Annotation of src/usr.bin/ssh/auth.c, Revision 1.64
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"
1.62 stevesk 26:
27: #include <sys/types.h>
28: #include <sys/stat.h>
1.22 markus 29:
30: #include <libgen.h>
1.61 stevesk 31: #include <paths.h>
1.1 markus 32:
33: #include "xmalloc.h"
1.13 markus 34: #include "match.h"
1.14 markus 35: #include "groupaccess.h"
36: #include "log.h"
1.1 markus 37: #include "servconf.h"
1.2 markus 38: #include "auth.h"
1.13 markus 39: #include "auth-options.h"
1.14 markus 40: #include "canohost.h"
1.22 markus 41: #include "buffer.h"
42: #include "bufaux.h"
1.24 markus 43: #include "uidswap.h"
1.40 markus 44: #include "misc.h"
1.42 markus 45: #include "bufaux.h"
46: #include "packet.h"
1.2 markus 47:
1.1 markus 48: /* import */
49: extern ServerOptions options;
50:
1.42 markus 51: /* Debugging messages */
52: Buffer auth_debug;
53: int auth_debug_init;
54:
1.1 markus 55: /*
1.12 markus 56: * Check if the user is allowed to log in via ssh. If user is listed
57: * in DenyUsers or one of user's groups is listed in DenyGroups, false
58: * will be returned. If AllowUsers isn't empty and user isn't listed
59: * there, or if AllowGroups isn't empty and one of user's groups isn't
60: * listed there, false will be returned.
1.1 markus 61: * If the user's shell is not executable, false will be returned.
1.4 markus 62: * Otherwise true is returned.
1.1 markus 63: */
1.5 markus 64: int
1.1 markus 65: allowed_user(struct passwd * pw)
66: {
67: struct stat st;
1.35 markus 68: const char *hostname = NULL, *ipaddr = NULL;
1.21 markus 69: char *shell;
1.60 djm 70: u_int i;
1.1 markus 71:
72: /* Shouldn't be called if pw is NULL, but better safe than sorry... */
1.12 markus 73: if (!pw || !pw->pw_name)
1.1 markus 74: return 0;
75:
1.7 deraadt 76: /*
77: * Get the shell from the password data. An empty shell field is
78: * legal, and means /bin/sh.
79: */
80: shell = (pw->pw_shell[0] == '\0') ? _PATH_BSHELL : pw->pw_shell;
81:
1.1 markus 82: /* deny if shell does not exists or is not executable */
1.34 stevesk 83: if (stat(shell, &st) != 0) {
1.47 itojun 84: logit("User %.100s not allowed because shell %.100s does not exist",
1.34 stevesk 85: pw->pw_name, shell);
1.1 markus 86: return 0;
1.34 stevesk 87: }
1.36 itojun 88: if (S_ISREG(st.st_mode) == 0 ||
89: (st.st_mode & (S_IXOTH|S_IXUSR|S_IXGRP)) == 0) {
1.47 itojun 90: logit("User %.100s not allowed because shell %.100s is not executable",
1.34 stevesk 91: pw->pw_name, shell);
1.1 markus 92: return 0;
1.34 stevesk 93: }
1.1 markus 94:
1.58 dtucker 95: if (options.num_deny_users > 0 || options.num_allow_users > 0 ||
96: options.num_deny_groups > 0 || options.num_allow_groups > 0) {
1.48 markus 97: hostname = get_canonical_hostname(options.use_dns);
1.35 markus 98: ipaddr = get_remote_ipaddr();
99: }
100:
1.1 markus 101: /* Return false if user is listed in DenyUsers */
102: if (options.num_deny_users > 0) {
103: for (i = 0; i < options.num_deny_users; i++)
1.39 markus 104: if (match_user(pw->pw_name, hostname, ipaddr,
1.34 stevesk 105: options.deny_users[i])) {
1.57 dtucker 106: logit("User %.100s from %.100s not allowed "
107: "because listed in DenyUsers",
108: pw->pw_name, hostname);
1.1 markus 109: return 0;
1.34 stevesk 110: }
1.1 markus 111: }
112: /* Return false if AllowUsers isn't empty and user isn't listed there */
113: if (options.num_allow_users > 0) {
114: for (i = 0; i < options.num_allow_users; i++)
1.39 markus 115: if (match_user(pw->pw_name, hostname, ipaddr,
1.26 markus 116: options.allow_users[i]))
