busybox/loginutils/login.c

/* vi: set sw=4 ts=4: */
/*
 * Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
 */

#include "libbb.h"
#include <syslog.h>
#include <utmp.h>
#include <sys/resource.h>

#if ENABLE_SELINUX
#include <selinux/selinux.h>  /* for is_selinux_enabled()  */
#include <selinux/get_context_list.h> /* for get_default_context() */
#include <selinux/flask.h> /* for security class definitions  */
#endif

#if ENABLE_PAM
/* PAM may include <locale.h>. We may need to undefine bbox's stub define: */
#undef setlocale
/* For some obscure reason, PAM is not in pam/xxx, but in security/xxx.
 * Apparently they like to confuse people. */
#include <security/pam_appl.h>
#include <security/pam_misc.h>
static const struct pam_conv conv = {
	misc_conv,
	NULL
};
#endif

enum {
	TIMEOUT = 60,
	EMPTY_USERNAME_COUNT = 10,
	USERNAME_SIZE = 32,
	TTYNAME_SIZE = 32,
};

static char* short_tty;

#if ENABLE_FEATURE_UTMP
/* vv  Taken from tinylogin utmp.c  vv */
/*
 * read_or_build_utent - see if utmp file is correct for this process
 *
 *	System V is very picky about the contents of the utmp file
 *	and requires that a slot for the current process exist.
 *	The utmp file is scanned for an entry with the same process
 *	ID.  If no entry exists the process exits with a message.
 *
 *	The "picky" flag is for network and other logins that may
 *	use special flags.  It allows the pid checks to be overridden.
 *	This means that getty should never invoke login with any
 *	command line flags.
 */

static void read_or_build_utent(struct utmp *utptr, int run_by_root)
{
	struct utmp *ut;
	pid_t pid = getpid();

	setutent();

	/* First, try to find a valid utmp entry for this process.  */
	/* If there is one, just use it.  */
	while ((ut = getutent()) != NULL)
		if (ut->ut_pid == pid && ut->ut_line[0] && ut->ut_id[0]
		 && (ut->ut_type == LOGIN_PROCESS || ut->ut_type == USER_PROCESS)
		) {
			*utptr = *ut; /* struct copy */
			if (run_by_root) /* why only for root? */
				memset(utptr->ut_host, 0, sizeof(utptr->ut_host));
			return;
		}

// Why? Do we require non-root to exec login from another
// former login process (e.g. login shell)? Some login's have
// login shells as children, so it won't work...
//	if (!run_by_root)
//		bb_error_msg_and_die("no utmp entry found");

	/* Otherwise create a new one.  */
	memset(utptr, 0, sizeof(*utptr));
	utptr->ut_type = LOGIN_PROCESS;
	utptr->ut_pid = pid;
	strncpy(utptr->ut_line, short_tty, sizeof(utptr->ut_line));
	/* This one is only 4 chars wide. Try to fit something
	 * remotely meaningful by skipping "tty"... */
	strncpy(utptr->ut_id, short_tty + 3, sizeof(utptr->ut_id));
	strncpy(utptr->ut_user, "LOGIN", sizeof(utptr->ut_user));
	utptr->ut_tv.tv_sec = time(NULL);
}

/*
 * write_utent - put a USER_PROCESS entry in the utmp file
 *
 *	write_utent changes the type of the current utmp entry to
 *	USER_PROCESS.  the wtmp file will be updated as well.
 */
static void write_utent(struct utmp *utptr, const char *username)
{
	utptr->ut_type = USER_PROCESS;
	strncpy(utptr->ut_user, username, sizeof(utptr->ut_user));
	utptr->ut_tv.tv_sec = time(NULL);
	/* other fields already filled in by read_or_build_utent above */
	setutent();
	pututline(utptr);
	endutent();
#if ENABLE_FEATURE_WTMP
	if (access(bb_path_wtmp_file, R_OK|W_OK) == -1) {
		close(creat(bb_path_wtmp_file, 0664));
	}
	updwtmp(bb_path_wtmp_file, utptr);
#endif
}
#else /* !ENABLE_FEATURE_UTMP */
#define read_or_build_utent(utptr, run_by_root) ((void)0)
#define write_utent(utptr, username) ((void)0)
#endif /* !ENABLE_FEATURE_UTMP */

#if ENABLE_FEATURE_NOLOGIN
static void die_if_nologin(void)
{
	FILE *fp;
	int c;
	int empty = 1;

	fp = fopen_for_read("/etc/nologin");
	if (!fp) /* assuming it does not exist */
		return;

	while ((c = getc(fp)) != EOF) {
		if (c == '\n')
			bb_putchar('\r');
		bb_putchar(c);
		empty = 0;
	}
	if (empty)
		puts("\r\nSystem closed for routine maintenance\r");

	fclose(fp);
	fflush_all();
	/* Users say that they do need this prior to exit: */
	tcdrain(STDOUT_FILENO);
	exit(EXIT_FAILURE);
}
#else
static ALWAYS_INLINE void die_if_nologin(void) {}
#endif

