aboutsummaryrefslogtreecommitdiff
path: root/src/util/crypto.c
blob: 158bb95111cac0f624a722c0405926865fa96588 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
/*
  This file is part of TALER
  Copyright (C) 2014, 2015 Christian Grothoff (and other contributing authors)

  TALER is free software; you can redistribute it and/or modify it under the
  terms of the GNU General Public License as published by the Free Software
  Foundation; either version 3, or (at your option) any later version.

  TALER is distributed in the hope that it will be useful, but WITHOUT ANY
  WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
  A PARTICULAR PURPOSE.  See the GNU General Public License for more details.

  You should have received a copy of the GNU General Public License along with
  TALER; see the file COPYING.  If not, If not, see <http://www.gnu.org/licenses/>
*/
/**
 * @file util/crypto.c
 * @brief Cryptographic utility functions
 * @author Sree Harsha Totakura <sreeharsha@totakura.in>
 * @author Florian Dold
 * @author Benedikt Mueller
 * @author Christian Grothoff
 */
#include "platform.h"
#include "taler_util.h"
#include <gnunet/gnunet_util_lib.h>
#include <gcrypt.h>


/**
 * Function called by libgcrypt on serious errors.
 * Prints an error message and aborts the process.
 *
 * @param cls NULL
 * @param wtf unknown
 * @param msg error message
 */
static void
fatal_error_handler (void *cls,
                     int wtf,
                     const char *msg)
{
  TALER_LOG_ERROR ("Fatal error in libgcrypt: %s\n",
             msg);
  abort();
}


/**
 * Initialize libgcrypt.
 */
void
TALER_gcrypt_init ()
{
  gcry_set_fatalerror_handler (&fatal_error_handler,
                               NULL);
  TALER_assert_as (gcry_check_version (NEED_LIBGCRYPT_VERSION),
                   "libgcrypt version mismatch");
  /* Disable secure memory.  */
  gcry_control (GCRYCTL_DISABLE_SECMEM, 0);
  gcry_control (GCRYCTL_INITIALIZATION_FINISHED, 0);
}


/**
 * Derive symmetric key material for refresh operations from
 * a given shared secret for link decryption.
 *
 * @param secret the shared secret
 * @param[out] iv set to initialization vector
 * @param[out] skey set to session key
 */
static void
derive_refresh_key (const struct TALER_LinkSecretP *secret,
                    struct GNUNET_CRYPTO_SymmetricInitializationVector *iv,
                    struct GNUNET_CRYPTO_SymmetricSessionKey *skey)
{
  static const char ctx_key[] = "taler-link-skey";
  static const char ctx_iv[] = "taler-link-iv";

  GNUNET_assert (GNUNET_YES ==
                 GNUNET_CRYPTO_kdf (skey, sizeof (struct GNUNET_CRYPTO_SymmetricSessionKey),
                                    ctx_key, strlen (ctx_key),
                                    secret, sizeof (struct TALER_LinkSecretP),
                                    NULL, 0));
  GNUNET_assert (GNUNET_YES ==
                 GNUNET_CRYPTO_kdf (iv, sizeof (struct GNUNET_CRYPTO_SymmetricInitializationVector),
                                    ctx_iv, strlen (ctx_iv),
                                    secret, sizeof (struct TALER_LinkSecretP),
                                    NULL, 0));
}


/**
 * Derive symmetric key material for refresh operations from
 * a given shared secret for key decryption.
 *
 * @param secret the shared secret
 * @param[out] iv set to initialization vector
 * @param[out] skey set to session key
 */
static void
derive_transfer_key (const struct TALER_TransferSecretP *secret,
                     struct GNUNET_CRYPTO_SymmetricInitializationVector *iv,
                     struct GNUNET_CRYPTO_SymmetricSessionKey *skey)
{
  static const char ctx_key[] = "taler-transfer-skey";
  static const char ctx_iv[] = "taler-transfer-iv";

