2 * Copyright (c) 2000 Markus Friedl. All rights reserved.
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions
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.
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.
26 RCSID("$OpenBSD: auth2.c,v 1.42 2001/02/13 22:49:40 markus Exp $");
28 #include <openssl/evp.h>
47 #include "pathnames.h"
49 #include "auth-options.h"
52 extern ServerOptions options;
53 extern u_char *session_id2;
54 extern int session_id2_len;
56 #ifdef WITH_AIXAUTHENTICATE
57 extern char *aixloginmsg;
60 static Authctxt *x_authctxt = NULL;
63 typedef struct Authmethod Authmethod;
66 int (*userauth)(Authctxt *authctxt);
72 void input_service_request(int type, int plen, void *ctxt);
73 void input_userauth_request(int type, int plen, void *ctxt);
74 void protocol_error(int type, int plen, void *ctxt);
77 Authmethod *authmethod_lookup(const char *name);
78 struct passwd *pwcopy(struct passwd *pw);
79 int user_key_allowed(struct passwd *pw, Key *key);
80 char *authmethods_get(void);
83 void userauth_banner(void);
84 int userauth_none(Authctxt *authctxt);
85 int userauth_passwd(Authctxt *authctxt);
86 int userauth_pubkey(Authctxt *authctxt);
87 int userauth_kbdint(Authctxt *authctxt);
89 Authmethod authmethods[] = {
95 &options.pubkey_authentication},
98 &options.password_authentication},
99 {"keyboard-interactive",
101 &options.kbd_interactive_authentication},
106 * loop until authctxt->success == TRUE
112 Authctxt *authctxt = authctxt_new();
114 x_authctxt = authctxt; /*XXX*/
116 /* challenge-reponse is implemented via keyboard interactive */
117 if (options.challenge_reponse_authentication)
118 options.kbd_interactive_authentication = 1;
120 dispatch_init(&protocol_error);
121 dispatch_set(SSH2_MSG_SERVICE_REQUEST, &input_service_request);
122 dispatch_run(DISPATCH_BLOCK, &authctxt->success, authctxt);
123 do_authenticated2(authctxt);
127 protocol_error(int type, int plen, void *ctxt)
129 log("auth: protocol error: type %d plen %d", type, plen);
130 packet_start(SSH2_MSG_UNIMPLEMENTED);
137 input_service_request(int type, int plen, void *ctxt)
139 Authctxt *authctxt = ctxt;
142 char *service = packet_get_string(&len);
145 if (authctxt == NULL)
146 fatal("input_service_request: no authctxt");
148 if (strcmp(service, "ssh-userauth") == 0) {
149 if (!authctxt->success) {
151 /* now we can handle user-auth requests */
152 dispatch_set(SSH2_MSG_USERAUTH_REQUEST, &input_userauth_request);
155 /* XXX all other service requests are denied */
158 packet_start(SSH2_MSG_SERVICE_ACCEPT);
159 packet_put_cstring(service);
163 debug("bad service request %s", service);
164 packet_disconnect("bad service request %s", service);
170 input_userauth_request(int type, int plen, void *ctxt)
172 Authctxt *authctxt = ctxt;
173 Authmethod *m = NULL;
174 char *user, *service, *method, *style = NULL;
175 int authenticated = 0;
177 if (authctxt == NULL)
178 fatal("input_userauth_request: no authctxt");
180 user = packet_get_string(NULL);
181 service = packet_get_string(NULL);
182 method = packet_get_string(NULL);
183 debug("userauth-request for user %s service %s method %s", user, service, method);
184 debug("attempt %d failures %d", authctxt->attempt, authctxt->failures);
186 if ((style = strchr(user, ':')) != NULL)
189 if (authctxt->attempt++ == 0) {
190 /* setup auth context */
