busybox/loginutils/login.c
James Byrne 6937487be7 libbb: reduce the overhead of single parameter bb_error_msg() calls
Back in 2007, commit 0c97c9d437 ("'simple' error message functions by
Loic Grenie") introduced bb_simple_perror_msg() to allow for a lower
overhead call to bb_perror_msg() when only a string was being printed
with no parameters. This saves space for some CPU architectures because
it avoids the overhead of a call to a variadic function. However there
has never been a simple version of bb_error_msg(), and since 2007 many
new calls to bb_perror_msg() have been added that only take a single
parameter and so could have been using bb_simple_perror_message().

This changeset introduces 'simple' versions of bb_info_msg(),
bb_error_msg(), bb_error_msg_and_die(), bb_herror_msg() and
bb_herror_msg_and_die(), and replaces all calls that only take a
single parameter, or use something like ("%s", arg), with calls to the
corresponding 'simple' version.

Since it is likely that single parameter calls to the variadic functions
may be accidentally reintroduced in the future a new debugging config
option WARN_SIMPLE_MSG has been introduced. This uses some macro magic
which will cause any such calls to generate a warning, but this is
turned off by default to avoid use of the unpleasant macros in normal
circumstances.

This is a large changeset due to the number of calls that have been
replaced. The only files that contain changes other than simple
substitution of function calls are libbb.h, libbb/herror_msg.c,
libbb/verror_msg.c and libbb/xfuncs_printf.c. In miscutils/devfsd.c,
networking/udhcp/common.h and util-linux/mdev.c additonal macros have
been added for logging so that single parameter and multiple parameter
logging variants exist.

The amount of space saved varies considerably by architecture, and was
found to be as follows (for 'defconfig' using GCC 7.4):

Arm:     -92 bytes
MIPS:    -52 bytes
PPC:   -1836 bytes
x86_64: -938 bytes

Note that for the MIPS architecture only an exception had to be made
disabling the 'simple' calls for 'udhcp' (in networking/udhcp/common.h)
because it made these files larger on MIPS.

Signed-off-by: James Byrne <james.byrne@origamienergy.com>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
2019-07-02 11:35:03 +02:00

