src/libipsec/esp_packet.c

   1 /*
   2  * Copyright (C) 2012 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 <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, skip_bytes, void,
 101         private_esp_packet_t *this, size_t bytes)
 102 {
 103         return this->packet->skip_bytes(this->packet, bytes);
 104 }
 105
 106 METHOD(packet_t, clone, packet_t*,
 107         private_esp_packet_t *this)
 108 {
 109         private_esp_packet_t *pkt;
 110
 111         pkt = esp_packet_create_internal(this->packet->clone(this->packet));
 112         pkt->payload = this->payload ? this->payload->clone(this->payload) : NULL;
 113         pkt->next_header = this->next_header;
 114         return &pkt->public.packet;
 115 }
 116
 117 METHOD(esp_packet_t, parse_header, bool,
 118         private_esp_packet_t *this, u_int32_t *spi)
 119 {
 120         bio_reader_t *reader;
 121         u_int32_t seq;
 122
 123         reader = bio_reader_create(this->packet->get_data(this->packet));
 124         if (!reader->read_uint32(reader, spi) ||
 125                 !reader->read_uint32(reader, &seq))
 126         {
 127                 DBG1(DBG_ESP, "failed to parse ESP header: invalid length");
 128                 reader->destroy(reader);
 129                 return FALSE;
 130         }
 131         reader->destroy(reader);
 132
 133         DBG2(DBG_ESP, "parsed ESP header with SPI %.8x [seq %u]", *spi, seq);
 134         *spi = htonl(*spi);
 135         return TRUE;
 136 }
 137
 138 /**
 139  * Check padding as specified in RFC 4303
 140  */
 141 static bool check_padding(chunk_t padding)
 142 {
 143         size_t i;
 144
 145         for (i = 0; i < padding.len; ++i)
 146         {
 147                 if (padding.ptr[i] != (u_int8_t)(i + 1))
 148                 {
 149                         return FALSE;
 150                 }
 151         }
 152         return TRUE;
 153 }
 154
 155 /**
 156  * Remove the padding from the payload and set the next header info
 157  */
 158 static bool remove_padding(private_esp_packet_t *this, chunk_t plaintext)
 159 {
 160         u_int8_t next_header, pad_length;
 161         chunk_t padding, payload;
 162         bio_reader_t *reader;
 163
 164         reader = bio_reader_create(plaintext);
 165         if (!reader->read_uint8_end(reader, &next_header) ||
 166                 !reader->read_uint8_end(reader, &pad_length))
 167         {
 168                 DBG1(DBG_ESP, "parsing ESP payload failed: invalid length");
 169                 goto failed;
 170         }
 171         if (!reader->read_data_end(reader, pad_length, &padding) ||
 172                 !check_padding(padding))
 173         {
 174                 DBG1(DBG_ESP, "parsing ESP payload failed: invalid padding");
 175                 goto failed;
 176         }
 177         this->payload = ip_packet_create(reader->peek(reader));
 178         reader->destroy(reader);
 179         if (!this->payload)
 180         {
 181                 DBG1(DBG_ESP, "parsing ESP payload failed: unsupported payload");
 182                 return FALSE;
 183         }
 184         this->next_header = next_header;
 185         payload = this->payload->get_encoding(this->payload);
 186
 187         DBG3(DBG_ESP, "ESP payload:\n  payload %B\n  padding %B\n  "
 188                  "padding length = %hhu, next header = %hhu", &payload, &padding,
 189                  pad_length, this->next_header);
 190         return TRUE;
 191
 192 failed:
 193         reader->destroy(reader);
 194         chunk_free(&plaintext);
 195         return FALSE;
 196 }
 197
 198 METHOD(esp_packet_t, decrypt, status_t,
 199         private_esp_packet_t *this, esp_context_t *esp_context)
 200 {
 201         bio_reader_t *reader;
 202         u_int32_t spi, seq;
 203         chunk_t data, iv, icv, ciphertext, plaintext;
 204         crypter_t *crypter;
 205         signer_t *signer;
 206
 207         DESTROY_IF(this->payload);
 208         this->payload = NULL;
 209
 210         data = this->packet->get_data(this->packet);
 211         crypter = esp_context->get_crypter(esp_context);
 212         signer = esp_context->get_signer(esp_context);
 213
 214         reader = bio_reader_create(data);
 215         if (!reader->read_uint32(reader, &spi) ||
 216                 !reader->read_uint32(reader, &seq) ||
 217                 !reader->read_data(reader, crypter->get_iv_size(crypter), &iv) ||
 218                 !reader->read_data_end(reader, signer->get_block_size(signer), &icv) ||
 219                 reader->remaining(reader) % crypter->get_block_size(crypter))
 220         {
 221                 DBG1(DBG_ESP, "ESP decryption failed: invalid length");
