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      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 Hgskolan
      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
     52 static void generate_password(char **pw, int num_classes, ...);
     53 #endif
     54 
     55 void
     56 random_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 */
     83 static int
     84 RND(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    */
    114 static void
    115 generate_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