kris/boringssl
1
0
Fork 0
Code Issues Pull Requests Releases Wiki Activity
150ad30d28
boringssl/crypto/fipsmodule/ec/simple.c
David Benjamin 6f564afbdd Make BN_mod_*_quick constant-time. 
As the EC code will ultimately want to use these in "words" form by way
of EC_FELEM, and because it's much easier, I've implement these as
low-level words-based functions that require all inputs have the same
width. The BIGNUM versions which RSA and, for now, EC calls are
implemented on top of that.

Unfortunately, doing such things in constant-time and accounting for
undersized inputs requires some scratch space, and these functions don't
take BN_CTX. So I've added internal bn_mod_*_quick_ctx functions that
take a BN_CTX and the old functions now allocate a bit unnecessarily.
RSA only needs lshift (for BN_MONT_CTX) and sub (for CRT), but the
generic EC code wants add as well.

The generic EC code isn't even remotely constant-time, and I hope to
ultimately use stack-allocated EC_FELEMs, so I've made the actual
implementations here implemented in "words", which is much simpler
anyway due to not having to take care of widths.

I've also gone ahead and switched the EC code to these functions,
largely as a test of their performance (an earlier iteration made the EC
code noticeably slower). These operations are otherwise not
performance-critical in RSA.

The conversion from BIGNUM to BIGNUM+BN_CTX should be dropped by the
static linker already, and the unused BIGNUM+BN_CTX functions will fall
off when EC_FELEM happens.

Update-Note: BN_mod_*_quick bounce on malloc a bit now, but they're not
    really used externally. The one caller I found was wpa_supplicant
    which bounces on malloc already. They appear to be implementing
    compressed coordinates by hand? We may be able to convince them to
    call EC_POINT_set_compressed_coordinates_GFp.

Bug: 233, 236
Change-Id: I2bf361e9c089e0211b97d95523dbc06f1168e12b
Reviewed-on: https://boringssl-review.googlesource.com/25261
Commit-Queue: David Benjamin <davidben@google.com>
CQ-Verified: CQ bot account: commit-bot@chromium.org <commit-bot@chromium.org>
Reviewed-by: Adam Langley <agl@google.com>
2018-02-06 01:16:04 +00:00

1047 lines
27 KiB
C
Raw Blame History

/* 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/ec.h>
#include <string.h>
#include <openssl/bn.h>
#include <openssl/err.h>
#include <openssl/mem.h>
#include "internal.h"
#include "../../internal.h"
// Most method functions in this file are designed to work with non-trivial
// representations of field elements if necessary (see ecp_mont.c): while
// standard modular addition and subtraction are used, the field_mul and
// field_sqr methods will be used for multiplication, and field_encode and
// field_decode (if defined) will be used for converting between
// representations.
//
// Functions here specifically assume that if a non-trivial representation is
// used, it is a Montgomery representation (i.e. 'encoding' means multiplying
// by some factor R).
int ec_GFp_simple_group_init(EC_GROUP *group) {
BN_init(&group->field);
BN_init(&group->a);
BN_init(&group->b);
BN_init(&group->one);
group->a_is_minus3 = 0;
return 1;
}
void ec_GFp_simple_group_finish(EC_GROUP *group) {
BN_free(&group->field);
BN_free(&group->a);
BN_free(&group->b);
BN_free(&group->one);
}
int ec_GFp_simple_group_set_curve(EC_GROUP *group, const BIGNUM *p,
const BIGNUM *a, const BIGNUM *b,
BN_CTX *ctx) {
int ret = 0;
BN_CTX *new_ctx = NULL;
BIGNUM *tmp_a;
// p must be a prime > 3
if (BN_num_bits(p) <= 2 || !BN_is_odd(p)) {
OPENSSL_PUT_ERROR(EC, EC_R_INVALID_FIELD);
return 0;
}
if (ctx == NULL) {
ctx = new_ctx = BN_CTX_new();
if (ctx == NULL) {
return 0;
}
}
BN_CTX_start(ctx);
tmp_a = BN_CTX_get(ctx);
if (tmp_a == NULL) {
goto err;
}
// group->field
if (!BN_copy(&group->field, p)) {
goto err;
}
BN_set_negative(&group->field, 0);
// Store the field in minimal form, so it can be used with |BN_ULONG| arrays.
