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 /* 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
  50 static void generate_password(char **pw, int num_classes, ...);
  51 #endif
  52
  53 void
  54 random_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 */
  80 static int
  81 RND(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    */
 111 static void
 112 generate_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