lib/mpi/mpicoder.c

   1 /* mpicoder.c  -  Coder for the external representation of MPIs
   2  * Copyright (C) 1998, 1999 Free Software Foundation, Inc.
   3  *
   4  * This file is part of GnuPG.
   5  *
   6  * GnuPG is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License as published by
   8  * the Free Software Foundation; either version 2 of the License, or
   9  * (at your option) any later version.
  10  *
  11  * GnuPG is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  * GNU General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU General Public License
  17  * along with this program; if not, write to the Free Software
  18  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
  19  */
  20
  21 #include <linux/bitops.h>
  22 #include <linux/count_zeros.h>
  23 #include "mpi-internal.h"
  24
  25 #define MAX_EXTERN_MPI_BITS 16384
  26
  27 /**
  28  * mpi_read_raw_data - Read a raw byte stream as a positive integer
  29  * @xbuffer: The data to read
  30  * @nbytes: The amount of data to read
  31  */
  32 MPI mpi_read_raw_data(const void *xbuffer, size_t nbytes)
  33 {
  34         const uint8_t *buffer = xbuffer;
  35         int i, j;
  36         unsigned nbits, nlimbs;
  37         mpi_limb_t a;
  38         MPI val = NULL;
  39
  40         while (nbytes > 0 && buffer[0] == 0) {
  41                 buffer++;
  42                 nbytes--;
  43         }
  44
  45         nbits = nbytes * 8;
  46         if (nbits > MAX_EXTERN_MPI_BITS) {
  47                 pr_info("MPI: mpi too large (%u bits)\n", nbits);
  48                 return NULL;
  49         }
  50         if (nbytes > 0)
  51                 nbits -= count_leading_zeros(buffer[0]);
  52         else
  53                 nbits = 0;
  54
  55         nlimbs = DIV_ROUND_UP(nbytes, BYTES_PER_MPI_LIMB);
  56         val = mpi_alloc(nlimbs);
  57         if (!val)
  58                 return NULL;
  59         val->nbits = nbits;
  60         val->sign = 0;
  61         val->nlimbs = nlimbs;
  62
  63         if (nbytes > 0) {
  64                 i = BYTES_PER_MPI_LIMB - nbytes % BYTES_PER_MPI_LIMB;
  65                 i %= BYTES_PER_MPI_LIMB;
  66                 for (j = nlimbs; j > 0; j--) {
  67                         a = 0;
  68                         for (; i < BYTES_PER_MPI_LIMB; i++) {
  69                                 a <<= 8;
  70                                 a |= *buffer++;
  71                         }
  72                         i = 0;
  73                         val->d[j - 1] = a;
  74                 }
  75         }
  76         return val;
  77 }
  78 EXPORT_SYMBOL_GPL(mpi_read_raw_data);
  79
  80 MPI mpi_read_from_buffer(const void *xbuffer, unsigned *ret_nread)
  81 {
  82         const uint8_t *buffer = xbuffer;
  83         int i, j;
  84         unsigned nbits, nbytes, nlimbs, nread = 0;
  85         mpi_limb_t a;
  86         MPI val = NULL;
  87
  88         if (*ret_nread < 2)
  89                 goto leave;
  90         nbits = buffer[0] << 8 | buffer[1];
  91
  92         if (nbits > MAX_EXTERN_MPI_BITS) {
  93                 pr_info("MPI: mpi too large (%u bits)\n", nbits);
  94                 goto leave;
  95         }
  96         buffer += 2;
  97         nread = 2;
  98
  99         nbytes = DIV_ROUND_UP(nbits, 8);
 100         nlimbs = DIV_ROUND_UP(nbytes, BYTES_PER_MPI_LIMB);
 101         val = mpi_alloc(nlimbs);
 102         if (!val)
 103                 return NULL;
 104         i = BYTES_PER_MPI_LIMB - nbytes % BYTES_PER_MPI_LIMB;
 105         i %= BYTES_PER_MPI_LIMB;
 106         val->nbits = nbits;
 107         j = val->nlimbs = nlimbs;
 108         val->sign = 0;
 109         for (; j > 0; j--) {
 110                 a = 0;
 111                 for (; i < BYTES_PER_MPI_LIMB; i++) {
 112                         if (++nread > *ret_nread) {
 113                                 printk
 114                                     ("MPI: mpi larger than buffer nread=%d ret_nread=%d\n",
 115                                      nread, *ret_nread);
 116                                 goto leave;
 117                         }
 118                         a <<= 8;
 119                         a |= *buffer++;
 120                 }
 121                 i = 0;
 122                 val->d[j - 1] = a;
 123         }
 124
 125 leave:
 126         *ret_nread = nread;
 127         return val;
 128 }
 129 EXPORT_SYMBOL_GPL(mpi_read_from_buffer);
 130
 131 /**
 132  * mpi_read_buffer() - read MPI to a bufer provided by user (msb first)
 133  *
 134  * @a:          a multi precision integer
 135  * @buf:        bufer to which the output will be written to. Needs to be at
 136  *              leaset mpi_get_size(a) long.
