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 on success and
 139  *              the data to-be-written on -EOVERFLOW in case buf_len was too
 140  *              small.
 141  * @sign:       if not NULL, it will be set to the sign of a.
 142  *
 143  * Return:      0 on success or error code in case of error
 144  */
 145 int mpi_read_buffer(MPI a, uint8_t *buf, unsigned buf_len, unsigned *nbytes,
 146                     int *sign)
 147 {
 148         uint8_t *p;
 149         mpi_limb_t alimb;
 150         unsigned int n = mpi_get_size(a);
 151         int i, lzeros = 0;
 152
 153         if (!buf || !nbytes)
 154                 return -EINVAL;
 155
 156         if (sign)
 157                 *sign = a->sign;
 158
 159         p = (void *)&a->d[a->nlimbs] - 1;
 160
 161         for (i = a->nlimbs * sizeof(alimb) - 1; i >= 0; i--, p--) {
 162                 if (!*p)
 163                         lzeros++;
 164                 else
 165                         break;
 166         }
 167
 168         if (buf_len < n - lzeros) {
 169                 *nbytes = n - lzeros;
 170                 return -EOVERFLOW;
 171         }
 172
 173         p = buf;
 174         *nbytes = n - lzeros;
 175
 176         for (i = a->nlimbs - 1; i >= 0; i--) {
 177                 alimb = a->d[i];
 178 #if BYTES_PER_MPI_LIMB == 4
 179                 *p++ = alimb >> 24;
 180                 *p++ = alimb >> 16;
 181                 *p++ = alimb >> 8;
 182                 *p++ = alimb;
 183 #elif BYTES_PER_MPI_LIMB == 8
 184                 *p++ = alimb >> 56;
 185                 *p++ = alimb >> 48;
 186                 *p++ = alimb >> 40;
 187                 *p++ = alimb >> 32;
 188                 *p++ = alimb >> 24;
 189                 *p++ = alimb >> 16;
 190                 *p++ = alimb >> 8;
 191                 *p++ = alimb;
 192 #else
 193 #error please implement for this limb size.
 194 #endif
 195
 196                 if (lzeros > 0) {
 197                         if (lzeros >= sizeof(alimb)) {
 198                                 p -= sizeof(alimb);
 199                         } else {
 200                                 mpi_limb_t *limb1 = (void *)p - sizeof(alimb);
 201                                 mpi_limb_t *limb2 = (void *)p - sizeof(alimb)
 202                                                         + lzeros;
 203                                 *limb1 = *limb2;
 204                                 p -= lzeros;
 205                         }
 206                         lzeros -= sizeof(alimb);
 207                 }
 208         }
 209         return 0;
 210 }
 211 EXPORT_SYMBOL_GPL(mpi_read_buffer);
 212
 213 /*
 214  * mpi_get_buffer() - Returns an allocated buffer with the MPI (msb first).
 215  * Caller must free the return string.
 216  * This function does return a 0 byte buffer with nbytes set to zero if the
 217  * value of A is zero.
 218  *
 219  * @a:          a multi precision integer.
 220  * @nbytes:     receives the length of this buffer.
 221  * @sign:       if not NULL, it will be set to the sign of the a.
 222  *
 223  * Return:      Pointer to MPI buffer or NULL on error
 224  */
 225 void *mpi_get_buffer(MPI a, unsigned *nbytes, int *sign)
 226 {
 227         uint8_t *buf;
 228         unsigned int n;
 229         int ret;
 230
 231         if (!nbytes)
 232                 return NULL;
 233
 234         n = mpi_get_size(a);
 235
 236         if (!n)
 237                 n++;
 238
 239         buf = kmalloc(n, GFP_KERNEL);
 240
 241         if (!buf)
 242                 return NULL;
 243
 244         ret = mpi_read_buffer(a, buf, n, nbytes, sign);
 245
 246         if (ret) {
 247                 kfree(buf);
 248                 return NULL;
 249         }
 250         return buf;
 251 }
 252 EXPORT_SYMBOL_GPL(mpi_get_buffer);
 253
 254 /****************
 255  * Use BUFFER to update MPI.
 256  */
 257 int mpi_set_buffer(MPI a, const void *xbuffer, unsigned nbytes, int sign)
 258 {
 259         const uint8_t *buffer = xbuffer, *p;
 260         mpi_limb_t alimb;
 261         int nlimbs;
 262         int i;
 263
 264         nlimbs = DIV_ROUND_UP(nbytes, BYTES_PER_MPI_LIMB);
 265         if (RESIZE_IF_NEEDED(a, nlimbs) < 0)
 266                 return -ENOMEM;
 267         a->sign = sign;
 268
 269         for (i = 0, p = buffer + nbytes - 1; p >= buffer + BYTES_PER_MPI_LIMB;) {
 270 #if BYTES_PER_MPI_LIMB == 4
 271                 alimb = (mpi_limb_t) *p--;
 272                 alimb |= (mpi_limb_t) *p-- << 8;
 273                 alimb |= (mpi_limb_t) *p-- << 16;
 274                 alimb |= (mpi_limb_t) *p-- << 24;
 275 #elif BYTES_PER_MPI_LIMB == 8
 276                 alimb = (mpi_limb_t) *p--;
 277                 alimb |= (mpi_limb_t) *p-- << 8;
 278                 alimb |= (mpi_limb_t) *p-- << 16;
 279                 alimb |= (mpi_limb_t) *p-- << 24;
 280                 alimb |= (mpi_limb_t) *p-- << 32;
 281                 alimb |= (mpi_limb_t) *p-- << 40;
 282                 alimb |= (mpi_limb_t) *p-- << 48;
 283                 alimb |= (mpi_limb_t) *p-- << 56;
 284 #else
 285 #error please implement for this limb size.