bn_set_minimal_width(&group->field);
// group->a
if (!BN_nnmod(tmp_a, a, &group->field, ctx)) {
goto err;
}
if (group->meth->field_encode) {
if (!group->meth->field_encode(group, &group->a, tmp_a, ctx)) {
goto err;
}
} else if (!BN_copy(&group->a, tmp_a)) {
goto err;
}
// group->b
if (!BN_nnmod(&group->b, b, &group->field, ctx)) {
goto err;
}
if (group->meth->field_encode &&
!group->meth->field_encode(group, &group->b, &group->b, ctx)) {
goto err;
}
// group->a_is_minus3
if (!BN_add_word(tmp_a, 3)) {
goto err;
}
group->a_is_minus3 = (0 == BN_cmp(tmp_a, &group->field));
if (group->meth->field_encode != NULL) {
if (!group->meth->field_encode(group, &group->one, BN_value_one(), ctx)) {
goto err;
}
} else if (!BN_copy(&group->one, BN_value_one())) {
goto err;
}
ret = 1;
err:
BN_CTX_end(ctx);
BN_CTX_free(new_ctx);
return ret;
}
int ec_GFp_simple_group_get_curve(const EC_GROUP *group, BIGNUM *p, BIGNUM *a,
BIGNUM *b, BN_CTX *ctx) {
int ret = 0;
BN_CTX *new_ctx = NULL;
if (p != NULL && !BN_copy(p, &group->field)) {
return 0;
}
if (a != NULL || b != NULL) {
if (group->meth->field_decode) {
if (ctx == NULL) {
ctx = new_ctx = BN_CTX_new();
if (ctx == NULL) {
return 0;
}
}
if (a != NULL && !group->meth->field_decode(group, a, &group->a, ctx)) {
goto err;
}
if (b != NULL && !group->meth->field_decode(group, b, &group->b, ctx)) {
goto err;
}
} else {
if (a != NULL && !BN_copy(a, &group->a)) {
goto err;
}
if (b != NULL && !BN_copy(b, &group->b)) {
goto err;
}
}
}
ret = 1;
err:
BN_CTX_free(new_ctx);
return ret;
}
unsigned ec_GFp_simple_group_get_degree(const EC_GROUP *group) {
return BN_num_bits(&group->field);
}
int ec_GFp_simple_point_init(EC_POINT *point) {
BN_init(&point->X);
BN_init(&point->Y);
BN_init(&point->Z);
return 1;
}
void ec_GFp_simple_point_finish(EC_POINT *point) {
BN_free(&point->X);
BN_free(&point->Y);
BN_free(&point->Z);
}
int ec_GFp_simple_point_copy(EC_POINT *dest, const EC_POINT *src) {
if (!BN_copy(&dest->X, &src->X) ||
!BN_copy(&dest->Y, &src->Y) ||
!BN_copy(&dest->Z, &src->Z)) {
return 0;
}
return 1;
}
int ec_GFp_simple_point_set_to_infinity(const EC_GROUP *group,
EC_POINT *point) {
BN_zero(&point->Z);
return 1;
}
static int set_Jprojective_coordinate_GFp(const EC_GROUP *group, BIGNUM *out,
const BIGNUM *in, BN_CTX *ctx) {
if (in == NULL) {
return 1;
}
if (BN_is_negative(in) ||
BN_cmp(in, &group->field) >= 0) {
OPENSSL_PUT_ERROR(EC, EC_R_COORDINATES_OUT_OF_RANGE);
return 0;
}
if (group->meth->field_encode) {
return group->meth->field_encode(group, out, in, ctx);
}
return BN_copy(out, in) != NULL;
}