 137  * @buf_len:    size of the buf.
 138  * @nbytes:     receives the actual length of the data written.
 139  * @sign:       if not NULL, it will be set to the sign of a.
 140  *
 141  * Return:      0 on success or error code in case of error
 142  */
 143 int mpi_read_buffer(MPI a, uint8_t *buf, unsigned buf_len, unsigned *nbytes,
 144                     int *sign)
 145 {
 146         uint8_t *p;
 147         mpi_limb_t alimb;
 148         unsigned int n = mpi_get_size(a);
 149         int i, lzeros = 0;
 150
 151         if (buf_len < n || !buf || !nbytes)
 152                 return -EINVAL;
 153
 154         if (sign)
 155                 *sign = a->sign;
 156
 157         p = (void *)&a->d[a->nlimbs] - 1;
 158
 159         for (i = a->nlimbs * sizeof(alimb) - 1; i >= 0; i--, p--) {
 160                 if (!*p)
 161                         lzeros++;
 162                 else
 163                         break;
 164         }
 165
 166         p = buf;
 167         *nbytes = n - lzeros;
 168
 169         for (i = a->nlimbs - 1; i >= 0; i--) {
 170                 alimb = a->d[i];
 171 #if BYTES_PER_MPI_LIMB == 4
 172                 *p++ = alimb >> 24;
 173                 *p++ = alimb >> 16;
 174                 *p++ = alimb >> 8;
 175                 *p++ = alimb;
 176 #elif BYTES_PER_MPI_LIMB == 8
 177                 *p++ = alimb >> 56;
 178                 *p++ = alimb >> 48;
 179                 *p++ = alimb >> 40;
 180                 *p++ = alimb >> 32;
 181                 *p++ = alimb >> 24;
 182                 *p++ = alimb >> 16;
 183                 *p++ = alimb >> 8;
 184                 *p++ = alimb;
 185 #else
 186 #error please implement for this limb size.
 187 #endif
 188
 189                 if (lzeros > 0) {
 190                         if (lzeros >= sizeof(alimb)) {
 191                                 p -= sizeof(alimb);
 192                         } else {
 193                                 mpi_limb_t *limb1 = (void *)p - sizeof(alimb);
 194                                 mpi_limb_t *limb2 = (void *)p - sizeof(alimb)
 195                                                         + lzeros;
 196                                 *limb1 = *limb2;
 197                                 p -= lzeros;
 198                         }
 199                         lzeros -= sizeof(alimb);
 200                 }
 201         }
 202         return 0;
 203 }
 204 EXPORT_SYMBOL_GPL(mpi_read_buffer);
 205
 206 /*
 207  * mpi_get_buffer() - Returns an allocated buffer with the MPI (msb first).
 208  * Caller must free the return string.
 209  * This function does return a 0 byte buffer with nbytes set to zero if the
 210  * value of A is zero.
 211  *
 212  * @a:          a multi precision integer.
 213  * @nbytes:     receives the length of this buffer.