 286 #endif
 287                 a->d[i++] = alimb;
 288         }
 289         if (p >= buffer) {
 290 #if BYTES_PER_MPI_LIMB == 4
 291                 alimb = *p--;
 292                 if (p >= buffer)
 293                         alimb |= (mpi_limb_t) *p-- << 8;
 294                 if (p >= buffer)
 295                         alimb |= (mpi_limb_t) *p-- << 16;
 296                 if (p >= buffer)
 297                         alimb |= (mpi_limb_t) *p-- << 24;
 298 #elif BYTES_PER_MPI_LIMB == 8
 299                 alimb = (mpi_limb_t) *p--;
 300                 if (p >= buffer)
 301                         alimb |= (mpi_limb_t) *p-- << 8;
 302                 if (p >= buffer)
 303                         alimb |= (mpi_limb_t) *p-- << 16;
 304                 if (p >= buffer)
 305                         alimb |= (mpi_limb_t) *p-- << 24;
 306                 if (p >= buffer)
 307                         alimb |= (mpi_limb_t) *p-- << 32;
 308                 if (p >= buffer)
 309                         alimb |= (mpi_limb_t) *p-- << 40;
 310                 if (p >= buffer)
 311                         alimb |= (mpi_limb_t) *p-- << 48;
 312                 if (p >= buffer)
 313                         alimb |= (mpi_limb_t) *p-- << 56;
 314 #else
 315 #error please implement for this limb size.
 316 #endif
 317                 a->d[i++] = alimb;
 318         }
 319         a->nlimbs = i;
 320
 321         if (i != nlimbs) {
 322                 pr_emerg("MPI: mpi_set_buffer: Assertion failed (%d != %d)", i,
 323                        nlimbs);
 324                 BUG();
 325         }
 326         return 0;
 327 }
 328 EXPORT_SYMBOL_GPL(mpi_set_buffer);
 329
 330 /**
 331  * mpi_write_to_sgl() - Funnction exports MPI to an sgl (msb first)
 332  *
 333  * This function works in the same way as the mpi_read_buffer, but it
 334  * takes an sgl instead of u8 * buf.
 335  *
 336  * @a:          a multi precision integer
 337  * @sgl:        scatterlist to write to. Needs to be at least
 338  *              mpi_get_size(a) long.
 339  * @nbytes:     in/out param - it has the be set to the maximum number of
 340  *              bytes that can be written to sgl. This has to be at least
 341  *              the size of the integer a. On return it receives the actual
 342  *              length of the data written on success or the data that would
 343  *              be written if buffer was too small.
 344  * @sign:       if not NULL, it will be set to the sign of a.
 345  *
 346  * Return:      0 on success or error code in case of error
 347  */
 348 int mpi_write_to_sgl(MPI a, struct scatterlist *sgl, unsigned *nbytes,
 349                      int *sign)
 350 {
 351         u8 *p, *p2;
 352         mpi_limb_t alimb, alimb2;
 353         unsigned int n = mpi_get_size(a);
 354         int i, x, y = 0, lzeros = 0, buf_len;
 355
 356         if (!nbytes)
 357                 return -EINVAL;
 358
 359         if (sign)
 360                 *sign = a->sign;
 361
 362         p = (void *)&a->d[a->nlimbs] - 1;
 363
 364         for (i = a->nlimbs * sizeof(alimb) - 1; i >= 0; i--, p--) {
 365                 if (!*p)
 366                         lzeros++;
 367                 else
 368                         break;
 369         }
 370
 371         if (*nbytes < n - lzeros) {
 372                 *nbytes = n - lzeros;
 373                 return -EOVERFLOW;
 374         }
 375
 376         *nbytes = n - lzeros;
 377         buf_len = sgl->length;
 378         p2 = sg_virt(sgl);
 379
 380         for (i = a->nlimbs - 1; i >= 0; i--) {
 381                 alimb = a->d[i];
 382                 p = (u8 *)&alimb2;
 383 #if BYTES_PER_MPI_LIMB == 4
 384                 *p++ = alimb >> 24;
 385                 *p++ = alimb >> 16;
 386                 *p++ = alimb >> 8;
 387                 *p++ = alimb;
 388 #elif BYTES_PER_MPI_LIMB == 8
 389                 *p++ = alimb >> 56;
 390                 *p++ = alimb >> 48;
 391                 *p++ = alimb >> 40;
 392                 *p++ = alimb >> 32;
 393                 *p++ = alimb >> 24;
 394                 *p++ = alimb >> 16;
 395                 *p++ = alimb >> 8;
 396                 *p++ = alimb;
 397 #else
 398 #error please implement for this limb size.
