src/libipsec/esp_packet.c

   1 /*
   2  * Copyright (C) 2012-2013 Tobias Brunner
   3  * Copyright (C) 2012 Giuliano Grassi
   4  * Copyright (C) 2012 Ralf Sager
   5  * Hochschule fuer Technik Rapperswil
   6  *
   7  * This program is free software; you can redistribute it and/or modify it
   8  * under the terms of the GNU General Public License as published by the
   9  * Free Software Foundation; either version 2 of the License, or (at your
  10  * option) any later version.  See <http://www.fsf.org/copyleft/gpl.txt>.
  11  *
  12  * This program is distributed in the hope that it will be useful, but
  13  * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
  14  * or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  15  * for more details.
  16  */
  17
  18
  19 #include "esp_packet.h"
  20
  21 #include <library.h>
  22 #include <utils/debug.h>
  23 #include <crypto/crypters/crypter.h>
  24 #include <crypto/signers/signer.h>
  25 #include <bio/bio_reader.h>
  26 #include <bio/bio_writer.h>
  27
  28 #include <netinet/in.h>
  29
  30 typedef struct private_esp_packet_t private_esp_packet_t;
  31
  32 /**
  33  * Private additions to esp_packet_t.
  34  */
  35 struct private_esp_packet_t {
  36
  37         /**
  38          * Public members
  39          */
  40         esp_packet_t public;
  41
  42         /**
  43          * Raw ESP packet
  44          */
  45         packet_t *packet;
  46
  47         /**
  48          * Payload of this packet
  49          */
  50         ip_packet_t *payload;
  51
  52         /**
  53          * Next Header info (e.g. IPPROTO_IPIP)
  54          */
  55         u_int8_t next_header;
  56
  57 };
  58
  59 /**
  60  * Forward declaration for clone()
  61  */
  62 static private_esp_packet_t *esp_packet_create_internal(packet_t *packet);
  63
  64 METHOD(packet_t, set_source, void,
  65         private_esp_packet_t *this, host_t *src)
  66 {
  67         return this->packet->set_source(this->packet, src);
  68 }
  69
  70 METHOD2(esp_packet_t, packet_t, get_source, host_t*,
  71         private_esp_packet_t *this)
  72 {
  73         return this->packet->get_source(this->packet);
  74 }
  75
  76 METHOD(packet_t, set_destination, void,
  77         private_esp_packet_t *this, host_t *dst)
  78 {
  79         return this->packet->set_destination(this->packet, dst);
  80 }
  81
  82 METHOD2(esp_packet_t, packet_t, get_destination, host_t*,
  83         private_esp_packet_t *this)
  84 {
  85         return this->packet->get_destination(this->packet);
  86 }
  87
  88 METHOD(packet_t, get_data, chunk_t,
  89         private_esp_packet_t *this)
  90 {
  91         return this->packet->get_data(this->packet);
  92 }
  93
  94 METHOD(packet_t, set_data, void,
  95         private_esp_packet_t *this, chunk_t data)
  96 {
  97         return this->packet->set_data(this->packet, data);
  98 }
  99
 100 METHOD(packet_t, get_dscp, u_int8_t,
 101         private_esp_packet_t *this)
 102 {
 103         return this->packet->get_dscp(this->packet);
 104 }
 105
 106 METHOD(packet_t, set_dscp, void,
 107         private_esp_packet_t *this, u_int8_t value)
 108 {
 109         this->packet->set_dscp(this->packet, value);
 110 }
 111
 112 METHOD(packet_t, skip_bytes, void,
 113         private_esp_packet_t *this, size_t bytes)
 114 {
 115         return this->packet->skip_bytes(this->packet, bytes);
 116 }
 117
 118 METHOD(packet_t, clone, packet_t*,
 119         private_esp_packet_t *this)
 120 {
 121         private_esp_packet_t *pkt;
 122
 123         pkt = esp_packet_create_internal(this->packet->clone(this->packet));
 124         pkt->payload = this->payload ? this->payload->clone(this->payload) : NULL;
 125         pkt->next_header = this->next_header;
 126         return &pkt->public.packet;
 127 }
 128
 129 METHOD(esp_packet_t, parse_header, bool,
 130         private_esp_packet_t *this, u_int32_t *spi)
 131 {
 132         bio_reader_t *reader;
 133         u_int32_t seq;
 134
 135         reader = bio_reader_create(this->packet->get_data(this->packet));
 136         if (!reader->read_uint32(reader, spi) ||
