src/charon/network/receiver.c

   1 /**
   2  * @file receiver.c
   3  *
   4  * @brief Implementation of receiver_t.
   5  *
   6  */
   7
   8 /*
   9  * Copyright (C) 2005-2006 Martin Willi
  10  * Copyright (C) 2005 Jan Hutter
  11  * Hochschule fuer Technik Rapperswil
  12  *
  13  * This program is free software; you can redistribute it and/or modify it
  14  * under the terms of the GNU General Public License as published by the
  15  * Free Software Foundation; either version 2 of the License, or (at your
  16  * option) any later version.  See <http://www.fsf.org/copyleft/gpl.txt>.
  17  *
  18  * This program is distributed in the hope that it will be useful, but
  19  * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
  20  * or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  21  * for more details.
  22  */
  23
  24 #include <stdlib.h>
  25 #include <pthread.h>
  26
  27 #include "receiver.h"
  28
  29 #include <daemon.h>
  30 #include <network/socket.h>
  31 #include <network/packet.h>
  32 #include <processing/job_queue.h>
  33 #include <processing/jobs/job.h>
  34 #include <processing/jobs/process_message_job.h>
  35
  36 /** length of the full cookie, including time (u_int32_t + SHA1()) */
  37 #define COOKIE_LENGTH 24
  38 /** lifetime of a cookie, in seconds */
  39 #define COOKIE_LIFETIME 10
  40 /** how many times to reuse the secret */
  41 #define COOKIE_REUSE 10000
  42 /** require cookies after half open IKE_SAs */
  43 #define COOKIE_TRESHOLD 10
  44 /** how many half open IKE_SAs per peer before blocking */
  45 #define BLOCK_TRESHOLD 5
  46 /** length of the secret to use for cookie calculation */
  47 #define SECRET_LENGTH 16
  48
  49 typedef struct private_receiver_t private_receiver_t;
  50
  51 /**
  52  * Private data of a receiver_t object.
  53  */
  54 struct private_receiver_t {
  55         /**
  56          * Public part of a receiver_t object.
  57          */
  58          receiver_t public;
  59
  60          /**
  61           * Assigned thread.
  62           */
  63          pthread_t assigned_thread;
  64
  65         /**
  66          * current secret to use for cookie calculation
  67          */
  68         char secret[SECRET_LENGTH];
  69
  70         /**
  71          * previous secret used to verify older cookies
  72          */
  73         char secret_old[SECRET_LENGTH];
  74
  75         /**
  76          * how many times we have used "secret" so far
  77          */
  78         u_int32_t secret_used;
  79
  80         /**
  81          * time we did the cookie switch
  82          */
  83         u_int32_t secret_switch;
  84
  85         /**
  86          * time offset to use, hides our system time
  87          */
  88         u_int32_t secret_offset;
  89
  90         /**
  91          * the randomizer to use for secret generation
  92          */
  93         randomizer_t *randomizer;
  94
  95         /**
  96          * hasher to use for cookie calculation
  97          */
  98         hasher_t *hasher;
  99 };
 100
 101 /**
 102  * send a notify back to the sender
 103  */
 104 static void send_notify(message_t *request, notify_type_t type, chunk_t data)
 105 {
 106         if (request->get_request(request) &&
 107                 request->get_exchange_type(request) == IKE_SA_INIT)
 108         {
 109                 message_t *response;
 110                 host_t *src, *dst;
 111                 packet_t *packet;
 112                 ike_sa_id_t *ike_sa_id;
 113
 114                 response = message_create();
 115                 dst = request->get_source(request);
 116                 src = request->get_destination(request);
 117                 response->set_source(response, src->clone(src));
 118                 response->set_destination(response, dst->clone(dst));
 119                 response->set_exchange_type(response, request->get_exchange_type(request));
 120                 response->set_request(response, FALSE);
 121                 response->set_message_id(response, 0);
 122                 ike_sa_id = request->get_ike_sa_id(request);
 123                 ike_sa_id->switch_initiator(ike_sa_id);
 124                 response->set_ike_sa_id(response, ike_sa_id);
 125                 response->add_notify(response, FALSE, type, data);
 126                 if (response->generate(response, NULL, NULL, &packet) == SUCCESS)
 127                 {
 128                         charon->sender->send(charon->sender, packet);
 129                         response->destroy(response);
 130                 }
 131         }
 132 }
