Annotation of src/usr.bin/ssh/auth.c, Revision 1.29
1.1 markus 1: /*
1.19 deraadt 2: * Copyright (c) 2000 Markus Friedl. All rights reserved.
1.9 deraadt 3: *
4: * Redistribution and use in source and binary forms, with or without
5: * modification, are permitted provided that the following conditions
6: * are met:
7: * 1. Redistributions of source code must retain the above copyright
8: * notice, this list of conditions and the following disclaimer.
9: * 2. Redistributions in binary form must reproduce the above copyright
10: * notice, this list of conditions and the following disclaimer in the
11: * documentation and/or other materials provided with the distribution.
12: *
13: * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
14: * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
15: * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
16: * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
17: * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
18: * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
19: * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
20: * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
21: * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
22: * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
1.1 markus 23: */
24:
25: #include "includes.h"
1.29 ! markus 26: RCSID("$OpenBSD: auth.c,v 1.28 2001/10/03 10:01:20 markus Exp $");
1.22 markus 27:
28: #include <libgen.h>
1.1 markus 29:
30: #include "xmalloc.h"
1.13 markus 31: #include "match.h"
1.14 markus 32: #include "groupaccess.h"
33: #include "log.h"
1.1 markus 34: #include "servconf.h"
1.2 markus 35: #include "auth.h"
1.13 markus 36: #include "auth-options.h"
1.14 markus 37: #include "canohost.h"
1.22 markus 38: #include "buffer.h"
39: #include "bufaux.h"
1.24 markus 40: #include "uidswap.h"
41: #include "tildexpand.h"
1.2 markus 42:
1.1 markus 43: /* import */
44: extern ServerOptions options;
45:
46: /*
1.12 markus 47: * Check if the user is allowed to log in via ssh. If user is listed
48: * in DenyUsers or one of user's groups is listed in DenyGroups, false
49: * will be returned. If AllowUsers isn't empty and user isn't listed
50: * there, or if AllowGroups isn't empty and one of user's groups isn't
51: * listed there, false will be returned.
1.1 markus 52: * If the user's shell is not executable, false will be returned.
1.4 markus 53: * Otherwise true is returned.
1.1 markus 54: */
1.5 markus 55: int
1.1 markus 56: allowed_user(struct passwd * pw)
57: {
58: struct stat st;
1.26 markus 59: const char *hostname = NULL, *ipaddr = NULL;
1.21 markus 60: char *shell;
1.1 markus 61: int i;
62:
63: /* Shouldn't be called if pw is NULL, but better safe than sorry... */
1.12 markus 64: if (!pw || !pw->pw_name)
1.1 markus 65: return 0;
66:
1.7 deraadt 67: /*
68: * Get the shell from the password data. An empty shell field is
69: * legal, and means /bin/sh.
70: */
71: shell = (pw->pw_shell[0] == '\0') ? _PATH_BSHELL : pw->pw_shell;
72:
1.1 markus 73: /* deny if shell does not exists or is not executable */
1.7 deraadt 74: if (stat(shell, &st) != 0)
1.1 markus 75: return 0;
76: if (!((st.st_mode & S_IFREG) && (st.st_mode & (S_IXOTH|S_IXUSR|S_IXGRP))))
77: return 0;
78:
1.26 markus 79: if (options.num_deny_users > 0 || options.num_allow_users > 0) {
80: hostname = get_canonical_hostname(options.reverse_mapping_check);
81: ipaddr = get_remote_ipaddr();
82: }
83:
1.1 markus 84: /* Return false if user is listed in DenyUsers */
85: if (options.num_deny_users > 0) {
86: for (i = 0; i < options.num_deny_users; i++)
1.26 markus 87: if (match_user(pw->pw_name, hostname, ipaddr,
