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openssl/providers/implementations/exchange/ecdh_exch.c

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/*
* Copyright 2020-2021 The OpenSSL Project Authors. All Rights Reserved.
*
* Licensed under the Apache License 2.0 (the "License"). You may not use
* this file except in compliance with the License. You can obtain a copy
* in the file LICENSE in the source distribution or at
* https://www.openssl.org/source/license.html
*/
/*
* ECDH low level APIs are deprecated for public use, but still ok for
* internal use.
*/
#include "internal/deprecated.h"
#include <string.h>
#include <openssl/crypto.h>
#include <openssl/evp.h>
#include <openssl/core_dispatch.h>
#include <openssl/core_names.h>
#include <openssl/ec.h>
#include <openssl/params.h>
#include <openssl/err.h>
#include <openssl/proverr.h>
#include "prov/provider_ctx.h"
#include "prov/providercommon.h"
#include "prov/implementations.h"
#include "prov/securitycheck.h"
#include "crypto/ec.h" /* ossl_ecdh_kdf_X9_63() */
static OSSL_FUNC_keyexch_newctx_fn ecdh_newctx;
static OSSL_FUNC_keyexch_init_fn ecdh_init;
static OSSL_FUNC_keyexch_set_peer_fn ecdh_set_peer;
static OSSL_FUNC_keyexch_derive_fn ecdh_derive;
static OSSL_FUNC_keyexch_freectx_fn ecdh_freectx;
static OSSL_FUNC_keyexch_dupctx_fn ecdh_dupctx;
static OSSL_FUNC_keyexch_set_ctx_params_fn ecdh_set_ctx_params;
static OSSL_FUNC_keyexch_settable_ctx_params_fn ecdh_settable_ctx_params;
static OSSL_FUNC_keyexch_get_ctx_params_fn ecdh_get_ctx_params;
static OSSL_FUNC_keyexch_gettable_ctx_params_fn ecdh_gettable_ctx_params;
enum kdf_type {
PROV_ECDH_KDF_NONE = 0,
PROV_ECDH_KDF_X9_63
};
/*
* What's passed as an actual key is defined by the KEYMGMT interface.
* We happen to know that our KEYMGMT simply passes EC_KEY structures, so
* we use that here too.
*/
typedef struct {
OSSL_LIB_CTX *libctx;
EC_KEY *k;
EC_KEY *peerk;
/*
* ECDH cofactor mode:
*
* . 0 disabled
* . 1 enabled
* . -1 use cofactor mode set for k
*/
int cofactor_mode;
/************
* ECDH KDF *
************/
/* KDF (if any) to use for ECDH */
enum kdf_type kdf_type;
/* Message digest to use for key derivation */
EVP_MD *kdf_md;
/* User key material */
unsigned char *kdf_ukm;
size_t kdf_ukmlen;
/* KDF output length */
size_t kdf_outlen;
} PROV_ECDH_CTX;
static
void *ecdh_newctx(void *provctx)
{
PROV_ECDH_CTX *pectx;
if (!ossl_prov_is_running())
return NULL;
pectx = OPENSSL_zalloc(sizeof(*pectx));
if (pectx == NULL)
return NULL;
pectx->libctx = PROV_LIBCTX_OF(provctx);
pectx->cofactor_mode = -1;
pectx->kdf_type = PROV_ECDH_KDF_NONE;
return (void *)pectx;
}
static
int ecdh_init(void *vpecdhctx, void *vecdh, const OSSL_PARAM params[])
