Loading...
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 | /* 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
IF_FEATURE_UTMP(pid_t my_pid;)
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;
pause_after_failed_login();
/* TODO: doesn't sound like correct English phrase to me */
puts("Login incorrect");
syslog(LOG_WARNING, "invalid password for '%s'%s",
username, fromhost);
if (++count == 3) {
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_FEATURE_UTMP(my_pid = getpid();)
update_utmp(my_pid, USER_PROCESS, short_tty, username, run_by_root ? opt_host : NULL);
#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(my_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);
/* 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 */
exec_login_shell(pw->pw_shell);
/* return EXIT_FAILURE; - not reached */
}
|