  GNUNET_assert (GNUNET_YES ==
                 GNUNET_CRYPTO_kdf (skey, sizeof (struct GNUNET_CRYPTO_SymmetricSessionKey),
                                    ctx_key, strlen (ctx_key),
                                    secret, sizeof (struct TALER_TransferSecretP),
                                    NULL, 0));
  GNUNET_assert (GNUNET_YES ==
                 GNUNET_CRYPTO_kdf (iv, sizeof (struct GNUNET_CRYPTO_SymmetricInitializationVector),
                                    ctx_iv, strlen (ctx_iv),
                                    secret, sizeof (struct TALER_TransferSecretP),
                                    NULL, 0));
}


/**
 * Use the @a trans_sec (from ECDHE) to decrypt the @a secret_enc
 * to obtain the @a secret to decrypt the linkage data.
 *
 * @param secret_enc encrypted secret
 * @param trans_sec transfer secret
 * @param secret shared secret for refresh link decryption
 * @return #GNUNET_OK on success
 */
int
TALER_transfer_decrypt (const struct TALER_EncryptedLinkSecretP *secret_enc,
                        const struct TALER_TransferSecretP *trans_sec,
                        struct TALER_LinkSecretP *secret)
{
  struct GNUNET_CRYPTO_SymmetricInitializationVector iv;
  struct GNUNET_CRYPTO_SymmetricSessionKey skey;
  ssize_t s;

  GNUNET_assert (sizeof (struct TALER_EncryptedLinkSecretP) ==
                 sizeof (struct TALER_LinkSecretP));
  derive_transfer_key (trans_sec, &iv, &skey);
  s = GNUNET_CRYPTO_symmetric_decrypt (secret_enc,
				       sizeof (struct TALER_LinkSecretP),
				       &skey,
				       &iv,
				       secret);
  if (sizeof (struct TALER_LinkSecretP) != s)
    return GNUNET_SYSERR;
  return GNUNET_OK;
}


/**
 * Use the @a trans_sec (from ECDHE) to encrypt the @a secret
 * to obtain the @a secret_enc.
 *
 * @param secret shared secret for refresh link decryption
 * @param trans_sec transfer secret
 * @param[out] secret_enc encrypted secret
 * @return #GNUNET_OK on success
 */
int
TALER_transfer_encrypt (const struct TALER_LinkSecretP *secret,
                        const struct TALER_TransferSecretP *trans_sec,
                        struct TALER_EncryptedLinkSecretP *secret_enc)
{
  struct GNUNET_CRYPTO_SymmetricInitializationVector iv;
  struct GNUNET_CRYPTO_SymmetricSessionKey skey;
  ssize_t s;

  GNUNET_assert (sizeof (struct TALER_EncryptedLinkSecretP) ==
                 sizeof (struct TALER_LinkSecretP));
  derive_transfer_key (trans_sec, &iv, &skey);
  s = GNUNET_CRYPTO_symmetric_encrypt (secret,
				       sizeof (struct TALER_LinkSecretP),
				       &skey,
				       &iv,
				       secret_enc);
  if (sizeof (struct TALER_LinkSecretP) != s)
    return GNUNET_SYSERR;
  return GNUNET_OK;
}


/**
 * Decrypt refresh link information.
 *
 * @param input encrypted refresh link data
 * @param secret shared secret to use for decryption
 * @return NULL on error
 */
struct TALER_RefreshLinkDecrypted *
TALER_refresh_decrypt (const struct TALER_RefreshLinkEncrypted *input,
                       const struct TALER_LinkSecretP *secret)
{
  struct TALER_RefreshLinkDecrypted *ret;
  struct GNUNET_CRYPTO_SymmetricInitializationVector iv;
  struct GNUNET_CRYPTO_SymmetricSessionKey skey;
  size_t buf_size = input->blinding_key_enc_size
    + sizeof (struct GNUNET_CRYPTO_EcdsaPrivateKey);
  char buf[buf_size];

