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)
122 if (access("/etc/nologin", F_OK))
125 fp = fopen_for_read("/etc/nologin");
127 while ((c = getc(fp)) != EOF)
128 bb_putchar((c=='\n') ? '\r' : c);
132 puts("\r\nSystem closed for routine maintenance\r");
136 static ALWAYS_INLINE void die_if_nologin(void) {}
139 #if ENABLE_FEATURE_SECURETTY && !ENABLE_PAM
140 static int check_securetty(void)
142 char *buf = (char*)"/etc/securetty"; /* any non-NULL is ok */
143 parser_t *parser = config_open2("/etc/securetty", fopen_for_read);
144 while (config_read(parser, &buf, 1, 1, "# \t", PARSE_NORMAL)) {
145 if (strcmp(buf, short_tty) == 0)
149 config_close(parser);
150 /* buf != NULL here if config file was not found, empty
151 * or line was found which equals short_tty */
155 static ALWAYS_INLINE int check_securetty(void) { return 1; }
158 static void get_username_or_die(char *buf, int size_buf)
162 cntdown = EMPTY_USERNAME_COUNT;
164 print_login_prompt();
165 /* skip whitespace */
168 if (c == EOF) exit(EXIT_FAILURE);
170 if (!--cntdown) exit(EXIT_FAILURE);
173 } while (isspace(c));
176 if (!fgets(buf, size_buf-2, stdin))
178 if (!strchr(buf, '\n'))
180 while (isgraph(*buf)) buf++;
184 static void motd(void)
188 fd = open(bb_path_motd_file, O_RDONLY);
191 bb_copyfd_eof(fd, STDOUT_FILENO);
196 static void alarm_handler(int sig UNUSED_PARAM)
198 /* This is the escape hatch! Poor serial line users and the like
199 * arrive here when their connection is broken.
200 * We don't want to block here */
202 printf("\r\nLogin timed out after %d seconds\r\n", TIMEOUT);
204 /* unix API is brain damaged regarding O_NONBLOCK,
205 * we should undo it, or else we can affect other processes */
210 int login_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
211 int login_main(int argc UNUSED_PARAM, char **argv)
214 LOGIN_OPT_f = (1<<0),
215 LOGIN_OPT_h = (1<<1),
216 LOGIN_OPT_p = (1<<2),
219 char username[USERNAME_SIZE];
225 char *opt_host = opt_host; /* for compiler */
226 char *opt_user = opt_user; /* for compiler */
227 char full_tty[TTYNAME_SIZE];
228 USE_SELINUX(security_context_t user_sid = NULL;)
229 USE_FEATURE_UTMP(struct utmp utent;)
234 const char *failed_msg;
235 struct passwd pwdstruct;
239 short_tty = full_tty;
241 signal(SIGALRM, alarm_handler);
244 /* More of suid paranoia if called by non-root */
245 amroot = !sanitize_env_if_suid(); /* Clear dangerous stuff, set PATH */
247 /* Mandatory paranoia for suid applet:
248 * ensure that fd# 0,1,2 are opened (at least to /dev/null)
249 * and any extra open fd's are closed.
250 * (The name of the function is misleading. Not daemonizing here.) */
251 bb_daemonize_or_rexec(DAEMON_ONLY_SANITIZE | DAEMON_CLOSE_EXTRA_FDS, NULL);
253 opt = getopt32(argv, "f:h:p", &opt_user, &opt_host);
254 if (opt & LOGIN_OPT_f) {
256 bb_error_msg_and_die("-f is for root only");
257 safe_strncpy(username, opt_user, sizeof(username));
260 if (argv[0]) /* user from command line (getty) */
261 safe_strncpy(username, argv[0], sizeof(username));
263 /* Let's find out and memorize our tty */
264 if (!isatty(0) || !isatty(1) || !isatty(2))
265 return EXIT_FAILURE; /* Must be a terminal */
266 safe_strncpy(full_tty, "UNKNOWN", sizeof(full_tty));
269 safe_strncpy(full_tty, tmp, sizeof(full_tty));
270 if (strncmp(full_tty, "/dev/", 5) == 0)
271 short_tty = full_tty + 5;
274 read_or_build_utent(&utent, !amroot);
276 if (opt & LOGIN_OPT_h) {
278 safe_strncpy(utent.ut_host, opt_host, sizeof(utent.ut_host));
280 fromhost = xasprintf(" on '%s' from '%s'", short_tty, opt_host);
282 fromhost = xasprintf(" on '%s'", short_tty);
284 /* Was breaking "login <username>" from shell command line: */
287 openlog(applet_name, LOG_PID | LOG_CONS | LOG_NOWAIT, LOG_AUTH);
290 /* flush away any type-ahead (as getty does) */
291 ioctl(0, TCFLSH, TCIFLUSH);
294 get_username_or_die(username, sizeof(username));
297 pamret = pam_start("login", username, &conv, &pamh);
298 if (pamret != PAM_SUCCESS) {
299 failed_msg = "start";
300 goto pam_auth_failed;
302 /* set TTY (so things like securetty work) */
303 pamret = pam_set_item(pamh, PAM_TTY, short_tty);
304 if (pamret != PAM_SUCCESS) {
305 failed_msg = "set_item(TTY)";
306 goto pam_auth_failed;
308 pamret = pam_authenticate(pamh, 0);
309 if (pamret != PAM_SUCCESS) {
310 failed_msg = "authenticate";
311 goto pam_auth_failed;
312 /* TODO: or just "goto auth_failed"
313 * since user seems to enter wrong password
314 * (in this case pamret == 7)
317 /* check that the account is healthy */
318 pamret = pam_acct_mgmt(pamh, 0);
319 if (pamret != PAM_SUCCESS) {
320 failed_msg = "acct_mgmt";
321 goto pam_auth_failed;
325 /* gcc: "dereferencing type-punned pointer breaks aliasing rules..."
