src/libcharon/network/receiver.c

   1 /*
   2  * Copyright (C) 2008 Tobias Brunner
   3  * Copyright (C) 2005-2006 Martin Willi
   4  * Copyright (C) 2005 Jan Hutter
   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 #include <stdlib.h>
  19 #include <unistd.h>
  20
  21 #include "receiver.h"
  22
  23 #include <daemon.h>
  24 #include <network/socket.h>
  25 #include <network/packet.h>
  26 #include <processing/jobs/job.h>
  27 #include <processing/jobs/process_message_job.h>
  28 #include <processing/jobs/callback_job.h>
  29 #include <crypto/hashers/hasher.h>
  30
  31 /** lifetime of a cookie, in seconds */
  32 #define COOKIE_LIFETIME 10
  33 /** how many times to reuse the secret */
  34 #define COOKIE_REUSE 10000
  35 /** default value for private_receiver_t.cookie_threshold */
  36 #define COOKIE_THRESHOLD_DEFAULT 10
  37 /** default value for private_receiver_t.block_threshold */
  38 #define BLOCK_THRESHOLD_DEFAULT 5
  39 /** length of the secret to use for cookie calculation */
  40 #define SECRET_LENGTH 16
  41
  42 typedef struct private_receiver_t private_receiver_t;
  43
  44 /**
  45  * Private data of a receiver_t object.
  46  */
  47 struct private_receiver_t {
  48         /**
  49          * Public part of a receiver_t object.
  50          */
  51         receiver_t public;
  52
  53         /**
  54          * Threads job receiving packets
  55          */
  56         callback_job_t *job;
  57
  58         /**
  59          * current secret to use for cookie calculation
  60          */
  61         char secret[SECRET_LENGTH];
  62
  63         /**
  64          * previous secret used to verify older cookies
  65          */
  66         char secret_old[SECRET_LENGTH];
  67
  68         /**
  69          * how many times we have used "secret" so far
  70          */
  71         u_int32_t secret_used;
  72
  73         /**
  74          * time we did the cookie switch
  75          */
  76         u_int32_t secret_switch;
  77
  78         /**
  79          * time offset to use, hides our system time
  80          */
  81         u_int32_t secret_offset;
  82
  83         /**
  84          * the RNG to use for secret generation
  85          */
  86         rng_t *rng;
  87
  88         /**
  89          * hasher to use for cookie calculation
  90          */
  91         hasher_t *hasher;
  92
  93         /**
  94          * require cookies after this many half open IKE_SAs
  95          */
  96         u_int32_t cookie_threshold;
  97
  98         /**
  99          * how many half open IKE_SAs per peer before blocking
 100          */
 101         u_int32_t block_threshold;
 102
 103         /**
 104          * Delay for receiving incoming packets, to simulate larger RTT
 105          */
 106         int receive_delay;
 107
 108         /**
 109          * Specific message type to delay, 0 for any
 110          */
 111         int receive_delay_type;
 112
 113         /**
 114          * Delay request messages?
 115          */
 116         bool receive_delay_request;
 117
 118         /**
 119          * Delay response messages?
