diff options
Diffstat (limited to 'grub-core/lib/libgcrypt/mpi/mpi-pow.c')
| -rw-r--r-- | grub-core/lib/libgcrypt/mpi/mpi-pow.c | 338 |
1 files changed, 338 insertions, 0 deletions
diff --git a/grub-core/lib/libgcrypt/mpi/mpi-pow.c b/grub-core/lib/libgcrypt/mpi/mpi-pow.c new file mode 100644 index 0000000..58643fe --- /dev/null +++ b/grub-core/lib/libgcrypt/mpi/mpi-pow.c @@ -0,0 +1,338 @@ +/* mpi-pow.c - MPI functions for exponentiation + * Copyright (C) 1994, 1996, 1998, 2000, 2002 + * 2003 Free Software Foundation, Inc. + * 2013 g10 Code GmbH + * + * This file is part of Libgcrypt. + * + * Libgcrypt is free software; you can redistribute it and/or modify + * it under the terms of the GNU Lesser General Public License as + * published by the Free Software Foundation; either version 2.1 of + * the License, or (at your option) any later version. + * + * Libgcrypt 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 Lesser General Public License for more details. + * + * You should have received a copy of the GNU Lesser General Public + * License along with this program; if not, see <http://www.gnu.org/licenses/>. + * + * Note: This code is heavily based on the GNU MP Library. + * Actually it's the same code with only minor changes in the + * way the data is stored; this is to support the abstraction + * of an optional secure memory allocation which may be used + * to avoid revealing of sensitive data due to paging etc. + */ + +#include <config.h> +#include <stdio.h> +#include <stdlib.h> +#include <string.h> + +#include "mpi-internal.h" +#include "longlong.h" + + +/**************** + * RES = BASE ^ EXPO mod MOD + */ +void +gcry_mpi_powm (gcry_mpi_t res, + gcry_mpi_t base, gcry_mpi_t expo, gcry_mpi_t mod) +{ + /* Pointer to the limbs of the arguments, their size and signs. */ + mpi_ptr_t rp, ep, mp, bp; + mpi_size_t esize, msize, bsize, rsize; + int msign, bsign, rsign; + /* Flags telling the secure allocation status of the arguments. */ + int esec, msec, bsec; + /* Size of the result including space for temporary values. */ + mpi_size_t size; + /* Helper. */ + int mod_shift_cnt; + int negative_result; + mpi_ptr_t mp_marker = NULL; + mpi_ptr_t bp_marker = NULL; + mpi_ptr_t ep_marker = NULL; + mpi_ptr_t xp_marker = NULL; + unsigned int mp_nlimbs = 0; + unsigned int bp_nlimbs = 0; + unsigned int ep_nlimbs = 0; + unsigned int xp_nlimbs = 0; + mpi_ptr_t tspace = NULL; + mpi_size_t tsize = 0; + + + esize = expo->nlimbs; + msize = mod->nlimbs; + size = 2 * msize; + msign = mod->sign; + + esec = mpi_is_secure(expo); + msec = mpi_is_secure(mod); + bsec = mpi_is_secure(base); + + rp = res->d; + ep = expo->d; + + if (!msize) + grub_fatal ("mpi division by zero"); + + if (!esize) + { + /* Exponent is zero, result is 1 mod MOD, i.e., 1 or 0 depending + on if MOD equals 1. */ + res->nlimbs = (msize == 1 && mod->d[0] == 1) ? 