2 * Copyright 2020-2021 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
11 * ECDH low level APIs are deprecated for public use, but still ok for
14 #include "internal/deprecated.h"
17 #include <openssl/crypto.h>
18 #include <openssl/evp.h>
19 #include <openssl/core_dispatch.h>
20 #include <openssl/core_names.h>
21 #include <openssl/ec.h>
22 #include <openssl/params.h>
23 #include <openssl/err.h>
24 #include <openssl/proverr.h>
25 #include "prov/provider_ctx.h"
26 #include "prov/providercommon.h"
27 #include "prov/implementations.h"
28 #include "prov/securitycheck.h"
29 #include "crypto/ec.h" /* ossl_ecdh_kdf_X9_63() */
31 static OSSL_FUNC_keyexch_newctx_fn ecdh_newctx;
32 static OSSL_FUNC_keyexch_init_fn ecdh_init;
33 static OSSL_FUNC_keyexch_set_peer_fn ecdh_set_peer;
34 static OSSL_FUNC_keyexch_derive_fn ecdh_derive;
35 static OSSL_FUNC_keyexch_freectx_fn ecdh_freectx;
36 static OSSL_FUNC_keyexch_dupctx_fn ecdh_dupctx;
37 static OSSL_FUNC_keyexch_set_ctx_params_fn ecdh_set_ctx_params;
38 static OSSL_FUNC_keyexch_settable_ctx_params_fn ecdh_settable_ctx_params;
39 static OSSL_FUNC_keyexch_get_ctx_params_fn ecdh_get_ctx_params;
40 static OSSL_FUNC_keyexch_gettable_ctx_params_fn ecdh_gettable_ctx_params;
43 PROV_ECDH_KDF_NONE = 0,
48 * What's passed as an actual key is defined by the KEYMGMT interface.
49 * We happen to know that our KEYMGMT simply passes EC_KEY structures, so
50 * we use that here too.
64 * . -1 use cofactor mode set for k
71 /* KDF (if any) to use for ECDH */
72 enum kdf_type kdf_type;
73 /* Message digest to use for key derivation */
75 /* User key material */
76 unsigned char *kdf_ukm;
78 /* KDF output length */
83 void *ecdh_newctx(void *provctx)
87 if (!ossl_prov_is_running())
90 pectx = OPENSSL_zalloc(sizeof(*pectx));
94 pectx->libctx = PROV_LIBCTX_OF(provctx);
95 pectx->cofactor_mode = -1;
96 pectx->kdf_type = PROV_ECDH_KDF_NONE;
102 int ecdh_init(void *vpecdhctx, void *vecdh)
104 PROV_ECDH_CTX *pecdhctx = (PROV_ECDH_CTX *)vpecdhctx;
106 if (!ossl_prov_is_running()
109 || !EC_KEY_up_ref(vecdh))
111 EC_KEY_free(pecdhctx->k);
113 pecdhctx->cofactor_mode = -1;
114 pecdhctx->kdf_type = PROV_ECDH_KDF_NONE;
115 return ossl_ec_check_key(vecdh, 1);
119 int ecdh_set_peer(void *vpecdhctx, void *vecdh)
121 PROV_ECDH_CTX *pecdhctx = (PROV_ECDH_CTX *)vpecdhctx;
123 if (!ossl_prov_is_running()
126 || !EC_KEY_up_ref(vecdh))
128 EC_KEY_free(pecdhctx->peerk);
129 pecdhctx->peerk = vecdh;
130 return ossl_ec_check_key(vecdh, 1);
134 void ecdh_freectx(void *vpecdhctx)
136 PROV_ECDH_CTX *pecdhctx = (PROV_ECDH_CTX *)vpecdhctx;
138 EC_KEY_free(pecdhctx->k);
139 EC_KEY_free(pecdhctx->peerk);
141 EVP_MD_free(pecdhctx->kdf_md);
142 OPENSSL_clear_free(pecdhctx->kdf_ukm, pecdhctx->kdf_ukmlen);
144 OPENSSL_free(pecdhctx);
148 void *ecdh_dupctx(void *vpecdhctx)
150 PROV_ECDH_CTX *srcctx = (PROV_ECDH_CTX *)vpecdhctx;
151 PROV_ECDH_CTX *dstctx;
