1 | /* |
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2 | * nonlocal-passwd.c |
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3 | * passwd database for nss_nonlocal proxy. |
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4 | * |
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5 | * Copyright © 2007 Anders Kaseorg <andersk@mit.edu> and Tim Abbott |
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6 | * <tabbott@mit.edu> |
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7 | * |
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8 | * Permission is hereby granted, free of charge, to any person |
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9 | * obtaining a copy of this software and associated documentation |
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10 | * files (the "Software"), to deal in the Software without |
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11 | * restriction, including without limitation the rights to use, copy, |
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12 | * modify, merge, publish, distribute, sublicense, and/or sell copies |
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13 | * of the Software, and to permit persons to whom the Software is |
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14 | * furnished to do so, subject to the following conditions: |
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15 | * |
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16 | * The above copyright notice and this permission notice shall be |
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17 | * included in all copies or substantial portions of the Software. |
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18 | * |
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19 | * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, |
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20 | * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF |
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21 | * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND |
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22 | * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS |
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23 | * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN |
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24 | * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN |
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25 | * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE |
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26 | * SOFTWARE. |
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27 | */ |
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28 | |
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29 | |
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30 | #define _GNU_SOURCE |
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31 | #include <sys/types.h> |
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32 | #include <unistd.h> |
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33 | #include <stdlib.h> |
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34 | #include <stdint.h> |
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35 | #include <string.h> |
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36 | #include <dlfcn.h> |
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37 | #include <stdio.h> |
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38 | #include <syslog.h> |
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39 | #include <errno.h> |
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40 | #include <pwd.h> |
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41 | #include <grp.h> |
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42 | #include <nss.h> |
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43 | #include "nsswitch-internal.h" |
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44 | #include "nonlocal.h" |
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45 | |
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46 | #define MAGIC_LOCAL_PW_BUFLEN (sysconf(_SC_GETPW_R_SIZE_MAX) + 7) |
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47 | |
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48 | |
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49 | static service_user * |
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50 | nss_passwd_nonlocal_database(void) |
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51 | { |
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52 | static service_user *nip = NULL; |
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53 | if (nip == NULL) |
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54 | __nss_database_lookup("passwd_nonlocal", NULL, "", &nip); |
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55 | |
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56 | return nip; |
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57 | } |
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58 | |
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59 | |
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60 | enum nss_status |
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61 | check_nonlocal_uid(const char *user, uid_t uid, int *errnop) |
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62 | { |
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63 | enum nss_status status = NSS_STATUS_SUCCESS; |
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64 | struct passwd pwbuf; |
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65 | struct passwd *pwbufp = &pwbuf; |
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66 | int ret; |
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67 | int old_errno = errno; |
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68 | int buflen = MAGIC_LOCAL_PW_BUFLEN; |
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69 | char *buf = malloc(buflen); |
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70 | if (buf == NULL) { |
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71 | *errnop = ENOMEM; |
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72 | errno = old_errno; |
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73 | return NSS_STATUS_TRYAGAIN; |
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74 | } |
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75 | errno = 0; |
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76 | ret = getpwuid_r(uid, pwbufp, buf, buflen, &pwbufp); |
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77 | if (ret != 0) { |
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78 | *errnop = errno; |
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79 | status = NSS_STATUS_TRYAGAIN; |
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80 | } else if (pwbufp != NULL) { |
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81 | syslog(LOG_ERR, "nss_nonlocal: possible spoofing attack: non-local user %s has same UID as local user %s!\n", user, pwbuf.pw_name); |
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82 | status = NSS_STATUS_NOTFOUND; |
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83 | } |
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84 | free(buf); |
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85 | errno = old_errno; |
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86 | return status; |
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87 | } |
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88 | |
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89 | enum nss_status |
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90 | check_nonlocal_user(const char *user, int *errnop) |
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91 | { |
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92 | enum nss_status status = NSS_STATUS_SUCCESS; |
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93 | struct passwd pwbuf; |
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94 | struct passwd *pwbufp = &pwbuf; |
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95 | int ret; |
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96 | int old_errno = errno; |
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97 | int buflen = MAGIC_LOCAL_PW_BUFLEN; |
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98 | char *buf = malloc(buflen); |
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99 | if (buf == NULL) { |
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100 | *errnop = ENOMEM; |
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101 | errno = old_errno; |
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102 | return NSS_STATUS_TRYAGAIN; |
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103 | } |
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104 | errno = 0; |
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105 | ret = getpwnam_r(user, pwbufp, buf, buflen, &pwbufp); |
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106 | if (ret != 0) { |