0 : 1; + if (res->nlimbs) + { + RESIZE_IF_NEEDED (res, 1); + rp = res->d; + rp[0] = 1; + } + res->sign = 0; + goto leave; + } + + /* Normalize MOD (i.e. make its most significant bit set) as + required by mpn_divrem. This will make the intermediate values + in the calculation slightly larger, but the correct result is + obtained after a final reduction using the original MOD value. */ + mp_nlimbs = msec? msize:0; + mp = mp_marker = mpi_alloc_limb_space(msize, msec); + count_leading_zeros (mod_shift_cnt, mod->d[msize-1]); + if (mod_shift_cnt) + _gcry_mpih_lshift (mp, mod->d, msize, mod_shift_cnt); + else + MPN_COPY( mp, mod->d, msize ); + + bsize = base->nlimbs; + bsign = base->sign; + if (bsize > msize) + { + /* The base is larger than the module. Reduce it. + + Allocate (BSIZE + 1) with space for remainder and quotient. + (The quotient is (bsize - msize + 1) limbs.) */ + bp_nlimbs = bsec ? (bsize + 1):0; + bp = bp_marker = mpi_alloc_limb_space( bsize + 1, bsec ); + MPN_COPY ( bp, base->d, bsize ); + /* We don't care about the quotient, store it above the + * remainder, at BP + MSIZE. */ + _gcry_mpih_divrem( bp + msize, 0, bp, bsize, mp, msize ); + bsize = msize; + /* Canonicalize the base, since we are going to multiply with it + quite a few times. */ + MPN_NORMALIZE( bp, bsize ); + } + else + bp = base->d; + + if (!bsize) + { + res->nlimbs = 0; + res->sign = 0; + goto leave; + } + + + /* Make BASE, EXPO and MOD not overlap with RES. */ + if ( rp == bp ) + { + /* RES and BASE are identical. Allocate temp. space for BASE. */ + gcry_assert (!bp_marker); + bp_nlimbs = bsec? bsize:0; + bp = bp_marker = mpi_alloc_limb_space( bsize, bsec ); + MPN_COPY(bp, rp, bsize); + } + if ( rp == ep ) + { + /* RES and EXPO are identical. Allocate temp. space for EXPO. */ + ep_nlimbs = esec? esize:0; + ep = ep_marker = mpi_alloc_limb_space( esize, esec ); + MPN_COPY(ep, rp, esize); + } + if ( rp == mp ) + { + /* RES and MOD are identical. Allocate temporary space for MOD.*/ + gcry_assert (!mp_marker); + mp_nlimbs = msec?msize:0; + mp = mp_marker = mpi_alloc_limb_space( msize, msec ); + MPN_COPY(mp, rp, msize); + } + + /* Copy base to the result. */ + if (res->alloced < size) + { + mpi_resize (res, size); + rp = res->d; + } + MPN_COPY ( rp, bp, bsize ); + rsize = bsize; + rsign = bsign; + + /* Main processing. */ + { + mpi_size_t i; + mpi_ptr_t xp; + int c; + mpi_limb_t e; + mpi_limb_t carry_limb; + struct karatsuba_ctx karactx; + + xp_nlimbs = msec? (2 * (msize + 1)):0; + xp = xp_marker = mpi_alloc_limb_space( 2 * (msize + 1), msec ); + + memset( &karactx, 0, sizeof karactx ); + negative_result = (ep[0] & 1) && base->sign; + + i = esize - 1; + e = ep[i]; + count_leading_zeros (c, e); + e = (e << c) << 1; /* Shift the expo bits to the left, lose msb. */ + c = BITS_PER_MPI_LIMB - 1 - c; + + /* Main loop. + + Make the result be pointed to alternately by XP and RP. This + helps us avoid block copying, which would otherwise be + necessary with the overlap restrictions of + _gcry_mpih_divmod. With 50% probability the result after this + loop will be in the area originally pointed by RP (==RES->d), + and with 50% probability in the area originally pointed to by XP. */ + for (;;) + { + while (c) + { + mpi_ptr_t