#if ENABLE_FEATURE_SECURETTY && !ENABLE_PAM
static int check_securetty(void)
{
	char *buf = (char*)"/etc/securetty"; /* any non-NULL is ok */
	parser_t *parser = config_open2("/etc/securetty", fopen_for_read);
	while (config_read(parser, &buf, 1, 1, "# \t", PARSE_NORMAL)) {
		if (strcmp(buf, short_tty) == 0)
			break;
		buf = NULL;
	}
	config_close(parser);
	/* buf != NULL here if config file was not found, empty
	 * or line was found which equals short_tty */
	return buf != NULL;
}
#else
static ALWAYS_INLINE int check_securetty(void) { return 1; }
#endif

#if ENABLE_SELINUX
static void initselinux(char *username, char *full_tty,
						security_context_t *user_sid)
{
	security_context_t old_tty_sid, new_tty_sid;

	if (!is_selinux_enabled())
		return;

	if (get_default_context(username, NULL, user_sid)) {
		bb_error_msg_and_die("can't get SID for %s", username);
	}
	if (getfilecon(full_tty, &old_tty_sid) < 0) {
		bb_perror_msg_and_die("getfilecon(%s) failed", full_tty);
	}
	if (security_compute_relabel(*user_sid, old_tty_sid,
				SECCLASS_CHR_FILE, &new_tty_sid) != 0) {
		bb_perror_msg_and_die("security_change_sid(%s) failed", full_tty);
	}
	if (setfilecon(full_tty, new_tty_sid) != 0) {
		bb_perror_msg_and_die("chsid(%s, %s) failed", full_tty, new_tty_sid);
	}
}
#endif

#if ENABLE_LOGIN_SCRIPTS
static void run_login_script(struct passwd *pw, char *full_tty)
{
	char *t_argv[2];

	t_argv[0] = getenv("LOGIN_PRE_SUID_SCRIPT");
	if (t_argv[0]) {
		t_argv[1] = NULL;
		xsetenv("LOGIN_TTY", full_tty);
		xsetenv("LOGIN_USER", pw->pw_name);
		xsetenv("LOGIN_UID", utoa(pw->pw_uid));
		xsetenv("LOGIN_GID", utoa(pw->pw_gid));
		xsetenv("LOGIN_SHELL", pw->pw_shell);
		spawn_and_wait(t_argv);	/* NOMMU-friendly */
		unsetenv("LOGIN_TTY");
		unsetenv("LOGIN_USER");
		unsetenv("LOGIN_UID");
		unsetenv("LOGIN_GID");
		unsetenv("LOGIN_SHELL");
	}
}
#else
void run_login_script(struct passwd *pw, char *full_tty);
#endif

static void get_username_or_die(char *buf, int size_buf)
{
	int c, cntdown;

	cntdown = EMPTY_USERNAME_COUNT;
 prompt:
	print_login_prompt();
	/* skip whitespace */
	do {
		c = getchar();
		if (c == EOF)
			exit(EXIT_FAILURE);
		if (c == '\n') {
			if (!--cntdown)
				exit(EXIT_FAILURE);
			goto prompt;
		}
	} while (isspace(c)); /* maybe isblank? */

	*buf++ = c;
	if (!fgets(buf, size_buf-2, stdin))
		exit(EXIT_FAILURE);
	if (!strchr(buf, '\n'))
		exit(EXIT_FAILURE);
	while ((unsigned char)*buf > ' ')
		buf++;
	*buf = '\0';
}

static void motd(void)
{
	int fd;

	fd = open(bb_path_motd_file, O_RDONLY);
	if (fd >= 0) {
		fflush_all();
		bb_copyfd_eof(fd, STDOUT_FILENO);
		close(fd);
	}
}

static void alarm_handler(int sig UNUSED_PARAM)
{
	/* This is the escape hatch!  Poor serial line users and the like
	 * arrive here when their connection is broken.
	 * We don't want to block here */
	ndelay_on(1);
	printf("\r\nLogin timed out after %d seconds\r\n", TIMEOUT);
	fflush_all();
	/* unix API is brain damaged regarding O_NONBLOCK,
	 * we should undo it, or else we can affect other processes */
	ndelay_off(1);
	_exit(EXIT_SUCCESS);
}

int login_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int login_main(int argc UNUSED_PARAM, char **argv)
{
	enum {
		LOGIN_OPT_f = (1<<0),
		LOGIN_OPT_h = (1<<1),
		LOGIN_OPT_p = (1<<2),
	};
	char *fromhost;
	char username[USERNAME_SIZE];
	const char *tmp;
	int run_by_root;
	unsigned opt;
	int count = 0;
	struct passwd *pw;
	char *opt_host = opt_host; /* for compiler */
	char *opt_user = opt_user; /* for compiler */
	char *full_tty;
	IF_SELINUX(security_context_t user_sid = NULL;)
	IF_FEATURE_UTMP(struct utmp utent;)
#if ENABLE_PAM
	int pamret;
	pam_handle_t *pamh;
	const char *pamuser;
	const char *failed_msg;
	struct passwd pwdstruct;
	char pwdbuf[256];
#endif

	username[0] = '\0';
	signal(SIGALRM, alarm_handler);
	alarm(TIMEOUT);