 222                 return PARSE_ERROR;
 223         }
 224         ciphertext = reader->peek(reader);
 225         reader->destroy(reader);
 226
 227         if (!esp_context->verify_seqno(esp_context, seq))
 228         {
 229                 DBG1(DBG_ESP, "ESP sequence number verification failed:\n  "
 230                          "src %H, dst %H, SPI %.8x [seq %u]",
 231                          get_source(this), get_destination(this), spi, seq);
 232                 return VERIFY_ERROR;
 233         }
 234         DBG3(DBG_ESP, "ESP decryption:\n  SPI %.8x [seq %u]\n  IV %B\n  "
 235                  "encrypted %B\n  ICV %B", spi, seq, &iv, &ciphertext, &icv);
 236
 237         if (!signer->get_signature(signer, chunk_create(data.ptr, 8), NULL) ||
 238                 !signer->get_signature(signer, iv, NULL) ||
 239                 !signer->verify_signature(signer, ciphertext, icv))
 240         {
 241                 DBG1(DBG_ESP, "ICV verification failed!");
 242                 return FAILED;
 243         }
 244         esp_context->set_authenticated_seqno(esp_context, seq);
 245
 246         if (!crypter->decrypt(crypter, ciphertext, iv, &plaintext))
 247         {
 248                 DBG1(DBG_ESP, "ESP decryption failed");
 249                 return FAILED;
 250         }
 251
 252         if (!remove_padding(this, plaintext))
 253         {
 254                 return PARSE_ERROR;
 255         }
 256         return SUCCESS;
 257 }
 258
 259 /**
 260  * Generate the padding as specified in RFC4303
 261  */
 262 static void generate_padding(chunk_t padding)
 263 {
 264         size_t i;
 265
 266         for (i = 0; i < padding.len; ++i)
 267         {
 268                 padding.ptr[i] = (u_int8_t)(i + 1);
 269         }
 270 }
 271
 272 METHOD(esp_packet_t, encrypt, status_t,
 273         private_esp_packet_t *this, esp_context_t *esp_context, u_int32_t spi)
 274 {
 275         chunk_t iv, icv, padding, payload, ciphertext, auth_data;
 276         bio_writer_t *writer;
 277         u_int32_t next_seqno;
 278         size_t blocksize, plainlen;
 279         crypter_t *crypter;
 280         signer_t *signer;
 281         rng_t *rng;
 282
 283         this->packet->set_data(this->packet, chunk_empty);
 284
 285         if (!esp_context->next_seqno(esp_context, &next_seqno))
 286         {
 287                 DBG1(DBG_ESP, "ESP encapsulation failed: sequence numbers cycled");
 288                 return FAILED;
 289         }
 290
 291         rng = lib->crypto->create_rng(lib->crypto, RNG_WEAK);
 292         if (!rng)
 293         {
 294                 DBG1(DBG_ESP, "ESP encryption failed: could not find RNG");
 295                 return NOT_FOUND;
 296         }
 297         crypter = esp_context->get_crypter(esp_context);
 298         signer = esp_context->get_signer(esp_context);
 299
 300         blocksize = crypter->get_block_size(crypter);
 301         iv.len = crypter->get_iv_size(crypter);
 302         icv.len = signer->get_block_size(signer);
 303
 304         /* plaintext = payload, padding, pad_length, next_header */
 305         payload = this->payload ? this->payload->get_encoding(this->payload)
 306                                                         : chunk_empty;
 307         plainlen = payload.len + 2;
 308         padding.len = blocksize - (plainlen % blocksize);
 309         plainlen += padding.len;
 310
 311         /* len = spi, seq, IV, plaintext, ICV */
 312         writer = bio_writer_create(2 * sizeof(u_int32_t) + iv.len + plainlen +
 313                                                            icv.len);
 314         writer->write_uint32(writer, ntohl(spi));
 315         writer->write_uint32(writer, next_seqno);
 316
 317         iv = writer->skip(writer, iv.len);
 318         if (!rng->get_bytes(rng, iv.len, iv.ptr))
 319         {
 320                 DBG1(DBG_ESP, "ESP encryption failed: could not generate IV");
 321                 writer->destroy(writer);
 322                 rng->destroy(rng);
 323                 return FAILED;
 324         }
 325         rng->destroy(rng);
 326
 327         /* plain-/ciphertext will start here */
 328         ciphertext = writer->get_buf(writer);
 329         ciphertext.ptr += ciphertext.len;
 330         ciphertext.len = plainlen;
 331
 332         writer->write_data(writer, payload);
 333
 334         padding = writer->skip(writer, padding.len);
 335         generate_padding(padding);
 336
 337         writer->write_uint8(writer, padding.len);
 338         writer->write_uint8(writer, this->next_header);
 339
 340         DBG3(DBG_ESP, "ESP before encryption:\n  payload = %B\n  padding = %B\n  "
