nsswitch/krb5_plugin/winbind_krb5_localauth.c

   1 /*
   2    Unix SMB/CIFS implementation.
   3
   4    A localauth plugin for MIT Kerberos
   5
   6    Copyright (C) 2018      Andreas Schneider <asn@samba.org>
   7
   8    This program is free software; you can redistribute it and/or modify
   9    it under the terms of the GNU General Public License as published by
  10    the Free Software Foundation; either version 3 of the License, or
  11    (at your option) any later version.
  12
  13    This program is distributed in the hope that it will be useful,
  14    but WITHOUT ANY WARRANTY; without even the implied warranty of
  15    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16    GNU General Public License for more details.
  17
  18    You should have received a copy of the GNU General Public License
  19    along with this program.  If not, see <http://www.gnu.org/licenses/>.
  20 */
  21
  22 #include "replace.h"
  23 #include <krb5/localauth_plugin.h>
  24 #include <wbclient.h>
  25 #ifdef HAVE_COM_ERR_H
  26 #include <com_err.h>
  27 #endif
  28
  29 struct krb5_localauth_moddata_st {
  30         struct wbcContext *wbc_ctx;
  31 };
  32
  33 /*
  34  * Initialize the module data.
  35  *
  36  * This creates the wbclient context.
  37  */
  38 static krb5_error_code winbind_init(krb5_context context,
  39                                     krb5_localauth_moddata *data)
  40 {
  41         krb5_localauth_moddata d;
  42
  43         *data = NULL;
  44         d = malloc(sizeof(struct krb5_localauth_moddata_st));
  45         if (d == NULL) {
  46                 return ENOMEM;
  47         }
  48
  49         d->wbc_ctx = wbcCtxCreate();
  50         if (d->wbc_ctx == NULL) {
  51                 free(d);
  52                 return ENOMEM;
  53         }
  54
  55         wbcSetClientProcessName("krb5_localauth_plugin");
  56
  57         *data = d;
  58
  59         return 0;
  60 }
  61
  62 /*
  63  * Release resources used by module data.
  64  */
  65 static void winbind_fini(krb5_context context, krb5_localauth_moddata data)
  66 {
  67         wbcCtxFree(data->wbc_ctx);
  68         free(data);
  69         data = NULL;
  70 }
  71
  72 /*
  73  * Determine whether aname is authorized to log in as the local account lname.
  74  *
  75  * Return 0 if aname is authorized, EPERM if aname is authoritatively not
  76  * authorized, KRB5_PLUGIN_NO_HANDLE if the module cannot determine whether
  77  * aname is authorized, and any other error code for a serious failure to
  78  * process the request.  aname will be considered authorized if at least one
  79  * module returns 0 and all other modules return KRB5_PLUGIN_NO_HANDLE.
  80  */
  81 static krb5_error_code winbind_userok(krb5_context context,
  82                                       krb5_localauth_moddata data,
  83                                       krb5_const_principal aname,
  84                                       const char *lname)
  85 {
  86         krb5_error_code code = 0;
  87         char *princ_str = NULL;
  88         struct passwd *pwd = NULL;
  89         uid_t princ_uid = (uid_t)-1;
  90         uid_t lname_uid = (uid_t)-1;
  91         wbcErr wbc_status;
  92         int cmp;
  93
  94         code = krb5_unparse_name(context, aname, &princ_str);
  95         if (code != 0) {
  96                 return code;
  97         }
  98
  99         cmp = strcasecmp(princ_str, lname);
 100         if (cmp == 0) {
 101                 goto out;
 102         }
 103
 104         wbc_status = wbcCtxGetpwnam(data->wbc_ctx,
 105                                     princ_str,
 106                                     &pwd);
 107         switch (wbc_status) {
 108         case WBC_ERR_SUCCESS:
 109                 princ_uid = pwd->pw_uid;
 110                 code = 0;
 111                 break;
 112         case WBC_ERR_UNKNOWN_USER:
 113         /* match other insane libwbclient return codes */
 114         case WBC_ERR_WINBIND_NOT_AVAILABLE:
 115         case WBC_ERR_DOMAIN_NOT_FOUND:
 116                 code = KRB5_PLUGIN_NO_HANDLE;
 117                 break;
 118         default:
 119                 code = EIO;
 120                 break;
 121         }
 122         wbcFreeMemory(pwd);
 123         if (code != 0) {
 124                 goto out;
 125         }
 126
 127         wbc_status = wbcCtxGetpwnam(data->wbc_ctx,
 128                                     lname,
 129                                     &pwd);
 130         switch (wbc_status) {
 131         case WBC_ERR_SUCCESS:
 132                 lname_uid = pwd->pw_uid;
 133                 break;
 134         case WBC_ERR_UNKNOWN_USER:
 135         /* match other insane libwbclient return codes */
 136         case WBC_ERR_WINBIND_NOT_AVAILABLE:
 137         case WBC_ERR_DOMAIN_NOT_FOUND:
 138                 code = KRB5_PLUGIN_NO_HANDLE;
 139                 break;
 140         default:
 141                 code = EIO;
 142                 break;
 143         }
 144         wbcFreeMemory(pwd);
 145         if (code != 0) {
 146                 goto out;
 147         }
 148
 149         if (princ_uid != lname_uid) {
 150                 code = EPERM;
 151         }
 152
 153         com_err("winbind_localauth",
 154                 code,
 155                 "Access %s: %s (uid=%u) %sequal to %s (uid=%u)",
 156                 code == 0 ? "granted" : "denied",
 157                 princ_str,
 158                 (unsigned int)princ_uid,
 159                 code == 0 ? "" : "not ",
 160                 lname,
 161                 (unsigned int)lname_uid);
 162
 163 out:
 164         krb5_free_unparsed_name(context, princ_str);
 165
 166         return code;
 167 }
 168
 169 /*
 170  * Determine the local account name corresponding to aname.
