lib/krb5/n-fold.c

   1 /*
   2  * Copyright (c) 1999 Kungliga Tekniska Högskolan
   3  * (Royal Institute of Technology, Stockholm, Sweden).
   4  * All rights reserved.
   5  *
   6  * Redistribution and use in source and binary forms, with or without
   7  * modification, are permitted provided that the following conditions
   8  * are met:
   9  *
  10  * 1. Redistributions of source code must retain the above copyright
  11  *    notice, this list of conditions and the following disclaimer.
  12  *
  13  * 2. Redistributions in binary form must reproduce the above copyright
  14  *    notice, this list of conditions and the following disclaimer in the
  15  *    documentation and/or other materials provided with the distribution.
  16  *
  17  * 3. Neither the name of KTH nor the names of its contributors may be
  18  *    used to endorse or promote products derived from this software without
  19  *    specific prior written permission.
  20  *
  21  * THIS SOFTWARE IS PROVIDED BY KTH AND ITS CONTRIBUTORS ``AS IS'' AND ANY
  22  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  23  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  24  * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL KTH OR ITS CONTRIBUTORS BE
  25  * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
  26  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
  27  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
  28  * BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
  29  * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
  30  * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
  31  * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. */
  32
  33 #include "krb5_locl.h"
  34
  35 static void
  36 rr13(uint8_t *dst1, uint8_t *dst2, uint8_t *src, size_t len)
  37 {
  38     int bytes = (len + 7) / 8;
  39     int i;
  40     const int bits = 13 % len;
  41
  42     for (i = 0; i < bytes; i++) {
  43         int bb;
  44         int b1, s1, b2, s2;
  45         /* calculate first bit position of this byte */
  46         bb = 8 * i - bits;
  47         while(bb < 0)
  48             bb += len;
  49         /* byte offset and shift count */
  50         b1 = bb / 8;
  51         s1 = bb % 8;
  52
  53         if (bb + 8 > bytes * 8)
  54             /* watch for wraparound */
  55             s2 = (len + 8 - s1) % 8;
  56         else
  57             s2 = 8 - s1;
  58         b2 = (b1 + 1) % bytes;
  59         dst1[i] = (src[b1] << s1) | (src[b2] >> s2);
  60         dst2[i] = dst1[i];
  61     }
  62
  63     return;
  64 }
  65
  66 /* Add `b' to `a', both being one's complement numbers. */
  67 static void
  68 add1(uint8_t *a, uint8_t *b, size_t len)
  69 {
  70     int i;
  71     int carry = 0;
  72     for(i = len - 1; i >= 0; i--){
  73         int x = a[i] + b[i] + carry;
  74         carry = x > 0xff;
  75         a[i] = x & 0xff;
  76     }
  77     for(i = len - 1; carry && i >= 0; i--){
  78         int x = a[i] + carry;
  79         carry = x > 0xff;
  80         a[i] = x & 0xff;
  81     }
  82 }
  83
  84 KRB5_LIB_FUNCTION krb5_error_code KRB5_LIB_CALL
  85 _krb5_n_fold(const void *str, size_t len, void *key, size_t size)
  86 {
  87     /* if len < size we need at most N * len bytes, ie < 2 * size;
  88        if len > size we need at most 2 * len */
  89     krb5_error_code ret = 0;
  90     size_t maxlen = 2 * max(size, len);
  91     size_t l = 0;
  92     uint8_t *tmp = malloc(maxlen + 2 * len);
  93     uint8_t *tmpbuf;
  94     uint8_t *buf1 = tmp + maxlen;
  95     uint8_t *buf2 = tmp + maxlen + len;
  96
  97     if (tmp == NULL) {
  98         ret = ENOMEM;
  99         goto out;
 100     }
 101
 102     memset(key, 0, size);
 103     memcpy(buf1, str, len);
 104     memcpy(tmp, buf1, len);
 105     do {
 106         l += len;
 107         while(l >= size) {
 108             add1(key, tmp, size);
 109             l -= size;
 110             if(l == 0)
 111                 break;
 112             memmove(tmp, tmp + size, l);
 113         }
 114         rr13(tmp + l, buf2, buf1, len * 8);
 115         tmpbuf = buf1;
 116         buf1 = buf2;
 117         buf2 = tmpbuf;
 118     } while(l != 0);
 119 out:
 120     if (tmp) {
 121         memset(tmp, 0, maxlen + 2 * len);
 122         free(tmp);
 123     }
 124     return ret;
 125 }