net/ipv4/netfilter/ipt_LOG.c

   1 /*
   2  * This is a module which is used for logging packets.
   3  */
   4
   5 /* (C) 1999-2001 Paul `Rusty' Russell
   6  * (C) 2002-2004 Netfilter Core Team <coreteam@netfilter.org>
   7  *
   8  * This program is free software; you can redistribute it and/or modify
   9  * it under the terms of the GNU General Public License version 2 as
  10  * published by the Free Software Foundation.
  11  */
  12 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  13 #include <linux/module.h>
  14 #include <linux/spinlock.h>
  15 #include <linux/skbuff.h>
  16 #include <linux/if_arp.h>
  17 #include <linux/ip.h>
  18 #include <net/icmp.h>
  19 #include <net/udp.h>
  20 #include <net/tcp.h>
  21 #include <net/route.h>
  22
  23 #include <linux/netfilter.h>
  24 #include <linux/netfilter/x_tables.h>
  25 #include <linux/netfilter_ipv4/ipt_LOG.h>
  26 #include <net/netfilter/nf_log.h>
  27 #include <net/netfilter/xt_log.h>
  28
  29 MODULE_LICENSE("GPL");
  30 MODULE_AUTHOR("Netfilter Core Team <coreteam@netfilter.org>");
  31 MODULE_DESCRIPTION("Xtables: IPv4 packet logging to syslog");
  32
  33 /* One level of recursion won't kill us */
  34 static void dump_packet(struct sbuff *m,
  35                         const struct nf_loginfo *info,
  36                         const struct sk_buff *skb,
  37                         unsigned int iphoff)
  38 {
  39         struct iphdr _iph;
  40         const struct iphdr *ih;
  41         unsigned int logflags;
  42
  43         if (info->type == NF_LOG_TYPE_LOG)
  44                 logflags = info->u.log.logflags;
  45         else
  46                 logflags = NF_LOG_MASK;
  47
  48         ih = skb_header_pointer(skb, iphoff, sizeof(_iph), &_iph);
  49         if (ih == NULL) {
  50                 sb_add(m, "TRUNCATED");
  51                 return;
  52         }
  53
  54         /* Important fields:
  55          * TOS, len, DF/MF, fragment offset, TTL, src, dst, options. */
  56         /* Max length: 40 "SRC=255.255.255.255 DST=255.255.255.255 " */
  57         sb_add(m, "SRC=%pI4 DST=%pI4 ",
  58                &ih->saddr, &ih->daddr);
  59
  60         /* Max length: 46 "LEN=65535 TOS=0xFF PREC=0xFF TTL=255 ID=65535 " */
  61         sb_add(m, "LEN=%u TOS=0x%02X PREC=0x%02X TTL=%u ID=%u ",
  62                ntohs(ih->tot_len), ih->tos & IPTOS_TOS_MASK,
  63                ih->tos & IPTOS_PREC_MASK, ih->ttl, ntohs(ih->id));
  64
  65         /* Max length: 6 "CE DF MF " */
  66         if (ntohs(ih->frag_off) & IP_CE)
  67                 sb_add(m, "CE ");
  68         if (ntohs(ih->frag_off) & IP_DF)
  69                 sb_add(m, "DF ");
  70         if (ntohs(ih->frag_off) & IP_MF)
  71                 sb_add(m, "MF ");
  72
  73         /* Max length: 11 "FRAG:65535 " */
  74         if (ntohs(ih->frag_off) & IP_OFFSET)
  75                 sb_add(m, "FRAG:%u ", ntohs(ih->frag_off) & IP_OFFSET);
  76
  77         if ((logflags & IPT_LOG_IPOPT) &&
  78             ih->ihl * 4 > sizeof(struct iphdr)) {
  79                 const unsigned char *op;
  80                 unsigned char _opt[4 * 15 - sizeof(struct iphdr)];
  81                 unsigned int i, optsize;
  82
  83                 optsize = ih->ihl * 4 - sizeof(struct iphdr);
  84                 op = skb_header_pointer(skb, iphoff+sizeof(_iph),
  85                                         optsize, _opt);
  86                 if (op == NULL) {
  87                         sb_add(m, "TRUNCATED");
  88                         return;
  89                 }
  90
  91                 /* Max length: 127 "OPT (" 15*4*2chars ") " */
  92                 sb_add(m, "OPT (");
  93                 for (i = 0; i < optsize; i++)
  94                         sb_add(m, "%02X", op[i]);
  95                 sb_add(m, ") ");
  96         }
  97
  98         switch (ih->protocol) {
  99         case IPPROTO_TCP: {
 100                 struct tcphdr _tcph;
 101                 const struct tcphdr *th;
 102
 103                 /* Max length: 10 "PROTO=TCP " */
 104                 sb_add(m, "PROTO=TCP ");
 105
 106                 if (ntohs(ih->frag_off) & IP_OFFSET)
 107                         break;
 108
 109                 /* Max length: 25 "INCOMPLETE [65535 bytes] " */
