2 * Copyright 2016-2018 The OpenSSL Project Authors. All Rights Reserved.
4 * Licensed under the Apache License 2.0 (the "License"). You may not use
5 * this file except in compliance with the License. You can obtain a copy
6 * in the file LICENSE in the source distribution or at
7 * https://www.openssl.org/source/license.html
13 #include <openssl/hmac.h>
14 #include <openssl/evp.h>
15 #include <openssl/kdf.h>
16 #include "internal/cryptlib.h"
17 #include "internal/numbers.h"
18 #include "internal/evp_int.h"
19 #include "kdf_local.h"
21 #define HKDF_MAXBUF 1024
23 static void kdf_hkdf_reset(EVP_KDF_IMPL
*impl
);
24 static int HKDF(const EVP_MD
*evp_md
,
25 const unsigned char *salt
, size_t salt_len
,
26 const unsigned char *key
, size_t key_len
,
27 const unsigned char *info
, size_t info_len
,
28 unsigned char *okm
, size_t okm_len
);
29 static int HKDF_Extract(const EVP_MD
*evp_md
,
30 const unsigned char *salt
, size_t salt_len
,
31 const unsigned char *ikm
, size_t ikm_len
,
32 unsigned char *prk
, size_t prk_len
);
33 static int HKDF_Expand(const EVP_MD
*evp_md
,
34 const unsigned char *prk
, size_t prk_len
,
35 const unsigned char *info
, size_t info_len
,
36 unsigned char *okm
, size_t okm_len
);
38 struct evp_kdf_impl_st
{
45 unsigned char info
[HKDF_MAXBUF
];
49 static EVP_KDF_IMPL
*kdf_hkdf_new(void)
53 if ((impl
= OPENSSL_zalloc(sizeof(*impl
))) == NULL
)
54 KDFerr(KDF_F_KDF_HKDF_NEW
, ERR_R_MALLOC_FAILURE
);
58 static void kdf_hkdf_free(EVP_KDF_IMPL
*impl
)
64 static void kdf_hkdf_reset(EVP_KDF_IMPL
*impl
)
66 OPENSSL_free(impl
->salt
);
67 OPENSSL_clear_free(impl
->key
, impl
->key_len
);
68 OPENSSL_cleanse(impl
->info
, impl
->info_len
);
69 memset(impl
, 0, sizeof(*impl
));
72 static int kdf_hkdf_ctrl(EVP_KDF_IMPL
*impl
, int cmd
, va_list args
)
74 const unsigned char *p
;
79 case EVP_KDF_CTRL_SET_MD
:
80 md
= va_arg(args
, const EVP_MD
*);
87 case EVP_KDF_CTRL_SET_HKDF_MODE
:
88 impl
->mode
= va_arg(args
, int);
91 case EVP_KDF_CTRL_SET_SALT
:
92 p
= va_arg(args
, const unsigned char *);
93 len
= va_arg(args
, size_t);
94 if (len
== 0 || p
== NULL
)
97 OPENSSL_free(impl
->salt
);
98 impl
->salt
= OPENSSL_memdup(p
, len
);
99 if (impl
->salt
== NULL
)
102 impl
->salt_len
= len
;
105 case EVP_KDF_CTRL_SET_KEY
:
106 p
= va_arg(args
, const unsigned char *);
107 len
= va_arg(args
, size_t);
108 OPENSSL_clear_free(impl
->key
, impl
->key_len
);
109 impl
->key
= OPENSSL_memdup(p
, len
);
110 if (impl
->key
== NULL
)
116 case EVP_KDF_CTRL_RESET_HKDF_INFO
:
117 OPENSSL_cleanse(impl
->info
, impl
->info_len
);
121 case EVP_KDF_CTRL_ADD_HKDF_INFO
:
122 p
= va_arg(args
, const unsigned char *);
123 len
= va_arg(args
, size_t);
124 if (len
== 0 || p
== NULL
)
127 if (len
> (HKDF_MAXBUF
- impl
->info_len
))
130 memcpy(impl
->info
+ impl
->info_len
, p
, len
);
131 impl
->info_len
+= len
;
139 static int kdf_hkdf_ctrl_str(EVP_KDF_IMPL
*impl
, const char *type
,
142 if (strcmp(type
, "mode") == 0) {
