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, const void *key, size_t key_len, const void *buf,
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, const void *xts, size_t xts_len, const void *skm,
95 size_t skm_len, void *prk)
99 ret = doHMAC (mac, xts, xts_len, skm, skm_len);
101 return GNUNET_SYSERR;
102 memcpy (prk, ret, gcry_md_get_algo_dlen (gcry_md_get_algo (mac)));
110 dump (const char *src, const void *p, unsigned int l)
114 printf ("\n%s: ", src);
115 for (i = 0; i < l; i++)
117 printf ("%2x", (int) ((const unsigned char *) p)[i]);
126 * @param result buffer for the derived key, allocated by caller
127 * @param out_len desired length of the derived key
128 * @param xtr_algo hash algorithm for the extraction phase, GCRY_MD_...
129 * @param prf_algo hash algorithm for the expansion phase, GCRY_MD_...
131 * @param xts_len length of xts
132 * @param skm source key material
133 * @param skm_len length of skm
134 * @param argp va_list of void * & size_t pairs for context chunks
135 * @return GNUNET_YES on success
138 GNUNET_CRYPTO_hkdf_v (void *result, size_t out_len, int xtr_algo, int prf_algo,
139 const void *xts, size_t xts_len, const void *skm,
140 size_t skm_len, va_list argp)
143 unsigned long i, t, d;
144 unsigned int k = gcry_md_get_algo_dlen (prf_algo);
145 unsigned int xtr_len = gcry_md_get_algo_dlen (xtr_algo);
148 gcry_md_hd_t xtr, prf;
153 return GNUNET_SYSERR;
155 if (gcry_md_open (&xtr, xtr_algo, GCRY_MD_FLAG_HMAC) != GPG_ERR_NO_ERROR)
156 return GNUNET_SYSERR;
158 if (gcry_md_open (&prf, prf_algo, GCRY_MD_FLAG_HMAC) != GPG_ERR_NO_ERROR)
161 return GNUNET_SYSERR;
164 va_copy (args, argp);
167 while (NULL != va_arg (args, void *))
168 ctx_len += va_arg (args, size_t);
172 memset (result, 0, out_len);
173 if (getPRK (xtr, xts, xts_len, skm, skm_len, prk) != GNUNET_YES)
176 dump ("PRK", prk, xtr_len);
184 size_t plain_len = k + ctx_len + 1;
185 char plain[plain_len];
190 va_copy (args, argp);
191 while ((ctx = va_arg (args, void *)))
195 len = va_arg (args, size_t);
196 memcpy (dst, ctx, len);
203 memset (plain + k + ctx_len, 1, 1);
205 dump ("K(1)", plain, plain_len);
207 hc = doHMAC (prf, prk, xtr_len, &plain[k], ctx_len + 1);
210 memcpy (result, hc, k);
215 for (i = 1; i < t; i++)
217 memcpy (plain, result - k, k);
218 memset (plain + k + ctx_len, i + 1, 1);
221 dump ("K(i+1)", plain, plain_len);
223 hc = doHMAC (prf, prk, xtr_len, plain, plain_len);
226 memcpy (result, hc, k);
235 memcpy (plain, result - k, k);
238 memset (plain + k + ctx_len, i, 1);
241 dump ("K(t):d", plain, plain_len);
244 hc = doHMAC (prf, prk, xtr_len, plain, plain_len);
246 hc = doHMAC (prf, prk, xtr_len, plain + k, plain_len - k);
249 memcpy (result, hc, d);
252 dump ("result", result - k, out_len);
270 * @param result buffer for the derived key, allocated by caller
271 * @param out_len desired length of the derived key
272 * @param xtr_algo hash algorithm for the extraction phase, GCRY_MD_...
273 * @param prf_algo hash algorithm for the expansion phase, GCRY_MD_...
275 * @param xts_len length of xts
276 * @param skm source key material
277 * @param skm_len length of skm
278 * @return GNUNET_YES on success
281 GNUNET_CRYPTO_hkdf (void *result, size_t out_len, int xtr_algo, int prf_algo,
282 const void *xts, size_t xts_len, const void *skm,
288 va_start (argp, skm_len);
290 GNUNET_CRYPTO_hkdf_v (result, out_len, xtr_algo, prf_algo, xts, xts_len,
297 /* end of crypto_hkdf.c */