random_password.c revision 55682 
1/*
2 * Copyright (c) 1998, 1999 Kungliga Tekniska H�gskolan
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 the Institute nor the names of its contributors
18 *    may be used to endorse or promote products derived from this software
19 *    without specific prior written permission.
20 *
21 * THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
22 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
23 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
24 * ARE DISCLAIMED.  IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
25 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
26 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
27 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
28 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
29 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
30 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
31 * SUCH DAMAGE.
32 */
33
34#include "kadmin_locl.h"
35
36RCSID("$Id: random_password.c,v 1.3 1999/12/02 17:04:58 joda Exp $");
37
38/* This file defines some a function that generates a random password,
39   that can be used when creating a large amount of principals (such
40   as for a batch of students). Since this is a political matter, you
41   should think about how secure generated passwords has to be.
42
43   Both methods defined here will give you at least 55 bits of
44   entropy.
45   */
46
47/* If you want OTP-style passwords, define OTP_STYLE */
48
49#ifdef OTP_STYLE
50#include <otp.h>
51#else
52static void generate_password(char **pw, int num_classes, ...);
53#endif
54
55void
56random_password(char *pw, size_t len)
57{
58#ifdef OTP_STYLE
59    {
60	des_cblock newkey;
61
62	des_new_random_key(&newkey);
63	otp_print_stddict (newkey, pw, len);
64	strlwr(pw);
65    }
66#else
67    char *pass;
68    generate_password(&pass, 3,
69		      "abcdefghijklmnopqrstuvwxyz", 7,
70		      "ABCDEFGHIJKLMNOPQRSTUVWXYZ", 2,
71		      "@$%&*()-+=:,/<>1234567890", 1);
72    strlcpy(pw, pass, len);
73    memset(pass, 0, strlen(pass));
74    free(pass);
75#endif
76}
77
78/* some helper functions */
79
80#ifndef OTP_STYLE
81/* return a random value in range 0-127 */
82static int
83RND(des_cblock *key, int *left)
84{
85    if(*left == 0){
86	des_new_random_key(key);
87	*left = 8;
88    }
89    (*left)--;
90    return ((unsigned char*)key)[*left];
91}
92
93/* This a helper function that generates a random password with a
94   number of characters from a set of character classes.
95
96   If there are n classes, and the size of each class is Pi, and the
97   number of characters from each class is Ni, the number of possible
98   passwords are (given that the character classes are disjoint):
99
100     n             n
101   -----        /  ----  \
102   |   |  Ni    |  \     |
103   |   | Pi     |   \  Ni| !
104   |   | ---- * |   /    |
105   |   | Ni!    |  /___  |
106    i=1          \  i=1  /
107
108    Since it uses the RND function above, neither the size of each
109    class, nor the total length of the generated password should be
110    larger than 127 (without fixing RND).
111
112   */
113static void
114generate_password(char **pw, int num_classes, ...)
115{
116    struct {
117	const char *str;
118	int len;
119	int freq;
120    } *classes;
121    va_list ap;
122    int len, i;
123    des_cblock rbuf; /* random buffer */
124    int rleft = 0;
125
126    classes = malloc(num_classes * sizeof(*classes));
127    va_start(ap, num_classes);
128    len = 0;
129    for(i = 0; i < num_classes; i++){
130	classes[i].str = va_arg(ap, const char*);
131	classes[i].len = strlen(classes[i].str);
132	classes[i].freq = va_arg(ap, int);
133	len += classes[i].freq;
134    }
135    va_end(ap);
136    *pw = malloc(len + 1);
137    if(*pw == NULL)
138	return;
139    for(i = 0; i < len; i++) {
140	int j;
141	int x = RND(&rbuf, &rleft) % (len - i);
142	int t = 0;
143	for(j = 0; j < num_classes; j++) {
144	    if(x < t + classes[j].freq) {
145		(*pw)[i] = classes[j].str[RND(&rbuf, &rleft) % classes[j].len];
146		classes[j].freq--;
147		break;
148	    }
149	    t += classes[j].freq;
150	}
151    }
152    (*pw)[len] = '\0';
153    memset(rbuf, 0, sizeof(rbuf));
154    free(classes);
155}
156#endif
157