	/* More of suid paranoia if called by non-root: */
	/* Clear dangerous stuff, set PATH */
	run_by_root = !sanitize_env_if_suid();

	/* Mandatory paranoia for suid applet:
	 * ensure that fd# 0,1,2 are opened (at least to /dev/null)
	 * and any extra open fd's are closed.
	 * (The name of the function is misleading. Not daemonizing here.) */
	bb_daemonize_or_rexec(DAEMON_ONLY_SANITIZE | DAEMON_CLOSE_EXTRA_FDS, NULL);

	opt = getopt32(argv, "f:h:p", &opt_user, &opt_host);
	if (opt & LOGIN_OPT_f) {
		if (!run_by_root)
			bb_error_msg_and_die("-f is for root only");
		safe_strncpy(username, opt_user, sizeof(username));
	}
	argv += optind;
	if (argv[0]) /* user from command line (getty) */
		safe_strncpy(username, argv[0], sizeof(username));

	/* Let's find out and memorize our tty */
	if (!isatty(STDIN_FILENO) || !isatty(STDOUT_FILENO) || !isatty(STDERR_FILENO))
		return EXIT_FAILURE;		/* Must be a terminal */
	full_tty = xmalloc_ttyname(STDIN_FILENO);
	if (!full_tty)
		full_tty = xstrdup("UNKNOWN");
	short_tty = full_tty;
	if (strncmp(full_tty, "/dev/", 5) == 0)
		short_tty += 5;

	read_or_build_utent(&utent, run_by_root);

	if (opt & LOGIN_OPT_h) {
		IF_FEATURE_UTMP(safe_strncpy(utent.ut_host, opt_host, sizeof(utent.ut_host));)
		fromhost = xasprintf(" on '%s' from '%s'", short_tty, opt_host);
	} else {
		fromhost = xasprintf(" on '%s'", short_tty);
	}

	/* Was breaking "login <username>" from shell command line: */
	/*bb_setpgrp();*/

	openlog(applet_name, LOG_PID | LOG_CONS, LOG_AUTH);

	while (1) {
		/* flush away any type-ahead (as getty does) */
		ioctl(0, TCFLSH, TCIFLUSH);

		if (!username[0])
			get_username_or_die(username, sizeof(username));

#if ENABLE_PAM
		pamret = pam_start("login", username, &conv, &pamh);
		if (pamret != PAM_SUCCESS) {
			failed_msg = "start";
			goto pam_auth_failed;
		}
		/* set TTY (so things like securetty work) */
		pamret = pam_set_item(pamh, PAM_TTY, short_tty);
		if (pamret != PAM_SUCCESS) {
			failed_msg = "set_item(TTY)";
			goto pam_auth_failed;
		}
		pamret = pam_authenticate(pamh, 0);
		if (pamret != PAM_SUCCESS) {
			failed_msg = "authenticate";
			goto pam_auth_failed;
			/* TODO: or just "goto auth_failed"
			 * since user seems to enter wrong password
			 * (in this case pamret == 7)
			 */
		}
		/* check that the account is healthy */
		pamret = pam_acct_mgmt(pamh, 0);
		if (pamret != PAM_SUCCESS) {
			failed_msg = "acct_mgmt";
			goto pam_auth_failed;
		}
		/* read user back */
		pamuser = NULL;
		/* gcc: "dereferencing type-punned pointer breaks aliasing rules..."
		 * thus we cast to (void*) */
		if (pam_get_item(pamh, PAM_USER, (void*)&pamuser) != PAM_SUCCESS) {
			failed_msg = "get_item(USER)";
			goto pam_auth_failed;
		}
		if (!pamuser || !pamuser[0])
			goto auth_failed;
		safe_strncpy(username, pamuser, sizeof(username));
		/* Don't use "pw = getpwnam(username);",
		 * PAM is said to be capable of destroying static storage
		 * used by getpwnam(). We are using safe(r) function */
		pw = NULL;
		getpwnam_r(username, &pwdstruct, pwdbuf, sizeof(pwdbuf), &pw);
		if (!pw)
			goto auth_failed;
		pamret = pam_open_session(pamh, 0);
		if (pamret != PAM_SUCCESS) {
			failed_msg = "open_session";
			goto pam_auth_failed;
		}
		pamret = pam_setcred(pamh, PAM_ESTABLISH_CRED);
		if (pamret != PAM_SUCCESS) {
			failed_msg = "setcred";
			goto pam_auth_failed;
		}
		break; /* success, continue login process */

 pam_auth_failed:
		/* syslog, because we don't want potential attacker
		 * to know _why_ login failed */
		syslog(LOG_WARNING, "pam_%s call failed: %s (%d)", failed_msg,
					pam_strerror(pamh, pamret), pamret);
		safe_strncpy(username, "UNKNOWN", sizeof(username));
#else /* not PAM */
		pw = getpwnam(username);
		if (!pw) {
			strcpy(username, "UNKNOWN");
			goto fake_it;
		}

		if (pw->pw_passwd[0] == '!' || pw->pw_passwd[0] == '*')
			goto auth_failed;

		if (opt & LOGIN_OPT_f)
			break; /* -f USER: success without asking passwd */

		if (pw->pw_uid == 0 && !check_securetty())
			goto auth_failed;