int ec_GFp_simple_point_set_affine_coordinates(const EC_GROUP *group,
EC_POINT *point, const BIGNUM *x,
const BIGNUM *y, BN_CTX *ctx) {
if (x == NULL || y == NULL) {
OPENSSL_PUT_ERROR(EC, ERR_R_PASSED_NULL_PARAMETER);
return 0;
}
BN_CTX *new_ctx = NULL;
int ret = 0;
if (ctx == NULL) {
ctx = new_ctx = BN_CTX_new();
if (ctx == NULL) {
return 0;
}
}
if (!set_Jprojective_coordinate_GFp(group, &point->X, x, ctx) ||
!set_Jprojective_coordinate_GFp(group, &point->Y, y, ctx) ||
!BN_copy(&point->Z, &group->one)) {
goto err;
}
ret = 1;
err:
BN_CTX_free(new_ctx);
return ret;
}
int ec_GFp_simple_add(const EC_GROUP *group, EC_POINT *r, const EC_POINT *a,
const EC_POINT *b, BN_CTX *ctx) {
int (*field_mul)(const EC_GROUP *, BIGNUM *, const BIGNUM *, const BIGNUM *,
BN_CTX *);
int (*field_sqr)(const EC_GROUP *, BIGNUM *, const BIGNUM *, BN_CTX *);
const BIGNUM *p;
BN_CTX *new_ctx = NULL;
BIGNUM *n0, *n1, *n2, *n3, *n4, *n5, *n6;
int ret = 0;
if (a == b) {
return EC_POINT_dbl(group, r, a, ctx);
}
if (EC_POINT_is_at_infinity(group, a)) {
return EC_POINT_copy(r, b);
}
if (EC_POINT_is_at_infinity(group, b)) {
return EC_POINT_copy(r, a);
}
field_mul = group->meth->field_mul;
field_sqr = group->meth->field_sqr;
p = &group->field;
if (ctx == NULL) {
ctx = new_ctx = BN_CTX_new();
if (ctx == NULL) {
return 0;
}
}
BN_CTX_start(ctx);
n0 = BN_CTX_get(ctx);
n1 = BN_CTX_get(ctx);
n2 = BN_CTX_get(ctx);
n3 = BN_CTX_get(ctx);
n4 = BN_CTX_get(ctx);
n5 = BN_CTX_get(ctx);
n6 = BN_CTX_get(ctx);
if (n6 == NULL) {
goto end;
}
// Note that in this function we must not read components of 'a' or 'b'
// once we have written the corresponding components of 'r'.
// ('r' might be one of 'a' or 'b'.)
// n1, n2
int b_Z_is_one = BN_cmp(&b->Z, &group->one) == 0;
if (b_Z_is_one) {
if (!BN_copy(n1, &a->X) || !BN_copy(n2, &a->Y)) {
goto end;
}
// n1 = X_a
// n2 = Y_a
} else {
if (!field_sqr(group, n0, &b->Z, ctx) ||
!field_mul(group, n1, &a->X, n0, ctx)) {
goto end;
}
// n1 = X_a * Z_b^2
if (!field_mul(group, n0, n0, &b->Z, ctx) ||
!field_mul(group, n2, &a->Y, n0, ctx)) {
goto end;
}
// n2 = Y_a * Z_b^3
}
// n3, n4
int a_Z_is_one = BN_cmp(&a->Z, &group->one) == 0;
if (a_Z_is_one) {
if (!BN_copy(n3, &b->X) || !BN_copy(n4, &b->Y)) {
goto end;
}
// n3 = X_b
// n4 = Y_b
} else {
if (!field_sqr(group, n0, &a->Z, ctx) ||
!field_mul(group, n3, &b->X, n0, ctx)) {
goto end;
}
// n3 = X_b * Z_a^2
if (!field_mul(group, n0, n0, &a->Z, ctx) ||
!field_mul(group, n4, &b->Y, n0, ctx)) {
goto end;
}
// n4 = Y_b * Z_a^3
}
// n5, n6
if (!bn_mod_sub_quick_ctx(n5, n1, n3, p, ctx) ||