tp; + mpi_size_t xsize; + + /*mpih_mul_n(xp, rp, rp, rsize);*/ + if ( rsize < KARATSUBA_THRESHOLD ) + _gcry_mpih_sqr_n_basecase( xp, rp, rsize ); + else + { + if ( !tspace ) + { + tsize = 2 * rsize; + tspace = mpi_alloc_limb_space( tsize, 0 ); + } + else if ( tsize < (2*rsize) ) + { + _gcry_mpi_free_limb_space (tspace, 0); + tsize = 2 * rsize; + tspace = mpi_alloc_limb_space (tsize, 0 ); + } + _gcry_mpih_sqr_n (xp, rp, rsize, tspace); + } + + xsize = 2 * rsize; + if ( xsize > msize ) + { + _gcry_mpih_divrem(xp + msize, 0, xp, xsize, mp, msize); + xsize = msize; + } + + tp = rp; rp = xp; xp = tp; + rsize = xsize; + + /* To mitigate the Yarom/Falkner flush+reload cache + * side-channel attack on the RSA secret exponent, we do + * the multiplication regardless of the value of the + * high-bit of E. But to avoid this performance penalty + * we do it only if the exponent has been stored in secure + * memory and we can thus assume it is a secret exponent. */ + if (esec || (mpi_limb_signed_t)e < 0) + { + /*mpih_mul( xp, rp, rsize, bp, bsize );*/ + if( bsize < KARATSUBA_THRESHOLD ) + _gcry_mpih_mul ( xp, rp, rsize, bp, bsize ); + else + _gcry_mpih_mul_karatsuba_case (xp, rp, rsize, bp, bsize, + &karactx); + + xsize = rsize + bsize; + if ( xsize > msize ) + { + _gcry_mpih_divrem(xp + msize, 0, xp, xsize, mp, msize); + xsize = msize; + } + } + if ( (mpi_limb_signed_t)e < 0 ) + { + tp = rp; rp = xp; xp = tp; + rsize = xsize; + } + e <<= 1; + c--; + } + + i--; + if ( i < 0 ) + break; + e = ep[i]; + c = BITS_PER_MPI_LIMB; + } + + /* We shifted MOD, the modulo reduction argument, left + MOD_SHIFT_CNT steps. Adjust the result by reducing it with the + original MOD. + + Also make sure the result is put in RES->d (where it already + might be, see above). */ + if ( mod_shift_cnt ) + { + carry_limb = _gcry_mpih_lshift( res->d, rp, rsize, mod_shift_cnt); + rp = res->d; + if ( carry_limb ) + { + rp[rsize] = carry_limb; + rsize++; + } + } + else if (res->d != rp) + { + MPN_COPY (res->d, rp, rsize); + rp = res->d; + } + + if ( rsize >= msize ) + { + _gcry_mpih_divrem(rp + msize, 0, rp, rsize, mp, msize); + rsize = msize; + } + + /* Remove any leading zero words from the result. */ + if ( mod_shift_cnt ) + _gcry_mpih_rshift( rp, rp, rsize, mod_shift_cnt); + MPN_NORMALIZE (rp, rsize); + + _gcry_mpih_release_karatsuba_ctx (&karactx ); + } + + /* Fixup for negative results. */ + if ( negative_result && rsize ) + { + if ( mod_shift_cnt ) + _gcry_mpih_rshift( mp, mp, msize, mod_shift_cnt); + _gcry_mpih_sub( rp, mp, msize, rp, rsize); + rsize = msize; + rsign = msign; + MPN_NORMALIZE(rp, rsize); + } + gcry_assert (res->d == rp); + res->nlimbs = rsize; + res->sign = rsign; + + leave: + if (mp_marker) + _gcry_mpi_free_limb_space( mp_marker, mp_nlimbs ); + if (bp_marker) + _gcry_mpi_free_limb_space( bp_marker, bp_nlimbs ); + if (ep_marker) + _gcry_mpi_free_limb_space( ep_marker, ep_nlimbs ); + if (xp_marker) + _gcry_mpi_free_limb_space( xp_marker, xp_nlimbs ); + if (tspace) + _gcry_mpi_free_limb_space( tspace, 0 ); +} |