1 /* vi: set sw=4 ts=4: */
3 * Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
7 #if ENABLE_FEATURE_UTMP
8 # include <utmp.h> /* USER_PROCESS */
10 #include <sys/resource.h>
13 # include <selinux/selinux.h> /* for is_selinux_enabled() */
14 # include <selinux/get_context_list.h> /* for get_default_context() */
15 # include <selinux/flask.h> /* for security class definitions */
19 /* PAM may include <locale.h>. We may need to undefine bbox's stub define: */
21 /* For some obscure reason, PAM is not in pam/xxx, but in security/xxx.
22 * Apparently they like to confuse people. */
23 # include <security/pam_appl.h>
24 # include <security/pam_misc.h>
25 static const struct pam_conv conv = {
33 EMPTY_USERNAME_COUNT = 10,
38 static char* short_tty;
40 #if ENABLE_FEATURE_NOLOGIN
41 static void die_if_nologin(void)
47 fp = fopen_for_read("/etc/nologin");
48 if (!fp) /* assuming it does not exist */
51 while ((c = getc(fp)) != EOF) {
58 puts("\r\nSystem closed for routine maintenance\r");
62 /* Users say that they do need this prior to exit: */
63 tcdrain(STDOUT_FILENO);
67 # define die_if_nologin() ((void)0)
70 #if ENABLE_FEATURE_SECURETTY && !ENABLE_PAM
71 static int check_securetty(void)
73 char *buf = (char*)"/etc/securetty"; /* any non-NULL is ok */
74 parser_t *parser = config_open2("/etc/securetty", fopen_for_read);
75 while (config_read(parser, &buf, 1, 1, "# \t", PARSE_NORMAL)) {
76 if (strcmp(buf, short_tty) == 0)
81 /* buf != NULL here if config file was not found, empty
82 * or line was found which equals short_tty */
86 static ALWAYS_INLINE int check_securetty(void) { return 1; }
90 static void initselinux(char *username, char *full_tty,
91 security_context_t *user_sid)
93 security_context_t old_tty_sid, new_tty_sid;
95 if (!is_selinux_enabled())
98 if (get_default_context(username, NULL, user_sid)) {
99 bb_error_msg_and_die("can't get SID for %s", username);
101 if (getfilecon(full_tty, &old_tty_sid) < 0) {
102 bb_perror_msg_and_die("getfilecon(%s) failed", full_tty);
104 if (security_compute_relabel(*user_sid, old_tty_sid,
105 SECCLASS_CHR_FILE, &new_tty_sid) != 0) {
106 bb_perror_msg_and_die("security_change_sid(%s) failed", full_tty);
108 if (setfilecon(full_tty, new_tty_sid) != 0) {
109 bb_perror_msg_and_die("chsid(%s, %s) failed", full_tty, new_tty_sid);
114 #if ENABLE_LOGIN_SCRIPTS
115 static void run_login_script(struct passwd *pw, char *full_tty)
119 t_argv[0] = getenv("LOGIN_PRE_SUID_SCRIPT");
122 xsetenv("LOGIN_TTY", full_tty);
123 xsetenv("LOGIN_USER", pw->pw_name);
124 xsetenv("LOGIN_UID", utoa(pw->pw_uid));
125 xsetenv("LOGIN_GID", utoa(pw->pw_gid));
126 xsetenv("LOGIN_SHELL", pw->pw_shell);
127 spawn_and_wait(t_argv); /* NOMMU-friendly */
128 unsetenv("LOGIN_TTY");
129 unsetenv("LOGIN_USER");
130 unsetenv("LOGIN_UID");
131 unsetenv("LOGIN_GID");
132 unsetenv("LOGIN_SHELL");
136 void run_login_script(struct passwd *pw, char *full_tty);
139 static void get_username_or_die(char *buf, int size_buf)
143 cntdown = EMPTY_USERNAME_COUNT;
145 print_login_prompt();
146 /* skip whitespace */
156 } while (isspace(c)); /* maybe isblank? */
159 if (!fgets(buf, size_buf-2, stdin))
161 if (!strchr(buf, '\n'))
163 while ((unsigned char)*buf > ' ')
168 static void motd(void)
172 fd = open(bb_path_motd_file, O_RDONLY);
175 bb_copyfd_eof(fd, STDOUT_FILENO);
180 static void alarm_handler(int sig UNUSED_PARAM)
182 /* This is the escape hatch! Poor serial line users and the like
183 * arrive here when their connection is broken.
