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 | |
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47 | enum nss_status |
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48 | _nss_nonlocal_getpwuid_r(uid_t uid, struct passwd *pwd, |
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49 | char *buffer, size_t buflen, int *errnop); |
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50 | enum nss_status |
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51 | _nss_nonlocal_getpwnam_r(const char *name, struct passwd *pwd, |
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52 | char *buffer, size_t buflen, int *errnop); |
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53 | |
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54 | |
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55 | static service_user * |
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56 | nss_passwd_nonlocal_database(void) |
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57 | { |
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58 | static service_user *nip = NULL; |
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59 | if (nip == NULL) |
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60 | __nss_database_lookup("passwd_nonlocal", NULL, "", &nip); |
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61 | |
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62 | return nip; |
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63 | } |
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64 | |
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65 | |
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66 | enum nss_status |
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67 | check_nonlocal_uid(const char *user, uid_t uid, int *errnop) |
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68 | { |
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69 | static const char *fct_name = "getpwuid_r"; |
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70 | static service_user *startp = NULL; |
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71 | static void *fct_start = NULL; |
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72 | enum nss_status status; |
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73 | service_user *nip; |
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74 | union { |
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75 | enum nss_status (*l)(uid_t uid, struct passwd *pwd, |
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76 | char *buffer, size_t buflen, int *errnop); |
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77 | void *ptr; |
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78 | } fct; |
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79 | struct passwd pwbuf; |
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80 | int old_errno = errno; |
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81 | |
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82 | size_t buflen = sysconf(_SC_GETPW_R_SIZE_MAX); |
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83 | char *buf = malloc(buflen); |
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84 | if (buf == NULL) { |
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85 | *errnop = ENOMEM; |
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86 | errno = old_errno; |
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87 | return NSS_STATUS_TRYAGAIN; |
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88 | } |
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89 | |
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90 | if (fct_start == NULL && |
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91 | __nss_passwd_lookup(&startp, fct_name, &fct_start) != 0) { |
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92 | free(buf); |
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93 | return NSS_STATUS_UNAVAIL; |
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94 | } |
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95 | nip = startp; |
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96 | fct.ptr = fct_start; |
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97 | do { |
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98 | morebuf: |
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99 | if (fct.l == _nss_nonlocal_getpwuid_r) |
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100 | status = NSS_STATUS_NOTFOUND; |
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101 | else |
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102 | status = DL_CALL_FCT(fct.l, (uid, &pwbuf, buf, buflen, errnop)); |
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103 | if (status == NSS_STATUS_TRYAGAIN && *errnop == ERANGE) { |
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104 | free(buf); |
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105 | buflen *= 2; |
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106 | buf = malloc(buflen); |
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107 | if (buf == NULL) { |
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108 | *errnop = ENOMEM; |
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109 | errno = old_errno; |
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110 | return NSS_STATUS_TRYAGAIN; |
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111 | } |
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112 | goto morebuf; |
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113 | } |
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114 | } while (__nss_next(&nip, fct_name, &fct.ptr, status, 0) == 0); |
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115 | |
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116 | if (status == NSS_STATUS_SUCCESS) { |
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117 | 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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118 | status = NSS_STATUS_NOTFOUND; |
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119 | } else if (status != NSS_STATUS_TRYAGAIN) { |
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120 | status = NSS_STATUS_SUCCESS; |
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121 | } |
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122 | |
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123 | free(buf); |
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124 | return status; |
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125 | } |
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126 | |
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127 | enum nss_status |
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128 | check_nonlocal_passwd(const char *user, struct passwd *pwd, int *errnop) |
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129 | { |
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130 | enum nss_status status = NSS_STATUS_SUCCESS; |
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131 | int old_errno = errno; |
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132 | char *end; |
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133 | unsigned long uid; |
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134 | |
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135 | errno = 0; |
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136 | uid = strtoul(pwd->pw_name, &end, 10); |
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137 | if (errno == 0 && *end == '\0' && (uid_t)uid == uid) |
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138 | status = check_nonlocal_uid(user, uid, errnop); |
