Annotation of src/usr.bin/ssh/auth.c, Revision 1.35
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"
1.35 ! markus 26: RCSID("$OpenBSD: auth.c,v 1.34 2002/02/28 20:56:00 stevesk 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;
1.35 ! 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 */
1.34 stevesk 74: if (stat(shell, &st) != 0) {
75: log("User %.100s not allowed because shell %.100s does not exist",
76: pw->pw_name, shell);
1.1 markus 77: return 0;
1.34 stevesk 78: }
79: if (!((st.st_mode & S_IFREG) && (st.st_mode & (S_IXOTH|S_IXUSR|S_IXGRP)))) {
80: log("User %.100s not allowed because shell %.100s is not executable",
81: pw->pw_name, shell);
1.1 markus 82: return 0;
1.34 stevesk 83: }
1.1 markus 84:
1.35 ! markus 85: if (options.num_deny_users > 0 || options.num_allow_users > 0) {
! 86: hostname = get_canonical_hostname(options.verify_reverse_mapping);
! 87: ipaddr = get_remote_ipaddr();
! 88: }
! 89:
1.1 markus 90: /* Return false if user is listed in DenyUsers */
91: if (options.num_deny_users > 0) {
92: for (i = 0; i < options.num_deny_users; i++)
1.35 ! markus 93: if (match_user(pw->pw_name, hostname, ipaddr,
1.34 stevesk 94: options.deny_users[i])) {
95: log("User %.100s not allowed because listed in DenyUsers",
96: pw->pw_name);
1.1 markus 97: return 0;
1.34 stevesk 98: }
1.1 markus 99: }
100: /* Return false if AllowUsers isn't empty and user isn't listed there */
101: if (options.num_allow_users > 0) {
102: for (i = 0; i < options.num_allow_users; i++)
1.35 ! markus 103: if (match_user(pw->pw_name, hostname, ipaddr,
1.26 markus 104: options.allow_users[i]))
1.1 markus 105: break;
106: /* i < options.num_allow_users iff we break for loop */
1.34 stevesk 107: if (i >= options.num_allow_users) {
108: log("User %.100s not allowed because not listed in AllowUsers",
109: pw->pw_name);
1.1 markus 110: return 0;
1.34 stevesk 111: }
1.1 markus 112: }
113: if (options.num_deny_groups > 0 || options.num_allow_groups > 0) {
1.12 markus 114: /* Get the user's group access list (primary and supplementary) */
1.34 stevesk 115: if (ga_init(pw->pw_name, pw->pw_gid) == 0) {
116: log("User %.100s not allowed because not in any group",
117: pw->pw_name);
1.1 markus 118: return 0;
1.34 stevesk 119: }
1.1 markus 120:
1.12 markus 121: /* Return false if one of user's groups is listed in DenyGroups */
122: if (options.num_deny_groups > 0)
123: if (ga_match(options.deny_groups,
124: options.num_deny_groups)) {
125: ga_free();
1.34 stevesk 126: log("User %.100s not allowed because a group is listed in DenyGroups",
127: pw->pw_name);
1.1 markus 128: return 0;
1.12 markus 129: }
1.1 markus 130: /*
1.12 markus 131: * Return false if AllowGroups isn't empty and one of user's groups
1.1 markus 132: * isn't listed there
133: */
1.12 markus 134: if (options.num_allow_groups > 0)
135: if (!ga_match(options.allow_groups,
136: options.num_allow_groups)) {
137: ga_free();
1.34 stevesk 138: log("User %.100s not allowed because none of user's groups are listed in AllowGroups",
139: pw->pw_name);
1.1 markus 140: return 0;
1.12 markus 141: }
142: ga_free();
1.1 markus 143: }
144: /* We found no reason not to let this user try to log on... */
145: return 1;
1.13 markus 146: }
147:
148: Authctxt *
149: authctxt_new(void)
150: {
1.16 stevesk 151: Authctxt *authctxt = xmalloc(sizeof(*authctxt));
152: memset(authctxt, 0, sizeof(*authctxt));
153: return authctxt;
1.13 markus 154: }
155:
156: void
157: auth_log(Authctxt *authctxt, int authenticated, char *method, char *info)
158: {
159: void (*authlog) (const char *fmt,...) = verbose;
160: char *authmsg;
161:
162: /* Raise logging level */
163: if (authenticated == 1 ||
164: !authctxt->valid ||
165: authctxt->failures >= AUTH_FAIL_LOG ||
166: strcmp(method, "password") == 0)
167: authlog = log;
168:
169: if (authctxt->postponed)
170: authmsg = "Postponed";
171: else
172: authmsg = authenticated ? "Accepted" : "Failed";
173:
174: authlog("%s %s for %s%.100s from %.200s port %d%s",
175: authmsg,
176: method,
177: authctxt->valid ? "" : "illegal user ",
1.29 markus 178: authctxt->user,
1.13 markus 179: get_remote_ipaddr(),
180: get_remote_port(),
181: info);
182: }
183:
184: /*
1.17 markus 185: * Check whether root logins are disallowed.
