/*

 * Copyright (c) 1999 Kungliga Tekniska Högskolan

 * (Royal Institute of Technology, Stockholm, Sweden).

 * All rights reserved.

 *

 * Redistribution and use in source and binary forms, with or without

 * modification, are permitted provided that the following conditions

 * are met:

 *

 * 1. Redistributions of source code must retain the above copyright

 *    notice, this list of conditions and the following disclaimer.

 *

 * 2. Redistributions in binary form must reproduce the above copyright

 *    notice, this list of conditions and the following disclaimer in the

 *    documentation and/or other materials provided with the distribution.

 *

 * 3. Neither the name of KTH nor the names of its contributors may be

 *    used to endorse or promote products derived from this software without

 *    specific prior written permission.

 *

 * THIS SOFTWARE IS PROVIDED BY KTH AND ITS CONTRIBUTORS ``AS IS'' AND ANY

 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE

 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR

 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL KTH OR ITS CONTRIBUTORS BE

 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR

 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF

 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR

 * BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,

 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR

 * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF

 * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. */

#include "krb5_locl.h"

static void

rr13(uint8_t *dst1, uint8_t *dst2, uint8_t *src, size_t len)

{

    int bytes = (len + 7) / 8;

    int i;

    const int bits = 13 % len;

    for (i = 0; i < bytes; i++) {

  int bb;

  int b1, s1, b2, s2;

  /* calculate first bit position of this byte */

  bb = 8 * i - bits;

  while(bb < 0)

      bb += len;

  /* byte offset and shift count */

  b1 = bb / 8;

  s1 = bb % 8;

  if (bb + 8 > bytes * 8)

      /* watch for wraparound */

      s2 = (len + 8 - s1) % 8;

  else

      s2 = 8 - s1;

  b2 = (b1 + 1) % bytes;

  dst1[i] = (src[b1] << s1) | (src[b2] >> s2);

  dst2[i] = dst1[i];

    }

    return;

}

/*

 * Add `b' to `a', both being one's complement numbers.

 * This function assumes that inputs *a, *b are aligned

 * to 4 bytes.

 */

static void

add1(uint8_t *a, uint8_t *b, size_t len)

{

    int i;

    int carry = 0;

    uint32_t x;

    uint32_t left, right;

    for (i = len - 1; (i+1) % 4; i--) {

  x = a[i] + b[i] + carry;

  carry = x > 0xff;

  a[i] = x & 0xff;

    }

    for (i = len / 4 - 1; i >= 0; i--) {

  left = ntohl(((uint32_t *)a)[i]);

  right = ntohl(((uint32_t *)b)[i]);

  x = left + right + carry;

  carry = x < left || x < right;

  ((uint32_t *)a)[i]  = x;

    }

    for (i = len - 1; (i+1) % 4; i--) {

  x = a[i] + carry;

  carry = x > 0xff;

  a[i] = x & 0xff;

    }

    for (i = len / 4 - 1; carry && i >= 0; i--) {

        left = ((uint32_t *)a)[i];

        x = left + carry;

        carry = x < left;

        ((uint32_t *)a)[i] = x;

    }

    for (i = len / 4 - 1; i >=0; i--)

        ((uint32_t *)a)[i] = htonl(((uint32_t *)a)[i]);

}

KRB5_LIB_FUNCTION krb5_error_code KRB5_LIB_CALL

_krb5_n_fold(const void *str, size_t len, void *key, size_t size)

{

    /* if len < size we need at most N * len bytes, ie < 2 * size;

       if len > size we need at most 2 * len */

    size_t maxlen = 2 * max(size, len);

    size_t l = 0;

    uint8_t *tmp;

    uint8_t *tmpbuf;

    uint8_t *buf1;

    uint8_t *buf2;

    tmp = malloc(maxlen + 2 * len);

    if (tmp == NULL)

        return ENOMEM;

    buf1 = tmp + maxlen;

    buf2 = tmp + maxlen + len;

    memset(key, 0, size);

    memcpy(buf1, str, len);

    memcpy(tmp, buf1, len);

    do {

  l += len;

  while(l >= size) {

      add1(key, tmp, size);

      l -= size;

      if(l == 0)

    break;

      memmove(tmp, tmp + size, l);

  }

  rr13(tmp + l, buf2, buf1, len * 8);

  tmpbuf = buf1;

  buf1 = buf2;

  buf2 = tmpbuf;

    } while(l != 0);

    memset(tmp, 0, maxlen + 2 * len);

    free(tmp);

    return 0;

}