 110                 th = skb_header_pointer(skb, iphoff + ih->ihl * 4,
 111                                         sizeof(_tcph), &_tcph);
 112                 if (th == NULL) {
 113                         sb_add(m, "INCOMPLETE [%u bytes] ",
 114                                skb->len - iphoff - ih->ihl*4);
 115                         break;
 116                 }
 117
 118                 /* Max length: 20 "SPT=65535 DPT=65535 " */
 119                 sb_add(m, "SPT=%u DPT=%u ",
 120                        ntohs(th->source), ntohs(th->dest));
 121                 /* Max length: 30 "SEQ=4294967295 ACK=4294967295 " */
 122                 if (logflags & IPT_LOG_TCPSEQ)
 123                         sb_add(m, "SEQ=%u ACK=%u ",
 124                                ntohl(th->seq), ntohl(th->ack_seq));
 125                 /* Max length: 13 "WINDOW=65535 " */
 126                 sb_add(m, "WINDOW=%u ", ntohs(th->window));
 127                 /* Max length: 9 "RES=0x3F " */
 128                 sb_add(m, "RES=0x%02x ", (u8)(ntohl(tcp_flag_word(th) & TCP_RESERVED_BITS) >> 22));
 129                 /* Max length: 32 "CWR ECE URG ACK PSH RST SYN FIN " */
 130                 if (th->cwr)
 131                         sb_add(m, "CWR ");
 132                 if (th->ece)
 133                         sb_add(m, "ECE ");
 134                 if (th->urg)
 135                         sb_add(m, "URG ");
 136                 if (th->ack)
 137                         sb_add(m, "ACK ");
 138                 if (th->psh)
 139                         sb_add(m, "PSH ");
 140                 if (th->rst)
 141                         sb_add(m, "RST ");
 142                 if (th->syn)
 143                         sb_add(m, "SYN ");
 144                 if (th->fin)
 145                         sb_add(m, "FIN ");
 146                 /* Max length: 11 "URGP=65535 " */
 147                 sb_add(m, "URGP=%u ", ntohs(th->urg_ptr));
 148
 149                 if ((logflags & IPT_LOG_TCPOPT) &&
 150                     th->doff * 4 > sizeof(struct tcphdr)) {
 151                         unsigned char _opt[4 * 15 - sizeof(struct tcphdr)];
 152                         const unsigned char *op;
 153                         unsigned int i, optsize;
 154
 155                         optsize = th->doff * 4 - sizeof(struct tcphdr);
 156                         op = skb_header_pointer(skb,
 157                                                 iphoff+ih->ihl*4+sizeof(_tcph),
 158                                                 optsize, _opt);
 159                         if (op == NULL) {
 160                                 sb_add(m, "TRUNCATED");
 161                                 return;
 162                         }
 163
 164                         /* Max length: 127 "OPT (" 15*4*2chars ") " */
 165                         sb_add(m, "OPT (");
 166                         for (i = 0; i < optsize; i++)
 167                                 sb_add(m, "%02X", op[i]);
 168                         sb_add(m, ") ");
 169                 }
 170                 break;
 171         }
 172         case IPPROTO_UDP:
 173         case IPPROTO_UDPLITE: {
 174                 struct udphdr _udph;
 175                 const struct udphdr *uh;
 176
 177                 if (ih->protocol == IPPROTO_UDP)
 178                         /* Max length: 10 "PROTO=UDP "     */
 179                         sb_add(m, "PROTO=UDP " );
 180                 else    /* Max length: 14 "PROTO=UDPLITE " */
 181                         sb_add(m, "PROTO=UDPLITE ");
 182
 183                 if (ntohs(ih->frag_off) & IP_OFFSET)
 184                         break;
 185
 186                 /* Max length: 25 "INCOMPLETE [65535 bytes] " */
 187                 uh = skb_header_pointer(skb, iphoff+ih->ihl*4,
 188                                         sizeof(_udph), &_udph);
 189                 if (uh == NULL) {
 190                         sb_add(m, "INCOMPLETE [%u bytes] ",
 191                                skb->len - iphoff - ih->ihl*4);
 192                         break;
 193                 }
 194
 195                 /* Max length: 20 "SPT=65535 DPT=65535 " */
 196                 sb_add(m, "SPT=%u DPT=%u LEN=%u ",
 197                        ntohs(uh->source), ntohs(uh->dest),