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139 | errno = old_errno; |
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140 | if (status != NSS_STATUS_SUCCESS) |
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141 | return status; |
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142 | |
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143 | return check_nonlocal_uid(user, pwd->pw_uid, errnop); |
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144 | } |
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145 | |
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146 | enum nss_status |
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147 | check_nonlocal_user(const char *user, int *errnop) |
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148 | { |
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149 | static const char *fct_name = "getpwnam_r"; |
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150 | static service_user *startp = NULL; |
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151 | static void *fct_start = NULL; |
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152 | enum nss_status status; |
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153 | service_user *nip; |
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154 | union { |
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155 | enum nss_status (*l)(const char *name, struct passwd *pwd, |
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156 | char *buffer, size_t buflen, int *errnop); |
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157 | void *ptr; |
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158 | } fct; |
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159 | struct passwd pwbuf; |
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160 | int old_errno = errno; |
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161 | |
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162 | size_t buflen = sysconf(_SC_GETPW_R_SIZE_MAX); |
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163 | char *buf = malloc(buflen); |
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164 | if (buf == NULL) { |
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165 | *errnop = ENOMEM; |
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166 | errno = old_errno; |
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167 | return NSS_STATUS_TRYAGAIN; |
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168 | } |
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169 | |
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170 | if (fct_start == NULL && |
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171 | __nss_passwd_lookup(&startp, fct_name, &fct_start) != 0) { |
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172 | free(buf); |
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173 | return NSS_STATUS_UNAVAIL; |
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174 | } |
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175 | nip = startp; |
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176 | fct.ptr = fct_start; |
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177 | do { |
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178 | morebuf: |
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179 | if (fct.l == _nss_nonlocal_getpwnam_r) |
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180 | status = NSS_STATUS_NOTFOUND; |
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181 | else |
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182 | status = DL_CALL_FCT(fct.l, (user, &pwbuf, buf, buflen, errnop)); |
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183 | if (status == NSS_STATUS_TRYAGAIN && *errnop == ERANGE) { |
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184 | free(buf); |
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185 | buflen *= 2; |
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186 | buf = malloc(buflen); |
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187 | if (buf == NULL) { |
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188 | *errnop = ENOMEM; |
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189 | errno = old_errno; |
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190 | return NSS_STATUS_TRYAGAIN; |
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191 | } |
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192 | goto morebuf; |
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193 | } |
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194 | } while (__nss_next(&nip, fct_name, &fct.ptr, status, 0) == 0); |
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195 | |
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196 | if (status == NSS_STATUS_SUCCESS) |
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197 | status = NSS_STATUS_NOTFOUND; |
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198 | else if (status != NSS_STATUS_TRYAGAIN) |
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199 | status = NSS_STATUS_SUCCESS; |
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200 | |
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201 | free(buf); |
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202 | return status; |
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203 | } |
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204 | |
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205 | |
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206 | static service_user *pwent_nip = NULL; |
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207 | static void *pwent_fct_start; |
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208 | static union { |
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209 | enum nss_status (*l)(struct passwd *pwd, char *buffer, size_t buflen, |
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210 | int *errnop); |
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211 | void *ptr; |
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212 | } pwent_fct; |
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213 | static const char *pwent_fct_name = "getpwent_r"; |
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214 | |
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215 | enum nss_status |
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216 | _nss_nonlocal_setpwent(int stayopen) |
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217 | { |
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218 | static const char *fct_name = "setpwent"; |
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219 | static void *fct_start = NULL; |
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220 | enum nss_status status; |
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221 | service_user *nip; |
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222 | union { |
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223 | enum nss_status (*l)(int stayopen); |
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224 | void *ptr; |
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225 | } fct; |
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226 | |
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227 | nip = nss_passwd_nonlocal_database(); |
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228 | if (nip == NULL) |
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229 | return NSS_STATUS_UNAVAIL; |
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230 | if (fct_start == NULL) |
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231 | fct_start = __nss_lookup_function(nip, fct_name); |
