2 Copyright (c) 2010 Nils Durner
4 Permission is hereby granted, free of charge, to any person obtaining a copy
5 of this software and associated documentation files (the "Software"), to deal
6 in the Software without restriction, including without limitation the rights
7 to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
8 copies of the Software, and to permit persons to whom the Software is
9 furnished to do so, subject to the following conditions:
11 The above copyright notice and this permission notice shall be included in
12 all copies or substantial portions of the Software.
14 THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
15 IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
16 FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
17 AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
18 LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
19 OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
24 * @file src/util/crypto_hkdf.c
25 * @brief Hash-based KDF as defined in RFC 5869
26 * @see http://www.rfc-editor.org/rfc/rfc5869.txt
27 * @todo remove GNUNET references
30 * The following list of people have reviewed this code and considered
31 * it correct on the date given (if you reviewed it, please
32 * have your name added to the list):
34 * - Christian Grothoff (08.10.2010)
35 * - Nathan Evans (08.10.2010)
36 * - Matthias Wachs (08.10.2010)
40 * Set this to 0 if you compile this code outside of GNUnet.
42 #define GNUNET_BUILD 1
52 #include "gnunet_crypto_lib.h"
56 #define GNUNET_SYSERR -1
64 * @brief Compute the HMAC
65 * @todo use chunked buffers
66 * @param mac gcrypt MAC handle
68 * @param key_len length of key
69 * @param buf message to be processed
70 * @param buf_len length of buf
71 * @return HMAC, freed by caller via gcry_md_close/_reset
74 doHMAC (gcry_md_hd_t mac,
75 const void *key, size_t key_len, const void *buf, size_t buf_len)
77 gcry_md_setkey (mac, key, key_len);
78 gcry_md_write (mac, buf, buf_len);
80 return (const void *) gcry_md_read (mac, 0);
84 * @brief Generate pseudo-random key
85 * @param mac gcrypt HMAC handle
87 * @param xts_len length of the salt
88 * @param skm source key material
89 * @param skm_len length of skm
90 * @param prk result buffer (allocated by caller; at least gcry_md_dlen() bytes)
91 * @return GNUNET_YES on success
94 getPRK (gcry_md_hd_t mac,
95 const void *xts, size_t xts_len,
96 const void *skm, size_t skm_len, void *prk)
100 ret = doHMAC (mac, xts, xts_len, skm, skm_len);
102 return GNUNET_SYSERR;
103 memcpy (prk, ret, gcry_md_get_algo_dlen (gcry_md_get_algo (mac)));
111 dump (const char *src, const void *p, unsigned int l)
115 printf ("\n%s: ", src);
116 for (i = 0; i < l; i++)
118 printf ("%2x", (int) ((const unsigned char *) p)[i]);
127 * @param result buffer for the derived key, allocated by caller
128 * @param out_len desired length of the derived key
129 * @param xtr_algo hash algorithm for the extraction phase, GCRY_MD_...
130 * @param prf_algo hash algorithm for the expansion phase, GCRY_MD_...
132 * @param xts_len length of xts
133 * @param skm source key material
134 * @param skm_len length of skm
135 * @param argp va_list of void * & size_t pairs for context chunks
136 * @return GNUNET_YES on success
139 GNUNET_CRYPTO_hkdf_v (void *result, size_t out_len,
140 int xtr_algo, int prf_algo,
141 const void *xts, size_t xts_len,
142 const void *skm, size_t skm_len, va_list argp)
145 unsigned long i, t, d;
146 unsigned int k = gcry_md_get_algo_dlen (prf_algo);
147 unsigned int xtr_len = gcry_md_get_algo_dlen (xtr_algo);
150 gcry_md_hd_t xtr, prf;
155 return GNUNET_SYSERR;
157 if (gcry_md_open (&xtr, xtr_algo, GCRY_MD_FLAG_HMAC) != GPG_ERR_NO_ERROR)
158 return GNUNET_SYSERR;
160 if (gcry_md_open (&prf, prf_algo, GCRY_MD_FLAG_HMAC) != GPG_ERR_NO_ERROR)
163 return GNUNET_SYSERR;
166 va_copy (args, argp);
169 while (NULL != va_arg (args, void *))
170 ctx_len += va_arg (args, size_t);
174 memset (result, 0, out_len);
175 if (getPRK (xtr, xts, xts_len, skm, skm_len, prk) != GNUNET_YES)
178 dump ("PRK", prk, xtr_len);
186 size_t plain_len = k + ctx_len + 1;
187 char plain[plain_len];
192 va_copy (args, argp);
193 while ((ctx = va_arg (args, void *)))
197 len = va_arg (args, size_t);
198 memcpy (dst, ctx, len);
205 memset (plain + k + ctx_len, 1, 1);
207 dump ("K(1)", plain, plain_len);
209 hc = doHMAC (prf, prk, xtr_len, &plain[k], ctx_len + 1);
212 memcpy (result, hc, k);
217 for (i = 1; i < t; i++)
219 memcpy (plain, result - k, k);
220 memset (plain + k + ctx_len, i + 1, 1);
223 dump ("K(i+1)", plain, plain_len);
225 hc = doHMAC (prf, prk, xtr_len, plain, plain_len);
228 memcpy (result, hc, k);
237 memcpy (plain, result - k, k);
240 memset (plain + k + ctx_len, i, 1);
243 dump ("K(t):d", plain, plain_len);
246 hc = doHMAC (prf, prk, xtr_len, plain, plain_len);
248 hc = doHMAC (prf, prk, xtr_len, plain + k, plain_len - k);
251 memcpy (result, hc, d);
254 dump ("result", result - k, out_len);
272 * @param result buffer for the derived key, allocated by caller
273 * @param out_len desired length of the derived key
274 * @param xtr_algo hash algorithm for the extraction phase, GCRY_MD_...
275 * @param prf_algo hash algorithm for the expansion phase, GCRY_MD_...
277 * @param xts_len length of xts
278 * @param skm source key material
279 * @param skm_len length of skm
280 * @return GNUNET_YES on success
283 GNUNET_CRYPTO_hkdf (void *result, size_t out_len,
284 int xtr_algo, int prf_algo,
285 const void *xts, size_t xts_len,
286 const void *skm, size_t skm_len, ...)
291 va_start (argp, skm_len);
292 ret = GNUNET_CRYPTO_hkdf_v (result, out_len, xtr_algo, prf_algo, xts,
293 xts_len, skm, skm_len, argp);
299 /* end of crypto_hkdf.c */