text: /*
   * 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 krb5_error_code
  rr13(unsigned char *buf, size_t len)
  {
      unsigned char *tmp;
      int bytes = (len + 7) / 8;
      int i;
      if(len == 0)
  	return 0;
      {
  	const int bits = 13 % len;
  	const int lbit = len % 8;
  
  	tmp = malloc(bytes);
  	if (tmp == NULL)
  	    return ENOMEM;
  	memcpy(tmp, buf, bytes);
  	if(lbit) {
  	    /* pad final byte with inital bits */
  	    tmp[bytes - 1] &= 0xff << (8 - lbit);
  	    for(i = lbit; i < 8; i += len)
  		tmp[bytes - 1] |= buf[0] >> i;
  	}
  	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;
  	    buf[i] = (tmp[b1] << s1) | (tmp[b2] >> s2);
  	}
  	free(tmp);
      }
      return 0;
  }
  
  /* Add `b' to `a', both being one's complement numbers. */
  static void
  add1(unsigned char *a, unsigned char *b, size_t len)
  {
      int i;
      int carry = 0;
      for(i = len - 1; i >= 0; i--){
  	int x = a[i] + b[i] + carry;
  	carry = x > 0xff;
  	a[i] = x & 0xff;
      }
      for(i = len - 1; carry && i >= 0; i--){
  	int x = a[i] + carry;
  	carry = x > 0xff;
  	a[i] = x & 0xff;
      }
  }
  
  krb5_error_code KRB5_LIB_FUNCTION
  _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 */
      krb5_error_code ret = 0;
      size_t maxlen = 2 * max(size, len);
      size_t l = 0;
      unsigned char *tmp = malloc(maxlen);
      unsigned char *buf = malloc(len);
  
      if (tmp == NULL || buf == NULL) {
          ret = ENOMEM;
  	goto out;
      }
  
      memcpy(buf, str, len);
      memset(key, 0, size);
      do {
  	memcpy(tmp + l, buf, len);
  	l += len;
  	ret = rr13(buf, len * 8);
  	if (ret)
  	    goto out;
  	while(l >= size) {
  	    add1(key, tmp, size);
  	    l -= size;
  	    if(l == 0)
  		break;
  	    memmove(tmp, tmp + size, l);
  	}
      } while(l != 0);
  out:
      if (buf) {
          memset(buf, 0, len);
  	free(buf);
      }
      if (tmp) {
          memset(tmp, 0, maxlen);
  	free(tmp);
      }
      return ret;
  }
  