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_time = 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_time = 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("/etc/nologin", "r");
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)
146 fp = fopen("/etc/securetty", "r");
148 /* A missing securetty file is not an error. */
151 while (fgets(buf, sizeof(buf)-1, fp)) {
152 for (i = strlen(buf)-1; i >= 0; --i) {
153 if (!isspace(buf[i]))
157 if (!buf[0] || (buf[0] == '#'))
159 if (strcmp(buf, short_tty) == 0) {
168 static ALWAYS_INLINE int check_securetty(void) { return 1; }
171 static void get_username_or_die(char *buf, int size_buf)
175 cntdown = EMPTY_USERNAME_COUNT;
177 print_login_prompt();
178 /* skip whitespace */
181 if (c == EOF) exit(1);
183 if (!--cntdown) exit(1);
186 } while (isspace(c));
189 if (!fgets(buf, size_buf-2, stdin))
191 if (!strchr(buf, '\n'))
193 while (isgraph(*buf)) buf++;
197 static void motd(void)
201 fd = open(bb_path_motd_file, O_RDONLY);
204 bb_copyfd_eof(fd, STDOUT_FILENO);
209 static void alarm_handler(int sig ATTRIBUTE_UNUSED)
211 /* This is the escape hatch! Poor serial line users and the like
212 * arrive here when their connection is broken.
213 * We don't want to block here */
215 printf("\r\nLogin timed out after %d seconds\r\n", TIMEOUT);
217 /* unix API is brain damaged regarding O_NONBLOCK,
218 * we should undo it, or else we can affect other processes */
223 int login_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
224 int login_main(int argc ATTRIBUTE_UNUSED, char **argv)
227 LOGIN_OPT_f = (1<<0),
228 LOGIN_OPT_h = (1<<1),
229 LOGIN_OPT_p = (1<<2),
232 char username[USERNAME_SIZE];
238 char *opt_host = opt_host; /* for compiler */
239 char *opt_user = opt_user; /* for compiler */
240 char full_tty[TTYNAME_SIZE];
241 USE_SELINUX(security_context_t user_sid = NULL;)
242 USE_FEATURE_UTMP(struct utmp utent;)
247 const char *failed_msg;
248 struct passwd pwdstruct;
252 short_tty = full_tty;
254 signal(SIGALRM, alarm_handler);
257 /* More of suid paranoia if called by non-root */
258 amroot = !sanitize_env_if_suid(); /* Clear dangerous stuff, set PATH */
260 /* Mandatory paranoia for suid applet:
261 * ensure that fd# 0,1,2 are opened (at least to /dev/null)
262 * and any extra open fd's are closed.
263 * (The name of the function is misleading. Not daemonizing here.) */
264 bb_daemonize_or_rexec(DAEMON_ONLY_SANITIZE | DAEMON_CLOSE_EXTRA_FDS, NULL);
266 opt = getopt32(argv, "f:h:p", &opt_user, &opt_host);
267 if (opt & LOGIN_OPT_f) {
269 bb_error_msg_and_die("-f is for root only");
270 safe_strncpy(username, opt_user, sizeof(username));
273 if (argv[0]) /* user from command line (getty) */
274 safe_strncpy(username, argv[0], sizeof(username));
276 /* Let's find out and memorize our tty */
277 if (!isatty(0) || !isatty(1) || !isatty(2))
278 return EXIT_FAILURE; /* Must be a terminal */
279 safe_strncpy(full_tty, "UNKNOWN", sizeof(full_tty));
282 safe_strncpy(full_tty, tmp, sizeof(full_tty));
283 if (strncmp(full_tty, "/dev/", 5) == 0)
284 short_tty = full_tty + 5;
287 read_or_build_utent(&utent, !amroot);
289 if (opt & LOGIN_OPT_h) {
291 safe_strncpy(utent.ut_host, opt_host, sizeof(utent.ut_host));
293 fromhost = xasprintf(" on '%s' from '%s'", short_tty, opt_host);
295 fromhost = xasprintf(" on '%s'", short_tty);
297 /* Was breaking "login <username>" from shell command line: */
300 openlog(applet_name, LOG_PID | LOG_CONS | LOG_NOWAIT, LOG_AUTH);
303 /* flush away any type-ahead (as getty does) */
304 ioctl(0, TCFLSH, TCIFLUSH);
307 get_username_or_die(username, sizeof(username));
310 pamret = pam_start("login", username, &conv, &pamh);
311 if (pamret != PAM_SUCCESS) {
312 failed_msg = "start";
313 goto pam_auth_failed;
315 /* set TTY (so things like securetty work) */
316 pamret = pam_set_item(pamh, PAM_TTY, short_tty);
317 if (pamret != PAM_SUCCESS) {
318 failed_msg = "set_item(TTY)";
319 goto pam_auth_failed;
321 pamret = pam_authenticate(pamh, 0);
322 if (pamret != PAM_SUCCESS) {
323 failed_msg = "authenticate";
324 goto pam_auth_failed;
325 /* TODO: or just "goto auth_failed"
326 * since user seems to enter wrong password
327 * (in this case pamret == 7)
330 /* check that the account is healthy */
331 pamret = pam_acct_mgmt(pamh, 0);
332 if (pamret != PAM_SUCCESS) {
333 failed_msg = "acct_mgmt";
334 goto pam_auth_failed;
338 /* gcc: "dereferencing type-punned pointer breaks aliasing rules..."