1.1 markus 117: break;
118: /* i < options.num_allow_users iff we break for loop */
1.34 stevesk 119: if (i >= options.num_allow_users) {
1.57 dtucker 120: logit("User %.100s from %.100s not allowed because "
121: "not listed in AllowUsers", pw->pw_name, hostname);
1.1 markus 122: return 0;
1.34 stevesk 123: }
1.1 markus 124: }
125: if (options.num_deny_groups > 0 || options.num_allow_groups > 0) {
1.12 markus 126: /* Get the user's group access list (primary and supplementary) */
1.34 stevesk 127: if (ga_init(pw->pw_name, pw->pw_gid) == 0) {
1.57 dtucker 128: logit("User %.100s from %.100s not allowed because "
129: "not in any group", pw->pw_name, hostname);
1.1 markus 130: return 0;
1.34 stevesk 131: }
1.1 markus 132:
1.12 markus 133: /* Return false if one of user's groups is listed in DenyGroups */
134: if (options.num_deny_groups > 0)
135: if (ga_match(options.deny_groups,
136: options.num_deny_groups)) {
137: ga_free();
1.57 dtucker 138: logit("User %.100s from %.100s not allowed "
139: "because a group is listed in DenyGroups",
140: pw->pw_name, hostname);
1.1 markus 141: return 0;
1.12 markus 142: }
1.1 markus 143: /*
1.12 markus 144: * Return false if AllowGroups isn't empty and one of user's groups
1.1 markus 145: * isn't listed there
146: */
1.12 markus 147: if (options.num_allow_groups > 0)
148: if (!ga_match(options.allow_groups,
149: options.num_allow_groups)) {
150: ga_free();
1.57 dtucker 151: logit("User %.100s from %.100s not allowed "
152: "because none of user's groups are listed "
153: "in AllowGroups", pw->pw_name, hostname);
1.1 markus 154: return 0;
1.12 markus 155: }
156: ga_free();
1.1 markus 157: }
158: /* We found no reason not to let this user try to log on... */
159: return 1;
1.13 markus 160: }
161:
162: void
163: auth_log(Authctxt *authctxt, int authenticated, char *method, char *info)
164: {
165: void (*authlog) (const char *fmt,...) = verbose;
166: char *authmsg;
167:
168: /* Raise logging level */
169: if (authenticated == 1 ||
170: !authctxt->valid ||
1.54 dtucker 171: authctxt->failures >= options.max_authtries / 2 ||
1.13 markus 172: strcmp(method, "password") == 0)
1.47 itojun 173: authlog = logit;
1.13 markus 174:
175: if (authctxt->postponed)
176: authmsg = "Postponed";
177: else
178: authmsg = authenticated ? "Accepted" : "Failed";
179:
180: authlog("%s %s for %s%.100s from %.200s port %d%s",
181: authmsg,
182: method,
1.56 markus 183: authctxt->valid ? "" : "invalid user ",
1.29 markus 184: authctxt->user,
1.13 markus 185: get_remote_ipaddr(),
186: get_remote_port(),
187: info);
188: }
189:
190: /*
1.17 markus 191: * Check whether root logins are disallowed.
1.13 markus 192: */
193: int
1.17 markus 194: auth_root_allowed(char *method)
1.13 markus 195: {
1.17 markus 196: switch (options.permit_root_login) {
197: case PERMIT_YES:
1.13 markus 198: return 1;
1.17 markus 199: case PERMIT_NO_PASSWD:
200: if (strcmp(method, "password") != 0)
201: return 1;
202: break;
203: case PERMIT_FORCED_ONLY:
204: if (forced_command) {
1.47 itojun 205: logit("Root login accepted for forced command.");
1.17 markus 206: return 1;
207: }
208: break;
1.13 markus 209: }
1.47 itojun 210: logit("ROOT LOGIN REFUSED FROM %.200s", get_remote_ipaddr());
1.22 markus 211: return 0;
212: }
213:
214:
215: /*
216: * Given a template and a passwd structure, build a filename
217: * by substituting % tokenised options. Currently, %% becomes '%',
218: * %h becomes the home directory and %u the username.
219: *
220: * This returns a buffer allocated by xmalloc.
