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 krb5_error_code
  36 rr13(unsigned char *buf, size_t len)
  37 {
  38     unsigned char *tmp;
  39     int bytes = (len + 7) / 8;
  40     int i;
  41     if(len == 0)
  42         return 0;
  43     {
  44         const int bits = 13 % len;
  45         const int lbit = len % 8;
  46
  47         tmp = malloc(bytes);
  48         if (tmp == NULL)
  49             return ENOMEM;
  50         memcpy(tmp, buf, bytes);
  51         if(lbit) {
  52             /* pad final byte with inital bits */
  53             tmp[bytes - 1] &= 0xff << (8 - lbit);
  54             for(i = lbit; i < 8; i += len)
  55                 tmp[bytes - 1] |= buf[0] >> i;
  56         }
  57         for(i = 0; i < bytes; i++) {
  58             int bb;
  59             int b1, s1, b2, s2;
  60             /* calculate first bit position of this byte */
  61             bb = 8 * i - bits;
  62             while(bb < 0)
  63                 bb += len;
  64             /* byte offset and shift count */
  65             b1 = bb / 8;
  66             s1 = bb % 8;
  67
  68             if(bb + 8 > bytes * 8)
  69                 /* watch for wraparound */
  70                 s2 = (len + 8 - s1) % 8;
  71             else
  72                 s2 = 8 - s1;
  73             b2 = (b1 + 1) % bytes;
  74             buf[i] = (tmp[b1] << s1) | (tmp[b2] >> s2);
  75         }
  76         free(tmp);
  77     }
  78     return 0;
  79 }
  80
  81 /* Add `b' to `a', both being one's complement numbers. */
  82 static void
  83 add1(unsigned char *a, unsigned char *b, size_t len)
  84 {
  85     int i;
  86     int carry = 0;
  87     for(i = len - 1; i >= 0; i--){
  88         int x = a[i] + b[i] + carry;
  89         carry = x > 0xff;
  90         a[i] = x & 0xff;
  91     }
  92     for(i = len - 1; carry && i >= 0; i--){
  93         int x = a[i] + carry;
  94         carry = x > 0xff;
  95         a[i] = x & 0xff;
  96     }
  97 }
  98
  99 KRB5_LIB_FUNCTION krb5_error_code KRB5_LIB_CALL
 100 _krb5_n_fold(const void *str, size_t len, void *key, size_t size)
 101 {
 102     /* if len < size we need at most N * len bytes, ie < 2 * size;
 103        if len > size we need at most 2 * len */
 104     krb5_error_code ret = 0;
 105     size_t maxlen = 2 * max(size, len);
 106     size_t l = 0;
 107     unsigned char *tmp = malloc(maxlen);
 108     unsigned char *buf = malloc(len);
 109
 110     if (tmp == NULL || buf == NULL) {
 111         ret = ENOMEM;
 112         goto out;
 113     }
 114
 115     memcpy(buf, str, len);
 116     memset(key, 0, size);
 117     do {
 118         memcpy(tmp + l, buf, len);
 119         l += len;
 120         ret = rr13(buf, len * 8);
 121         if (ret)
 122             goto out;
 123         while(l >= size) {
 124             add1(key, tmp, size);
 125             l -= size;
 126             if(l == 0)
 127                 break;
 128             memmove(tmp, tmp + size, l);
 129         }
 130     } while(l != 0);
 131 out:
 132     if (buf) {
 133         memset(buf, 0, len);
 134         free(buf);
 135     }
 136     if (tmp) {
 137         memset(tmp, 0, maxlen);
 138         free(tmp);
 139     }
 140     return ret;
 141 }