609 lines
16 KiB
C

/* vi: set sw=4 ts=4: */
/*
* Licensed under GPLv2 or later, see file LICENSE in this source tree.
*/
//config:config LOGIN
//config: bool "login (24 kb)"
//config: default y
//config: select FEATURE_SYSLOG
//config: help
//config: login is used when signing onto a system.
//config:
//config: Note that busybox binary must be setuid root for this applet to
//config: work properly.
//config:
//config:config LOGIN_SESSION_AS_CHILD
//config: bool "Run logged in session in a child process"
//config: default y if PAM
//config: depends on LOGIN
//config: help
//config: Run the logged in session in a child process. This allows
//config: login to clean up things such as utmp entries or PAM sessions
//config: when the login session is complete. If you use PAM, you
//config: almost always would want this to be set to Y, else PAM session
//config: will not be cleaned up.
//config:
//config:config LOGIN_SCRIPTS
//config: bool "Support login scripts"
//config: depends on LOGIN
//config: default y
//config: help
//config: Enable this if you want login to execute $LOGIN_PRE_SUID_SCRIPT
//config: just prior to switching from root to logged-in user.
//config:
//config:config FEATURE_NOLOGIN
//config: bool "Support /etc/nologin"
//config: default y
//config: depends on LOGIN
//config: help
//config: The file /etc/nologin is used by (some versions of) login(1).
//config: If it exists, non-root logins are prohibited.
//config:
//config:config FEATURE_SECURETTY
//config: bool "Support /etc/securetty"
//config: default y
//config: depends on LOGIN
//config: help
//config: The file /etc/securetty is used by (some versions of) login(1).
//config: The file contains the device names of tty lines (one per line,
//config: without leading /dev/) on which root is allowed to login.
//applet:/* Needs to be run by root or be suid root - needs to change uid and gid: */
//applet:IF_LOGIN(APPLET(login, BB_DIR_BIN, BB_SUID_REQUIRE))
//kbuild:lib-$(CONFIG_LOGIN) += login.o
//usage:#define login_trivial_usage
//usage: "[-p] [-h HOST] [[-f] USER]"
//usage:#define login_full_usage "\n\n"
//usage: "Begin a new session on the system\n"
//usage: "\n -f Don't authenticate (user already authenticated)"
//usage: "\n -h HOST Host user came from (for network logins)"
//usage: "\n -p Preserve environment"
#include "libbb.h"
#include "common_bufsiz.h"
#include <syslog.h>
#if ENABLE_SELINUX
# include <selinux/selinux.h> /* for is_selinux_enabled() */
# include <selinux/get_context_list.h> /* for get_default_context() */
# /* from deprecated <selinux/flask.h>: */
# undef SECCLASS_CHR_FILE
# define SECCLASS_CHR_FILE 10
#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>
# if 0
/* This supposedly can be used to avoid double password prompt,
* if used instead of standard misc_conv():
*
* "When we want to authenticate first with local method and then with tacacs for example,
* the password is asked for local method and if not good is asked a second time for tacacs.
* So if we want to authenticate a user with tacacs, and the user exists localy, the password is
* asked two times before authentication is accepted."
*
* However, code looks shaky. For example, why misc_conv() return value is ignored?
* Are msg[i] and resp[i] indexes handled correctly?
*/
static char *passwd = NULL;
static int my_conv(int num_msg, const struct pam_message **msg,
struct pam_response **resp, void *data)
{
int i;
for (i = 0; i < num_msg; i++) {
switch (msg[i]->msg_style) {
case PAM_PROMPT_ECHO_OFF:
if (passwd == NULL) {
misc_conv(num_msg, msg, resp, data);
passwd = xstrdup(resp[i]->resp);
return PAM_SUCCESS;
}
resp[0] = xzalloc(sizeof(struct pam_response));
resp[0]->resp = passwd;
passwd = NULL;
resp[0]->resp_retcode = PAM_SUCCESS;
resp[1] = NULL;
return PAM_SUCCESS;
default:
break;
}
}
return PAM_SUCCESS;
}
# endif
static const struct pam_conv conv = {
misc_conv,
NULL
};
#endif
enum {
TIMEOUT = 60,
EMPTY_USERNAME_COUNT = 10,
/* Some users found 32 chars limit to be too low: */
USERNAME_SIZE = 64,
TTYNAME_SIZE = 32,
};
struct globals {
struct termios tty_attrs;
} FIX_ALIASING;
#define G (*(struct globals*)bb_common_bufsiz1)
#define INIT_G() do { setup_common_bufsiz(); } while (0)
#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
# define die_if_nologin() ((void)0)
#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
#if ENABLE_LOGIN_SESSION_AS_CHILD && ENABLE_PAM
static void login_pam_end(pam_handle_t *pamh)