  GNUNET_assert (input->blinding_key_enc == (const char *) &input[1]);
  derive_refresh_key (secret, &iv, &skey);
  if (buf_size !=
      GNUNET_CRYPTO_symmetric_decrypt (input->coin_priv_enc,
                                       buf_size,
                                       &skey,
                                       &iv,
                                       buf))
    return NULL;
  ret = GNUNET_new (struct TALER_RefreshLinkDecrypted);
  memcpy (&ret->coin_priv,
          buf,
          sizeof (union TALER_CoinSpendPrivateKeyP));
  ret->blinding_key.rsa_blinding_key
    = GNUNET_CRYPTO_rsa_blinding_key_decode (&buf[sizeof (struct GNUNET_CRYPTO_EcdsaPrivateKey)],
                                             input->blinding_key_enc_size);
  if (NULL == ret->blinding_key.rsa_blinding_key)
  {
    GNUNET_free (ret);
    return NULL;
  }
  return ret;
}


/**
 * Encrypt refresh link information.
 *
 * @param input plaintext refresh link data
 * @param secret shared secret to use for encryption
 * @return NULL on error (should never happen)
 */
struct TALER_RefreshLinkEncrypted *
TALER_refresh_encrypt (const struct TALER_RefreshLinkDecrypted *input,
                       const struct TALER_LinkSecretP *secret)
{
  char *b_buf;
  size_t b_buf_size;
  struct GNUNET_CRYPTO_SymmetricInitializationVector iv;
  struct GNUNET_CRYPTO_SymmetricSessionKey skey;
  struct TALER_RefreshLinkEncrypted *ret;

  derive_refresh_key (secret, &iv, &skey);
  b_buf_size = GNUNET_CRYPTO_rsa_blinding_key_encode (input->blinding_key.rsa_blinding_key,
                                                      &b_buf);
  ret = GNUNET_malloc (sizeof (struct TALER_RefreshLinkEncrypted) +
                       b_buf_size);
  ret->blinding_key_enc = (const char *) &ret[1];
  ret->blinding_key_enc_size = b_buf_size;
  {
    size_t buf_size = b_buf_size + sizeof (struct GNUNET_CRYPTO_EcdsaPrivateKey);
    char buf[buf_size];

    memcpy (buf,
            &input->coin_priv,
            sizeof (struct GNUNET_CRYPTO_EcdsaPrivateKey));
    memcpy (&buf[sizeof (struct GNUNET_CRYPTO_EcdsaPrivateKey)],
            b_buf,
            b_buf_size);

    if (buf_size !=
        GNUNET_CRYPTO_symmetric_encrypt (buf,
                                         buf_size,
                                         &skey,
                                         &iv,
                                         ret->coin_priv_enc))
    {
      GNUNET_free (ret);
      return NULL;
    }
  }
  return ret;
}


/**
 * Decode encrypted refresh link information from buffer.
 *
 * @param buf buffer with refresh link data
 * @param buf_len number of bytes in @a buf
 * @return NULL on error (@a buf_len too small)
 */
struct TALER_RefreshLinkEncrypted *
TALER_refresh_link_encrypted_decode (const char *buf,
                                     size_t buf_len)
{
  struct TALER_RefreshLinkEncrypted *rle;

  if (buf_len < sizeof (struct GNUNET_CRYPTO_EcdsaPrivateKey))
    return NULL;
  rle = GNUNET_malloc (sizeof (struct TALER_RefreshLinkEncrypted) +
                       buf_len - sizeof (struct GNUNET_CRYPTO_EcdsaPrivateKey));
  rle->blinding_key_enc = (const char *) &rle[1];
  rle->blinding_key_enc_size = buf_len - sizeof (struct GNUNET_CRYPTO_EcdsaPrivateKey);
  memcpy (rle->coin_priv_enc,
          buf,
          buf_len);
  return rle;
}


