| /* |
| * Copyright 2011-2022 The OpenSSL Project Authors. All Rights Reserved. |
| * Copyright (c) 2002, Oracle and/or its affiliates. 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 |
| */ |
| |
| /* |
| * ECDSA low level APIs are deprecated for public use, but still ok for |
| * internal use. |
| */ |
| #include "internal/deprecated.h" |
| |
| #include <openssl/err.h> |
| |
| #include "ec_local.h" |
| |
| #ifndef OPENSSL_NO_EC2M |
| |
| /*- |
| * Calculates and sets the affine coordinates of an EC_POINT from the given |
| * compressed coordinates. Uses algorithm 2.3.4 of SEC 1. |
| * Note that the simple implementation only uses affine coordinates. |
| * |
| * The method is from the following publication: |
| * |
| * Harper, Menezes, Vanstone: |
| * "Public-Key Cryptosystems with Very Small Key Lengths", |
| * EUROCRYPT '92, Springer-Verlag LNCS 658, |
| * published February 1993 |
| * |
| * US Patents 6,141,420 and 6,618,483 (Vanstone, Mullin, Agnew) describe |
| * the same method, but claim no priority date earlier than July 29, 1994 |
| * (and additionally fail to cite the EUROCRYPT '92 publication as prior art). |
| */ |
| int ossl_ec_GF2m_simple_set_compressed_coordinates(const EC_GROUP *group, |
| EC_POINT *point, |
| const BIGNUM *x_, int y_bit, |
| BN_CTX *ctx) |
| { |
| BIGNUM *tmp, *x, *y, *z; |
| int ret = 0, z0; |
| #ifndef FIPS_MODULE |
| BN_CTX *new_ctx = NULL; |
| |
| if (ctx == NULL) { |
| ctx = new_ctx = BN_CTX_new(); |
| if (ctx == NULL) |
| return 0; |
| } |
| #endif |
| |
| y_bit = (y_bit != 0) ? 1 : 0; |
| |
| BN_CTX_start(ctx); |
| tmp = BN_CTX_get(ctx); |
| x = BN_CTX_get(ctx); |
| y = BN_CTX_get(ctx); |
| z = BN_CTX_get(ctx); |
| if (z == NULL) |
| goto err; |
| |
| if (!BN_GF2m_mod_arr(x, x_, group->poly)) |
| goto err; |
| if (BN_is_zero(x)) { |
| if (!BN_GF2m_mod_sqrt_arr(y, group->b, group->poly, ctx)) |
| goto err; |
| } else { |
| if (!group->meth->field_sqr(group, tmp, x, ctx)) |
| goto err; |
| if (!group->meth->field_div(group, tmp, group->b, tmp, ctx)) |
| goto err; |
| if (!BN_GF2m_add(tmp, group->a, tmp)) |
| goto err; |
| if (!BN_GF2m_add(tmp, x, tmp)) |
| goto err; |
| ERR_set_mark(); |
| if (!BN_GF2m_mod_solve_quad_arr(z, tmp, group->poly, ctx)) { |
| #ifndef FIPS_MODULE |
| unsigned long err = ERR_peek_last_error(); |
| |
| if (ERR_GET_LIB(err) == ERR_LIB_BN |
| && ERR_GET_REASON(err) == BN_R_NO_SOLUTION) { |
| ERR_pop_to_mark(); |
| ERR_raise(ERR_LIB_EC, EC_R_INVALID_COMPRESSED_POINT); |
| } else |
| #endif |
| { |
| ERR_clear_last_mark(); |
| ERR_raise(ERR_LIB_EC, ERR_R_BN_LIB); |
| } |
| goto err; |
| } |
| ERR_clear_last_mark(); |
| z0 = (BN_is_odd(z)) ? 1 : 0; |
| if (!group->meth->field_mul(group, y, x, z, ctx)) |
| goto err; |
| if (z0 != y_bit) { |
| if (!BN_GF2m_add(y, y, x)) |
| goto err; |
| } |
| } |
| |
| if (!EC_POINT_set_affine_coordinates(group, point, x, y, ctx)) |
| goto err; |
| |
| ret = 1; |
| |
| err: |
| BN_CTX_end(ctx); |
| #ifndef FIPS_MODULE |
| BN_CTX_free(new_ctx); |
| #endif |
| return ret; |
| } |
| |
| /* |
| * Converts an EC_POINT to an octet string. If buf is NULL, the encoded |
| * length will be returned. If the length len of buf is smaller than required |
| * an error will be returned. |
