lib/mpi/mpiutil.c

0001 /* mpiutil.ac  -  Utility functions for MPI
0002  * Copyright (C) 1998, 1999 Free Software Foundation, Inc.
0003  *
0004  * This file is part of GnuPG.
0005  *
0006  * GnuPG is free software; you can redistribute it and/or modify
0007  * it under the terms of the GNU General Public License as published by
0008  * the Free Software Foundation; either version 2 of the License, or
0009  * (at your option) any later version.
0010  *
0011  * GnuPG is distributed in the hope that it will be useful,
0012  * but WITHOUT ANY WARRANTY; without even the implied warranty of
0013  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
0014  * GNU General Public License for more details.
0015  *
0016  * You should have received a copy of the GNU General Public License
0017  * along with this program; if not, write to the Free Software
0018  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
0019  */
0020
0021 #include "mpi-internal.h"
0022
0023 /* Constants allocated right away at startup.  */
0024 static MPI constants[MPI_NUMBER_OF_CONSTANTS];
0025
0026 /* Initialize the MPI subsystem.  This is called early and allows to
0027  * do some initialization without taking care of threading issues.
0028  */
0029 static int __init mpi_init(void)
0030 {
0031     int idx;
0032     unsigned long value;
0033
0034     for (idx = 0; idx < MPI_NUMBER_OF_CONSTANTS; idx++) {
0035         switch (idx) {
0036         case MPI_C_ZERO:
0037             value = 0;
0038             break;
0039         case MPI_C_ONE:
0040             value = 1;
0041             break;
0042         case MPI_C_TWO:
0043             value = 2;
0044             break;
0045         case MPI_C_THREE:
0046             value = 3;
0047             break;
0048         case MPI_C_FOUR:
0049             value = 4;
0050             break;
0051         case MPI_C_EIGHT:
0052             value = 8;
0053             break;
0054         default:
0055             pr_err("MPI: invalid mpi_const selector %d\n", idx);
0056             return -EFAULT;
0057         }
0058         constants[idx] = mpi_alloc_set_ui(value);
0059         constants[idx]->flags = (16|32);
0060     }
0061
0062     return 0;
0063 }
0064 postcore_initcall(mpi_init);
0065
0066 /* Return a constant MPI descripbed by NO which is one of the
0067  * MPI_C_xxx macros.  There is no need to copy this returned value; it
0068  * may be used directly.
0069  */
0070 MPI mpi_const(enum gcry_mpi_constants no)
0071 {
0072     if ((int)no < 0 || no > MPI_NUMBER_OF_CONSTANTS)
0073         pr_err("MPI: invalid mpi_const selector %d\n", no);
0074     if (!constants[no])
0075         pr_err("MPI: MPI subsystem not initialized\n");
0076     return constants[no];
0077 }
0078 EXPORT_SYMBOL_GPL(mpi_const);
0079
0080 /****************
0081  * Note:  It was a bad idea to use the number of limbs to allocate
0082  *    because on a alpha the limbs are large but we normally need
0083  *    integers of n bits - So we should change this to bits (or bytes).
0084  *
0085  *    But mpi_alloc is used in a lot of places :-)
0086  */
0087 MPI mpi_alloc(unsigned nlimbs)
0088 {
0089     MPI a;
0090
0091     a = kmalloc(sizeof *a, GFP_KERNEL);
0092     if (!a)
0093         return a;
0094
0095     if (nlimbs) {
0096         a->d = mpi_alloc_limb_space(nlimbs);
0097         if (!a->d) {
0098             kfree(a);
0099             return NULL;
0100         }
0101     } else {
0102         a->d = NULL;
0103     }
0104
0105     a->alloced = nlimbs;
0106     a->nlimbs = 0;
0107     a->sign = 0;
0108     a->flags = 0;
0109     a->nbits = 0;
0110     return a;
0111 }
0112 EXPORT_SYMBOL_GPL(mpi_alloc);
0113
0114 mpi_ptr_t mpi_alloc_limb_space(unsigned nlimbs)
0115 {
0116     size_t len = nlimbs * sizeof(mpi_limb_t);
0117
0118     if (!len)
0119         return NULL;
0120
0121     return kmalloc(len, GFP_KERNEL);
0122 }
0123
0124 void mpi_free_limb_space(mpi_ptr_t a)
0125 {
0126     if (!a)
0127         return;
0128
0129     kfree_sensitive(a);
0130 }
0131
0132 void mpi_assign_limb_space(MPI a, mpi_ptr_t ap, unsigned nlimbs)
0133 {
0134     mpi_free_limb_space(a->d);
0135     a->d = ap;
0136     a->alloced = nlimbs;
0137 }
0138
0139 /****************
0140  * Resize the array of A to NLIMBS. the additional space is cleared
0141  * (set to 0) [done by m_realloc()]
0142  */
0143 int mpi_resize(MPI a, unsigned nlimbs)
0144 {
0145     void *p;
0146
0147     if (nlimbs <= a->alloced)
0148         return 0;   /* no need to do it */
0149
0150     if (a->d) {
0151         p = kcalloc(nlimbs, sizeof(mpi_limb_t), GFP_KERNEL);
0152         if (!p)
0153             return -ENOMEM;
0154         memcpy(p, a->d, a->alloced * sizeof(mpi_limb_t));
0155         kfree_sensitive(a->d);
0156         a->d = p;
0157     } else {
0158         a->d = kcalloc(nlimbs, sizeof(mpi_limb_t), GFP_KERNEL);
0159         if (!a->d)
0160             return -ENOMEM;
0161     }
0162     a->alloced = nlimbs;
0163     return 0;
0164 }
0165
0166 void mpi_clear(MPI a)
0167 {
0168     if (!a)
0169         return;
0170     a->nlimbs = 0;
0171     a->flags = 0;
0172 }
0173 EXPORT_SYMBOL_GPL(mpi_clear);
0174
0175 void mpi_free(MPI a)
0176 {
0177     if (!a)
0178         return;
0179
0180     if (a->flags & 4)
0181         kfree_sensitive(a->d);
0182     else
0183         mpi_free_limb_space(a->d);
0184
0185     if (a->flags & ~7)
0186         pr_info("invalid flag value in mpi\n");
0187     kfree(a);
0188 }
0189 EXPORT_SYMBOL_GPL(mpi_free);
0190
0191 /****************
0192  * Note: This copy function should not interpret the MPI
0193  *   but copy it transparently.
