net/ipv4/ip_masq_irc.c

   1 /*
   2  *              IP_MASQ_IRC irc masquerading module
   3  *
   4  *
   5  * Version:     @(#)ip_masq_irc.c 0.03   97/11/30
   6  *
   7  * Author:      Juan Jose Ciarlante
   8  *
   9  * Additions:
  10  *  - recognize a few non-irc-II DCC requests (Oliver Wagner)
  11  *     DCC MOVE (AmIRC/DCC.MOVE; SEND with resuming)
  12  *     DCC SCHAT (AmIRC IDEA encrypted CHAT)
  13  *     DCC TSEND (AmIRC/PIRCH SEND without ACKs)
  14  * Fixes:
  15  *      Juan Jose Ciarlante     :  set NO_DADDR flag in ip_masq_new()
  16  *      Nigel Metheringham      :  Added multiple port support
  17  *      Juan Jose Ciarlante     :  litl bits for 2.1
  18  *      Oliver Wagner           :  more IRC cmds processing
  19  *        <winmute@lucifer.gv.kotnet.org>
  20  *      Juan Jose Ciarlante     :  put new ms entry to listen()
  21  *
  22  * FIXME:
  23  *      - detect also previous "PRIVMSG" string ?.
  24  *
  25  *      This program is free software; you can redistribute it and/or
  26  *      modify it under the terms of the GNU General Public License
  27  *      as published by the Free Software Foundation; either version
  28  *      2 of the License, or (at your option) any later version.
  29  *
  30  * Multiple Port Support
  31  *      The helper can be made to handle up to MAX_MASQ_APP_PORTS (normally 12)
  32  *      with the port numbers being defined at module load time.  The module
  33  *      uses the symbol "ports" to define a list of monitored ports, which can
  34  *      be specified on the insmod command line as
  35  *              ports=x1,x2,x3...
  36  *      where x[n] are integer port numbers.  This option can be put into
  37  *      /etc/conf.modules (or /etc/modules.conf depending on your config)
  38  *      where modload will pick it up should you use modload to load your
  39  *      modules.
  40  *
  41  */
  42
  43 #include <linux/config.h>
  44 #include <linux/module.h>
  45
  46 #include <linux/types.h>
  47 #include <linux/kernel.h>
  48 #include <asm/system.h>
  49 #include <linux/skbuff.h>
  50 #include <linux/in.h>
  51 #include <linux/ip.h>
  52 #include <linux/init.h>
  53 #include <net/protocol.h>
  54 #include <net/tcp.h>
  55 #include <net/ip_masq.h>
  56
  57
  58 /*
  59  * List of ports (up to MAX_MASQ_APP_PORTS) to be handled by helper
  60  * First port is set to the default port.
  61  */
  62 int ports[MAX_MASQ_APP_PORTS] = {6667}; /* I rely on the trailing items being set to zero */
  63 struct ip_masq_app *masq_incarnations[MAX_MASQ_APP_PORTS];
  64 /*
  65  *      Debug level
  66  */
  67 #ifdef CONFIG_IP_MASQ_DEBUG
  68 static int debug=0;
  69 MODULE_PARM(debug, "i");
  70 #endif
  71
  72 MODULE_PARM(ports, "1-" __MODULE_STRING(MAX_MASQ_APP_PORTS) "i");
  73
  74
  75 /*
  76  * List of supported DCC protocols
  77  */
  78
  79 #define NUM_DCCPROTO 5
  80
  81 struct dccproto
  82 {
  83   char *match;
  84   int matchlen;
  85   int xtra_args;
  86 };
  87
  88 struct dccproto dccprotos[NUM_DCCPROTO] = {
  89  { "SEND ", 5, 1 },
  90  { "CHAT ", 5, 0, },
  91  { "MOVE ", 5, 1 },
  92  { "TSEND ", 6, 1, },
  93  { "SCHAT ", 6, 0, }
  94 };
  95 #define MAXMATCHLEN 6
  96
  97 static int
  98 masq_irc_init_1 (struct ip_masq_app *mapp, struct ip_masq *ms)
  99 {
 100         MOD_INC_USE_COUNT;
 101         return 0;
 102 }
 103
 104 static int
 105 masq_irc_done_1 (struct ip_masq_app *mapp, struct ip_masq *ms)
 106 {
 107         MOD_DEC_USE_COUNT;
 108         return 0;
 109 }
 110
 111 int
 112 masq_irc_out (struct ip_masq_app *mapp, struct ip_masq *ms, struct sk_buff **skb_p, __u32 maddr)
 113 {
 114         struct sk_buff *skb;
 115         struct iphdr *iph;
 116         struct tcphdr *th;
 117         char *data, *data_limit;
 118         __u32 s_addr;
 119         __u16 s_port;
 120         struct ip_masq *n_ms;
 121         char buf[20];           /* "m_addr m_port" (dec base)*/
 122         unsigned buf_len;
 123         int diff;
 124         int xtra_args = 0;      /* extra int args wanted after addr */
 125         char *dcc_p, *addr_beg_p, *addr_end_p;
 126
 127         skb = *skb_p;
 128         iph = skb->nh.iph;
 129         th = (struct tcphdr *)&(((char *)iph)[iph->ihl*4]);
 130         data = (char *)&th[1];
 131
 132         /*
