135 | *ptr++ = htonl((TCPOPT_NOP << 24) | |
| 136 | (TCPOPT_NOP << 16) | |
| 137 | (TCPOPT_SACK_PERM << 8) | |
| 138 | TCPOLEN_SACK_PERM); |
| 139 | |
| 140 | if (options & XT_SYNPROXY_OPT_WSCALE) |
| 141 | *ptr++ = htonl((TCPOPT_NOP << 24) | |
| 142 | (TCPOPT_WINDOW << 16) | |
| 143 | (TCPOLEN_WINDOW << 8) | |
| 144 | opts->wscale); |
| 145 | } |
| 146 | EXPORT_SYMBOL_GPL(synproxy_build_options); |
| 147 | |
| 148 | void synproxy_init_timestamp_cookie(const struct xt_synproxy_info *info, |
| 149 | struct synproxy_options *opts) |
| 150 | { |
| 151 | opts->tsecr = opts->tsval; |
| 152 | opts->tsval = tcp_time_stamp & ~0x3f; |
| 153 | |
Martin Topholm | c1898c4 | 2013-11-14 15:35:31 +0100 | [diff] [blame] | 154 | if (opts->options & XT_SYNPROXY_OPT_WSCALE) { |
| 155 | opts->tsval |= opts->wscale; |
| 156 | opts->wscale = info->wscale; |
| 157 | } else |
Patrick McHardy | 48b1de4 | 2013-08-27 08:50:14 +0200 | [diff] [blame] | 158 | opts->tsval |= 0xf; |
| 159 | |
| 160 | if (opts->options & XT_SYNPROXY_OPT_SACK_PERM) |
| 161 | opts->tsval |= 1 << 4; |
| 162 | |
| 163 | if (opts->options & XT_SYNPROXY_OPT_ECN) |
| 164 | opts->tsval |= 1 << 5; |
| 165 | } |
| 166 | EXPORT_SYMBOL_GPL(synproxy_init_timestamp_cookie); |
| 167 | |
| 168 | void synproxy_check_timestamp_cookie(struct synproxy_options *opts) |
| 169 | { |
| 170 | opts->wscale = opts->tsecr & 0xf; |
| 171 | if (opts->wscale != 0xf) |
| 172 | opts->options |= XT_SYNPROXY_OPT_WSCALE; |
| 173 | |
| 174 | opts->options |= opts->tsecr & (1 << 4) ? XT_SYNPROXY_OPT_SACK_PERM : 0; |
| 175 | |
| 176 | opts->options |= opts->tsecr & (1 << 5) ? XT_SYNPROXY_OPT_ECN : 0; |
| 177 | } |
| 178 | EXPORT_SYMBOL_GPL(synproxy_check_timestamp_cookie); |
| 179 | |
| 180 | unsigned int synproxy_tstamp_adjust(struct sk_buff *skb, |
| 181 | unsigned int protoff, |
| 182 | struct tcphdr *th, |
| 183 | struct nf_conn *ct, |
| 184 | enum ip_conntrack_info ctinfo, |
| 185 | const struct nf_conn_synproxy *synproxy) |
| 186 | { |
| 187 | unsigned int optoff, optend; |
| 188 | u32 *ptr, old; |
| 189 | |
| 190 | if (synproxy->tsoff == 0) |
| 191 | return 1; |
| 192 | |
| 193 | optoff = protoff + sizeof(struct tcphdr); |
| 194 | optend = protoff + th->doff * 4; |
| 195 | |
| 196 | if (!skb_make_writable(skb, optend)) |
| 197 | return 0; |
| 198 | |
| 199 | while (optoff < optend) { |
| 200 | unsigned char *op = skb->data + optoff; |
| 201 | |
| 202 | switch (op[0]) { |
| 203 | case TCPOPT_EOL: |
| 204 | return 1; |
| 205 | case TCPOPT_NOP: |
| 206 | optoff++; |
| 207 | continue; |
| 208 | default: |
| 209 | if (optoff + 1 == optend || |
| 210 | optoff + op[1] > optend || |
| 211 | op[1] < 2) |
| 212 | return 0; |
| 213 | if (op[0] == TCPOPT_TIMESTAMP && |
| 214 | op[1] == TCPOLEN_TIMESTAMP) { |
| 215 | if (CTINFO2DIR(ctinfo) == IP_CT_DIR_REPLY) { |
| 216 | ptr = (u32 *)&op[2]; |
| 217 | old = *ptr; |
| 218 | *ptr = htonl(ntohl(*ptr) - |
| 219 | synproxy->tsoff); |
| 220 | } else { |
| 221 | ptr = (u32 *)&op[6]; |
| 222 | old = *ptr; |
| 223 | *ptr = htonl(ntohl(*ptr) + |
| 224 | synproxy->tsoff); |
| 225 | } |
| 226 | inet_proto_csum_replace4(&th->check, skb, |
| 227 | old, *ptr, 0); |
| 228 | return 1; |
| 229 | } |
| 230 | optoff += op[1]; |
| 231 | } |
