openssl/crypto/ec/ec_key.c

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2023-05-09 22:08:48 +00:00
/*
* Copyright 2002-2022 The OpenSSL Project Authors. All Rights Reserved.
* Copyright (c) 2002, Oracle and/or its affiliates. All rights reserved
*
* Licensed under the OpenSSL license (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
*/
#include "internal/cryptlib.h"
#include <string.h>
#include "ec_local.h"
#include "internal/refcount.h"
#include <openssl/err.h>
#include <openssl/engine.h>
#include "crypto/bn.h"
EC_KEY *EC_KEY_new(void)
{
return EC_KEY_new_method(NULL);
}
EC_KEY *EC_KEY_new_by_curve_name(int nid)
{
EC_KEY *ret = EC_KEY_new();
if (ret == NULL)
return NULL;
ret->group = EC_GROUP_new_by_curve_name(nid);
if (ret->group == NULL) {
EC_KEY_free(ret);
return NULL;
}
if (ret->meth->set_group != NULL
&& ret->meth->set_group(ret, ret->group) == 0) {
EC_KEY_free(ret);
return NULL;
}
return ret;
}
void EC_KEY_free(EC_KEY *r)
{
int i;
if (r == NULL)
return;
CRYPTO_DOWN_REF(&r->references, &i, r->lock);
REF_PRINT_COUNT("EC_KEY", r);
if (i > 0)
return;
REF_ASSERT_ISNT(i < 0);
if (r->meth != NULL && r->meth->finish != NULL)
r->meth->finish(r);
#ifndef OPENSSL_NO_ENGINE
ENGINE_finish(r->engine);
#endif
if (r->group && r->group->meth->keyfinish)
r->group->meth->keyfinish(r);
CRYPTO_free_ex_data(CRYPTO_EX_INDEX_EC_KEY, r, &r->ex_data);
CRYPTO_THREAD_lock_free(r->lock);
EC_GROUP_free(r->group);
EC_POINT_free(r->pub_key);
BN_clear_free(r->priv_key);
OPENSSL_clear_free((void *)r, sizeof(EC_KEY));
}
EC_KEY *EC_KEY_copy(EC_KEY *dest, const EC_KEY *src)
{
if (dest == NULL || src == NULL) {
ECerr(EC_F_EC_KEY_COPY, ERR_R_PASSED_NULL_PARAMETER);
return NULL;
}
if (src->meth != dest->meth) {
if (dest->meth->finish != NULL)
dest->meth->finish(dest);
if (dest->group && dest->group->meth->keyfinish)
dest->group->meth->keyfinish(dest);
#ifndef OPENSSL_NO_ENGINE
if (ENGINE_finish(dest->engine) == 0)
return 0;
dest->engine = NULL;
#endif
}
/* copy the parameters */
if (src->group != NULL) {
const EC_METHOD *meth = EC_GROUP_method_of(src->group);
/* clear the old group */
EC_GROUP_free(dest->group);
dest->group = EC_GROUP_new(meth);
if (dest->group == NULL)
return NULL;
if (!EC_GROUP_copy(dest->group, src->group))
return NULL;
/* copy the public key */
if (src->pub_key != NULL) {
EC_POINT_free(dest->pub_key);
dest->pub_key = EC_POINT_new(src->group);
if (dest->pub_key == NULL)
return NULL;
if (!EC_POINT_copy(dest->pub_key, src->pub_key))
return NULL;
}
/* copy the private key */
if (src->priv_key != NULL) {
if (dest->priv_key == NULL) {
dest->priv_key = BN_new();
if (dest->priv_key == NULL)
return NULL;
}
if (!BN_copy(dest->priv_key, src->priv_key))
return NULL;
if (src->group->meth->keycopy
&& src->group->meth->keycopy(dest, src) == 0)
return NULL;
}
}
/* copy the rest */
dest->enc_flag = src->enc_flag;
dest->conv_form = src->conv_form;
dest->version = src->version;
dest->flags = src->flags;
if (!CRYPTO_dup_ex_data(CRYPTO_EX_INDEX_EC_KEY,
&dest->ex_data, &src->ex_data))
return NULL;
if (src->meth != dest->meth) {