 133
 134 /**
 135  * build a cookie
 136  */
 137 static chunk_t cookie_build(private_receiver_t *this, message_t *message,
 138                                                         u_int32_t t, chunk_t secret)
 139 {
 140         u_int64_t spi = message->get_initiator_spi(message);
 141         host_t *ip = message->get_source(message);
 142         chunk_t input, hash = chunk_alloca(this->hasher->get_hash_size(this->hasher));
 143
 144         /* COOKIE = t | sha1( IPi | SPIi | t | secret ) */
 145         input = chunk_cata("cccc", ip->get_address(ip), chunk_from_thing(spi),
 146                                           chunk_from_thing(t), secret);
 147         this->hasher->get_hash(this->hasher, input, hash.ptr);
 148         return chunk_cat("cc", chunk_from_thing(t), hash);
 149 }
 150
 151 /**
 152  * verify a received cookie
 153  */
 154 static bool cookie_verify(private_receiver_t *this, message_t *message,
 155                                                   chunk_t cookie)
 156 {
 157         u_int32_t t, now;
 158         chunk_t reference;
 159         chunk_t secret;
 160
 161         now = time(NULL);
 162         t = *(u_int32_t*)cookie.ptr;
 163
 164         if (cookie.len != COOKIE_LENGTH ||
 165                 t < now - this->secret_offset - COOKIE_LIFETIME)
 166         {
 167                 DBG2(DBG_NET, "received cookie lifetime expired, rejecting");
 168                 return FALSE;
 169         }
 170
 171         /* check if cookie is derived from old_secret */
 172         if (t + this->secret_offset > this->secret_switch)
 173         {
 174                 secret = chunk_from_thing(this->secret);
 175         }
 176         else
 177         {
 178                 secret = chunk_from_thing(this->secret_old);
 179         }
 180
 181         /* compare own calculation against received */
 182         reference = cookie_build(this, message, t, secret);
 183         if (chunk_equals(reference, cookie))
 184         {
 185                 chunk_free(&reference);
 186                 return TRUE;
 187         }
 188         chunk_free(&reference);
 189         return FALSE;
 190 }
 191
 192 /**
 193  * check if cookies are required, and if so, a valid cookie is included
 194  */
 195 static bool cookie_required(private_receiver_t *this, message_t *message)
 196 {
 197         bool failed = FALSE;
 198
 199         if (charon->ike_sa_manager->get_half_open_count(charon->ike_sa_manager,
 200                                                                                                         NULL) >= COOKIE_TRESHOLD)
 201         {
 202                 /* check for a cookie. We don't use our parser here and do it
 203                  * quick and dirty for performance reasons.
 204                  * we assume to cookie is the first payload (which is a MUST), and
 205                  * the cookies SPI length is zero. */
 206                 packet_t *packet = message->get_packet(message);
 207                 chunk_t data = packet->get_data(packet);
 208                 if (data.len <
 209                          IKE_HEADER_LENGTH + NOTIFY_PAYLOAD_HEADER_LENGTH + COOKIE_LENGTH ||
 210                         *(data.ptr + 16) != NOTIFY ||
 211                         *(u_int16_t*)(data.ptr + IKE_HEADER_LENGTH + 6) != htons(COOKIE))
 212                 {
 213                         /* no cookie found */
 214                         failed = TRUE;
 215                 }
 216                 else
 217                 {
 218                         data.ptr += IKE_HEADER_LENGTH + NOTIFY_PAYLOAD_HEADER_LENGTH;
 219                         data.len = COOKIE_LENGTH;
 220                         if (!cookie_verify(this, message, data))
 221                         {
 222                                 DBG2(DBG_NET, "found cookie, but content invalid");
 223                                 failed = TRUE;
 224                         }
 225                 }
 226                 packet->destroy(packet);
 227         }
 228         return failed;
 229 }
 230
 231 /**
 232  * check if peer has to many half open IKE_SAs
 233  */
 234 static bool peer_to_aggressive(private_receiver_t *this, message_t *message)
 235 {
 236         if (charon->ike_sa_manager->get_half_open_count(charon->ike_sa_manager,
 237                                                                 message->get_source(message)) >= BLOCK_TRESHOLD)
 238         {
 239                 return TRUE;
 240         }
 241         return FALSE;
 242 }
 243
 244 /**
 245  * Implementation of receiver_t.receive_packets.
