1 /* vi: set sw=4 ts=4: */
3 * Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
9 #include <sys/resource.h>
12 #include <selinux/selinux.h> /* for is_selinux_enabled() */
13 #include <selinux/get_context_list.h> /* for get_default_context() */
14 #include <selinux/flask.h> /* for security class definitions */
18 /* PAM may include <locale.h>. We may need to undefine bbox's stub define: */
20 /* For some obscure reason, PAM is not in pam/xxx, but in security/xxx.
21 * Apparently they like to confuse people. */
22 #include <security/pam_appl.h>
23 #include <security/pam_misc.h>
24 static const struct pam_conv conv = {
32 EMPTY_USERNAME_COUNT = 10,
37 static char* short_tty;
39 #if ENABLE_FEATURE_UTMP
40 /* vv Taken from tinylogin utmp.c vv */
42 * read_or_build_utent - see if utmp file is correct for this process
44 * System V is very picky about the contents of the utmp file
45 * and requires that a slot for the current process exist.
46 * The utmp file is scanned for an entry with the same process
47 * ID. If no entry exists the process exits with a message.
49 * The "picky" flag is for network and other logins that may
50 * use special flags. It allows the pid checks to be overridden.
51 * This means that getty should never invoke login with any
55 static void read_or_build_utent(struct utmp *utptr, int picky)
62 /* First, try to find a valid utmp entry for this process. */
63 while ((ut = getutent()))
64 if (ut->ut_pid == pid && ut->ut_line[0] && ut->ut_id[0] &&
65 (ut->ut_type == LOGIN_PROCESS || ut->ut_type == USER_PROCESS))
68 /* If there is one, just use it, otherwise create a new one. */
73 bb_error_msg_and_die("no utmp entry found");
75 memset(utptr, 0, sizeof(*utptr));
76 utptr->ut_type = LOGIN_PROCESS;
78 strncpy(utptr->ut_line, short_tty, sizeof(utptr->ut_line));
79 /* This one is only 4 chars wide. Try to fit something
80 * remotely meaningful by skipping "tty"... */
81 strncpy(utptr->ut_id, short_tty + 3, sizeof(utptr->ut_id));
82 strncpy(utptr->ut_user, "LOGIN", sizeof(utptr->ut_user));
83 utptr->ut_tv.tv_sec = time(NULL);
85 if (!picky) /* root login */
86 memset(utptr->ut_host, 0, sizeof(utptr->ut_host));
90 * write_utent - put a USER_PROCESS entry in the utmp file
92 * write_utent changes the type of the current utmp entry to
93 * USER_PROCESS. the wtmp file will be updated as well.
95 static void write_utent(struct utmp *utptr, const char *username)
97 utptr->ut_type = USER_PROCESS;
98 strncpy(utptr->ut_user, username, sizeof(utptr->ut_user));
99 utptr->ut_tv.tv_sec = time(NULL);
100 /* other fields already filled in by read_or_build_utent above */
104 #if ENABLE_FEATURE_WTMP
105 if (access(bb_path_wtmp_file, R_OK|W_OK) == -1) {
106 close(creat(bb_path_wtmp_file, 0664));
108 updwtmp(bb_path_wtmp_file, utptr);
111 #else /* !ENABLE_FEATURE_UTMP */
112 #define read_or_build_utent(utptr, picky) ((void)0)
113 #define write_utent(utptr, username) ((void)0)
114 #endif /* !ENABLE_FEATURE_UTMP */
116 #if ENABLE_FEATURE_NOLOGIN
117 static void die_if_nologin(void)
123 fp = fopen_for_read("/etc/nologin");
124 if (!fp) /* assuming it does not exist */
127 while ((c = getc(fp)) != EOF) {
134 puts("\r\nSystem closed for routine maintenance\r");
138 /* Users say that they do need this prior to exit: */
139 tcdrain(STDOUT_FILENO);
143 static ALWAYS_INLINE void die_if_nologin(void) {}
146 #if ENABLE_FEATURE_SECURETTY && !ENABLE_PAM
147 static int check_securetty(void)
149 char *buf = (char*)"/etc/securetty"; /* any non-NULL is ok */
150 parser_t *parser = config_open2("/etc/securetty", fopen_for_read);
151 while (config_read(parser, &buf, 1, 1, "# \t", PARSE_NORMAL)) {
152 if (strcmp(buf, short_tty) == 0)
156 config_close(parser);
157 /* buf != NULL here if config file was not found, empty
158 * or line was found which equals short_tty */
162 static ALWAYS_INLINE int check_securetty(void) { return 1; }
165 static void get_username_or_die(char *buf, int size_buf)
169 cntdown = EMPTY_USERNAME_COUNT;
171 print_login_prompt();
172 /* skip whitespace */
175 if (c == EOF) exit(EXIT_FAILURE);
177 if (!--cntdown) exit(EXIT_FAILURE);
180 } while (isspace(c));
183 if (!fgets(buf, size_buf-2, stdin))
185 if (!strchr(buf, '\n'))
187 while (isgraph(*buf)) buf++;
191 static void motd(void)
195 fd = open(bb_path_motd_file, O_RDONLY);
198 bb_copyfd_eof(fd, STDOUT_FILENO);
203 static void alarm_handler(int sig UNUSED_PARAM)
205 /* This is the escape hatch! Poor serial line users and the like
206 * arrive here when their connection is broken.