!bn_mod_sub_quick_ctx(n6, n2, n4, p, ctx)) {
goto end;
}
// n5 = n1 - n3
// n6 = n2 - n4
if (BN_is_zero(n5)) {
if (BN_is_zero(n6)) {
// a is the same point as b
BN_CTX_end(ctx);
ret = EC_POINT_dbl(group, r, a, ctx);
ctx = NULL;
goto end;
} else {
// a is the inverse of b
BN_zero(&r->Z);
ret = 1;
goto end;
}
}
// 'n7', 'n8'
if (!bn_mod_add_quick_ctx(n1, n1, n3, p, ctx) ||
!bn_mod_add_quick_ctx(n2, n2, n4, p, ctx)) {
goto end;
}
// 'n7' = n1 + n3
// 'n8' = n2 + n4
// Z_r
if (a_Z_is_one && b_Z_is_one) {
if (!BN_copy(&r->Z, n5)) {
goto end;
}
} else {
if (a_Z_is_one) {
if (!BN_copy(n0, &b->Z)) {
goto end;
}
} else if (b_Z_is_one) {
if (!BN_copy(n0, &a->Z)) {
goto end;
}
} else if (!field_mul(group, n0, &a->Z, &b->Z, ctx)) {
goto end;
}
if (!field_mul(group, &r->Z, n0, n5, ctx)) {
goto end;
}
}
// Z_r = Z_a * Z_b * n5
// X_r
if (!field_sqr(group, n0, n6, ctx) ||
!field_sqr(group, n4, n5, ctx) ||
!field_mul(group, n3, n1, n4, ctx) ||
!bn_mod_sub_quick_ctx(&r->X, n0, n3, p, ctx)) {
goto end;
}
// X_r = n6^2 - n5^2 * 'n7'
// 'n9'
if (!bn_mod_lshift1_quick_ctx(n0, &r->X, p, ctx) ||
!bn_mod_sub_quick_ctx(n0, n3, n0, p, ctx)) {
goto end;
}
// n9 = n5^2 * 'n7' - 2 * X_r
// Y_r
if (!field_mul(group, n0, n0, n6, ctx) ||
!field_mul(group, n5, n4, n5, ctx)) {
goto end; // now n5 is n5^3
}
if (!field_mul(group, n1, n2, n5, ctx) ||
!bn_mod_sub_quick_ctx(n0, n0, n1, p, ctx)) {
goto end;
}
if (BN_is_odd(n0) && !BN_add(n0, n0, p)) {
goto end;
}
// now 0 <= n0 < 2*p, and n0 is even
if (!BN_rshift1(&r->Y, n0)) {
goto end;
}
// Y_r = (n6 * 'n9' - 'n8' * 'n5^3') / 2
ret = 1;
end:
if (ctx) {
// otherwise we already called BN_CTX_end
BN_CTX_end(ctx);
}
BN_CTX_free(new_ctx);
return ret;
}
int ec_GFp_simple_dbl(const EC_GROUP *group, EC_POINT *r, const EC_POINT *a,
BN_CTX *ctx) {
int (*field_mul)(const EC_GROUP *, BIGNUM *, const BIGNUM *, const BIGNUM *,
BN_CTX *);
int (*field_sqr)(const EC_GROUP *, BIGNUM *, const BIGNUM *, BN_CTX *);
const BIGNUM *p;
BN_CTX *new_ctx = NULL;
BIGNUM *n0, *n1, *n2, *n3;
int ret = 0;
if (EC_POINT_is_at_infinity(group, a)) {
BN_zero(&r->Z);
return 1;
}
field_mul = group->meth->field_mul;
field_sqr = group->meth->field_sqr;
p = &group->field;
if (ctx == NULL) {
ctx = new_ctx = BN_CTX_new();
if (ctx == NULL) {
return 0;
}
}
BN_CTX_start(ctx);
n0 = BN_CTX_get(ctx);
n1 = BN_CTX_get(ctx);
n2 = BN_CTX_get(ctx);
n3 = BN_CTX_get(ctx);
if (n3 == NULL) {
goto err;
}
// Note that in this function we must not read components of 'a'
// once we have written the corresponding components of 'r'.
// ('r' might the same as 'a'.)