{
int pamret;
pamret = pam_setcred(pamh, PAM_DELETE_CRED);
if (pamret != PAM_SUCCESS) {
bb_error_msg("pam_%s failed: %s (%d)", "setcred",
pam_strerror(pamh, pamret), pamret);
}
pamret = pam_close_session(pamh, 0);
if (pamret != PAM_SUCCESS) {
bb_error_msg("pam_%s failed: %s (%d)", "close_session",
pam_strerror(pamh, pamret), pamret);
}
pamret = pam_end(pamh, pamret);
if (pamret != PAM_SUCCESS) {
bb_error_msg("pam_%s failed: %s (%d)", "end",
pam_strerror(pamh, pamret), pamret);
}
}
#else
# define login_pam_end(pamh) ((void)0)
#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(STDOUT_FILENO);
/* Test for correct attr restoring:
* run "getty 0 -" from a shell, enter bogus username, stop at
* password prompt, let it time out. Without the tcsetattr below,
* when you are back at shell prompt, echo will be still off.
*/
tcsetattr_stdin_TCSANOW(&G.tty_attrs);
printf("\r\nLogin timed out after %u 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(STDOUT_FILENO);
_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];
int run_by_root;
unsigned opt;
int count = 0;
struct passwd *pw;
char *opt_host = NULL;
char *opt_user = opt_user; /* for compiler */
char *full_tty;
char *short_tty;
IF_SELINUX(security_context_t user_sid = NULL;)
#if ENABLE_PAM
int pamret;
pam_handle_t *pamh;
const char *pamuser;
const char *failed_msg;
struct passwd pwdstruct;
char pwdbuf[256];
char **pamenv;
#endif
#if ENABLE_LOGIN_SESSION_AS_CHILD
pid_t child_pid;
#endif
INIT_G();
/* 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.
*/
bb_daemon_helper(DAEMON_CLOSE_EXTRA_FDS);
username[0] = '\0';
opt = getopt32(argv, "f:h:p", &opt_user, &opt_host);
if (opt & LOGIN_OPT_f) {
if (!run_by_root)
bb_simple_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));
/* Save tty attributes - and by doing it, check that it's indeed a tty */
if (tcgetattr(STDIN_FILENO, &G.tty_attrs) < 0
|| !isatty(STDOUT_FILENO)
/*|| !isatty(STDERR_FILENO) - no, guess some people might want to redirect this */
) {
return EXIT_FAILURE; /* Must be a terminal */
}
/* We install timeout handler only _after_ we saved G.tty_attrs */
signal(SIGALRM, alarm_handler);
alarm(TIMEOUT);
/* Find out and memorize our tty name */
full_tty = xmalloc_ttyname(STDIN_FILENO);
if (!full_tty)
full_tty = xstrdup("UNKNOWN");
short_tty = skip_dev_pfx(full_tty);
if (opt_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) */
tcflush(0, 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;
}
/* set RHOST */
if (opt_host) {
pamret = pam_set_item(pamh, PAM_RHOST, opt_host);
if (pamret != PAM_SUCCESS) {
failed_msg = "set_item(RHOST)";
goto pam_auth_failed;
}
}
if (!(opt & LOGIN_OPT_f)) {
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);
login_pam_end(pamh);
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 && !is_tty_secure(short_tty))
goto auth_failed;
/* Don't check the password if password entry is empty (!) */
if (!pw->pw_passwd[0])
break;
fake_it:
/* Password reading and authorization takes place here.
* Note that reads (in no-echo mode) trash tty attributes.
* If we get interrupted by SIGALRM, we need to restore attrs.
*/
if (ask_and_check_password(pw) > 0)
break;
#endif /* ENABLE_PAM */
auth_failed:
opt &= ~LOGIN_OPT_f;
bb_do_delay(LOGIN_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);
if (ENABLE_FEATURE_CLEAN_UP)
free(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();
#if ENABLE_LOGIN_SESSION_AS_CHILD
child_pid = vfork();
if (child_pid != 0) {
if (child_pid < 0)
bb_simple_perror_msg("vfork");
else {
wait_for_exitstatus(child_pid);
update_utmp_DEAD_PROCESS(child_pid);
}
login_pam_end(pamh);
return 0;
}
#endif
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);
update_utmp(getpid(), USER_PROCESS, short_tty, username, run_by_root ? opt_host : NULL);
/* 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);
setup_environment(pw->pw_shell,
(!(opt & LOGIN_OPT_p) * SETUP_ENV_CLEARENV) + SETUP_ENV_CHANGEENV,
pw);
#if ENABLE_PAM
/* Modules such as pam_env will setup the PAM environment,
* which should be copied into the new environment. */
pamenv = pam_getenvlist(pamh);
if (pamenv) while (*pamenv) {
putenv(*pamenv);
pamenv++;
}
#endif
if (access(".hushlogin", F_OK) != 0)
motd();
if (pw->pw_uid == 0)
syslog(LOG_INFO, "root login%s", fromhost);
if (ENABLE_FEATURE_CLEAN_UP)
free(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(pw->pw_shell, 1, NULL);
/* return EXIT_FAILURE; - not reached */
}