1 /* vi: set sw=4 ts=4: */
3 * Licensed under GPLv2 or later, see file LICENSE in this source tree.
8 //config: select FEATURE_SYSLOG
10 //config: login is used when signing onto a system.
12 //config: Note that Busybox binary must be setuid root for this applet to
13 //config: work properly.
15 //config:config LOGIN_SESSION_AS_CHILD
16 //config: bool "Run logged in session in a child process"
17 //config: default y if PAM
18 //config: depends on LOGIN
20 //config: Run the logged in session in a child process. This allows
21 //config: login to clean up things such as utmp entries or PAM sessions
22 //config: when the login session is complete. If you use PAM, you
23 //config: almost always would want this to be set to Y, else PAM session
24 //config: will not be cleaned up.
26 //config:config LOGIN_SCRIPTS
27 //config: bool "Support for login scripts"
28 //config: depends on LOGIN
31 //config: Enable this if you want login to execute $LOGIN_PRE_SUID_SCRIPT
32 //config: just prior to switching from root to logged-in user.
34 //config:config FEATURE_NOLOGIN
35 //config: bool "Support for /etc/nologin"
37 //config: depends on LOGIN
39 //config: The file /etc/nologin is used by (some versions of) login(1).
40 //config: If it exists, non-root logins are prohibited.
42 //config:config FEATURE_SECURETTY
43 //config: bool "Support for /etc/securetty"
45 //config: depends on LOGIN
47 //config: The file /etc/securetty is used by (some versions of) login(1).
48 //config: The file contains the device names of tty lines (one per line,
49 //config: without leading /dev/) on which root is allowed to login.
51 //applet:/* Needs to be run by root or be suid root - needs to change uid and gid: */
52 //applet:IF_LOGIN(APPLET(login, BB_DIR_BIN, BB_SUID_REQUIRE))
54 //kbuild:lib-$(CONFIG_LOGIN) += login.o
56 //usage:#define login_trivial_usage
57 //usage: "[-p] [-h HOST] [[-f] USER]"
58 //usage:#define login_full_usage "\n\n"
59 //usage: "Begin a new session on the system\n"
60 //usage: "\n -f Don't authenticate (user already authenticated)"
61 //usage: "\n -h HOST Host user came from (for network logins)"
62 //usage: "\n -p Preserve environment"
66 #include <sys/resource.h>
69 # include <selinux/selinux.h> /* for is_selinux_enabled() */
70 # include <selinux/get_context_list.h> /* for get_default_context() */
71 # include <selinux/flask.h> /* for security class definitions */
75 /* PAM may include <locale.h>. We may need to undefine bbox's stub define: */
77 /* For some obscure reason, PAM is not in pam/xxx, but in security/xxx.
78 * Apparently they like to confuse people. */
79 # include <security/pam_appl.h>
80 # include <security/pam_misc.h>
81 static const struct pam_conv conv = {
89 EMPTY_USERNAME_COUNT = 10,
90 /* Some users found 32 chars limit to be too low: */
96 struct termios tty_attrs;
98 #define G (*(struct globals*)&bb_common_bufsiz1)
99 #define INIT_G() do { } while (0)
102 #if ENABLE_FEATURE_NOLOGIN
103 static void die_if_nologin(void)
109 fp = fopen_for_read("/etc/nologin");
110 if (!fp) /* assuming it does not exist */
113 while ((c = getc(fp)) != EOF) {
120 puts("\r\nSystem closed for routine maintenance\r");
124 /* Users say that they do need this prior to exit: */
125 tcdrain(STDOUT_FILENO);
129 # define die_if_nologin() ((void)0)
132 #if ENABLE_FEATURE_SECURETTY && !ENABLE_PAM
133 static int check_securetty(const char *short_tty)
135 char *buf = (char*)"/etc/securetty"; /* any non-NULL is ok */
136 parser_t *parser = config_open2("/etc/securetty", fopen_for_read);
137 while (config_read(parser, &buf, 1, 1, "# \t", PARSE_NORMAL)) {
138 if (strcmp(buf, short_tty) == 0)
142 config_close(parser);
143 /* buf != NULL here if config file was not found, empty
144 * or line was found which equals short_tty */
148 static ALWAYS_INLINE int check_securetty(const char *short_tty UNUSED_PARAM) { return 1; }