{
PROV_ECDH_CTX *pecdhctx = (PROV_ECDH_CTX *)vpecdhctx;
if (!ossl_prov_is_running()
|| pecdhctx == NULL
|| vecdh == NULL
|| !EC_KEY_up_ref(vecdh))
return 0;
EC_KEY_free(pecdhctx->k);
pecdhctx->k = vecdh;
pecdhctx->cofactor_mode = -1;
pecdhctx->kdf_type = PROV_ECDH_KDF_NONE;
return ecdh_set_ctx_params(pecdhctx, params)
&& ossl_ec_check_key(pecdhctx->libctx, vecdh, 1);
}
static
int ecdh_match_params(const EC_KEY *priv, const EC_KEY *peer)
{
int ret;
BN_CTX *ctx = NULL;
const EC_GROUP *group_priv = EC_KEY_get0_group(priv);
const EC_GROUP *group_peer = EC_KEY_get0_group(peer);
ctx = BN_CTX_new_ex(ossl_ec_key_get_libctx(priv));
if (ctx == NULL) {
ERR_raise(ERR_LIB_PROV, ERR_R_MALLOC_FAILURE);
return 0;
}
ret = group_priv != NULL
&& group_peer != NULL
&& EC_GROUP_cmp(group_priv, group_peer, ctx) == 0;
if (!ret)
ERR_raise(ERR_LIB_PROV, PROV_R_MISMATCHING_DOMAIN_PARAMETERS);
BN_CTX_free(ctx);
return ret;
}
static
int ecdh_set_peer(void *vpecdhctx, void *vecdh)
{
PROV_ECDH_CTX *pecdhctx = (PROV_ECDH_CTX *)vpecdhctx;
if (!ossl_prov_is_running()
|| pecdhctx == NULL
|| vecdh == NULL
|| !ecdh_match_params(pecdhctx->k, vecdh)
|| !ossl_ec_check_key(pecdhctx->libctx, vecdh, 1)
|| !EC_KEY_up_ref(vecdh))
return 0;
EC_KEY_free(pecdhctx->peerk);
pecdhctx->peerk = vecdh;
return 1;
}
static
void ecdh_freectx(void *vpecdhctx)
{
PROV_ECDH_CTX *pecdhctx = (PROV_ECDH_CTX *)vpecdhctx;
EC_KEY_free(pecdhctx->k);
EC_KEY_free(pecdhctx->peerk);
EVP_MD_free(pecdhctx->kdf_md);
OPENSSL_clear_free(pecdhctx->kdf_ukm, pecdhctx->kdf_ukmlen);
OPENSSL_free(pecdhctx);
}
static
void *ecdh_dupctx(void *vpecdhctx)
{
PROV_ECDH_CTX *srcctx = (PROV_ECDH_CTX *)vpecdhctx;
PROV_ECDH_CTX *dstctx;
if (!ossl_prov_is_running())
return NULL;
dstctx = OPENSSL_zalloc(sizeof(*srcctx));
if (dstctx == NULL)
return NULL;
*dstctx = *srcctx;
/* clear all pointers */
dstctx->k= NULL;
dstctx->peerk = NULL;
dstctx->kdf_md = NULL;
dstctx->kdf_ukm = NULL;
/* up-ref all ref-counted objects referenced in dstctx */
if (srcctx->k != NULL && !EC_KEY_up_ref(srcctx->k))
goto err;
else
dstctx->k = srcctx->k;
if (srcctx->peerk != NULL && !EC_KEY_up_ref(srcctx->peerk))
goto err;
else
dstctx->peerk = srcctx->peerk;
if (srcctx->kdf_md != NULL && !EVP_MD_up_ref(srcctx->kdf_md))
goto err;
else
dstctx->kdf_md = srcctx->kdf_md;
/* Duplicate UKM data if present */
if (srcctx->kdf_ukm != NULL && srcctx->kdf_ukmlen > 0) {
dstctx->kdf_ukm = OPENSSL_memdup(srcctx->kdf_ukm,
srcctx->kdf_ukmlen);
if (dstctx->kdf_ukm == NULL)
goto err;
}
return dstctx;
err:
ecdh_freectx(dstctx);
return NULL;
}
static
int ecdh_set_ctx_params(void *vpecdhctx, const OSSL_PARAM params[])
{
char name[80] = { '\0' }; /* should be big enough */