| 232 | } |
| 233 | return 1; |
| 234 | } |
| 235 | EXPORT_SYMBOL_GPL(synproxy_tstamp_adjust); |
| 236 | |
| 237 | static struct nf_ct_ext_type nf_ct_synproxy_extend __read_mostly = { |
| 238 | .len = sizeof(struct nf_conn_synproxy), |
| 239 | .align = __alignof__(struct nf_conn_synproxy), |
| 240 | .id = NF_CT_EXT_SYNPROXY, |
| 241 | }; |
| 242 | |
| 243 | #ifdef CONFIG_PROC_FS |
| 244 | static void *synproxy_cpu_seq_start(struct seq_file *seq, loff_t *pos) |
| 245 | { |
| 246 | struct synproxy_net *snet = synproxy_pernet(seq_file_net(seq)); |
| 247 | int cpu; |
| 248 | |
| 249 | if (*pos == 0) |
| 250 | return SEQ_START_TOKEN; |
| 251 | |
| 252 | for (cpu = *pos - 1; cpu < nr_cpu_ids; cpu++) { |
| 253 | if (!cpu_possible(cpu)) |
| 254 | continue; |
| 255 | *pos = cpu + 1; |
| 256 | return per_cpu_ptr(snet->stats, cpu); |
| 257 | } |
| 258 | |
| 259 | return NULL; |
| 260 | } |
| 261 | |
| 262 | static void *synproxy_cpu_seq_next(struct seq_file *seq, void *v, loff_t *pos) |
| 263 | { |
| 264 | struct synproxy_net *snet = synproxy_pernet(seq_file_net(seq)); |
| 265 | int cpu; |
| 266 | |
| 267 | for (cpu = *pos; cpu < nr_cpu_ids; cpu++) { |
| 268 | if (!cpu_possible(cpu)) |
| 269 | continue; |
| 270 | *pos = cpu + 1; |
| 271 | return per_cpu_ptr(snet->stats, cpu); |
| 272 | } |
| 273 | |
| 274 | return NULL; |
| 275 | } |
| 276 | |
| 277 | static void synproxy_cpu_seq_stop(struct seq_file *seq, void *v) |
| 278 | { |
| 279 | return; |
| 280 | } |
| 281 | |
| 282 | static int synproxy_cpu_seq_show(struct seq_file *seq, void *v) |
| 283 | { |
| 284 | struct synproxy_stats *stats = v; |
| 285 | |
| 286 | if (v == SEQ_START_TOKEN) { |
| 287 | seq_printf(seq, "entries\t\tsyn_received\t" |
| 288 | "cookie_invalid\tcookie_valid\t" |
| 289 | "cookie_retrans\tconn_reopened\n"); |
| 290 | return 0; |
| 291 | } |
| 292 | |
| 293 | seq_printf(seq, "%08x\t%08x\t%08x\t%08x\t%08x\t%08x\n", 0, |
| 294 | stats->syn_received, |
| 295 | stats->cookie_invalid, |
| 296 | stats->cookie_valid, |
| 297 | stats->cookie_retrans, |
| 298 | stats->conn_reopened); |
| 299 | |
| 300 | return 0; |
| 301 | } |
| 302 | |
| 303 | static const struct seq_operations synproxy_cpu_seq_ops = { |
| 304 | .start = synproxy_cpu_seq_start, |
| 305 | .next = synproxy_cpu_seq_next, |
| 306 | .stop = synproxy_cpu_seq_stop, |
| 307 | .show = synproxy_cpu_seq_show, |
| 308 | }; |
| 309 | |
| 310 | static int synproxy_cpu_seq_open(struct inode *inode, struct file *file) |
| 311 | { |
| 312 | return seq_open_net(inode, file, &synproxy_cpu_seq_ops, |
| 313 | sizeof(struct seq_net_private)); |
| 314 | } |
| 315 | |
| 316 | static const struct file_operations synproxy_cpu_seq_fops = { |
| 317 | .owner = THIS_MODULE, |
| 318 | .open = synproxy_cpu_seq_open, |
| 319 | .read = seq_read, |
| 320 | .llseek = seq_lseek, |
| 321 | .release = seq_release_net, |
| 322 | }; |
| 323 | |
| 324 | static int __net_init synproxy_proc_init(struct net *net) |
| 325 | { |
| 326 | if (!proc_create("synproxy", S_IRUGO, net->proc_net_stat, |
| 327 | &synproxy_cpu_seq_fops)) |
| 328 | return -ENOMEM; |
| 329 | return 0; |
| 330 | } |
| 331 | |
| 332 | static void __net_exit synproxy_proc_exit(struct net *net) |
| 333 | { |
| 334 | remove_proc_entry("synproxy", net->proc_net_stat); |