 137                 !reader->read_uint32(reader, &seq))
 138         {
 139                 DBG1(DBG_ESP, "failed to parse ESP header: invalid length");
 140                 reader->destroy(reader);
 141                 return FALSE;
 142         }
 143         reader->destroy(reader);
 144
 145         DBG2(DBG_ESP, "parsed ESP header with SPI %.8x [seq %u]", *spi, seq);
 146         *spi = htonl(*spi);
 147         return TRUE;
 148 }
 149
 150 /**
 151  * Check padding as specified in RFC 4303
 152  */
 153 static bool check_padding(chunk_t padding)
 154 {
 155         size_t i;
 156
 157         for (i = 0; i < padding.len; ++i)
 158         {
 159                 if (padding.ptr[i] != (u_int8_t)(i + 1))
 160                 {
 161                         return FALSE;
 162                 }
 163         }
 164         return TRUE;
 165 }
 166
 167 /**
 168  * Remove the padding from the payload and set the next header info
 169  */
 170 static bool remove_padding(private_esp_packet_t *this, chunk_t plaintext)
 171 {
 172         u_int8_t next_header, pad_length;
 173         chunk_t padding, payload;
 174         bio_reader_t *reader;
 175
 176         reader = bio_reader_create(plaintext);
 177         if (!reader->read_uint8_end(reader, &next_header) ||
 178                 !reader->read_uint8_end(reader, &pad_length))
 179         {
 180                 DBG1(DBG_ESP, "parsing ESP payload failed: invalid length");
 181                 goto failed;
 182         }
 183         if (!reader->read_data_end(reader, pad_length, &padding) ||
 184                 !check_padding(padding))
 185         {
 186                 DBG1(DBG_ESP, "parsing ESP payload failed: invalid padding");
 187                 goto failed;
 188         }
 189         this->payload = ip_packet_create(reader->peek(reader));
 190         reader->destroy(reader);
 191         if (!this->payload)
 192         {
 193                 DBG1(DBG_ESP, "parsing ESP payload failed: unsupported payload");
 194                 return FALSE;
 195         }
 196         this->next_header = next_header;
 197         payload = this->payload->get_encoding(this->payload);
 198
 199         DBG3(DBG_ESP, "ESP payload:\n  payload %B\n  padding %B\n  "
 200                  "padding length = %hhu, next header = %hhu", &payload, &padding,
 201                  pad_length, this->next_header);
 202         return TRUE;
 203
 204 failed:
 205         reader->destroy(reader);
 206         chunk_free(&plaintext);
 207         return FALSE;
 208 }
 209
 210 METHOD(esp_packet_t, decrypt, status_t,
 211         private_esp_packet_t *this, esp_context_t *esp_context)
 212 {
 213         bio_reader_t *reader;
 214         u_int32_t spi, seq;
 215         chunk_t data, iv, icv, aad, ciphertext, plaintext;
 216         aead_t *aead;
 217
 218         DESTROY_IF(this->payload);
 219         this->payload = NULL;
 220
 221         data = this->packet->get_data(this->packet);
 222         aead = esp_context->get_aead(esp_context);
 223
 224         reader = bio_reader_create(data);
 225         if (!reader->read_uint32(reader, &spi) ||
 226                 !reader->read_uint32(reader, &seq) ||
 227                 !reader->read_data(reader, aead->get_iv_size(aead), &iv) ||
 228                 !reader->read_data_end(reader, aead->get_icv_size(aead), &icv) ||
 229                 reader->remaining(reader) % aead->get_block_size(aead))
 230         {
 231                 DBG1(DBG_ESP, "ESP decryption failed: invalid length");
 232                 return PARSE_ERROR;
 233         }
 234         ciphertext = reader->peek(reader);
 235         ciphertext.len += icv.len;
 236         reader->destroy(reader);
 237
 238         if (!esp_context->verify_seqno(esp_context, seq))
 239         {
 240                 DBG1(DBG_ESP, "ESP sequence number verification failed:\n  "
 241                          "src %H, dst %H, SPI %.8x [seq %u]",
 242                          get_source(this), get_destination(this), spi, seq);
 243                 return VERIFY_ERROR;
 244         }
 245         DBG3(DBG_ESP, "ESP decryption:\n  SPI %.8x [seq %u]\n  IV %B\n  "
