kadmin/random_password.c

   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 RCSID("$Id$");
  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     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 */
  82 static int
  83 RND(unsigned char *key, int keylen, int *left)
  84 {
  85     if(*left == 0){
  86         krb5_generate_random_block(key, keylen);
  87         *left = keylen;
  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    */
 113 static void
 114 generate_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     unsigned char rbuf[8]; /* random buffer */
 124     int rleft = 0;
 125
 126     *pw = NULL;
 127
 128     classes = malloc(num_classes * sizeof(*classes));
 129     if(classes == NULL)
 130         return;
 131     va_start(ap, num_classes);
 132     len = 0;
 133     for(i = 0; i < num_classes; i++){
 134         classes[i].str = va_arg(ap, const char*);
 135         classes[i].len = strlen(classes[i].str);
 136         classes[i].freq = va_arg(ap, int);
 137         len += classes[i].freq;
 138     }
 139     va_end(ap);
 140     *pw = malloc(len + 1);
 141     if(*pw == NULL) {
 142         free(classes);
 143         return;
 144     }
 145     for(i = 0; i < len; i++) {
 146         int j;
 147         int x = RND(rbuf, sizeof(rbuf), &rleft) % (len - i);
 148         int t = 0;
 149         for(j = 0; j < num_classes; j++) {
 150             if(x < t + classes[j].freq) {
 151                 (*pw)[i] = classes[j].str[RND(rbuf, sizeof(rbuf), &rleft)
 152                                          % classes[j].len];
 153                 classes[j].freq--;
 154                 break;
 155             }
 156             t += classes[j].freq;
 157         }
 158     }
 159     (*pw)[len] = '\0';
 160     memset(rbuf, 0, sizeof(rbuf));
 161     free(classes);
 162 }
 163 #endif