libnet/src/libnet_build_gre.c

   1 /*
   2  *  libnet
   3  *  libnet_build_gre.c - GRE packet assembler
   4  *
   5  *  Copyright (c) 2003 Frédéric Raynal <pappy@security-labs.org>
   6  *  All rights reserved.
   7  *
   8  * Redistribution and use in source and binary forms, with or without
   9  * modification, are permitted provided that the following conditions
  10  * are met:
  11  * 1. Redistributions of source code must retain the above copyright
  12  *    notice, this list of conditions and the following disclaimer.
  13  * 2. Redistributions in binary form must reproduce the above copyright
  14  *    notice, this list of conditions and the following disclaimer in the
  15  *    documentation and/or other materials provided with the distribution.
  16  *
  17  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
  18  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  19  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  20  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
  21  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  22  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  23  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  24  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  25  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  26  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  27  * SUCH DAMAGE.
  28  *
  29  */
  30
  31 #if (HAVE_CONFIG_H)
  32 #include "../include/config.h"
  33 #endif
  34 #if (!(_WIN32) || (__CYGWIN__))
  35 #include "../include/libnet.h"
  36 #else
  37 #include "../include/win32/libnet.h"
  38 #endif
  39
  40 /*
  41  * Overall packet
  42  *
  43  *  The entire encapsulated packet would then have the form:
  44  *
  45  *                  ---------------------------------
  46  *                  |                               |
  47  *                  |       Delivery Header         |
  48  *                  |                               |
  49  *                  ---------------------------------
  50  *                  |                               |
  51  *                  |       GRE Header              |
  52  *                  |                               |
  53  *                  ---------------------------------
  54  *                  |                               |
  55  *                  |       Payload packet          |
  56  *                  |                               |
  57  *                  ---------------------------------
  58  *
  59  * RFC 1701 defines a header.
  60  * A new RFC (2784) has changed the header and proposed to remove the key
  61  * and seqnum.
  62  * A newer RFC (2890) has changed the header proposed in RFC 2784 by putting
  63  * back key and seqnum.
  64  * These will be supported the day IETF'guys stop this mess !
  65  *
  66  *   FR
  67  */
  68
  69
  70 /*
  71  * Generic Routing Encapsulation (GRE)
  72  * RFC 1701 http://www.faqs.org/rfcs/rfc1701.html
  73  *
  74  *
  75  * Packet header
  76  *
  77  *   The GRE packet header has the form:
  78  *
  79  *       0                   1                   2                   3
  80  *       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
  81  *      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  82  *      |C|R|K|S|s|Recur|  Flags  | Ver |         Protocol Type         |
  83  *      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  84  *      |      Checksum (optional)      |       Offset (optional)       |
  85  *      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  86  *      |                         Key (optional)                        |
  87  *      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  88  *      |                    Sequence Number (optional)                 |
  89  *      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  90  *      |                         Routing (optional)                    |
  91  *      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  92  *
  93  * Enhanced GRE header
  94  *
  95  *   See rfc 2637 for details. It is used for PPTP tunneling.
  96  *
  97  *          0                   1                   2                   3
  98  *          0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
  99  *         +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 100  *         |C|R|K|S|s|Recur|A| Flags | Ver |         Protocol Type         |
 101  *         +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 102  *         |    Key (HW) Payload Length    |       Key (LW) Call ID        |
 103  *         +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 104  *         |                  Sequence Number (Optional)                   |
 105  *         +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 106  *         |               Acknowledgment Number (Optional)                |
 107  *         +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 108  *
 109  */
 110
 111 static inline void
 112 __libnet_print_gre_flags_ver(u_int16_t fv)
 113 {
 114     printf("version = %d (%d) -> ",
 115         fv & GRE_VERSION_MASK, libnet_getgre_length(fv));
 116     if (fv & GRE_CSUM)
 117     {
 118         printf("CSUM ");
 119     }
 120     if (fv & GRE_ROUTING)
 121     {
 122         printf("ROUTING ");
 123     }
 124     if (fv & GRE_KEY)
 125     {
 126         printf("KEY ");
 127     }
 128     if (fv & GRE_SEQ)
 129     {
 130         printf("SEQ ");
 131     }
 132     if (fv & GRE_ACK)
 133     {
 134         printf("ACK ");
 135     }
 136     printf("\n");
 137 }
 138
 139
 140 /* FIXME: what is the portability of the "((struct libnet_gre_hdr*)0)->" ? */
 141 inline u_int32_t
 142 libnet_getgre_length(u_int16_t fv)
 143 {
 144
 145     u_int32_t n = LIBNET_GRE_H;
 146     /*
 147      * If either the Checksum Present bit or the Routing Present bit are
 148      * set, BOTH the Checksum and Offset fields are present in the GRE
 149      * packet.