| 335 | } |
| 336 | #else |
| 337 | static int __net_init synproxy_proc_init(struct net *net) |
| 338 | { |
| 339 | return 0; |
| 340 | } |
| 341 | |
| 342 | static void __net_exit synproxy_proc_exit(struct net *net) |
| 343 | { |
| 344 | return; |
| 345 | } |
| 346 | #endif /* CONFIG_PROC_FS */ |
| 347 | |
| 348 | static int __net_init synproxy_net_init(struct net *net) |
| 349 | { |
| 350 | struct synproxy_net *snet = synproxy_pernet(net); |
| 351 | struct nf_conntrack_tuple t; |
| 352 | struct nf_conn *ct; |
| 353 | int err = -ENOMEM; |
| 354 | |
| 355 | memset(&t, 0, sizeof(t)); |
| 356 | ct = nf_conntrack_alloc(net, 0, &t, &t, GFP_KERNEL); |
| 357 | if (IS_ERR(ct)) { |
| 358 | err = PTR_ERR(ct); |
| 359 | goto err1; |
| 360 | } |
| 361 | |
Patrick McHardy | 48b1de4 | 2013-08-27 08:50:14 +0200 | [diff] [blame] | 362 | if (!nfct_seqadj_ext_add(ct)) |
| 363 | goto err2; |
| 364 | if (!nfct_synproxy_ext_add(ct)) |
| 365 | goto err2; |
Patrick McHardy | 48b1de4 | 2013-08-27 08:50:14 +0200 | [diff] [blame] | 366 | |
Pablo Neira Ayuso | e53376b | 2014-02-03 20:01:53 +0100 | [diff] [blame] | 367 | nf_conntrack_tmpl_insert(net, ct); |
Patrick McHardy | 48b1de4 | 2013-08-27 08:50:14 +0200 | [diff] [blame] | 368 | snet->tmpl = ct; |
| 369 | |
| 370 | snet->stats = alloc_percpu(struct synproxy_stats); |
| 371 | if (snet->stats == NULL) |
| 372 | goto err2; |
| 373 | |
| 374 | err = synproxy_proc_init(net); |
| 375 | if (err < 0) |
| 376 | goto err3; |
| 377 | |
| 378 | return 0; |
| 379 | |
| 380 | err3: |
| 381 | free_percpu(snet->stats); |
| 382 | err2: |
| 383 | nf_conntrack_free(ct); |
| 384 | err1: |
| 385 | return err; |
| 386 | } |
| 387 | |
| 388 | static void __net_exit synproxy_net_exit(struct net *net) |
| 389 | { |
| 390 | struct synproxy_net *snet = synproxy_pernet(net); |
| 391 | |
Pablo Neira Ayuso | e53376b | 2014-02-03 20:01:53 +0100 | [diff] [blame] | 392 | nf_ct_put(snet->tmpl); |
Patrick McHardy | 48b1de4 | 2013-08-27 08:50:14 +0200 | [diff] [blame] | 393 | synproxy_proc_exit(net); |
| 394 | free_percpu(snet->stats); |
| 395 | } |
| 396 | |
| 397 | static struct pernet_operations synproxy_net_ops = { |
| 398 | .init = synproxy_net_init, |
| 399 | .exit = synproxy_net_exit, |
| 400 | .id = &synproxy_net_id, |
| 401 | .size = sizeof(struct synproxy_net), |
| 402 | }; |
| 403 | |
| 404 | static int __init synproxy_core_init(void) |
| 405 | { |
| 406 | int err; |
| 407 | |
| 408 | err = nf_ct_extend_register(&nf_ct_synproxy_extend); |
| 409 | if (err < 0) |
| 410 | goto err1; |
| 411 | |
| 412 | err = register_pernet_subsys(&synproxy_net_ops); |
| 413 | if (err < 0) |
| 414 | goto err2; |
| 415 | |
| 416 | return 0; |
| 417 | |
| 418 | err2: |
| 419 | nf_ct_extend_unregister(&nf_ct_synproxy_extend); |
| 420 | err1: |
| 421 | return err; |
| 422 | } |
| 423 | |
| 424 | static void __exit synproxy_core_exit(void) |
| 425 | { |
| 426 | unregister_pernet_subsys(&synproxy_net_ops); |
| 427 | nf_ct_extend_unregister(&nf_ct_synproxy_extend); |
| 428 | } |
| 429 | |
| 430 | module_init(synproxy_core_init); |
| 431 | module_exit(synproxy_core_exit); |
| 432 | |
| 433 | MODULE_LICENSE("GPL"); |
| 434 | MODULE_AUTHOR("Patrick McHardy <kaber@trash.net>"); |