// n1
if (BN_cmp(&a->Z, &group->one) == 0) {
if (!field_sqr(group, n0, &a->X, ctx) ||
!bn_mod_lshift1_quick_ctx(n1, n0, p, ctx) ||
!bn_mod_add_quick_ctx(n0, n0, n1, p, ctx) ||
!bn_mod_add_quick_ctx(n1, n0, &group->a, p, ctx)) {
goto err;
}
// n1 = 3 * X_a^2 + a_curve
} else if (group->a_is_minus3) {
if (!field_sqr(group, n1, &a->Z, ctx) ||
!bn_mod_add_quick_ctx(n0, &a->X, n1, p, ctx) ||
!bn_mod_sub_quick_ctx(n2, &a->X, n1, p, ctx) ||
!field_mul(group, n1, n0, n2, ctx) ||
!bn_mod_lshift1_quick_ctx(n0, n1, p, ctx) ||
!bn_mod_add_quick_ctx(n1, n0, n1, p, ctx)) {
goto err;
}
// n1 = 3 * (X_a + Z_a^2) * (X_a - Z_a^2)
// = 3 * X_a^2 - 3 * Z_a^4
} else {
if (!field_sqr(group, n0, &a->X, ctx) ||
!bn_mod_lshift1_quick_ctx(n1, n0, p, ctx) ||
!bn_mod_add_quick_ctx(n0, n0, n1, p, ctx) ||
!field_sqr(group, n1, &a->Z, ctx) ||
!field_sqr(group, n1, n1, ctx) ||
!field_mul(group, n1, n1, &group->a, ctx) ||
!bn_mod_add_quick_ctx(n1, n1, n0, p, ctx)) {
goto err;
}
// n1 = 3 * X_a^2 + a_curve * Z_a^4
}
// Z_r
if (BN_cmp(&a->Z, &group->one) == 0) {
if (!BN_copy(n0, &a->Y)) {
goto err;
}
} else if (!field_mul(group, n0, &a->Y, &a->Z, ctx)) {
goto err;
}
if (!bn_mod_lshift1_quick_ctx(&r->Z, n0, p, ctx)) {
goto err;
}
// Z_r = 2 * Y_a * Z_a
// n2
if (!field_sqr(group, n3, &a->Y, ctx) ||
!field_mul(group, n2, &a->X, n3, ctx) ||
!bn_mod_lshift_quick_ctx(n2, n2, 2, p, ctx)) {
goto err;
}
// n2 = 4 * X_a * Y_a^2
// X_r
if (!bn_mod_lshift1_quick_ctx(n0, n2, p, ctx) ||
!field_sqr(group, &r->X, n1, ctx) ||
!bn_mod_sub_quick_ctx(&r->X, &r->X, n0, p, ctx)) {
goto err;
}
// X_r = n1^2 - 2 * n2
// n3
if (!field_sqr(group, n0, n3, ctx) ||
!bn_mod_lshift_quick_ctx(n3, n0, 3, p, ctx)) {
goto err;
}
// n3 = 8 * Y_a^4
// Y_r
if (!bn_mod_sub_quick_ctx(n0, n2, &r->X, p, ctx) ||
!field_mul(group, n0, n1, n0, ctx) ||
!bn_mod_sub_quick_ctx(&r->Y, n0, n3, p, ctx)) {
goto err;
}
// Y_r = n1 * (n2 - X_r) - n3
ret = 1;
err:
BN_CTX_end(ctx);
BN_CTX_free(new_ctx);
return ret;
}
int ec_GFp_simple_invert(const EC_GROUP *group, EC_POINT *point, BN_CTX *ctx) {
if (EC_POINT_is_at_infinity(group, point) || BN_is_zero(&point->Y)) {
// point is its own inverse
return 1;
}
return BN_usub(&point->Y, &group->field, &point->Y);
}
int ec_GFp_simple_is_at_infinity(const EC_GROUP *group, const EC_POINT *point) {
return BN_is_zero(&point->Z);
}
int ec_GFp_simple_is_on_curve(const EC_GROUP *group, const EC_POINT *point,
BN_CTX *ctx) {
int (*field_mul)(const EC_GROUP *, BIGNUM *, const BIGNUM *, const BIGNUM *,
BN_CTX *);
int (*field_sqr)(const EC_GROUP *, BIGNUM *, const BIGNUM *, BN_CTX *);
const BIGNUM *p;
BN_CTX *new_ctx = NULL;
BIGNUM *rh, *tmp, *Z4, *Z6;
int ret = 0;
if (EC_POINT_is_at_infinity(group, point)) {
return 1;
}
field_mul = group->meth->field_mul;
field_sqr = group->meth->field_sqr;
p = &group->field;
if (ctx == NULL) {
ctx = new_ctx = BN_CTX_new();
if (ctx == NULL) {
return 0;
}
}
BN_CTX_start(ctx);
rh = BN_CTX_get(ctx);
tmp = BN_CTX_get(ctx);
Z4 = BN_CTX_get(ctx);
Z6 = BN_CTX_get(ctx);
if (Z6 == NULL) {
goto err;
}
// We have a curve defined by a Weierstrass equation
// y^2 = x^3 + a*x + b.