 246                  "encrypted %B\n  ICV %B", spi, seq, &iv, &ciphertext, &icv);
 247
 248         /* aad = spi + seq */
 249         aad = chunk_create(data.ptr, 8);
 250
 251         if (!aead->decrypt(aead, ciphertext, aad, iv, &plaintext))
 252         {
 253                 DBG1(DBG_ESP, "ESP decryption or ICV verification failed");
 254                 return FAILED;
 255         }
 256         esp_context->set_authenticated_seqno(esp_context, seq);
 257
 258         if (!remove_padding(this, plaintext))
 259         {
 260                 return PARSE_ERROR;
 261         }
 262         return SUCCESS;
 263 }
 264
 265 /**
 266  * Generate the padding as specified in RFC4303
 267  */
 268 static void generate_padding(chunk_t padding)
 269 {
 270         size_t i;
 271
 272         for (i = 0; i < padding.len; ++i)
 273         {
 274                 padding.ptr[i] = (u_int8_t)(i + 1);
 275         }
 276 }
 277
 278 METHOD(esp_packet_t, encrypt, status_t,
 279         private_esp_packet_t *this, esp_context_t *esp_context, u_int32_t spi)
 280 {
 281         chunk_t iv, icv, aad, padding, payload, ciphertext;
 282         bio_writer_t *writer;
 283         u_int32_t next_seqno;
 284         size_t blocksize, plainlen;
 285         aead_t *aead;
 286         iv_gen_t *iv_gen;
 287
 288         this->packet->set_data(this->packet, chunk_empty);
 289
 290         if (!esp_context->next_seqno(esp_context, &next_seqno))
 291         {
 292                 DBG1(DBG_ESP, "ESP encapsulation failed: sequence numbers cycled");
 293                 return FAILED;
 294         }
 295
 296         aead = esp_context->get_aead(esp_context);
 297         iv_gen = aead->get_iv_gen(aead);
 298         if (!iv_gen)
 299         {
 300                 DBG1(DBG_ESP, "ESP encryption failed: no IV generator");
 301                 return NOT_FOUND;
 302         }
 303
 304         blocksize = aead->get_block_size(aead);
 305         iv.len = aead->get_iv_size(aead);
 306         icv.len = aead->get_icv_size(aead);
 307
 308         /* plaintext = payload, padding, pad_length, next_header */
 309         payload = this->payload ? this->payload->get_encoding(this->payload)
 310                                                         : chunk_empty;
 311         plainlen = payload.len + 2;
 312         padding.len = blocksize - (plainlen % blocksize);
 313         plainlen += padding.len;
 314
 315         /* len = spi, seq, IV, plaintext, ICV */
 316         writer = bio_writer_create(2 * sizeof(u_int32_t) + iv.len + plainlen +
 317                                                            icv.len);
 318         writer->write_uint32(writer, ntohl(spi));
 319         writer->write_uint32(writer, next_seqno);
 320
 321         iv = writer->skip(writer, iv.len);
 322         if (!iv_gen->get_iv(iv_gen, next_seqno, iv.len, iv.ptr))
 323         {
 324                 DBG1(DBG_ESP, "ESP encryption failed: could not generate IV");
 325                 writer->destroy(writer);
 326                 return FAILED;
 327         }
 328
 329         /* plain-/ciphertext will start here */
 330         ciphertext = writer->get_buf(writer);
 331         ciphertext.ptr += ciphertext.len;
 332         ciphertext.len = plainlen;
 333
 334         writer->write_data(writer, payload);
 335
 336         padding = writer->skip(writer, padding.len);
 337         generate_padding(padding);
 338
 339         writer->write_uint8(writer, padding.len);
 340         writer->write_uint8(writer, this->next_header);
 341
 342         /* aad = spi + seq */
 343         aad = writer->get_buf(writer);
 344         aad.len = 8;
 345         icv = writer->skip(writer, icv.len);
 346
 347         DBG3(DBG_ESP, "ESP before encryption:\n  payload = %B\n  padding = %B\n  "
 348                  "padding length = %hhu, next header = %hhu", &payload, &padding,
 349                  (u_int8_t)padding.len, this->next_header);
 350
 351         /* encrypt/authenticate the content inline */
 352         if (!aead->encrypt(aead, ciphertext, aad, iv, NULL))
 353         {
