1 | /* vi: set sw=4 ts=4: */
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2 | /*
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3 | * Mini weak password checker implementation for busybox
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4 | *
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5 | * Copyright (C) 2006 Tito Ragusa <farmatito@tiscali.it>
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6 | *
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7 | * Licensed under GPLv2 or later, see file LICENSE in this source tree.
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8 | */
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9 |
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10 | /* A good password:
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11 | 1) should contain at least six characters (man passwd);
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12 | 2) empty passwords are not permitted;
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13 | 3) should contain a mix of four different types of characters
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14 | upper case letters,
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15 | lower case letters,
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16 | numbers,
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17 | special characters such as !@#$%^&*,;".
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18 | This password types should not be permitted:
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19 | a) pure numbers: birthdates, social security number, license plate, phone numbers;
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20 | b) words and all letters only passwords (uppercase, lowercase or mixed)
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21 | as palindromes, consecutive or repetitive letters
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22 | or adjacent letters on your keyboard;
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23 | c) username, real name, company name or (e-mail?) address
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24 | in any form (as-is, reversed, capitalized, doubled, etc.).
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25 | (we can check only against username, gecos and hostname)
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26 | d) common and obvious letter-number replacements
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27 | (e.g. replace the letter O with number 0)
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28 | such as "M1cr0$0ft" or "P@ssw0rd" (CAVEAT: we cannot check for them
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29 | without the use of a dictionary).
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30 |
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31 | For each missing type of characters an increase of password length is
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32 | requested.
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33 |
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34 | If user is root we warn only.
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35 |
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36 | CAVEAT: some older versions of crypt() truncates passwords to 8 chars,
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37 | so that aaaaaaaa1Q$ is equal to aaaaaaaa making it possible to fool
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38 | some of our checks. We don't test for this special case as newer versions
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39 | of crypt do not truncate passwords.
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40 | */
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41 |
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42 | #include "libbb.h"
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43 |
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44 | static int string_checker_helper(const char *p1, const char *p2) __attribute__ ((__pure__));
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45 |
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46 | static int string_checker_helper(const char *p1, const char *p2)
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47 | {
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48 | /* as sub-string */
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49 | if (strcasestr(p2, p1) != NULL
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50 | /* invert in case haystack is shorter than needle */
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51 | || strcasestr(p1, p2) != NULL
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52 | /* as-is or capitalized */
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53 | /* || strcasecmp(p1, p2) == 0 - 1st strcasestr should catch this too */
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54 | ) {
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55 | return 1;
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56 | }
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57 | return 0;
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58 | }
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59 |
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60 | static int string_checker(const char *p1, const char *p2)
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61 | {
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62 | int size, i;
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63 | /* check string */
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64 | int ret = string_checker_helper(p1, p2);
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65 | /* make our own copy */
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66 | char *p = xstrdup(p1);
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67 |
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68 | /* reverse string */
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69 | i = size = strlen(p1);
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70 | while (--i >= 0) {
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71 | *p++ = p1[i];
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72 | }
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73 | p -= size; /* restore pointer */
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74 |
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75 | /* check reversed string */
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76 | ret |= string_checker_helper(p, p2);
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77 |
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78 | /* clean up */
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79 | nuke_str(p);
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80 | free(p);
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81 |
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82 | return ret;
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83 | }
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84 |
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85 | #define CATEGORIES 4
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86 |
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87 | #define LOWERCASE 1
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88 | #define UPPERCASE 2
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89 | #define NUMBERS 4
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90 | #define SPECIAL 8
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91 |
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92 | #define LAST_CAT 8
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93 |
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94 | static const char *obscure_msg(const char *old_p, const char *new_p, const struct passwd *pw)
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95 | {
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96 | unsigned length;
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97 | unsigned size;
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98 | unsigned mixed;
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99 | unsigned c;
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100 | unsigned i;
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101 | const char *p;
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102 | char *hostname;
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103 |
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104 | /* size */
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105 | if (!new_p || (length = strlen(new_p)) < CONFIG_PASSWORD_MINLEN)
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106 | return "too short";
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107 |
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108 | /* no username as-is, as sub-string, reversed, capitalized, doubled */
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109 | if (string_checker(new_p, pw->pw_name)) {
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110 | return "similar to username";
