source: MondoRescue/branches/3.2/mindi-busybox/loginutils/login.c@ 3263

Last change on this file since 3263 was 3232, checked in by Bruno Cornec, 12 years ago
  • Update mindi-busybox to 1.21.1
File size: 14.0 KB
Line 
1/* vi: set sw=4 ts=4: */
2/*
3 * Licensed under GPLv2 or later, see file LICENSE in this source tree.
4 */
5
6//usage:#define login_trivial_usage
7//usage: "[-p] [-h HOST] [[-f] USER]"
8//usage:#define login_full_usage "\n\n"
9//usage: "Begin a new session on the system\n"
10//usage: "\n -f Don't authenticate (user already authenticated)"
11//usage: "\n -h Name of the remote host"
12//usage: "\n -p Preserve environment"
13
14#include "libbb.h"
15#include <syslog.h>
16#include <sys/resource.h>
17
18#if ENABLE_SELINUX
19# include <selinux/selinux.h> /* for is_selinux_enabled() */
20# include <selinux/get_context_list.h> /* for get_default_context() */
21# include <selinux/flask.h> /* for security class definitions */
22#endif
23
24#if ENABLE_PAM
25/* PAM may include <locale.h>. We may need to undefine bbox's stub define: */
26# undef setlocale
27/* For some obscure reason, PAM is not in pam/xxx, but in security/xxx.
28 * Apparently they like to confuse people. */
29# include <security/pam_appl.h>
30# include <security/pam_misc.h>
31static const struct pam_conv conv = {
32 misc_conv,
33 NULL
34};
35#endif
36
37enum {
38 TIMEOUT = 60,
39 EMPTY_USERNAME_COUNT = 10,
40 /* Some users found 32 chars limit to be too low: */
41 USERNAME_SIZE = 64,
42 TTYNAME_SIZE = 32,
43};
44
45struct globals {
46 struct termios tty_attrs;
47} FIX_ALIASING;
48#define G (*(struct globals*)&bb_common_bufsiz1)
49#define INIT_G() do { } while (0)
50
51
52#if ENABLE_FEATURE_NOLOGIN
53static void die_if_nologin(void)
54{
55 FILE *fp;
56 int c;
57 int empty = 1;
58
59 fp = fopen_for_read("/etc/nologin");
60 if (!fp) /* assuming it does not exist */
61 return;
62
63 while ((c = getc(fp)) != EOF) {
64 if (c == '\n')
65 bb_putchar('\r');
66 bb_putchar(c);
67 empty = 0;
68 }
69 if (empty)
70 puts("\r\nSystem closed for routine maintenance\r");
71
72 fclose(fp);
73 fflush_all();
74 /* Users say that they do need this prior to exit: */
75 tcdrain(STDOUT_FILENO);
76 exit(EXIT_FAILURE);
77}
78#else
79# define die_if_nologin() ((void)0)
80#endif
81
82#if ENABLE_FEATURE_SECURETTY && !ENABLE_PAM
83static int check_securetty(const char *short_tty)
84{
85 char *buf = (char*)"/etc/securetty"; /* any non-NULL is ok */
86 parser_t *parser = config_open2("/etc/securetty", fopen_for_read);
87 while (config_read(parser, &buf, 1, 1, "# \t", PARSE_NORMAL)) {
88 if (strcmp(buf, short_tty) == 0)
89 break;
90 buf = NULL;
91 }
92 config_close(parser);
93 /* buf != NULL here if config file was not found, empty
94 * or line was found which equals short_tty */
95 return buf != NULL;
96}
97#else
98static ALWAYS_INLINE int check_securetty(const char *short_tty UNUSED_PARAM) { return 1; }
99#endif
100
101#if ENABLE_SELINUX
102static void initselinux(char *username, char *full_tty,
103 security_context_t *user_sid)
104{
105 security_context_t old_tty_sid, new_tty_sid;
106
107 if (!is_selinux_enabled())
108 return;
109
110 if (get_default_context(username, NULL, user_sid)) {
111 bb_error_msg_and_die("can't get SID for %s", username);
112 }
113 if (getfilecon(full_tty, &old_tty_sid) < 0) {
114 bb_perror_msg_and_die("getfilecon(%s) failed", full_tty);
115 }
116 if (security_compute_relabel(*user_sid, old_tty_sid,
117 SECCLASS_CHR_FILE, &new_tty_sid) != 0) {
118 bb_perror_msg_and_die("security_change_sid(%s) failed", full_tty);
119 }
120 if (setfilecon(full_tty, new_tty_sid) != 0) {
121 bb_perror_msg_and_die("chsid(%s, %s) failed", full_tty, new_tty_sid);
122 }
123}
124#endif
125
126#if ENABLE_LOGIN_SCRIPTS
127static void run_login_script(struct passwd *pw, char *full_tty)
128{
129 char *t_argv[2];
130
131 t_argv[0] = getenv("LOGIN_PRE_SUID_SCRIPT");
132 if (t_argv[0]) {
133 t_argv[1] = NULL;
134 xsetenv("LOGIN_TTY", full_tty);
135 xsetenv("LOGIN_USER", pw->pw_name);
136 xsetenv("LOGIN_UID", utoa(pw->pw_uid));
