diff options
Diffstat (limited to 'lib/mpi/mpi-mul.c')
| -rw-r--r-- | lib/mpi/mpi-mul.c | 194 |
1 files changed, 194 insertions, 0 deletions
diff --git a/lib/mpi/mpi-mul.c b/lib/mpi/mpi-mul.c new file mode 100644 index 000000000000..1f3219e27292 --- /dev/null +++ b/lib/mpi/mpi-mul.c @@ -0,0 +1,194 @@ +/* mpi-mul.c - MPI functions + * Copyright (C) 1994, 1996 Free Software Foundation, Inc. + * Copyright (C) 1998, 2001 Free Software Foundation, Inc. + * + * This file is part of GnuPG. + * + * GnuPG 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. + * + * GnuPG 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., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA + * + * 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. + * The GNU MP Library itself is published under the LGPL; + * however I decided to publish this code under the plain GPL. + */ + +#include "mpi-internal.h" + +int mpi_mul_ui(MPI prod, MPI mult, unsigned long small_mult) +{ + mpi_size_t size, prod_size; + mpi_ptr_t prod_ptr; + mpi_limb_t cy; + int sign; + + size = mult->nlimbs; + sign = mult->sign; + + if (!size || !small_mult) { + prod->nlimbs = 0; + prod->sign = 0; + return 0; + } + + prod_size = size + 1; + if (prod->alloced < prod_size) + if (mpi_resize(prod, prod_size) < 0) + return -ENOMEM; + prod_ptr = prod->d; + + cy = mpihelp_mul_1(prod_ptr, mult->d, size, (mpi_limb_t) small_mult); + if (cy) + prod_ptr[size++] = cy; + prod->nlimbs = size; + prod->sign = sign; + return 0; +} + +int mpi_mul_2exp(MPI w, MPI u, unsigned long cnt) +{ + mpi_size_t usize, wsize, limb_cnt; + mpi_ptr_t wp; + mpi_limb_t wlimb; + int usign, wsign; + + usize = u->nlimbs; + usign = u->sign; + + if (!usize) { + w->nlimbs = 0; + w->sign = 0; + return 0; + } + + limb_cnt = cnt / BITS_PER_MPI_LIMB; + wsize = usize + limb_cnt + 1; + if (w->alloced < wsize) + if (mpi_resize(w, wsize) < 0) + return -ENOMEM; + wp = w->d; + wsize = usize + limb_cnt; + wsign = usign; + + cnt %= BITS_PER_MPI_LIMB; + if (cnt) { + wlimb = mpihelp_lshift(wp + limb_cnt, u->d, usize, cnt); + if (wlimb) { + wp[wsize] = wlimb; + wsize++; + } + } else { + MPN_COPY_DECR(wp + limb_cnt, u->d, usize); + } + + /* Zero all whole limbs at low end. Do it here and not before calling + * mpn_lshift, not to lose for U == W. */ + MPN_ZERO(wp, limb_cnt); + + w->nlimbs = wsize; + w->sign = wsign; + return 0; +} + +int mpi_mul(MPI w, MPI u, MPI v) +{ + int rc = -ENOMEM; + mpi_size_t usize, vsize, wsize; + mpi_ptr_t up, vp, wp; + mpi_limb_t cy; + int usign, vsign, sign_product; + int assign_wp = 0; + mpi_ptr_t tmp_limb = NULL; + + if (u->nlimbs < v->nlimbs) { /* Swap U and V. */ + usize = v->nlimbs; + usign = v->sign; + up = v->d; + vsize = u->nlimbs; + vsign = u->sign; + vp = u->d; + } else { + usize = u->nlimbs; + usign = u->sign; + up = u->d; + vsize = v->nlimbs; + vsign = v->sign; + vp = v->d; + } + sign_product = usign ^ vsign; + wp = w->d; + + /* Ensure W has space enough to store the result. */ + wsize = usize + vsize; + if (w->alloced < (size_t) wsize) { + if (wp == up || wp == vp) { + wp = mpi_alloc_limb_space(wsize); + if (!wp) + goto nomem; + assign_wp = 1; + } else { + if (mpi_resize(w, wsize) < 0) + goto nomem; + wp = w->d; + } + } else { /* Make U and V not overlap with W. */ + if (wp == up) { + /* W and U are identical. Allocate temporary space for U. */ + up = tmp_limb = mpi_alloc_limb_space(usize); + if (!up) + goto nomem; + /* Is V identical too? Keep it identical with U. */ + if (wp == vp) + vp = up; + /* Copy to the temporary space. */ + MPN_COPY(up, wp, usize); + } else if (wp == vp) { + /* W and V are identical. Allocate temporary space for V. */ + vp = tmp_limb = mpi_alloc_limb_space(vsize); + if (!vp) + goto nomem; + /* Copy to the temporary space. */ + MPN_COPY(vp, wp, vsize); + } + } + + if (!vsize) + wsize = 0; + else { + if (mpihelp_mul(wp, up, usize, vp, vsize, &cy) < 0) + goto nomem; + wsize -= cy ? 0 : 1; + } + + if (assign_wp) + mpi_assign_limb_space(w, wp, wsize); + + w->nlimbs = wsize; + w->sign = sign_product; + rc = 0; +nomem: + if (tmp_limb) + mpi_free_limb_space(tmp_limb); + return rc; +} + +int mpi_mulm(MPI w, MPI u, MPI v, MPI m) +{ + if (mpi_mul(w, u, v) < 0) + return -ENOMEM; + return mpi_fdiv_r(w, w, m); +} |