Annotation of src/usr.bin/ssh/auth.c, Revision 1.41.2.1
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"
1.41.2.1! jason 26: RCSID("$OpenBSD: auth.c,v 1.42 2002/05/13 20:44:58 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"
1.40 markus 42: #include "misc.h"
1.41.2.1! jason 43: #include "bufaux.h"
! 44: #include "packet.h"
1.2 markus 45:
1.1 markus 46: /* import */
47: extern ServerOptions options;
48:
1.41.2.1! jason 49: /* Debugging messages */
! 50: Buffer auth_debug;
! 51: int auth_debug_init;
! 52:
1.1 markus 53: /*
1.12 markus 54: * Check if the user is allowed to log in via ssh. If user is listed
55: * in DenyUsers or one of user's groups is listed in DenyGroups, false
56: * will be returned. If AllowUsers isn't empty and user isn't listed
57: * there, or if AllowGroups isn't empty and one of user's groups isn't
58: * listed there, false will be returned.
1.1 markus 59: * If the user's shell is not executable, false will be returned.
1.4 markus 60: * Otherwise true is returned.
1.1 markus 61: */
1.5 markus 62: int
1.1 markus 63: allowed_user(struct passwd * pw)
64: {
65: struct stat st;
1.35 markus 66: const char *hostname = NULL, *ipaddr = NULL;
1.21 markus 67: char *shell;
1.1 markus 68: int i;
69:
70: /* Shouldn't be called if pw is NULL, but better safe than sorry... */
1.12 markus 71: if (!pw || !pw->pw_name)
1.1 markus 72: return 0;
73:
1.7 deraadt 74: /*
75: * Get the shell from the password data. An empty shell field is
76: * legal, and means /bin/sh.
77: */
78: shell = (pw->pw_shell[0] == '\0') ? _PATH_BSHELL : pw->pw_shell;
79:
1.1 markus 80: /* deny if shell does not exists or is not executable */
1.34 stevesk 81: if (stat(shell, &st) != 0) {
82: log("User %.100s not allowed because shell %.100s does not exist",
83: pw->pw_name, shell);
1.1 markus 84: return 0;
1.34 stevesk 85: }
1.36 itojun 86: if (S_ISREG(st.st_mode) == 0 ||
87: (st.st_mode & (S_IXOTH|S_IXUSR|S_IXGRP)) == 0) {
1.34 stevesk 88: log("User %.100s not allowed because shell %.100s is not executable",
89: pw->pw_name, shell);
1.1 markus 90: return 0;
1.34 stevesk 91: }
1.1 markus 92:
1.35 markus 93: if (options.num_deny_users > 0 || options.num_allow_users > 0) {
94: hostname = get_canonical_hostname(options.verify_reverse_mapping);
95: ipaddr = get_remote_ipaddr();
96: }
97:
1.1 markus 98: /* Return false if user is listed in DenyUsers */
99: if (options.num_deny_users > 0) {
100: for (i = 0; i < options.num_deny_users; i++)
1.39 markus 101: if (match_user(pw->pw_name, hostname, ipaddr,
1.34 stevesk 102: options.deny_users[i])) {
1.39 markus 103: log("User %.100s not allowed because listed in DenyUsers",
104: pw->pw_name);
1.1 markus 105: return 0;
1.34 stevesk 106: }
1.1 markus 107: }
108: /* Return false if AllowUsers isn't empty and user isn't listed there */
109: if (options.num_allow_users > 0) {
110: for (i = 0; i < options.num_allow_users; i++)
1.39 markus 111: if (match_user(pw->pw_name, hostname, ipaddr,
1.26 markus 112: options.allow_users[i]))
1.1 markus 113: break;
114: /* i < options.num_allow_users iff we break for loop */
1.34 stevesk 115: if (i >= options.num_allow_users) {
116: log("User %.100s not allowed because not listed in AllowUsers",
117: pw->pw_name);
1.1 markus 118: return 0;
1.34 stevesk 119: }
1.1 markus 120: }
121: if (options.num_deny_groups > 0 || options.num_allow_groups > 0) {
