| /* |
| * Copyright 1995-2022 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 |
| */ |
| |
| #include <stdio.h> |
| #include "internal/cryptlib.h" |
| #include "bn_local.h" |
| |
| #define TABLE_SIZE 32 |
| |
| int BN_mod_exp2_mont(BIGNUM *rr, const BIGNUM *a1, const BIGNUM *p1, |
| const BIGNUM *a2, const BIGNUM *p2, const BIGNUM *m, |
| BN_CTX *ctx, BN_MONT_CTX *in_mont) |
| { |
| int i, j, bits, b, bits1, bits2, ret = |
| 0, wpos1, wpos2, window1, window2, wvalue1, wvalue2; |
| int r_is_one = 1; |
| BIGNUM *d, *r; |
| const BIGNUM *a_mod_m; |
| /* Tables of variables obtained from 'ctx' */ |
| BIGNUM *val1[TABLE_SIZE], *val2[TABLE_SIZE]; |
| BN_MONT_CTX *mont = NULL; |
| |
| bn_check_top(a1); |
| bn_check_top(p1); |
| bn_check_top(a2); |
| bn_check_top(p2); |
| bn_check_top(m); |
| |
| if (!BN_is_odd(m)) { |
| ERR_raise(ERR_LIB_BN, BN_R_CALLED_WITH_EVEN_MODULUS); |
| return 0; |
| } |
| bits1 = BN_num_bits(p1); |
| bits2 = BN_num_bits(p2); |
| if ((bits1 == 0) && (bits2 == 0)) { |
| ret = BN_one(rr); |
| return ret; |
| } |
| |
| bits = (bits1 > bits2) ? bits1 : bits2; |
| |
| BN_CTX_start(ctx); |
| d = BN_CTX_get(ctx); |
| r = BN_CTX_get(ctx); |
| val1[0] = BN_CTX_get(ctx); |
| val2[0] = BN_CTX_get(ctx); |
| if (val2[0] == NULL) |
| goto err; |
| |
| if (in_mont != NULL) |
| mont = in_mont; |
| else { |
| if ((mont = BN_MONT_CTX_new()) == NULL) |
| goto err; |
| if (!BN_MONT_CTX_set(mont, m, ctx)) |
| goto err; |
| } |
| |
| window1 = BN_window_bits_for_exponent_size(bits1); |
| window2 = BN_window_bits_for_exponent_size(bits2); |
| |
| /* |
| * Build table for a1: val1[i] := a1^(2*i + 1) mod m for i = 0 .. 2^(window1-1) |
| */ |
| if (a1->neg || BN_ucmp(a1, m) >= 0) { |
| if (!BN_mod(val1[0], a1, m, ctx)) |
| goto err; |
| a_mod_m = val1[0]; |
| } else |
| a_mod_m = a1; |
| if (BN_is_zero(a_mod_m)) { |
| BN_zero(rr); |
| ret = 1; |
| goto err; |
| } |
| |
| if (!BN_to_montgomery(val1[0], a_mod_m, mont, ctx)) |
| goto err; |
| if (window1 > 1) { |
| if (!BN_mod_mul_montgomery(d, val1[0], val1[0], mont, ctx)) |
| goto err; |
| |
| j = 1 << (window1 - 1); |
| for (i = 1; i < j; i++) { |
| if (((val1[i] = BN_CTX_get(ctx)) == NULL) || |
| !BN_mod_mul_montgomery(val1[i], val1[i - 1], d, mont, ctx)) |
| goto err; |
| } |
| } |
| |
| /* |
| * Build table for a2: val2[i] := a2^(2*i + 1) mod m for i = 0 .. 2^(window2-1) |
| */ |
| if (a2->neg || BN_ucmp(a2, m) >= 0) { |
| if (!BN_mod(val2[0], a2, m, ctx)) |
| goto err; |
| a_mod_m = val2[0]; |
| } else |
| a_mod_m = a2; |
| if (BN_is_zero(a_mod_m)) { |
| BN_zero(rr); |
| ret = 1; |
| goto err; |
| } |
| if (!BN_to_montgomery(val2[0], a_mod_m, mont, ctx)) |
| goto err; |
| if (window2 > 1) { |
| if (!BN_mod_mul_montgomery(d, val2[0], val2[0], mont, ctx)) |
| goto err; |
| |
| j = 1 << (window2 - 1); |
| for (i = 1; i < j; i++) { |
| if (((val2[i] = BN_CTX_get(ctx)) == NULL) || |
| !BN_mod_mul_montgomery(val2[i], val2[i - 1], d, mont, ctx)) |
| goto err; |
| } |
| } |
| |
| /* Now compute the power product, using independent windows. */ |
| r_is_one = 1; |
| wvalue1 = 0; /* The 'value' of the first window */ |
| wvalue2 = 0; /* The 'value' of the second window */ |
| wpos1 = 0; /* If wvalue1 > 0, the bottom bit of the |
| * first window */ |
| wpos2 = 0; /* If wvalue2 > 0, the bottom bit of the |
| * second window */ |
| |
| if (!BN_to_montgomery(r, BN_value_one(), mont, ctx)) |
| goto err; |
| for (b = bits - 1; b >= 0; b--) { |
| if (!r_is_one) { |
| if (!BN_mod_mul_montgomery(r, r, r, mont, ctx)) |
| goto err; |
| } |
| |
| if (!wvalue1) |
| if (BN_is_bit_set(p1, b)) { |
| /* |
| * consider bits b-window1+1 .. b for this window |
| */ |
| i = b - window1 + 1; |
| while (!BN_is_bit_set(p1, i)) /* works for i<0 */ |
| i++; |
| wpos1 = i; |
| wvalue1 = 1; |
| for (i = b - 1; i >= wpos1; i--) { |
| wvalue1 <<= 1; |
| if (BN_is_bit_set(p1, i)) |
| wvalue1++; |
| } |
| } |
| |
| if (!wvalue2) |
| if (BN_is_bit_set(p2, b)) { |
| /* |
| * consider bits b-window2+1 .. b for this window |
| */ |
| i = b - window2 + 1; |
| while (!BN_is_bit_set(p2, i)) |
| i++; |
| wpos2 = i; |
| wvalue2 = 1; |
| for (i = b - 1; i >= wpos2; i--) { |
| wvalue2 <<= 1; |
| if (BN_is_bit_set(p2, i)) |
| wvalue2++; |
| } |
| } |
| |
| if (wvalue1 && b == wpos1) { |
| /* wvalue1 is odd and < 2^window1 */ |
| if (!BN_mod_mul_montgomery(r, r, val1[wvalue1 >> 1], mont, ctx)) |
| goto err; |
| wvalue1 = 0; |
| r_is_one = 0; |
| } |
| |
| if (wvalue2 && b == wpos2) { |
| /* wvalue2 is odd and < 2^window2 */ |
| if (!BN_mod_mul_montgomery(r, r, val2[wvalue2 >> 1], mont, ctx)) |
| goto err; |
| wvalue2 = 0; |
| r_is_one = 0; |
| } |
| } |
| if (!BN_from_montgomery(rr, r, mont, ctx)) |
| goto err; |
| ret = 1; |
| err: |
| if (in_mont == NULL) |
| BN_MONT_CTX_free(mont); |
| BN_CTX_end(ctx); |
| bn_check_top(rr); |
| return ret; |
| } |