		/* Don't check the password if password entry is empty (!) */
		if (!pw->pw_passwd[0])
			break;
 fake_it:
		/* authorization takes place here */
		if (correct_password(pw))
			break;
#endif /* ENABLE_PAM */
 auth_failed:
		opt &= ~LOGIN_OPT_f;
		bb_do_delay(FAIL_DELAY);
		/* TODO: doesn't sound like correct English phrase to me */
		puts("Login incorrect");
		if (++count == 3) {
			syslog(LOG_WARNING, "invalid password for '%s'%s",
						username, fromhost);
			return EXIT_FAILURE;
		}
		username[0] = '\0';
	} /* while (1) */

	alarm(0);
	/* We can ignore /etc/nologin if we are logging in as root,
	 * it doesn't matter whether we are run by root or not */
	if (pw->pw_uid != 0)
		die_if_nologin();

	write_utent(&utent, username);

	IF_SELINUX(initselinux(username, full_tty, &user_sid));

	/* Try these, but don't complain if they fail.
	 * _f_chown is safe wrt race t=ttyname(0);...;chown(t); */
	fchown(0, pw->pw_uid, pw->pw_gid);
	fchmod(0, 0600);

	/* We trust environment only if we run by root */
	if (ENABLE_LOGIN_SCRIPTS && run_by_root)
		run_login_script(pw, full_tty);

	change_identity(pw);
	tmp = pw->pw_shell;
	if (!tmp || !*tmp)
		tmp = DEFAULT_SHELL;
	/* setup_environment params: shell, clear_env, change_env, pw */
	setup_environment(tmp, !(opt & LOGIN_OPT_p), 1, pw);

	motd();

	if (pw->pw_uid == 0)
		syslog(LOG_INFO, "root login%s", fromhost);

	/* well, a simple setexeccon() here would do the job as well,
	 * but let's play the game for now */
	IF_SELINUX(set_current_security_context(user_sid);)

	// util-linux login also does:
	// /* start new session */
	// setsid();
	// /* TIOCSCTTY: steal tty from other process group */
	// if (ioctl(0, TIOCSCTTY, 1)) error_msg...
	// BBox login used to do this (see above):
	// bb_setpgrp();
	// If this stuff is really needed, add it and explain why!

	/* Set signals to defaults */
	/* Non-ignored signals revert to SIG_DFL on exec anyway */
	/*signal(SIGALRM, SIG_DFL);*/

	/* Is this correct? This way user can ctrl-c out of /etc/profile,
	 * potentially creating security breach (tested with bash 3.0).
	 * But without this, bash 3.0 will not enable ctrl-c either.
	 * Maybe bash is buggy?
	 * Need to find out what standards say about /bin/login -
	 * should we leave SIGINT etc enabled or disabled? */
	signal(SIGINT, SIG_DFL);

	/* Exec login shell with no additional parameters */
	run_shell(tmp, 1, NULL, NULL);

