1/* crypto/bn/bn_rand.c */
2/* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
3 * All rights reserved.
4 *
5 * This package is an SSL implementation written
6 * by Eric Young (eay@cryptsoft.com).
7 * The implementation was written so as to conform with Netscapes SSL.
8 *
9 * This library is free for commercial and non-commercial use as long as
10 * the following conditions are aheared to.  The following conditions
11 * apply to all code found in this distribution, be it the RC4, RSA,
12 * lhash, DES, etc., code; not just the SSL code.  The SSL documentation
13 * included with this distribution is covered by the same copyright terms
14 * except that the holder is Tim Hudson (tjh@cryptsoft.com).
15 *
16 * Copyright remains Eric Young's, and as such any Copyright notices in
17 * the code are not to be removed.
18 * If this package is used in a product, Eric Young should be given attribution
19 * as the author of the parts of the library used.
20 * This can be in the form of a textual message at program startup or
21 * in documentation (online or textual) provided with the package.
22 *
23 * Redistribution and use in source and binary forms, with or without
24 * modification, are permitted provided that the following conditions
25 * are met:
26 * 1. Redistributions of source code must retain the copyright
27 *    notice, this list of conditions and the following disclaimer.
28 * 2. Redistributions in binary form must reproduce the above copyright
29 *    notice, this list of conditions and the following disclaimer in the
30 *    documentation and/or other materials provided with the distribution.
31 * 3. All advertising materials mentioning features or use of this software
32 *    must display the following acknowledgement:
33 *    "This product includes cryptographic software written by
34 *     Eric Young (eay@cryptsoft.com)"
35 *    The word 'cryptographic' can be left out if the rouines from the library
36 *    being used are not cryptographic related :-).
37 * 4. If you include any Windows specific code (or a derivative thereof) from
38 *    the apps directory (application code) you must include an acknowledgement:
39 *    "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"
40 *
41 * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND
42 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
43 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
44 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
45 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
46 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
47 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
48 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
49 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
50 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
51 * SUCH DAMAGE.
52 *
53 * The licence and distribution terms for any publically available version or
54 * derivative of this code cannot be changed.  i.e. this code cannot simply be
55 * copied and put under another distribution licence
56 * [including the GNU Public Licence.]
57 */
58
59#include <stdio.h>
60#include <time.h>
61#include "cryptlib.h"
62#include "bn_lcl.h"
63#include <openssl/rand.h>
64
65static int bnrand(int pseudorand, BIGNUM *rnd, int bits, int top, int bottom)
66	{
67	unsigned char *buf=NULL;
68	int ret=0,bit,bytes,mask;
69	time_t tim;
70
71	if (bits == 0)
72		{
73		BN_zero(rnd);
74		return 1;
75		}
76
77	bytes=(bits+7)/8;
78	bit=(bits-1)%8;
79	mask=0xff<<(bit+1);
80
81	buf=(unsigned char *)Malloc(bytes);
82	if (buf == NULL)
83		{
84		BNerr(BN_F_BN_RAND,ERR_R_MALLOC_FAILURE);
85		goto err;
86		}
87
88	/* make a random number and set the top and bottom bits */
89	time(&tim);
90	RAND_add(&tim,sizeof(tim),0);
91
92	if (pseudorand)
93		{
94		if (RAND_pseudo_bytes(buf, bytes) == -1)
95			goto err;
96		}
97	else
98		{
99		if (RAND_bytes(buf, bytes) <= 0)
100			goto err;
101		}
102
103#if 1
104	if (pseudorand == 2)
105		{
106		/* generate patterns that are more likely to trigger BN
107		   library bugs */
108		int i;
109		unsigned char c;
110
111		for (i = 0; i < bytes; i++)
112			{
113			RAND_pseudo_bytes(&c, 1);
114			if (c >= 128 && i > 0)
115				buf[i] = buf[i-1];
116			else if (c < 42)
117				buf[i] = 0;
118			else if (c < 84)
119				buf[i] = 255;
120			}
121		}
122#endif
123
124	if (top != -1)
125		{
126		if (top)
127			{
128			if (bit == 0)
129				{
130				buf[0]=1;
131				buf[1]|=0x80;
132				}
133			else
134				{
135				buf[0]|=(3<<(bit-1));
136				}
137			}
138		else
139			{
140			buf[0]|=(1<<bit);
141			}
142		}
143	buf[0] &= ~mask;
144	if (bottom) /* set bottom bit if requested */
145		buf[bytes-1]|=1;
146	if (!BN_bin2bn(buf,bytes,rnd)) goto err;
147	ret=1;
148err:
149	if (buf != NULL)
150		{
151		memset(buf,0,bytes);
152		Free(buf);
153		}
154	return(ret);
155	}
156
157int     BN_rand(BIGNUM *rnd, int bits, int top, int bottom)
158	{
159	return bnrand(0, rnd, bits, top, bottom);
160	}
161
162int     BN_pseudo_rand(BIGNUM *rnd, int bits, int top, int bottom)
163	{
164	return bnrand(1, rnd, bits, top, bottom);
165	}
166
167#if 0
168int     BN_bntest_rand(BIGNUM *rnd, int bits, int top, int bottom)
169	{
170	return bnrand(2, rnd, bits, top, bottom);
171	}
172#endif
173
174/* random number r:  0 <= r < range */
175int	BN_rand_range(BIGNUM *r, BIGNUM *range)
176	{
177	int n;
178
179	if (range->neg || BN_is_zero(range))
180		{
181		BNerr(BN_F_BN_RAND_RANGE, BN_R_INVALID_RANGE);
182		return 0;
183		}
184
185	n = BN_num_bits(range); /* n > 0 */
186
187	if (n == 1)
188		{
189		if (!BN_zero(r)) return 0;
190		}
191	else if (BN_is_bit_set(range, n - 2))
192		{
193		do
194			{
195			/* range = 11..._2, so each iteration succeeds with probability >= .75 */
196			if (!BN_rand(r, n, -1, 0)) return 0;
197			}
198		while (BN_cmp(r, range) >= 0);
199		}
200	else
201		{
202		/* range = 10..._2,
203		 * so  3*range (= 11..._2)  is exactly one bit longer than  range */
204		do
205			{
206			if (!BN_rand(r, n + 1, -1, 0)) return 0;
207			/* If  r < 3*range,  use  r := r MOD range
208			 * (which is either  r, r - range,  or  r - 2*range).
209			 * Otherwise, iterate once more.
210			 * Since  3*range = 11..._2, each iteration succeeds with
211			 * probability >= .75. */
212			if (BN_cmp(r ,range) >= 0)
213				{
214				if (!BN_sub(r, r, range)) return 0;
215				if (BN_cmp(r, range) >= 0)
216					if (!BN_sub(r, r, range)) return 0;
217				}
218			}
219		while (BN_cmp(r, range) >= 0);
220		}
221
222	return 1;
223	}
224