 399 #endif
 400                 if (lzeros > 0) {
 401                         if (lzeros >= sizeof(alimb)) {
 402                                 p -= sizeof(alimb);
 403                                 continue;
 404                         } else {
 405                                 mpi_limb_t *limb1 = (void *)p - sizeof(alimb);
 406                                 mpi_limb_t *limb2 = (void *)p - sizeof(alimb)
 407                                                         + lzeros;
 408                                 *limb1 = *limb2;
 409                                 p -= lzeros;
 410                                 y = lzeros;
 411                         }
 412                         lzeros -= sizeof(alimb);
 413                 }
 414
 415                 p = p - (sizeof(alimb) - y);
 416
 417                 for (x = 0; x < sizeof(alimb) - y; x++) {
 418                         if (!buf_len) {
 419                                 sgl = sg_next(sgl);
 420                                 if (!sgl)
 421                                         return -EINVAL;
 422                                 buf_len = sgl->length;
 423                                 p2 = sg_virt(sgl);
 424                         }
 425                         *p2++ = *p++;
 426                         buf_len--;
 427                 }
 428                 y = 0;
 429         }
 430         return 0;
 431 }
 432 EXPORT_SYMBOL_GPL(mpi_write_to_sgl);
 433
 434 /*
 435  * mpi_read_raw_from_sgl() - Function allocates an MPI and populates it with
 436  *                           data from the sgl
 437  *
 438  * This function works in the same way as the mpi_read_raw_data, but it
 439  * takes an sgl instead of void * buffer. i.e. it allocates
 440  * a new MPI and reads the content of the sgl to the MPI.
 441  *
 442  * @sgl:        scatterlist to read from
 443  * @len:        number of bytes to read
 444  *
 445  * Return:      Pointer to a new MPI or NULL on error
 446  */
 447 MPI mpi_read_raw_from_sgl(struct scatterlist *sgl, unsigned int len)
 448 {
 449         struct scatterlist *sg;
 450         int x, i, j, z, lzeros, ents;
 451         unsigned int nbits, nlimbs, nbytes;
 452         mpi_limb_t a;
 453         MPI val = NULL;
 454
 455         lzeros = 0;
 456         ents = sg_nents(sgl);
 457
 458         for_each_sg(sgl, sg, ents, i) {
 459                 const u8 *buff = sg_virt(sg);
 460                 int len = sg->length;
 461
 462                 while (len && !*buff) {
 463                         lzeros++;
 464                         len--;
 465                         buff++;
 466                 }
 467
 468                 if (len && *buff)
 469                         break;
 470
 471                 ents--;
 472                 lzeros = 0;
 473         }
 474
 475         sgl = sg;
 476
 477         if (!ents)
 478                 nbytes = 0;
 479         else
 480                 nbytes = len - lzeros;
 481
 482         nbits = nbytes * 8;
 483         if (nbits > MAX_EXTERN_MPI_BITS) {
 484                 pr_info("MPI: mpi too large (%u bits)\n", nbits);
 485                 return NULL;
 486         }
 487
 488         if (nbytes > 0)
 489                 nbits -= count_leading_zeros(*(u8 *)(sg_virt(sgl) + lzeros));
 490         else
 491                 nbits = 0;
 492
 493         nlimbs = DIV_ROUND_UP(nbytes, BYTES_PER_MPI_LIMB);
 494         val = mpi_alloc(nlimbs);
 495         if (!val)
 496                 return NULL;
 497
 498         val->nbits = nbits;
 499         val->sign = 0;
 500         val->nlimbs = nlimbs;
 501
 502         if (nbytes == 0)
 503                 return val;
 504
 505         j = nlimbs - 1;
 506         a = 0;
 507         z = 0;
 508         x = BYTES_PER_MPI_LIMB - nbytes % BYTES_PER_MPI_LIMB;
 509         x %= BYTES_PER_MPI_LIMB;
 510
 511         for_each_sg(sgl, sg, ents, i) {
 512                 const u8 *buffer = sg_virt(sg) + lzeros;
 513                 int len = sg->length - lzeros;
 514                 int buf_shift = x;
 515
 516                 if  (sg_is_last(sg) && (len % BYTES_PER_MPI_LIMB))
 517                         len += BYTES_PER_MPI_LIMB - (len % BYTES_PER_MPI_LIMB);
 518
 519                 for (; x < len + buf_shift; x++) {
 520                         a <<= 8;
 521                         a |= *buffer++;
 522                         if (((z + x + 1) % BYTES_PER_MPI_LIMB) == 0) {
 523                                 val->d[j--] = a;
 524                                 a = 0;
 525                         }
 526                 }
 527                 z += x;
 528                 x = 0;
 529                 lzeros = 0;
 530         }
 531         return val;
 532 }
 533 EXPORT_SYMBOL_GPL(mpi_read_raw_from_sgl);