 133          *      Hunt irc DCC string, the _shortest_:
 134          *
 135          *      strlen("DCC CHAT chat AAAAAAAA P\x01\n")=26
 136          *      strlen("DCC SCHAT chat AAAAAAAA P\x01\n")=27
 137          *      strlen("DCC SEND F AAAAAAAA P S\x01\n")=25
 138          *      strlen("DCC MOVE F AAAAAAAA P S\x01\n")=25
 139          *      strlen("DCC TSEND F AAAAAAAA P S\x01\n")=26
 140          *      strlen("DCC MOVE F AAAAAAAA P S\x01\n")=25
 141          *              AAAAAAAAA: bound addr (1.0.0.0==16777216, min 8 digits)
 142          *              P:         bound port (min 1 d )
 143          *              F:         filename   (min 1 d )
 144          *              S:         size       (min 1 d )
 145          *              0x01, \n:  terminators
 146          */
 147
 148         data_limit = skb->h.raw + skb->len;
 149
 150         while (data < (data_limit - ( 21 + MAXMATCHLEN ) ) )
 151         {
 152                 int i;
 153                 if (memcmp(data,"DCC ",4))  {
 154                         data ++;
 155                         continue;
 156                 }
 157
 158                 dcc_p = data;
 159                 data += 4;     /* point to DCC cmd */
 160
 161                 for(i=0; i<NUM_DCCPROTO; i++)
 162                 {
 163                         /*
 164                          * go through the table and hunt a match string
 165                          */
 166
 167                         if( memcmp(data, dccprotos[i].match, dccprotos[i].matchlen ) == 0 )
 168                         {
 169                                 xtra_args = dccprotos[i].xtra_args;
 170                                 data += dccprotos[i].matchlen;
 171
 172                                 /*
 173                                  *      skip next string.
 174                                  */
 175
 176                                 while( *data++ != ' ')
 177
 178                                         /*
 179                                          *      must still parse, at least, "AAAAAAAA P\x01\n",
 180                                          *      12 bytes left.
 181                                          */
 182                                         if (data > (data_limit-12)) return 0;
 183
 184
 185                                 addr_beg_p = data;
 186
 187                                 /*
 188                                  *      client bound address in dec base
 189                                  */
 190
 191                                 s_addr = simple_strtoul(data,&data,10);
 192                                 if (*data++ !=' ')
 193                                         continue;
 194
 195                                 /*
 196                                  *      client bound port in dec base
 197                                  */
 198
 199                                 s_port = simple_strtoul(data,&data,10);
 200                                 addr_end_p = data;
 201
 202                                 /*
 203                                  *      should check args consistency?
 204                                  */
 205
 206                                 while(xtra_args) {
 207                                         if (*data != ' ')
 208                                                 break;
 209                                         data++;
 210                                         simple_strtoul(data,&data,10);
 211                                         xtra_args--;
 212                                 }
 213
 214                                 if (xtra_args != 0) continue;
 215
 216                                 /*
 217                                  *      terminators.
 218                                  */
 219
 220                                 if (data[0] != 0x01)
 221                                         continue;
 222                                 if (data[1]!='\r' && data[1]!='\n')
 223                                         continue;
 224
 225                                 /*
 226                                  *      Now create an masquerade entry for it
 227                                  *      must set NO_DPORT and NO_DADDR because
 228                                  *      connection is requested by another client.