// The point to consider is given in Jacobian projective coordinates
// where (X, Y, Z) represents (x, y) = (X/Z^2, Y/Z^3).
// Substituting this and multiplying by Z^6 transforms the above equation
// into
// Y^2 = X^3 + a*X*Z^4 + b*Z^6.
// To test this, we add up the right-hand side in 'rh'.
// rh := X^2
if (!field_sqr(group, rh, &point->X, ctx)) {
goto err;
}
if (BN_cmp(&point->Z, &group->one) != 0) {
if (!field_sqr(group, tmp, &point->Z, ctx) ||
!field_sqr(group, Z4, tmp, ctx) ||
!field_mul(group, Z6, Z4, tmp, ctx)) {
goto err;
}
// rh := (rh + a*Z^4)*X
if (group->a_is_minus3) {
if (!bn_mod_lshift1_quick_ctx(tmp, Z4, p, ctx) ||
!bn_mod_add_quick_ctx(tmp, tmp, Z4, p, ctx) ||
!bn_mod_sub_quick_ctx(rh, rh, tmp, p, ctx) ||
!field_mul(group, rh, rh, &point->X, ctx)) {
goto err;
}
} else {
if (!field_mul(group, tmp, Z4, &group->a, ctx) ||
!bn_mod_add_quick_ctx(rh, rh, tmp, p, ctx) ||
!field_mul(group, rh, rh, &point->X, ctx)) {
goto err;
}
}
// rh := rh + b*Z^6
if (!field_mul(group, tmp, &group->b, Z6, ctx) ||
!bn_mod_add_quick_ctx(rh, rh, tmp, p, ctx)) {
goto err;
}
} else {
// rh := (rh + a)*X
if (!bn_mod_add_quick_ctx(rh, rh, &group->a, p, ctx) ||
!field_mul(group, rh, rh, &point->X, ctx)) {
goto err;
}
// rh := rh + b
if (!bn_mod_add_quick_ctx(rh, rh, &group->b, p, ctx)) {
goto err;
}
}
// 'lh' := Y^2
if (!field_sqr(group, tmp, &point->Y, ctx)) {
goto err;
}
ret = (0 == BN_ucmp(tmp, rh));
err:
BN_CTX_end(ctx);
BN_CTX_free(new_ctx);
return ret;
}
int ec_GFp_simple_cmp(const EC_GROUP *group, const EC_POINT *a,
const EC_POINT *b, BN_CTX *ctx) {
// return values:
// -1 error
// 0 equal (in affine coordinates)
// 1 not equal
int (*field_mul)(const EC_GROUP *, BIGNUM *, const BIGNUM *, const BIGNUM *,
BN_CTX *);
int (*field_sqr)(const EC_GROUP *, BIGNUM *, const BIGNUM *, BN_CTX *);
BN_CTX *new_ctx = NULL;
BIGNUM *tmp1, *tmp2, *Za23, *Zb23;
const BIGNUM *tmp1_, *tmp2_;
int ret = -1;
if (ec_GFp_simple_is_at_infinity(group, a)) {
return ec_GFp_simple_is_at_infinity(group, b) ? 0 : 1;
}
if (ec_GFp_simple_is_at_infinity(group, b)) {
return 1;
}
int a_Z_is_one = BN_cmp(&a->Z, &group->one) == 0;
int b_Z_is_one = BN_cmp(&b->Z, &group->one) == 0;
if (a_Z_is_one && b_Z_is_one) {
return ((BN_cmp(&a->X, &b->X) == 0) && BN_cmp(&a->Y, &b->Y) == 0) ? 0 : 1;
}
field_mul = group->meth->field_mul;
field_sqr = group->meth->field_sqr;
if (ctx == NULL) {
ctx = new_ctx = BN_CTX_new();
if (ctx == NULL) {
return -1;
}
}
BN_CTX_start(ctx);
tmp1 = BN_CTX_get(ctx);
tmp2 = BN_CTX_get(ctx);
Za23 = BN_CTX_get(ctx);
Zb23 = BN_CTX_get(ctx);
if (Zb23 == NULL) {
goto end;
}
// We have to decide whether
// (X_a/Z_a^2, Y_a/Z_a^3) = (X_b/Z_b^2, Y_b/Z_b^3),
// or equivalently, whether
// (X_a*Z_b^2, Y_a*Z_b^3) = (X_b*Z_a^2, Y_b*Z_a^3).