221: */
1.59 djm 222: static char *
223: expand_authorized_keys(const char *filename, struct passwd *pw)
1.22 markus 224: {
1.59 djm 225: char *file, *ret;
1.22 markus 226:
1.59 djm 227: file = percent_expand(filename, "h", pw->pw_dir,
228: "u", pw->pw_name, (char *)NULL);
1.22 markus 229:
230: /*
231: * Ensure that filename starts anchored. If not, be backward
232: * compatible and prepend the '%h/'
233: */
1.59 djm 234: if (*file == '/')
235: return (file);
236:
237: ret = xmalloc(MAXPATHLEN);
238: if (strlcpy(ret, pw->pw_dir, MAXPATHLEN) >= MAXPATHLEN ||
239: strlcat(ret, "/", MAXPATHLEN) >= MAXPATHLEN ||
240: strlcat(ret, file, MAXPATHLEN) >= MAXPATHLEN)
241: fatal("expand_authorized_keys: path too long");
1.22 markus 242:
1.59 djm 243: xfree(file);
244: return (ret);
1.22 markus 245: }
246:
247: char *
248: authorized_keys_file(struct passwd *pw)
249: {
1.59 djm 250: return expand_authorized_keys(options.authorized_keys_file, pw);
1.22 markus 251: }
252:
253: char *
254: authorized_keys_file2(struct passwd *pw)
255: {
1.59 djm 256: return expand_authorized_keys(options.authorized_keys_file2, pw);
1.22 markus 257: }
1.24 markus 258:
259: /* return ok if key exists in sysfile or userfile */
260: HostStatus
261: check_key_in_hostfiles(struct passwd *pw, Key *key, const char *host,
262: const char *sysfile, const char *userfile)
263: {
264: Key *found;
265: char *user_hostfile;
266: struct stat st;
1.30 stevesk 267: HostStatus host_status;
1.24 markus 268:
269: /* Check if we know the host and its host key. */
270: found = key_new(key->type);
271: host_status = check_host_in_hostfile(sysfile, host, key, found, NULL);
272:
273: if (host_status != HOST_OK && userfile != NULL) {
274: user_hostfile = tilde_expand_filename(userfile, pw->pw_uid);
275: if (options.strict_modes &&
276: (stat(user_hostfile, &st) == 0) &&
277: ((st.st_uid != 0 && st.st_uid != pw->pw_uid) ||
1.31 deraadt 278: (st.st_mode & 022) != 0)) {
1.47 itojun 279: logit("Authentication refused for %.100s: "
1.24 markus 280: "bad owner or modes for %.200s",
281: pw->pw_name, user_hostfile);
282: } else {
283: temporarily_use_uid(pw);
284: host_status = check_host_in_hostfile(user_hostfile,
285: host, key, found, NULL);
286: restore_uid();
287: }
288: xfree(user_hostfile);
289: }
290: key_free(found);
291:
292: debug2("check_key_in_hostfiles: key %s for %s", host_status == HOST_OK ?
293: "ok" : "not found", host);
294: return host_status;
295: }
296:
1.22 markus 297:
298: /*
299: * Check a given file for security. This is defined as all components
1.44 stevesk 300: * of the path to the file must be owned by either the owner of
1.23 markus 301: * of the file or root and no directories must be group or world writable.
1.22 markus 302: *
303: * XXX Should any specific check be done for sym links ?
304: *
305: * Takes an open file descriptor, the file name, a uid and and
306: * error buffer plus max size as arguments.
