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 tarball for details.
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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 <ctype.h>
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43 | #include <unistd.h>
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44 | #include <string.h>
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45 | #include <strings.h>
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46 |
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47 | #include "libbb.h"
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48 |
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49 |
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50 | /* passwords should consist of 6 (to 8 characters) */
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51 | #define MINLEN 6
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52 |
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53 |
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54 | static int string_checker_helper(const char *p1, const char *p2) __attribute__ ((__pure__));
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55 |
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56 | static int string_checker_helper(const char *p1, const char *p2)
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57 | {
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58 | /* as-is or capitalized */
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59 | if (strcasecmp(p1, p2) == 0
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60 | /* as sub-string */
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61 | || strcasestr(p2, p1) != NULL
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62 | /* invert in case haystack is shorter than needle */
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63 | || strcasestr(p1, p2) != NULL)
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64 | return 1;
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65 | return 0;
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66 | }
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67 |
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68 | static int string_checker(const char *p1, const char *p2)
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69 | {
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70 | int size;
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71 | /* check string */
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72 | int ret = string_checker_helper(p1, p2);
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73 | /* Make our own copy */
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74 | char *p = bb_xstrdup(p1);
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75 | /* reverse string */
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76 | size = strlen(p);
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77 |
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78 | while (size--) {
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79 | *p = p1[size];
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80 | p++;
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81 | }
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82 | /* restore pointer */
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83 | p -= strlen(p1);
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84 | /* check reversed string */
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85 | ret |= string_checker_helper(p, p2);
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86 | /* clean up */
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87 | memset(p, 0, strlen(p1));
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88 | free(p);
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89 | return ret;
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90 | }
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91 |
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92 | #define LOWERCASE 1
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93 | #define UPPERCASE 2
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94 | #define NUMBERS 4
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95 | #define SPECIAL 8
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96 |
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97 | static const char *obscure_msg(const char *old_p, const char *new_p, const struct passwd *pw)
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98 | {
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99 | int i;
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100 | int c;
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101 | int length;
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102 | int mixed = 0;
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103 | /* Add 1 for each type of characters to the minlen of password */
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104 | int size = MINLEN + 8;
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105 | const char *p;
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106 | char hostname[255];
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107 |
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108 | /* size */
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109 | if (!new_p || (length = strlen(new_p)) < MINLEN)
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110 | return("too short");
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111 |
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112 | /* no username as-is, as sub-string, reversed, capitalized, doubled */
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113 | if (string_checker(new_p, pw->pw_name)) {
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114 | return "similar to username";
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115 | }
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116 | /* no gecos as-is, as sub-string, reversed, capitalized, doubled */
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117 | if (*pw->pw_gecos && string_checker(new_p, pw->pw_gecos)) {
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118 | return "similar to gecos";
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119 | }
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120 | /* hostname as-is, as sub-string, reversed, capitalized, doubled */
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121 | if (gethostname(hostname, 255) == 0) {
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122 | hostname[254] = '\0';
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123 | if (string_checker(new_p, hostname)) {
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124 | return "similar to hostname";
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125 | }
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126 | }
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127 |
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128 | /* Should / Must contain a mix of: */
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129 | for (i = 0; i < length; i++) {
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130 | if (islower(new_p[i])) { /* a-z */
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131 | mixed |= LOWERCASE;
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132 | } else if (isupper(new_p[i])) { /* A-Z */
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133 | mixed |= UPPERCASE;
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134 | } else if (isdigit(new_p[i])) { /* 0-9 */
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135 | mixed |= NUMBERS;
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136 | } else { /* special characters */
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137 | mixed |= SPECIAL;
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138 | }
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139 | /* More than 50% similar characters ? */
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140 | c = 0;
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141 | p = new_p;
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142 | while (1) {
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143 | if ((p = strchr(p, new_p[i])) == NULL) {
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144 | break;
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145 | }
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146 | c++;
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147 | if (!++p) {
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148 | break; /* move past the matched char if possible */
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149 | }
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150 | }
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151 |
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152 | if (c >= (length / 2)) {
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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 | for (i=0; i<4; i++)
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157 | if (mixed & (1<<i)) size -= 2;
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158 | if (length < size)
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159 | return "too weak";
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160 |
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161 | if (old_p && old_p[0] != '\0') {
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162 | /* check vs. old password */
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163 | if (string_checker(new_p, old_p)) {
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164 | return "similar to old password";
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165 | }
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166 | }
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167 | return NULL;
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168 | }
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169 |
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170 | int obscure(const char *old, const char *newval, const struct passwd *pwdp)
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171 | {
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172 | const char *msg;
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173 |
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174 | if ((msg = obscure_msg(old, newval, pwdp))) {
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175 | printf("Bad password: %s.\n", msg);
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176 | /* If user is root warn only */
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177 | return (getuid())? 1 : 0;
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178 | }
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179 | return 0;
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180 | }
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