	/* return EXIT_FAILURE; - not reached */
}
1	niro	532	/* vi: set sw=4 ts=4: */
2			/*
3			* Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
4			*/
5
6	niro	816	#include "libbb.h"
7			#include <syslog.h>
8	niro	532	#include <utmp.h>
9			#include <sys/resource.h>
10
11	niro	816	#if ENABLE_SELINUX
12	niro	532	#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 */
15			#endif
16
17	niro	816	#if ENABLE_PAM
18			/* PAM may include <locale.h>. We may need to undefine bbox's stub define: */
19			#undef setlocale
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 = {
25			misc_conv,
26			NULL
27			};
28			#endif
29
30	niro	532	enum {
31			TIMEOUT = 60,
32			EMPTY_USERNAME_COUNT = 10,
33			USERNAME_SIZE = 32,
34			TTYNAME_SIZE = 32,
35			};
36
37	niro	816	static char* short_tty;
38	niro	532
39			#if ENABLE_FEATURE_UTMP
40			/* vv Taken from tinylogin utmp.c vv */
41			/*
42			* read_or_build_utent - see if utmp file is correct for this process
43			*
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.
48			*
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
52			* command line flags.
53			*/
54
55	niro	816	static void read_or_build_utent(struct utmp *utptr, int run_by_root)
56	niro	532	{
57			struct utmp *ut;
58			pid_t pid = getpid();
59
60			setutent();
61
62			/* First, try to find a valid utmp entry for this process. */
63	niro	816	/* If there is one, just use it. */
64			while ((ut = getutent()) != NULL)
65			if (ut->ut_pid == pid && ut->ut_line[0] && ut->ut_id[0]
66			&& (ut->ut_type == LOGIN_PROCESS \|\| ut->ut_type == USER_PROCESS)
67			) {
68			utptr = ut; /* struct copy */
69			if (run_by_root) /* why only for root? */
70			memset(utptr->ut_host, 0, sizeof(utptr->ut_host));
71			return;
72			}
73	niro	532
74	niro	816	// Why? Do we require non-root to exec login from another
75			// former login process (e.g. login shell)? Some login's have
76			// login shells as children, so it won't work...
77			// if (!run_by_root)
78			// bb_error_msg_and_die("no utmp entry found");
79	niro	532
80	niro	816	/* Otherwise create a new one. */
81			memset(utptr, 0, sizeof(*utptr));
82			utptr->ut_type = LOGIN_PROCESS;
83			utptr->ut_pid = pid;
84			strncpy(utptr->ut_line, short_tty, sizeof(utptr->ut_line));
85			/* This one is only 4 chars wide. Try to fit something
86			* remotely meaningful by skipping "tty"... */
87			strncpy(utptr->ut_id, short_tty + 3, sizeof(utptr->ut_id));
88			strncpy(utptr->ut_user, "LOGIN", sizeof(utptr->ut_user));
89			utptr->ut_tv.tv_sec = time(NULL);
90	niro	532	}
91
92			/*
93			* write_utent - put a USER_PROCESS entry in the utmp file
94			*
95			* write_utent changes the type of the current utmp entry to
96			* USER_PROCESS. the wtmp file will be updated as well.
97			*/
98	niro	816	static void write_utent(struct utmp utptr, const char username)
99	niro	532	{
100	niro	816	utptr->ut_type = USER_PROCESS;
101			strncpy(utptr->ut_user, username, sizeof(utptr->ut_user));
102			utptr->ut_tv.tv_sec = time(NULL);
103	niro	532	/* other fields already filled in by read_or_build_utent above */
104			setutent();
105	niro	816	pututline(utptr);
106	niro	532	endutent();
107			#if ENABLE_FEATURE_WTMP
108			if (access(bb_path_wtmp_file, R_OK\|W_OK) == -1) {
109			close(creat(bb_path_wtmp_file, 0664));
110			}
111	niro	816	updwtmp(bb_path_wtmp_file, utptr);
112	niro	532	#endif
113			}
114			#else /* !ENABLE_FEATURE_UTMP */
115	niro	816	#define read_or_build_utent(utptr, run_by_root) ((void)0)
116			#define write_utent(utptr, username) ((void)0)
117	niro	532	#endif /* !ENABLE_FEATURE_UTMP */
118
119	niro	816	#if ENABLE_FEATURE_NOLOGIN
120			static void die_if_nologin(void)
121	niro	532	{
122			FILE *fp;
123			int c;
124	niro	816	int empty = 1;
125	niro	532
126	niro	816	fp = fopen_for_read("/etc/nologin");
127			if (!fp) /* assuming it does not exist */
128	niro	532	return;
129
130	niro	816	while ((c = getc(fp)) != EOF) {
131			if (c == '\n')
132			bb_putchar('\r');
133			bb_putchar(c);
134			empty = 0;
135			}
136			if (empty)
137	niro	532	puts("\r\nSystem closed for routine maintenance\r");
138	niro	816
139			fclose(fp);
140	niro	984	fflush_all();
141	niro	816	/* Users say that they do need this prior to exit: */
142			tcdrain(STDOUT_FILENO);
143			exit(EXIT_FAILURE);
