src/libsimaka/simaka_crypto.c

   1 /*
   2  * Copyright (C) 2009-2011 Martin Willi
   3  * Hochschule fuer Technik Rapperswil
   4  *
   5  * This program is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License as published by the
   7  * Free Software Foundation; either version 2 of the License, or (at your
   8  * option) any later version.  See <http://www.fsf.org/copyleft/gpl.txt>.
   9  *
  10  * This program is distributed in the hope that it will be useful, but
  11  * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
  12  * or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  13  * for more details.
  14  */
  15
  16 #include "simaka_crypto.h"
  17
  18 #include "simaka_manager.h"
  19
  20 #include <debug.h>
  21
  22 /** length of the k_encr key */
  23 #define KENCR_LEN 16
  24 /** length of the k_auth key */
  25 #define KAUTH_LEN 16
  26 /** length of the MSK */
  27 #define MSK_LEN 64
  28 /** length of the EMSK */
  29 #define EMSK_LEN 64
  30
  31 typedef struct private_simaka_crypto_t private_simaka_crypto_t;
  32
  33 /**
  34  * Private data of an simaka_crypto_t object.
  35  */
  36 struct private_simaka_crypto_t {
  37
  38         /**
  39          * Public simaka_crypto_t interface.
  40          */
  41         simaka_crypto_t public;
  42
  43         /**
  44          * EAP type this crypto is used, SIM or AKA
  45          */
  46         eap_type_t type;
  47
  48         /**
  49          * signer to create/verify AT_MAC
  50          */
  51         signer_t *signer;
  52
  53         /**
  54          * crypter to encrypt/decrypt AT_ENCR_DATA
  55          */
  56         crypter_t *crypter;
  57
  58         /**
  59          * hasher used in key derivation
  60          */
  61         hasher_t *hasher;
  62
  63         /**
  64          * PRF function used in key derivation
  65          */
  66         prf_t *prf;
  67
  68         /**
  69          * Random number generator to generate nonces
  70          */
  71         rng_t *rng;
  72
  73         /**
  74          * Have k_encr/k_auth been derived?
  75          */
  76         bool derived;
  77 };
  78
  79 METHOD(simaka_crypto_t, get_signer, signer_t*,
  80         private_simaka_crypto_t *this)
  81 {
  82         return this->derived ? this->signer : NULL;
  83 }
  84
  85 METHOD(simaka_crypto_t, get_crypter, crypter_t*,
  86         private_simaka_crypto_t *this)
  87 {
  88         return this->derived ? this->crypter : NULL;
  89 }
  90
  91 METHOD(simaka_crypto_t, get_rng, rng_t*,
  92         private_simaka_crypto_t *this)
  93 {
  94         return this->rng;
  95 }
  96
  97 /**
  98  * Call SIM/AKA key hook
  99  */
 100 static void call_hook(private_simaka_crypto_t *this, chunk_t encr, chunk_t auth)
 101 {
 102         simaka_manager_t *mgr;
 103
 104         switch (this->type)
 105         {
 106                 case EAP_SIM:
 107                         mgr = lib->get(lib, "sim-manager");
 108                         break;
 109                 case EAP_AKA:
 110                         mgr = lib->get(lib, "aka-manager");
 111                         break;
 112                 default:
 113                         return;
 114         }
 115         mgr->key_hook(mgr, encr, auth);
 116 }
 117
 118 METHOD(simaka_crypto_t, derive_keys_full, bool,
 119         private_simaka_crypto_t *this, identification_t *id,
 120         chunk_t data, chunk_t *mk, chunk_t *msk)
 121 {
 122         chunk_t str, k_encr, k_auth;
 123         int i;
 124
 125         /* For SIM: MK = SHA1(Identity|n*Kc|NONCE_MT|Version List|Selected Version)
 126          * For AKA: MK = SHA1(Identity|IK|CK) */
 127         if (!this->hasher->get_hash(this->hasher, id->get_encoding(id), NULL) ||
 128                 !this->hasher->allocate_hash(this->hasher, data, mk))
 129         {
 130                 return FALSE;
 131         }
 132         DBG3(DBG_LIB, "MK %B", mk);
 133
 134         /* K_encr | K_auth | MSK | EMSK = prf() | prf() | prf() | prf() */
 135         if (this->prf->set_key(this->prf, *mk))
 136         {
 137                 return FALSE;
 138         }
 139         str = chunk_alloca(this->prf->get_block_size(this->prf) * 3);
 140         for (i = 0; i < 3; i++)
 141         {
 142                 if (!this->prf->get_bytes(this->prf, chunk_empty,
 143                                                                   str.ptr + str.len / 3 * i))
 144                 {
 145                         chunk_clear(mk);
 146                         return FALSE;
 147                 }
 148         }
 149
 150         k_encr = chunk_create(str.ptr, KENCR_LEN);
 151         k_auth = chunk_create(str.ptr + KENCR_LEN, KAUTH_LEN);
 152         DBG3(DBG_LIB, "K_encr %B\nK_auth %B\nMSK %B", &k_encr, &k_auth, &msk);
 153
 154         if (!this->signer->set_key(this->signer, k_auth) ||
 155                 !this->crypter->set_key(this->crypter, k_encr))
 156         {
 157                 chunk_clear(mk);