153 if (!ossl_prov_is_running())
156 dstctx = OPENSSL_zalloc(sizeof(*srcctx));
162 /* clear all pointers */
165 dstctx->peerk = NULL;
166 dstctx->kdf_md = NULL;
167 dstctx->kdf_ukm = NULL;
169 /* up-ref all ref-counted objects referenced in dstctx */
171 if (srcctx->k != NULL && !EC_KEY_up_ref(srcctx->k))
174 dstctx->k = srcctx->k;
176 if (srcctx->peerk != NULL && !EC_KEY_up_ref(srcctx->peerk))
179 dstctx->peerk = srcctx->peerk;
181 if (srcctx->kdf_md != NULL && !EVP_MD_up_ref(srcctx->kdf_md))
184 dstctx->kdf_md = srcctx->kdf_md;
186 /* Duplicate UKM data if present */
187 if (srcctx->kdf_ukm != NULL && srcctx->kdf_ukmlen > 0) {
188 dstctx->kdf_ukm = OPENSSL_memdup(srcctx->kdf_ukm,
190 if (dstctx->kdf_ukm == NULL)
197 ecdh_freectx(dstctx);
202 int ecdh_set_ctx_params(void *vpecdhctx, const OSSL_PARAM params[])
204 char name[80] = { '\0' }; /* should be big enough */
206 PROV_ECDH_CTX *pectx = (PROV_ECDH_CTX *)vpecdhctx;
209 if (pectx == NULL || params == NULL)
212 p = OSSL_PARAM_locate_const(params, OSSL_EXCHANGE_PARAM_EC_ECDH_COFACTOR_MODE);
216 if (!OSSL_PARAM_get_int(p, &mode))
219 if (mode < -1 || mode > 1)
222 pectx->cofactor_mode = mode;
225 p = OSSL_PARAM_locate_const(params, OSSL_EXCHANGE_PARAM_KDF_TYPE);
228 if (!OSSL_PARAM_get_utf8_string(p, &str, sizeof(name)))
232 pectx->kdf_type = PROV_ECDH_KDF_NONE;
233 else if (strcmp(name, OSSL_KDF_NAME_X963KDF) == 0)
234 pectx->kdf_type = PROV_ECDH_KDF_X9_63;
239 p = OSSL_PARAM_locate_const(params, OSSL_EXCHANGE_PARAM_KDF_DIGEST);
241 char mdprops[80] = { '\0' }; /* should be big enough */
244 if (!OSSL_PARAM_get_utf8_string(p, &str, sizeof(name)))
248 p = OSSL_PARAM_locate_const(params,
249 OSSL_EXCHANGE_PARAM_KDF_DIGEST_PROPS);
252 if (!OSSL_PARAM_get_utf8_string(p, &str, sizeof(mdprops)))
256 EVP_MD_free(pectx->kdf_md);
257 pectx->kdf_md = EVP_MD_fetch(pectx->libctx, name, mdprops);
258 if (!ossl_digest_is_allowed(pectx->kdf_md)) {
259 EVP_MD_free(pectx->kdf_md);
260 pectx->kdf_md = NULL;
262 if (pectx->kdf_md == NULL)
266 p = OSSL_PARAM_locate_const(params, OSSL_EXCHANGE_PARAM_KDF_OUTLEN);
270 if (!OSSL_PARAM_get_size_t(p, &outlen))
272 pectx->kdf_outlen = outlen;
275 p = OSSL_PARAM_locate_const(params, OSSL_EXCHANGE_PARAM_KDF_UKM);
277 void *tmp_ukm = NULL;
280 if (!OSSL_PARAM_get_octet_string(p, &tmp_ukm, 0, &tmp_ukmlen))
282 OPENSSL_free(pectx->kdf_ukm);
283 pectx->kdf_ukm = tmp_ukm;
284 pectx->kdf_ukmlen = tmp_ukmlen;
290 static const OSSL_PARAM known_settable_ctx_params[] = {
291 OSSL_PARAM_int(OSSL_EXCHANGE_PARAM_EC_ECDH_COFACTOR_MODE, NULL),
292 OSSL_PARAM_utf8_string(OSSL_EXCHANGE_PARAM_KDF_TYPE, NULL, 0),
293 OSSL_PARAM_utf8_string(OSSL_EXCHANGE_PARAM_KDF_DIGEST, NULL, 0),
294 OSSL_PARAM_utf8_string(OSSL_EXCHANGE_PARAM_KDF_DIGEST_PROPS, NULL, 0),
295 OSSL_PARAM_size_t(OSSL_EXCHANGE_PARAM_KDF_OUTLEN, NULL),
296 OSSL_PARAM_octet_string(OSSL_EXCHANGE_PARAM_KDF_UKM, NULL, 0),