 198                        ntohs(uh->len));
 199                 break;
 200         }
 201         case IPPROTO_ICMP: {
 202                 struct icmphdr _icmph;
 203                 const struct icmphdr *ich;
 204                 static const size_t required_len[NR_ICMP_TYPES+1]
 205                         = { [ICMP_ECHOREPLY] = 4,
 206                             [ICMP_DEST_UNREACH]
 207                             = 8 + sizeof(struct iphdr),
 208                             [ICMP_SOURCE_QUENCH]
 209                             = 8 + sizeof(struct iphdr),
 210                             [ICMP_REDIRECT]
 211                             = 8 + sizeof(struct iphdr),
 212                             [ICMP_ECHO] = 4,
 213                             [ICMP_TIME_EXCEEDED]
 214                             = 8 + sizeof(struct iphdr),
 215                             [ICMP_PARAMETERPROB]
 216                             = 8 + sizeof(struct iphdr),
 217                             [ICMP_TIMESTAMP] = 20,
 218                             [ICMP_TIMESTAMPREPLY] = 20,
 219                             [ICMP_ADDRESS] = 12,
 220                             [ICMP_ADDRESSREPLY] = 12 };
 221
 222                 /* Max length: 11 "PROTO=ICMP " */
 223                 sb_add(m, "PROTO=ICMP ");
 224
 225                 if (ntohs(ih->frag_off) & IP_OFFSET)
 226                         break;
 227
 228                 /* Max length: 25 "INCOMPLETE [65535 bytes] " */
 229                 ich = skb_header_pointer(skb, iphoff + ih->ihl * 4,
 230                                          sizeof(_icmph), &_icmph);
 231                 if (ich == NULL) {
 232                         sb_add(m, "INCOMPLETE [%u bytes] ",
 233                                skb->len - iphoff - ih->ihl*4);
 234                         break;
 235                 }
 236
 237                 /* Max length: 18 "TYPE=255 CODE=255 " */
 238                 sb_add(m, "TYPE=%u CODE=%u ", ich->type, ich->code);
 239
 240                 /* Max length: 25 "INCOMPLETE [65535 bytes] " */
 241                 if (ich->type <= NR_ICMP_TYPES &&
 242                     required_len[ich->type] &&
 243                     skb->len-iphoff-ih->ihl*4 < required_len[ich->type]) {
 244                         sb_add(m, "INCOMPLETE [%u bytes] ",
 245                                skb->len - iphoff - ih->ihl*4);
 246                         break;
 247                 }
 248
 249                 switch (ich->type) {
 250                 case ICMP_ECHOREPLY:
 251                 case ICMP_ECHO:
 252                         /* Max length: 19 "ID=65535 SEQ=65535 " */
 253                         sb_add(m, "ID=%u SEQ=%u ",
 254                                ntohs(ich->un.echo.id),
 255                                ntohs(ich->un.echo.sequence));
 256                         break;
 257
 258                 case ICMP_PARAMETERPROB:
 259                         /* Max length: 14 "PARAMETER=255 " */
 260                         sb_add(m, "PARAMETER=%u ",
 261                                ntohl(ich->un.gateway) >> 24);
 262                         break;
 263                 case ICMP_REDIRECT:
 264                         /* Max length: 24 "GATEWAY=255.255.255.255 " */
 265                         sb_add(m, "GATEWAY=%pI4 ", &ich->un.gateway);
 266                         /* Fall through */
 267                 case ICMP_DEST_UNREACH:
 268                 case ICMP_SOURCE_QUENCH:
 269                 case ICMP_TIME_EXCEEDED:
 270                         /* Max length: 3+maxlen */
 271                         if (!iphoff) { /* Only recurse once. */
 272                                 sb_add(m, "[");
 273                                 dump_packet(m, info, skb,
 274                                             iphoff + ih->ihl*4+sizeof(_icmph));
 275                                 sb_add(m, "] ");
 276                         }
 277
 278                         /* Max length: 10 "MTU=65535 " */
 279                         if (ich->type == ICMP_DEST_UNREACH &&
 280                             ich->code == ICMP_FRAG_NEEDED)
 281                                 sb_add(m, "MTU=%u ", ntohs(ich->un.frag.mtu));
 282                 }
 283                 break;
 284         }
