lib/krb5/kuserok.c

   1 /*
   2  * Copyright (c) 1997 - 2005 Kungliga Tekniska Högskolan
   3  * (Royal Institute of Technology, Stockholm, Sweden).
   4  * All rights reserved.
   5  *
   6  * Redistribution and use in source and binary forms, with or without
   7  * modification, are permitted provided that the following conditions
   8  * are met:
   9  *
  10  * 1. Redistributions of source code must retain the above copyright
  11  *    notice, this list of conditions and the following disclaimer.
  12  *
  13  * 2. Redistributions in binary form must reproduce the above copyright
  14  *    notice, this list of conditions and the following disclaimer in the
  15  *    documentation and/or other materials provided with the distribution.
  16  *
  17  * 3. Neither the name of the Institute nor the names of its contributors
  18  *    may be used to endorse or promote products derived from this software
  19  *    without specific prior written permission.
  20  *
  21  * THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
  22  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  23  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  24  * ARE DISCLAIMED.  IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
  25  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  26  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  27  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  28  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  29  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  30  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  31  * SUCH DAMAGE.
  32  */
  33
  34 #include "krb5_locl.h"
  35 #include <dirent.h>
  36
  37 #ifndef _WIN32
  38
  39 /* see if principal is mentioned in the filename access file, return
  40    TRUE (in result) if so, FALSE otherwise */
  41
  42 static krb5_error_code
  43 check_one_file(krb5_context context,
  44                const char *filename,
  45                struct passwd *pwd,
  46                krb5_principal principal,
  47                krb5_boolean *result)
  48 {
  49     FILE *f;
  50     char buf[BUFSIZ];
  51     krb5_error_code ret;
  52     struct stat st;
  53
  54     *result = FALSE;
  55
  56     f = fopen (filename, "r");
  57     if (f == NULL)
  58         return errno;
  59     rk_cloexec_file(f);
  60
  61     /* check type and mode of file */
  62     if (fstat(fileno(f), &st) != 0) {
  63         fclose (f);
  64         return errno;
  65     }
  66     if (S_ISDIR(st.st_mode)) {
  67         fclose (f);
  68         return EISDIR;
  69     }
  70     if (st.st_uid != pwd->pw_uid && st.st_uid != 0) {
  71         fclose (f);
  72         return EACCES;
  73     }
  74     if ((st.st_mode & (S_IWGRP | S_IWOTH)) != 0) {
  75         fclose (f);
  76         return EACCES;
  77     }
  78
  79     while (fgets (buf, sizeof(buf), f) != NULL) {
  80         krb5_principal tmp;
  81         char *newline = buf + strcspn(buf, "\n");
  82
  83         if(*newline != '\n') {
  84             int c;
  85             c = fgetc(f);
  86             if(c != EOF) {
  87                 while(c != EOF && c != '\n')
  88                     c = fgetc(f);
  89                 /* line was too long, so ignore it */
  90                 continue;
  91             }
  92         }
  93         *newline = '\0';
  94         ret = krb5_parse_name (context, buf, &tmp);
  95         if (ret)
  96             continue;
  97         *result = krb5_principal_compare (context, principal, tmp);
  98         krb5_free_principal (context, tmp);
  99         if (*result) {
 100             fclose (f);
 101             return 0;
 102         }
 103     }
 104     fclose (f);
 105     return 0;
 106 }
 107
 108 static krb5_error_code
 109 check_directory(krb5_context context,
 110                 const char *dirname,
 111                 struct passwd *pwd,
 112                 krb5_principal principal,
 113                 krb5_boolean *result)
 114 {
 115     DIR *d;
 116     struct dirent *dent;
 117     char filename[MAXPATHLEN];
 118     krb5_error_code ret = 0;
 119     struct stat st;
 120
 121     *result = FALSE;
 122
 123     if(lstat(dirname, &st) < 0)
 124         return errno;
 125
 126     if (!S_ISDIR(st.st_mode))
 127         return ENOTDIR;
 128
 129     if (st.st_uid != pwd->pw_uid && st.st_uid != 0)
 130         return EACCES;
 131     if ((st.st_mode & (S_IWGRP | S_IWOTH)) != 0)
 132         return EACCES;
 133
 134     if((d = opendir(dirname)) == NULL)
 135         return errno;
 136
 137     {
 138         int fd;
 139         struct stat st2;
 140
 141         fd = dirfd(d);
 142         if(fstat(fd, &st2) < 0) {
 143             closedir(d);
 144             return errno;
 145         }
 146         if(st.st_dev != st2.st_dev || st.st_ino != st2.st_ino) {
 147             closedir(d);
 148             return EACCES;
 149         }
 150     }
 151
 152     while((dent = readdir(d)) != NULL) {
 153         if(strcmp(dent->d_name, ".") == 0 ||
 154            strcmp(dent->d_name, "..") == 0 ||
 155            dent->d_name[0] == '#' ||                      /* emacs autosave */
 156            dent->d_name[strlen(dent->d_name) - 1] == '~') /* emacs backup */
 157             continue;
 158         snprintf(filename, sizeof(filename), "%s/%s", dirname, dent->d_name);
 159         ret = check_one_file(context, filename, pwd, principal, result);
 160         if(ret == 0 && *result == TRUE)
 161             break;
 162         ret = 0; /* don't propagate errors upstream */
 163     }
 164     closedir(d);
 165     return ret;
 166 }
 167
 168 #endif  /* !_WIN32 */
 169
 170 static krb5_boolean
 171 match_local_principals(krb5_context context,
 172                        krb5_principal principal,
 173                        const char *luser)
 174 {
 175     krb5_error_code ret;
 176     krb5_realm *realms, *r;
 177     krb5_boolean result = FALSE;
 178
 179     /* multi-component principals can never match */
 180     if(krb5_principal_get_comp_string(context, principal, 1) != NULL)
 181         return FALSE;
 182
 183     ret = krb5_get_default_realms (context, &realms);
 184     if (ret)
 185         return FALSE;
 186
 187     for (r = realms; *r != NULL; ++r) {
 188         if(strcmp(krb5_principal_get_realm(context, principal),
 189                   *r) != 0)
 190             continue;
 191         if(strcmp(krb5_principal_get_comp_string(context, principal, 0),
 192                   luser) == 0) {
 193             result = TRUE;
 194             break;
 195         }
 196     }
 197     krb5_free_host_realm (context, realms);
 198     return result;
 199 }
 200
 201 /**
 202  * This function takes the name of a local user and checks if
 203  * principal is allowed to log in as that user.