152 static void initselinux(char *username, char *full_tty,
153 security_context_t *user_sid)
155 security_context_t old_tty_sid, new_tty_sid;
157 if (!is_selinux_enabled())
160 if (get_default_context(username, NULL, user_sid)) {
161 bb_error_msg_and_die("can't get SID for %s", username);
163 if (getfilecon(full_tty, &old_tty_sid) < 0) {
164 bb_perror_msg_and_die("getfilecon(%s) failed", full_tty);
166 if (security_compute_relabel(*user_sid, old_tty_sid,
167 SECCLASS_CHR_FILE, &new_tty_sid) != 0) {
168 bb_perror_msg_and_die("security_change_sid(%s) failed", full_tty);
170 if (setfilecon(full_tty, new_tty_sid) != 0) {
171 bb_perror_msg_and_die("chsid(%s, %s) failed", full_tty, new_tty_sid);
176 #if ENABLE_LOGIN_SCRIPTS
177 static void run_login_script(struct passwd *pw, char *full_tty)
181 t_argv[0] = getenv("LOGIN_PRE_SUID_SCRIPT");
184 xsetenv("LOGIN_TTY", full_tty);
185 xsetenv("LOGIN_USER", pw->pw_name);
186 xsetenv("LOGIN_UID", utoa(pw->pw_uid));
187 xsetenv("LOGIN_GID", utoa(pw->pw_gid));
188 xsetenv("LOGIN_SHELL", pw->pw_shell);
189 spawn_and_wait(t_argv); /* NOMMU-friendly */
190 unsetenv("LOGIN_TTY");
191 unsetenv("LOGIN_USER");
192 unsetenv("LOGIN_UID");
193 unsetenv("LOGIN_GID");
194 unsetenv("LOGIN_SHELL");
198 void run_login_script(struct passwd *pw, char *full_tty);
201 #if ENABLE_LOGIN_SESSION_AS_CHILD && ENABLE_PAM
202 static void login_pam_end(pam_handle_t *pamh)
206 pamret = pam_setcred(pamh, PAM_DELETE_CRED);
207 if (pamret != PAM_SUCCESS) {
208 bb_error_msg("pam_%s failed: %s (%d)", "setcred",
209 pam_strerror(pamh, pamret), pamret);
211 pamret = pam_close_session(pamh, 0);
212 if (pamret != PAM_SUCCESS) {
213 bb_error_msg("pam_%s failed: %s (%d)", "close_session",
214 pam_strerror(pamh, pamret), pamret);
216 pamret = pam_end(pamh, pamret);
217 if (pamret != PAM_SUCCESS) {
218 bb_error_msg("pam_%s failed: %s (%d)", "end",
219 pam_strerror(pamh, pamret), pamret);
222 #endif /* ENABLE_PAM */
224 static void get_username_or_die(char *buf, int size_buf)
228 cntdown = EMPTY_USERNAME_COUNT;
230 print_login_prompt();
231 /* skip whitespace */
241 } while (isspace(c)); /* maybe isblank? */
244 if (!fgets(buf, size_buf-2, stdin))
246 if (!strchr(buf, '\n'))
248 while ((unsigned char)*buf > ' ')
253 static void motd(void)
257 fd = open(bb_path_motd_file, O_RDONLY);
260 bb_copyfd_eof(fd, STDOUT_FILENO);
265 static void alarm_handler(int sig UNUSED_PARAM)
267 /* This is the escape hatch! Poor serial line users and the like
268 * arrive here when their connection is broken.
269 * We don't want to block here */
270 ndelay_on(STDOUT_FILENO);
271 /* Test for correct attr restoring:
272 * run "getty 0 -" from a shell, enter bogus username, stop at
273 * password prompt, let it time out. Without the tcsetattr below,
274 * when you are back at shell prompt, echo will be still off.
276 tcsetattr_stdin_TCSANOW(&G.tty_attrs);
277 printf("\r\nLogin timed out after %u seconds\r\n", TIMEOUT);
279 /* unix API is brain damaged regarding O_NONBLOCK,
280 * we should undo it, or else we can affect other processes */
281 ndelay_off(STDOUT_FILENO);
285 int login_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
286 int login_main(int argc UNUSED_PARAM, char **argv)
289 LOGIN_OPT_f = (1<<0),
290 LOGIN_OPT_h = (1<<1),
291 LOGIN_OPT_p = (1<<2),
294 char username[USERNAME_SIZE];
299 char *opt_host = NULL;
300 char *opt_user = opt_user; /* for compiler */
303 IF_SELINUX(security_context_t user_sid = NULL;)
308 const char *failed_msg;
309 struct passwd pwdstruct;
313 #if ENABLE_LOGIN_SESSION_AS_CHILD
319 /* More of suid paranoia if called by non-root: */
320 /* Clear dangerous stuff, set PATH */
321 run_by_root = !sanitize_env_if_suid();
323 /* Mandatory paranoia for suid applet:
324 * ensure that fd# 0,1,2 are opened (at least to /dev/null)
325 * and any extra open fd's are closed.