 214  * @sign:       if not NULL, it will be set to the sign of the a.
 215  *
 216  * Return:      Pointer to MPI buffer or NULL on error
 217  */
 218 void *mpi_get_buffer(MPI a, unsigned *nbytes, int *sign)
 219 {
 220         uint8_t *buf;
 221         unsigned int n;
 222         int ret;
 223
 224         if (!nbytes)
 225                 return NULL;
 226
 227         n = mpi_get_size(a);
 228
 229         if (!n)
 230                 n++;
 231
 232         buf = kmalloc(n, GFP_KERNEL);
 233
 234         if (!buf)
 235                 return NULL;
 236
 237         ret = mpi_read_buffer(a, buf, n, nbytes, sign);
 238
 239         if (ret) {
 240                 kfree(buf);
 241                 return NULL;
 242         }
 243         return buf;
 244 }
 245 EXPORT_SYMBOL_GPL(mpi_get_buffer);
 246
 247 /****************
 248  * Use BUFFER to update MPI.
 249  */
 250 int mpi_set_buffer(MPI a, const void *xbuffer, unsigned nbytes, int sign)
 251 {
 252         const uint8_t *buffer = xbuffer, *p;
 253         mpi_limb_t alimb;
 254         int nlimbs;
 255         int i;
 256
 257         nlimbs = DIV_ROUND_UP(nbytes, BYTES_PER_MPI_LIMB);
 258         if (RESIZE_IF_NEEDED(a, nlimbs) < 0)
 259                 return -ENOMEM;
 260         a->sign = sign;
 261
 262         for (i = 0, p = buffer + nbytes - 1; p >= buffer + BYTES_PER_MPI_LIMB;) {
 263 #if BYTES_PER_MPI_LIMB == 4
 264                 alimb = (mpi_limb_t) *p--;
 265                 alimb |= (mpi_limb_t) *p-- << 8;
 266                 alimb |= (mpi_limb_t) *p-- << 16;
 267                 alimb |= (mpi_limb_t) *p-- << 24;
 268 #elif BYTES_PER_MPI_LIMB == 8
 269                 alimb = (mpi_limb_t) *p--;
 270                 alimb |= (mpi_limb_t) *p-- << 8;
 271                 alimb |= (mpi_limb_t) *p-- << 16;
 272                 alimb |= (mpi_limb_t) *p-- << 24;
 273                 alimb |= (mpi_limb_t) *p-- << 32;
 274                 alimb |= (mpi_limb_t) *p-- << 40;
 275                 alimb |= (mpi_limb_t) *p-- << 48;
 276                 alimb |= (mpi_limb_t) *p-- << 56;
 277 #else
 278 #error please implement for this limb size.
 279 #endif
 280                 a->d[i++] = alimb;
 281         }
 282         if (p >= buffer) {
 283 #if BYTES_PER_MPI_LIMB == 4
 284                 alimb = *p--;
 285                 if (p >= buffer)
 286                         alimb |= (mpi_limb_t) *p-- << 8;
 287                 if (p >= buffer)
 288                         alimb |= (mpi_limb_t) *p-- << 16;
 289                 if (p >= buffer)
 290                         alimb |= (mpi_limb_t) *p-- << 24;
 291 #elif BYTES_PER_MPI_LIMB == 8
 292                 alimb = (mpi_limb_t) *p--;
 293                 if (p >= buffer)
 294                         alimb |= (mpi_limb_t) *p-- << 8;
 295                 if (p >= buffer)
 296                         alimb |= (mpi_limb_t) *p-- << 16;
 297                 if (p >= buffer)
 298                         alimb |= (mpi_limb_t) *p-- << 24;
 299                 if (p >= buffer)
 300                         alimb |= (mpi_limb_t) *p-- << 32;
 301                 if (p >= buffer)
 302                         alimb |= (mpi_limb_t) *p-- << 40;
 303                 if (p >= buffer)
 304                         alimb |= (mpi_limb_t) *p-- << 48;
 305                 if (p >= buffer)
 306                         alimb |= (mpi_limb_t) *p-- << 56;
 307 #else
 308 #error please implement for this limb size.