1.12 markus 122: /* Get the user's group access list (primary and supplementary) */
1.34 stevesk 123: if (ga_init(pw->pw_name, pw->pw_gid) == 0) {
124: log("User %.100s not allowed because not in any group",
125: pw->pw_name);
1.1 markus 126: return 0;
1.34 stevesk 127: }
1.1 markus 128:
1.12 markus 129: /* Return false if one of user's groups is listed in DenyGroups */
130: if (options.num_deny_groups > 0)
131: if (ga_match(options.deny_groups,
132: options.num_deny_groups)) {
133: ga_free();
1.34 stevesk 134: log("User %.100s not allowed because a group is listed in DenyGroups",
135: pw->pw_name);
1.1 markus 136: return 0;
1.12 markus 137: }
1.1 markus 138: /*
1.12 markus 139: * Return false if AllowGroups isn't empty and one of user's groups
1.1 markus 140: * isn't listed there
141: */
1.12 markus 142: if (options.num_allow_groups > 0)
143: if (!ga_match(options.allow_groups,
144: options.num_allow_groups)) {
145: ga_free();
1.34 stevesk 146: log("User %.100s not allowed because none of user's groups are listed in AllowGroups",
147: pw->pw_name);
1.1 markus 148: return 0;
1.12 markus 149: }
150: ga_free();
1.1 markus 151: }
152: /* We found no reason not to let this user try to log on... */
153: return 1;
1.13 markus 154: }
155:
156: Authctxt *
157: authctxt_new(void)
158: {
1.16 stevesk 159: Authctxt *authctxt = xmalloc(sizeof(*authctxt));
160: memset(authctxt, 0, sizeof(*authctxt));
161: return authctxt;
1.13 markus 162: }
163:
164: void
165: auth_log(Authctxt *authctxt, int authenticated, char *method, char *info)
166: {
167: void (*authlog) (const char *fmt,...) = verbose;
168: char *authmsg;
169:
170: /* Raise logging level */
171: if (authenticated == 1 ||
172: !authctxt->valid ||
173: authctxt->failures >= AUTH_FAIL_LOG ||
174: strcmp(method, "password") == 0)
175: authlog = log;
176:
177: if (authctxt->postponed)
178: authmsg = "Postponed";
179: else
180: authmsg = authenticated ? "Accepted" : "Failed";
181:
182: authlog("%s %s for %s%.100s from %.200s port %d%s",
183: authmsg,
184: method,
185: authctxt->valid ? "" : "illegal user ",
1.29 markus 186: authctxt->user,
1.13 markus 187: get_remote_ipaddr(),
188: get_remote_port(),
189: info);
190: }
191:
192: /*
1.17 markus 193: * Check whether root logins are disallowed.
1.13 markus 194: */
195: int
1.17 markus 196: auth_root_allowed(char *method)
1.13 markus 197: {
1.17 markus 198: switch (options.permit_root_login) {
199: case PERMIT_YES:
1.13 markus 200: return 1;
1.17 markus 201: break;
202: case PERMIT_NO_PASSWD:
203: if (strcmp(method, "password") != 0)
204: return 1;
205: break;
206: case PERMIT_FORCED_ONLY:
207: if (forced_command) {
208: log("Root login accepted for forced command.");
209: return 1;
210: }
211: break;
1.13 markus 212: }
1.17 markus 213: log("ROOT LOGIN REFUSED FROM %.200s", get_remote_ipaddr());
1.22 markus 214: return 0;
215: }
216:
217:
218: /*
219: * Given a template and a passwd structure, build a filename
220: * by substituting % tokenised options. Currently, %% becomes '%',
221: * %h becomes the home directory and %u the username.
222: *
223: * This returns a buffer allocated by xmalloc.
224: */
225: char *
226: expand_filename(const char *filename, struct passwd *pw)
227: {
228: Buffer buffer;
229: char *file;
230: const char *cp;
231:
232: /*
233: * Build the filename string in the buffer by making the appropriate
234: * substitutions to the given file name.