207 * We don't want to block here */
209 printf("\r\nLogin timed out after %d seconds\r\n", TIMEOUT);
211 /* unix API is brain damaged regarding O_NONBLOCK,
212 * we should undo it, or else we can affect other processes */
217 int login_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
218 int login_main(int argc UNUSED_PARAM, char **argv)
221 LOGIN_OPT_f = (1<<0),
222 LOGIN_OPT_h = (1<<1),
223 LOGIN_OPT_p = (1<<2),
226 char username[USERNAME_SIZE];
232 char *opt_host = opt_host; /* for compiler */
233 char *opt_user = opt_user; /* for compiler */
234 char full_tty[TTYNAME_SIZE];
235 USE_SELINUX(security_context_t user_sid = NULL;)
236 USE_FEATURE_UTMP(struct utmp utent;)
241 const char *failed_msg;
242 struct passwd pwdstruct;
246 short_tty = full_tty;
248 signal(SIGALRM, alarm_handler);
251 /* More of suid paranoia if called by non-root */
252 amroot = !sanitize_env_if_suid(); /* Clear dangerous stuff, set PATH */
254 /* Mandatory paranoia for suid applet:
255 * ensure that fd# 0,1,2 are opened (at least to /dev/null)
256 * and any extra open fd's are closed.
257 * (The name of the function is misleading. Not daemonizing here.) */
258 bb_daemonize_or_rexec(DAEMON_ONLY_SANITIZE | DAEMON_CLOSE_EXTRA_FDS, NULL);
260 opt = getopt32(argv, "f:h:p", &opt_user, &opt_host);
261 if (opt & LOGIN_OPT_f) {
263 bb_error_msg_and_die("-f is for root only");
264 safe_strncpy(username, opt_user, sizeof(username));
267 if (argv[0]) /* user from command line (getty) */
268 safe_strncpy(username, argv[0], sizeof(username));
270 /* Let's find out and memorize our tty */
271 if (!isatty(0) || !isatty(1) || !isatty(2))
272 return EXIT_FAILURE; /* Must be a terminal */
273 safe_strncpy(full_tty, "UNKNOWN", sizeof(full_tty));
276 safe_strncpy(full_tty, tmp, sizeof(full_tty));
277 if (strncmp(full_tty, "/dev/", 5) == 0)
278 short_tty = full_tty + 5;
281 read_or_build_utent(&utent, !amroot);
283 if (opt & LOGIN_OPT_h) {
285 safe_strncpy(utent.ut_host, opt_host, sizeof(utent.ut_host));
287 fromhost = xasprintf(" on '%s' from '%s'", short_tty, opt_host);
289 fromhost = xasprintf(" on '%s'", short_tty);
291 /* Was breaking "login <username>" from shell command line: */
294 openlog(applet_name, LOG_PID | LOG_CONS | LOG_NOWAIT, LOG_AUTH);
297 /* flush away any type-ahead (as getty does) */
298 ioctl(0, TCFLSH, TCIFLUSH);
301 get_username_or_die(username, sizeof(username));
304 pamret = pam_start("login", username, &conv, &pamh);
305 if (pamret != PAM_SUCCESS) {
306 failed_msg = "start";
307 goto pam_auth_failed;
309 /* set TTY (so things like securetty work) */
310 pamret = pam_set_item(pamh, PAM_TTY, short_tty);
311 if (pamret != PAM_SUCCESS) {
312 failed_msg = "set_item(TTY)";
313 goto pam_auth_failed;
315 pamret = pam_authenticate(pamh, 0);
316 if (pamret != PAM_SUCCESS) {
317 failed_msg = "authenticate";
318 goto pam_auth_failed;
319 /* TODO: or just "goto auth_failed"
320 * since user seems to enter wrong password
321 * (in this case pamret == 7)
324 /* check that the account is healthy */
325 pamret = pam_acct_mgmt(pamh, 0);
326 if (pamret != PAM_SUCCESS) {
327 failed_msg = "acct_mgmt";
328 goto pam_auth_failed;
332 /* gcc: "dereferencing type-punned pointer breaks aliasing rules..."