 285         /* Max Length */
 286         case IPPROTO_AH: {
 287                 struct ip_auth_hdr _ahdr;
 288                 const struct ip_auth_hdr *ah;
 289
 290                 if (ntohs(ih->frag_off) & IP_OFFSET)
 291                         break;
 292
 293                 /* Max length: 9 "PROTO=AH " */
 294                 sb_add(m, "PROTO=AH ");
 295
 296                 /* Max length: 25 "INCOMPLETE [65535 bytes] " */
 297                 ah = skb_header_pointer(skb, iphoff+ih->ihl*4,
 298                                         sizeof(_ahdr), &_ahdr);
 299                 if (ah == NULL) {
 300                         sb_add(m, "INCOMPLETE [%u bytes] ",
 301                                skb->len - iphoff - ih->ihl*4);
 302                         break;
 303                 }
 304
 305                 /* Length: 15 "SPI=0xF1234567 " */
 306                 sb_add(m, "SPI=0x%x ", ntohl(ah->spi));
 307                 break;
 308         }
 309         case IPPROTO_ESP: {
 310                 struct ip_esp_hdr _esph;
 311                 const struct ip_esp_hdr *eh;
 312
 313                 /* Max length: 10 "PROTO=ESP " */
 314                 sb_add(m, "PROTO=ESP ");
 315
 316                 if (ntohs(ih->frag_off) & IP_OFFSET)
 317                         break;
 318
 319                 /* Max length: 25 "INCOMPLETE [65535 bytes] " */
 320                 eh = skb_header_pointer(skb, iphoff+ih->ihl*4,
 321                                         sizeof(_esph), &_esph);
 322                 if (eh == NULL) {
 323                         sb_add(m, "INCOMPLETE [%u bytes] ",
 324                                skb->len - iphoff - ih->ihl*4);
 325                         break;
 326                 }
 327
 328                 /* Length: 15 "SPI=0xF1234567 " */
 329                 sb_add(m, "SPI=0x%x ", ntohl(eh->spi));
 330                 break;
 331         }
 332         /* Max length: 10 "PROTO 255 " */
 333         default:
 334                 sb_add(m, "PROTO=%u ", ih->protocol);
 335         }
 336
 337         /* Max length: 15 "UID=4294967295 " */
 338         if ((logflags & IPT_LOG_UID) && !iphoff && skb->sk) {
 339                 read_lock_bh(&skb->sk->sk_callback_lock);
 340                 if (skb->sk->sk_socket && skb->sk->sk_socket->file)
 341                         sb_add(m, "UID=%u GID=%u ",
 342                                 skb->sk->sk_socket->file->f_cred->fsuid,
 343                                 skb->sk->sk_socket->file->f_cred->fsgid);
 344                 read_unlock_bh(&skb->sk->sk_callback_lock);
 345         }
 346
 347         /* Max length: 16 "MARK=0xFFFFFFFF " */
 348         if (!iphoff && skb->mark)
 349                 sb_add(m, "MARK=0x%x ", skb->mark);
 350
 351         /* Proto    Max log string length */
 352         /* IP:      40+46+6+11+127 = 230 */
 353         /* TCP:     10+max(25,20+30+13+9+32+11+127) = 252 */
 354         /* UDP:     10+max(25,20) = 35 */
 355         /* UDPLITE: 14+max(25,20) = 39 */
 356         /* ICMP:    11+max(25, 18+25+max(19,14,24+3+n+10,3+n+10)) = 91+n */
 357         /* ESP:     10+max(25)+15 = 50 */
 358         /* AH:      9+max(25)+15 = 49 */
 359         /* unknown: 10 */
 360
 361         /* (ICMP allows recursion one level deep) */
 362         /* maxlen =  IP + ICMP +  IP + max(TCP,UDP,ICMP,unknown) */
 363         /* maxlen = 230+   91  + 230 + 252 = 803 */
 364 }
 365
 366 static void dump_mac_header(struct sbuff *m,
 367                             const struct nf_loginfo *info,
 368                             const struct sk_buff *skb)
 369 {
 370         struct net_device *dev = skb->dev;
 371         unsigned int logflags = 0;
 372
 373         if (info->type == NF_LOG_TYPE_LOG)
 374                 logflags = info->u.log.logflags;
 375
 376         if (!(logflags & IPT_LOG_MACDECODE))
 377                 goto fallback;
 378
 379         switch (dev->type) {
 380         case ARPHRD_ETHER:
 381                 sb_add(m, "MACSRC=%pM MACDST=%pM MACPROTO=%04x ",
 382                        eth_hdr(skb)->h_source, eth_hdr(skb)->h_dest,
 383                        ntohs(eth_hdr(skb)->h_proto));
 384                 return;
 385         default:
 386                 break;
 387         }
 388
 389 fallback:
 390         sb_add(m, "MAC=");
 391         if (dev->hard_header_len &&
 392             skb->mac_header != skb->network_header) {
 393                 const unsigned char *p = skb_mac_header(skb);
 394                 unsigned int i;
 395
 396                 sb_add(m, "%02x", *p++);
 397                 for (i = 1; i < dev->hard_header_len; i++, p++)
 398                         sb_add(m, ":%02x", *p);
 399         }
 400         sb_add(m, " ");
 401 }
 402
 403 static struct nf_loginfo default_loginfo = {
 404         .type   = NF_LOG_TYPE_LOG,
 405         .u = {
 406                 .log = {
 407                         .level    = 5,
 408                         .logflags = NF_LOG_MASK,
 409                 },
 410         },
 411 };
 412
 413 static void
 414 ipt_log_packet(u_int8_t pf,
 415                unsigned int hooknum,
 416                const struct sk_buff *skb,
 417                const struct net_device *in,
 418                const struct net_device *out,
 419                const struct nf_loginfo *loginfo,
 420                const char *prefix)
 421 {
 422         struct sbuff *m = sb_open();
 423
 424         if (!loginfo)
 425                 loginfo = &default_loginfo;
 426
 427         sb_add(m, "<%d>%sIN=%s OUT=%s ", loginfo->u.log.level,
 428                prefix,
 429                in ? in->name : "",
 430                out ? out->name : "");
 431 #ifdef CONFIG_BRIDGE_NETFILTER
 432         if (skb->nf_bridge) {
 433                 const struct net_device *physindev;
 434                 const struct net_device *physoutdev;
 435
 436                 physindev = skb->nf_bridge->physindev;
 437                 if (physindev && in != physindev)
 438                         sb_add(m, "PHYSIN=%s ", physindev->name);
 439                 physoutdev = skb->nf_bridge->physoutdev;
 440                 if (physoutdev && out != physoutdev)
 441                         sb_add(m, "PHYSOUT=%s ", physoutdev->name);
 442         }
 443 #endif
 444
 445         if (in != NULL)
 446                 dump_mac_header(m, loginfo, skb);
 447
 448         dump_packet(m, loginfo, skb, 0);
 449
 450         sb_close(m);
 451 }
 452
 453 static unsigned int
 454 log_tg(struct sk_buff *skb, const struct xt_action_param *par)
 455 {
 456         const struct ipt_log_info *loginfo = par->targinfo;
 457         struct nf_loginfo li;
 458
 459         li.type = NF_LOG_TYPE_LOG;
 460         li.u.log.level = loginfo->level;
 461         li.u.log.logflags = loginfo->logflags;
 462
 463         ipt_log_packet(NFPROTO_IPV4, par->hooknum, skb, par->in, par->out, &li,
 464                        loginfo->prefix);
 465         return XT_CONTINUE;
 466 }
 467
 468 static int log_tg_check(const struct xt_tgchk_param *par)
 469 {
 470         const struct ipt_log_info *loginfo = par->targinfo;
 471
 472         if (loginfo->level >= 8) {
 473                 pr_debug("level %u >= 8\n", loginfo->level);
 474                 return -EINVAL;
 475         }
 476         if (loginfo->prefix[sizeof(loginfo->prefix)-1] != '\0') {
 477                 pr_debug("prefix is not null-terminated\n");
 478                 return -EINVAL;
 479         }
 480         return 0;
 481 }
 482
 483 static struct xt_target log_tg_reg __read_mostly = {
 484         .name           = "LOG",
 485         .family         = NFPROTO_IPV4,
 486         .target         = log_tg,
 487         .targetsize     = sizeof(struct ipt_log_info),
 488         .checkentry     = log_tg_check,
 489         .me             = THIS_MODULE,
 490 };
 491
 492 static struct nf_logger ipt_log_logger __read_mostly = {
 493         .name           = "ipt_LOG",
 494         .logfn          = &ipt_log_packet,
 495         .me             = THIS_MODULE,
 496 };
 497
 498 static int __init log_tg_init(void)
 499 {
 500         int ret;
 501
 502         ret = xt_register_target(&log_tg_reg);
 503         if (ret < 0)
 504                 return ret;
 505         nf_log_register(NFPROTO_IPV4, &ipt_log_logger);
 506         return 0;
 507 }
 508
 509 static void __exit log_tg_exit(void)
 510 {
 511         nf_log_unregister(&ipt_log_logger);
 512         xt_unregister_target(&log_tg_reg);
 513 }
 514
 515 module_init(log_tg_init);
 516 module_exit(log_tg_exit);