 120          */
 121         bool receive_delay_response;
 122 };
 123
 124 /**
 125  * send a notify back to the sender
 126  */
 127 static void send_notify(message_t *request, notify_type_t type, chunk_t data)
 128 {
 129         if (request->get_request(request) &&
 130                 request->get_exchange_type(request) == IKE_SA_INIT)
 131         {
 132                 message_t *response;
 133                 host_t *src, *dst;
 134                 packet_t *packet;
 135                 ike_sa_id_t *ike_sa_id;
 136
 137                 response = message_create();
 138                 dst = request->get_source(request);
 139                 src = request->get_destination(request);
 140                 response->set_source(response, src->clone(src));
 141                 response->set_destination(response, dst->clone(dst));
 142                 response->set_exchange_type(response, request->get_exchange_type(request));
 143                 response->set_request(response, FALSE);
 144                 response->set_message_id(response, 0);
 145                 ike_sa_id = request->get_ike_sa_id(request);
 146                 ike_sa_id->switch_initiator(ike_sa_id);
 147                 response->set_ike_sa_id(response, ike_sa_id);
 148                 response->add_notify(response, FALSE, type, data);
 149                 if (response->generate(response, NULL, &packet) == SUCCESS)
 150                 {
 151                         charon->sender->send(charon->sender, packet);
 152                         response->destroy(response);
 153                 }
 154         }
 155 }
 156
 157 /**
 158  * build a cookie
 159  */
 160 static chunk_t cookie_build(private_receiver_t *this, message_t *message,
 161                                                         u_int32_t t, chunk_t secret)
 162 {
 163         u_int64_t spi = message->get_initiator_spi(message);
 164         host_t *ip = message->get_source(message);
 165         chunk_t input, hash;
 166
 167         /* COOKIE = t | sha1( IPi | SPIi | t | secret ) */
 168         input = chunk_cata("cccc", ip->get_address(ip), chunk_from_thing(spi),
 169                                           chunk_from_thing(t), secret);
 170         hash = chunk_alloca(this->hasher->get_hash_size(this->hasher));
 171         this->hasher->get_hash(this->hasher, input, hash.ptr);
 172         return chunk_cat("cc", chunk_from_thing(t), hash);
 173 }
 174
 175 /**
 176  * verify a received cookie
 177  */
 178 static bool cookie_verify(private_receiver_t *this, message_t *message,
 179                                                   chunk_t cookie)
 180 {
 181         u_int32_t t, now;
 182         chunk_t reference;
 183         chunk_t secret;
 184
 185         now = time_monotonic(NULL);
 186         t = *(u_int32_t*)cookie.ptr;
 187
 188         if (cookie.len != sizeof(u_int32_t) +
 189                         this->hasher->get_hash_size(this->hasher) ||
 190                 t < now - this->secret_offset - COOKIE_LIFETIME)
 191         {
 192                 DBG2(DBG_NET, "received cookie lifetime expired, rejecting");
 193                 return FALSE;
 194         }
 195
 196         /* check if cookie is derived from old_secret */
 197         if (t + this->secret_offset > this->secret_switch)
 198         {
 199                 secret = chunk_from_thing(this->secret);
 200         }
 201         else
 202         {
 203                 secret = chunk_from_thing(this->secret_old);
 204         }
 205
 206         /* compare own calculation against received */
 207         reference = cookie_build(this, message, t, secret);
 208         if (chunk_equals(reference, cookie))
 209         {
 210                 chunk_free(&reference);
 211                 return TRUE;
 212         }
 213         chunk_free(&reference);
 214         return FALSE;
 215 }
 216
 217 /**
 218  * check if cookies are required, and if so, a valid cookie is included
 219  */
 220 static bool cookie_required(private_receiver_t *this, message_t *message)
 221 {
 222         bool failed = FALSE;
 223
 224         if (charon->ike_sa_manager->get_half_open_count(charon->ike_sa_manager,
 225                                                                                                 NULL) >= this->cookie_threshold)
 226         {
 227                 /* check for a cookie. We don't use our parser here and do it
 228                  * quick and dirty for performance reasons.