#ifndef OPENSSL_NO_ENGINE
if (src->engine != NULL && ENGINE_init(src->engine) == 0)
return NULL;
dest->engine = src->engine;
#endif
dest->meth = src->meth;
}
if (src->meth->copy != NULL && src->meth->copy(dest, src) == 0)
return NULL;
return dest;
}
EC_KEY *EC_KEY_dup(const EC_KEY *ec_key)
{
EC_KEY *ret = EC_KEY_new_method(ec_key->engine);
if (ret == NULL)
return NULL;
if (EC_KEY_copy(ret, ec_key) == NULL) {
EC_KEY_free(ret);
return NULL;
}
return ret;
}
int EC_KEY_up_ref(EC_KEY *r)
{
int i;
if (CRYPTO_UP_REF(&r->references, &i, r->lock) <= 0)
return 0;
REF_PRINT_COUNT("EC_KEY", r);
REF_ASSERT_ISNT(i < 2);
return ((i > 1) ? 1 : 0);
}
ENGINE *EC_KEY_get0_engine(const EC_KEY *eckey)
{
return eckey->engine;
}
int EC_KEY_generate_key(EC_KEY *eckey)
{
if (eckey == NULL || eckey->group == NULL) {
ECerr(EC_F_EC_KEY_GENERATE_KEY, ERR_R_PASSED_NULL_PARAMETER);
return 0;
}
if (eckey->meth->keygen != NULL)
return eckey->meth->keygen(eckey);
ECerr(EC_F_EC_KEY_GENERATE_KEY, EC_R_OPERATION_NOT_SUPPORTED);
return 0;
}
int ossl_ec_key_gen(EC_KEY *eckey)
{
return eckey->group->meth->keygen(eckey);
}
int ec_key_simple_generate_key(EC_KEY *eckey)
{
int ok = 0;
BN_CTX *ctx = NULL;
BIGNUM *priv_key = NULL;
const BIGNUM *order = NULL;
EC_POINT *pub_key = NULL;
if ((ctx = BN_CTX_new()) == NULL)
goto err;
if (eckey->priv_key == NULL) {
priv_key = BN_new();
if (priv_key == NULL)
goto err;
} else
priv_key = eckey->priv_key;
order = EC_GROUP_get0_order(eckey->group);
if (order == NULL)
goto err;
do
if (!BN_priv_rand_range(priv_key, order))
goto err;
while (BN_is_zero(priv_key)) ;
if (eckey->pub_key == NULL) {
pub_key = EC_POINT_new(eckey->group);
if (pub_key == NULL)
goto err;
} else
pub_key = eckey->pub_key;
if (!EC_POINT_mul(eckey->group, pub_key, priv_key, NULL, NULL, ctx))
goto err;
eckey->priv_key = priv_key;
eckey->pub_key = pub_key;
ok = 1;
err:
if (eckey->pub_key == NULL)
EC_POINT_free(pub_key);
if (eckey->priv_key != priv_key)
BN_free(priv_key);
BN_CTX_free(ctx);
return ok;
}
int ec_key_simple_generate_public_key(EC_KEY *eckey)
{
return EC_POINT_mul(eckey->group, eckey->pub_key, eckey->priv_key, NULL,
NULL, NULL);
}
int EC_KEY_check_key(const EC_KEY *eckey)
{
if (eckey == NULL || eckey->group == NULL || eckey->pub_key == NULL) {
ECerr(EC_F_EC_KEY_CHECK_KEY, ERR_R_PASSED_NULL_PARAMETER);
return 0;
}
if (eckey->group->meth->keycheck == NULL) {
ECerr(EC_F_EC_KEY_CHECK_KEY, ERR_R_SHOULD_NOT_HAVE_BEEN_CALLED);
return 0;
}
return eckey->group->meth->keycheck(eckey);
}
int ec_key_simple_check_key(const EC_KEY *eckey)
{
int ok = 0;
BN_CTX *ctx = NULL;
const BIGNUM *order = NULL;
EC_POINT *point = NULL;
if (eckey == NULL || eckey->group == NULL || eckey->pub_key == NULL) {
ECerr(EC_F_EC_KEY_SIMPLE_CHECK_KEY, ERR_R_PASSED_NULL_PARAMETER);
return 0;
}
if (EC_POINT_is_at_infinity(eckey->group, eckey->pub_key)) {
ECerr(EC_F_EC_KEY_SIMPLE_CHECK_KEY, EC_R_POINT_AT_INFINITY);
goto err;
}
if ((ctx = BN_CTX_new()) == NULL)
goto err;
if ((point = EC_POINT_new(eckey->group)) == NULL)
goto err;
/* testing whether the pub_key is on the elliptic curve */
