1 /* $NetBSD: kuserok.c,v 1.1.1.2 2014/04/24 12:45:50 pettai Exp $ */
2
3 /*
4 * Copyright (c) 1997 - 2005 Kungliga Tekniska Högskolan
5 * (Royal Institute of Technology, Stockholm, Sweden).
6 * All rights reserved.
7 *
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
10 * are met:
11 *
12 * 1. Redistributions of source code must retain the above copyright
13 * notice, this list of conditions and the following disclaimer.
14 *
15 * 2. Redistributions in binary form must reproduce the above copyright
16 * notice, this list of conditions and the following disclaimer in the
17 * documentation and/or other materials provided with the distribution.
18 *
19 * 3. Neither the name of the Institute nor the names of its contributors
20 * may be used to endorse or promote products derived from this software
21 * without specific prior written permission.
22 *
23 * THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
24 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
25 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
26 * ARE DISCLAIMED. IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
27 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
28 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
29 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
30 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
31 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
32 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
33 * SUCH DAMAGE.
34 */
35
36 #include "krb5_locl.h"
37 #include <dirent.h>
38
39 #ifndef _WIN32
40
41 /* see if principal is mentioned in the filename access file, return
42 TRUE (in result) if so, FALSE otherwise */
43
44 static krb5_error_code
check_one_file(krb5_context context,const char * filename,struct passwd * pwd,krb5_principal principal,krb5_boolean * result)45 check_one_file(krb5_context context,
46 const char *filename,
47 struct passwd *pwd,
48 krb5_principal principal,
49 krb5_boolean *result)
50 {
51 FILE *f;
52 char buf[BUFSIZ];
53 krb5_error_code ret;
54 struct stat st;
55
56 *result = FALSE;
57
58 f = fopen (filename, "r");
59 if (f == NULL)
60 return errno;
61 rk_cloexec_file(f);
62
63 /* check type and mode of file */
64 if (fstat(fileno(f), &st) != 0) {
65 fclose (f);
66 return errno;
67 }
68 if (S_ISDIR(st.st_mode)) {
69 fclose (f);
70 return EISDIR;
71 }
72 if (st.st_uid != pwd->pw_uid && st.st_uid != 0) {
73 fclose (f);
74 return EACCES;
75 }
76 if ((st.st_mode & (S_IWGRP | S_IWOTH)) != 0) {
77 fclose (f);
78 return EACCES;
79 }
80
81 while (fgets (buf, sizeof(buf), f) != NULL) {
82 krb5_principal tmp;
83 char *newline = buf + strcspn(buf, "\n");
84
85 if(*newline != '\n') {
86 int c;
87 c = fgetc(f);
88 if(c != EOF) {
89 while(c != EOF && c != '\n')
90 c = fgetc(f);
91 /* line was too long, so ignore it */
92 continue;
93 }
94 }
95 *newline = '\0';
96 ret = krb5_parse_name (context, buf, &tmp);
97 if (ret)
98 continue;
99 *result = krb5_principal_compare (context, principal, tmp);
100 krb5_free_principal (context, tmp);
101 if (*result) {
102 fclose (f);
103 return 0;
104 }
105 }
106 fclose (f);
107 return 0;
108 }
109
110 static krb5_error_code
check_directory(krb5_context context,const char * dirname,struct passwd * pwd,krb5_principal principal,krb5_boolean * result)111 check_directory(krb5_context context,
112 const char *dirname,
113 struct passwd *pwd,
114 krb5_principal principal,
115 krb5_boolean *result)
116 {
117 DIR *d;
118 struct dirent *dent;
119 char filename[MAXPATHLEN];
120 krb5_error_code ret = 0;
121 struct stat st;
122
123 *result = FALSE;
124
125 if(lstat(dirname, &st) < 0)
126 return errno;
127
128 if (!S_ISDIR(st.st_mode))
129 return ENOTDIR;
130
131 if (st.st_uid != pwd->pw_uid && st.st_uid != 0)
132 return EACCES;
133 if ((st.st_mode & (S_IWGRP | S_IWOTH)) != 0)
134 return EACCES;
135
136 if((d = opendir(dirname)) == NULL)
137 return errno;
138
139 {
140 int fd;
141 struct stat st2;
142
143 fd = dirfd(d);
144 if(fstat(fd, &st2) < 0) {
145 closedir(d);
146 return errno;
147 }
148 if(st.st_dev != st2.st_dev || st.st_ino != st2.st_ino) {
149 closedir(d);
150 return EACCES;
151 }
152 }
153
154 while((dent = readdir(d)) != NULL) {
155 if(strcmp(dent->d_name, ".") == 0 ||
156 strcmp(dent->d_name, "..") == 0 ||
157 dent->d_name[0] == '#' || /* emacs autosave */
158 dent->d_name[strlen(dent->d_name) - 1] == '~') /* emacs backup */
159 continue;
160 snprintf(filename, sizeof(filename), "%s/%s", dirname, dent->d_name);
161 ret = check_one_file(context, filename, pwd, principal, result);
162 if(ret == 0 && *result == TRUE)
163 break;
164 ret = 0; /* don't propagate errors upstream */
165 }
166 closedir(d);
167 return ret;
168 }
169
170 #endif /* !_WIN32 */
171
172 static krb5_boolean
match_local_principals(krb5_context context,krb5_principal principal,const char * luser)173 match_local_principals(krb5_context context,
174 krb5_principal principal,
175 const char *luser)
176 {
177 krb5_error_code ret;
178 krb5_realm *realms, *r;
179 krb5_boolean result = FALSE;
180
181 /* multi-component principals can never match */
182 if(krb5_principal_get_comp_string(context, principal, 1) != NULL)
183 return FALSE;
184
185 ret = krb5_get_default_realms (context, &realms);
186 if (ret)
187 return FALSE;
188
189 for (r = realms; *r != NULL; ++r) {
190 if(strcmp(krb5_principal_get_realm(context, principal),
191 *r) != 0)
192 continue;
193 if(strcmp(krb5_principal_get_comp_string(context, principal, 0),
194 luser) == 0) {
195 result = TRUE;
196 break;
197 }
198 }
199 krb5_free_host_realm (context, realms);
200 return result;
201 }
202
203 /**
204 * This function takes the name of a local user and checks if
205 * principal is allowed to log in as that user.