145 if (strcmp(value
, "EXTRACT_AND_EXPAND") == 0)
146 mode
= EVP_KDF_HKDF_MODE_EXTRACT_AND_EXPAND
;
147 else if (strcmp(value
, "EXTRACT_ONLY") == 0)
148 mode
= EVP_KDF_HKDF_MODE_EXTRACT_ONLY
;
149 else if (strcmp(value
, "EXPAND_ONLY") == 0)
150 mode
= EVP_KDF_HKDF_MODE_EXPAND_ONLY
;
154 return call_ctrl(kdf_hkdf_ctrl
, impl
, EVP_KDF_CTRL_SET_HKDF_MODE
, mode
);
157 if (strcmp(type
, "digest") == 0)
158 return kdf_md2ctrl(impl
, kdf_hkdf_ctrl
, EVP_KDF_CTRL_SET_MD
, value
);
160 if (strcmp(type
, "salt") == 0)
161 return kdf_str2ctrl(impl
, kdf_hkdf_ctrl
, EVP_KDF_CTRL_SET_SALT
, value
);
163 if (strcmp(type
, "hexsalt") == 0)
164 return kdf_hex2ctrl(impl
, kdf_hkdf_ctrl
, EVP_KDF_CTRL_SET_SALT
, value
);
166 if (strcmp(type
, "key") == 0)
167 return kdf_str2ctrl(impl
, kdf_hkdf_ctrl
, EVP_KDF_CTRL_SET_KEY
, value
);
169 if (strcmp(type
, "hexkey") == 0)
170 return kdf_hex2ctrl(impl
, kdf_hkdf_ctrl
, EVP_KDF_CTRL_SET_KEY
, value
);
172 if (strcmp(type
, "info") == 0)
173 return kdf_str2ctrl(impl
, kdf_hkdf_ctrl
, EVP_KDF_CTRL_ADD_HKDF_INFO
,
176 if (strcmp(type
, "hexinfo") == 0)
177 return kdf_hex2ctrl(impl
, kdf_hkdf_ctrl
, EVP_KDF_CTRL_ADD_HKDF_INFO
,
183 static size_t kdf_hkdf_size(EVP_KDF_IMPL
*impl
)
187 if (impl
->mode
!= EVP_KDF_HKDF_MODE_EXTRACT_ONLY
)
190 if (impl
->md
== NULL
) {
191 KDFerr(KDF_F_KDF_HKDF_SIZE
, KDF_R_MISSING_MESSAGE_DIGEST
);
194 sz
= EVP_MD_size(impl
->md
);
201 static int kdf_hkdf_derive(EVP_KDF_IMPL
*impl
, unsigned char *key
,
204 if (impl
->md
== NULL
) {
205 KDFerr(KDF_F_KDF_HKDF_DERIVE
, KDF_R_MISSING_MESSAGE_DIGEST
);
208 if (impl
->key
== NULL
) {
209 KDFerr(KDF_F_KDF_HKDF_DERIVE
, KDF_R_MISSING_KEY
);
213 switch (impl
->mode
) {
214 case EVP_KDF_HKDF_MODE_EXTRACT_AND_EXPAND
:
215 return HKDF(impl
->md
, impl
->salt
, impl
->salt_len
, impl
->key
,
216 impl
->key_len
, impl
->info
, impl
->info_len
, key
,
219 case EVP_KDF_HKDF_MODE_EXTRACT_ONLY
:
220 return HKDF_Extract(impl
->md
, impl
->salt
, impl
->salt_len
, impl
->key
,
221 impl
->key_len
, key
, keylen
);
223 case EVP_KDF_HKDF_MODE_EXPAND_ONLY
:
224 return HKDF_Expand(impl
->md
, impl
->key
, impl
->key_len
, impl
->info
,
225 impl
->info_len
, key
, keylen
);
232 const EVP_KDF hkdf_kdf_meth
= {
244 * Refer to "HMAC-based Extract-and-Expand Key Derivation Function (HKDF)"
245 * Section 2 (https://tools.ietf.org/html/rfc5869#section-2) and
246 * "Cryptographic Extraction and Key Derivation: The HKDF Scheme"
247 * Section 4.2 (https://eprint.iacr.org/2010/264.pdf).
250 * The scheme HKDF is specified as:
251 * HKDF(XTS, SKM, CTXinfo, L) = K(1) | K(2) | ... | K(t)
254 * SKM is source key material
255 * XTS is extractor salt (which may be null or constant)
256 * CTXinfo is context information (may be null)
257 * L is the number of key bits to be produced by KDF
258 * k is the output length in bits of the hash function used with HMAC
260 * the value K(t) is truncated to its first d = L mod k bits.