| */ |
| size_t ossl_ec_GF2m_simple_point2oct(const EC_GROUP *group, |
| const EC_POINT *point, |
| point_conversion_form_t form, |
| unsigned char *buf, size_t len, BN_CTX *ctx) |
| { |
| size_t ret; |
| int used_ctx = 0; |
| BIGNUM *x, *y, *yxi; |
| size_t field_len, i, skip; |
| #ifndef FIPS_MODULE |
| BN_CTX *new_ctx = NULL; |
| #endif |
| |
| if ((form != POINT_CONVERSION_COMPRESSED) |
| && (form != POINT_CONVERSION_UNCOMPRESSED) |
| && (form != POINT_CONVERSION_HYBRID)) { |
| ERR_raise(ERR_LIB_EC, EC_R_INVALID_FORM); |
| goto err; |
| } |
| |
| if (EC_POINT_is_at_infinity(group, point)) { |
| /* encodes to a single 0 octet */ |
| if (buf != NULL) { |
| if (len < 1) { |
| ERR_raise(ERR_LIB_EC, EC_R_BUFFER_TOO_SMALL); |
| return 0; |
| } |
| buf[0] = 0; |
| } |
| return 1; |
| } |
| |
| /* ret := required output buffer length */ |
| field_len = (EC_GROUP_get_degree(group) + 7) / 8; |
| ret = |
| (form == |
| POINT_CONVERSION_COMPRESSED) ? 1 + field_len : 1 + 2 * field_len; |
| |
| /* if 'buf' is NULL, just return required length */ |
| if (buf != NULL) { |
| if (len < ret) { |
| ERR_raise(ERR_LIB_EC, EC_R_BUFFER_TOO_SMALL); |
| goto err; |
| } |
| |
| #ifndef FIPS_MODULE |
| if (ctx == NULL) { |
| ctx = new_ctx = BN_CTX_new(); |
| if (ctx == NULL) |
| return 0; |
| } |
| #endif |
| |
| BN_CTX_start(ctx); |
| used_ctx = 1; |
| x = BN_CTX_get(ctx); |
| y = BN_CTX_get(ctx); |
| yxi = BN_CTX_get(ctx); |
| if (yxi == NULL) |
| goto err; |
| |
| if (!EC_POINT_get_affine_coordinates(group, point, x, y, ctx)) |
| goto err; |
| |
| buf[0] = form; |
| if ((form != POINT_CONVERSION_UNCOMPRESSED) && !BN_is_zero(x)) { |
| if (!group->meth->field_div(group, yxi, y, x, ctx)) |
| goto err; |
| if (BN_is_odd(yxi)) |
| buf[0]++; |
| } |
| |
| i = 1; |
| |
| skip = field_len - BN_num_bytes(x); |
| if (skip > field_len) { |
| ERR_raise(ERR_LIB_EC, ERR_R_INTERNAL_ERROR); |
| goto err; |
| } |
| while (skip > 0) { |
| buf[i++] = 0; |
| skip--; |
| } |
| skip = BN_bn2bin(x, buf + i); |
| i += skip; |
| if (i != 1 + field_len) { |
| ERR_raise(ERR_LIB_EC, ERR_R_INTERNAL_ERROR); |
| goto err; |
| } |
| |
| if (form == POINT_CONVERSION_UNCOMPRESSED |
| || form == POINT_CONVERSION_HYBRID) { |
| skip = field_len - BN_num_bytes(y); |
| if (skip > field_len) { |
| ERR_raise(ERR_LIB_EC, ERR_R_INTERNAL_ERROR); |
| goto err; |
| } |
| while (skip > 0) { |
| buf[i++] = 0; |
| skip--; |
| } |
| skip = BN_bn2bin(y, buf + i); |
| i += skip; |
| } |
| |
| if (i != ret) { |
| ERR_raise(ERR_LIB_EC, ERR_R_INTERNAL_ERROR); |
| goto err; |
| } |
| } |
| |
| if (used_ctx) |
| BN_CTX_end(ctx); |
| #ifndef FIPS_MODULE |
| BN_CTX_free(new_ctx); |
| #endif |
| return ret; |
| |
| err: |
| if (used_ctx) |
| BN_CTX_end(ctx); |
| #ifndef FIPS_MODULE |
| BN_CTX_free(new_ctx); |
| #endif |
| return 0; |
| } |
| |
| /* |
| * Converts an octet string representation to an EC_POINT. Note that the |
| * simple implementation only uses affine coordinates. |
| */ |
| int ossl_ec_GF2m_simple_oct2point(const EC_GROUP *group, EC_POINT *point, |
| const unsigned char *buf, size_t len, |
| BN_CTX *ctx) |
| { |
| point_conversion_form_t form; |
| int y_bit, m; |
| BIGNUM *x, *y, *yxi; |
| size_t field_len, enc_len; |