if (!b_Z_is_one) {
if (!field_sqr(group, Zb23, &b->Z, ctx) ||
!field_mul(group, tmp1, &a->X, Zb23, ctx)) {
goto end;
}
tmp1_ = tmp1;
} else {
tmp1_ = &a->X;
}
if (!a_Z_is_one) {
if (!field_sqr(group, Za23, &a->Z, ctx) ||
!field_mul(group, tmp2, &b->X, Za23, ctx)) {
goto end;
}
tmp2_ = tmp2;
} else {
tmp2_ = &b->X;
}
// compare X_a*Z_b^2 with X_b*Z_a^2
if (BN_cmp(tmp1_, tmp2_) != 0) {
ret = 1; // points differ
goto end;
}
if (!b_Z_is_one) {
if (!field_mul(group, Zb23, Zb23, &b->Z, ctx) ||
!field_mul(group, tmp1, &a->Y, Zb23, ctx)) {
goto end;
}
// tmp1_ = tmp1
} else {
tmp1_ = &a->Y;
}
if (!a_Z_is_one) {
if (!field_mul(group, Za23, Za23, &a->Z, ctx) ||
!field_mul(group, tmp2, &b->Y, Za23, ctx)) {
goto end;
}
// tmp2_ = tmp2
} else {
tmp2_ = &b->Y;
}
// compare Y_a*Z_b^3 with Y_b*Z_a^3
if (BN_cmp(tmp1_, tmp2_) != 0) {
ret = 1; // points differ
goto end;
}
// points are equal
ret = 0;
end:
BN_CTX_end(ctx);
BN_CTX_free(new_ctx);
return ret;
}
int ec_GFp_simple_make_affine(const EC_GROUP *group, EC_POINT *point,
BN_CTX *ctx) {
BN_CTX *new_ctx = NULL;
BIGNUM *x, *y;
int ret = 0;
if (BN_cmp(&point->Z, &group->one) == 0 ||
EC_POINT_is_at_infinity(group, point)) {
return 1;
}
if (ctx == NULL) {
ctx = new_ctx = BN_CTX_new();
if (ctx == NULL) {
return 0;
}
}
BN_CTX_start(ctx);
x = BN_CTX_get(ctx);
y = BN_CTX_get(ctx);
if (y == NULL) {
goto err;
}
if (!EC_POINT_get_affine_coordinates_GFp(group, point, x, y, ctx) ||
!EC_POINT_set_affine_coordinates_GFp(group, point, x, y, ctx)) {
goto err;
}
if (BN_cmp(&point->Z, &group->one) != 0) {
OPENSSL_PUT_ERROR(EC, ERR_R_INTERNAL_ERROR);
goto err;
}
ret = 1;
err:
BN_CTX_end(ctx);
BN_CTX_free(new_ctx);
return ret;
}
int ec_GFp_simple_points_make_affine(const EC_GROUP *group, size_t num,
EC_POINT *points[], BN_CTX *ctx) {
BN_CTX *new_ctx = NULL;
BIGNUM *tmp, *tmp_Z;
BIGNUM **prod_Z = NULL;
int ret = 0;
if (num == 0) {
return 1;
}
if (ctx == NULL) {
ctx = new_ctx = BN_CTX_new();
if (ctx == NULL) {
return 0;
}
}
BN_CTX_start(ctx);
tmp = BN_CTX_get(ctx);
tmp_Z = BN_CTX_get(ctx);
if (tmp == NULL || tmp_Z == NULL) {
goto err;
}
prod_Z = OPENSSL_malloc(num * sizeof(prod_Z[0]));
if (prod_Z == NULL) {
goto err;
}
OPENSSL_memset(prod_Z, 0, num * sizeof(prod_Z[0]));
for (size_t i = 0; i < num; i++) {
prod_Z[i] = BN_new();
if (prod_Z[i] == NULL) {
goto err;
}
}
// Set each prod_Z[i] to the product of points[0]->Z .. points[i]->Z,
// skipping any zero-valued inputs (pretend that they're 1).