if (EC_POINT_is_on_curve(eckey->group, eckey->pub_key, ctx) <= 0) {
ECerr(EC_F_EC_KEY_SIMPLE_CHECK_KEY, EC_R_POINT_IS_NOT_ON_CURVE);
goto err;
}
/* testing whether pub_key * order is the point at infinity */
order = eckey->group->order;
if (BN_is_zero(order)) {
ECerr(EC_F_EC_KEY_SIMPLE_CHECK_KEY, EC_R_INVALID_GROUP_ORDER);
goto err;
}
if (!EC_POINT_mul(eckey->group, point, NULL, eckey->pub_key, order, ctx)) {
ECerr(EC_F_EC_KEY_SIMPLE_CHECK_KEY, ERR_R_EC_LIB);
goto err;
}
if (!EC_POINT_is_at_infinity(eckey->group, point)) {
ECerr(EC_F_EC_KEY_SIMPLE_CHECK_KEY, EC_R_WRONG_ORDER);
goto err;
}
/*
* in case the priv_key is present : check if generator * priv_key ==
* pub_key
*/
if (eckey->priv_key != NULL) {
if (BN_cmp(eckey->priv_key, order) >= 0) {
ECerr(EC_F_EC_KEY_SIMPLE_CHECK_KEY, EC_R_WRONG_ORDER);
goto err;
}
if (!EC_POINT_mul(eckey->group, point, eckey->priv_key,
NULL, NULL, ctx)) {
ECerr(EC_F_EC_KEY_SIMPLE_CHECK_KEY, ERR_R_EC_LIB);
goto err;
}
if (EC_POINT_cmp(eckey->group, point, eckey->pub_key, ctx) != 0) {
ECerr(EC_F_EC_KEY_SIMPLE_CHECK_KEY, EC_R_INVALID_PRIVATE_KEY);
goto err;
}
}
ok = 1;
err:
BN_CTX_free(ctx);
EC_POINT_free(point);
return ok;
}
int EC_KEY_set_public_key_affine_coordinates(EC_KEY *key, BIGNUM *x,
BIGNUM *y)
{
BN_CTX *ctx = NULL;
BIGNUM *tx, *ty;
EC_POINT *point = NULL;
int ok = 0;
if (key == NULL || key->group == NULL || x == NULL || y == NULL) {
ECerr(EC_F_EC_KEY_SET_PUBLIC_KEY_AFFINE_COORDINATES,
ERR_R_PASSED_NULL_PARAMETER);
return 0;
}
ctx = BN_CTX_new();
if (ctx == NULL)
return 0;
BN_CTX_start(ctx);
point = EC_POINT_new(key->group);
if (point == NULL)
goto err;
tx = BN_CTX_get(ctx);
ty = BN_CTX_get(ctx);
if (ty == NULL)
goto err;
if (!EC_POINT_set_affine_coordinates(key->group, point, x, y, ctx))
goto err;
if (!EC_POINT_get_affine_coordinates(key->group, point, tx, ty, ctx))
goto err;
/*
* Check if retrieved coordinates match originals and are less than field
* order: if not values are out of range.
*/
if (BN_cmp(x, tx) || BN_cmp(y, ty)
|| (BN_cmp(x, key->group->field) >= 0)
|| (BN_cmp(y, key->group->field) >= 0)) {
ECerr(EC_F_EC_KEY_SET_PUBLIC_KEY_AFFINE_COORDINATES,
EC_R_COORDINATES_OUT_OF_RANGE);
goto err;
}
if (!EC_KEY_set_public_key(key, point))
goto err;
if (EC_KEY_check_key(key) == 0)
goto err;
ok = 1;
err:
BN_CTX_end(ctx);
BN_CTX_free(ctx);
EC_POINT_free(point);
return ok;
}
const EC_GROUP *EC_KEY_get0_group(const EC_KEY *key)
{
return key->group;
}
int EC_KEY_set_group(EC_KEY *key, const EC_GROUP *group)
{
if (key->meth->set_group != NULL && key->meth->set_group(key, group) == 0)
return 0;
EC_GROUP_free(key->group);
key->group = EC_GROUP_dup(group);
return (key->group == NULL) ? 0 : 1;
}
const BIGNUM *EC_KEY_get0_private_key(const EC_KEY *key)
{
return key->priv_key;
}
int EC_KEY_set_private_key(EC_KEY *key, const BIGNUM *priv_key)
{
int fixed_top;
const BIGNUM *order = NULL;
BIGNUM *tmp_key = NULL;
if (key->group == NULL || key->group->meth == NULL)
return 0;
/*
* Not only should key->group be set, but it should also be in a valid
* fully initialized state.