144	niro	532	}
145	niro	816	#else
146			static ALWAYS_INLINE void die_if_nologin(void) {}
147			#endif
148	niro	532
149	niro	816	#if ENABLE_FEATURE_SECURETTY && !ENABLE_PAM
150	niro	532	static int check_securetty(void)
151			{
152	niro	816	char buf = (char)"/etc/securetty"; /* any non-NULL is ok */
153			parser_t *parser = config_open2("/etc/securetty", fopen_for_read);
154			while (config_read(parser, &buf, 1, 1, "# \t", PARSE_NORMAL)) {
155			if (strcmp(buf, short_tty) == 0)
156			break;
157			buf = NULL;
158	niro	532	}
159	niro	816	config_close(parser);
160			/* buf != NULL here if config file was not found, empty
161			* or line was found which equals short_tty */
162			return buf != NULL;
163	niro	532	}
164			#else
165	niro	816	static ALWAYS_INLINE int check_securetty(void) { return 1; }
166	niro	532	#endif
167
168	niro	984	#if ENABLE_SELINUX
169			static void initselinux(char username, char full_tty,
170			security_context_t *user_sid)
171			{
172			security_context_t old_tty_sid, new_tty_sid;
173
174			if (!is_selinux_enabled())
175			return;
176
177			if (get_default_context(username, NULL, user_sid)) {
178			bb_error_msg_and_die("can't get SID for %s", username);
179			}
180			if (getfilecon(full_tty, &old_tty_sid) < 0) {
181			bb_perror_msg_and_die("getfilecon(%s) failed", full_tty);
182			}
183			if (security_compute_relabel(*user_sid, old_tty_sid,
184			SECCLASS_CHR_FILE, &new_tty_sid) != 0) {
185			bb_perror_msg_and_die("security_change_sid(%s) failed", full_tty);
186			}
187			if (setfilecon(full_tty, new_tty_sid) != 0) {
188			bb_perror_msg_and_die("chsid(%s, %s) failed", full_tty, new_tty_sid);
189			}
190			}
191			#endif
192
193			#if ENABLE_LOGIN_SCRIPTS
194			static void run_login_script(struct passwd pw, char full_tty)
195			{
196			char *t_argv[2];
197
198			t_argv[0] = getenv("LOGIN_PRE_SUID_SCRIPT");
199			if (t_argv[0]) {
200			t_argv[1] = NULL;
201			xsetenv("LOGIN_TTY", full_tty);
202			xsetenv("LOGIN_USER", pw->pw_name);
203			xsetenv("LOGIN_UID", utoa(pw->pw_uid));
204			xsetenv("LOGIN_GID", utoa(pw->pw_gid));
205			xsetenv("LOGIN_SHELL", pw->pw_shell);
206			spawn_and_wait(t_argv); /* NOMMU-friendly */
207			unsetenv("LOGIN_TTY");
208			unsetenv("LOGIN_USER");
209			unsetenv("LOGIN_UID");
210			unsetenv("LOGIN_GID");
211			unsetenv("LOGIN_SHELL");
212			}
213			}
214			#else
215			void run_login_script(struct passwd pw, char full_tty);
216			#endif
217
218	niro	532	static void get_username_or_die(char *buf, int size_buf)
219			{
220			int c, cntdown;
221	niro	816
222	niro	532	cntdown = EMPTY_USERNAME_COUNT;
223	niro	816	prompt:
224			print_login_prompt();
225	niro	532	/* skip whitespace */
226			do {
227			c = getchar();
228	niro	984	if (c == EOF)
229			exit(EXIT_FAILURE);
230	niro	532	if (c == '\n') {
231	niro	984	if (!--cntdown)
232			exit(EXIT_FAILURE);
233	niro	532	goto prompt;
234			}
235	niro	984	} while (isspace(c)); /* maybe isblank? */
236	niro	532
237			*buf++ = c;
238			if (!fgets(buf, size_buf-2, stdin))
239	niro	816	exit(EXIT_FAILURE);
240	niro	532	if (!strchr(buf, '\n'))
241	niro	816	exit(EXIT_FAILURE);
242	niro	984	while ((unsigned char)*buf > ' ')
243			buf++;
244	niro	532	*buf = '\0';
245			}
246
247			static void motd(void)
248			{
249	niro	816	int fd;
250	niro	532
251	niro	816	fd = open(bb_path_motd_file, O_RDONLY);
252			if (fd >= 0) {
253	niro	984	fflush_all();
254	niro	816	bb_copyfd_eof(fd, STDOUT_FILENO);
255			close(fd);
256	niro	532	}
257			}
258
259	niro	816	static void alarm_handler(int sig UNUSED_PARAM)
260	niro	532	{
261			/* This is the escape hatch! Poor serial line users and the like
262			* arrive here when their connection is broken.
263			* We don't want to block here */
264	niro	816	ndelay_on(1);
265			printf("\r\nLogin timed out after %d seconds\r\n", TIMEOUT);
266	niro	984	fflush_all();
267	niro	816	/* unix API is brain damaged regarding O_NONBLOCK,
268			* we should undo it, or else we can affect other processes */
269			ndelay_off(1);
270			_exit(EXIT_SUCCESS);
271	niro	532	}
272
273	niro	816	int login_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
274			int login_main(int argc UNUSED_PARAM, char **argv)
275	niro	532	{
276			enum {
277			LOGIN_OPT_f = (1<<0),
278			LOGIN_OPT_h = (1<<1),
279			LOGIN_OPT_p = (1<<2),
280			};
