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 RCSID("$Id$");
  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
  60     /* check type and mode of file */
  61     if (fstat(fileno(f), &st) != 0) {
  62         fclose (f);
  63         return errno;
  64     }
  65     if (S_ISDIR(st.st_mode)) {
  66         fclose (f);
  67         return EISDIR;
  68     }
  69     if (st.st_uid != pwd->pw_uid && st.st_uid != 0) {
  70         fclose (f);
  71         return EACCES;
  72     }
  73     if ((st.st_mode & (S_IWGRP | S_IWOTH)) != 0) {
  74         fclose (f);
  75         return EACCES;
  76     }
  77
  78     while (fgets (buf, sizeof(buf), f) != NULL) {
  79         krb5_principal tmp;
  80         char *newline = buf + strcspn(buf, "\n");
  81
  82         if(*newline != '\n') {
  83             int c;
  84             c = fgetc(f);
  85             if(c != EOF) {
  86                 while(c != EOF && c != '\n')
  87                     c = fgetc(f);
  88                 /* line was too long, so ignore it */
  89                 continue;
  90             }
  91         }
  92         *newline = '\0';
  93         ret = krb5_parse_name (context, buf, &tmp);
  94         if (ret)
  95             continue;
  96         *result = krb5_principal_compare (context, principal, tmp);
  97         krb5_free_principal (context, tmp);
  98         if (*result) {
  99             fclose (f);
 100             return 0;
 101         }
 102     }
 103     fclose (f);
 104     return 0;
 105 }
 106
 107 static krb5_error_code
 108 check_directory(krb5_context context,
 109                 const char *dirname,
 110                 struct passwd *pwd,
 111                 krb5_principal principal,
 112                 krb5_boolean *result)
 113 {
 114     DIR *d;
 115     struct dirent *dent;
 116     char filename[MAXPATHLEN];
 117     krb5_error_code ret = 0;
 118     struct stat st;
 119
 120     *result = FALSE;
 121
 122     if(lstat(dirname, &st) < 0)
 123         return errno;
 124
 125     if (!S_ISDIR(st.st_mode))
 126         return ENOTDIR;
 127
 128     if (st.st_uid != pwd->pw_uid && st.st_uid != 0)
 129         return EACCES;
 130     if ((st.st_mode & (S_IWGRP | S_IWOTH)) != 0)
 131         return EACCES;
 132
 133     if((d = opendir(dirname)) == NULL)
 134         return errno;
 135
 136 #ifdef HAVE_DIRFD
 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 #endif
 152
 153     while((dent = readdir(d)) != NULL) {
 154         if(strcmp(dent->d_name, ".") == 0 ||
 155            strcmp(dent->d_name, "..") == 0 ||
 156            dent->d_name[0] == '#' ||                      /* emacs autosave */
 157            dent->d_name[strlen(dent->d_name) - 1] == '~') /* emacs backup */
 158             continue;
 159         snprintf(filename, sizeof(filename), "%s/%s", dirname, dent->d_name);
 160         ret = check_one_file(context, filename, pwd, principal, result);
 161         if(ret == 0 && *result == TRUE)
 162             break;
 163         ret = 0; /* don't propagate errors upstream */
 164     }
 165     closedir(d);
 166     return ret;
 167 }
 168
 169 static krb5_boolean
 170 match_local_principals(krb5_context context,
 171                        krb5_principal principal,
 172                        const char *luser)
 173 {
 174     krb5_error_code ret;
 175     krb5_realm *realms, *r;
 176     krb5_boolean result = FALSE;
 177
 178     /* multi-component principals can never match */
 179     if(krb5_principal_get_comp_string(context, principal, 1) != NULL)
 180         return FALSE;
 181
 182     ret = krb5_get_default_realms (context, &realms);
 183     if (ret)
 184         return FALSE;
 185
 186     for (r = realms; *r != NULL; ++r) {
 187         if(strcmp(krb5_principal_get_realm(context, principal),
 188                   *r) != 0)
 189             continue;
 190         if(strcmp(krb5_principal_get_comp_string(context, principal, 0),
 191                   luser) == 0) {
 192             result = TRUE;
 193             break;
 194         }
 195     }
 196     krb5_free_host_realm (context, realms);
 197     return result;
 198 }
 199
 200 /**
 201  * Return TRUE iff `principal' is allowed to login as `luser'.
 202  */
 203
 204 krb5_boolean KRB5_LIB_FUNCTION
 205 krb5_kuserok (krb5_context context,
 206               krb5_principal principal,
 207               const char *luser)
 208 {
 209     char *buf;
 210     size_t buflen;
 211     struct passwd *pwd;
 212     krb5_error_code ret;
 213     krb5_boolean result = FALSE;
 214
 215     krb5_boolean found_file = FALSE;
 216
 217 #ifdef POSIX_GETPWNAM_R
 218     char pwbuf[2048];
 219     struct passwd pw;
 220
 221     if(getpwnam_r(luser, &pw, pwbuf, sizeof(pwbuf), &pwd) != 0)
 222         return FALSE;
 223 #else
 224     pwd = getpwnam (luser);
 225 #endif
 226     if (pwd == NULL)
 227         return FALSE;
 228
 229 #define KLOGIN "/.k5login"
 230     buflen = strlen(pwd->pw_dir) + sizeof(KLOGIN) + 2; /* 2 for .d */
 231     buf = malloc(buflen);
 232     if(buf == NULL)
 233         return FALSE;
 234     /* check user's ~/.k5login */
 235     strlcpy(buf, pwd->pw_dir, buflen);
 236     strlcat(buf, KLOGIN, buflen);
 237     ret = check_one_file(context, buf, pwd, principal, &result);
 238
 239     if(ret == 0 && result == TRUE) {
 240         free(buf);
 241         return TRUE;
 242     }
 243
 244     if(ret != ENOENT)
 245         found_file = TRUE;
 246
 247     strlcat(buf, ".d", buflen);
 248     ret = check_directory(context, buf, pwd, principal, &result);
 249     free(buf);
 250     if(ret == 0 && result == TRUE)
 251         return TRUE;
 252
 253     if(ret != ENOENT && ret != ENOTDIR)
 254         found_file = TRUE;
 255
 256     /* finally if no files exist, allow all principals matching
 257        <localuser>@<LOCALREALM> */
 258     if(found_file == FALSE)
 259         return match_local_principals(context, principal, luser);
 260
 261     return FALSE;
 262 }