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111 | }
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112 | #ifndef __BIONIC__
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113 | /* no gecos as-is, as sub-string, reversed, capitalized, doubled */
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114 | if (pw->pw_gecos[0] && string_checker(new_p, pw->pw_gecos)) {
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115 | return "similar to gecos";
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116 | }
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117 | #endif
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118 | /* hostname as-is, as sub-string, reversed, capitalized, doubled */
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119 | hostname = safe_gethostname();
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120 | i = string_checker(new_p, hostname);
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121 | free(hostname);
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122 | if (i)
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123 | return "similar to hostname";
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124 |
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125 | /* Should / Must contain a mix of: */
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126 | mixed = 0;
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127 | for (i = 0; i < length; i++) {
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128 | if (islower(new_p[i])) { /* a-z */
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129 | mixed |= LOWERCASE;
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130 | } else if (isupper(new_p[i])) { /* A-Z */
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131 | mixed |= UPPERCASE;
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132 | } else if (isdigit(new_p[i])) { /* 0-9 */
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133 | mixed |= NUMBERS;
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134 | } else { /* special characters */
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135 | mixed |= SPECIAL;
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136 | }
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137 | /* Count i'th char */
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138 | c = 0;
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139 | p = new_p;
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140 | while (1) {
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141 | p = strchr(p, new_p[i]);
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142 | if (p == NULL) {
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143 | break;
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144 | }
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145 | c++;
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146 | p++;
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147 | if (!*p) {
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148 | break;
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149 | }
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150 | }
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151 | /* More than 50% similar characters ? */
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152 | if (c*2 >= length) {
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153 | return "too many similar characters";
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154 | }
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155 | }
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156 |
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157 | size = CONFIG_PASSWORD_MINLEN + 2*CATEGORIES;
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158 | for (i = 1; i <= LAST_CAT; i <<= 1)
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159 | if (mixed & i)
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160 | size -= 2;
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161 | if (length < size)
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162 | return "too weak";
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163 |
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164 | if (old_p && old_p[0]) {
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165 | /* check vs. old password */
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166 | if (string_checker(new_p, old_p)) {
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167 | return "similar to old password";
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168 | }
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169 | }
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170 |
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171 | return NULL;
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172 | }
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173 |
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174 | int FAST_FUNC obscure(const char *old, const char *newval, const struct passwd *pw)
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175 | {
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176 | const char *msg;
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177 |
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178 | msg = obscure_msg(old, newval, pw);
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179 | if (msg) {
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180 | printf("Bad password: %s\n", msg);
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181 | return 1;
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182 | }
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183 | return 0;
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184 | }
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185 |
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186 | #if ENABLE_UNIT_TEST
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187 |
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188 | /* Test obscure_msg() instead of obscure() in order not to print anything. */
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189 |
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190 | static const struct passwd pw = {
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191 | .pw_name = (char *)"johndoe",
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192 | .pw_gecos = (char *)"John Doe",
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193 | };
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194 |
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195 | BBUNIT_DEFINE_TEST(obscure_weak_pass)
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196 | {
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197 | /* Empty password */
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198 | BBUNIT_ASSERT_NOTNULL(obscure_msg("Ad4#21?'S|", "", &pw));
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199 | /* Pure numbers */
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200 | BBUNIT_ASSERT_NOTNULL(obscure_msg("Ad4#21?'S|", "23577315", &pw));
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201 | /* Similar to pw_name */
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202 | BBUNIT_ASSERT_NOTNULL(obscure_msg("Ad4#21?'S|", "johndoe123%", &pw));
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203 | /* Similar to pw_gecos, reversed */
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204 | BBUNIT_ASSERT_NOTNULL(obscure_msg("Ad4#21?'S|", "eoD nhoJ^44@", &pw));
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205 | /* Similar to the old password */
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206 | BBUNIT_ASSERT_NOTNULL(obscure_msg("Ad4#21?'S|", "d4#21?'S", &pw));
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207 | /* adjacent letters */
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208 | BBUNIT_ASSERT_NOTNULL(obscure_msg("Ad4#21?'S|", "qwerty123", &pw));
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209 | /* Many similar chars */
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210 | BBUNIT_ASSERT_NOTNULL(obscure_msg("Ad4#21?'S|", "^33Daaaaaa1", &pw));
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211 |
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212 | BBUNIT_ENDTEST;
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213 | }
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214 |
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215 | BBUNIT_DEFINE_TEST(obscure_strong_pass)
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216 | {
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217 | BBUNIT_ASSERT_NULL(obscure_msg("Rt4##2&:'|", "}(^#rrSX3S*22", &pw));
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218 |
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219 | BBUNIT_ENDTEST;
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220 | }
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221 |
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222 | #endif /* ENABLE_UNIT_TEST */
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