301 const OSSL_PARAM *ecdh_settable_ctx_params(ossl_unused void *provctx)
303 return known_settable_ctx_params;
307 int ecdh_get_ctx_params(void *vpecdhctx, OSSL_PARAM params[])
309 PROV_ECDH_CTX *pectx = (PROV_ECDH_CTX *)vpecdhctx;
312 if (pectx == NULL || params == NULL)
315 p = OSSL_PARAM_locate(params, OSSL_EXCHANGE_PARAM_EC_ECDH_COFACTOR_MODE);
317 int mode = pectx->cofactor_mode;
320 /* check what is the default for pecdhctx->k */
321 mode = EC_KEY_get_flags(pectx->k) & EC_FLAG_COFACTOR_ECDH ? 1 : 0;
324 if (!OSSL_PARAM_set_int(p, mode))
328 p = OSSL_PARAM_locate(params, OSSL_EXCHANGE_PARAM_KDF_TYPE);
330 const char *kdf_type = NULL;
332 switch (pectx->kdf_type) {
333 case PROV_ECDH_KDF_NONE:
336 case PROV_ECDH_KDF_X9_63:
337 kdf_type = OSSL_KDF_NAME_X963KDF;
343 if (!OSSL_PARAM_set_utf8_string(p, kdf_type))
347 p = OSSL_PARAM_locate(params, OSSL_EXCHANGE_PARAM_KDF_DIGEST);
349 && !OSSL_PARAM_set_utf8_string(p, pectx->kdf_md == NULL
351 : EVP_MD_name(pectx->kdf_md))){
355 p = OSSL_PARAM_locate(params, OSSL_EXCHANGE_PARAM_KDF_OUTLEN);
356 if (p != NULL && !OSSL_PARAM_set_size_t(p, pectx->kdf_outlen))
359 p = OSSL_PARAM_locate(params, OSSL_EXCHANGE_PARAM_KDF_UKM);
361 !OSSL_PARAM_set_octet_ptr(p, pectx->kdf_ukm, pectx->kdf_ukmlen))
367 static const OSSL_PARAM known_gettable_ctx_params[] = {
368 OSSL_PARAM_int(OSSL_EXCHANGE_PARAM_EC_ECDH_COFACTOR_MODE, NULL),
369 OSSL_PARAM_utf8_string(OSSL_EXCHANGE_PARAM_KDF_TYPE, NULL, 0),
370 OSSL_PARAM_utf8_string(OSSL_EXCHANGE_PARAM_KDF_DIGEST, NULL, 0),
371 OSSL_PARAM_size_t(OSSL_EXCHANGE_PARAM_KDF_OUTLEN, NULL),
372 OSSL_PARAM_DEFN(OSSL_EXCHANGE_PARAM_KDF_UKM, OSSL_PARAM_OCTET_PTR,
378 const OSSL_PARAM *ecdh_gettable_ctx_params(ossl_unused void *provctx)
380 return known_gettable_ctx_params;
384 size_t ecdh_size(const EC_KEY *k)
387 const EC_GROUP *group;
390 || (group = EC_KEY_get0_group(k)) == NULL)
393 degree = EC_GROUP_get_degree(group);
395 return (degree + 7) / 8;
399 int ecdh_plain_derive(void *vpecdhctx, unsigned char *secret,
400 size_t *psecretlen, size_t outlen)
402 PROV_ECDH_CTX *pecdhctx = (PROV_ECDH_CTX *)vpecdhctx;
404 size_t ecdhsize, size;
405 const EC_POINT *ppubkey = NULL;
406 EC_KEY *privk = NULL;
407 const EC_GROUP *group;
408 const BIGNUM *cofactor;
409 int key_cofactor_mode;
411 if (pecdhctx->k == NULL || pecdhctx->peerk == NULL) {
412 ERR_raise(ERR_LIB_PROV, PROV_R_MISSING_KEY);
416 ecdhsize = ecdh_size(pecdhctx->k);
417 if (secret == NULL) {
418 *psecretlen = ecdhsize;
422 if ((group = EC_KEY_get0_group(pecdhctx->k)) == NULL
423 || (cofactor = EC_GROUP_get0_cofactor(group)) == NULL )
427 * NB: unlike PKCS#3 DH, if outlen is less than maximum size this is not
428 * an error, the result is truncated.
430 size = outlen < ecdhsize ? outlen : ecdhsize;
433 * The ctx->cofactor_mode flag has precedence over the
434 * cofactor_mode flag set on ctx->k.
