1/*
2 * Copyright (c) 1998, 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 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
36/* This file defines some a function that generates a random password,
37   that can be used when creating a large amount of principals (such
38   as for a batch of students). Since this is a political matter, you
39   should think about how secure generated passwords has to be.
40
41   Both methods defined here will give you at least 55 bits of
42   entropy.
43   */
44
45/* If you want OTP-style passwords, define OTP_STYLE */
46
47#ifdef OTP_STYLE
48#include <otp.h>
49#else
50static void generate_password(char **pw, int num_classes, ...);
51#endif
52
53void
54random_password(char *pw, size_t len)
55{
56#ifdef OTP_STYLE
57    {
58	OtpKey newkey;
59
60	krb5_generate_random_block(&newkey, sizeof(newkey));
61	otp_print_stddict (newkey, pw, len);
62	strlwr(pw);
63    }
64#else
65    char *pass;
66    generate_password(&pass, 3,
67		      "abcdefghijklmnopqrstuvwxyz", 7,
68		      "ABCDEFGHIJKLMNOPQRSTUVWXYZ", 2,
69		      "@$%&*()-+=:,/<>1234567890", 1);
70    strlcpy(pw, pass, len);
71    memset(pass, 0, strlen(pass));
72    free(pass);
73#endif
74}
75
76/* some helper functions */
77
78#ifndef OTP_STYLE
79/* return a random value in range 0-127 */
80static int
81RND(unsigned char *key, int keylen, int *left)
82{
83    if(*left == 0){
84	krb5_generate_random_block(key, keylen);
85	*left = keylen;
86    }
87    (*left)--;
88    return ((unsigned char*)key)[*left];
89}
90
91/* This a helper function that generates a random password with a
92   number of characters from a set of character classes.
93
94   If there are n classes, and the size of each class is Pi, and the
95   number of characters from each class is Ni, the number of possible
96   passwords are (given that the character classes are disjoint):
97
98     n             n
99   -----        /  ----  \
100   |   |  Ni    |  \     |
101   |   | Pi     |   \  Ni| !
102   |   | ---- * |   /    |
103   |   | Ni!    |  /___  |
104    i=1          \  i=1  /
105
106    Since it uses the RND function above, neither the size of each
107    class, nor the total length of the generated password should be
108    larger than 127 (without fixing RND).
109
110   */
111static void
112generate_password(char **pw, int num_classes, ...)
113{
114    struct {
115	const char *str;
116	int len;
117	int freq;
118    } *classes;
119    va_list ap;
120    int len, i;
121    unsigned char rbuf[8]; /* random buffer */
122    int rleft = 0;
123
124    *pw = NULL;
125
126    classes = malloc(num_classes * sizeof(*classes));
127    if(classes == NULL)
128	return;
129    va_start(ap, num_classes);
130    len = 0;
131    for(i = 0; i < num_classes; i++){
132	classes[i].str = va_arg(ap, const char*);
133	classes[i].len = strlen(classes[i].str);
134	classes[i].freq = va_arg(ap, int);
135	len += classes[i].freq;
136    }
137    va_end(ap);
138    *pw = malloc(len + 1);
139    if(*pw == NULL) {
140	free(classes);
141	return;
142    }
143    for(i = 0; i < len; i++) {
144	int j;
145	int x = RND(rbuf, sizeof(rbuf), &rleft) % (len - i);
146	int t = 0;
147	for(j = 0; j < num_classes; j++) {
148	    if(x < t + classes[j].freq) {
149		(*pw)[i] = classes[j].str[RND(rbuf, sizeof(rbuf), &rleft)
150					 % classes[j].len];
151		classes[j].freq--;
152		break;
153	    }
154	    t += classes[j].freq;
155	}
156    }
157    (*pw)[len] = '\0';
158    memset(rbuf, 0, sizeof(rbuf));
159    free(classes);
160}
161#endif
162