235: */
236: buffer_init(&buffer);
237: for (cp = filename; *cp; cp++) {
238: if (cp[0] == '%' && cp[1] == '%') {
239: buffer_append(&buffer, "%", 1);
240: cp++;
241: continue;
242: }
243: if (cp[0] == '%' && cp[1] == 'h') {
244: buffer_append(&buffer, pw->pw_dir, strlen(pw->pw_dir));
245: cp++;
246: continue;
247: }
248: if (cp[0] == '%' && cp[1] == 'u') {
249: buffer_append(&buffer, pw->pw_name,
1.31 deraadt 250: strlen(pw->pw_name));
1.22 markus 251: cp++;
252: continue;
253: }
254: buffer_append(&buffer, cp, 1);
255: }
256: buffer_append(&buffer, "\0", 1);
257:
258: /*
259: * Ensure that filename starts anchored. If not, be backward
260: * compatible and prepend the '%h/'
261: */
262: file = xmalloc(MAXPATHLEN);
263: cp = buffer_ptr(&buffer);
264: if (*cp != '/')
265: snprintf(file, MAXPATHLEN, "%s/%s", pw->pw_dir, cp);
266: else
267: strlcpy(file, cp, MAXPATHLEN);
268:
269: buffer_free(&buffer);
270: return file;
271: }
272:
273: char *
274: authorized_keys_file(struct passwd *pw)
275: {
276: return expand_filename(options.authorized_keys_file, pw);
277: }
278:
279: char *
280: authorized_keys_file2(struct passwd *pw)
281: {
282: return expand_filename(options.authorized_keys_file2, pw);
283: }
1.24 markus 284:
285: /* return ok if key exists in sysfile or userfile */
286: HostStatus
287: check_key_in_hostfiles(struct passwd *pw, Key *key, const char *host,
288: const char *sysfile, const char *userfile)
289: {
290: Key *found;
291: char *user_hostfile;
292: struct stat st;
1.30 stevesk 293: HostStatus host_status;
1.24 markus 294:
295: /* Check if we know the host and its host key. */
296: found = key_new(key->type);
297: host_status = check_host_in_hostfile(sysfile, host, key, found, NULL);
298:
299: if (host_status != HOST_OK && userfile != NULL) {
300: user_hostfile = tilde_expand_filename(userfile, pw->pw_uid);
301: if (options.strict_modes &&
302: (stat(user_hostfile, &st) == 0) &&
303: ((st.st_uid != 0 && st.st_uid != pw->pw_uid) ||
1.31 deraadt 304: (st.st_mode & 022) != 0)) {
1.24 markus 305: log("Authentication refused for %.100s: "
306: "bad owner or modes for %.200s",
307: pw->pw_name, user_hostfile);
308: } else {
309: temporarily_use_uid(pw);
310: host_status = check_host_in_hostfile(user_hostfile,
311: host, key, found, NULL);
312: restore_uid();
313: }
314: xfree(user_hostfile);
315: }
316: key_free(found);
317:
318: debug2("check_key_in_hostfiles: key %s for %s", host_status == HOST_OK ?
319: "ok" : "not found", host);
320: return host_status;
321: }
322:
1.22 markus 323:
324: /*
325: * Check a given file for security. This is defined as all components
326: * of the path to the file must either be owned by either the owner of
1.23 markus 327: * of the file or root and no directories must be group or world writable.
1.22 markus 328: *
329: * XXX Should any specific check be done for sym links ?
330: *
331: * Takes an open file descriptor, the file name, a uid and and
332: * error buffer plus max size as arguments.