184 * We don't want to block here */
186 printf("\r\nLogin timed out after %d seconds\r\n", TIMEOUT);
188 /* unix API is brain damaged regarding O_NONBLOCK,
189 * we should undo it, or else we can affect other processes */
194 int login_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
195 int login_main(int argc UNUSED_PARAM, char **argv)
198 LOGIN_OPT_f = (1<<0),
199 LOGIN_OPT_h = (1<<1),
200 LOGIN_OPT_p = (1<<2),
203 char username[USERNAME_SIZE];
209 char *opt_host = NULL;
210 char *opt_user = opt_user; /* for compiler */
212 IF_SELINUX(security_context_t user_sid = NULL;)
217 const char *failed_msg;
218 struct passwd pwdstruct;
223 signal(SIGALRM, alarm_handler);
226 /* More of suid paranoia if called by non-root: */
227 /* Clear dangerous stuff, set PATH */
228 run_by_root = !sanitize_env_if_suid();
230 /* Mandatory paranoia for suid applet:
231 * ensure that fd# 0,1,2 are opened (at least to /dev/null)
232 * and any extra open fd's are closed.
233 * (The name of the function is misleading. Not daemonizing here.) */
234 bb_daemonize_or_rexec(DAEMON_ONLY_SANITIZE | DAEMON_CLOSE_EXTRA_FDS, NULL);
236 opt = getopt32(argv, "f:h:p", &opt_user, &opt_host);
237 if (opt & LOGIN_OPT_f) {
239 bb_error_msg_and_die("-f is for root only");
240 safe_strncpy(username, opt_user, sizeof(username));
243 if (argv[0]) /* user from command line (getty) */
244 safe_strncpy(username, argv[0], sizeof(username));
246 /* Let's find out and memorize our tty */
247 if (!isatty(STDIN_FILENO) || !isatty(STDOUT_FILENO) || !isatty(STDERR_FILENO))
248 return EXIT_FAILURE; /* Must be a terminal */
249 full_tty = xmalloc_ttyname(STDIN_FILENO);
251 full_tty = xstrdup("UNKNOWN");
252 short_tty = full_tty;
253 if (strncmp(full_tty, "/dev/", 5) == 0)
257 fromhost = xasprintf(" on '%s' from '%s'", short_tty, opt_host);
259 fromhost = xasprintf(" on '%s'", short_tty);
262 /* Was breaking "login <username>" from shell command line: */
265 openlog(applet_name, LOG_PID | LOG_CONS, LOG_AUTH);
268 /* flush away any type-ahead (as getty does) */
269 ioctl(0, TCFLSH, TCIFLUSH);
272 get_username_or_die(username, sizeof(username));
275 pamret = pam_start("login", username, &conv, &pamh);
276 if (pamret != PAM_SUCCESS) {
277 failed_msg = "start";
278 goto pam_auth_failed;
280 /* set TTY (so things like securetty work) */
281 pamret = pam_set_item(pamh, PAM_TTY, short_tty);
282 if (pamret != PAM_SUCCESS) {
283 failed_msg = "set_item(TTY)";
284 goto pam_auth_failed;
286 pamret = pam_authenticate(pamh, 0);
287 if (pamret != PAM_SUCCESS) {
288 failed_msg = "authenticate";
289 goto pam_auth_failed;
290 /* TODO: or just "goto auth_failed"
291 * since user seems to enter wrong password
292 * (in this case pamret == 7)
295 /* check that the account is healthy */
296 pamret = pam_acct_mgmt(pamh, 0);
297 if (pamret != PAM_SUCCESS) {
298 failed_msg = "acct_mgmt";
299 goto pam_auth_failed;
303 /* gcc: "dereferencing type-punned pointer breaks aliasing rules..."
