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, unsigned 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, unsigned num_classes, ...)
113{
114    struct {
115	const char *str;
116	size_t len;
117	int freq;
118    } *classes;
119    va_list ap;
120    size_t len;
121    unsigned i;
122    unsigned char rbuf[8]; /* random buffer */
123    int rleft = 0;
124
125    *pw = NULL;
126
127    classes = malloc(num_classes * sizeof(*classes));
128    if(classes == NULL)
129	return;
130    va_start(ap, num_classes);
131    len = 0;
132    for(i = 0; i < num_classes; i++){
133	classes[i].str = va_arg(ap, const char*);
134	classes[i].len = strlen(classes[i].str);
135	classes[i].freq = va_arg(ap, int);
136	len += classes[i].freq;
137    }
138    va_end(ap);
139    *pw = malloc(len + 1);
140    if(*pw == NULL) {
141	free(classes);
142	return;
143    }
144    for(i = 0; i < len; i++) {
145	unsigned j;
146	int x = RND(rbuf, sizeof(rbuf), &rleft) % (len - i);
147	int t = 0;
148	for(j = 0; j < num_classes; j++) {
149	    if(x < t + classes[j].freq) {
150		(*pw)[i] = classes[j].str[RND(rbuf, sizeof(rbuf), &rleft)
151					 % classes[j].len];
152		classes[j].freq--;
153		break;
154	    }
155	    t += classes[j].freq;
156	}
157    }
158    (*pw)[len] = '\0';
159    memset(rbuf, 0, sizeof(rbuf));
160    free(classes);
161}
162#endif
163