 309 #endif
 310                 a->d[i++] = alimb;
 311         }
 312         a->nlimbs = i;
 313
 314         if (i != nlimbs) {
 315                 pr_emerg("MPI: mpi_set_buffer: Assertion failed (%d != %d)", i,
 316                        nlimbs);
 317                 BUG();
 318         }
 319         return 0;
 320 }
 321 EXPORT_SYMBOL_GPL(mpi_set_buffer);
 322
 323 /**
 324  * mpi_write_to_sgl() - Funnction exports MPI to an sgl (msb first)
 325  *
 326  * This function works in the same way as the mpi_read_buffer, but it
 327  * takes an sgl instead of u8 * buf.
 328  *
 329  * @a:          a multi precision integer
 330  * @sgl:        scatterlist to write to. Needs to be at least
 331  *              mpi_get_size(a) long.
 332  * @nbytes:     in/out param - it has the be set to the maximum number of
 333  *              bytes that can be written to sgl. This has to be at least
 334  *              the size of the integer a. On return it receives the actual
 335  *              length of the data written.
 336  * @sign:       if not NULL, it will be set to the sign of a.
 337  *
 338  * Return:      0 on success or error code in case of error
 339  */
 340 int mpi_write_to_sgl(MPI a, struct scatterlist *sgl, unsigned *nbytes,
 341                      int *sign)
 342 {
 343         u8 *p, *p2;
 344         mpi_limb_t alimb, alimb2;
 345         unsigned int n = mpi_get_size(a);
 346         int i, x, y = 0, lzeros = 0, buf_len;
 347
 348         if (!nbytes || *nbytes < n)
 349                 return -EINVAL;
 350
 351         if (sign)
 352                 *sign = a->sign;
 353
 354         p = (void *)&a->d[a->nlimbs] - 1;
 355
 356         for (i = a->nlimbs * sizeof(alimb) - 1; i >= 0; i--, p--) {
 357                 if (!*p)
 358                         lzeros++;
 359                 else
 360                         break;
 361         }
 362
 363         *nbytes = n - lzeros;
 364         buf_len = sgl->length;
 365         p2 = sg_virt(sgl);
 366
 367         for (i = a->nlimbs - 1; i >= 0; i--) {
 368                 alimb = a->d[i];
 369                 p = (u8 *)&alimb2;
 370 #if BYTES_PER_MPI_LIMB == 4
 371                 *p++ = alimb >> 24;
 372                 *p++ = alimb >> 16;
 373                 *p++ = alimb >> 8;
 374                 *p++ = alimb;
 375 #elif BYTES_PER_MPI_LIMB == 8
 376                 *p++ = alimb >> 56;
 377                 *p++ = alimb >> 48;
 378                 *p++ = alimb >> 40;
 379                 *p++ = alimb >> 32;
 380                 *p++ = alimb >> 24;
 381                 *p++ = alimb >> 16;
 382                 *p++ = alimb >> 8;
 383                 *p++ = alimb;
 384 #else
 385 #error please implement for this limb size.
 386 #endif
 387                 if (lzeros > 0) {
 388                         if (lzeros >= sizeof(alimb)) {
 389                                 p -= sizeof(alimb);
 390                                 continue;
 391                         } else {
 392                                 mpi_limb_t *limb1 = (void *)p - sizeof(alimb);
 393                                 mpi_limb_t *limb2 = (void *)p - sizeof(alimb)
 394                                                         + lzeros;
 395                                 *limb1 = *limb2;
 396                                 p -= lzeros;
 397                                 y = lzeros;
 398                         }
 399                         lzeros -= sizeof(alimb);
 400                 }
 401
 402                 p = p - (sizeof(alimb) - y);
 403
 404                 for (x = 0; x < sizeof(alimb) - y; x++) {
 405                         if (!buf_len) {
 406                                 sgl = sg_next(sgl);
 407                                 if (!sgl)
 408                                         return -EINVAL;
 409                                 buf_len = sgl->length;
 410                                 p2 = sg_virt(sgl);
 411                         }
 412                         *p2++ = *p++;
 413                         buf_len--;
 414                 }
 415                 y = 0;
 416         }
 417         return 0;
 418 }
 419 EXPORT_SYMBOL_GPL(mpi_write_to_sgl);
 420
 421 /*
 422  * mpi_read_raw_from_sgl() - Function allocates an MPI and populates it with
 423  *                           data from the sgl
 424  *
 425  * This function works in the same way as the mpi_read_raw_data, but it
 426  * takes an sgl instead of void * buffer. i.e. it allocates
 427  * a new MPI and reads the content of the sgl to the MPI.