88: options.deny_users[i]))
1.1 markus 89: return 0;
90: }
91: /* Return false if AllowUsers isn't empty and user isn't listed there */
92: if (options.num_allow_users > 0) {
93: for (i = 0; i < options.num_allow_users; i++)
1.26 markus 94: if (match_user(pw->pw_name, hostname, ipaddr,
95: options.allow_users[i]))
1.1 markus 96: break;
97: /* i < options.num_allow_users iff we break for loop */
98: if (i >= options.num_allow_users)
99: return 0;
100: }
101: if (options.num_deny_groups > 0 || options.num_allow_groups > 0) {
1.12 markus 102: /* Get the user's group access list (primary and supplementary) */
103: if (ga_init(pw->pw_name, pw->pw_gid) == 0)
1.1 markus 104: return 0;
105:
1.12 markus 106: /* Return false if one of user's groups is listed in DenyGroups */
107: if (options.num_deny_groups > 0)
108: if (ga_match(options.deny_groups,
109: options.num_deny_groups)) {
110: ga_free();
1.1 markus 111: return 0;
1.12 markus 112: }
1.1 markus 113: /*
1.12 markus 114: * Return false if AllowGroups isn't empty and one of user's groups
1.1 markus 115: * isn't listed there
116: */
1.12 markus 117: if (options.num_allow_groups > 0)
118: if (!ga_match(options.allow_groups,
119: options.num_allow_groups)) {
120: ga_free();
1.1 markus 121: return 0;
1.12 markus 122: }
123: ga_free();
1.1 markus 124: }
125: /* We found no reason not to let this user try to log on... */
126: return 1;
1.13 markus 127: }
128:
129: Authctxt *
130: authctxt_new(void)
131: {
1.16 stevesk 132: Authctxt *authctxt = xmalloc(sizeof(*authctxt));
133: memset(authctxt, 0, sizeof(*authctxt));
134: return authctxt;
1.13 markus 135: }
136:
137: void
138: auth_log(Authctxt *authctxt, int authenticated, char *method, char *info)
139: {
140: void (*authlog) (const char *fmt,...) = verbose;
141: char *authmsg;
142:
143: /* Raise logging level */
144: if (authenticated == 1 ||
145: !authctxt->valid ||
146: authctxt->failures >= AUTH_FAIL_LOG ||
147: strcmp(method, "password") == 0)
148: authlog = log;
149:
150: if (authctxt->postponed)
151: authmsg = "Postponed";
152: else
153: authmsg = authenticated ? "Accepted" : "Failed";
154:
155: authlog("%s %s for %s%.100s from %.200s port %d%s",
156: authmsg,
157: method,
158: authctxt->valid ? "" : "illegal user ",
1.29 ! markus 159: authctxt->user,
1.13 markus 160: get_remote_ipaddr(),
161: get_remote_port(),
162: info);
163: }
164:
165: /*
1.17 markus 166: * Check whether root logins are disallowed.
1.13 markus 167: */
168: int
1.17 markus 169: auth_root_allowed(char *method)
1.13 markus 170: {
1.17 markus 171: switch (options.permit_root_login) {
172: case PERMIT_YES:
1.13 markus 173: return 1;
1.17 markus 174: break;
175: case PERMIT_NO_PASSWD:
176: if (strcmp(method, "password") != 0)
177: return 1;
178: break;
179: case PERMIT_FORCED_ONLY:
180: if (forced_command) {
181: log("Root login accepted for forced command.");
182: return 1;
183: }
184: break;
1.13 markus 185: }
1.17 markus 186: log("ROOT LOGIN REFUSED FROM %.200s", get_remote_ipaddr());
1.22 markus 187: return 0;
188: }
189:
190:
191: /*
192: * Given a template and a passwd structure, build a filename
193: * by substituting % tokenised options. Currently, %% becomes '%',
194: * %h becomes the home directory and %u the username.
195: *
196: * This returns a buffer allocated by xmalloc.
197: */
198: char *
199: expand_filename(const char *filename, struct passwd *pw)
200: {
201: Buffer buffer;
202: char *file;
203: const char *cp;
204:
205: /*
206: * Build the filename string in the buffer by making the appropriate
207: * substitutions to the given file name.