206 *
207 * The user may have a ~/.k5login file listing principals that are
208 * allowed to login as that user. If that file does not exist, all
209 * principals with a first component identical to the username, and a
210 * realm considered local, are allowed access.
211 *
212 * The .k5login file must contain one principal per line, be owned by
213 * user and not be writable by group or other (but must be readable by
214 * anyone).
215 *
216 * Note that if the file exists, no implicit access rights are given
217 * to user@@LOCALREALM.
218 *
219 * Optionally, a set of files may be put in ~/.k5login.d (a
220 * directory), in which case they will all be checked in the same
221 * manner as .k5login. The files may be called anything, but files
222 * starting with a hash (#) , or ending with a tilde (~) are
223 * ignored. Subdirectories are not traversed. Note that this directory
224 * may not be checked by other Kerberos implementations.
225 *
226 * If no configuration file exists, match user against local domains,
227 * ie luser@@LOCAL-REALMS-IN-CONFIGURATION-FILES.
228 *
229 * @param context Kerberos 5 context.
230 * @param principal principal to check if allowed to login
231 * @param luser local user id
232 *
233 * @return returns TRUE if access should be granted, FALSE otherwise.
234 *
235 * @ingroup krb5_support
236 */
237
238 KRB5_LIB_FUNCTION krb5_boolean KRB5_LIB_CALL
krb5_kuserok(krb5_context context,krb5_principal principal,const char * luser)239 krb5_kuserok (krb5_context context,
240 krb5_principal principal,
241 const char *luser)
242 {
243 #ifndef _WIN32
244 char *buf;
245 size_t buflen;
246 struct passwd *pwd = NULL;
247 char *profile_dir = NULL;
248 krb5_error_code ret;
249 krb5_boolean result = FALSE;
250
251 krb5_boolean found_file = FALSE;
252
253 #ifdef POSIX_GETPWNAM_R
254 char pwbuf[2048];
255 struct passwd pw;
256
257 if(getpwnam_r(luser, &pw, pwbuf, sizeof(pwbuf), &pwd) != 0)
258 return FALSE;
259 #else
260 pwd = getpwnam (luser);
261 #endif
262 if (pwd == NULL)
263 return FALSE;
264 profile_dir = pwd->pw_dir;
265
266 #define KLOGIN "/.k5login"
267 buflen = strlen(profile_dir) + sizeof(KLOGIN) + 2; /* 2 for .d */
268 buf = malloc(buflen);
269 if(buf == NULL)
270 return FALSE;
271 /* check user's ~/.k5login */
272 strlcpy(buf, profile_dir, buflen);
273 strlcat(buf, KLOGIN, buflen);
274 ret = check_one_file(context, buf, pwd, principal, &result);
275
276 if(ret == 0 && result == TRUE) {
277 free(buf);
278 return TRUE;
279 }
280
281 if(ret != ENOENT)
282 found_file = TRUE;
283
284 strlcat(buf, ".d", buflen);
285 ret = check_directory(context, buf, pwd, principal, &result);
286 free(buf);
287 if(ret == 0 && result == TRUE)
288 return TRUE;
289
290 if(ret != ENOENT && ret != ENOTDIR)
291 found_file = TRUE;
292
293 /* finally if no files exist, allow all principals matching
294 <localuser>@<LOCALREALM> */
295 if(found_file == FALSE)
296 return match_local_principals(context, principal, luser);
297
298 return FALSE;
299 #else
300 /* The .k5login file may be on a remote profile and we don't have
301 access to the profile until we have a token handle for the
302 user's credentials. */
303 return match_local_principals(context, principal, luser);
304 #endif
305 }
306