0194  */
0195 MPI mpi_copy(MPI a)
0196 {
0197     int i;
0198     MPI b;
0199
0200     if (a) {
0201         b = mpi_alloc(a->nlimbs);
0202         b->nlimbs = a->nlimbs;
0203         b->sign = a->sign;
0204         b->flags = a->flags;
0205         b->flags &= ~(16|32); /* Reset the immutable and constant flags. */
0206         for (i = 0; i < b->nlimbs; i++)
0207             b->d[i] = a->d[i];
0208     } else
0209         b = NULL;
0210     return b;
0211 }
0212
0213 /****************
0214  * This function allocates an MPI which is optimized to hold
0215  * a value as large as the one given in the argument and allocates it
0216  * with the same flags as A.
0217  */
0218 MPI mpi_alloc_like(MPI a)
0219 {
0220     MPI b;
0221
0222     if (a) {
0223         b = mpi_alloc(a->nlimbs);
0224         b->nlimbs = 0;
0225         b->sign = 0;
0226         b->flags = a->flags;
0227     } else
0228         b = NULL;
0229
0230     return b;
0231 }
0232
0233
0234 /* Set U into W and release U.  If W is NULL only U will be released. */
0235 void mpi_snatch(MPI w, MPI u)
0236 {
0237     if (w) {
0238         mpi_assign_limb_space(w, u->d, u->alloced);
0239         w->nlimbs = u->nlimbs;
0240         w->sign   = u->sign;
0241         w->flags  = u->flags;
0242         u->alloced = 0;
0243         u->nlimbs = 0;
0244         u->d = NULL;
0245     }
0246     mpi_free(u);
0247 }
0248
0249
0250 MPI mpi_set(MPI w, MPI u)
0251 {
0252     mpi_ptr_t wp, up;
0253     mpi_size_t usize = u->nlimbs;
0254     int usign = u->sign;
0255
0256     if (!w)
0257         w = mpi_alloc(mpi_get_nlimbs(u));
0258     RESIZE_IF_NEEDED(w, usize);
0259     wp = w->d;
0260     up = u->d;
0261     MPN_COPY(wp, up, usize);
0262     w->nlimbs = usize;
0263     w->flags = u->flags;
0264     w->flags &= ~(16|32); /* Reset the immutable and constant flags.  */
0265     w->sign = usign;
0266     return w;
0267 }
0268 EXPORT_SYMBOL_GPL(mpi_set);
0269
0270 MPI mpi_set_ui(MPI w, unsigned long u)
0271 {
0272     if (!w)
0273         w = mpi_alloc(1);
0274     /* FIXME: If U is 0 we have no need to resize and thus possible
0275      * allocating the limbs.
0276      */
0277     RESIZE_IF_NEEDED(w, 1);
0278     w->d[0] = u;
0279     w->nlimbs = u ? 1 : 0;
0280     w->sign = 0;
0281     w->flags = 0;
0282     return w;
0283 }
0284 EXPORT_SYMBOL_GPL(mpi_set_ui);
0285
0286 MPI mpi_alloc_set_ui(unsigned long u)
0287 {
0288     MPI w = mpi_alloc(1);
0289     w->d[0] = u;
0290     w->nlimbs = u ? 1 : 0;
0291     w->sign = 0;
0292     return w;
0293 }
0294
0295 /****************
0296  * Swap the value of A and B, when SWAP is 1.
0297  * Leave the value when SWAP is 0.
0298  * This implementation should be constant-time regardless of SWAP.
0299  */
0300 void mpi_swap_cond(MPI a, MPI b, unsigned long swap)
0301 {
0302     mpi_size_t i;
0303     mpi_size_t nlimbs;
0304     mpi_limb_t mask = ((mpi_limb_t)0) - swap;
0305     mpi_limb_t x;
0306
0307     if (a->alloced > b->alloced)
0308         nlimbs = b->alloced;
0309     else
0310         nlimbs = a->alloced;
0311     if (a->nlimbs > nlimbs || b->nlimbs > nlimbs)
0312         return;
0313
0314     for (i = 0; i < nlimbs; i++) {
0315         x = mask & (a->d[i] ^ b->d[i]);
0316         a->d[i] = a->d[i] ^ x;
0317         b->d[i] = b->d[i] ^ x;
0318     }
0319
0320     x = mask & (a->nlimbs ^ b->nlimbs);
0321     a->nlimbs = a->nlimbs ^ x;
0322     b->nlimbs = b->nlimbs ^ x;
0323
0324     x = mask & (a->sign ^ b->sign);
0325     a->sign = a->sign ^ x;
0326     b->sign = b->sign ^ x;
0327 }
0328
0329 MODULE_DESCRIPTION("Multiprecision maths library");
0330 MODULE_LICENSE("GPL");