307: *
308: * Returns 0 on success and -1 on failure
309: */
310: int
1.25 provos 311: secure_filename(FILE *f, const char *file, struct passwd *pw,
312: char *err, size_t errlen)
1.22 markus 313: {
1.25 provos 314: uid_t uid = pw->pw_uid;
1.28 markus 315: char buf[MAXPATHLEN], homedir[MAXPATHLEN];
1.22 markus 316: char *cp;
1.46 markus 317: int comparehome = 0;
1.22 markus 318: struct stat st;
319:
320: if (realpath(file, buf) == NULL) {
321: snprintf(err, errlen, "realpath %s failed: %s", file,
322: strerror(errno));
323: return -1;
324: }
1.46 markus 325: if (realpath(pw->pw_dir, homedir) != NULL)
326: comparehome = 1;
1.22 markus 327:
328: /* check the open file to avoid races */
329: if (fstat(fileno(f), &st) < 0 ||
330: (st.st_uid != 0 && st.st_uid != uid) ||
331: (st.st_mode & 022) != 0) {
332: snprintf(err, errlen, "bad ownership or modes for file %s",
333: buf);
334: return -1;
335: }
336:
337: /* for each component of the canonical path, walking upwards */
338: for (;;) {
339: if ((cp = dirname(buf)) == NULL) {
340: snprintf(err, errlen, "dirname() failed");
341: return -1;
342: }
343: strlcpy(buf, cp, sizeof(buf));
1.25 provos 344:
1.22 markus 345: debug3("secure_filename: checking '%s'", buf);
346: if (stat(buf, &st) < 0 ||
347: (st.st_uid != 0 && st.st_uid != uid) ||
348: (st.st_mode & 022) != 0) {
1.31 deraadt 349: snprintf(err, errlen,
1.22 markus 350: "bad ownership or modes for directory %s", buf);
351: return -1;
352: }
353:
1.27 markus 354: /* If are passed the homedir then we can stop */
1.46 markus 355: if (comparehome && strcmp(homedir, buf) == 0) {
1.27 markus 356: debug3("secure_filename: terminating check at '%s'",
357: buf);
358: break;
359: }
1.22 markus 360: /*
361: * dirname should always complete with a "/" path,
362: * but we can be paranoid and check for "." too
363: */
364: if ((strcmp("/", buf) == 0) || (strcmp(".", buf) == 0))
365: break;
366: }
1.17 markus 367: return 0;
1.37 provos 368: }
369:
370: struct passwd *
371: getpwnamallow(const char *user)
372: {
1.38 provos 373: #ifdef HAVE_LOGIN_CAP
374: extern login_cap_t *lc;
375: #ifdef BSD_AUTH
376: auth_session_t *as;
377: #endif
378: #endif
1.37 provos 379: struct passwd *pw;
380:
381: pw = getpwnam(user);
1.45 stevesk 382: if (pw == NULL) {
1.55 markus 383: logit("Invalid user %.100s from %.100s",
1.45 stevesk 384: user, get_remote_ipaddr());
385: return (NULL);
386: }
387: if (!allowed_user(pw))
1.38 provos 388: return (NULL);
389: #ifdef HAVE_LOGIN_CAP
390: if ((lc = login_getclass(pw->pw_class)) == NULL) {
391: debug("unable to get login class: %s", user);
392: return (NULL);
393: }
394: #ifdef BSD_AUTH
395: if ((as = auth_open()) == NULL || auth_setpwd(as, pw) != 0 ||
1.43 millert 396: auth_approval(as, lc, pw->pw_name, "ssh") <= 0) {
1.38 provos 397: debug("Approval failure for %s", user);
1.37 provos 398: pw = NULL;
1.38 provos 399: }
400: if (as != NULL)
401: auth_close(as);
402: #endif
403: #endif
1.41 markus 404: if (pw != NULL)
405: return (pwcopy(pw));
406: return (NULL);
1.42 markus 407: }
408:
409: void
410: auth_debug_add(const char *fmt,...)
411: {
412: char buf[1024];
413: va_list args;
414:
415: if (!auth_debug_init)
416: return;
417:
418: va_start(args, fmt);
419: vsnprintf(buf, sizeof(buf), fmt, args);
420: va_end(args);
421: buffer_put_cstring(&auth_debug, buf);
422: }
423:
424: void
425: auth_debug_send(void)
426: {
427: char *msg;
428:
429: if (!auth_debug_init)
430: return;
431: while (buffer_len(&auth_debug)) {
432: msg = buffer_get_string(&auth_debug, NULL);
433: packet_send_debug("%s", msg);
434: xfree(msg);
435: }
436: }
437:
438: void
439: auth_debug_reset(void)
440: {
441: if (auth_debug_init)
442: buffer_clear(&auth_debug);
443: else {
444: buffer_init(&auth_debug);
445: auth_debug_init = 1;
446: }
1.49 markus 447: }
448:
449: struct passwd *
450: fakepw(void)
451: {
452: static struct passwd fake;
453:
454: memset(&fake, 0, sizeof(fake));
455: fake.pw_name = "NOUSER";
456: fake.pw_passwd =
1.51 djm 457: "$2a$06$r3.juUaHZDlIbQaO2dS9FuYxL1W9M81R1Tc92PoSNmzvpEqLkLGrK";
1.49 markus 458: fake.pw_gecos = "NOUSER";
1.53 deraadt 459: fake.pw_uid = (uid_t)-1;
460: fake.pw_gid = (gid_t)-1;
1.49 markus 461: fake.pw_class = "";
462: fake.pw_dir = "/nonexist";
463: fake.pw_shell = "/nonexist";
464:
465: return (&fake);
1.1 markus 466: }
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