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,
76 const void *buf, size_t buf_len)
78 gcry_md_setkey (mac, key, key_len);
79 gcry_md_write (mac, buf, buf_len);
81 return (const void *) gcry_md_read (mac, 0);
85 * @brief Generate pseudo-random key
86 * @param mac gcrypt HMAC handle
88 * @param xts_len length of the salt
89 * @param skm source key material
90 * @param skm_len length of skm
91 * @param prk result buffer (allocated by caller; at least gcry_md_dlen() bytes)
92 * @return GNUNET_YES on success
95 getPRK (gcry_md_hd_t mac,
96 const void *xts, size_t xts_len,
97 const void *skm, size_t skm_len,
102 ret = doHMAC (mac, xts, xts_len, skm, skm_len);
104 return GNUNET_SYSERR;
107 gcry_md_get_algo_dlen (gcry_md_get_algo (mac)));
115 dump(const char *src,
121 printf("\n%s: ", src);
122 for (i = 0; i < l; i++)
124 printf("%2x", (int) ((const unsigned char *) p)[i]);
133 * @param result buffer for the derived key, allocated by caller
134 * @param out_len desired length of the derived key
135 * @param xtr_algo hash algorithm for the extraction phase, GCRY_MD_...
136 * @param prf_algo hash algorithm for the expansion phase, GCRY_MD_...
138 * @param xts_len length of xts
139 * @param skm source key material
140 * @param skm_len length of skm
141 * @param argp va_list of void * & size_t pairs for context chunks
142 * @return GNUNET_YES on success
145 GNUNET_CRYPTO_hkdf_v (void *result, size_t out_len,
146 int xtr_algo, int prf_algo,
147 const void *xts, size_t xts_len,
148 const void *skm, size_t skm_len,
152 unsigned long i, t, d;
153 unsigned int k = gcry_md_get_algo_dlen (prf_algo);
154 unsigned int xtr_len = gcry_md_get_algo_dlen (xtr_algo);
157 gcry_md_hd_t xtr, prf;
162 return GNUNET_SYSERR;
164 // FIXME: what is the check for?
165 if (out_len > (2 ^ 32 * k))
166 return GNUNET_SYSERR;
168 if (gcry_md_open(&xtr, xtr_algo, GCRY_MD_FLAG_HMAC) != GPG_ERR_NO_ERROR)
169 return GNUNET_SYSERR;
171 if (gcry_md_open(&prf, prf_algo, GCRY_MD_FLAG_HMAC) != GPG_ERR_NO_ERROR)
174 return GNUNET_SYSERR;
177 va_copy (args, argp);
180 while (NULL != va_arg (args, void *))
181 ctx_len += va_arg (args, size_t);
184 memset (result, 0, out_len);
185 if (getPRK (xtr, xts, xts_len, skm, skm_len, prk)
189 dump("PRK", prk, xtr_len);
197 size_t plain_len = k + ctx_len + 1;
198 char plain[plain_len];
203 va_copy (args, argp);
204 while ((ctx = va_arg (args, void *)))
208 len = va_arg (args, size_t);
209 memcpy (dst, ctx, len);
216 memset (plain + k + ctx_len, 1, 1);
218 dump("K(1)", plain, plain_len);
222 xtr_len, &plain[k], ctx_len + 1);
225 memcpy (result, hc, k);
230 for (i = 1; i < t; i++)
232 memcpy (plain, result - k, k);
233 memset (plain + k + ctx_len, i + 1, 1);
236 dump("K(i+1)", plain, plain_len);
238 hc = doHMAC (prf, prk, xtr_len, plain, plain_len);
241 memcpy (result, hc, k);
249 memcpy (plain, result - k, k);
250 memset (plain + k + ctx_len, i + 1, 1);
253 dump("K(t):d", plain, plain_len);
256 hc = doHMAC (prf, prk, xtr_len, plain, plain_len);
258 hc = doHMAC (prf, prk, xtr_len, plain + k, plain_len - k);
261 memcpy (result, hc, d);
264 dump("result", result - k, out_len);
282 * @param result buffer for the derived key, allocated by caller
283 * @param out_len desired length of the derived key
284 * @param xtr_algo hash algorithm for the extraction phase, GCRY_MD_...
285 * @param prf_algo hash algorithm for the expansion phase, GCRY_MD_...
287 * @param xts_len length of xts
288 * @param skm source key material
289 * @param skm_len length of skm
290 * @param ctx context info
291 * @param ctx_len length of ctx
292 * @return GNUNET_YES on success
295 GNUNET_CRYPTO_hkdf (void *result, size_t out_len,
296 int xtr_algo, int prf_algo,
297 const void *xts, size_t xts_len,
298 const void *skm, size_t skm_len,
304 va_start(argp, skm_len);
305 ret = GNUNET_CRYPTO_hkdf_v (result, out_len, xtr_algo, prf_algo, xts,
306 xts_len, skm, skm_len, argp);
312 /* end of crypto_hkdf.c */