char *str = NULL;
PROV_ECDH_CTX *pectx = (PROV_ECDH_CTX *)vpecdhctx;
const OSSL_PARAM *p;
if (pectx == NULL)
return 0;
if (params == NULL)
return 1;
p = OSSL_PARAM_locate_const(params, OSSL_EXCHANGE_PARAM_EC_ECDH_COFACTOR_MODE);
if (p != NULL) {
int mode;
if (!OSSL_PARAM_get_int(p, &mode))
return 0;
if (mode < -1 || mode > 1)
return 0;
pectx->cofactor_mode = mode;
}
p = OSSL_PARAM_locate_const(params, OSSL_EXCHANGE_PARAM_KDF_TYPE);
if (p != NULL) {
str = name;
if (!OSSL_PARAM_get_utf8_string(p, &str, sizeof(name)))
return 0;
if (name[0] == '\0')
pectx->kdf_type = PROV_ECDH_KDF_NONE;
else if (strcmp(name, OSSL_KDF_NAME_X963KDF) == 0)
pectx->kdf_type = PROV_ECDH_KDF_X9_63;
else
return 0;
}
p = OSSL_PARAM_locate_const(params, OSSL_EXCHANGE_PARAM_KDF_DIGEST);
if (p != NULL) {
char mdprops[80] = { '\0' }; /* should be big enough */
str = name;
if (!OSSL_PARAM_get_utf8_string(p, &str, sizeof(name)))
return 0;
str = mdprops;
p = OSSL_PARAM_locate_const(params,
OSSL_EXCHANGE_PARAM_KDF_DIGEST_PROPS);
if (p != NULL) {
if (!OSSL_PARAM_get_utf8_string(p, &str, sizeof(mdprops)))
return 0;
}
EVP_MD_free(pectx->kdf_md);
pectx->kdf_md = EVP_MD_fetch(pectx->libctx, name, mdprops);
if (!ossl_digest_is_allowed(pectx->libctx, pectx->kdf_md)) {
EVP_MD_free(pectx->kdf_md);
pectx->kdf_md = NULL;
}
if (pectx->kdf_md == NULL)
return 0;
}
p = OSSL_PARAM_locate_const(params, OSSL_EXCHANGE_PARAM_KDF_OUTLEN);
if (p != NULL) {
size_t outlen;
if (!OSSL_PARAM_get_size_t(p, &outlen))
return 0;
pectx->kdf_outlen = outlen;
}
p = OSSL_PARAM_locate_const(params, OSSL_EXCHANGE_PARAM_KDF_UKM);
if (p != NULL) {
void *tmp_ukm = NULL;
size_t tmp_ukmlen;
if (!OSSL_PARAM_get_octet_string(p, &tmp_ukm, 0, &tmp_ukmlen))
return 0;
OPENSSL_free(pectx->kdf_ukm);
pectx->kdf_ukm = tmp_ukm;
pectx->kdf_ukmlen = tmp_ukmlen;
}
return 1;
}
static const OSSL_PARAM known_settable_ctx_params[] = {
OSSL_PARAM_int(OSSL_EXCHANGE_PARAM_EC_ECDH_COFACTOR_MODE, NULL),
OSSL_PARAM_utf8_string(OSSL_EXCHANGE_PARAM_KDF_TYPE, NULL, 0),
OSSL_PARAM_utf8_string(OSSL_EXCHANGE_PARAM_KDF_DIGEST, NULL, 0),
OSSL_PARAM_utf8_string(OSSL_EXCHANGE_PARAM_KDF_DIGEST_PROPS, NULL, 0),
OSSL_PARAM_size_t(OSSL_EXCHANGE_PARAM_KDF_OUTLEN, NULL),
OSSL_PARAM_octet_string(OSSL_EXCHANGE_PARAM_KDF_UKM, NULL, 0),
OSSL_PARAM_END
};
static
const OSSL_PARAM *ecdh_settable_ctx_params(ossl_unused void *vpecdhctx,
ossl_unused void *provctx)
{
return known_settable_ctx_params;
}
static
int ecdh_get_ctx_params(void *vpecdhctx, OSSL_PARAM params[])
{
PROV_ECDH_CTX *pectx = (PROV_ECDH_CTX *)vpecdhctx;
OSSL_PARAM *p;
if (pectx == NULL)
return 0;
p = OSSL_PARAM_locate(params, OSSL_EXCHANGE_PARAM_EC_ECDH_COFACTOR_MODE);
if (p != NULL) {
int mode = pectx->cofactor_mode;