191 struct passwd *pw = NULL;
193 if (pw && allowed_user(pw) && strcmp(service, "ssh-connection")==0) {
194 authctxt->pw = pwcopy(pw);
196 debug2("input_userauth_request: setting up authctxt for %s", user);
198 start_pam(pw->pw_name);
201 log("input_userauth_request: illegal user %s", user);
206 setproctitle("%s", pw ? user : "unknown");
207 authctxt->user = xstrdup(user);
208 authctxt->service = xstrdup(service);
209 authctxt->style = style ? xstrdup(style) : NULL; /* currently unused */
210 } else if (authctxt->valid) {
211 if (strcmp(user, authctxt->user) != 0 ||
212 strcmp(service, authctxt->service) != 0) {
213 log("input_userauth_request: missmatch: (%s,%s)!=(%s,%s)",
214 user, service, authctxt->user, authctxt->service);
219 dispatch_set(SSH2_MSG_USERAUTH_INFO_RESPONSE, &protocol_error);
220 authctxt->postponed = 0;
222 /* try to authenticate user */
223 m = authmethod_lookup(method);
225 debug2("input_userauth_request: try method %s", method);
226 authenticated = m->userauth(authctxt);
228 if (!authctxt->valid && authenticated)
229 fatal("INTERNAL ERROR: authenticated invalid user %s",
232 /* Special handling for root */
233 if (authenticated && authctxt->pw->pw_uid == 0 &&
234 !auth_root_allowed(method))
238 if (authenticated && authctxt->user && !do_pam_account(authctxt->user,
243 /* Log before sending the reply */
244 auth_log(authctxt, authenticated, method, " ssh2");
246 if (!authctxt->postponed)
247 userauth_reply(authctxt, authenticated);
255 userauth_banner(void)
262 if (options.banner == NULL || (datafellows & SSH_BUG_BANNER))
264 if ((fd = open(options.banner, O_RDONLY)) < 0) {
265 error("userauth_banner: open %s failed: %s",
266 options.banner, strerror(errno));
269 if (fstat(fd, &st) < 0)
272 banner = xmalloc(len + 1);
273 if ((n = read(fd, banner, len)) < 0)
276 packet_start(SSH2_MSG_USERAUTH_BANNER);
277 packet_put_cstring(banner);
278 packet_put_cstring(""); /* language, unused */
280 debug("userauth_banner: sent");
289 userauth_reply(Authctxt *authctxt, int authenticated)
293 /* XXX todo: check if multiple auth methods are needed */
294 if (authenticated == 1) {
295 #ifdef WITH_AIXAUTHENTICATE
296 /* We don't have a pty yet, so just label the line as "ssh" */
297 if (loginsuccess(authctxt->user?authctxt->user:"NOUSER",
298 get_canonical_hostname(options.reverse_mapping_check),
299 "ssh", &aixloginmsg) < 0)
301 #endif /* WITH_AIXAUTHENTICATE */
302 /* turn off userauth */
303 dispatch_set(SSH2_MSG_USERAUTH_REQUEST, &protocol_error);
304 packet_start(SSH2_MSG_USERAUTH_SUCCESS);
307 /* now we can break out */
308 authctxt->success = 1;
310 if (authctxt->failures++ > AUTH_FAIL_MAX)
311 packet_disconnect(AUTH_FAIL_MSG, authctxt->user);
312 methods = authmethods_get();
313 packet_start(SSH2_MSG_USERAUTH_FAILURE);
314 packet_put_cstring(methods);
315 packet_put_char(0); /* XXX partial success, unused */
323 userauth_none(Authctxt *authctxt)
325 /* disable method "none", only allowed one time */
326 Authmethod *m = authmethod_lookup("none");
332 if (authctxt->valid == 0)
336 if (check_nt_auth(1, authctxt->pw->pw_uid) == 0)
340 return auth_pam_password(authctxt->pw, "");
341 #elif defined(HAVE_OSF_SIA)
343 #else /* !HAVE_OSF_SIA && !USE_PAM */
344 return auth_password(authctxt->pw, "");
349 userauth_passwd(Authctxt *authctxt)
352 int authenticated = 0;