/**
 * Check if a coin is valid; that is, whether the denomination key exists,
 * is not expired, and the signature is correct.
 *
 * @param coin_public_info the coin public info to check for validity
 * @return #GNUNET_YES if the coin is valid,
 *         #GNUNET_NO if it is invalid
 *         #GNUNET_SYSERROR if an internal error occured
 */
int
TALER_test_coin_valid (const struct TALER_CoinPublicInfo *coin_public_info)
{
  struct GNUNET_HashCode c_hash;

  GNUNET_CRYPTO_hash (&coin_public_info->coin_pub,
                      sizeof (struct GNUNET_CRYPTO_EcdsaPublicKey),
                      &c_hash);
  if (GNUNET_OK !=
      GNUNET_CRYPTO_rsa_verify (&c_hash,
                                coin_public_info->denom_sig.rsa_signature,
                                coin_public_info->denom_pub.rsa_public_key))
  {
    GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
                "coin signature is invalid\n");
    return GNUNET_NO;
  }
  return GNUNET_YES;
}



/**
 * Decrypt the shared @a secret from the information in the
 * encrypted link secret @e secret_enc using the transfer
 * private key and the coin's public key.
 * 
 * @param secret_enc encrypted link secret
 * @param transfer_priv transfer private key
 * @param coin_pub coin public key
 * @param[out] secret set to the shared secret
 * @return #GNUNET_OK on success, #GNUNET_SYSERR on error
 */
int
TALER_link_decrypt_secret (const struct TALER_EncryptedLinkSecretP *secret_enc,
			   const struct TALER_TransferPrivateKeyP *trans_priv,
			   const union TALER_CoinSpendPublicKeyP *coin_pub,
			   struct TALER_LinkSecretP *secret)
{
  struct TALER_TransferSecretP transfer_secret;

  if (GNUNET_OK !=
      GNUNET_CRYPTO_ecc_ecdh (&trans_priv->ecdhe_priv,
			      &coin_pub->ecdhe_pub,
			      &transfer_secret.key))
  {
    GNUNET_break (0);
    return GNUNET_SYSERR;
  }
  if (GNUNET_OK !=
      TALER_transfer_decrypt (secret_enc,
			      &transfer_secret,
			      secret))
  {
    GNUNET_break (0);
    return GNUNET_SYSERR;
  }
  return GNUNET_OK;
}


/**
 * Encrypt the shared @a secret to generate the encrypted link secret.
 * Also creates the transfer key.
 * 
 * @param secret link secret to encrypt 
 * @param coin_pub coin public key
 * @param transfer_priv[out] set to transfer private key
 * @param transfer_pub[out] set to transfer public key
 * @param[out] secret_enc set to the encryptd @a secret
 * @return #GNUNET_OK on success, #GNUNET_SYSERR on error
 */
int
TALER_link_encrypt_secret (const struct TALER_LinkSecretP *secret,
			   const union TALER_CoinSpendPublicKeyP *coin_pub,
			   struct TALER_TransferPrivateKeyP *trans_priv,
			   struct TALER_TransferPublicKeyP *trans_pub,
			   struct TALER_EncryptedLinkSecretP *secret_enc)
{
  struct TALER_TransferSecretP transfer_secret;
  struct GNUNET_CRYPTO_EcdhePrivateKey *pk;

  pk = GNUNET_CRYPTO_ecdhe_key_create ();
  if (GNUNET_OK !=
      GNUNET_CRYPTO_ecc_ecdh (pk,
			      &coin_pub->ecdhe_pub,
			      &transfer_secret.key))
  {
    GNUNET_break (0);
    GNUNET_free (pk);
    return GNUNET_SYSERR;
  }
  if (GNUNET_OK !=
      TALER_transfer_encrypt (secret,
			      &transfer_secret,
			      secret_enc))
  {
    GNUNET_break (0);
    return GNUNET_SYSERR;
  }
  trans_priv->ecdhe_priv = *pk;
  GNUNET_CRYPTO_ecdhe_key_get_public (pk,
				      &trans_pub->ecdhe_pub);
  GNUNET_free (pk);
  return GNUNET_OK;
}


/* end of crypto.c */