crypto/dist/heimdal/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("$Heimdal: random_password.c 21745 2007-07-31 16:11:25Z lha $"
  37         "$NetBSD$");
  38
  39 /* This file defines some a function that generates a random password,
  40    that can be used when creating a large amount of principals (such
  41    as for a batch of students). Since this is a political matter, you
  42    should think about how secure generated passwords has to be.
  43
  44    Both methods defined here will give you at least 55 bits of
  45    entropy.
  46    */
  47
  48 /* If you want OTP-style passwords, define OTP_STYLE */
  49
  50 #ifdef OTP_STYLE
  51 #include <otp.h>
  52 #else
  53 static void generate_password(char **pw, int num_classes, ...);
  54 #endif
  55
  56 void
  57 random_password(char *pw, size_t len)
  58 {
  59 #ifdef OTP_STYLE
  60     {
  61         OtpKey newkey;
  62
  63         krb5_generate_random_block(&newkey, sizeof(newkey));
  64         otp_print_stddict (newkey, pw, len);
  65         strlwr(pw);
  66     }
  67 #else
  68     char *pass;
  69     generate_password(&pass, 3,
  70                       "abcdefghijklmnopqrstuvwxyz", 7,
  71                       "ABCDEFGHIJKLMNOPQRSTUVWXYZ", 2,
  72                       "@$%&*()-+=:,/<>1234567890", 1);
  73     strlcpy(pw, pass, len);
  74     memset(pass, 0, strlen(pass));
  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(rbuf, 0, sizeof(rbuf));
 162     free(classes);
 163 }
 164 #endif