326 * (The name of the function is misleading. Not daemonizing here.) */
327 bb_daemonize_or_rexec(DAEMON_ONLY_SANITIZE | DAEMON_CLOSE_EXTRA_FDS, NULL);
330 opt = getopt32(argv, "f:h:p", &opt_user, &opt_host);
331 if (opt & LOGIN_OPT_f) {
333 bb_error_msg_and_die("-f is for root only");
334 safe_strncpy(username, opt_user, sizeof(username));
337 if (argv[0]) /* user from command line (getty) */
338 safe_strncpy(username, argv[0], sizeof(username));
340 /* Save tty attributes - and by doing it, check that it's indeed a tty */
341 if (tcgetattr(STDIN_FILENO, &G.tty_attrs) < 0
342 || !isatty(STDOUT_FILENO)
343 /*|| !isatty(STDERR_FILENO) - no, guess some people might want to redirect this */
345 return EXIT_FAILURE; /* Must be a terminal */
348 /* We install timeout handler only _after_ we saved G.tty_attrs */
349 signal(SIGALRM, alarm_handler);
352 /* Find out and memorize our tty name */
353 full_tty = xmalloc_ttyname(STDIN_FILENO);
355 full_tty = xstrdup("UNKNOWN");
356 short_tty = skip_dev_pfx(full_tty);
359 fromhost = xasprintf(" on '%s' from '%s'", short_tty, opt_host);
361 fromhost = xasprintf(" on '%s'", short_tty);
364 /* Was breaking "login <username>" from shell command line: */
367 openlog(applet_name, LOG_PID | LOG_CONS, LOG_AUTH);
370 /* flush away any type-ahead (as getty does) */
371 tcflush(0, TCIFLUSH);
374 get_username_or_die(username, sizeof(username));
377 pamret = pam_start("login", username, &conv, &pamh);
378 if (pamret != PAM_SUCCESS) {
379 failed_msg = "start";
380 goto pam_auth_failed;
382 /* set TTY (so things like securetty work) */
383 pamret = pam_set_item(pamh, PAM_TTY, short_tty);
384 if (pamret != PAM_SUCCESS) {
385 failed_msg = "set_item(TTY)";
386 goto pam_auth_failed;
390 pamret = pam_set_item(pamh, PAM_RHOST, opt_host);
391 if (pamret != PAM_SUCCESS) {
392 failed_msg = "set_item(RHOST)";
393 goto pam_auth_failed;
396 if (!(opt & LOGIN_OPT_f)) {
397 pamret = pam_authenticate(pamh, 0);
398 if (pamret != PAM_SUCCESS) {
399 failed_msg = "authenticate";
400 goto pam_auth_failed;
401 /* TODO: or just "goto auth_failed"
402 * since user seems to enter wrong password
403 * (in this case pamret == 7)
407 /* check that the account is healthy */
408 pamret = pam_acct_mgmt(pamh, 0);
409 if (pamret != PAM_SUCCESS) {
410 failed_msg = "acct_mgmt";
411 goto pam_auth_failed;
415 /* gcc: "dereferencing type-punned pointer breaks aliasing rules..."
