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