436 * - if ctx->cofactor_mode == -1, use ctx->k directly
437 * - if ctx->cofactor_mode == key_cofactor_mode, use ctx->k directly
438 * - if ctx->cofactor_mode != key_cofactor_mode:
439 * - if ctx->k->cofactor == 1, the cofactor_mode flag is irrelevant, use
441 * - if ctx->k->cofactor != 1, use a duplicate of ctx->k with the flag
442 * set to ctx->cofactor_mode
445 (EC_KEY_get_flags(pecdhctx->k) & EC_FLAG_COFACTOR_ECDH) ? 1 : 0;
446 if (pecdhctx->cofactor_mode != -1
447 && pecdhctx->cofactor_mode != key_cofactor_mode
448 && !BN_is_one(cofactor)) {
449 if ((privk = EC_KEY_dup(pecdhctx->k)) == NULL)
452 if (pecdhctx->cofactor_mode == 1)
453 EC_KEY_set_flags(privk, EC_FLAG_COFACTOR_ECDH);
455 EC_KEY_clear_flags(privk, EC_FLAG_COFACTOR_ECDH);
460 ppubkey = EC_KEY_get0_public_key(pecdhctx->peerk);
462 retlen = ECDH_compute_key(secret, size, ppubkey, privk, NULL);
467 *psecretlen = retlen;
471 if (privk != pecdhctx->k)
477 int ecdh_X9_63_kdf_derive(void *vpecdhctx, unsigned char *secret,
478 size_t *psecretlen, size_t outlen)
480 PROV_ECDH_CTX *pecdhctx = (PROV_ECDH_CTX *)vpecdhctx;
481 unsigned char *stmp = NULL;
485 if (secret == NULL) {
486 *psecretlen = pecdhctx->kdf_outlen;
490 if (pecdhctx->kdf_outlen > outlen) {
491 ERR_raise(ERR_LIB_PROV, PROV_R_OUTPUT_BUFFER_TOO_SMALL);
494 if (!ecdh_plain_derive(vpecdhctx, NULL, &stmplen, 0))
496 if ((stmp = OPENSSL_secure_malloc(stmplen)) == NULL) {
497 ERR_raise(ERR_LIB_PROV, ERR_R_MALLOC_FAILURE);
500 if (!ecdh_plain_derive(vpecdhctx, stmp, &stmplen, stmplen))
504 if (!ossl_ecdh_kdf_X9_63(secret, pecdhctx->kdf_outlen,
507 pecdhctx->kdf_ukmlen,
509 pecdhctx->libctx, NULL))
511 *psecretlen = pecdhctx->kdf_outlen;
515 OPENSSL_secure_clear_free(stmp, stmplen);
520 int ecdh_derive(void *vpecdhctx, unsigned char *secret,
521 size_t *psecretlen, size_t outlen)
523 PROV_ECDH_CTX *pecdhctx = (PROV_ECDH_CTX *)vpecdhctx;
525 switch (pecdhctx->kdf_type) {
526 case PROV_ECDH_KDF_NONE:
527 return ecdh_plain_derive(vpecdhctx, secret, psecretlen, outlen);
528 case PROV_ECDH_KDF_X9_63:
529 return ecdh_X9_63_kdf_derive(vpecdhctx, secret, psecretlen, outlen);
536 const OSSL_DISPATCH ossl_ecdh_keyexch_functions[] = {
537 { OSSL_FUNC_KEYEXCH_NEWCTX, (void (*)(void))ecdh_newctx },
538 { OSSL_FUNC_KEYEXCH_INIT, (void (*)(void))ecdh_init },
539 { OSSL_FUNC_KEYEXCH_DERIVE, (void (*)(void))ecdh_derive },
540 { OSSL_FUNC_KEYEXCH_SET_PEER, (void (*)(void))ecdh_set_peer },
541 { OSSL_FUNC_KEYEXCH_FREECTX, (void (*)(void))ecdh_freectx },
542 { OSSL_FUNC_KEYEXCH_DUPCTX, (void (*)(void))ecdh_dupctx },
543 { OSSL_FUNC_KEYEXCH_SET_CTX_PARAMS, (void (*)(void))ecdh_set_ctx_params },
544 { OSSL_FUNC_KEYEXCH_SETTABLE_CTX_PARAMS,
545 (void (*)(void))ecdh_settable_ctx_params },
546 { OSSL_FUNC_KEYEXCH_GET_CTX_PARAMS, (void (*)(void))ecdh_get_ctx_params },
547 { OSSL_FUNC_KEYEXCH_GETTABLE_CTX_PARAMS,
548 (void (*)(void))ecdh_gettable_ctx_params },