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)
39 #define LOG(kind,...) GNUNET_log_from (kind, "util", __VA_ARGS__)
42 * Set this to 0 if you compile this code outside of GNUnet.
44 #define GNUNET_BUILD 1
54 #include "gnunet_crypto_lib.h"
58 #define GNUNET_SYSERR -1
66 * @brief Compute the HMAC
67 * @todo use chunked buffers
68 * @param mac gcrypt MAC handle
70 * @param key_len length of key
71 * @param buf message to be processed
72 * @param buf_len length of buf
73 * @return HMAC, freed by caller via gcry_md_close/_reset
76 doHMAC (gcry_md_hd_t mac, const void *key, size_t key_len, const void *buf,
79 gcry_md_setkey (mac, key, key_len);
80 gcry_md_write (mac, buf, buf_len);
82 return (const void *) gcry_md_read (mac, 0);
86 * @brief Generate pseudo-random key
87 * @param mac gcrypt HMAC handle
89 * @param xts_len length of the salt
90 * @param skm source key material
91 * @param skm_len length of skm
92 * @param prk result buffer (allocated by caller; at least gcry_md_dlen() bytes)
93 * @return GNUNET_YES on success
96 getPRK (gcry_md_hd_t mac, const void *xts, size_t xts_len, const void *skm,
97 size_t skm_len, void *prk)
101 ret = doHMAC (mac, xts, xts_len, skm, skm_len);
103 return GNUNET_SYSERR;
104 memcpy (prk, ret, gcry_md_get_algo_dlen (gcry_md_get_algo (mac)));
112 dump (const char *src, const void *p, unsigned int l)
116 printf ("\n%s: ", src);
117 for (i = 0; i < l; i++)
119 printf ("%2x", (int) ((const unsigned char *) p)[i]);
128 * @param result buffer for the derived key, allocated by caller
129 * @param out_len desired length of the derived key
130 * @param xtr_algo hash algorithm for the extraction phase, GCRY_MD_...
131 * @param prf_algo hash algorithm for the expansion phase, GCRY_MD_...
133 * @param xts_len length of xts
134 * @param skm source key material
135 * @param skm_len length of skm
136 * @param argp va_list of void * & size_t pairs for context chunks
137 * @return GNUNET_YES on success
140 GNUNET_CRYPTO_hkdf_v (void *result, size_t out_len, int xtr_algo, int prf_algo,
141 const void *xts, size_t xts_len, const void *skm,
142 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, int xtr_algo, int prf_algo,
284 const void *xts, size_t xts_len, const void *skm,
290 va_start (argp, skm_len);
292 GNUNET_CRYPTO_hkdf_v (result, out_len, xtr_algo, prf_algo, xts, xts_len,
299 /* end of crypto_hkdf.c */