1/*	$NetBSD: random_password.c,v 1.3 2019/12/15 22:50:46 christos Exp $	*/
2
3/*
4 * Copyright (c) 1998, 1999 Kungliga Tekniska H��gskolan
5 * (Royal Institute of Technology, Stockholm, Sweden).
6 * All rights reserved.
7 *
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
10 * are met:
11 *
12 * 1. Redistributions of source code must retain the above copyright
13 *    notice, this list of conditions and the following disclaimer.
14 *
15 * 2. Redistributions in binary form must reproduce the above copyright
16 *    notice, this list of conditions and the following disclaimer in the
17 *    documentation and/or other materials provided with the distribution.
18 *
19 * 3. Neither the name of the Institute nor the names of its contributors
20 *    may be used to endorse or promote products derived from this software
21 *    without specific prior written permission.
22 *
23 * THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
24 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
25 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
26 * ARE DISCLAIMED.  IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
27 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
28 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
29 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
30 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
31 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
32 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
33 * SUCH DAMAGE.
34 */
35
36#include "kadmin_locl.h"
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	OtpKey newkey;
61
62	krb5_generate_random_block(&newkey, sizeof(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    len = strlen(pass);
74    memset_s(pass, len, 0, len);
75    free(pass);
76#endif
77}
78
79/* some helper functions */
80
81#ifndef OTP_STYLE
82/* return a random value in range 0-127 */
83static int
84RND(unsigned char *key, int keylen, int *left)
85{
86    if(*left == 0){
87	krb5_generate_random_block(key, keylen);
88	*left = keylen;
89    }
90    (*left)--;
91    return ((unsigned char*)key)[*left];
92}
93
94/* This a helper function that generates a random password with a
95   number of characters from a set of character classes.
96
97   If there are n classes, and the size of each class is Pi, and the
98   number of characters from each class is Ni, the number of possible
99   passwords are (given that the character classes are disjoint):
100
101     n             n
102   -----        /  ----  \
103   |   |  Ni    |  \     |
104   |   | Pi     |   \  Ni| !
105   |   | ---- * |   /    |
106   |   | Ni!    |  /___  |
107    i=1          \  i=1  /
108
109    Since it uses the RND function above, neither the size of each
110    class, nor the total length of the generated password should be
111    larger than 127 (without fixing RND).
112
113   */
114static void
115generate_password(char **pw, int num_classes, ...)
116{
117    struct {
118	const char *str;
119	int len;
120	int freq;
121    } *classes;
122    va_list ap;
123    int len, i;
124    unsigned char rbuf[8]; /* random buffer */
125    int rleft = 0;
126
127    *pw = NULL;
128
129    classes = malloc(num_classes * sizeof(*classes));
130    if(classes == NULL)
131	return;
132    va_start(ap, num_classes);
133    len = 0;
134    for(i = 0; i < num_classes; i++){
135	classes[i].str = va_arg(ap, const char*);
136	classes[i].len = strlen(classes[i].str);
137	classes[i].freq = va_arg(ap, int);
138	len += classes[i].freq;
139    }
140    va_end(ap);
141    *pw = malloc(len + 1);
142    if(*pw == NULL) {
143	free(classes);
144	return;
145    }
146    for(i = 0; i < len; i++) {
147	int j;
148	int x = RND(rbuf, sizeof(rbuf), &rleft) % (len - i);
149	int t = 0;
150	for(j = 0; j < num_classes; j++) {
151	    if(x < t + classes[j].freq) {
152		(*pw)[i] = classes[j].str[RND(rbuf, sizeof(rbuf), &rleft)
153					 % classes[j].len];
154		classes[j].freq--;
155		break;
156	    }
157	    t += classes[j].freq;
158	}
159    }
160    (*pw)[len] = '\0';
161    memset_s(rbuf, sizeof(rbuf), 0, sizeof(rbuf));
162    free(classes);
163}
164#endif
165