| int ret = 0; |
| #ifndef FIPS_MODULE |
| BN_CTX *new_ctx = NULL; |
| #endif |
| |
| if (len == 0) { |
| ERR_raise(ERR_LIB_EC, EC_R_BUFFER_TOO_SMALL); |
| return 0; |
| } |
| |
| /* |
| * The first octet is the point conversion octet PC, see X9.62, page 4 |
| * and section 4.4.2. It must be: |
| * 0x00 for the point at infinity |
| * 0x02 or 0x03 for compressed form |
| * 0x04 for uncompressed form |
| * 0x06 or 0x07 for hybrid form. |
| * For compressed or hybrid forms, we store the last bit of buf[0] as |
| * y_bit and clear it from buf[0] so as to obtain a POINT_CONVERSION_*. |
| * We error if buf[0] contains any but the above values. |
| */ |
| y_bit = buf[0] & 1; |
| form = buf[0] & ~1U; |
| |
| if ((form != 0) && (form != POINT_CONVERSION_COMPRESSED) |
| && (form != POINT_CONVERSION_UNCOMPRESSED) |
| && (form != POINT_CONVERSION_HYBRID)) { |
| ERR_raise(ERR_LIB_EC, EC_R_INVALID_ENCODING); |
| return 0; |
| } |
| if ((form == 0 || form == POINT_CONVERSION_UNCOMPRESSED) && y_bit) { |
| ERR_raise(ERR_LIB_EC, EC_R_INVALID_ENCODING); |
| return 0; |
| } |
| |
| /* The point at infinity is represented by a single zero octet. */ |
| if (form == 0) { |
| if (len != 1) { |
| ERR_raise(ERR_LIB_EC, EC_R_INVALID_ENCODING); |
| return 0; |
| } |
| |
| return EC_POINT_set_to_infinity(group, point); |
| } |
| |
| m = EC_GROUP_get_degree(group); |
| field_len = (m + 7) / 8; |
| enc_len = |
| (form == |
| POINT_CONVERSION_COMPRESSED) ? 1 + field_len : 1 + 2 * field_len; |
| |
| if (len != enc_len) { |
| ERR_raise(ERR_LIB_EC, EC_R_INVALID_ENCODING); |
| return 0; |
| } |
| |
| #ifndef FIPS_MODULE |
| if (ctx == NULL) { |
| ctx = new_ctx = BN_CTX_new(); |
| if (ctx == NULL) |
| return 0; |
| } |
| #endif |
| |
| BN_CTX_start(ctx); |
| x = BN_CTX_get(ctx); |
| y = BN_CTX_get(ctx); |
| yxi = BN_CTX_get(ctx); |
| if (yxi == NULL) |
| goto err; |
| |
| if (!BN_bin2bn(buf + 1, field_len, x)) |
| goto err; |
| if (BN_num_bits(x) > m) { |
| ERR_raise(ERR_LIB_EC, EC_R_INVALID_ENCODING); |
| goto err; |
| } |
| |
| if (form == POINT_CONVERSION_COMPRESSED) { |
| if (!EC_POINT_set_compressed_coordinates(group, point, x, y_bit, ctx)) |
| goto err; |
| } else { |
| if (!BN_bin2bn(buf + 1 + field_len, field_len, y)) |
| goto err; |
| if (BN_num_bits(y) > m) { |
| ERR_raise(ERR_LIB_EC, EC_R_INVALID_ENCODING); |
| goto err; |
| } |
| if (form == POINT_CONVERSION_HYBRID) { |
| /* |
| * Check that the form in the encoding was set correctly |
| * according to X9.62 4.4.2.a, 4(c), see also first paragraph |
| * of X9.62, 4.4.1.b. |
| */ |
| if (BN_is_zero(x)) { |
| if (y_bit != 0) { |
| ERR_raise(ERR_LIB_EC, EC_R_INVALID_ENCODING); |
| goto err; |
| } |
| } else { |
| if (!group->meth->field_div(group, yxi, y, x, ctx)) |
| goto err; |
| if (y_bit != BN_is_odd(yxi)) { |
| ERR_raise(ERR_LIB_EC, EC_R_INVALID_ENCODING); |
| goto err; |
| } |
| } |
| } |
| |
| /* |
| * EC_POINT_set_affine_coordinates is responsible for checking that |
| * the point is on the curve. |
| */ |
| if (!EC_POINT_set_affine_coordinates(group, point, x, y, ctx)) |
| goto err; |
| } |
| |
| ret = 1; |
| |
| err: |
| BN_CTX_end(ctx); |
| #ifndef FIPS_MODULE |
| BN_CTX_free(new_ctx); |
| #endif |
| return ret; |
| } |
| #endif |
