diff options
Diffstat (limited to 'thirdparty/mbedtls/library/bignum.c')
| -rw-r--r-- | thirdparty/mbedtls/library/bignum.c | 192 |
1 files changed, 143 insertions, 49 deletions
diff --git a/thirdparty/mbedtls/library/bignum.c b/thirdparty/mbedtls/library/bignum.c index 87ccf42fad..2feb727d89 100644 --- a/thirdparty/mbedtls/library/bignum.c +++ b/thirdparty/mbedtls/library/bignum.c @@ -1,8 +1,14 @@ /* * Multi-precision integer library * - * Copyright (C) 2006-2015, ARM Limited, All Rights Reserved - * SPDX-License-Identifier: Apache-2.0 + * Copyright The Mbed TLS Contributors + * SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later + * + * This file is provided under the Apache License 2.0, or the + * GNU General Public License v2.0 or later. + * + * ********** + * Apache License 2.0: * * Licensed under the Apache License, Version 2.0 (the "License"); you may * not use this file except in compliance with the License. @@ -16,7 +22,26 @@ * See the License for the specific language governing permissions and * limitations under the License. * - * This file is part of mbed TLS (https://tls.mbed.org) + * ********** + * + * ********** + * GNU General Public License v2.0 or later: + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 2 of the License, or + * (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License along + * with this program; if not, write to the Free Software Foundation, Inc., + * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA. + * + * ********** */ /* @@ -243,6 +268,22 @@ void mbedtls_mpi_swap( mbedtls_mpi *X, mbedtls_mpi *Y ) } /* + * Conditionally assign dest = src, without leaking information + * about whether the assignment was made or not. + * dest and src must be arrays of limbs of size n. + * assign must be 0 or 1. + */ +static void mpi_safe_cond_assign( size_t n, + mbedtls_mpi_uint *dest, + const mbedtls_mpi_uint *src, + unsigned char assign ) +{ + size_t i; + for( i = 0; i < n; i++ ) + dest[i] = dest[i] * ( 1 - assign ) + src[i] * assign; +} + +/* * Conditionally assign X = Y, without leaking information * about whether the assignment was made or not. * (Leaking information about the respective sizes of X and Y is ok however.) @@ -261,10 +302,9 @@ int mbedtls_mpi_safe_cond_assign( mbedtls_mpi *X, const mbedtls_mpi *Y, unsigned X->s = X->s * ( 1 - assign ) + Y->s * assign; - for( i = 0; i < Y->n; i++ ) - X->p[i] = X->p[i] * ( 1 - assign ) + Y->p[i] * assign; + mpi_safe_cond_assign( Y->n, X->p, Y->p, assign ); - for( ; i < X->n; i++ ) + for( i = Y->n; i < X->n; i++ ) X->p[i] *= ( 1 - assign ); cleanup: @@ -1249,10 +1289,24 @@ cleanup: return( ret ); } -/* - * Helper for mbedtls_mpi subtraction +/** + * Helper for mbedtls_mpi subtraction. + * + * Calculate d - s where d and s have the same size. + * This function operates