208: */
209: buffer_init(&buffer);
210: for (cp = filename; *cp; cp++) {
211: if (cp[0] == '%' && cp[1] == '%') {
212: buffer_append(&buffer, "%", 1);
213: cp++;
214: continue;
215: }
216: if (cp[0] == '%' && cp[1] == 'h') {
217: buffer_append(&buffer, pw->pw_dir, strlen(pw->pw_dir));
218: cp++;
219: continue;
220: }
221: if (cp[0] == '%' && cp[1] == 'u') {
222: buffer_append(&buffer, pw->pw_name,
223: strlen(pw->pw_name));
224: cp++;
225: continue;
226: }
227: buffer_append(&buffer, cp, 1);
228: }
229: buffer_append(&buffer, "\0", 1);
230:
231: /*
232: * Ensure that filename starts anchored. If not, be backward
233: * compatible and prepend the '%h/'
234: */
235: file = xmalloc(MAXPATHLEN);
236: cp = buffer_ptr(&buffer);
237: if (*cp != '/')
238: snprintf(file, MAXPATHLEN, "%s/%s", pw->pw_dir, cp);
239: else
240: strlcpy(file, cp, MAXPATHLEN);
241:
242: buffer_free(&buffer);
243: return file;
244: }
245:
246: char *
247: authorized_keys_file(struct passwd *pw)
248: {
249: return expand_filename(options.authorized_keys_file, pw);
250: }
251:
252: char *
253: authorized_keys_file2(struct passwd *pw)
254: {
255: return expand_filename(options.authorized_keys_file2, pw);
256: }
1.24 markus 257:
258: /* return ok if key exists in sysfile or userfile */
259: HostStatus
260: check_key_in_hostfiles(struct passwd *pw, Key *key, const char *host,
261: const char *sysfile, const char *userfile)
262: {
263: Key *found;
264: char *user_hostfile;
265: struct stat st;
266: int host_status;
267:
268: /* Check if we know the host and its host key. */
269: found = key_new(key->type);
270: host_status = check_host_in_hostfile(sysfile, host, key, found, NULL);
271:
272: if (host_status != HOST_OK && userfile != NULL) {
273: user_hostfile = tilde_expand_filename(userfile, pw->pw_uid);
274: if (options.strict_modes &&
275: (stat(user_hostfile, &st) == 0) &&
276: ((st.st_uid != 0 && st.st_uid != pw->pw_uid) ||
277: (st.st_mode & 022) != 0)) {
278: log("Authentication refused for %.100s: "
279: "bad owner or modes for %.200s",
280: pw->pw_name, user_hostfile);
281: } else {
282: temporarily_use_uid(pw);
283: host_status = check_host_in_hostfile(user_hostfile,
284: host, key, found, NULL);
285: restore_uid();
286: }
287: xfree(user_hostfile);
288: }
289: key_free(found);
290:
291: debug2("check_key_in_hostfiles: key %s for %s", host_status == HOST_OK ?
292: "ok" : "not found", host);
293: return host_status;
294: }
295:
1.22 markus 296:
297: /*
298: * Check a given file for security. This is defined as all components
299: * of the path to the file must either be owned by either the owner of
1.23 markus 300: * of the file or root and no directories must be group or world writable.
1.22 markus 301: *
302: * XXX Should any specific check be done for sym links ?
303: *
304: * Takes an open file descriptor, the file name, a uid and and
305: * error buffer plus max size as arguments.
306: *
307: * Returns 0 on success and -1 on failure
308: */
309: int
1.25 provos 310: secure_filename(FILE *f, const char *file, struct passwd *pw,
311: char *err, size_t errlen)
1.22 markus 312: {
1.25 provos 313: uid_t uid = pw->pw_uid;
1.28 markus 314: char buf[MAXPATHLEN], homedir[MAXPATHLEN];
1.22 markus 315: char *cp;
316: struct stat st;
317:
318: if (realpath(file, buf) == NULL) {
319: snprintf(err, errlen, "realpath %s failed: %s", file,
320: strerror(errno));
321: return -1;
322: }
1.28 markus 323: if (realpath(pw->pw_dir, homedir) == NULL) {
324: snprintf(err, errlen, "realpath %s failed: %s", pw->pw_dir,
325: strerror(errno));
326: return -1;
327: }
1.22 markus 328:
329: /* check the open file to avoid races */
330: if (fstat(fileno(f), &st) < 0 ||
331: (st.st_uid != 0 && st.st_uid != uid) ||
332: (st.st_mode & 022) != 0) {
333: snprintf(err, errlen, "bad ownership or modes for file %s",
334: buf);
335: return -1;
336: }
337:
338: /* for each component of the canonical path, walking upwards */
339: for (;;) {
340: if ((cp = dirname(buf)) == NULL) {
341: snprintf(err, errlen, "dirname() failed");
342: return -1;
343: }
344: strlcpy(buf, cp, sizeof(buf));
1.25 provos 345:
1.22 markus 346: debug3("secure_filename: checking '%s'", buf);
347: if (stat(buf, &st) < 0 ||
348: (st.st_uid != 0 && st.st_uid != uid) ||
349: (st.st_mode & 022) != 0) {
350: snprintf(err, errlen,
351: "bad ownership or modes for directory %s", buf);
352: return -1;
353: }
354:
1.27 markus 355: /* If are passed the homedir then we can stop */
1.28 markus 356: if (strcmp(homedir, buf) == 0) {
1.27 markus 357: debug3("secure_filename: terminating check at '%s'",
358: buf);
359: break;
360: }
1.22 markus 361: /*
362: * dirname should always complete with a "/" path,
363: * but we can be paranoid and check for "." too
364: */
365: if ((strcmp("/", buf) == 0) || (strcmp(".", buf) == 0))
366: break;
367: }
1.17 markus 368: return 0;
1.1 markus 369: }
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