 158                 return FALSE;
 159         }
 160
 161         *msk = chunk_create(str.ptr + KENCR_LEN + KAUTH_LEN, MSK_LEN);
 162
 163         call_hook(this, k_encr, k_auth);
 164
 165         this->derived = TRUE;
 166         return TRUE;
 167 }
 168
 169 METHOD(simaka_crypto_t, derive_keys_reauth, bool,
 170         private_simaka_crypto_t *this, chunk_t mk)
 171 {
 172         chunk_t str, k_encr, k_auth;
 173         int i;
 174
 175         /* K_encr | K_auth = prf() | prf() */
 176         if (!this->prf->set_key(this->prf, mk))
 177         {
 178                 return FALSE;
 179         }
 180         str = chunk_alloca(this->prf->get_block_size(this->prf) * 2);
 181         for (i = 0; i < 2; i++)
 182         {
 183                 if (!this->prf->get_bytes(this->prf, chunk_empty,
 184                                                                   str.ptr + str.len / 2 * i))
 185                 {
 186                         return FALSE;
 187                 }
 188         }
 189         k_encr = chunk_create(str.ptr, KENCR_LEN);
 190         k_auth = chunk_create(str.ptr + KENCR_LEN, KAUTH_LEN);
 191         DBG3(DBG_LIB, "K_encr %B\nK_auth %B", &k_encr, &k_auth);
 192
 193         if (!this->signer->set_key(this->signer, k_auth) ||
 194                 !this->crypter->set_key(this->crypter, k_encr))
 195         {
 196                 return FALSE;
 197         }
 198
 199         call_hook(this, k_encr, k_auth);
 200
 201         this->derived = TRUE;
 202         return TRUE;
 203 }
 204
 205 METHOD(simaka_crypto_t, derive_keys_reauth_msk, bool,
 206         private_simaka_crypto_t *this, identification_t *id, chunk_t counter,
 207         chunk_t nonce_s, chunk_t mk, chunk_t *msk)
 208 {
 209         char xkey[HASH_SIZE_SHA1];
 210         chunk_t str;
 211         int i;
 212
 213         if (!this->hasher->get_hash(this->hasher, id->get_encoding(id), NULL) ||
 214                 !this->hasher->get_hash(this->hasher, counter, NULL) ||
 215                 !this->hasher->get_hash(this->hasher, nonce_s, NULL) ||
 216                 !this->hasher->get_hash(this->hasher, mk, xkey))
 217         {
 218                 return FALSE;
 219         }
 220
 221         /* MSK | EMSK = prf() | prf() | prf() | prf() */
 222         if (!this->prf->set_key(this->prf, chunk_create(xkey, sizeof(xkey))))
 223         {
 224                 return FALSE;
 225         }
 226         str = chunk_alloca(this->prf->get_block_size(this->prf) * 2);
 227         for (i = 0; i < 2; i++)
 228         {
 229                 if (!this->prf->get_bytes(this->prf, chunk_empty,
 230                                                                   str.ptr + str.len / 2 * i))
 231                 {
 232                         return FALSE;
 233                 }
 234         }
 235         *msk = chunk_create(str.ptr, MSK_LEN);
 236         DBG3(DBG_LIB, "MSK %B", msk);
 237
 238         return TRUE;
 239 }
 240
 241 METHOD(simaka_crypto_t, clear_keys, void,
 242         private_simaka_crypto_t *this)
 243 {
 244         this->derived = FALSE;
 245 }
 246
 247 METHOD(simaka_crypto_t, destroy, void,
 248         private_simaka_crypto_t *this)
 249 {
 250         DESTROY_IF(this->rng);
 251         DESTROY_IF(this->hasher);
 252         DESTROY_IF(this->prf);
 253         DESTROY_IF(this->signer);
 254         DESTROY_IF(this->crypter);
 255         free(this);
 256 }
 257
 258 /**
 259  * See header
 260  */
 261 simaka_crypto_t *simaka_crypto_create(eap_type_t type)
 262 {
 263         private_simaka_crypto_t *this;
 264
 265         INIT(this,
 266                 .public = {
 267                         .get_signer = _get_signer,
 268                         .get_crypter = _get_crypter,
 269                         .get_rng = _get_rng,
 270                         .derive_keys_full = _derive_keys_full,
 271                         .derive_keys_reauth = _derive_keys_reauth,
 272                         .derive_keys_reauth_msk = _derive_keys_reauth_msk,
 273                         .clear_keys = _clear_keys,
 274                         .destroy = _destroy,
 275                 },
 276                 .type = type,
 277                 .rng = lib->crypto->create_rng(lib->crypto, RNG_WEAK),
 278                 .hasher = lib->crypto->create_hasher(lib->crypto, HASH_SHA1),
 279                 .prf = lib->crypto->create_prf(lib->crypto, PRF_FIPS_SHA1_160),
 280                 .signer = lib->crypto->create_signer(lib->crypto, AUTH_HMAC_SHA1_128),
 281                 .crypter = lib->crypto->create_crypter(lib->crypto, ENCR_AES_CBC, 16),
 282         );
 283         if (!this->rng || !this->hasher || !this->prf ||
 284                 !this->signer || !this->crypter)
 285         {
 286                 DBG1(DBG_LIB, "unable to use %N, missing algorithms",
 287                          eap_type_names, type);
 288                 destroy(this);
 289                 return NULL;
 290         }
 291         return &this->public;
 292 }