Annotation of src/usr.bin/ssh/auth.c, Revision 1.38
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"
1.38 ! provos 26: RCSID("$OpenBSD: auth.c,v 1.37 2002/03/17 20:25:56 provos 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: }
1.36 itojun 79: if (S_ISREG(st.st_mode) == 0 ||
80: (st.st_mode & (S_IXOTH|S_IXUSR|S_IXGRP)) == 0) {
1.34 stevesk 81: log("User %.100s not allowed because shell %.100s is not executable",
82: pw->pw_name, shell);
1.1 markus 83: return 0;
1.34 stevesk 84: }
1.1 markus 85:
1.35 markus 86: if (options.num_deny_users > 0 || options.num_allow_users > 0) {
87: hostname = get_canonical_hostname(options.verify_reverse_mapping);
88: ipaddr = get_remote_ipaddr();
89: }
90:
1.1 markus 91: /* Return false if user is listed in DenyUsers */
92: if (options.num_deny_users > 0) {
93: for (i = 0; i < options.num_deny_users; i++)
1.35 markus 94: if (match_user(pw->pw_name, hostname, ipaddr,
1.34 stevesk 95: options.deny_users[i])) {
96: log("User %.100s not allowed because listed in DenyUsers",
97: pw->pw_name);
1.1 markus 98: return 0;
1.34 stevesk 99: }
1.1 markus 100: }
101: /* Return false if AllowUsers isn't empty and user isn't listed there */
102: if (options.num_allow_users > 0) {
103: for (i = 0; i < options.num_allow_users; i++)
1.35 markus 104: if (match_user(pw->pw_name, hostname, ipaddr,
1.26 markus 105: options.allow_users[i]))
1.1 markus 106: break;
107: /* i < options.num_allow_users iff we break for loop */
1.34 stevesk 108: if (i >= options.num_allow_users) {
109: log("User %.100s not allowed because not listed in AllowUsers",
110: pw->pw_name);
1.1 markus 111: return 0;
1.34 stevesk 112: }
1.1 markus 113: }
114: if (options.num_deny_groups > 0 || options.num_allow_groups > 0) {
1.12 markus 115: /* Get the user's group access list (primary and supplementary) */
1.34 stevesk 116: if (ga_init(pw->pw_name, pw->pw_gid) == 0) {
117: log("User %.100s not allowed because not in any group",
118: pw->pw_name);
1.1 markus 119: return 0;
1.34 stevesk 120: }
1.1 markus 121:
1.12 markus 122: /* Return false if one of user's groups is listed in DenyGroups */
123: if (options.num_deny_groups > 0)
124: if (ga_match(options.deny_groups,
125: options.num_deny_groups)) {
126: ga_free();
1.34 stevesk 127: log("User %.100s not allowed because a group is listed in DenyGroups",
128: pw->pw_name);
1.1 markus 129: return 0;
1.12 markus 130: }
1.1 markus 131: /*
1.12 markus 132: * Return false if AllowGroups isn't empty and one of user's groups
1.1 markus 133: * isn't listed there
134: */
1.12 markus 135: if (options.num_allow_groups > 0)
136: if (!ga_match(options.allow_groups,
137: options.num_allow_groups)) {
138: ga_free();
1.34 stevesk 139: log("User %.100s not allowed because none of user's groups are listed in AllowGroups",
140: pw->pw_name);
1.1 markus 141: return 0;
1.12 markus 142: }
143: ga_free();
1.1 markus 144: }
145: /* We found no reason not to let this user try to log on... */
146: return 1;
1.13 markus 147: }
148:
149: Authctxt *
150: authctxt_new(void)
151: {
1.16 stevesk 152: Authctxt *authctxt = xmalloc(sizeof(*authctxt));
153: memset(authctxt, 0, sizeof(*authctxt));
154: return authctxt;
1.13 markus 155: }
156:
157: void
158: auth_log(Authctxt *authctxt, int authenticated, char *method, char *info)
159: {
160: void (*authlog) (const char *fmt,...) = verbose;
161: char *authmsg;
162:
163: /* Raise logging level */
164: if (authenticated == 1 ||
165: !authctxt->valid ||
166: authctxt->failures >= AUTH_FAIL_LOG ||
167: strcmp(method, "password") == 0)
168: authlog = log;
169:
170: if (authctxt->postponed)
171: authmsg = "Postponed";
172: else
173: authmsg = authenticated ? "Accepted" : "Failed";
174:
175: authlog("%s %s for %s%.100s from %.200s port %d%s",
176: authmsg,
177: method,
178: authctxt->valid ? "" : "illegal user ",
1.29 markus 179: authctxt->user,
1.13 markus 180: get_remote_ipaddr(),
181: get_remote_port(),
182: info);
183: }
184:
185: /*
1.17 markus 186: * Check whether root logins are disallowed.