333: *
334: * Returns 0 on success and -1 on failure
335: */
336: int
1.25 provos 337: secure_filename(FILE *f, const char *file, struct passwd *pw,
338: char *err, size_t errlen)
1.22 markus 339: {
1.25 provos 340: uid_t uid = pw->pw_uid;
1.28 markus 341: char buf[MAXPATHLEN], homedir[MAXPATHLEN];
1.22 markus 342: char *cp;
343: struct stat st;
344:
345: if (realpath(file, buf) == NULL) {
346: snprintf(err, errlen, "realpath %s failed: %s", file,
347: strerror(errno));
348: return -1;
349: }
1.28 markus 350: if (realpath(pw->pw_dir, homedir) == NULL) {
351: snprintf(err, errlen, "realpath %s failed: %s", pw->pw_dir,
352: strerror(errno));
353: return -1;
354: }
1.22 markus 355:
356: /* check the open file to avoid races */
357: if (fstat(fileno(f), &st) < 0 ||
358: (st.st_uid != 0 && st.st_uid != uid) ||
359: (st.st_mode & 022) != 0) {
360: snprintf(err, errlen, "bad ownership or modes for file %s",
361: buf);
362: return -1;
363: }
364:
365: /* for each component of the canonical path, walking upwards */
366: for (;;) {
367: if ((cp = dirname(buf)) == NULL) {
368: snprintf(err, errlen, "dirname() failed");
369: return -1;
370: }
371: strlcpy(buf, cp, sizeof(buf));
1.25 provos 372:
1.22 markus 373: debug3("secure_filename: checking '%s'", buf);
374: if (stat(buf, &st) < 0 ||
375: (st.st_uid != 0 && st.st_uid != uid) ||
376: (st.st_mode & 022) != 0) {
1.31 deraadt 377: snprintf(err, errlen,
1.22 markus 378: "bad ownership or modes for directory %s", buf);
379: return -1;
380: }
381:
1.27 markus 382: /* If are passed the homedir then we can stop */
1.28 markus 383: if (strcmp(homedir, buf) == 0) {
1.27 markus 384: debug3("secure_filename: terminating check at '%s'",
385: buf);
386: break;
387: }
1.22 markus 388: /*
389: * dirname should always complete with a "/" path,
390: * but we can be paranoid and check for "." too
391: */
392: if ((strcmp("/", buf) == 0) || (strcmp(".", buf) == 0))
393: break;
394: }
1.17 markus 395: return 0;
1.37 provos 396: }
397:
398: struct passwd *
399: getpwnamallow(const char *user)
400: {
1.38 provos 401: #ifdef HAVE_LOGIN_CAP
402: extern login_cap_t *lc;
403: #ifdef BSD_AUTH
404: auth_session_t *as;
405: #endif
406: #endif
1.37 provos 407: struct passwd *pw;
408:
409: pw = getpwnam(user);
1.38 provos 410: if (pw == NULL || !allowed_user(pw))
411: return (NULL);
412: #ifdef HAVE_LOGIN_CAP
413: if ((lc = login_getclass(pw->pw_class)) == NULL) {
414: debug("unable to get login class: %s", user);
415: return (NULL);
416: }
417: #ifdef BSD_AUTH
418: if ((as = auth_open()) == NULL || auth_setpwd(as, pw) != 0 ||
419: auth_approval(NULL, lc, pw->pw_name, "ssh") <= 0) {
420: debug("Approval failure for %s", user);
1.37 provos 421: pw = NULL;
1.38 provos 422: }
423: if (as != NULL)
424: auth_close(as);
425: #endif
426: #endif
1.41 markus 427: if (pw != NULL)
428: return (pwcopy(pw));
429: return (NULL);
1.41.2.1! jason 430: }
! 431:
! 432: void
! 433: auth_debug_add(const char *fmt,...)
! 434: {
! 435: char buf[1024];
! 436: va_list args;
! 437:
! 438: if (!auth_debug_init)
! 439: return;
! 440:
! 441: va_start(args, fmt);
! 442: vsnprintf(buf, sizeof(buf), fmt, args);
! 443: va_end(args);
! 444: buffer_put_cstring(&auth_debug, buf);
! 445: }
! 446:
! 447: void
! 448: auth_debug_send(void)
! 449: {
! 450: char *msg;
! 451:
! 452: if (!auth_debug_init)
! 453: return;
! 454: while (buffer_len(&auth_debug)) {
! 455: msg = buffer_get_string(&auth_debug, NULL);
! 456: packet_send_debug("%s", msg);
! 457: xfree(msg);
! 458: }
! 459: }
! 460:
! 461: void
! 462: auth_debug_reset(void)
! 463: {
! 464: if (auth_debug_init)
! 465: buffer_clear(&auth_debug);
! 466: else {
! 467: buffer_init(&auth_debug);
! 468: auth_debug_init = 1;
! 469: }
1.1 markus 470: }
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