281	niro	816	char *fromhost;
282	niro	532	char username[USERNAME_SIZE];
283			const char *tmp;
284	niro	816	int run_by_root;
285	niro	532	unsigned opt;
286			int count = 0;
287			struct passwd *pw;
288	niro	816	char opt_host = opt_host; / for compiler */
289			char opt_user = opt_user; / for compiler */
290	niro	984	char *full_tty;
291			IF_SELINUX(security_context_t user_sid = NULL;)
292			IF_FEATURE_UTMP(struct utmp utent;)
293	niro	816	#if ENABLE_PAM
294			int pamret;
295			pam_handle_t *pamh;
296			const char *pamuser;
297			const char *failed_msg;
298			struct passwd pwdstruct;
299			char pwdbuf[256];
300			#endif
301	niro	532
302			username[0] = '\0';
303			signal(SIGALRM, alarm_handler);
304			alarm(TIMEOUT);
305
306	niro	816	/* More of suid paranoia if called by non-root: */
307			/* Clear dangerous stuff, set PATH */
308			run_by_root = !sanitize_env_if_suid();
309
310			/* Mandatory paranoia for suid applet:
311			* ensure that fd# 0,1,2 are opened (at least to /dev/null)
312			* and any extra open fd's are closed.
313			* (The name of the function is misleading. Not daemonizing here.) */
314			bb_daemonize_or_rexec(DAEMON_ONLY_SANITIZE \| DAEMON_CLOSE_EXTRA_FDS, NULL);
315
316			opt = getopt32(argv, "f:h:p", &opt_user, &opt_host);
317	niro	532	if (opt & LOGIN_OPT_f) {
318	niro	816	if (!run_by_root)
319	niro	532	bb_error_msg_and_die("-f is for root only");
320			safe_strncpy(username, opt_user, sizeof(username));
321			}
322	niro	816	argv += optind;
323			if (argv[0]) /* user from command line (getty) */
324			safe_strncpy(username, argv[0], sizeof(username));
325	niro	532
326			/* Let's find out and memorize our tty */
327	niro	984	if (!isatty(STDIN_FILENO) \|\| !isatty(STDOUT_FILENO) \|\| !isatty(STDERR_FILENO))
328	niro	532	return EXIT_FAILURE; /* Must be a terminal */
329	niro	984	full_tty = xmalloc_ttyname(STDIN_FILENO);
330			if (!full_tty)
331			full_tty = xstrdup("UNKNOWN");
332			short_tty = full_tty;
333			if (strncmp(full_tty, "/dev/", 5) == 0)
334			short_tty += 5;
335	niro	532
336	niro	816	read_or_build_utent(&utent, run_by_root);
337	niro	532
338	niro	816	if (opt & LOGIN_OPT_h) {
339	niro	984	IF_FEATURE_UTMP(safe_strncpy(utent.ut_host, opt_host, sizeof(utent.ut_host));)
340	niro	816	fromhost = xasprintf(" on '%s' from '%s'", short_tty, opt_host);
341	niro	984	} else {
342	niro	816	fromhost = xasprintf(" on '%s'", short_tty);
343	niro	984	}
344	niro	532
345	niro	816	/* Was breaking "login <username>" from shell command line: */
346			/bb_setpgrp();/
347	niro	532
348	niro	984	openlog(applet_name, LOG_PID \| LOG_CONS, LOG_AUTH);
349	niro	532
350			while (1) {
351	niro	816	/* flush away any type-ahead (as getty does) */
352			ioctl(0, TCFLSH, TCIFLUSH);
353
354	niro	532	if (!username[0])
355			get_username_or_die(username, sizeof(username));
356
357	niro	816	#if ENABLE_PAM
358			pamret = pam_start("login", username, &conv, &pamh);
359			if (pamret != PAM_SUCCESS) {
360			failed_msg = "start";
361			goto pam_auth_failed;
362			}
363			/* set TTY (so things like securetty work) */
364			pamret = pam_set_item(pamh, PAM_TTY, short_tty);
365			if (pamret != PAM_SUCCESS) {
366			failed_msg = "set_item(TTY)";
367			goto pam_auth_failed;
368			}
369			pamret = pam_authenticate(pamh, 0);
370			if (pamret != PAM_SUCCESS) {
371			failed_msg = "authenticate";
372			goto pam_auth_failed;
373			/* TODO: or just "goto auth_failed"
374			* since user seems to enter wrong password
375			* (in this case pamret == 7)
376			*/
377			}
378			/* check that the account is healthy */
379			pamret = pam_acct_mgmt(pamh, 0);
380			if (pamret != PAM_SUCCESS) {
381			failed_msg = "acct_mgmt";
382			goto pam_auth_failed;
383			}
384			/* read user back */
385			pamuser = NULL;
386			/* gcc: "dereferencing type-punned pointer breaks aliasing rules..."
387			* thus we cast to (void) /
388			if (pam_get_item(pamh, PAM_USER, (void*)&pamuser) != PAM_SUCCESS) {
389			failed_msg = "get_item(USER)";
390			goto pam_auth_failed;
391			}
392			if (!pamuser \|\| !pamuser[0])
393			goto auth_failed;
394			safe_strncpy(username, pamuser, sizeof(username));
395			/* Don't use "pw = getpwnam(username);",
396			* PAM is said to be capable of destroying static storage
397			* used by getpwnam(). We are using safe(r) function */