 204  *
 205  * The user may have a ~/.k5login file listing principals that are
 206  * allowed to login as that user. If that file does not exist, all
 207  * principals with a first component identical to the username, and a
 208  * realm considered local, are allowed access.
 209  *
 210  * The .k5login file must contain one principal per line, be owned by
 211  * user and not be writable by group or other (but must be readable by
 212  * anyone).
 213  *
 214  * Note that if the file exists, no implicit access rights are given
 215  * to user@@LOCALREALM.
 216  *
 217  * Optionally, a set of files may be put in ~/.k5login.d (a
 218  * directory), in which case they will all be checked in the same
 219  * manner as .k5login.  The files may be called anything, but files
 220  * starting with a hash (#) , or ending with a tilde (~) are
 221  * ignored. Subdirectories are not traversed. Note that this directory
 222  * may not be checked by other Kerberos implementations.
 223  *
 224  * If no configuration file exists, match user against local domains,
 225  * ie luser@@LOCAL-REALMS-IN-CONFIGURATION-FILES.
 226  *
 227  * @param context Kerberos 5 context.
 228  * @param principal principal to check if allowed to login
 229  * @param luser local user id
 230  *
 231  * @return returns TRUE if access should be granted, FALSE otherwise.
 232  *
 233  * @ingroup krb5_support
 234  */
 235
 236 KRB5_LIB_FUNCTION krb5_boolean KRB5_LIB_CALL
 237 krb5_kuserok (krb5_context context,
 238               krb5_principal principal,
 239               const char *luser)
 240 {
 241 #ifndef _WIN32
 242     char *buf;
 243     size_t buflen;
 244     struct passwd *pwd = NULL;
 245     char *profile_dir = NULL;
 246     krb5_error_code ret;
 247     krb5_boolean result = FALSE;
 248
 249     krb5_boolean found_file = FALSE;
 250
 251 #ifdef POSIX_GETPWNAM_R
 252     char pwbuf[2048];
 253     struct passwd pw;
 254
 255     if(getpwnam_r(luser, &pw, pwbuf, sizeof(pwbuf), &pwd) != 0)
 256         return FALSE;
 257 #else
 258     pwd = getpwnam (luser);
 259 #endif
 260     if (pwd == NULL)
 261         return FALSE;
 262     profile_dir = pwd->pw_dir;
 263
 264 #define KLOGIN "/.k5login"
 265     buflen = strlen(profile_dir) + sizeof(KLOGIN) + 2; /* 2 for .d */
 266     buf = malloc(buflen);
 267     if(buf == NULL)
 268         return FALSE;
 269     /* check user's ~/.k5login */
 270     strlcpy(buf, profile_dir, buflen);
 271     strlcat(buf, KLOGIN, buflen);
 272     ret = check_one_file(context, buf, pwd, principal, &result);
 273
 274     if(ret == 0 && result == TRUE) {
 275         free(buf);
 276         return TRUE;
 277     }
 278
 279     if(ret != ENOENT)
 280         found_file = TRUE;
 281
 282     strlcat(buf, ".d", buflen);
 283     ret = check_directory(context, buf, pwd, principal, &result);
 284     free(buf);
 285     if(ret == 0 && result == TRUE)
 286         return TRUE;
 287
 288     if(ret != ENOENT && ret != ENOTDIR)
 289         found_file = TRUE;
 290
 291     /* finally if no files exist, allow all principals matching
 292        <localuser>@<LOCALREALM> */
 293     if(found_file == FALSE)
 294         return match_local_principals(context, principal, luser);
 295
 296     return FALSE;
 297 #else
 298     /* The .k5login file may be on a remote profile and we don't have
 299        access to the profile until we have a token handle for the
 300        user's credentials. */
 301     return match_local_principals(context, principal, luser);
 302 #endif
 303 }