355 change = packet_get_char();
357 log("password change not supported");
358 password = packet_get_string(&len);
360 if (authctxt->valid &&
362 check_nt_auth(1, authctxt->pw->pw_uid) &&
365 auth_pam_password(authctxt->pw, password) == 1)
366 #elif defined(HAVE_OSF_SIA)
367 auth_sia_password(authctxt->user, password) == 1)
368 #else /* !USE_PAM && !HAVE_OSF_SIA */
369 auth_password(authctxt->pw, password) == 1)
372 memset(password, 0, len);
374 return authenticated;
378 userauth_kbdint(Authctxt *authctxt)
380 int authenticated = 0;
384 lang = packet_get_string(NULL);
385 devs = packet_get_string(NULL);
388 debug("keyboard-interactive language %s devs %s", lang, devs);
390 if (options.challenge_reponse_authentication)
391 authenticated = auth2_challenge(authctxt, devs);
394 if (authenticated == 0)
395 authenticated = auth2_pam(authctxt);
400 if (check_nt_auth(0, authctxt->pw->pw_uid) == 0)
403 return authenticated;
407 userauth_pubkey(Authctxt *authctxt)
411 char *pkalg, *pkblob, *sig;
412 u_int alen, blen, slen;
413 int have_sig, pktype;
414 int authenticated = 0;
416 if (!authctxt->valid) {
417 debug2("userauth_pubkey: disabled because of invalid user");
420 have_sig = packet_get_char();
421 if (datafellows & SSH_BUG_PKAUTH) {
422 debug2("userauth_pubkey: SSH_BUG_PKAUTH");
423 /* no explicit pkalg given */
424 pkblob = packet_get_string(&blen);
426 buffer_append(&b, pkblob, blen);
427 /* so we have to extract the pkalg from the pkblob */
428 pkalg = buffer_get_string(&b, &alen);
431 pkalg = packet_get_string(&alen);
432 pkblob = packet_get_string(&blen);
434 pktype = key_type_from_name(pkalg);
435 if (pktype == KEY_UNSPEC) {
436 /* this is perfectly legal */
437 log("userauth_pubkey: unsupported public key algorithm: %s", pkalg);
442 key = key_from_blob(pkblob, blen);
445 sig = packet_get_string(&slen);
448 if (datafellows & SSH_OLD_SESSIONID) {
449 buffer_append(&b, session_id2, session_id2_len);
451 buffer_put_string(&b, session_id2, session_id2_len);
453 /* reconstruct packet */
454 buffer_put_char(&b, SSH2_MSG_USERAUTH_REQUEST);
455 buffer_put_cstring(&b, authctxt->user);
456 buffer_put_cstring(&b,
457 datafellows & SSH_BUG_PKSERVICE ?
460 if (datafellows & SSH_BUG_PKAUTH) {
461 buffer_put_char(&b, have_sig);
463 buffer_put_cstring(&b, "publickey");
464 buffer_put_char(&b, have_sig);
465 buffer_put_cstring(&b, key_ssh_name(key));
467 buffer_put_string(&b, pkblob, blen);
471 /* test for correct signature */
472 if (user_key_allowed(authctxt->pw, key) &&
473 key_verify(key, sig, slen, buffer_ptr(&b), buffer_len(&b)) == 1)
478 debug("test whether pkalg/pkblob are acceptable");
481 /* XXX fake reply and always send PK_OK ? */
483 * XXX this allows testing whether a user is allowed
484 * to login: if you happen to have a valid pubkey this
485 * message is sent. the message is NEVER sent at all
486 * if a user is not allowed to login. is this an
489 if (user_key_allowed(authctxt->pw, key)) {
490 packet_start(SSH2_MSG_USERAUTH_PK_OK);
491 packet_put_string(pkalg, alen);
492 packet_put_string(pkblob, blen);
495 authctxt->postponed = 1;
498 if (authenticated != 1)
499 auth_clear_options();
502 debug2("userauth_pubkey: authenticated %d pkalg %s", authenticated, pkalg);
506 if (check_nt_auth(0, authctxt->pw->pw_uid) == 0)
509 return authenticated;
512 /* get current user */