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107 | *errnop = errno; |
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108 | status = NSS_STATUS_TRYAGAIN; |
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109 | } else if (pwbufp != NULL) { |
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110 | status = NSS_STATUS_NOTFOUND; |
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111 | } |
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112 | free(buf); |
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113 | errno = old_errno; |
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114 | return status; |
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115 | } |
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116 | |
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117 | |
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118 | static service_user *pwent_nip = NULL; |
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119 | static void *pwent_fct_start; |
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120 | static union { |
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121 | enum nss_status (*l)(struct passwd *pwd, char *buffer, size_t buflen, |
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122 | int *errnop); |
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123 | void *ptr; |
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124 | } pwent_fct; |
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125 | static const char *pwent_fct_name = "getpwent_r"; |
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126 | |
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127 | enum nss_status |
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128 | _nss_nonlocal_setpwent(int stayopen) |
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129 | { |
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130 | static const char *fct_name = "setpwent"; |
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131 | static void *fct_start = NULL; |
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132 | enum nss_status status; |
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133 | service_user *nip; |
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134 | union { |
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135 | enum nss_status (*l)(int stayopen); |
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136 | void *ptr; |
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137 | } fct; |
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138 | |
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139 | nip = nss_passwd_nonlocal_database(); |
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140 | if (nip == NULL) |
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141 | return NSS_STATUS_UNAVAIL; |
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142 | if (fct_start == NULL) |
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143 | fct_start = __nss_lookup_function(nip, fct_name); |
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144 | fct.ptr = fct_start; |
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145 | do { |
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146 | if (fct.ptr == NULL) |
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147 | status = NSS_STATUS_UNAVAIL; |
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148 | else |
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149 | status = DL_CALL_FCT(fct.l, (stayopen)); |
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150 | } while (__nss_next(&nip, fct_name, &fct.ptr, status, 0) == 0); |
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151 | if (status != NSS_STATUS_SUCCESS) |
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152 | return status; |
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153 | |
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154 | pwent_nip = nip; |
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155 | if (pwent_fct_start == NULL) |
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156 | pwent_fct_start = __nss_lookup_function(nip, pwent_fct_name); |
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157 | pwent_fct.ptr = pwent_fct_start; |
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158 | return NSS_STATUS_SUCCESS; |
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159 | } |
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160 | |
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161 | enum nss_status |
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162 | _nss_nonlocal_endpwent(void) |
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163 | { |
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164 | static const char *fct_name = "endpwent"; |
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165 | static void *fct_start = NULL; |
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166 | enum nss_status status; |
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167 | service_user *nip; |
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168 | union { |
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169 | enum nss_status (*l)(void); |
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170 | void *ptr; |
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171 | } fct; |
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172 | |
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173 | pwent_nip = NULL; |
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174 | |
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175 | nip = nss_passwd_nonlocal_database(); |
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176 | if (nip == NULL) |
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177 | return NSS_STATUS_UNAVAIL; |
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178 | if (fct_start == NULL) |
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179 | fct_start = __nss_lookup_function(nip, fct_name); |
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180 | fct.ptr = fct_start; |
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181 | do { |
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182 | if (fct.ptr == NULL) |
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183 | status = NSS_STATUS_UNAVAIL; |
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184 | else |
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185 | status = DL_CALL_FCT(fct.l, ()); |
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186 | } while (__nss_next(&nip, fct_name, &fct.ptr, status, 0) == 0); |
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187 | return status; |
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188 | } |
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189 | |
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190 | enum nss_status |
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191 | _nss_nonlocal_getpwent_r(struct passwd *pwd, char *buffer, size_t buflen, |
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192 | int *errnop) |
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193 | { |
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194 | enum nss_status status; |
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195 | |
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196 | char *nonlocal_ignore = getenv(NONLOCAL_IGNORE_ENV); |
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197 | if (buflen == MAGIC_LOCAL_PW_BUFLEN || |
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198 | (nonlocal_ignore != NULL && nonlocal_ignore[0] != '\0')) |
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199 | return NSS_STATUS_UNAVAIL; |
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200 | |
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201 | if (pwent_nip == NULL) { |
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202 | status = _nss_nonlocal_setpwent(0); |
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203 | if (status != NSS_STATUS_SUCCESS) |
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204 | return status; |
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205 | } |
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206 | do { |
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207 | if (pwent_fct.ptr == NULL) |
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208 | status = NSS_STATUS_UNAVAIL; |
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209 | else { |
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210 | int nonlocal_errno; |
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211 | do |
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212 | status = DL_CALL_FCT(pwent_fct.l, (pwd, buffer, buflen, errnop)); |
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213 | while (status == NSS_STATUS_SUCCESS && |
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214 | check_nonlocal_uid(pwd->pw_name, pwd->pw_uid, &nonlocal_errno) != NSS_STATUS_SUCCESS); |
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215 | } |
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216 | if (status == NSS_STATUS_TRYAGAIN && *errnop == ERANGE) |