 229                                  */
 230
 231                                 n_ms = ip_masq_new(IPPROTO_TCP,
 232                                                 maddr, 0,
 233                                                 htonl(s_addr),htons(s_port),
 234                                                 0, 0,
 235                                                 IP_MASQ_F_NO_DPORT|IP_MASQ_F_NO_DADDR);
 236                                 if (n_ms==NULL)
 237                                         return 0;
 238
 239                                 /*
 240                                  * Replace the old "address port" with the new one
 241                                  */
 242
 243                                 buf_len = sprintf(buf,"%lu %u",
 244                                                 ntohl(n_ms->maddr),ntohs(n_ms->mport));
 245
 246                                 /*
 247                                  * Calculate required delta-offset to keep TCP happy
 248                                  */
 249
 250                                 diff = buf_len - (addr_end_p-addr_beg_p);
 251
 252                                 *addr_beg_p = '\0';
 253                                 IP_MASQ_DEBUG(1-debug, "masq_irc_out(): '%s' %X:%X detected (diff=%d)\n", dcc_p, s_addr,s_port, diff);
 254
 255                                 /*
 256                                  *      No shift.
 257                                  */
 258
 259                                 if (diff==0) {
 260                                         /*
 261                                          * simple case, just copy.
 262                                          */
 263                                         memcpy(addr_beg_p,buf,buf_len);
 264                                 } else {
 265
 266                                         *skb_p = ip_masq_skb_replace(skb, GFP_ATOMIC,
 267                                                         addr_beg_p, addr_end_p-addr_beg_p,
 268                                                         buf, buf_len);
 269                                 }
 270                                 ip_masq_listen(n_ms);
 271                                 ip_masq_put(n_ms);
 272                                 return diff;
 273                         }
 274                 }
 275         }
 276         return 0;
 277
 278 }
 279
 280 /*
 281  *      Main irc object
 282  *      You need 1 object per port in case you need
 283  *      to offer also other used irc ports (6665,6666,etc),
 284  *      they will share methods but they need own space for
 285  *      data.
 286  */
 287
 288 struct ip_masq_app ip_masq_irc = {
 289         NULL,                   /* next */
 290         "irc",                  /* name */
 291         0,                      /* type */
 292         0,                      /* n_attach */
 293         masq_irc_init_1,        /* init_1 */
 294         masq_irc_done_1,        /* done_1 */
 295         masq_irc_out,           /* pkt_out */
 296         NULL                    /* pkt_in */
 297 };
 298
 299 /*
 300  *      ip_masq_irc initialization
 301  */
 302
 303 __initfunc(int ip_masq_irc_init(void))
 304 {
 305         int i, j;
 306
 307         for (i=0; (i<MAX_MASQ_APP_PORTS); i++) {
 308                 if (ports[i]) {
 309                         if ((masq_incarnations[i] = kmalloc(sizeof(struct ip_masq_app),
 310                                                             GFP_KERNEL)) == NULL)
 311                                 return -ENOMEM;
 312                         memcpy(masq_incarnations[i], &ip_masq_irc, sizeof(struct ip_masq_app));
 313                         if ((j = register_ip_masq_app(masq_incarnations[i],
 314                                                       IPPROTO_TCP,
 315                                                       ports[i]))) {
 316                                 return j;
 317                         }
 318                         IP_MASQ_DEBUG(1-debug,
 319                                         "Irc: loaded support on port[%d] = %d\n",
 320                                i, ports[i]);
 321                 } else {
 322                         /* To be safe, force the incarnation table entry to NULL */
 323                         masq_incarnations[i] = NULL;
 324                 }
 325         }
 326         return 0;
 327 }
 328
 329 /*
 330  *      ip_masq_irc fin.
 331  */
 332
 333 int ip_masq_irc_done(void)
 334 {
 335         int i, j, k;
 336
 337         k=0;
 338         for (i=0; (i<MAX_MASQ_APP_PORTS); i++) {
 339                 if (masq_incarnations[i]) {
 340                         if ((j = unregister_ip_masq_app(masq_incarnations[i]))) {
 341                                 k = j;
 342                         } else {
 343                                 kfree(masq_incarnations[i]);
 344                                 masq_incarnations[i] = NULL;
 345                                 IP_MASQ_DEBUG(1-debug, "Irc: unloaded support on port[%d] = %d\n",
 346                                        i, ports[i]);
 347                         }
 348                 }
 349         }
 350         return k;
 351 }
 352
 353
 354 #ifdef MODULE
 355 EXPORT_NO_SYMBOLS;
 356
 357 int init_module(void)
 358 {
 359         if (ip_masq_irc_init() != 0)
 360                 return -EIO;
 361         return 0;
 362 }
 363
 364 void cleanup_module(void)
 365 {
 366         if (ip_masq_irc_done() != 0)
 367                 printk(KERN_INFO "ip_masq_irc: can't remove module");
 368 }
 369
 370 #endif /* MODULE */