kc3-lang/libtommath/bn_mp_pack.c

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• Hash : fe2f91a1
  Author :
  Date : 2019-10-09T20:22:11
  

  to_sbin/to_ubin/pack: don't write anything in case of buffer overflow

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• bn_mp_pack.c

• #include "tommath_private.h"
  #ifdef BN_MP_PACK_C
  /* LibTomMath, multiple-precision integer library -- Tom St Denis */
  /* SPDX-License-Identifier: Unlicense */
  
  /* based on gmp's mpz_export.
   * see http://gmplib.org/manual/Integer-Import-and-Export.html
   */
  mp_err mp_pack(void *rop, size_t maxcount, size_t *written, mp_order order, size_t size,
                 mp_endian endian, size_t nails, const mp_int *op)
  {
     mp_err err;
     size_t odd_nails, nail_bytes, i, j, count;
     unsigned char odd_nail_mask;
  
     mp_int t;
  
     count = mp_pack_count(op, nails, size);
  
     if (count > maxcount) {
        return MP_BUF;
     }
  
     if ((err = mp_init_copy(&t, op)) != MP_OKAY) {
        return err;
     }
  
     if (endian == MP_NATIVE_ENDIAN) {
        MP_GET_ENDIANNESS(endian);
     }
  
     odd_nails = (nails % 8u);
     odd_nail_mask = 0xff;
     for (i = 0u; i < odd_nails; ++i) {
        odd_nail_mask ^= (unsigned char)(1u << (7u - i));
     }
     nail_bytes = nails / 8u;
  
     for (i = 0u; i < count; ++i) {
        for (j = 0u; j < size; ++j) {
           unsigned char *byte = (unsigned char *)rop +
                                 (((order == MP_LSB_FIRST) ? i : ((count - 1u) - i)) * size) +
                                 ((endian == MP_LITTLE_ENDIAN) ? j : ((size - 1u) - j));
  
           if (j >= (size - nail_bytes)) {
              *byte = 0;
              continue;
           }
  
           *byte = (unsigned char)((j == ((size - nail_bytes) - 1u)) ? (t.dp[0] & odd_nail_mask) : (t.dp[0] & 0xFFuL));
  
           if ((err = mp_div_2d(&t, (j == ((size - nail_bytes) - 1u)) ? (int)(8u - odd_nails) : 8, &t, NULL)) != MP_OKAY) {
              goto LBL_ERR;
           }
  
        }
     }
  
     if (written != NULL) {
        *written = count;
     }
     err = MP_OKAY;
  
  LBL_ERR:
     mp_clear(&t);
     return err;
  }
  
  #endif
  

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