517 return (x_authctxt != NULL && x_authctxt->valid) ? x_authctxt->pw : NULL;
523 authmethods_get(void)
525 Authmethod *method = NULL;
529 for (method = authmethods; method->name != NULL; method++) {
530 if (strcmp(method->name, "none") == 0)
532 if (method->enabled != NULL && *(method->enabled) != 0) {
534 size += strlen(DELIM);
535 size += strlen(method->name);
538 size++; /* trailing '\0' */
539 list = xmalloc(size);
542 for (method = authmethods; method->name != NULL; method++) {
543 if (strcmp(method->name, "none") == 0)
545 if (method->enabled != NULL && *(method->enabled) != 0) {
547 strlcat(list, DELIM, size);
548 strlcat(list, method->name, size);
555 authmethod_lookup(const char *name)
557 Authmethod *method = NULL;
559 for (method = authmethods; method->name != NULL; method++)
560 if (method->enabled != NULL &&
561 *(method->enabled) != 0 &&
562 strcmp(name, method->name) == 0)
564 debug2("Unrecognized authentication method name: %s", name ? name : "NULL");
568 /* return 1 if user allows given key */
570 user_key_allowed(struct passwd *pw, Key *key)
572 char line[8192], file[MAXPATHLEN];
582 /* Temporarily use the user's uid. */
583 temporarily_use_uid(pw->pw_uid);
585 /* The authorized keys. */
586 snprintf(file, sizeof file, "%.500s/%.100s", pw->pw_dir,
587 _PATH_SSH_USER_PERMITTED_KEYS2);
589 /* Fail quietly if file does not exist */
590 if (stat(file, &st) < 0) {
591 /* Restore the privileged uid. */
595 /* Open the file containing the authorized keys. */
596 f = fopen(file, "r");
598 /* Restore the privileged uid. */
602 if (options.strict_modes) {
605 /* Check open file in order to avoid open/stat races */
606 if (fstat(fileno(f), &st) < 0 ||
607 (st.st_uid != 0 && st.st_uid != pw->pw_uid) ||
608 (st.st_mode & 022) != 0) {
609 snprintf(buf, sizeof buf,
610 "%s authentication refused for %.100s: "
611 "bad ownership or modes for '%s'.",
612 key_type(key), pw->pw_name, file);
615 /* Check path to _PATH_SSH_USER_PERMITTED_KEYS */
617 static const char *check[] = {
618 "", _PATH_SSH_USER_DIR, NULL
620 for (i = 0; check[i]; i++) {
621 snprintf(line, sizeof line, "%.500s/%.100s",
622 pw->pw_dir, check[i]);
623 if (stat(line, &st) < 0 ||
624 (st.st_uid != 0 && st.st_uid != pw->pw_uid) ||
625 (st.st_mode & 022) != 0) {
626 snprintf(buf, sizeof buf,
627 "%s authentication refused for %.100s: "
628 "bad ownership or modes for '%s'.",
629 key_type(key), pw->pw_name, line);
643 found = key_new(key->type);
645 while (fgets(line, sizeof(line), f)) {
646 char *cp, *options = NULL;
648 /* Skip leading whitespace, empty and comment lines. */
649 for (cp = line; *cp == ' ' || *cp == '\t'; cp++)
651 if (!*cp || *cp == '\n' || *cp == '#')
654 if (key_read(found, &cp) == -1) {
655 /* no key? check if there are options for this key */
657 debug2("user_key_allowed: check options: '%s'", cp);
659 for (; *cp && (quoted || (*cp != ' ' && *cp != '\t')); cp++) {
660 if (*cp == '\\' && cp[1] == '"')
661 cp++; /* Skip both */
665 /* Skip remaining whitespace. */
666 for (; *cp == ' ' || *cp == '\t'; cp++)
668 if (key_read(found, &cp) == -1) {
669 debug2("user_key_allowed: advance: '%s'", cp);
670 /* still no key? advance to next line*/
674 if (key_equal(found, key) &&
675 auth_parse_options(pw, options, file, linenum) == 1) {
677 debug("matching key found: file %s, line %ld",