*
* Specifically, to operate in constant time, we need that the group order
* is set, as we use its length as the fixed public size of any scalar used
* as an EC private key.
*/
order = EC_GROUP_get0_order(key->group);
if (order == NULL || BN_is_zero(order))
return 0; /* This should never happen */
if (key->group->meth->set_private != NULL
&& key->group->meth->set_private(key, priv_key) == 0)
return 0;
if (key->meth->set_private != NULL
&& key->meth->set_private(key, priv_key) == 0)
return 0;
/*
* Return `0` to comply with legacy behavior for this function, see
* https://github.com/openssl/openssl/issues/18744#issuecomment-1195175696
*/
if (priv_key == NULL) {
BN_clear_free(key->priv_key);
key->priv_key = NULL;
return 0; /* intentional for legacy compatibility */
}
/*
* We should never leak the bit length of the secret scalar in the key,
* so we always set the `BN_FLG_CONSTTIME` flag on the internal `BIGNUM`
* holding the secret scalar.
*
* This is important also because `BN_dup()` (and `BN_copy()`) do not
* propagate the `BN_FLG_CONSTTIME` flag from the source `BIGNUM`, and
* this brings an extra risk of inadvertently losing the flag, even when
* the caller specifically set it.
*
* The propagation has been turned on and off a few times in the past
* years because in some conditions has shown unintended consequences in
* some code paths, so at the moment we can't fix this in the BN layer.
*
* In `EC_KEY_set_private_key()` we can work around the propagation by
* manually setting the flag after `BN_dup()` as we know for sure that
* inside the EC module the `BN_FLG_CONSTTIME` is always treated
* correctly and should not generate unintended consequences.
*
* Setting the BN_FLG_CONSTTIME flag alone is never enough, we also have
* to preallocate the BIGNUM internal buffer to a fixed public size big
* enough that operations performed during the processing never trigger
* a realloc which would leak the size of the scalar through memory
* accesses.
*
* Fixed Length
* ------------
*
* The order of the large prime subgroup of the curve is our choice for
* a fixed public size, as that is generally the upper bound for
* generating a private key in EC cryptosystems and should fit all valid
* secret scalars.
*
* For preallocating the BIGNUM storage we look at the number of "words"
* required for the internal representation of the order, and we
* preallocate 2 extra "words" in case any of the subsequent processing
* might temporarily overflow the order length.
*/
tmp_key = BN_dup(priv_key);
if (tmp_key == NULL)
return 0;
BN_set_flags(tmp_key, BN_FLG_CONSTTIME);
fixed_top = bn_get_top(order) + 2;
if (bn_wexpand(tmp_key, fixed_top) == NULL) {
BN_clear_free(tmp_key);
return 0;
}
BN_clear_free(key->priv_key);
key->priv_key = tmp_key;
return 1;
}
const EC_POINT *EC_KEY_get0_public_key(const EC_KEY *key)
{
return key->pub_key;
}
int EC_KEY_set_public_key(EC_KEY *key, const EC_POINT *pub_key)
{
if (key->meth->set_public != NULL
&& key->meth->set_public(key, pub_key) == 0)
return 0;
EC_POINT_free(key->pub_key);
key->pub_key = EC_POINT_dup(pub_key, key->group);
return (key->pub_key == NULL) ? 0 : 1;
}
unsigned int EC_KEY_get_enc_flags(const EC_KEY *key)
{
return key->enc_flag;
}
void EC_KEY_set_enc_flags(EC_KEY *key, unsigned int flags)
{
key->enc_flag = flags;
}
point_conversion_form_t EC_KEY_get_conv_form(const EC_KEY *key)
{
return key->conv_form;
}
void EC_KEY_set_conv_form(EC_KEY *key, point_conversion_form_t cform)
{
key->conv_form = cform;
if (key->group != NULL)
EC_GROUP_set_point_conversion_form(key->group, cform);
}
void EC_KEY_set_asn1_flag(EC_KEY *key, int flag)
{
if (key->group != NULL)
EC_GROUP_set_asn1_flag(key->group, flag);
}
int EC_KEY_precompute_mult(EC_KEY *key, BN_CTX *ctx)
{
if (key->group == NULL)
return 0;
return EC_GROUP_precompute_mult(key->group, ctx);
}
int EC_KEY_get_flags(const EC_KEY *key)
{
return key->flags;
}
void EC_KEY_set_flags(EC_KEY *key, int flags)
{
key->flags |= flags;
}
void EC_KEY_clear_flags(EC_KEY *key, int flags)
{
key->flags &= ~flags;
}
int EC_KEY_decoded_from_explicit_params(const EC_KEY *key)
{
if (key == NULL || key->group == NULL)
return -1;
return key->group->decoded_from_explicit_params;
}
size_t EC_KEY_key2buf(const EC_KEY *key, point_conversion_form_t form,
unsigned char **pbuf, BN_CTX *ctx)
{
if (key == NULL || key->pub_key == NULL || key->group == NULL)
return 0;
return EC_POINT_point2buf(key->group, key->pub_key, form, pbuf, ctx);
}
int EC_KEY_oct2key(EC_KEY *key, const unsigned char *buf, size_t len,
BN_CTX *ctx)
{
if (key == NULL || key->group == NULL)
return 0;
if (key->pub_key == NULL)
key->pub_key = EC_POINT_new(key->group);
if (key->pub_key == NULL)
return 0;
if (EC_POINT_oct2point(key->group, key->pub_key, buf, len, ctx) == 0)
return 0;
/*
* Save the point conversion form.