333 * thus we cast to (void*) */
334 if (pam_get_item(pamh, PAM_USER, (void*)&pamuser) != PAM_SUCCESS) {
335 failed_msg = "get_item(USER)";
336 goto pam_auth_failed;
338 if (!pamuser || !pamuser[0])
340 safe_strncpy(username, pamuser, sizeof(username));
341 /* Don't use "pw = getpwnam(username);",
342 * PAM is said to be capable of destroying static storage
343 * used by getpwnam(). We are using safe(r) function */
345 getpwnam_r(username, &pwdstruct, pwdbuf, sizeof(pwdbuf), &pw);
348 pamret = pam_open_session(pamh, 0);
349 if (pamret != PAM_SUCCESS) {
350 failed_msg = "open_session";
351 goto pam_auth_failed;
353 pamret = pam_setcred(pamh, PAM_ESTABLISH_CRED);
354 if (pamret != PAM_SUCCESS) {
355 failed_msg = "setcred";
356 goto pam_auth_failed;
358 break; /* success, continue login process */
361 bb_error_msg("pam_%s call failed: %s (%d)", failed_msg,
362 pam_strerror(pamh, pamret), pamret);
363 safe_strncpy(username, "UNKNOWN", sizeof(username));
365 pw = getpwnam(username);
367 strcpy(username, "UNKNOWN");
371 if (pw->pw_passwd[0] == '!' || pw->pw_passwd[0] == '*')
374 if (opt & LOGIN_OPT_f)
375 break; /* -f USER: success without asking passwd */
377 if (pw->pw_uid == 0 && !check_securetty())
380 /* Don't check the password if password entry is empty (!) */
381 if (!pw->pw_passwd[0])
384 /* authorization takes place here */
385 if (correct_password(pw))
387 #endif /* ENABLE_PAM */
390 bb_do_delay(FAIL_DELAY);
391 /* TODO: doesn't sound like correct English phrase to me */
392 puts("Login incorrect");
394 syslog(LOG_WARNING, "invalid password for '%s'%s",
405 write_utent(&utent, username);
408 if (is_selinux_enabled()) {
409 security_context_t old_tty_sid, new_tty_sid;
411 if (get_default_context(username, NULL, &user_sid)) {
412 bb_error_msg_and_die("cannot get SID for %s",
415 if (getfilecon(full_tty, &old_tty_sid) < 0) {
416 bb_perror_msg_and_die("getfilecon(%s) failed",
419 if (security_compute_relabel(user_sid, old_tty_sid,
420 SECCLASS_CHR_FILE, &new_tty_sid) != 0) {
421 bb_perror_msg_and_die("security_change_sid(%s) failed",
424 if (setfilecon(full_tty, new_tty_sid) != 0) {
425 bb_perror_msg_and_die("chsid(%s, %s) failed",
426 full_tty, new_tty_sid);
430 /* Try these, but don't complain if they fail.
431 * _f_chown is safe wrt race t=ttyname(0);...;chown(t); */
432 fchown(0, pw->pw_uid, pw->pw_gid);
435 /* We trust environment only if we run by root */
436 if (ENABLE_LOGIN_SCRIPTS && amroot) {
439 t_argv[0] = getenv("LOGIN_PRE_SUID_SCRIPT");
442 xsetenv("LOGIN_TTY", full_tty);
443 xsetenv("LOGIN_USER", pw->pw_name);
444 xsetenv("LOGIN_UID", utoa(pw->pw_uid));
445 xsetenv("LOGIN_GID", utoa(pw->pw_gid));
446 xsetenv("LOGIN_SHELL", pw->pw_shell);
447 spawn_and_wait(t_argv); /* NOMMU-friendly */
448 unsetenv("LOGIN_TTY" );
449 unsetenv("LOGIN_USER" );
450 unsetenv("LOGIN_UID" );
451 unsetenv("LOGIN_GID" );
452 unsetenv("LOGIN_SHELL");
460 /* setup_environment params: shell, clear_env, change_env, pw */
461 setup_environment(tmp, !(opt & LOGIN_OPT_p), 1, pw);
466 syslog(LOG_INFO, "root login%s", fromhost);
468 /* well, a simple setexeccon() here would do the job as well,
469 * but let's play the game for now */
470 set_current_security_context(user_sid);
473 // util-linux login also does:
474 // /* start new session */
476 // /* TIOCSCTTY: steal tty from other process group */
477 // if (ioctl(0, TIOCSCTTY, 1)) error_msg...
478 // BBox login used to do this (see above):
480 // If this stuff is really needed, add it and explain why!
482 /* set signals to defaults */
483 signal(SIGALRM, SIG_DFL);
484 /* Is this correct? This way user can ctrl-c out of /etc/profile,
485 * potentially creating security breach (tested with bash 3.0).
486 * But without this, bash 3.0 will not enable ctrl-c either.
487 * Maybe bash is buggy?
488 * Need to find out what standards say about /bin/login -
489 * should it leave SIGINT etc enabled or disabled? */
490 signal(SIGINT, SIG_DFL);
492 /* Exec login shell with no additional parameters */
493 run_shell(tmp, 1, NULL, NULL);
495 /* return EXIT_FAILURE; - not reached */