416 * thus we cast to (void*) */
417 if (pam_get_item(pamh, PAM_USER, (void*)&pamuser) != PAM_SUCCESS) {
418 failed_msg = "get_item(USER)";
419 goto pam_auth_failed;
421 if (!pamuser || !pamuser[0])
423 safe_strncpy(username, pamuser, sizeof(username));
424 /* Don't use "pw = getpwnam(username);",
425 * PAM is said to be capable of destroying static storage
426 * used by getpwnam(). We are using safe(r) function */
428 getpwnam_r(username, &pwdstruct, pwdbuf, sizeof(pwdbuf), &pw);
431 pamret = pam_open_session(pamh, 0);
432 if (pamret != PAM_SUCCESS) {
433 failed_msg = "open_session";
434 goto pam_auth_failed;
436 pamret = pam_setcred(pamh, PAM_ESTABLISH_CRED);
437 if (pamret != PAM_SUCCESS) {
438 failed_msg = "setcred";
439 goto pam_auth_failed;
441 break; /* success, continue login process */
444 /* syslog, because we don't want potential attacker
445 * to know _why_ login failed */
446 syslog(LOG_WARNING, "pam_%s call failed: %s (%d)", failed_msg,
447 pam_strerror(pamh, pamret), pamret);
448 safe_strncpy(username, "UNKNOWN", sizeof(username));
450 pw = getpwnam(username);
452 strcpy(username, "UNKNOWN");
456 if (pw->pw_passwd[0] == '!' || pw->pw_passwd[0] == '*')
459 if (opt & LOGIN_OPT_f)
460 break; /* -f USER: success without asking passwd */
462 if (pw->pw_uid == 0 && !check_securetty(short_tty))
465 /* Don't check the password if password entry is empty (!) */
466 if (!pw->pw_passwd[0])
469 /* Password reading and authorization takes place here.
470 * Note that reads (in no-echo mode) trash tty attributes.
471 * If we get interrupted by SIGALRM, we need to restore attrs.
473 if (ask_and_check_password(pw) > 0)
475 #endif /* ENABLE_PAM */
478 bb_do_delay(LOGIN_FAIL_DELAY);
479 /* TODO: doesn't sound like correct English phrase to me */
480 puts("Login incorrect");
482 syslog(LOG_WARNING, "invalid password for '%s'%s",
485 if (ENABLE_FEATURE_CLEAN_UP)
494 /* We can ignore /etc/nologin if we are logging in as root,
495 * it doesn't matter whether we are run by root or not */
499 #if ENABLE_LOGIN_SESSION_AS_CHILD
501 if (child_pid != 0) {
503 bb_perror_msg("vfork");
505 if (safe_waitpid(child_pid, NULL, 0) == -1)
506 bb_perror_msg("waitpid");
507 update_utmp_DEAD_PROCESS(child_pid);
509 IF_PAM(login_pam_end(pamh);)
514 IF_SELINUX(initselinux(username, full_tty, &user_sid);)
516 /* Try these, but don't complain if they fail.
517 * _f_chown is safe wrt race t=ttyname(0);...;chown(t); */
518 fchown(0, pw->pw_uid, pw->pw_gid);
521 update_utmp(getpid(), USER_PROCESS, short_tty, username, run_by_root ? opt_host : NULL);
523 /* We trust environment only if we run by root */
524 if (ENABLE_LOGIN_SCRIPTS && run_by_root)
525 run_login_script(pw, full_tty);
528 setup_environment(pw->pw_shell,
529 (!(opt & LOGIN_OPT_p) * SETUP_ENV_CLEARENV) + SETUP_ENV_CHANGEENV,
533 /* Modules such as pam_env will setup the PAM environment,
534 * which should be copied into the new environment. */
535 pamenv = pam_getenvlist(pamh);
536 if (pamenv) while (*pamenv) {
542 if (access(".hushlogin", F_OK) != 0)
546 syslog(LOG_INFO, "root login%s", fromhost);
548 if (ENABLE_FEATURE_CLEAN_UP)
551 /* well, a simple setexeccon() here would do the job as well,
552 * but let's play the game for now */
553 IF_SELINUX(set_current_security_context(user_sid);)
555 // util-linux login also does:
556 // /* start new session */
558 // /* TIOCSCTTY: steal tty from other process group */
559 // if (ioctl(0, TIOCSCTTY, 1)) error_msg...
560 // BBox login used to do this (see above):
562 // If this stuff is really needed, add it and explain why!
564 /* Set signals to defaults */
565 /* Non-ignored signals revert to SIG_DFL on exec anyway */
566 /*signal(SIGALRM, SIG_DFL);*/
568 /* Is this correct? This way user can ctrl-c out of /etc/profile,
569 * potentially creating security breach (tested with bash 3.0).
570 * But without this, bash 3.0 will not enable ctrl-c either.
571 * Maybe bash is buggy?
572 * Need to find out what standards say about /bin/login -
573 * should we leave SIGINT etc enabled or disabled? */
574 signal(SIGINT, SIG_DFL);
576 /* Exec login shell with no additional parameters */
577 run_shell(pw->pw_shell, 1, NULL, NULL);
579 /* return EXIT_FAILURE; - not reached */