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
42static krb5_error_code
43check_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
108static krb5_error_code
109check_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
170static krb5_boolean
171match_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
201static krb5_error_code
202check_unix(krb5_context context,
203	   krb5_principal principal,
204	   const char *luser)
205{
206    char *buf;
207    size_t buflen;
208    struct passwd *pwd = NULL;
209    char *profile_dir = NULL;
210    krb5_error_code ret;
211    krb5_boolean result = FALSE;
212
213    krb5_boolean found_file = FALSE;
214
215#ifdef POSIX_GETPWNAM_R
216    char pwbuf[2048];
217    struct passwd pw;
218
219    if(getpwnam_r(luser, &pw, pwbuf, sizeof(pwbuf), &pwd) != 0)
220	return FALSE;
221#else
222    pwd = getpwnam (luser);
223#endif
224    if (pwd == NULL)
225	return FALSE;
226    profile_dir = pwd->pw_dir;
227
228#define KLOGIN "/.k5login"
229    buflen = strlen(profile_dir) + sizeof(KLOGIN) + 2; /* 2 for .d */
230    buf = malloc(buflen);
231    if(buf == NULL)
232	return FALSE;
233    /* check user's ~/.k5login */
234    strlcpy(buf, profile_dir, buflen);
235    strlcat(buf, KLOGIN, buflen);
236    ret = check_one_file(context, buf, pwd, principal, &result);
237
238    if(ret == 0 && result == TRUE) {
239	free(buf);
240	return TRUE;
241    }
242
243    if(ret != ENOENT)
244	found_file = TRUE;
245
246    strlcat(buf, ".d", buflen);
247    ret = check_directory(context, buf, pwd, principal, &result);
248    free(buf);
249    if(ret == 0 && result == TRUE)
250	return TRUE;
251
252    if(ret != ENOENT && ret != ENOTDIR)
253	found_file = TRUE;
254
255    /* finally if no files exist, allow all principals matching
256       <localuser>@<LOCALREALM> */
257    if(found_file == FALSE)
258	return match_local_principals(context, principal, luser);
259
260    return FALSE;
261}
262
263#ifdef __APPLE__
264#include <membership.h>
265
266static krb5_error_code
267check_od(krb5_context context,
268	 krb5_principal principal,
269	 const char *luser)
270{
271    krb5_boolean match = FALSE;
272    uuid_t krb_uuid, un_uuid;
273    char *kprinc = NULL;
274    int ret = 0;
275
276    ret = krb5_unparse_name(context, principal, &kprinc);
277    if (ret)
278	goto out;
279
280    ret = mbr_identifier_to_uuid(ID_TYPE_USERNAME, luser, strlen(luser), un_uuid);
281    if (!ret)
282	goto out;
283
284    ret = mbr_identifier_to_uuid(ID_TYPE_KERBEROS, kprinc, strlen(kprinc), krb_uuid);
285    if (!ret)
286	goto out;
287
288    ret = uuid_compare(krb_uuid, un_uuid);
289    if (0 == ret)
290	match = TRUE;
291
292 out:
293    if (kprinc)
294	free(kprinc);
295
296    return match;
297}
298#endif
299
300/**
301 * This function takes the name of a local user and checks if
302 * principal is allowed to log in as that user.
303 *
304 * The user may have a ~/.k5login file listing principals that are
305 * allowed to login as that user. If that file does not exist, all
306 * principals with a first component identical to the username, and a
307 * realm considered local, are allowed access.
308 *
309 * The .k5login file must contain one principal per line, be owned by
310 * user and not be writable by group or other (but must be readable by
311 * anyone).
312 *
313 * Note that if the file exists, no implicit access rights are given
314 * to user@@LOCALREALM.
315 *
316 * Optionally, a set of files may be put in ~/.k5login.d (a
317 * directory), in which case they will all be checked in the same
318 * manner as .k5login.  The files may be called anything, but files
319 * starting with a hash (#) , or ending with a tilde (~) are
320 * ignored. Subdirectories are not traversed. Note that this directory
321 * may not be checked by other Kerberos implementations.
322 *
323 * If no configuration file exists, match user against local domains,
324 * ie luser@@LOCAL-REALMS-IN-CONFIGURATION-FILES.
325 *
326 * @param context Kerberos 5 context.
327 * @param principal principal to check if allowed to login
328 * @param luser local user id
329 *
330 * @return returns TRUE if access should be granted, FALSE otherwise.
331 *
332 * @ingroup krb5_support
333 */
334
335KRB5_LIB_FUNCTION krb5_boolean KRB5_LIB_CALL
336krb5_kuserok (krb5_context context,
337	      krb5_principal principal,
338	      const char *luser)
339{
340    krb5_boolean match;
341
342#ifndef _WIN32
343    match = check_unix(context, principal, luser);
344#else
345    /* The .k5login file may be on a remote profile and we don't have
346       access to the profile until we have a token handle for the
347       user's credentials. */
348    match = match_local_principals(context, principal, luser);
349#endif
350
351#ifdef __APPLE__
352    if (!match)
353	match = check_od(context, principal, luser);
354#endif
355    return match;
356}
357