modulo (2^ciL)^n and returns the carry + * (1 if there was a wraparound, i.e. if `d < s`, and 0 otherwise). + * + * \param n Number of limbs of \p d and \p s. + * \param[in,out] d On input, the left operand. + * On output, the result of the subtraction: + * \param[in] s The right operand. + * + * \return 1 if `d < s`. + * 0 if `d >= s`. */ -static void mpi_sub_hlp( size_t n, mbedtls_mpi_uint *s, mbedtls_mpi_uint *d ) +static mbedtls_mpi_uint mpi_sub_hlp( size_t n, + mbedtls_mpi_uint *d, + const mbedtls_mpi_uint *s ) { size_t i; mbedtls_mpi_uint c, z; @@ -1263,28 +1317,22 @@ static void mpi_sub_hlp( size_t n, mbedtls_mpi_uint *s, mbedtls_mpi_uint *d ) c = ( *d < *s ) + z; *d -= *s; } - while( c != 0 ) - { - z = ( *d < c ); *d -= c; - c = z; d++; - } + return( c ); } /* - * Unsigned subtraction: X = |A| - |B| (HAC 14.9) + * Unsigned subtraction: X = |A| - |B| (HAC 14.9, 14.10) */ int mbedtls_mpi_sub_abs( mbedtls_mpi *X, const mbedtls_mpi *A, const mbedtls_mpi *B ) { mbedtls_mpi TB; int ret; size_t n; + mbedtls_mpi_uint carry; MPI_VALIDATE_RET( X != NULL ); MPI_VALIDATE_RET( A != NULL ); MPI_VALIDATE_RET( B != NULL ); - if( mbedtls_mpi_cmp_abs( A, B ) < 0 ) - return( MBEDTLS_ERR_MPI_NEGATIVE_VALUE ); - mbedtls_mpi_init( &TB ); if( X == B ) @@ -1307,7 +1355,21 @@ int mbedtls_mpi_sub_abs( mbedtls_mpi *X, const mbedtls_mpi *A, const mbedtls_mpi if( B->p[n - 1] != 0 ) break; - mpi_sub_hlp( n, B->p, X->p ); + carry = mpi_sub_hlp( n, X->p, B->p ); + if( carry != 0 ) + { + /* Propagate the carry to the first nonzero limb of X. */ + for( ; n < X->n && X->p[n] == 0; n++ ) + --X->p[n]; + /* If we ran out of space for the carry, it means that the result + * is negative. */ + if( n == X->n ) + { + ret = MBEDTLS_ERR_MPI_NEGATIVE_VALUE; + goto cleanup; + } + --X->p[n]; + } cleanup: @@ -1887,18 +1949,34 @@ static void mpi_montg_init( mbedtls_mpi_uint *mm, const mbedtls_mpi *N ) *mm = ~x + 1; } -/* - * Montgomery multiplication: A = A * B * R^-1 mod N (HAC 14.36) +/** Montgomery multiplication: A = A * B * R^-1 mod N (HAC 14.36) + * + * \param[in,out] A One of the numbers to multiply. + * It must have at least as many limbs as N + * (A->n >= N->n), and any limbs beyond n are ignored. + * On successful completion, A contains the result of + * the multiplication A * B * R^-1 mod N where + * R = (2^ciL)^n. + * \param[in] B One of the numbers to multiply. + * It must be nonzero and must not have more limbs than N + * (B->n <= N->n). + * \param[in] N The modulo. N must be odd. + * \param mm The value calculated by `mpi_montg_init(&mm, N)`. + * This is -N^-1 mod 2^ciL. + * \param[in,out] T A bignum for temporary storage. + * It must be at least twice the limb size of N plus 2 + * (T->n >= 2 * (N->n + 1)). + * Its initial content is unused and + * its final content is