GNUnet  0.11.x
crypto_kdf.c
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1 /*
2  This file is part of GNUnet.
3  Copyright (C) 2010 GNUnet e.V.
4 
5  GNUnet is free software: you can redistribute it and/or modify it
6  under the terms of the GNU Affero General Public License as published
7  by the Free Software Foundation, either version 3 of the License,
8  or (at your option) any later version.
9 
10  GNUnet is distributed in the hope that it will be useful, but
11  WITHOUT ANY WARRANTY; without even the implied warranty of
12  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13  Affero General Public License for more details.
14 
15  You should have received a copy of the GNU Affero General Public License
16  along with this program. If not, see <http://www.gnu.org/licenses/>.
17 
18  SPDX-License-Identifier: AGPL3.0-or-later
19  */
20 
28 #include <gcrypt.h>
29 
30 #include "platform.h"
31 #include "gnunet_crypto_lib.h"
32 
33 #define LOG(kind, ...) GNUNET_log_from (kind, "util-crypto-kdf", __VA_ARGS__)
34 
46 int
48  size_t out_len,
49  const void *xts,
50  size_t xts_len,
51  const void *skm,
52  size_t skm_len,
53  va_list argp)
54 {
55  /*
56  * "Finally, we point out to a particularly advantageous instantiation using
57  * HMAC-SHA512 as XTR and HMAC-SHA256 in PRF* (in which case the output from SHA-512 is
58  * truncated to 256 bits). This makes sense in two ways: First, the extraction part is where we need a
59  * stronger hash function due to the unconventional demand from the hash function in the extraction
60  * setting. Second, as shown in Section 6, using HMAC with a truncated output as an extractor
61  * allows to prove the security of HKDF under considerably weaker assumptions on the underlying
62  * hash function."
63  *
64  * http://eprint.iacr.org/2010/264
65  *///
66  return GNUNET_CRYPTO_hkdf_v (result,
67  out_len,
68  GCRY_MD_SHA512,
69  GCRY_MD_SHA256,
70  xts,
71  xts_len,
72  skm,
73  skm_len,
74  argp);
75 }
76 
77 
89 int
91  size_t out_len,
92  const void *xts,
93  size_t xts_len,
94  const void *skm,
95  size_t skm_len, ...)
96 {
97  va_list argp;
98  int ret;
99 
100  va_start (argp, skm_len);
101  ret = GNUNET_CRYPTO_kdf_v (result,
102  out_len,
103  xts,
104  xts_len,
105  skm,
106  skm_len,
107  argp);
108  va_end (argp);
109 
110  return ret;
111 }
112 
113 
126 void
128  gcry_mpi_t n,
129  const void *xts, size_t xts_len,
130  const void *skm, size_t skm_len,
131  const char *ctx)
132 {
133  gcry_error_t rc;
134  unsigned int nbits;
135  size_t rsize;
136  uint16_t ctr;
137 
138  nbits = gcry_mpi_get_nbits (n);
139  /* GNUNET_assert (nbits > 512); */
140 
141  ctr = 0;
142  while (1)
143  {
144  /* Ain't clear if n is always divisible by 8 */
145  uint8_t buf[ (nbits - 1) / 8 + 1 ];
146  uint16_t ctr_nbo = htons (ctr);
147 
148  rc = GNUNET_CRYPTO_kdf (buf,
149  sizeof(buf),
150  xts, xts_len,
151  skm, skm_len,
152  ctx, strlen (ctx),
153  &ctr_nbo, sizeof(ctr_nbo),
154  NULL, 0);
155  GNUNET_assert (GNUNET_YES == rc);
156 
157  rc = gcry_mpi_scan (r,
158  GCRYMPI_FMT_USG,
159  (const unsigned char *) buf,
160  sizeof(buf),
161  &rsize);
162  GNUNET_assert (0 == rc); /* Allocation error? */
163 
164  gcry_mpi_clear_highbit (*r, nbits);
165  GNUNET_assert (0 == gcry_mpi_test_bit (*r, nbits));
166  ++ctr;
167  /* We reject this FDH if either *r > n and retry with another ctr */
168  if (0 > gcry_mpi_cmp (*r, n))
169  break;
170  gcry_mpi_release (*r);
171  }
172 }
173 
174 
175 /* end of crypto_kdf.c */
#define GNUNET_assert(cond)
Use this for fatal errors that cannot be handled.
static int ret
Return value of the commandline.
Definition: gnunet-abd.c:81
static struct GNUNET_DNSSTUB_Context * ctx
Context for DNS resolution.
int GNUNET_CRYPTO_kdf_v(void *result, size_t out_len, const void *xts, size_t xts_len, const void *skm, size_t skm_len, va_list argp)
Derive key.
Definition: crypto_kdf.c:47
cryptographic primitives for GNUnet
void GNUNET_CRYPTO_kdf_mod_mpi(gcry_mpi_t *r, gcry_mpi_t n, const void *xts, size_t xts_len, const void *skm, size_t skm_len, const char *ctx)
Deterministically generate a pseudo-random number uniformly from the integers modulo a libgcrypt mpi...
Definition: crypto_kdf.c:127
int GNUNET_CRYPTO_kdf(void *result, size_t out_len, const void *xts, size_t xts_len, const void *skm, size_t skm_len,...)
Derive key.
Definition: crypto_kdf.c:90
static char buf[2048]
static int result
Global testing status.
enum GNUNET_GenericReturnValue GNUNET_CRYPTO_hkdf_v(void *result, size_t out_len, int xtr_algo, int prf_algo, const void *xts, size_t xts_len, const void *skm, size_t skm_len, va_list argp)
Derive key.
Definition: crypto_hkdf.c:144