 150      */
 151
 152     if ((!(fv & GRE_VERSION_MASK) && (fv & (GRE_CSUM|GRE_ROUTING))) || /* v0 */
 153         (fv & GRE_VERSION_MASK) )                                      /* v1 */
 154     {
 155         n += sizeof( ((struct libnet_gre_hdr *)0)->gre_sum) +
 156             sizeof( ((struct libnet_gre_hdr *)0)->gre_offset);
 157     }
 158
 159     if ((!(fv & GRE_VERSION_MASK) && (fv & GRE_KEY)) ||                /* v0 */
 160         ( (fv & GRE_VERSION_MASK) && (fv & GRE_SEQ)) )                 /* v1 */
 161     {
 162         n += sizeof( ((struct libnet_gre_hdr *)0)->gre_key);
 163     }
 164
 165     if ((!(fv & GRE_VERSION_MASK) && (fv & GRE_SEQ)) ||                /* v0 */
 166         ( (fv & GRE_VERSION_MASK) && (fv & GRE_ACK)) )                 /* v1 */
 167     {
 168         n += sizeof( ((struct libnet_gre_hdr *)0)->gre_seq );
 169     }
 170
 171     return (n);
 172 }
 173
 174 libnet_ptag_t
 175 libnet_build_gre(u_int16_t fv, u_int16_t type, u_int16_t sum,
 176 u_int16_t offset, u_int32_t key, u_int32_t seq, u_int16_t len,
 177 u_int8_t *payload, u_int32_t payload_s, libnet_t *l, libnet_ptag_t ptag)
 178 {
 179     u_int32_t n;
 180     libnet_pblock_t *p;
 181     struct libnet_gre_hdr gre_hdr;
 182
 183     if (l == NULL)
 184     {
 185         return (-1);
 186     }
 187
 188     n = libnet_getgre_length(fv) + payload_s;
 189
 190     /*
 191      *  Find the existing protocol block if a ptag is specified, or create
 192      *  a new one.
 193      */
 194     p = libnet_pblock_probe(l, ptag, n, LIBNET_PBLOCK_GRE_H);
 195     if (p == NULL)
 196     {
 197         return (-1);
 198     }
 199
 200     gre_hdr.flags_ver = htons(fv);
 201     gre_hdr.type      = htons(type);
 202     n = libnet_pblock_append(l, p, (u_int8_t *)&gre_hdr, LIBNET_GRE_H);
 203     if (n == -1)
 204     {
 205         /* err msg set in libnet_pblock_append() */
 206         goto bad;
 207     }
 208
 209     if ((!(fv & GRE_VERSION_MASK) && (fv & (GRE_CSUM|GRE_ROUTING))) || /* v0 */
 210         (fv & GRE_VERSION_MASK))                                       /* v1 */
 211     {
 212         sum = htons(sum);
 213         n = libnet_pblock_append(l, p, (u_int8_t*)&sum,
 214                 sizeof(gre_hdr.gre_sum));
 215         if (n == -1)
 216         {
 217             /* err msg set in libnet_pblock_append() */
 218             goto bad;
 219         }
 220         offset = htons(offset);
 221         n = libnet_pblock_append(l, p, (u_int8_t*)&offset,
 222                 sizeof(gre_hdr.gre_offset));
 223         if (n == -1)
 224         {
 225             /* err msg set in libnet_pblock_append() */
 226             goto bad;
 227         }
 228     }
 229
 230     if ((!(fv & GRE_VERSION_MASK) && (fv & GRE_KEY)) ||                /* v0 */
 231         ( (fv & GRE_VERSION_MASK) && (fv & GRE_SEQ)) )                 /* v1 */
 232     {
 233         key = htonl(key);
 234         n = libnet_pblock_append(l, p, (u_int8_t*)&key,
 235                 sizeof(gre_hdr.gre_key));
 236         if (n == -1)
 237         {
 238             /* err msg set in libnet_pblock_append() */
 239             goto bad;
 240         }
 241     }
 242
 243     if ((!(fv & GRE_VERSION_MASK) && (fv & GRE_SEQ)) ||                /* v0 */
 244         ( (fv & GRE_VERSION_MASK) && (fv & GRE_ACK)) )                 /* v1 */
 245     {
 246         seq = htonl(seq);
 247         n = libnet_pblock_append(l, p, (u_int8_t*)&seq,
 248                 sizeof(gre_hdr.gre_seq));
 249         if (n == -1)
 250         {
 251             /* err msg set in libnet_pblock_append() */
 252             goto bad;
 253         }
 254     }
 255
 256     if ((payload && !payload_s) || (!payload && payload_s))
 257     {
 258         sprintf(l->err_buf, "%s(): payload inconsistency\n", __func__);
 259         goto bad;
 260     }
 261
 262     if (payload && payload_s)
 263     {
 264         n = libnet_pblock_append(l, p, payload, payload_s);
 265         if (n == -1)
 266         {
 267             /* err msg set in libnet_pblock_append() */
 268             goto bad;
 269         }
 270     }
 271
 272     if ( (fv & GRE_CSUM) && (!sum) )
 273     {
 274         libnet_pblock_setflags(p, LIBNET_PBLOCK_DO_CHECKSUM);
 275     }
 276
 277     return (ptag ? ptag : libnet_pblock_update(l, p, len, LIBNET_PBLOCK_GRE_H));
 278
 279 bad:
 280     libnet_pblock_delete(l, p);
 281     return (-1);
 282 }
 283
 284 libnet_ptag_t
 285 libnet_build_egre(u_int16_t fv, u_int16_t type, u_int16_t sum,
 286 u_int16_t offset, u_int32_t key, u_int32_t seq, u_int16_t len,
 287 u_int8_t *payload, u_int32_t payload_s, libnet_t *l, libnet_ptag_t ptag)
 288 {
 289     return (libnet_build_gre(fv, type, sum, offset, key, seq, len,
 290            payload, payload_s, l, ptag));
 291 }
 292
 293 /*
 294  *    Routing (variable)
 295  *
 296  *      The Routing field is optional and is present only if the Routing
 297  *      Present bit is set to 1.