if (mode == -1) {
/* check what is the default for pecdhctx->k */
mode = EC_KEY_get_flags(pectx->k) & EC_FLAG_COFACTOR_ECDH ? 1 : 0;
}
if (!OSSL_PARAM_set_int(p, mode))
return 0;
}
p = OSSL_PARAM_locate(params, OSSL_EXCHANGE_PARAM_KDF_TYPE);
if (p != NULL) {
const char *kdf_type = NULL;
switch (pectx->kdf_type) {
case PROV_ECDH_KDF_NONE:
kdf_type = "";
break;
case PROV_ECDH_KDF_X9_63:
kdf_type = OSSL_KDF_NAME_X963KDF;
break;
default:
return 0;
}
if (!OSSL_PARAM_set_utf8_string(p, kdf_type))
return 0;
}
p = OSSL_PARAM_locate(params, OSSL_EXCHANGE_PARAM_KDF_DIGEST);
if (p != NULL
&& !OSSL_PARAM_set_utf8_string(p, pectx->kdf_md == NULL
? ""
: EVP_MD_name(pectx->kdf_md))){
return 0;
}
p = OSSL_PARAM_locate(params, OSSL_EXCHANGE_PARAM_KDF_OUTLEN);
if (p != NULL && !OSSL_PARAM_set_size_t(p, pectx->kdf_outlen))
return 0;
p = OSSL_PARAM_locate(params, OSSL_EXCHANGE_PARAM_KDF_UKM);
if (p != NULL &&
!OSSL_PARAM_set_octet_ptr(p, pectx->kdf_ukm, pectx->kdf_ukmlen))
return 0;
return 1;
}
static const OSSL_PARAM known_gettable_ctx_params[] = {
OSSL_PARAM_int(OSSL_EXCHANGE_PARAM_EC_ECDH_COFACTOR_MODE, NULL),
OSSL_PARAM_utf8_string(OSSL_EXCHANGE_PARAM_KDF_TYPE, NULL, 0),
OSSL_PARAM_utf8_string(OSSL_EXCHANGE_PARAM_KDF_DIGEST, NULL, 0),
OSSL_PARAM_size_t(OSSL_EXCHANGE_PARAM_KDF_OUTLEN, NULL),
OSSL_PARAM_DEFN(OSSL_EXCHANGE_PARAM_KDF_UKM, OSSL_PARAM_OCTET_PTR,
NULL, 0),
OSSL_PARAM_END
};
static
const OSSL_PARAM *ecdh_gettable_ctx_params(ossl_unused void *vpecdhctx,
ossl_unused void *provctx)
{
return known_gettable_ctx_params;
}
static ossl_inline
size_t ecdh_size(const EC_KEY *k)
{
size_t degree = 0;
const EC_GROUP *group;
if (k == NULL
|| (group = EC_KEY_get0_group(k)) == NULL)
return 0;
degree = EC_GROUP_get_degree(group);
return (degree + 7) / 8;
}
static ossl_inline
int ecdh_plain_derive(void *vpecdhctx, unsigned char *secret,
size_t *psecretlen, size_t outlen)
{
PROV_ECDH_CTX *pecdhctx = (PROV_ECDH_CTX *)vpecdhctx;
int retlen, ret = 0;
size_t ecdhsize, size;
const EC_POINT *ppubkey = NULL;
EC_KEY *privk = NULL;
const EC_GROUP *group;
const BIGNUM *cofactor;
int key_cofactor_mode;
if (pecdhctx->k == NULL || pecdhctx->peerk == NULL) {
ERR_raise(ERR_LIB_PROV, PROV_R_MISSING_KEY);
return 0;
}
ecdhsize = ecdh_size(pecdhctx->k);
if (secret == NULL) {
*psecretlen = ecdhsize;
return 1;
}
if ((group = EC_KEY_get0_group(pecdhctx->k)) == NULL
|| (cofactor = EC_GROUP_get0_cofactor(group)) == NULL )
return 0;
/*
* NB: unlike PKCS#3 DH, if outlen is less than maximum size this is not
* an error, the result is truncated.
*/
size = outlen < ecdhsize ? outlen : ecdhsize;
/*
* The ctx->cofactor_mode flag has precedence over the
* cofactor_mode flag set on ctx->k.