1.13 markus 186: */
187: int
1.17 markus 188: auth_root_allowed(char *method)
1.13 markus 189: {
1.17 markus 190: switch (options.permit_root_login) {
191: case PERMIT_YES:
1.13 markus 192: return 1;
1.17 markus 193: break;
194: case PERMIT_NO_PASSWD:
195: if (strcmp(method, "password") != 0)
196: return 1;
197: break;
198: case PERMIT_FORCED_ONLY:
199: if (forced_command) {
200: log("Root login accepted for forced command.");
201: return 1;
202: }
203: break;
1.13 markus 204: }
1.17 markus 205: log("ROOT LOGIN REFUSED FROM %.200s", get_remote_ipaddr());
1.22 markus 206: return 0;
207: }
208:
209:
210: /*
211: * Given a template and a passwd structure, build a filename
212: * by substituting % tokenised options. Currently, %% becomes '%',
213: * %h becomes the home directory and %u the username.
214: *
215: * This returns a buffer allocated by xmalloc.
216: */
217: char *
218: expand_filename(const char *filename, struct passwd *pw)
219: {
220: Buffer buffer;
221: char *file;
222: const char *cp;
223:
224: /*
225: * Build the filename string in the buffer by making the appropriate
226: * substitutions to the given file name.
227: */
228: buffer_init(&buffer);
229: for (cp = filename; *cp; cp++) {
230: if (cp[0] == '%' && cp[1] == '%') {
231: buffer_append(&buffer, "%", 1);
232: cp++;
233: continue;
234: }
235: if (cp[0] == '%' && cp[1] == 'h') {
236: buffer_append(&buffer, pw->pw_dir, strlen(pw->pw_dir));
237: cp++;
238: continue;
239: }
240: if (cp[0] == '%' && cp[1] == 'u') {
241: buffer_append(&buffer, pw->pw_name,
1.31 deraadt 242: strlen(pw->pw_name));
1.22 markus 243: cp++;
244: continue;
245: }
246: buffer_append(&buffer, cp, 1);
247: }
248: buffer_append(&buffer, "\0", 1);
249:
250: /*
251: * Ensure that filename starts anchored. If not, be backward
252: * compatible and prepend the '%h/'
253: */
254: file = xmalloc(MAXPATHLEN);
255: cp = buffer_ptr(&buffer);
256: if (*cp != '/')
257: snprintf(file, MAXPATHLEN, "%s/%s", pw->pw_dir, cp);
258: else
259: strlcpy(file, cp, MAXPATHLEN);
260:
261: buffer_free(&buffer);
262: return file;
263: }
264:
265: char *
266: authorized_keys_file(struct passwd *pw)
267: {
268: return expand_filename(options.authorized_keys_file, pw);
269: }
270:
271: char *
272: authorized_keys_file2(struct passwd *pw)
273: {
274: return expand_filename(options.authorized_keys_file2, pw);
275: }
1.24 markus 276:
277: /* return ok if key exists in sysfile or userfile */
278: HostStatus
279: check_key_in_hostfiles(struct passwd *pw, Key *key, const char *host,
280: const char *sysfile, const char *userfile)
281: {
282: Key *found;
283: char *user_hostfile;
284: struct stat st;
1.30 stevesk 285: HostStatus host_status;
1.24 markus 286:
287: /* Check if we know the host and its host key. */
288: found = key_new(key->type);
289: host_status = check_host_in_hostfile(sysfile, host, key, found, NULL);
290:
291: if (host_status != HOST_OK && userfile != NULL) {
292: user_hostfile = tilde_expand_filename(userfile, pw->pw_uid);
293: if (options.strict_modes &&
294: (stat(user_hostfile, &st) == 0) &&
295: ((st.st_uid != 0 && st.st_uid != pw->pw_uid) ||
1.31 deraadt 296: (st.st_mode & 022) != 0)) {
1.24 markus 297: log("Authentication refused for %.100s: "
298: "bad owner or modes for %.200s",
299: pw->pw_name, user_hostfile);
300: } else {
301: temporarily_use_uid(pw);
302: host_status = check_host_in_hostfile(user_hostfile,
303: host, key, found, NULL);
304: restore_uid();
305: }
306: xfree(user_hostfile);
307: }
308: key_free(found);
309:
310: debug2("check_key_in_hostfiles: key %s for %s", host_status == HOST_OK ?