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232 | fct.ptr = fct_start; |
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233 | do { |
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234 | if (fct.ptr == NULL) |
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235 | status = NSS_STATUS_UNAVAIL; |
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236 | else |
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237 | status = DL_CALL_FCT(fct.l, (stayopen)); |
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238 | } while (__nss_next(&nip, fct_name, &fct.ptr, status, 0) == 0); |
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239 | if (status != NSS_STATUS_SUCCESS) |
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240 | return status; |
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241 | |
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242 | pwent_nip = nip; |
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243 | if (pwent_fct_start == NULL) |
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244 | pwent_fct_start = __nss_lookup_function(nip, pwent_fct_name); |
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245 | pwent_fct.ptr = pwent_fct_start; |
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246 | return NSS_STATUS_SUCCESS; |
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247 | } |
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248 | |
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249 | enum nss_status |
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250 | _nss_nonlocal_endpwent(void) |
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251 | { |
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252 | static const char *fct_name = "endpwent"; |
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253 | static void *fct_start = NULL; |
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254 | enum nss_status status; |
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255 | service_user *nip; |
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256 | union { |
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257 | enum nss_status (*l)(void); |
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258 | void *ptr; |
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259 | } fct; |
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260 | |
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261 | pwent_nip = NULL; |
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262 | |
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263 | nip = nss_passwd_nonlocal_database(); |
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264 | if (nip == NULL) |
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265 | return NSS_STATUS_UNAVAIL; |
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266 | if (fct_start == NULL) |
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267 | fct_start = __nss_lookup_function(nip, fct_name); |
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268 | fct.ptr = fct_start; |
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269 | do { |
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270 | if (fct.ptr == NULL) |
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271 | status = NSS_STATUS_UNAVAIL; |
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272 | else |
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273 | status = DL_CALL_FCT(fct.l, ()); |
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274 | } while (__nss_next(&nip, fct_name, &fct.ptr, status, 0) == 0); |
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275 | return status; |
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276 | } |
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277 | |
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278 | enum nss_status |
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279 | _nss_nonlocal_getpwent_r(struct passwd *pwd, char *buffer, size_t buflen, |
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280 | int *errnop) |
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281 | { |
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282 | enum nss_status status; |
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283 | |
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284 | char *nonlocal_ignore = getenv(NONLOCAL_IGNORE_ENV); |
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285 | if (nonlocal_ignore != NULL && nonlocal_ignore[0] != '\0') |
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286 | return NSS_STATUS_UNAVAIL; |
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287 | |
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288 | if (pwent_nip == NULL) { |
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289 | status = _nss_nonlocal_setpwent(0); |
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290 | if (status != NSS_STATUS_SUCCESS) |
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291 | return status; |
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292 | } |
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293 | do { |
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294 | if (pwent_fct.ptr == NULL) |
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295 | status = NSS_STATUS_UNAVAIL; |
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296 | else { |
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297 | int nonlocal_errno; |
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298 | do |
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299 | status = DL_CALL_FCT(pwent_fct.l, (pwd, buffer, buflen, errnop)); |
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300 | while (status == NSS_STATUS_SUCCESS && |
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301 | check_nonlocal_passwd(pwd->pw_name, pwd, &nonlocal_errno) != NSS_STATUS_SUCCESS); |
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302 | } |
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303 | if (status == NSS_STATUS_TRYAGAIN && *errnop == ERANGE) |
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304 | return status; |
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305 | |
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306 | if (status == NSS_STATUS_SUCCESS) |
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307 | return NSS_STATUS_SUCCESS; |
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308 | } while (__nss_next(&pwent_nip, pwent_fct_name, &pwent_fct.ptr, status, 0) == 0); |
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309 | |
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310 | pwent_nip = NULL; |
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311 | return NSS_STATUS_NOTFOUND; |
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312 | } |
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313 | |
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314 | |
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315 | enum nss_status |
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316 | _nss_nonlocal_getpwnam_r(const char *name, struct passwd *pwd, |
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317 | char *buffer, size_t buflen, int *errnop) |
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318 | { |
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319 | static const char *fct_name = "getpwnam_r"; |
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320 | static void *fct_start = NULL; |
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321 | enum nss_status status; |
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322 | service_user *nip; |
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323 | union { |