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217 | return status; |
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218 | |
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219 | if (status == NSS_STATUS_SUCCESS) |
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220 | return NSS_STATUS_SUCCESS; |
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221 | } while (__nss_next(&pwent_nip, pwent_fct_name, &pwent_fct.ptr, status, 0) == 0); |
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222 | |
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223 | pwent_nip = NULL; |
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224 | return NSS_STATUS_NOTFOUND; |
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225 | } |
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226 | |
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227 | |
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228 | enum nss_status |
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229 | _nss_nonlocal_getpwnam_r(const char *name, struct passwd *pwd, |
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230 | char *buffer, size_t buflen, int *errnop) |
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231 | { |
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232 | static const char *fct_name = "getpwnam_r"; |
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233 | static void *fct_start = NULL; |
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234 | enum nss_status status; |
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235 | service_user *nip; |
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236 | union { |
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237 | enum nss_status (*l)(const char *name, struct passwd *pwd, |
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238 | char *buffer, size_t buflen, int *errnop); |
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239 | void *ptr; |
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240 | } fct; |
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241 | int group_errno; |
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242 | |
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243 | char *nonlocal_ignore = getenv(NONLOCAL_IGNORE_ENV); |
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244 | if (buflen == MAGIC_LOCAL_PW_BUFLEN || |
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245 | (nonlocal_ignore != NULL && nonlocal_ignore[0] != '\0')) |
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246 | return NSS_STATUS_UNAVAIL; |
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247 | |
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248 | nip = nss_passwd_nonlocal_database(); |
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249 | if (nip == NULL) |
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250 | return NSS_STATUS_UNAVAIL; |
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251 | if (fct_start == NULL) |
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252 | fct_start = __nss_lookup_function(nip, fct_name); |
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253 | fct.ptr = fct_start; |
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254 | do { |
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255 | if (fct.ptr == NULL) |
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256 | status = NSS_STATUS_UNAVAIL; |
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257 | else |
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258 | status = DL_CALL_FCT(fct.l, (name, pwd, buffer, buflen, errnop)); |
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259 | if (status == NSS_STATUS_TRYAGAIN && *errnop == ERANGE) |
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260 | break; |
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261 | } while (__nss_next(&nip, fct_name, &fct.ptr, status, 0) == 0); |
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262 | if (status != NSS_STATUS_SUCCESS) |
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263 | return status; |
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264 | |
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265 | status = check_nonlocal_uid(name, pwd->pw_uid, errnop); |
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266 | if (status != NSS_STATUS_SUCCESS) |
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267 | return status; |
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268 | |
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269 | if (check_nonlocal_gid(name, pwd->pw_gid, &group_errno) != |
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270 | NSS_STATUS_SUCCESS) |
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271 | pwd->pw_gid = 65534 /* nogroup */; |
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272 | return NSS_STATUS_SUCCESS; |
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273 | } |
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274 | |
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275 | enum nss_status |
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276 | _nss_nonlocal_getpwuid_r(uid_t uid, struct passwd *pwd, |
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277 | char *buffer, size_t buflen, int *errnop) |
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278 | { |
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279 | static const char *fct_name = "getpwuid_r"; |
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280 | static void *fct_start = NULL; |
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281 | enum nss_status status; |
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282 | service_user *nip; |
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283 | union { |
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284 | enum nss_status (*l)(uid_t uid, struct passwd *pwd, |
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285 | char *buffer, size_t buflen, int *errnop); |
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286 | void *ptr; |
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287 | } fct; |
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288 | int group_errno; |
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289 | |
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290 | char *nonlocal_ignore = getenv(NONLOCAL_IGNORE_ENV); |
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291 | if (buflen == MAGIC_LOCAL_PW_BUFLEN || |
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292 | (nonlocal_ignore != NULL && nonlocal_ignore[0] != '\0')) |
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293 | return NSS_STATUS_UNAVAIL; |
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294 | |
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295 | nip = nss_passwd_nonlocal_database(); |
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296 | if (nip == NULL) |
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297 | return NSS_STATUS_UNAVAIL; |
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298 | if (fct_start == NULL) |
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299 | fct_start = __nss_lookup_function(nip, fct_name); |
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300 | fct.ptr = fct_start; |
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301 | do { |
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302 | if (fct.ptr == NULL) |
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303 | status = NSS_STATUS_UNAVAIL; |
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304 | else |
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305 | status = DL_CALL_FCT(fct.l, (uid, pwd, buffer, buflen, errnop)); |
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306 | if (status == NSS_STATUS_TRYAGAIN && *errnop == ERANGE) |
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307 | break; |
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308 | } while (__nss_next(&nip, fct_name, &fct.ptr, status, 0) == 0); |
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309 | if (status != NSS_STATUS_SUCCESS) |
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310 | return status; |
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311 | |
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312 | status = check_nonlocal_uid(pwd->pw_name, pwd->pw_uid, errnop); |
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313 | if (status != NSS_STATUS_SUCCESS) |
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314 | return status; |
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315 | |
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316 | if (check_nonlocal_gid(pwd->pw_name, pwd->pw_gid, &group_errno) != |
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317 | NSS_STATUS_SUCCESS) |
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318 | pwd->pw_gid = 65534 /* nogroup */; |
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319 | return NSS_STATUS_SUCCESS; |
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320 | } |
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