if (!BN_is_zero(&points[0]->Z)) {
if (!BN_copy(prod_Z[0], &points[0]->Z)) {
goto err;
}
} else {
if (BN_copy(prod_Z[0], &group->one) == NULL) {
goto err;
}
}
for (size_t i = 1; i < num; i++) {
if (!BN_is_zero(&points[i]->Z)) {
if (!group->meth->field_mul(group, prod_Z[i], prod_Z[i - 1],
&points[i]->Z, ctx)) {
goto err;
}
} else {
if (!BN_copy(prod_Z[i], prod_Z[i - 1])) {
goto err;
}
}
}
// Now use a single explicit inversion to replace every non-zero points[i]->Z
// by its inverse. We use |BN_mod_inverse_odd| instead of doing a constant-
// time inversion using Fermat's Little Theorem because this function is
// usually only used for converting multiples of a public key point to
// affine, and a public key point isn't secret. If we were to use Fermat's
// Little Theorem then the cost of the inversion would usually be so high
// that converting the multiples to affine would be counterproductive.
int no_inverse;
if (!BN_mod_inverse_odd(tmp, &no_inverse, prod_Z[num - 1], &group->field,
ctx)) {
OPENSSL_PUT_ERROR(EC, ERR_R_BN_LIB);
goto err;
}
if (group->meth->field_encode != NULL) {
// In the Montgomery case, we just turned R*H (representing H)
// into 1/(R*H), but we need R*(1/H) (representing 1/H);
// i.e. we need to multiply by the Montgomery factor twice.
if (!group->meth->field_encode(group, tmp, tmp, ctx) ||
!group->meth->field_encode(group, tmp, tmp, ctx)) {
goto err;
}
}
for (size_t i = num - 1; i > 0; --i) {
// Loop invariant: tmp is the product of the inverses of
// points[0]->Z .. points[i]->Z (zero-valued inputs skipped).
if (BN_is_zero(&points[i]->Z)) {
continue;
}
// Set tmp_Z to the inverse of points[i]->Z (as product
// of Z inverses 0 .. i, Z values 0 .. i - 1).
if (!group->meth->field_mul(group, tmp_Z, prod_Z[i - 1], tmp, ctx) ||
// Update tmp to satisfy the loop invariant for i - 1.
!group->meth->field_mul(group, tmp, tmp, &points[i]->Z, ctx) ||
// Replace points[i]->Z by its inverse.
!BN_copy(&points[i]->Z, tmp_Z)) {
goto err;
}
}
// Replace points[0]->Z by its inverse.
if (!BN_is_zero(&points[0]->Z) && !BN_copy(&points[0]->Z, tmp)) {
goto err;
}
// Finally, fix up the X and Y coordinates for all points.
for (size_t i = 0; i < num; i++) {
EC_POINT *p = points[i];
if (!BN_is_zero(&p->Z)) {
// turn (X, Y, 1/Z) into (X/Z^2, Y/Z^3, 1).
if (!group->meth->field_sqr(group, tmp, &p->Z, ctx) ||
!group->meth->field_mul(group, &p->X, &p->X, tmp, ctx) ||
!group->meth->field_mul(group, tmp, tmp, &p->Z, ctx) ||
!group->meth->field_mul(group, &p->Y, &p->Y, tmp, ctx)) {
goto err;
}
if (BN_copy(&p->Z, &group->one) == NULL) {
goto err;
}
}
}
ret = 1;
err:
BN_CTX_end(ctx);
BN_CTX_free(new_ctx);
if (prod_Z != NULL) {
for (size_t i = 0; i < num; i++) {
if (prod_Z[i] == NULL) {
break;
}
BN_clear_free(prod_Z[i]);
}
OPENSSL_free(prod_Z);
}
return ret;
}
int ec_GFp_simple_field_mul(const EC_GROUP *group, BIGNUM *r, const BIGNUM *a,
const BIGNUM *b, BN_CTX *ctx) {
return BN_mod_mul(r, a, b, &group->field, ctx);
}
int ec_GFp_simple_field_sqr(const EC_GROUP *group, BIGNUM *r, const BIGNUM *a,
BN_CTX *ctx) {
return BN_mod_sqr(r, a, &group->field, ctx);
}
Reference in New Issue View Git Blame Copy Permalink