 229                  * we assume the cookie is the first payload (which is a MUST), and
 230                  * the cookie's SPI length is zero. */
 231                 packet_t *packet = message->get_packet(message);
 232                 chunk_t data = packet->get_data(packet);
 233                 if (data.len <
 234                          IKE_HEADER_LENGTH + NOTIFY_PAYLOAD_HEADER_LENGTH +
 235                          sizeof(u_int32_t) + this->hasher->get_hash_size(this->hasher) ||
 236                         *(data.ptr + 16) != NOTIFY ||
 237                         *(u_int16_t*)(data.ptr + IKE_HEADER_LENGTH + 6) != htons(COOKIE))
 238                 {
 239                         /* no cookie found */
 240                         failed = TRUE;
 241                 }
 242                 else
 243                 {
 244                         data.ptr += IKE_HEADER_LENGTH + NOTIFY_PAYLOAD_HEADER_LENGTH;
 245                         data.len = sizeof(u_int32_t) + this->hasher->get_hash_size(this->hasher);
 246                         if (!cookie_verify(this, message, data))
 247                         {
 248                                 DBG2(DBG_NET, "found cookie, but content invalid");
 249                                 failed = TRUE;
 250                         }
 251                 }
 252                 packet->destroy(packet);
 253         }
 254         return failed;
 255 }
 256
 257 /**
 258  * check if peer has to many half open IKE_SAs
 259  */
 260 static bool peer_too_aggressive(private_receiver_t *this, message_t *message)
 261 {
 262         if (charon->ike_sa_manager->get_half_open_count(charon->ike_sa_manager,
 263                                                 message->get_source(message)) >= this->block_threshold)
 264         {
 265                 return TRUE;
 266         }
 267         return FALSE;
 268 }
 269
 270 /**
 271  * Job callback to receive packets
 272  */
 273 static job_requeue_t receive_packets(private_receiver_t *this)
 274 {
 275         packet_t *packet;
 276         message_t *message;
 277
 278         /* read in a packet */
 279         if (charon->socket->receive(charon->socket, &packet) != SUCCESS)
 280         {
 281                 DBG2(DBG_NET, "receiving from socket failed!");
 282                 return JOB_REQUEUE_FAIR;
 283         }
 284
 285         /* parse message header */
 286         message = message_create_from_packet(packet);
 287         if (message->parse_header(message) != SUCCESS)
 288         {
 289                 DBG1(DBG_NET, "received invalid IKE header from %H - ignored",
 290                          packet->get_source(packet));
 291                 message->destroy(message);
 292                 return JOB_REQUEUE_DIRECT;
 293         }
 294
 295         /* check IKE major version */
 296         if (message->get_major_version(message) != IKE_MAJOR_VERSION)
 297         {
 298                 DBG1(DBG_NET, "received unsupported IKE version %d.%d from %H, "
 299                          "sending INVALID_MAJOR_VERSION", message->get_major_version(message),
 300                          message->get_minor_version(message), packet->get_source(packet));
 301                 send_notify(message, INVALID_MAJOR_VERSION, chunk_empty);
 302                 message->destroy(message);
 303                 return JOB_REQUEUE_DIRECT;
 304         }
 305
 306         if (message->get_request(message) &&
 307                 message->get_exchange_type(message) == IKE_SA_INIT)
 308         {
 309                 /* check for cookies */
 310                 if (this->cookie_threshold && cookie_required(this, message))
 311                 {
 312                         u_int32_t now = time_monotonic(NULL);
 313                         chunk_t cookie = cookie_build(this, message, now - this->secret_offset,
 314                                                                                   chunk_from_thing(this->secret));
 315
 316                         DBG2(DBG_NET, "received packet from: %#H to %#H",
 317                                  message->get_source(message),
 318                                  message->get_destination(message));
 319                         DBG2(DBG_NET, "sending COOKIE notify to %H",
 320                                  message->get_source(message));
 321                         send_notify(message, COOKIE, cookie);
 322                         chunk_free(&cookie);
 323                         if (++this->secret_used > COOKIE_REUSE)
 324                         {
 325                                 /* create new cookie */
 326                                 DBG1(DBG_NET, "generating new cookie secret after %d uses",
 327                                          this->secret_used);
 328                                 memcpy(this->secret_old, this->secret, SECRET_LENGTH);
 329                                 this->rng->get_bytes(this->rng, SECRET_LENGTH, this->secret);
 330                                 this->secret_switch = now;