311: "ok" : "not found", host);
312: return host_status;
313: }
314:
1.22 markus 315:
316: /*
317: * Check a given file for security. This is defined as all components
318: * of the path to the file must either be owned by either the owner of
1.23 markus 319: * of the file or root and no directories must be group or world writable.
1.22 markus 320: *
321: * XXX Should any specific check be done for sym links ?
322: *
323: * Takes an open file descriptor, the file name, a uid and and
324: * error buffer plus max size as arguments.
325: *
326: * Returns 0 on success and -1 on failure
327: */
328: int
1.25 provos 329: secure_filename(FILE *f, const char *file, struct passwd *pw,
330: char *err, size_t errlen)
1.22 markus 331: {
1.25 provos 332: uid_t uid = pw->pw_uid;
1.28 markus 333: char buf[MAXPATHLEN], homedir[MAXPATHLEN];
1.22 markus 334: char *cp;
335: struct stat st;
336:
337: if (realpath(file, buf) == NULL) {
338: snprintf(err, errlen, "realpath %s failed: %s", file,
339: strerror(errno));
340: return -1;
341: }
1.28 markus 342: if (realpath(pw->pw_dir, homedir) == NULL) {
343: snprintf(err, errlen, "realpath %s failed: %s", pw->pw_dir,
344: strerror(errno));
345: return -1;
346: }
1.22 markus 347:
348: /* check the open file to avoid races */
349: if (fstat(fileno(f), &st) < 0 ||
350: (st.st_uid != 0 && st.st_uid != uid) ||
351: (st.st_mode & 022) != 0) {
352: snprintf(err, errlen, "bad ownership or modes for file %s",
353: buf);
354: return -1;
355: }
356:
357: /* for each component of the canonical path, walking upwards */
358: for (;;) {
359: if ((cp = dirname(buf)) == NULL) {
360: snprintf(err, errlen, "dirname() failed");
361: return -1;
362: }
363: strlcpy(buf, cp, sizeof(buf));
1.25 provos 364:
1.22 markus 365: debug3("secure_filename: checking '%s'", buf);
366: if (stat(buf, &st) < 0 ||
367: (st.st_uid != 0 && st.st_uid != uid) ||
368: (st.st_mode & 022) != 0) {
1.31 deraadt 369: snprintf(err, errlen,
1.22 markus 370: "bad ownership or modes for directory %s", buf);
371: return -1;
372: }
373:
1.27 markus 374: /* If are passed the homedir then we can stop */
1.28 markus 375: if (strcmp(homedir, buf) == 0) {
1.27 markus 376: debug3("secure_filename: terminating check at '%s'",
377: buf);
378: break;
379: }
1.22 markus 380: /*
381: * dirname should always complete with a "/" path,
382: * but we can be paranoid and check for "." too
383: */
384: if ((strcmp("/", buf) == 0) || (strcmp(".", buf) == 0))
385: break;
386: }
1.17 markus 387: return 0;
1.1 markus 388: }
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