 298  *
 299  *      The Routing field is a list of Source Route Entries (SREs).  Each
 300  *      SRE has the form:
 301  *
 302  *    0                   1                   2                   3
 303  *    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 304  *   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 305  *   |       Address Family          |  SRE Offset   |  SRE Length   |
 306  *   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 307  *   |                        Routing Information ...
 308  *   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 309  *
 310  */
 311 libnet_ptag_t
 312 libnet_build_gre_sre(u_int16_t af, u_int8_t offset, u_int8_t length,
 313 u_int8_t *routing, u_int8_t *payload, u_int32_t payload_s, libnet_t *l,
 314 libnet_ptag_t ptag)
 315 {
 316     u_int32_t n;
 317     libnet_pblock_t *p;
 318     struct libnet_gre_sre_hdr sre_hdr;
 319
 320     if (l == NULL)
 321     {
 322         return (-1);
 323     }
 324
 325     n = LIBNET_GRE_SRE_H + length + payload_s;
 326
 327     /*
 328      *  Find the existing protocol block if a ptag is specified, or create
 329      *  a new one.
 330      */
 331     p = libnet_pblock_probe(l, ptag, n, LIBNET_PBLOCK_GRE_SRE_H);
 332     if (p == NULL)
 333     {
 334         return (-1);
 335     }
 336     sre_hdr.af = htons(af);
 337     sre_hdr.sre_offset = offset;
 338     sre_hdr.sre_length = length;
 339     n = libnet_pblock_append(l, p, (u_int8_t *)&sre_hdr, LIBNET_GRE_SRE_H);
 340     if (n == -1)
 341     {
 342         /* err msg set in libnet_pblock_append() */
 343         goto bad;
 344     }
 345
 346     if ((routing && !length) || (!routing && length))
 347     {
 348         sprintf(l->err_buf, "%s(): routing inconsistency\n", __func__);
 349         goto bad;
 350     }
 351
 352     if (routing && length)
 353     {
 354         n = libnet_pblock_append(l, p, routing, length);
 355         if (n == -1)
 356         {
 357             /* err msg set in libnet_pblock_append() */
 358             goto bad;
 359         }
 360     }
 361
 362     if ((payload && !payload_s) || (!payload && payload_s))
 363     {
 364         sprintf(l->err_buf, "%s(): payload inconsistency\n", __func__);
 365         goto bad;
 366     }
 367
 368     if (payload && payload_s)
 369     {
 370         n = libnet_pblock_append(l, p, payload, payload_s);
 371         if (n == -1)
 372         {
 373             /* err msg set in libnet_pblock_append() */
 374             goto bad;
 375         }
 376     }
 377
 378     return (ptag ? ptag : libnet_pblock_update(l, p, 0,
 379            LIBNET_PBLOCK_GRE_SRE_H));
 380
 381 bad:
 382     libnet_pblock_delete(l, p);
 383     return (-1);
 384
 385 }
 386
 387 libnet_ptag_t
 388 libnet_build_gre_last_sre(libnet_t *l, libnet_ptag_t ptag)
 389 {
 390     u_int32_t n, zero = 0;
 391     libnet_pblock_t *p;
 392
 393     if (l == NULL)
 394     {
 395         return (-1);
 396     }
 397
 398     n = LIBNET_GRE_SRE_H;
 399
 400     /*
 401      *  Find the existing protocol block if a ptag is specified, or create
 402      *  a new one.
 403      */
 404     p = libnet_pblock_probe(l, ptag, n, LIBNET_PBLOCK_GRE_H);
 405     if (p == NULL)
 406     {
 407         return (-1);
 408     }
 409
 410     n = libnet_pblock_append(l, p, (u_int8_t *)&zero, LIBNET_GRE_SRE_H);
 411     if (n == -1)
 412     {
 413         /* err msg set in libnet_pblock_append() */
 414         goto bad;
 415     }
 416
 417     return (ptag ? ptag : libnet_pblock_update(l, p, 0,
 418            LIBNET_PBLOCK_GRE_SRE_H));
 419
 420 bad:
 421     libnet_pblock_delete(l, p);
 422     return (-1);
 423
 424 }
 425
 426
 427 /* EOF */