2 Copyright (c) 2010 Nils Durner
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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 if (gcry_md_open(&xtr, xtr_algo, GCRY_MD_FLAG_HMAC) != GPG_ERR_NO_ERROR)
165 return GNUNET_SYSERR;
167 if (gcry_md_open(&prf, prf_algo, GCRY_MD_FLAG_HMAC) != GPG_ERR_NO_ERROR)
170 return GNUNET_SYSERR;
173 va_copy (args, argp);
176 while (NULL != va_arg (args, void *))
177 ctx_len += va_arg (args, size_t);
180 memset (result, 0, out_len);
181 if (getPRK (xtr, xts, xts_len, skm, skm_len, prk)
185 dump("PRK", prk, xtr_len);
193 size_t plain_len = k + ctx_len + 1;
194 char plain[plain_len];
199 va_copy (args, argp);
200 while ((ctx = va_arg (args, void *)))
204 len = va_arg (args, size_t);
205 memcpy (dst, ctx, len);
212 memset (plain + k + ctx_len, 1, 1);
214 dump("K(1)", plain, plain_len);
218 xtr_len, &plain[k], ctx_len + 1);
221 memcpy (result, hc, k);
226 for (i = 1; i < t; i++)
228 memcpy (plain, result - k, k);
229 memset (plain + k + ctx_len, i + 1, 1);
232 dump("K(i+1)", plain, plain_len);
234 hc = doHMAC (prf, prk, xtr_len, plain, plain_len);
237 memcpy (result, hc, k);
246 memcpy (plain, result - k, k);
249 memset (plain + k + ctx_len, i, 1);
252 dump("K(t):d", plain, plain_len);
255 hc = doHMAC (prf, prk, xtr_len, plain, plain_len);
257 hc = doHMAC (prf, prk, xtr_len, plain + k, plain_len - k);
260 memcpy (result, hc, d);
263 dump("result", result - k, out_len);
281 * @param result buffer for the derived key, allocated by caller
282 * @param out_len desired length of the derived key
283 * @param xtr_algo hash algorithm for the extraction phase, GCRY_MD_...
284 * @param prf_algo hash algorithm for the expansion phase, GCRY_MD_...
286 * @param xts_len length of xts
287 * @param skm source key material
288 * @param skm_len length of skm
289 * @return GNUNET_YES on success
292 GNUNET_CRYPTO_hkdf (void *result, size_t out_len,
293 int xtr_algo, int prf_algo,
294 const void *xts, size_t xts_len,
295 const void *skm, size_t skm_len,
301 va_start(argp, skm_len);
302 ret = GNUNET_CRYPTO_hkdf_v (result, out_len, xtr_algo, prf_algo, xts,
303 xts_len, skm, skm_len, argp);
309 /* end of crypto_hkdf.c */