/* Originally written by Bodo Moeller for the OpenSSL project.
* ====================================================================
* Copyright (c) 1998-2005 The OpenSSL Project. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
*
* 3. All advertising materials mentioning features or use of this
* software must display the following acknowledgment:
* "This product includes software developed by the OpenSSL Project
* for use in the OpenSSL Toolkit. (http://www.openssl.org/)"
*
* 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
* endorse or promote products derived from this software without
* prior written permission. For written permission, please contact
* openssl-core@openssl.org.
*
* 5. Products derived from this software may not be called "OpenSSL"
* nor may "OpenSSL" appear in their names without prior written
* permission of the OpenSSL Project.
*
* 6. Redistributions of any form whatsoever must retain the following
* acknowledgment:
* "This product includes software developed by the OpenSSL Project
* for use in the OpenSSL Toolkit (http://www.openssl.org/)"
*
* THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
* EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE OpenSSL PROJECT OR
* ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
* STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
* OF THE POSSIBILITY OF SUCH DAMAGE.
* ====================================================================
*
* This product includes cryptographic software written by Eric Young
* (eay@cryptsoft.com). This product includes software written by Tim
* Hudson (tjh@cryptsoft.com).
*
*/
/* ====================================================================
* Copyright 2002 Sun Microsystems, Inc. ALL RIGHTS RESERVED.
*
* Portions of the attached software ("Contribution") are developed by
* SUN MICROSYSTEMS, INC., and are contributed to the OpenSSL project.
*
* The Contribution is licensed pursuant to the OpenSSL open source
* license provided above.
*
* The elliptic curve binary polynomial software is originally written by
* Sheueling Chang Shantz and Douglas Stebila of Sun Microsystems
* Laboratories. */
#include <openssl_grpc/ec.h>
#include <openssl_grpc/bn.h>
#include <openssl_grpc/err.h>
#include "internal.h"
size_t ec_point_to_bytes(const EC_GROUP *group, const EC_AFFINE *point,
point_conversion_form_t form, uint8_t *buf,
size_t len) {
if (form != POINT_CONVERSION_COMPRESSED &&
form != POINT_CONVERSION_UNCOMPRESSED) {
OPENSSL_PUT_ERROR(EC, EC_R_INVALID_FORM);
return 0;
}
const size_t field_len = BN_num_bytes(&group->field);
size_t output_len = 1 /* type byte */ + field_len;
if (form == POINT_CONVERSION_UNCOMPRESSED) {
// Uncompressed points have a second coordinate.
output_len += field_len;
}
// if 'buf' is NULL, just return required length
if (buf != NULL) {
if (len < output_len) {
OPENSSL_PUT_ERROR(EC, EC_R_BUFFER_TOO_SMALL);
return 0;
}
size_t field_len_out;
ec_felem_to_bytes(group, buf + 1, &field_len_out, &point->X);
assert(field_len_out == field_len);
if (form == POINT_CONVERSION_UNCOMPRESSED) {
ec_felem_to_bytes(group, buf + 1 + field_len, &field_len_out, &point->Y);
assert(field_len_out == field_len);
buf[0] = form;
} else {
uint8_t y_buf[EC_MAX_BYTES];
ec_felem_to_bytes(group, y_buf, &field_len_out, &point->Y);
buf[0] = form + (y_buf[field_len_out - 1] & 1);
}
}
return output_len;
}
int ec_point_from_uncompressed(const EC_GROUP *group, EC_AFFINE *out,
const uint8_t *in, size_t len) {
const size_t field_len = BN_num_bytes(&group->field);
if (len != 1 + 2 * field_len || in[0] != POINT_CONVERSION_UNCOMPRESSED) {
OPENSSL_PUT_ERROR(EC, EC_R_INVALID_ENCODING);
return 0;
}
EC_FELEM x, y;
if (!ec_felem_from_bytes(group, &x, in + 1, field_len) ||
!ec_felem_from_bytes(group, &y, in + 1 + field_len, field_len) ||
!ec_point_set_affine_coordinates(group, out, &x, &y)) {
return 0;
}
return 1;
}
static int ec_GFp_simple_oct2point(const EC_GROUP *group, EC_POINT *point,
const uint8_t *buf, size_t len,
BN_CTX *ctx) {
if (len == 0) {
OPENSSL_PUT_ERROR(EC, EC_R_BUFFER_TOO_SMALL);
return 0;
}
point_conversion_form_t form = buf[0];
if (form == POINT_CONVERSION_UNCOMPRESSED) {
EC_AFFINE affine;
if (!ec_point_from_uncompressed(group, &affine, buf, len)) {
// In the event of an error, defend against the caller not checking the
// return value by setting a known safe value.