1.13 markus 187: */
188: int
1.17 markus 189: auth_root_allowed(char *method)
1.13 markus 190: {
1.17 markus 191: switch (options.permit_root_login) {
192: case PERMIT_YES:
1.13 markus 193: return 1;
1.17 markus 194: break;
195: case PERMIT_NO_PASSWD:
196: if (strcmp(method, "password") != 0)
197: return 1;
198: break;
199: case PERMIT_FORCED_ONLY:
200: if (forced_command) {
201: log("Root login accepted for forced command.");
202: return 1;
203: }
204: break;
1.13 markus 205: }
1.17 markus 206: log("ROOT LOGIN REFUSED FROM %.200s", get_remote_ipaddr());
1.22 markus 207: return 0;
208: }
209:
210:
211: /*
212: * Given a template and a passwd structure, build a filename
213: * by substituting % tokenised options. Currently, %% becomes '%',
214: * %h becomes the home directory and %u the username.
215: *
216: * This returns a buffer allocated by xmalloc.
217: */
218: char *
219: expand_filename(const char *filename, struct passwd *pw)
220: {
221: Buffer buffer;
222: char *file;
223: const char *cp;
224:
225: /*
226: * Build the filename string in the buffer by making the appropriate
227: * substitutions to the given file name.
228: */
229: buffer_init(&buffer);
230: for (cp = filename; *cp; cp++) {
231: if (cp[0] == '%' && cp[1] == '%') {
232: buffer_append(&buffer, "%", 1);
233: cp++;
234: continue;
235: }
236: if (cp[0] == '%' && cp[1] == 'h') {
237: buffer_append(&buffer, pw->pw_dir, strlen(pw->pw_dir));
238: cp++;
239: continue;
240: }
241: if (cp[0] == '%' && cp[1] == 'u') {
242: buffer_append(&buffer, pw->pw_name,
1.31 deraadt 243: strlen(pw->pw_name));
1.22 markus 244: cp++;
245: continue;
246: }
247: buffer_append(&buffer, cp, 1);
248: }
249: buffer_append(&buffer, "\0", 1);
250:
251: /*
252: * Ensure that filename starts anchored. If not, be backward
253: * compatible and prepend the '%h/'
254: */
255: file = xmalloc(MAXPATHLEN);
256: cp = buffer_ptr(&buffer);
257: if (*cp != '/')
258: snprintf(file, MAXPATHLEN, "%s/%s", pw->pw_dir, cp);
259: else
260: strlcpy(file, cp, MAXPATHLEN);
261:
262: buffer_free(&buffer);
263: return file;
264: }
265:
266: char *
267: authorized_keys_file(struct passwd *pw)
268: {
269: return expand_filename(options.authorized_keys_file, pw);
270: }
271:
272: char *
273: authorized_keys_file2(struct passwd *pw)
274: {
275: return expand_filename(options.authorized_keys_file2, pw);
276: }
1.24 markus 277:
278: /* return ok if key exists in sysfile or userfile */
279: HostStatus
280: check_key_in_hostfiles(struct passwd *pw, Key *key, const char *host,
281: const char *sysfile, const char *userfile)
282: {
283: Key *found;
284: char *user_hostfile;
285: struct stat st;
1.30 stevesk 286: HostStatus host_status;
1.24 markus 287:
288: /* Check if we know the host and its host key. */
289: found = key_new(key->type);
290: host_status = check_host_in_hostfile(sysfile, host, key, found, NULL);
291:
292: if (host_status != HOST_OK && userfile != NULL) {
293: user_hostfile = tilde_expand_filename(userfile, pw->pw_uid);
294: if (options.strict_modes &&
295: (stat(user_hostfile, &st) == 0) &&
296: ((st.st_uid != 0 && st.st_uid != pw->pw_uid) ||
1.31 deraadt 297: (st.st_mode & 022) != 0)) {
1.24 markus 298: log("Authentication refused for %.100s: "
299: "bad owner or modes for %.200s",
300: pw->pw_name, user_hostfile);
301: } else {
302: temporarily_use_uid(pw);
303: host_status = check_host_in_hostfile(user_hostfile,
304: host, key, found, NULL);
305: restore_uid();
306: }
307: xfree(user_hostfile);
308: }
309: key_free(found);
310:
311: debug2("check_key_in_hostfiles: key %s for %s", host_status == HOST_OK ?