 246  */
 247 static void receive_packets(private_receiver_t *this)
 248 {
 249         packet_t *packet;
 250         message_t *message;
 251         job_t *job;
 252
 253         pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, NULL);
 254         DBG1(DBG_NET, "receiver thread running, thread_ID: %06u",
 255                  (int)pthread_self());
 256
 257         charon->drop_capabilities(charon, TRUE);
 258
 259         while (TRUE)
 260         {
 261                 /* read in a packet */
 262                 if (charon->socket->receive(charon->socket, &packet) != SUCCESS)
 263                 {
 264                         DBG2(DBG_NET, "receiving from socket failed!");
 265                         /* try again after a delay */
 266                         sleep(1);
 267                         continue;
 268                 }
 269
 270                 /* parse message header */
 271                 message = message_create_from_packet(packet);
 272                 if (message->parse_header(message) != SUCCESS)
 273                 {
 274                         DBG1(DBG_NET, "received invalid IKE header from %H, ignored",
 275                                  packet->get_source(packet));
 276                         message->destroy(message);
 277                         continue;
 278                 }
 279
 280                 /* check IKE major version */
 281                 if (message->get_major_version(message) != IKE_MAJOR_VERSION)
 282                 {
 283                         DBG1(DBG_NET, "received unsupported IKE version %d.%d from %H, "
 284                                  "sending INVALID_MAJOR_VERSION", message->get_major_version(message),
 285                                  message->get_minor_version(message), packet->get_source(packet));
 286                         send_notify(message, INVALID_MAJOR_VERSION, chunk_empty);
 287                         message->destroy(message);
 288                         continue;
 289                 }
 290
 291                 if (message->get_request(message) &&
 292                         message->get_exchange_type(message) == IKE_SA_INIT)
 293                 {
 294                         /* check for cookies */
 295                         if (cookie_required(this, message))
 296                         {
 297                                 u_int32_t now = time(NULL);
 298                                 chunk_t cookie = cookie_build(this, message, now - this->secret_offset,
 299                                                                                           chunk_from_thing(this->secret));
 300
 301                                 DBG2(DBG_NET, "received packet from: %#H to %#H",
 302                                          message->get_source(message),
 303                                          message->get_destination(message));
 304                                 DBG2(DBG_NET, "sending COOKIE notify to %H",
 305                                          message->get_source(message));
 306                                 send_notify(message, COOKIE, cookie);
 307                                 chunk_free(&cookie);
 308                                 if (++this->secret_used > COOKIE_REUSE)
 309                                 {
 310                                         /* create new cookie */
 311                                         DBG1(DBG_NET, "generating new cookie secret after %d uses",
 312                                                  this->secret_used);
 313                                         memcpy(this->secret_old, this->secret, SECRET_LENGTH);
 314                                         this->randomizer->get_pseudo_random_bytes(this->randomizer,
 315                                                                                                         SECRET_LENGTH, this->secret);
 316                                         this->secret_switch = now;
 317                                         this->secret_used = 0;
 318                                 }
 319                                 message->destroy(message);
 320                                 continue;
 321                         }
 322
 323                         /* check if peer has not too many IKE_SAs half open */
 324                         if (peer_to_aggressive(this, message))
 325                         {
 326                                 DBG1(DBG_NET, "ignoring IKE_SA setup from %H, "
 327                                          "peer to aggressive", message->get_source(message));
 328                                 message->destroy(message);
 329                                 continue;
 330                         }
 331                 }
 332                 job = (job_t *)process_message_job_create(message);
 333                 charon->job_queue->add(charon->job_queue, job);
 334         }
 335 }
 336
 337 /**
 338  * Implementation of receiver_t.destroy.
 339  */
 340 static void destroy(private_receiver_t *this)
 341 {
 342         pthread_cancel(this->assigned_thread);
 343         pthread_join(this->assigned_thread, NULL);
 344         this->randomizer->destroy(this->randomizer);
 345         this->hasher->destroy(this->hasher);
 346         free(this);
 347 }
 348
 349 /*
 350  * Described in header.
 351  */
 352 receiver_t *receiver_create()
 353 {
 354         private_receiver_t *this = malloc_thing(private_receiver_t);
 355         u_int32_t now = time(NULL);
 356
 357         this->public.destroy = (void(*)(receiver_t*)) destroy;
 358
 359         this->randomizer = randomizer_create();
 360         this->hasher = hasher_create(HASH_SHA1);
 361         this->secret_switch = now;
 362         this->secret_offset = random() % now;
 363         this->secret_used = 0;
 364         this->randomizer->get_pseudo_random_bytes(this->randomizer, SECRET_LENGTH,
 365                                                                                           this->secret);
 366         memcpy(this->secret_old, this->secret, SECRET_LENGTH);
 367
 368         if (pthread_create(&this->assigned_thread, NULL,
 369                                            (void*)receive_packets, this) != 0)
 370         {
 371                 free(this);
 372                 charon->kill(charon, "unable to create receiver thread");
 373         }
 374
 375         return &this->public;
 376 }