*
* - if ctx->cofactor_mode == -1, use ctx->k directly
* - if ctx->cofactor_mode == key_cofactor_mode, use ctx->k directly
* - if ctx->cofactor_mode != key_cofactor_mode:
* - if ctx->k->cofactor == 1, the cofactor_mode flag is irrelevant, use
* ctx->k directly
* - if ctx->k->cofactor != 1, use a duplicate of ctx->k with the flag
* set to ctx->cofactor_mode
*/
key_cofactor_mode =
(EC_KEY_get_flags(pecdhctx->k) & EC_FLAG_COFACTOR_ECDH) ? 1 : 0;
if (pecdhctx->cofactor_mode != -1
&& pecdhctx->cofactor_mode != key_cofactor_mode
&& !BN_is_one(cofactor)) {
if ((privk = EC_KEY_dup(pecdhctx->k)) == NULL)
return 0;
if (pecdhctx->cofactor_mode == 1)
EC_KEY_set_flags(privk, EC_FLAG_COFACTOR_ECDH);
else
EC_KEY_clear_flags(privk, EC_FLAG_COFACTOR_ECDH);
} else {
privk = pecdhctx->k;
}
ppubkey = EC_KEY_get0_public_key(pecdhctx->peerk);
retlen = ECDH_compute_key(secret, size, ppubkey, privk, NULL);
if (retlen <= 0)
goto end;
*psecretlen = retlen;
ret = 1;
end:
if (privk != pecdhctx->k)
EC_KEY_free(privk);
return ret;
}
static ossl_inline
int ecdh_X9_63_kdf_derive(void *vpecdhctx, unsigned char *secret,
size_t *psecretlen, size_t outlen)
{
PROV_ECDH_CTX *pecdhctx = (PROV_ECDH_CTX *)vpecdhctx;
unsigned char *stmp = NULL;
size_t stmplen;
int ret = 0;
if (secret == NULL) {
*psecretlen = pecdhctx->kdf_outlen;
return 1;
}
if (pecdhctx->kdf_outlen > outlen) {
ERR_raise(ERR_LIB_PROV, PROV_R_OUTPUT_BUFFER_TOO_SMALL);
return 0;
}
if (!ecdh_plain_derive(vpecdhctx, NULL, &stmplen, 0))
return 0;
if ((stmp = OPENSSL_secure_malloc(stmplen)) == NULL) {
ERR_raise(ERR_LIB_PROV, ERR_R_MALLOC_FAILURE);
return 0;
}
if (!ecdh_plain_derive(vpecdhctx, stmp, &stmplen, stmplen))
goto err;
/* Do KDF stuff */
if (!ossl_ecdh_kdf_X9_63(secret, pecdhctx->kdf_outlen,
stmp, stmplen,
pecdhctx->kdf_ukm,
pecdhctx->kdf_ukmlen,
pecdhctx->kdf_md,
pecdhctx->libctx, NULL))
goto err;
*psecretlen = pecdhctx->kdf_outlen;
ret = 1;
err:
OPENSSL_secure_clear_free(stmp, stmplen);
return ret;
}
static
int ecdh_derive(void *vpecdhctx, unsigned char *secret,
size_t *psecretlen, size_t outlen)
{
PROV_ECDH_CTX *pecdhctx = (PROV_ECDH_CTX *)vpecdhctx;
switch (pecdhctx->kdf_type) {
case PROV_ECDH_KDF_NONE:
return ecdh_plain_derive(vpecdhctx, secret, psecretlen, outlen);
case PROV_ECDH_KDF_X9_63:
return ecdh_X9_63_kdf_derive(vpecdhctx, secret, psecretlen, outlen);
default:
break;
}
return 0;
}
const OSSL_DISPATCH ossl_ecdh_keyexch_functions[] = {
{ OSSL_FUNC_KEYEXCH_NEWCTX, (void (*)(void))ecdh_newctx },
{ OSSL_FUNC_KEYEXCH_INIT, (void (*)(void))ecdh_init },
{ OSSL_FUNC_KEYEXCH_DERIVE, (void (*)(void))ecdh_derive },
{ OSSL_FUNC_KEYEXCH_SET_PEER, (void (*)(void))ecdh_set_peer },
{ OSSL_FUNC_KEYEXCH_FREECTX, (void (*)(void))ecdh_freectx },
{ OSSL_FUNC_KEYEXCH_DUPCTX, (void (*)(void))ecdh_dupctx },
{ OSSL_FUNC_KEYEXCH_SET_CTX_PARAMS, (void (*)(void))ecdh_set_ctx_params },
{ OSSL_FUNC_KEYEXCH_SETTABLE_CTX_PARAMS,
(void (*)(void))ecdh_settable_ctx_params },
{ OSSL_FUNC_KEYEXCH_GET_CTX_PARAMS, (void (*)(void))ecdh_get_ctx_params },
{ OSSL_FUNC_KEYEXCH_GETTABLE_CTX_PARAMS,
(void (*)(void))ecdh_gettable_ctx_params },
{ 0, NULL }
};
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