1 /* 2 * Copyright (c) 1998, 1999 Kungliga Tekniska H�gskolan 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: random_password.c 21745 2007-07-31 16:11:25Z lha $"); 37 38 /* This file defines some a function that generates a random password, 39 that can be used when creating a large amount of principals (such 40 as for a batch of students). Since this is a political matter, you 41 should think about how secure generated passwords has to be. 42 43 Both methods defined here will give you at least 55 bits of 44 entropy. 45 */ 46 47 /* If you want OTP-style passwords, define OTP_STYLE */ 48 49 #ifdef OTP_STYLE 50 #include <otp.h> 51 #else 52 static void generate_password(char **pw, int num_classes, ...); 53 #endif 54 55 void 56 random_password(char *pw, size_t len) 57 { 58 #ifdef OTP_STYLE 59 { 60 OtpKey newkey; 61 62 krb5_generate_random_block(&newkey, sizeof(newkey)); 63 otp_print_stddict (newkey, pw, len); 64 strlwr(pw); 65 } 66 #else 67 char *pass; 68 generate_password(&pass, 3, 69 "abcdefghijklmnopqrstuvwxyz", 7, 70 "ABCDEFGHIJKLMNOPQRSTUVWXYZ", 2, 71 "@$%&*()-+=:,/<>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 164