 331                                 this->secret_used = 0;
 332                         }
 333                         message->destroy(message);
 334                         return JOB_REQUEUE_DIRECT;
 335                 }
 336
 337                 /* check if peer has not too many IKE_SAs half open */
 338                 if (this->block_threshold && peer_too_aggressive(this, message))
 339                 {
 340                         DBG1(DBG_NET, "ignoring IKE_SA setup from %H, "
 341                                  "peer too aggressive", message->get_source(message));
 342                         message->destroy(message);
 343                         return JOB_REQUEUE_DIRECT;
 344                 }
 345         }
 346         if (this->receive_delay)
 347         {
 348                 if (this->receive_delay_type == 0 ||
 349                         this->receive_delay_type == message->get_exchange_type(message))
 350                 {
 351                         if ((message->get_request(message) && this->receive_delay_request) ||
 352                                 (!message->get_request(message) && this->receive_delay_response))
 353                         {
 354                                 DBG1(DBG_NET, "using receive delay: %dms",
 355                                          this->receive_delay);
 356                                 charon->scheduler->schedule_job_ms(charon->scheduler,
 357                                                                 (job_t*)process_message_job_create(message),
 358                                                                 this->receive_delay);
 359                                 return JOB_REQUEUE_DIRECT;
 360                         }
 361                 }
 362         }
 363         charon->processor->queue_job(charon->processor,
 364                                                                  (job_t*)process_message_job_create(message));
 365         return JOB_REQUEUE_DIRECT;
 366 }
 367
 368 METHOD(receiver_t, destroy, void,
 369         private_receiver_t *this)
 370 {
 371         this->job->cancel(this->job);
 372         this->rng->destroy(this->rng);
 373         this->hasher->destroy(this->hasher);
 374         free(this);
 375 }
 376
 377 /*
 378  * Described in header.
 379  */
 380 receiver_t *receiver_create()
 381 {
 382         private_receiver_t *this;
 383         u_int32_t now = time_monotonic(NULL);
 384
 385         INIT(this,
 386                 .public = {
 387                         .destroy = _destroy,
 388                 },
 389                 .secret_switch = now,
 390                 .secret_offset = random() % now,
 391         );
 392
 393         if (lib->settings->get_bool(lib->settings, "charon.dos_protection", TRUE))
 394         {
 395                 this->cookie_threshold = lib->settings->get_int(lib->settings,
 396                                                 "charon.cookie_threshold", COOKIE_THRESHOLD_DEFAULT);
 397                 this->block_threshold = lib->settings->get_int(lib->settings,
 398                                                 "charon.block_threshold", BLOCK_THRESHOLD_DEFAULT);
 399         }
 400         this->receive_delay = lib->settings->get_int(lib->settings,
 401                                                 "charon.receive_delay", 0);
 402         this->receive_delay_type = lib->settings->get_int(lib->settings,
 403                                                 "charon.receive_delay_type", 0),
 404         this->receive_delay_request = lib->settings->get_bool(lib->settings,
 405                                                 "charon.receive_delay_request", TRUE),
 406         this->receive_delay_response = lib->settings->get_int(lib->settings,
 407                                                 "charon.receive_delay_response", TRUE),
 408
 409         this->hasher = lib->crypto->create_hasher(lib->crypto, HASH_PREFERRED);
 410         if (this->hasher == NULL)
 411         {
 412                 DBG1(DBG_NET, "creating cookie hasher failed, no hashers supported");
 413                 free(this);
 414                 return NULL;
 415         }
 416         this->rng = lib->crypto->create_rng(lib->crypto, RNG_STRONG);
 417         if (this->rng == NULL)
 418         {
 419                 DBG1(DBG_NET, "creating cookie RNG failed, no RNG supported");
 420                 this->hasher->destroy(this->hasher);
 421                 free(this);
 422                 return NULL;
 423         }
 424         this->rng->get_bytes(this->rng, SECRET_LENGTH, this->secret);
 425         memcpy(this->secret_old, this->secret, SECRET_LENGTH);
 426
 427         this->job = callback_job_create((callback_job_cb_t)receive_packets,
 428                                                                         this, NULL, NULL);
 429         charon->processor->queue_job(charon->processor, (job_t*)this->job);
 430
 431         return &this->public;
 432 }
 433