indeterminate. + * Note that unlike the usual convention in the library + * for `const mbedtls_mpi*`, the content of T can change. */ -static int mpi_montmul( mbedtls_mpi *A, const mbedtls_mpi *B, const mbedtls_mpi *N, mbedtls_mpi_uint mm, +static void mpi_montmul( mbedtls_mpi *A, const mbedtls_mpi *B, const mbedtls_mpi *N, mbedtls_mpi_uint mm, const mbedtls_mpi *T ) { size_t i, n, m; mbedtls_mpi_uint u0, u1, *d; - if( T->n < N->n + 1 || T->p == NULL ) - return( MBEDTLS_ERR_MPI_BAD_INPUT_DATA ); - memset( T->p, 0, T->n * ciL ); d = T->p; @@ -1919,22 +1997,34 @@ static int mpi_montmul( mbedtls_mpi *A, const mbedtls_mpi *B, const mbedtls_mpi *d++ = u0; d[n + 1] = 0; } - memcpy( A->p, d, ( n + 1 ) * ciL ); - - if( mbedtls_mpi_cmp_abs( A, N ) >= 0 ) - mpi_sub_hlp( n, N->p, A->p ); - else - /* prevent timing attacks */ - mpi_sub_hlp( n, A->p, T->p ); - - return( 0 ); + /* At this point, d is either the desired result or the desired result + * plus N. We now potentially subtract N, avoiding leaking whether the + * subtraction is performed through side channels. */ + + /* Copy the n least significant limbs of d to A, so that + * A = d if d < N (recall that N has n limbs). */ + memcpy( A->p, d, n * ciL ); + /* If d >= N then we want to set A to d - N. To prevent timing attacks, + * do the calculation without using conditional tests. */ + /* Set d to d0 + (2^biL)^n - N where d0 is the current value of d. */ + d[n] += 1; + d[n] -= mpi_sub_hlp( n, d, N->p ); + /* If d0 < N then d < (2^biL)^n + * so d[n] == 0 and we want to keep A as it is. + * If d0 >= N then d >= (2^biL)^n, and d <= (2^biL)^n + N < 2 * (2^biL)^n + * so d[n] == 1 and we want to set A to the result of the subtraction + * which is d - (2^biL)^n, i.e. the n least significant limbs of d. + * This exactly corresponds to a conditional assignment. */ + mpi_safe_cond_assign( n, A->p, d, (unsigned char) d[n] ); } /* * Montgomery reduction: A = A * R^-1 mod N + * + * See mpi_montmul() regarding constraints and guarantees on the parameters. */ -static int mpi_montred( mbedtls_mpi *A, const mbedtls_mpi *N, - mbedtls_mpi_uint mm, const mbedtls_mpi *T ) +static void mpi_montred( mbedtls_mpi *A, const mbedtls_mpi *N, + mbedtls_mpi_uint mm, const mbedtls_mpi *T ) { mbedtls_mpi_uint z = 1; mbedtls_mpi U; @@ -1942,7 +2032,7 @@ static int mpi_montred( mbedtls_mpi *A, const mbedtls_mpi *N, U.n = U.s = (int) z; U.p = &z; - return( mpi_montmul( A, &U, N, mm, T ) ); + mpi_montmul( A, &U, N, mm, T ); } /* @@ -1957,7 +2047,7 @@ int mbedtls_mpi_exp_mod( mbedtls_mpi *X, const mbedtls_mpi *A, size_t i, j, nblimbs; size_t bufsize, nbits; mbedtls_mpi_uint ei, mm, state; - mbedtls_mpi RR, T, W[ 2 << MBEDTLS_MPI_WINDOW_SIZE ], Apos; + mbedtls_mpi RR, T, W[ 1 << MBEDTLS_MPI_WINDOW_SIZE ], Apos; int neg; MPI_VALIDATE_RET( X != NULL ); @@ -1971,6 +2061,10 @@ int mbedtls_mpi_exp_mod( mbedtls_mpi *X, const mbedtls_mpi *A, if( mbedtls_mpi_cmp_int( E, 0 ) < 0 ) return( MBEDTLS_ERR_MPI_BAD_INPUT_DATA ); + if( mbedtls_mpi_bitlen( E ) > MBEDTLS_MPI_MAX_BITS || + mbedtls_mpi_bitlen( N ) > MBEDTLS_MPI_MAX_BITS ) + return ( MBEDTLS_ERR_MPI_BAD_INPUT_DATA ); + /* * Init temps and window size */ @@ -2028,13 +2122,13 @@ int mbedtls_mpi_exp_mod( mbedtls_mpi *X, const mbedtls_mpi *A, else MBEDTLS_MPI_CHK( mbedtls_mpi_copy( &W[1], A ) ); - MBEDTLS_MPI_CHK( mpi_montmul( &W[1], &RR, N, mm, &T ) ); + mpi_montmul( &W[1], &RR, N, mm, &T ); /* * X = R^2 * R^-1 mod N = R mod N */ MBEDTLS_MPI_CHK( mbedtls_mpi_copy( X, &RR ) ); - MBEDTLS_MPI_CHK( mpi_montred( X, N, mm, &T ) ); + mpi_montred( X, N, mm, &T ); if( wsize > 1 ) { @@ -2047,7 +2141,7 @@ int mbedtls_mpi_exp_mod( mbedtls_mpi *X, const mbedtls_mpi *A, MBEDTLS_MPI_CHK( mbedtls_mpi_copy( &W[j], &W[1] ) ); for( i = 0; i < wsize - 1; i++ ) - MBEDTLS_MPI_CHK( mpi_montmul( &W[j], &W[j], N, mm, &T ) ); + mpi_montmul( &W[j], &W[j], N, mm, &T ); /* * W[i] = W[i - 1] * W[1] @@ -2057,7 +2151,7 @@ int mbedtls_mpi_exp_mod( mbedtls_mpi *X, const mbedtls_mpi *A, MBEDTLS_MPI_CHK( mbedtls_mpi_grow( &W[i], N->n + 1 ) ); MBEDTLS_MPI_CHK( mbedtls_mpi_copy( &W[i], &W[i - 1] ) ); - MBEDTLS_MPI_CHK( mpi_montmul( &W[i], &W[1], N, mm, &T ) ); + mpi_montmul( &W[i], &W[1], N, mm, &T ); } } @@ -2094,7 +2188,7 @@ int mbedtls_mpi_exp_mod( mbedtls_mpi *X, const mbedtls_mpi *A, /* * out of window, square X */ - MBEDTLS_MPI_CHK( mpi_montmul( X, X, N, mm, &T ) ); + mpi_montmul( X, X, N, mm, &T ); continue; } @@ -2112,12 +2206,12 @@ int mbedtls_mpi_exp_mod( mbedtls_mpi *X, const mbedtls_mpi *A, * X = X^wsize R^-1 mod N */ for( i = 0; i < wsize; i++ ) - MBEDTLS_MPI_CHK( mpi_montmul( X, X, N, mm, &T ) ); + mpi_montmul( X, X, N, mm, &T ); /* * X = X * W[wbits] R^-1 mod N */ - MBEDTLS_MPI_CHK( mpi_montmul( X, &W[wbits], N, mm, &T ) ); + mpi_montmul( X, &W[wbits], N, mm, &T ); state--; nbits = 0; @@ -2130,18 +2224,18 @@ int mbedtls_mpi_exp_mod( mbedtls_mpi *X, const mbedtls_mpi *A, */ for( i = 0; i < nbits; i++ ) { - MBEDTLS_MPI_CHK( mpi_montmul( X, X, N, mm, &T ) ); + mpi_montmul( X, X, N, mm, &T ); wbits <<= 1; if( ( wbits & ( one << wsize ) ) != 0 ) - MBEDTLS_MPI_CHK( mpi_montmul( X, &W[1], N, mm, &T ) ); + mpi_montmul( X, &W[1], N, mm, &T ); } /* * X = A^E * R * R^-1 mod N = A^E mod N */ - MBEDTLS_MPI_CHK( mpi_montred( X, N, mm, &T ) ); + mpi_montred( X, N, mm, &T ); if( neg && E->n != 0 && ( E->p[0] & 1 ) != 0 ) { @@ -2247,7 +2341,7 @@ int mbedtls_mpi_fill_random( mbedtls_mpi *X, size_t size, MBEDTLS_MPI_CHK( mbedtls_mpi_lset( X, 0 ) ); Xp = (unsigned char*) X->p; - f_rng( p_rng, Xp + overhead, size ); + MBEDTLS_MPI_CHK( f_rng( p_rng, Xp + overhead, size ) ); mpi_bigendian_to_host( X->p, limbs ); |