 428  *
 429  * @sgl:        scatterlist to read from
 430  * @len:        number of bytes to read
 431  *
 432  * Return:      Pointer to a new MPI or NULL on error
 433  */
 434 MPI mpi_read_raw_from_sgl(struct scatterlist *sgl, unsigned int len)
 435 {
 436         struct scatterlist *sg;
 437         int x, i, j, z, lzeros, ents;
 438         unsigned int nbits, nlimbs, nbytes;
 439         mpi_limb_t a;
 440         MPI val = NULL;
 441
 442         lzeros = 0;
 443         ents = sg_nents(sgl);
 444
 445         for_each_sg(sgl, sg, ents, i) {
 446                 const u8 *buff = sg_virt(sg);
 447                 int len = sg->length;
 448
 449                 while (len && !*buff) {
 450                         lzeros++;
 451                         len--;
 452                         buff++;
 453                 }
 454
 455                 if (len && *buff)
 456                         break;
 457
 458                 ents--;
 459                 lzeros = 0;
 460         }
 461
 462         sgl = sg;
 463
 464         if (!ents)
 465                 nbytes = 0;
 466         else
 467                 nbytes = len - lzeros;
 468
 469         nbits = nbytes * 8;
 470         if (nbits > MAX_EXTERN_MPI_BITS) {
 471                 pr_info("MPI: mpi too large (%u bits)\n", nbits);
 472                 return NULL;
 473         }
 474
 475         if (nbytes > 0)
 476                 nbits -= count_leading_zeros(*(u8 *)(sg_virt(sgl) + lzeros));
 477         else
 478                 nbits = 0;
 479
 480         nlimbs = DIV_ROUND_UP(nbytes, BYTES_PER_MPI_LIMB);
 481         val = mpi_alloc(nlimbs);
 482         if (!val)
 483                 return NULL;
 484
 485         val->nbits = nbits;
 486         val->sign = 0;
 487         val->nlimbs = nlimbs;
 488
 489         if (nbytes == 0)
 490                 return val;
 491
 492         j = nlimbs - 1;
 493         a = 0;
 494         z = 0;
 495         x = BYTES_PER_MPI_LIMB - nbytes % BYTES_PER_MPI_LIMB;
 496         x %= BYTES_PER_MPI_LIMB;
 497
 498         for_each_sg(sgl, sg, ents, i) {
 499                 const u8 *buffer = sg_virt(sg) + lzeros;
 500                 int len = sg->length - lzeros;
 501                 int buf_shift = x;
 502
 503                 if  (sg_is_last(sg) && (len % BYTES_PER_MPI_LIMB))
 504                         len += BYTES_PER_MPI_LIMB - (len % BYTES_PER_MPI_LIMB);
 505
 506                 for (; x < len + buf_shift; x++) {
 507                         a <<= 8;
 508                         a |= *buffer++;
 509                         if (((z + x + 1) % BYTES_PER_MPI_LIMB) == 0) {
 510                                 val->d[j--] = a;
 511                                 a = 0;
 512                         }
 513                 }
 514                 z += x;
 515                 x = 0;
 516                 lzeros = 0;
 517         }
 518         return val;
 519 }
 520 EXPORT_SYMBOL_GPL(mpi_read_raw_from_sgl);