 341                  "padding length = %hhu, next header = %hhu", &payload, &padding,
 342                  (u_int8_t)padding.len, this->next_header);
 343
 344         /* encrypt the content inline */
 345         if (!crypter->encrypt(crypter, ciphertext, iv, NULL))
 346         {
 347                 DBG1(DBG_ESP, "ESP encryption failed");
 348                 writer->destroy(writer);
 349                 return FAILED;
 350         }
 351
 352         /* calculate signature */
 353         auth_data = writer->get_buf(writer);
 354         icv = writer->skip(writer, icv.len);
 355         if (!signer->get_signature(signer, auth_data, icv.ptr))
 356         {
 357                 DBG1(DBG_ESP, "ESP encryption failed: signature generation failed");
 358                 writer->destroy(writer);
 359                 return FAILED;
 360         }
 361
 362         DBG3(DBG_ESP, "ESP packet:\n  SPI %.8x [seq %u]\n  IV %B\n  "
 363                  "encrypted %B\n  ICV %B", ntohl(spi), next_seqno, &iv,
 364                  &ciphertext, &icv);
 365
 366         this->packet->set_data(this->packet, writer->extract_buf(writer));
 367         writer->destroy(writer);
 368         return SUCCESS;
 369 }
 370
 371 METHOD(esp_packet_t, get_next_header, u_int8_t,
 372         private_esp_packet_t *this)
 373 {
 374         return this->next_header;
 375 }
 376
 377 METHOD(esp_packet_t, get_payload, ip_packet_t*,
 378         private_esp_packet_t *this)
 379 {
 380         return this->payload;
 381 }
 382
 383 METHOD(esp_packet_t, extract_payload, ip_packet_t*,
 384         private_esp_packet_t *this)
 385 {
 386         ip_packet_t *payload;
 387
 388         payload = this->payload;
 389         this->payload = NULL;
 390         return payload;
 391 }
 392
 393 METHOD2(esp_packet_t, packet_t, destroy, void,
 394         private_esp_packet_t *this)
 395 {
 396         DESTROY_IF(this->payload);
 397         this->packet->destroy(this->packet);
 398         free(this);
 399 }
 400
 401 static private_esp_packet_t *esp_packet_create_internal(packet_t *packet)
 402 {
 403         private_esp_packet_t *this;
 404
 405         INIT(this,
 406                 .public = {
 407                         .packet = {
 408                                 .set_source = _set_source,
 409                                 .get_source = _get_source,
 410                                 .set_destination = _set_destination,
 411                                 .get_destination = _get_destination,
 412                                 .get_data = _get_data,
 413                                 .set_data = _set_data,
 414                                 .skip_bytes = _skip_bytes,
 415                                 .clone = _clone,
 416                                 .destroy = _destroy,
 417                         },
 418                         .get_source = _get_source,
 419                         .get_destination = _get_destination,
 420                         .get_next_header = _get_next_header,
 421                         .parse_header = _parse_header,
 422                         .decrypt = _decrypt,
 423                         .encrypt = _encrypt,
 424                         .get_payload = _get_payload,
 425                         .extract_payload = _extract_payload,
 426                         .destroy = _destroy,
 427                 },
 428                 .packet = packet,
 429                 .next_header = IPPROTO_NONE,
 430         );
 431         return this;
 432 }
 433
 434 /**
 435  * Described in header.
 436  */
 437 esp_packet_t *esp_packet_create_from_packet(packet_t *packet)
 438 {
 439         private_esp_packet_t *this;
 440
 441         this = esp_packet_create_internal(packet);
 442
 443         return &this->public;
 444 }
 445
 446 /**
 447  * Described in header.
 448  */
 449 esp_packet_t *esp_packet_create_from_payload(host_t *src, host_t *dst,
 450                                                                                          ip_packet_t *payload)
 451 {
 452         private_esp_packet_t *this;
 453         packet_t *packet;
 454
 455         packet = packet_create_from_data(src, dst, chunk_empty);
 456         this = esp_packet_create_internal(packet);
 457         this->payload = payload;
 458         if (payload)
 459         {
 460                 this->next_header = payload->get_version(payload) == 4 ? IPPROTO_IPIP
 461                                                                                                                            : IPPROTO_IPV6;
 462         }
 463         else
 464         {
 465                 this->next_header = IPPROTO_NONE;
 466         }
 467         return &this->public;
 468 }