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annotate pw.c @ 33:fa93d2ff9c62

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Prevent potential division by zero Add safeguard ensuring that there is at least one possible character to generate passwords from in order to exclude the possibility of a division by zero error in rand_uniform.
author Guido Berhoerster <guido+pwm@berhoerster.name>
date Tue, 30 Jul 2019 20:38:08 +0200
parents 8768fbd09bc5
children
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1 /*
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2 * Copyright (C) 2017 Guido Berhoerster <guido+pwm@berhoerster.name>
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3 *
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4 * Permission is hereby granted, free of charge, to any person obtaining
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5 * a copy of this software and associated documentation files (the
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6 * "Software"), to deal in the Software without restriction, including
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7 * without limitation the rights to use, copy, modify, merge, publish,
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8 * distribute, sublicense, and/or sell copies of the Software, and to
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9 * permit persons to whom the Software is furnished to do so, subject to
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10 * the following conditions:
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11 *
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12 * The above copyright notice and this permission notice shall be included
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13 * in all copies or substantial portions of the Software.
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14 *
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15 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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16 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
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17 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
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18 * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
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19 * CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
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20 * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
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21 * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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22 */
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23
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24 #include "compat.h"
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25
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26 #ifdef HAVE_ERR_H
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27 #include <err.h>
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28 #endif /* HAVE_ERR_H */
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29 #include <pws.h>
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30 #include <stdint.h>
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31 #include <string.h>
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32
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33 #include "pw.h"
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34 #include "rand.h"
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35 #include "util.h"
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36
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37 int
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38 pw_genrandom(struct pw_char_group groups[], size_t groups_len, char *password,
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39 size_t password_len)
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40 {
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41 int retval = -1;
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42 char *password_buf = NULL;
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43 size_t *group_matches = NULL;
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44 size_t i;
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45 size_t chars_len = 0;
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46 char *chars;
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47 size_t j;
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48 uint32_t r;
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49 size_t k;
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50
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51 password_buf = xmalloc(password_len + 1);
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52 password_buf[password_len] = '\0';
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53
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54 group_matches = xmalloc(groups_len * sizeof (size_t));
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55
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56 for (i = 0; i < groups_len; i++) {
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57 chars_len += strlen(groups[i].chars);
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58 }
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59 if (chars_len == 0) {
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60 /* there must be at least one character to choose from */
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61 return (-1);
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62 }
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63
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64 chars = xmalloc(chars_len + 1);
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65 chars[0] = '\0';
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66 for (i = 0; i < groups_len; i++) {
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67 strcat(chars, groups[i].chars);
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68 }
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69
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70 for (k = 0; k < 100000; k++) {
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71 memset(group_matches, 0, groups_len * sizeof (size_t));
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72
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73 for (j = 0; j < password_len; j++) {
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74 r = rand_uniform(chars_len);
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75 password_buf[j] = chars[r];
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76
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77 for (i = 0; i < groups_len; i++) {
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78 if (strchr(groups[i].chars, chars[r]) != NULL) {
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79 group_matches[i]++;
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80 break;
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81 }
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82 }
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83 }
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84
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85 for (i = 0; i < groups_len; i++) {
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86 if (group_matches[i] < groups[i].chars_min) {
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87 /* try again */
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88 break;
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89 }
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90 }
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91 if (i == groups_len) {
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92 /* password meets all constraints */
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93 strcpy(password, password_buf);
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94 retval = 0;
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95 break;
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96 }
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97 }
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98
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99 free(chars);
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100 free(group_matches);
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101 free(password_buf);
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102
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103 return (retval);
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104 }