 354                 DBG1(DBG_ESP, "ESP encryption or ICV generation failed");
 355                 writer->destroy(writer);
 356                 return FAILED;
 357         }
 358
 359         DBG3(DBG_ESP, "ESP packet:\n  SPI %.8x [seq %u]\n  IV %B\n  "
 360                  "encrypted %B\n  ICV %B", ntohl(spi), next_seqno, &iv,
 361                  &ciphertext, &icv);
 362
 363         this->packet->set_data(this->packet, writer->extract_buf(writer));
 364         writer->destroy(writer);
 365         return SUCCESS;
 366 }
 367
 368 METHOD(esp_packet_t, get_next_header, u_int8_t,
 369         private_esp_packet_t *this)
 370 {
 371         return this->next_header;
 372 }
 373
 374 METHOD(esp_packet_t, get_payload, ip_packet_t*,
 375         private_esp_packet_t *this)
 376 {
 377         return this->payload;
 378 }
 379
 380 METHOD(esp_packet_t, extract_payload, ip_packet_t*,
 381         private_esp_packet_t *this)
 382 {
 383         ip_packet_t *payload;
 384
 385         payload = this->payload;
 386         this->payload = NULL;
 387         return payload;
 388 }
 389
 390 METHOD2(esp_packet_t, packet_t, destroy, void,
 391         private_esp_packet_t *this)
 392 {
 393         DESTROY_IF(this->payload);
 394         this->packet->destroy(this->packet);
 395         free(this);
 396 }
 397
 398 static private_esp_packet_t *esp_packet_create_internal(packet_t *packet)
 399 {
 400         private_esp_packet_t *this;
 401
 402         INIT(this,
 403                 .public = {
 404                         .packet = {
 405                                 .set_source = _set_source,
 406                                 .get_source = _get_source,
 407                                 .set_destination = _set_destination,
 408                                 .get_destination = _get_destination,
 409                                 .get_data = _get_data,
 410                                 .set_data = _set_data,
 411                                 .get_dscp = _get_dscp,
 412                                 .set_dscp = _set_dscp,
 413                                 .skip_bytes = _skip_bytes,
 414                                 .clone = _clone,
 415                                 .destroy = _destroy,
 416                         },
 417                         .get_source = _get_source,
 418                         .get_destination = _get_destination,
 419                         .get_next_header = _get_next_header,
 420                         .parse_header = _parse_header,
 421                         .decrypt = _decrypt,
 422                         .encrypt = _encrypt,
 423                         .get_payload = _get_payload,
 424                         .extract_payload = _extract_payload,
 425                         .destroy = _destroy,
 426                 },
 427                 .packet = packet,
 428                 .next_header = IPPROTO_NONE,
 429         );
 430         return this;
 431 }
 432
 433 /**
 434  * Described in header.
 435  */
 436 esp_packet_t *esp_packet_create_from_packet(packet_t *packet)
 437 {
 438         private_esp_packet_t *this;
 439
 440         this = esp_packet_create_internal(packet);
 441
 442         return &this->public;
 443 }
 444
 445 /**
 446  * Described in header.
 447  */
 448 esp_packet_t *esp_packet_create_from_payload(host_t *src, host_t *dst,
 449                                                                                          ip_packet_t *payload)
 450 {
 451         private_esp_packet_t *this;
 452         packet_t *packet;
 453
 454         packet = packet_create_from_data(src, dst, chunk_empty);
 455         this = esp_packet_create_internal(packet);
 456         this->payload = payload;
 457         if (payload)
 458         {
 459                 this->next_header = payload->get_version(payload) == 4 ? IPPROTO_IPIP
 460                                                                                                                            : IPPROTO_IPV6;
 461         }
 462         else
 463         {
 464                 this->next_header = IPPROTO_NONE;
 465         }
 466         return &this->public;
 467 }