339 * thus we cast to (void*) */
340 if (pam_get_item(pamh, PAM_USER, (void*)&pamuser) != PAM_SUCCESS) {
341 failed_msg = "get_item(USER)";
342 goto pam_auth_failed;
344 if (!pamuser || !pamuser[0])
346 safe_strncpy(username, pamuser, sizeof(username));
347 /* Don't use "pw = getpwnam(username);",
348 * PAM is said to be capable of destroying static storage
349 * used by getpwnam(). We are using safe(r) function */
351 getpwnam_r(username, &pwdstruct, pwdbuf, sizeof(pwdbuf), &pw);
354 pamret = pam_open_session(pamh, 0);
355 if (pamret != PAM_SUCCESS) {
356 failed_msg = "open_session";
357 goto pam_auth_failed;
359 pamret = pam_setcred(pamh, PAM_ESTABLISH_CRED);
360 if (pamret != PAM_SUCCESS) {
361 failed_msg = "setcred";
362 goto pam_auth_failed;
364 break; /* success, continue login process */
367 bb_error_msg("pam_%s call failed: %s (%d)", failed_msg,
368 pam_strerror(pamh, pamret), pamret);
369 safe_strncpy(username, "UNKNOWN", sizeof(username));
371 pw = getpwnam(username);
373 strcpy(username, "UNKNOWN");
377 if (pw->pw_passwd[0] == '!' || pw->pw_passwd[0] == '*')
380 if (opt & LOGIN_OPT_f)
381 break; /* -f USER: success without asking passwd */
383 if (pw->pw_uid == 0 && !check_securetty())
386 /* Don't check the password if password entry is empty (!) */
387 if (!pw->pw_passwd[0])
390 /* authorization takes place here */
391 if (correct_password(pw))
393 #endif /* ENABLE_PAM */
396 bb_do_delay(FAIL_DELAY);
397 /* TODO: doesn't sound like correct English phrase to me */
398 puts("Login incorrect");
400 syslog(LOG_WARNING, "invalid password for '%s'%s",
411 write_utent(&utent, username);
414 if (is_selinux_enabled()) {
415 security_context_t old_tty_sid, new_tty_sid;
417 if (get_default_context(username, NULL, &user_sid)) {
418 bb_error_msg_and_die("cannot get SID for %s",
421 if (getfilecon(full_tty, &old_tty_sid) < 0) {
422 bb_perror_msg_and_die("getfilecon(%s) failed",
425 if (security_compute_relabel(user_sid, old_tty_sid,
426 SECCLASS_CHR_FILE, &new_tty_sid) != 0) {
427 bb_perror_msg_and_die("security_change_sid(%s) failed",
430 if (setfilecon(full_tty, new_tty_sid) != 0) {
431 bb_perror_msg_and_die("chsid(%s, %s) failed",
432 full_tty, new_tty_sid);
436 /* Try these, but don't complain if they fail.
437 * _f_chown is safe wrt race t=ttyname(0);...;chown(t); */
438 fchown(0, pw->pw_uid, pw->pw_gid);
441 /* We trust environment only if we run by root */
442 if (ENABLE_LOGIN_SCRIPTS && amroot) {
445 t_argv[0] = getenv("LOGIN_PRE_SUID_SCRIPT");
448 xsetenv("LOGIN_TTY", full_tty);
449 xsetenv("LOGIN_USER", pw->pw_name);
450 xsetenv("LOGIN_UID", utoa(pw->pw_uid));
451 xsetenv("LOGIN_GID", utoa(pw->pw_gid));
452 xsetenv("LOGIN_SHELL", pw->pw_shell);
453 spawn_and_wait(t_argv); /* NOMMU-friendly */
454 unsetenv("LOGIN_TTY" );
455 unsetenv("LOGIN_USER" );
456 unsetenv("LOGIN_UID" );
457 unsetenv("LOGIN_GID" );
458 unsetenv("LOGIN_SHELL");
466 /* setup_environment params: shell, clear_env, change_env, pw */
467 setup_environment(tmp, !(opt & LOGIN_OPT_p), 1, pw);
472 syslog(LOG_INFO, "root login%s", fromhost);
474 /* well, a simple setexeccon() here would do the job as well,
475 * but let's play the game for now */
476 set_current_security_context(user_sid);
479 // util-linux login also does:
480 // /* start new session */
482 // /* TIOCSCTTY: steal tty from other process group */
483 // if (ioctl(0, TIOCSCTTY, 1)) error_msg...
484 // BBox login used to do this (see above):
486 // If this stuff is really needed, add it and explain why!
488 /* set signals to defaults */
489 signal(SIGALRM, SIG_DFL);
490 /* Is this correct? This way user can ctrl-c out of /etc/profile,
491 * potentially creating security breach (tested with bash 3.0).
492 * But without this, bash 3.0 will not enable ctrl-c either.
493 * Maybe bash is buggy?
494 * Need to find out what standards say about /bin/login -
495 * should it leave SIGINT etc enabled or disabled? */
496 signal(SIGINT, SIG_DFL);
498 /* Exec login shell with no additional parameters */
499 run_shell(tmp, 1, NULL, NULL);
501 /* return EXIT_FAILURE; - not reached */