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
35static krb5_error_code
36rr13(unsigned char *buf, size_t len)
37{
38    unsigned char *tmp;
39    size_t bytes = (len + 7) / 8;
40    size_t 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	    ssize_t bb;
59	    ssize_t 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((size_t)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. */
82static void
83add1(unsigned char *a, unsigned char *b, size_t len)
84{
85    ssize_t 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
99KRB5_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);
131out:
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}
142