263 * 2.2. Step 1: Extract
264 * HKDF-Extract(salt, IKM) -> PRK
265 * 2.3. Step 2: Expand
266 * HKDF-Expand(PRK, info, L) -> OKM
268 static int HKDF(const EVP_MD
*evp_md
,
269 const unsigned char *salt
, size_t salt_len
,
270 const unsigned char *ikm
, size_t ikm_len
,
271 const unsigned char *info
, size_t info_len
,
272 unsigned char *okm
, size_t okm_len
)
274 unsigned char prk
[EVP_MAX_MD_SIZE
];
278 sz
= EVP_MD_size(evp_md
);
281 prk_len
= (size_t)sz
;
283 /* Step 1: HKDF-Extract(salt, IKM) -> PRK */
284 if (!HKDF_Extract(evp_md
, salt
, salt_len
, ikm
, ikm_len
, prk
, prk_len
))
287 /* Step 2: HKDF-Expand(PRK, info, L) -> OKM */
288 ret
= HKDF_Expand(evp_md
, prk
, prk_len
, info
, info_len
, okm
, okm_len
);
289 OPENSSL_cleanse(prk
, sizeof(prk
));
295 * Refer to "HMAC-based Extract-and-Expand Key Derivation Function (HKDF)"
296 * Section 2.2 (https://tools.ietf.org/html/rfc5869#section-2.2).
298 * 2.2. Step 1: Extract
300 * HKDF-Extract(salt, IKM) -> PRK
303 * Hash a hash function; HashLen denotes the length of the
304 * hash function output in octets
307 * salt optional salt value (a non-secret random value);
308 * if not provided, it is set to a string of HashLen zeros.
309 * IKM input keying material
312 * PRK a pseudorandom key (of HashLen octets)
314 * The output PRK is calculated as follows:
316 * PRK = HMAC-Hash(salt, IKM)
318 static int HKDF_Extract(const EVP_MD
*evp_md
,
319 const unsigned char *salt
, size_t salt_len
,
320 const unsigned char *ikm
, size_t ikm_len
,
321 unsigned char *prk
, size_t prk_len
)
323 int sz
= EVP_MD_size(evp_md
);
327 if (prk_len
!= (size_t)sz
) {
328 KDFerr(KDF_F_HKDF_EXTRACT
, KDF_R_WRONG_OUTPUT_BUFFER_SIZE
);
331 /* calc: PRK = HMAC-Hash(salt, IKM) */
332 return HMAC(evp_md
, salt
, salt_len
, ikm
, ikm_len
, prk
, NULL
) != NULL
;
336 * Refer to "HMAC-based Extract-and-Expand Key Derivation Function (HKDF)"
337 * Section 2.3 (https://tools.ietf.org/html/rfc5869#section-2.3).
339 * 2.3. Step 2: Expand
341 * HKDF-Expand(PRK, info, L) -> OKM
344 * Hash a hash function; HashLen denotes the length of the
345 * hash function output in octets
348 * PRK a pseudorandom key of at least HashLen octets
349 * (usually, the output from the extract step)
350 * info optional context and application specific information
351 * (can be a zero-length string)
352 * L length of output keying material in octets
356 * OKM output keying material (of L octets)
358 * The output OKM is calculated as follows:
360 * N = ceil(L/HashLen)
361 * T = T(1) | T(2) | T(3) | ... | T(N)
362 * OKM = first L octets of T
365 * T(0) = empty string (zero length)
366 * T(1) = HMAC-Hash(PRK, T(0) | info | 0x01)
367 * T(2) = HMAC-Hash(PRK, T(1) | info | 0x02)
368 * T(3) = HMAC-Hash(PRK, T(2) | info | 0x03)
371 * (where the constant concatenated to the end of each T(n) is a
374 static int HKDF_Expand(const EVP_MD
*evp_md
,
375 const unsigned char *prk
, size_t prk_len
,
376 const unsigned char *info
, size_t info_len
,
377 unsigned char *okm
, size_t okm_len
)
382 unsigned char prev
[EVP_MAX_MD_SIZE
];
383 size_t done_len
= 0, dig_len
, n
;
385 sz
= EVP_MD_size(evp_md
);
388 dig_len
= (size_t)sz
;
390 /* calc: N = ceil(L/HashLen) */
391 n
= okm_len
/ dig_len
;
392 if (okm_len
% dig_len
)
395 if (n
> 255 || okm
== NULL
)
398 if ((hmac
= HMAC_CTX_new()) == NULL
)
401 if (!HMAC_Init_ex(hmac
, prk
, prk_len
, evp_md
, NULL
))
404 for (i
= 1; i
<= n
; i
++) {
406 const unsigned char ctr
= i
;
408 /* calc: T(i) = HMAC-Hash(PRK, T(i - 1) | info | i) */
410 if (!HMAC_Init_ex(hmac
, NULL
, 0, NULL
, NULL
))
413 if (!HMAC_Update(hmac
, prev
, dig_len
))
417 if (!HMAC_Update(hmac
, info
, info_len
))
420 if (!HMAC_Update(hmac
, &ctr
, 1))
423 if (!HMAC_Final(hmac
, prev
, NULL
))
426 copy_len
= (done_len
+ dig_len
> okm_len
) ?
430 memcpy(okm
+ done_len
, prev
, copy_len
);
432 done_len
+= copy_len
;
437 OPENSSL_cleanse(prev
, sizeof(prev
));