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324 | enum nss_status (*l)(const char *name, struct passwd *pwd, |
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325 | char *buffer, size_t buflen, int *errnop); |
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326 | void *ptr; |
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327 | } fct; |
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328 | int group_errno; |
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329 | |
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330 | char *nonlocal_ignore = getenv(NONLOCAL_IGNORE_ENV); |
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331 | if (nonlocal_ignore != NULL && nonlocal_ignore[0] != '\0') |
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332 | return NSS_STATUS_UNAVAIL; |
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333 | |
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334 | nip = nss_passwd_nonlocal_database(); |
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335 | if (nip == NULL) |
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336 | return NSS_STATUS_UNAVAIL; |
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337 | if (fct_start == NULL) |
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338 | fct_start = __nss_lookup_function(nip, fct_name); |
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339 | fct.ptr = fct_start; |
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340 | do { |
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341 | if (fct.ptr == NULL) |
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342 | status = NSS_STATUS_UNAVAIL; |
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343 | else |
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344 | status = DL_CALL_FCT(fct.l, (name, pwd, buffer, buflen, errnop)); |
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345 | if (status == NSS_STATUS_TRYAGAIN && *errnop == ERANGE) |
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346 | break; |
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347 | } while (__nss_next(&nip, fct_name, &fct.ptr, status, 0) == 0); |
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348 | if (status != NSS_STATUS_SUCCESS) |
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349 | return status; |
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350 | |
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351 | if (strcmp(name, pwd->pw_name) != 0) { |
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352 | syslog(LOG_ERR, "nss_nonlocal: discarding user %s from lookup for user %s\n", pwd->pw_name, name); |
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353 | return NSS_STATUS_NOTFOUND; |
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354 | } |
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355 | |
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356 | status = check_nonlocal_passwd(name, pwd, errnop); |
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357 | if (status != NSS_STATUS_SUCCESS) |
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358 | return status; |
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359 | |
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360 | if (check_nonlocal_gid(name, pwd->pw_gid, &group_errno) != |
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361 | NSS_STATUS_SUCCESS) |
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362 | pwd->pw_gid = 65534 /* nogroup */; |
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363 | return NSS_STATUS_SUCCESS; |
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364 | } |
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365 | |
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366 | enum nss_status |
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367 | _nss_nonlocal_getpwuid_r(uid_t uid, struct passwd *pwd, |
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368 | char *buffer, size_t buflen, int *errnop) |
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369 | { |
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370 | static const char *fct_name = "getpwuid_r"; |
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371 | static void *fct_start = NULL; |
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372 | enum nss_status status; |
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373 | service_user *nip; |
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374 | union { |
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375 | enum nss_status (*l)(uid_t uid, struct passwd *pwd, |
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376 | char *buffer, size_t buflen, int *errnop); |
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377 | void *ptr; |
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378 | } fct; |
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379 | int group_errno; |
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380 | |
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381 | char *nonlocal_ignore = getenv(NONLOCAL_IGNORE_ENV); |
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382 | if (nonlocal_ignore != NULL && nonlocal_ignore[0] != '\0') |
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383 | return NSS_STATUS_UNAVAIL; |
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384 | |
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385 | nip = nss_passwd_nonlocal_database(); |
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386 | if (nip == NULL) |
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387 | return NSS_STATUS_UNAVAIL; |
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388 | if (fct_start == NULL) |
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389 | fct_start = __nss_lookup_function(nip, fct_name); |
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390 | fct.ptr = fct_start; |
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391 | do { |
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392 | if (fct.ptr == NULL) |
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393 | status = NSS_STATUS_UNAVAIL; |
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394 | else |
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395 | status = DL_CALL_FCT(fct.l, (uid, pwd, buffer, buflen, errnop)); |
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396 | if (status == NSS_STATUS_TRYAGAIN && *errnop == ERANGE) |
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397 | break; |
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398 | } while (__nss_next(&nip, fct_name, &fct.ptr, status, 0) == 0); |
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399 | if (status != NSS_STATUS_SUCCESS) |
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400 | return status; |
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401 | |
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402 | status = check_nonlocal_passwd(pwd->pw_name, pwd, errnop); |
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403 | if (status != NSS_STATUS_SUCCESS) |
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404 | return status; |
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405 | |
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406 | if (check_nonlocal_gid(pwd->pw_name, pwd->pw_gid, &group_errno) != |
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407 | NSS_STATUS_SUCCESS) |
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408 | pwd->pw_gid = 65534 /* nogroup */; |
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409 | return NSS_STATUS_SUCCESS; |
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410 | } |
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