304 * thus we cast to (void*) */
305 if (pam_get_item(pamh, PAM_USER, (void*)&pamuser) != PAM_SUCCESS) {
306 failed_msg = "get_item(USER)";
307 goto pam_auth_failed;
309 if (!pamuser || !pamuser[0])
311 safe_strncpy(username, pamuser, sizeof(username));
312 /* Don't use "pw = getpwnam(username);",
313 * PAM is said to be capable of destroying static storage
314 * used by getpwnam(). We are using safe(r) function */
316 getpwnam_r(username, &pwdstruct, pwdbuf, sizeof(pwdbuf), &pw);
319 pamret = pam_open_session(pamh, 0);
320 if (pamret != PAM_SUCCESS) {
321 failed_msg = "open_session";
322 goto pam_auth_failed;
324 pamret = pam_setcred(pamh, PAM_ESTABLISH_CRED);
325 if (pamret != PAM_SUCCESS) {
326 failed_msg = "setcred";
327 goto pam_auth_failed;
329 break; /* success, continue login process */
332 /* syslog, because we don't want potential attacker
333 * to know _why_ login failed */
334 syslog(LOG_WARNING, "pam_%s call failed: %s (%d)", failed_msg,
335 pam_strerror(pamh, pamret), pamret);
336 safe_strncpy(username, "UNKNOWN", sizeof(username));
338 pw = getpwnam(username);
340 strcpy(username, "UNKNOWN");
344 if (pw->pw_passwd[0] == '!' || pw->pw_passwd[0] == '*')
347 if (opt & LOGIN_OPT_f)
348 break; /* -f USER: success without asking passwd */
350 if (pw->pw_uid == 0 && !check_securetty())
353 /* Don't check the password if password entry is empty (!) */
354 if (!pw->pw_passwd[0])
357 /* authorization takes place here */
358 if (correct_password(pw))
360 #endif /* ENABLE_PAM */
363 bb_do_delay(FAIL_DELAY);
364 /* TODO: doesn't sound like correct English phrase to me */
365 puts("Login incorrect");
367 syslog(LOG_WARNING, "invalid password for '%s'%s",
375 /* We can ignore /etc/nologin if we are logging in as root,
376 * it doesn't matter whether we are run by root or not */
380 IF_SELINUX(initselinux(username, full_tty, &user_sid));
382 /* Try these, but don't complain if they fail.
383 * _f_chown is safe wrt race t=ttyname(0);...;chown(t); */
384 fchown(0, pw->pw_uid, pw->pw_gid);
387 update_utmp(USER_PROCESS, short_tty, username, run_by_root ? opt_host : NULL);
389 /* We trust environment only if we run by root */
390 if (ENABLE_LOGIN_SCRIPTS && run_by_root)
391 run_login_script(pw, full_tty);
397 setup_environment(tmp,
398 (!(opt & LOGIN_OPT_p) * SETUP_ENV_CLEARENV) + SETUP_ENV_CHANGEENV,
404 syslog(LOG_INFO, "root login%s", fromhost);
406 /* well, a simple setexeccon() here would do the job as well,
407 * but let's play the game for now */
408 IF_SELINUX(set_current_security_context(user_sid);)
410 // util-linux login also does:
411 // /* start new session */
413 // /* TIOCSCTTY: steal tty from other process group */
414 // if (ioctl(0, TIOCSCTTY, 1)) error_msg...
415 // BBox login used to do this (see above):
417 // If this stuff is really needed, add it and explain why!
419 /* Set signals to defaults */
420 /* Non-ignored signals revert to SIG_DFL on exec anyway */
421 /*signal(SIGALRM, SIG_DFL);*/
423 /* Is this correct? This way user can ctrl-c out of /etc/profile,
424 * potentially creating security breach (tested with bash 3.0).
425 * But without this, bash 3.0 will not enable ctrl-c either.
426 * Maybe bash is buggy?
427 * Need to find out what standards say about /bin/login -
428 * should we leave SIGINT etc enabled or disabled? */
429 signal(SIGINT, SIG_DFL);
431 /* Exec login shell with no additional parameters */
432 run_shell(tmp, 1, NULL, NULL);
434 /* return EXIT_FAILURE; - not reached */