* For non-custom curves the first octet of the buffer (excluding
* the last significant bit) contains the point conversion form.
* EC_POINT_oct2point() has already performed sanity checking of
* the buffer so we know it is valid.
*/
if ((key->group->meth->flags & EC_FLAGS_CUSTOM_CURVE) == 0)
key->conv_form = (point_conversion_form_t)(buf[0] & ~0x01);
return 1;
}
size_t EC_KEY_priv2oct(const EC_KEY *eckey,
unsigned char *buf, size_t len)
{
if (eckey->group == NULL || eckey->group->meth == NULL)
return 0;
if (eckey->group->meth->priv2oct == NULL) {
ECerr(EC_F_EC_KEY_PRIV2OCT, ERR_R_SHOULD_NOT_HAVE_BEEN_CALLED);
return 0;
}
return eckey->group->meth->priv2oct(eckey, buf, len);
}
size_t ec_key_simple_priv2oct(const EC_KEY *eckey,
unsigned char *buf, size_t len)
{
size_t buf_len;
buf_len = (EC_GROUP_order_bits(eckey->group) + 7) / 8;
if (eckey->priv_key == NULL)
return 0;
if (buf == NULL)
return buf_len;
else if (len < buf_len)
return 0;
/* Octetstring may need leading zeros if BN is to short */
if (BN_bn2binpad(eckey->priv_key, buf, buf_len) == -1) {
ECerr(EC_F_EC_KEY_SIMPLE_PRIV2OCT, EC_R_BUFFER_TOO_SMALL);
return 0;
}
return buf_len;
}
int EC_KEY_oct2priv(EC_KEY *eckey, const unsigned char *buf, size_t len)
{
if (eckey->group == NULL || eckey->group->meth == NULL)
return 0;
if (eckey->group->meth->oct2priv == NULL) {
ECerr(EC_F_EC_KEY_OCT2PRIV, ERR_R_SHOULD_NOT_HAVE_BEEN_CALLED);
return 0;
}
return eckey->group->meth->oct2priv(eckey, buf, len);
}
int ec_key_simple_oct2priv(EC_KEY *eckey, const unsigned char *buf, size_t len)
{
if (eckey->priv_key == NULL)
eckey->priv_key = BN_secure_new();
if (eckey->priv_key == NULL) {
ECerr(EC_F_EC_KEY_SIMPLE_OCT2PRIV, ERR_R_MALLOC_FAILURE);
return 0;
}
if (BN_bin2bn(buf, len, eckey->priv_key) == NULL) {
ECerr(EC_F_EC_KEY_SIMPLE_OCT2PRIV, ERR_R_BN_LIB);
return 0;
}
return 1;
}
size_t EC_KEY_priv2buf(const EC_KEY *eckey, unsigned char **pbuf)
{
size_t len;
unsigned char *buf;
len = EC_KEY_priv2oct(eckey, NULL, 0);
if (len == 0)
return 0;
if ((buf = OPENSSL_malloc(len)) == NULL) {
ECerr(EC_F_EC_KEY_PRIV2BUF, ERR_R_MALLOC_FAILURE);
return 0;
}
len = EC_KEY_priv2oct(eckey, buf, len);
if (len == 0) {
OPENSSL_free(buf);
return 0;
}
*pbuf = buf;
return len;
}
int EC_KEY_can_sign(const EC_KEY *eckey)
{
if (eckey->group == NULL || eckey->group->meth == NULL
|| (eckey->group->meth->flags & EC_FLAGS_NO_SIGN))
return 0;
return 1;
}