312: "ok" : "not found", host);
313: return host_status;
314: }
315:
1.22 markus 316:
317: /*
318: * Check a given file for security. This is defined as all components
319: * of the path to the file must either be owned by either the owner of
1.23 markus 320: * of the file or root and no directories must be group or world writable.
1.22 markus 321: *
322: * XXX Should any specific check be done for sym links ?
323: *
324: * Takes an open file descriptor, the file name, a uid and and
325: * error buffer plus max size as arguments.
326: *
327: * Returns 0 on success and -1 on failure
328: */
329: int
1.25 provos 330: secure_filename(FILE *f, const char *file, struct passwd *pw,
331: char *err, size_t errlen)
1.22 markus 332: {
1.25 provos 333: uid_t uid = pw->pw_uid;
1.28 markus 334: char buf[MAXPATHLEN], homedir[MAXPATHLEN];
1.22 markus 335: char *cp;
336: struct stat st;
337:
338: if (realpath(file, buf) == NULL) {
339: snprintf(err, errlen, "realpath %s failed: %s", file,
340: strerror(errno));
341: return -1;
342: }
1.28 markus 343: if (realpath(pw->pw_dir, homedir) == NULL) {
344: snprintf(err, errlen, "realpath %s failed: %s", pw->pw_dir,
345: strerror(errno));
346: return -1;
347: }
1.22 markus 348:
349: /* check the open file to avoid races */
350: if (fstat(fileno(f), &st) < 0 ||
351: (st.st_uid != 0 && st.st_uid != uid) ||
352: (st.st_mode & 022) != 0) {
353: snprintf(err, errlen, "bad ownership or modes for file %s",
354: buf);
355: return -1;
356: }
357:
358: /* for each component of the canonical path, walking upwards */
359: for (;;) {
360: if ((cp = dirname(buf)) == NULL) {
361: snprintf(err, errlen, "dirname() failed");
362: return -1;
363: }
364: strlcpy(buf, cp, sizeof(buf));
1.25 provos 365:
1.22 markus 366: debug3("secure_filename: checking '%s'", buf);
367: if (stat(buf, &st) < 0 ||
368: (st.st_uid != 0 && st.st_uid != uid) ||
369: (st.st_mode & 022) != 0) {
1.31 deraadt 370: snprintf(err, errlen,
1.22 markus 371: "bad ownership or modes for directory %s", buf);
372: return -1;
373: }
374:
1.27 markus 375: /* If are passed the homedir then we can stop */
1.28 markus 376: if (strcmp(homedir, buf) == 0) {
1.27 markus 377: debug3("secure_filename: terminating check at '%s'",
378: buf);
379: break;
380: }
1.22 markus 381: /*
382: * dirname should always complete with a "/" path,
383: * but we can be paranoid and check for "." too
384: */
385: if ((strcmp("/", buf) == 0) || (strcmp(".", buf) == 0))
386: break;
387: }
1.17 markus 388: return 0;
1.37 provos 389: }
390:
391: struct passwd *
392: getpwnamallow(const char *user)
393: {
1.38 ! provos 394: #ifdef HAVE_LOGIN_CAP
! 395: extern login_cap_t *lc;
! 396: #ifdef BSD_AUTH
! 397: auth_session_t *as;
! 398: #endif
! 399: #endif
1.37 provos 400: struct passwd *pw;
401:
402: pw = getpwnam(user);
1.38 ! provos 403: if (pw == NULL || !allowed_user(pw))
! 404: return (NULL);
! 405: #ifdef HAVE_LOGIN_CAP
! 406: if ((lc = login_getclass(pw->pw_class)) == NULL) {
! 407: debug("unable to get login class: %s", user);
! 408: return (NULL);
! 409: }
! 410: #ifdef BSD_AUTH
! 411: if ((as = auth_open()) == NULL || auth_setpwd(as, pw) != 0 ||
! 412: auth_approval(NULL, lc, pw->pw_name, "ssh") <= 0) {
! 413: debug("Approval failure for %s", user);
1.37 provos 414: pw = NULL;
1.38 ! provos 415: }
! 416: if (as != NULL)
! 417: auth_close(as);
! 418: #endif
! 419: #endif
1.37 provos 420: return (pw);
1.1 markus 421: }
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