326 * thus we cast to (void*) */
327 if (pam_get_item(pamh, PAM_USER, (void*)&pamuser) != PAM_SUCCESS) {
328 failed_msg = "get_item(USER)";
329 goto pam_auth_failed;
331 if (!pamuser || !pamuser[0])
333 safe_strncpy(username, pamuser, sizeof(username));
334 /* Don't use "pw = getpwnam(username);",
335 * PAM is said to be capable of destroying static storage
336 * used by getpwnam(). We are using safe(r) function */
338 getpwnam_r(username, &pwdstruct, pwdbuf, sizeof(pwdbuf), &pw);
341 pamret = pam_open_session(pamh, 0);
342 if (pamret != PAM_SUCCESS) {
343 failed_msg = "open_session";
344 goto pam_auth_failed;
346 pamret = pam_setcred(pamh, PAM_ESTABLISH_CRED);
347 if (pamret != PAM_SUCCESS) {
348 failed_msg = "setcred";
349 goto pam_auth_failed;
351 break; /* success, continue login process */
354 bb_error_msg("pam_%s call failed: %s (%d)", failed_msg,
355 pam_strerror(pamh, pamret), pamret);
356 safe_strncpy(username, "UNKNOWN", sizeof(username));
358 pw = getpwnam(username);
360 strcpy(username, "UNKNOWN");
364 if (pw->pw_passwd[0] == '!' || pw->pw_passwd[0] == '*')
367 if (opt & LOGIN_OPT_f)
368 break; /* -f USER: success without asking passwd */
370 if (pw->pw_uid == 0 && !check_securetty())
373 /* Don't check the password if password entry is empty (!) */
374 if (!pw->pw_passwd[0])
377 /* authorization takes place here */
378 if (correct_password(pw))
380 #endif /* ENABLE_PAM */
383 bb_do_delay(FAIL_DELAY);
384 /* TODO: doesn't sound like correct English phrase to me */
385 puts("Login incorrect");
387 syslog(LOG_WARNING, "invalid password for '%s'%s",
398 write_utent(&utent, username);
401 if (is_selinux_enabled()) {
402 security_context_t old_tty_sid, new_tty_sid;
404 if (get_default_context(username, NULL, &user_sid)) {
405 bb_error_msg_and_die("cannot get SID for %s",
408 if (getfilecon(full_tty, &old_tty_sid) < 0) {
409 bb_perror_msg_and_die("getfilecon(%s) failed",
412 if (security_compute_relabel(user_sid, old_tty_sid,
413 SECCLASS_CHR_FILE, &new_tty_sid) != 0) {
414 bb_perror_msg_and_die("security_change_sid(%s) failed",
417 if (setfilecon(full_tty, new_tty_sid) != 0) {
418 bb_perror_msg_and_die("chsid(%s, %s) failed",
419 full_tty, new_tty_sid);
423 /* Try these, but don't complain if they fail.
424 * _f_chown is safe wrt race t=ttyname(0);...;chown(t); */
425 fchown(0, pw->pw_uid, pw->pw_gid);
428 /* We trust environment only if we run by root */
429 if (ENABLE_LOGIN_SCRIPTS && amroot) {
432 t_argv[0] = getenv("LOGIN_PRE_SUID_SCRIPT");
435 xsetenv("LOGIN_TTY", full_tty);
436 xsetenv("LOGIN_USER", pw->pw_name);
437 xsetenv("LOGIN_UID", utoa(pw->pw_uid));
438 xsetenv("LOGIN_GID", utoa(pw->pw_gid));
439 xsetenv("LOGIN_SHELL", pw->pw_shell);
440 spawn_and_wait(t_argv); /* NOMMU-friendly */
441 unsetenv("LOGIN_TTY" );
442 unsetenv("LOGIN_USER" );
443 unsetenv("LOGIN_UID" );
444 unsetenv("LOGIN_GID" );
445 unsetenv("LOGIN_SHELL");
453 /* setup_environment params: shell, clear_env, change_env, pw */
454 setup_environment(tmp, !(opt & LOGIN_OPT_p), 1, pw);
459 syslog(LOG_INFO, "root login%s", fromhost);
461 /* well, a simple setexeccon() here would do the job as well,
462 * but let's play the game for now */
463 set_current_security_context(user_sid);
466 // util-linux login also does:
467 // /* start new session */
469 // /* TIOCSCTTY: steal tty from other process group */
470 // if (ioctl(0, TIOCSCTTY, 1)) error_msg...
471 // BBox login used to do this (see above):
473 // If this stuff is really needed, add it and explain why!
475 /* set signals to defaults */
476 signal(SIGALRM, SIG_DFL);
477 /* Is this correct? This way user can ctrl-c out of /etc/profile,
478 * potentially creating security breach (tested with bash 3.0).
479 * But without this, bash 3.0 will not enable ctrl-c either.
480 * Maybe bash is buggy?
481 * Need to find out what standards say about /bin/login -
482 * should it leave SIGINT etc enabled or disabled? */
483 signal(SIGINT, SIG_DFL);
485 /* Exec login shell with no additional parameters */
486 run_shell(tmp, 1, NULL, NULL);
488 /* return EXIT_FAILURE; - not reached */