ec_set_to_safe_point(group, &point->raw);
return 0;
}
ec_affine_to_jacobian(group, &point->raw, &affine);
return 1;
}
const int y_bit = form & 1;
const size_t field_len = BN_num_bytes(&group->field);
form = form & ~1u;
if (form != POINT_CONVERSION_COMPRESSED ||
len != 1 /* type byte */ + field_len) {
OPENSSL_PUT_ERROR(EC, EC_R_INVALID_ENCODING);
return 0;
}
// TODO(davidben): Integrate compressed coordinates with the lower-level EC
// abstractions. This requires a way to compute square roots, which is tricky
// for primes which are not 3 (mod 4), namely P-224 and custom curves. P-224's
// prime is particularly inconvenient for compressed coordinates. See
// https://cr.yp.to/papers/sqroot.pdf
BN_CTX *new_ctx = NULL;
if (ctx == NULL) {
ctx = new_ctx = BN_CTX_new();
if (ctx == NULL) {
return 0;
}
}
int ret = 0;
BN_CTX_start(ctx);
BIGNUM *x = BN_CTX_get(ctx);
if (x == NULL || !BN_bin2bn(buf + 1, field_len, x)) {
goto err;
}
if (BN_ucmp(x, &group->field) >= 0) {
OPENSSL_PUT_ERROR(EC, EC_R_INVALID_ENCODING);
goto err;
}
if (!EC_POINT_set_compressed_coordinates_GFp(group, point, x, y_bit, ctx)) {
goto err;
}
ret = 1;
err:
BN_CTX_end(ctx);
BN_CTX_free(new_ctx);
return ret;
}
int EC_POINT_oct2point(const EC_GROUP *group, EC_POINT *point,
const uint8_t *buf, size_t len, BN_CTX *ctx) {
if (EC_GROUP_cmp(group, point->group, NULL) != 0) {
OPENSSL_PUT_ERROR(EC, EC_R_INCOMPATIBLE_OBJECTS);
return 0;
}
return ec_GFp_simple_oct2point(group, point, buf, len, ctx);
}
size_t EC_POINT_point2oct(const EC_GROUP *group, const EC_POINT *point,
point_conversion_form_t form, uint8_t *buf,
size_t len, BN_CTX *ctx) {
if (EC_GROUP_cmp(group, point->group, NULL) != 0) {
OPENSSL_PUT_ERROR(EC, EC_R_INCOMPATIBLE_OBJECTS);
return 0;
}
EC_AFFINE affine;
if (!ec_jacobian_to_affine(group, &affine, &point->raw)) {
return 0;
}
return ec_point_to_bytes(group, &affine, form, buf, len);
}
int EC_POINT_set_compressed_coordinates_GFp(const EC_GROUP *group,
EC_POINT *point, const BIGNUM *x,
int y_bit, BN_CTX *ctx) {
if (EC_GROUP_cmp(group, point->group, NULL) != 0) {
OPENSSL_PUT_ERROR(EC, EC_R_INCOMPATIBLE_OBJECTS);
return 0;
}
if (BN_is_negative(x) || BN_cmp(x, &group->field) >= 0) {
OPENSSL_PUT_ERROR(EC, EC_R_INVALID_COMPRESSED_POINT);
return 0;
}
BN_CTX *new_ctx = NULL;
int ret = 0;
ERR_clear_error();
if (ctx == NULL) {
ctx = new_ctx = BN_CTX_new();
if (ctx == NULL) {
return 0;
}
}
y_bit = (y_bit != 0);
BN_CTX_start(ctx);
BIGNUM *tmp1 = BN_CTX_get(ctx);
BIGNUM *tmp2 = BN_CTX_get(ctx);
BIGNUM *a = BN_CTX_get(ctx);
BIGNUM *b = BN_CTX_get(ctx);
BIGNUM *y = BN_CTX_get(ctx);
if (y == NULL ||
!EC_GROUP_get_curve_GFp(group, NULL, a, b, ctx)) {
goto err;
}
// Recover y. We have a Weierstrass equation
// y^2 = x^3 + a*x + b,
// so y is one of the square roots of x^3 + a*x + b.
// tmp1 := x^3
if (!BN_mod_sqr(tmp2, x, &group->field, ctx) ||
!BN_mod_mul(tmp1, tmp2, x, &group->field, ctx)) {
goto err;
}
// tmp1 := tmp1 + a*x
if (group->a_is_minus3) {
if (!bn_mod_lshift1_consttime(tmp2, x, &group->field, ctx) ||
!bn_mod_add_consttime(tmp2, tmp2, x, &group->field, ctx) ||
!bn_mod_sub_consttime(tmp1, tmp1, tmp2, &group->field, ctx)) {
goto err;
}
} else {
if (!BN_mod_mul(tmp2, a, x, &group->field, ctx) ||
!bn_mod_add_consttime(tmp1, tmp1, tmp2, &group->field, ctx)) {
goto err;
}
}
// tmp1 := tmp1 + b
if (!bn_mod_add_consttime(tmp1, tmp1, b, &group->field, ctx)) {
goto err;
}
if (!BN_mod_sqrt(y, tmp1, &group->field, ctx)) {
unsigned long err = ERR_peek_last_error();
if (ERR_GET_LIB(err) == ERR_LIB_BN &&
ERR_GET_REASON(err) == BN_R_NOT_A_SQUARE) {
ERR_clear_error();
OPENSSL_PUT_ERROR(EC, EC_R_INVALID_COMPRESSED_POINT);
} else {
OPENSSL_PUT_ERROR(EC, ERR_R_BN_LIB);
}
goto err;
}
if (y_bit != BN_is_odd(y)) {
if (BN_is_zero(y)) {
OPENSSL_PUT_ERROR(EC, EC_R_INVALID_COMPRESSION_BIT);
goto err;
}
if (!BN_usub(y, &group->field, y)) {
goto err;
}
}
if (y_bit != BN_is_odd(y)) {
OPENSSL_PUT_ERROR(EC, ERR_R_INTERNAL_ERROR);
goto err;
}
if (!EC_POINT_set_affine_coordinates_GFp(group, point, x, y, ctx)) {
goto err;
}
ret = 1;
err:
BN_CTX_end(ctx);
BN_CTX_free(new_ctx);
return ret;
}