398			pw = NULL;
399			getpwnam_r(username, &pwdstruct, pwdbuf, sizeof(pwdbuf), &pw);
400			if (!pw)
401			goto auth_failed;
402			pamret = pam_open_session(pamh, 0);
403			if (pamret != PAM_SUCCESS) {
404			failed_msg = "open_session";
405			goto pam_auth_failed;
406			}
407			pamret = pam_setcred(pamh, PAM_ESTABLISH_CRED);
408			if (pamret != PAM_SUCCESS) {
409			failed_msg = "setcred";
410			goto pam_auth_failed;
411			}
412			break; /* success, continue login process */
413
414			pam_auth_failed:
415	niro	984	/* syslog, because we don't want potential attacker
416			* to know _why_ login failed */
417			syslog(LOG_WARNING, "pam_%s call failed: %s (%d)", failed_msg,
418	niro	816	pam_strerror(pamh, pamret), pamret);
419			safe_strncpy(username, "UNKNOWN", sizeof(username));
420			#else /* not PAM */
421	niro	532	pw = getpwnam(username);
422			if (!pw) {
423	niro	816	strcpy(username, "UNKNOWN");
424			goto fake_it;
425	niro	532	}
426
427			if (pw->pw_passwd[0] == '!' \|\| pw->pw_passwd[0] == '*')
428			goto auth_failed;
429
430			if (opt & LOGIN_OPT_f)
431			break; /* -f USER: success without asking passwd */
432
433			if (pw->pw_uid == 0 && !check_securetty())
434			goto auth_failed;
435
436			/* Don't check the password if password entry is empty (!) */
437			if (!pw->pw_passwd[0])
438			break;
439	niro	816	fake_it:
440	niro	532	/* authorization takes place here */
441			if (correct_password(pw))
442			break;
443	niro	816	#endif /* ENABLE_PAM */
444			auth_failed:
445	niro	532	opt &= ~LOGIN_OPT_f;
446			bb_do_delay(FAIL_DELAY);
447	niro	816	/* TODO: doesn't sound like correct English phrase to me */
448	niro	532	puts("Login incorrect");
449			if (++count == 3) {
450			syslog(LOG_WARNING, "invalid password for '%s'%s",
451			username, fromhost);
452			return EXIT_FAILURE;
453			}
454			username[0] = '\0';
455	niro	816	} /* while (1) */
456	niro	532
457			alarm(0);
458	niro	816	/* We can ignore /etc/nologin if we are logging in as root,
459			* it doesn't matter whether we are run by root or not */
460			if (pw->pw_uid != 0)
461			die_if_nologin();
462	niro	532
463	niro	816	write_utent(&utent, username);
464	niro	532
465	niro	984	IF_SELINUX(initselinux(username, full_tty, &user_sid));
466	niro	532
467			/* Try these, but don't complain if they fail.
468			* _f_chown is safe wrt race t=ttyname(0);...;chown(t); */
469			fchown(0, pw->pw_uid, pw->pw_gid);
470			fchmod(0, 0600);
471
472	niro	816	/* We trust environment only if we run by root */
473	niro	984	if (ENABLE_LOGIN_SCRIPTS && run_by_root)
474			run_login_script(pw, full_tty);
475	niro	816
476	niro	532	change_identity(pw);
477			tmp = pw->pw_shell;
478			if (!tmp \|\| !*tmp)
479			tmp = DEFAULT_SHELL;
480	niro	816	/* setup_environment params: shell, clear_env, change_env, pw */
481			setup_environment(tmp, !(opt & LOGIN_OPT_p), 1, pw);
482	niro	532
483			motd();
484
485			if (pw->pw_uid == 0)
486			syslog(LOG_INFO, "root login%s", fromhost);
487	niro	984
488	niro	532	/* well, a simple setexeccon() here would do the job as well,
489			* but let's play the game for now */
490	niro	984	IF_SELINUX(set_current_security_context(user_sid);)
491	niro	532
492			// util-linux login also does:
493			// /* start new session */
494			// setsid();
495			// /* TIOCSCTTY: steal tty from other process group */
496			// if (ioctl(0, TIOCSCTTY, 1)) error_msg...
497	niro	816	// BBox login used to do this (see above):
498			// bb_setpgrp();
499			// If this stuff is really needed, add it and explain why!
500	niro	532
501	niro	816	/* Set signals to defaults */
502			/* Non-ignored signals revert to SIG_DFL on exec anyway */
503			/signal(SIGALRM, SIG_DFL);/
504
505	niro	532	/* Is this correct? This way user can ctrl-c out of /etc/profile,
506			* potentially creating security breach (tested with bash 3.0).
507			* But without this, bash 3.0 will not enable ctrl-c either.
508			* Maybe bash is buggy?
509			* Need to find out what standards say about /bin/login -
510	niro	816	* should we leave SIGINT etc enabled or disabled? */
511	niro	532	signal(SIGINT, SIG_DFL);
512
513	niro	816	/* Exec login shell with no additional parameters */
514			run_shell(tmp, 1, NULL, NULL);
515	niro	532
516	niro	816	/* return EXIT_FAILURE; - not reached */
517	niro	532	}