 171  *
 172  * Return 0 and set *lname_out if a mapping can be determined; the contents of
 173  * *lname_out will later be released with a call to the module's free_string
 174  * method.  Return KRB5_LNAME_NOTRANS if no mapping can be determined.  Return
 175  * any other error code for a serious failure to process the request; this will
 176  * halt the krb5_aname_to_localname operation.
 177  *
 178  * If the module's an2ln_types field is set, this method will only be invoked
 179  * when a profile "auth_to_local" value references one of the module's types.
 180  * type and residual will be set to the type and residual of the auth_to_local
 181  * value.
 182  *
 183  * If the module's an2ln_types field is not set but the an2ln method is
 184  * implemented, this method will be invoked independently of the profile's
 185  * auth_to_local settings, with type and residual set to NULL.  If multiple
 186  * modules are registered with an2ln methods but no an2ln_types field, the
 187  * order of invocation is not defined, but all such modules will be consulted
 188  * before the built-in mechanisms are tried.
 189  */
 190 static krb5_error_code winbind_an2ln(krb5_context context,
 191                                      krb5_localauth_moddata data,
 192                                      const char *type,
 193                                      const char *residual,
 194                                      krb5_const_principal aname,
 195                                      char **lname_out)
 196 {
 197         krb5_error_code code = 0;
 198         char *princ_str = NULL;
 199         char *name = NULL;
 200         struct passwd *pwd = NULL;
 201         wbcErr wbc_status;
 202
 203         code = krb5_unparse_name(context, aname, &princ_str);
 204         if (code != 0) {
 205                 return code;
 206         }
 207
 208         wbc_status = wbcCtxGetpwnam(data->wbc_ctx,
 209                                     princ_str,
 210                                     &pwd);
 211         krb5_free_unparsed_name(context, princ_str);
 212         switch (wbc_status) {
 213         case WBC_ERR_SUCCESS:
 214                 name = strdup(pwd->pw_name);
 215                 code = 0;
 216                 break;
 217         case WBC_ERR_UNKNOWN_USER:
 218         /* match other insane libwbclient return codes */
 219         case WBC_ERR_WINBIND_NOT_AVAILABLE:
 220         case WBC_ERR_DOMAIN_NOT_FOUND:
 221                 code = KRB5_LNAME_NOTRANS;
 222                 break;
 223         default:
 224                 code = EIO;
 225                 break;
 226         }
 227         wbcFreeMemory(pwd);
 228         if (code != 0) {
 229                 return code;
 230         }
 231
 232         if (name == NULL) {
 233                 return ENOMEM;
 234         }
 235
 236         *lname_out = name;
 237
 238         return code;
 239 }
 240
 241 /*
 242  * Release the memory returned by an invocation of an2ln.
 243  */
 244 static void winbind_free_string(krb5_context context,
 245                                 krb5_localauth_moddata data,
 246                                 char *str)
 247 {
 248         free(str);
 249 }
 250
 251 krb5_error_code
 252 localauth_winbind_initvt(krb5_context context,
 253                          int maj_ver,
 254                          int min_ver,
 255                          krb5_plugin_vtable vtable);
 256
 257 krb5_error_code
 258 localauth_winbind_initvt(krb5_context context,
 259                          int maj_ver,
 260                          int min_ver,
 261                          krb5_plugin_vtable vtable)
 262 {
 263         krb5_localauth_vtable vt = (krb5_localauth_vtable)vtable;
 264
 265         if (maj_ver != 1) {
 266                 com_err("winbind_localauth",
 267                         EINVAL,
 268                         "Failed to load, plugin API changed.");
 269                 return KRB5_PLUGIN_VER_NOTSUPP;
 270         }
 271
 272         vt->init = winbind_init;
 273         vt->fini = winbind_fini;
 274         vt->name = "winbind";
 275         vt->an2ln = winbind_an2ln;
 276         vt->userok = winbind_userok;
 277         vt->free_string = winbind_free_string;
 278
 279         return 0;
 280 }