137 xsetenv("LOGIN_GID", utoa(pw->pw_gid));
138 xsetenv("LOGIN_SHELL", pw->pw_shell);
139 spawn_and_wait(t_argv); /* NOMMU-friendly */
140 unsetenv("LOGIN_TTY");
141 unsetenv("LOGIN_USER");
142 unsetenv("LOGIN_UID");
143 unsetenv("LOGIN_GID");
144 unsetenv("LOGIN_SHELL");
145 }
146}
147#else
148void run_login_script(struct passwd *pw, char *full_tty);
149#endif
150
151#if ENABLE_LOGIN_SESSION_AS_CHILD && ENABLE_PAM
152static void login_pam_end(pam_handle_t *pamh)
153{
154 int pamret;
155
156 pamret = pam_setcred(pamh, PAM_DELETE_CRED);
157 if (pamret != PAM_SUCCESS) {
158 bb_error_msg("pam_%s failed: %s (%d)", "setcred",
159 pam_strerror(pamh, pamret), pamret);
160 }
161 pamret = pam_close_session(pamh, 0);
162 if (pamret != PAM_SUCCESS) {
163 bb_error_msg("pam_%s failed: %s (%d)", "close_session",
164 pam_strerror(pamh, pamret), pamret);
165 }
166 pamret = pam_end(pamh, pamret);
167 if (pamret != PAM_SUCCESS) {
168 bb_error_msg("pam_%s failed: %s (%d)", "end",
169 pam_strerror(pamh, pamret), pamret);
170 }
171}
172#endif /* ENABLE_PAM */
173
174static void get_username_or_die(char *buf, int size_buf)
175{
176 int c, cntdown;
177
178 cntdown = EMPTY_USERNAME_COUNT;
179 prompt:
180 print_login_prompt();
181 /* skip whitespace */
182 do {
183 c = getchar();
184 if (c == EOF)
185 exit(EXIT_FAILURE);
186 if (c == '\n') {
187 if (!--cntdown)
188 exit(EXIT_FAILURE);
189 goto prompt;
190 }
191 } while (isspace(c)); /* maybe isblank? */
192
193 *buf++ = c;
194 if (!fgets(buf, size_buf-2, stdin))
195 exit(EXIT_FAILURE);
196 if (!strchr(buf, '\n'))
197 exit(EXIT_FAILURE);
198 while ((unsigned char)*buf > ' ')
199 buf++;
200 *buf = '\0';
201}
202
203static void motd(void)
204{
205 int fd;
206
207 fd = open(bb_path_motd_file, O_RDONLY);
208 if (fd >= 0) {
209 fflush_all();
210 bb_copyfd_eof(fd, STDOUT_FILENO);
211 close(fd);
212 }
213}
214
215static void alarm_handler(int sig UNUSED_PARAM)
216{
217 /* This is the escape hatch! Poor serial line users and the like
218 * arrive here when their connection is broken.
219 * We don't want to block here */
220 ndelay_on(STDOUT_FILENO);
221 /* Test for correct attr restoring:
222 * run "getty 0 -" from a shell, enter bogus username, stop at
223 * password prompt, let it time out. Without the tcsetattr below,
224 * when you are back at shell prompt, echo will be still off.
225 */
226 tcsetattr_stdin_TCSANOW(&G.tty_attrs);
227 printf("\r\nLogin timed out after %u seconds\r\n", TIMEOUT);
228 fflush_all();
229 /* unix API is brain damaged regarding O_NONBLOCK,
230 * we should undo it, or else we can affect other processes */
231 ndelay_off(STDOUT_FILENO);
232 _exit(EXIT_SUCCESS);
233}
234
235int login_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
236int login_main(int argc UNUSED_PARAM, char **argv)
237{
238 enum {
239 LOGIN_OPT_f = (1<<0),
240 LOGIN_OPT_h = (1<<1),
241 LOGIN_OPT_p = (1<<2),
242 };
243 char *fromhost;
244 char username[USERNAME_SIZE];
245 int run_by_root;
246 unsigned opt;
247 int count = 0;
248 struct passwd *pw;
249 char *opt_host = NULL;
250 char *opt_user = opt_user; /* for compiler */
251 char *full_tty;
252 char *short_tty;
253 IF_SELINUX(security_context_t user_sid = NULL;)
254#if ENABLE_PAM
255 int pamret;
256 pam_handle_t *pamh;
257 const char *pamuser;
258 const char *failed_msg;
259 struct passwd pwdstruct;
260 char pwdbuf[256];
261 char **pamenv;
262#endif
263#if ENABLE_LOGIN_SESSION_AS_CHILD
264 pid_t child_pid;
265#endif
266
267 INIT_G();
268
269 /* More of suid paranoia if called by non-root: */
270 /* Clear dangerous stuff, set PATH */
271 run_by_root = !sanitize_env_if_suid();
272
273 /* Mandatory paranoia for suid applet:
274 * ensure that fd# 0,1,2 are opened (at least to /dev/null)
275 * and any extra open fd's are closed.
276 * (The name of the function is misleading. Not daemonizing here.) */
277 bb_daemonize_or_rexec(DAEMON_ONLY_SANITIZE | DAEMON_CLOSE_EXTRA_FDS, NULL);
278
279 username[0] = '\0';
280 opt = getopt32(argv, "f:h:p", &opt_user, &opt_host);
281 if (opt & LOGIN_OPT_f) {
282 if (!run_by_root)
283 bb_error_msg_and_die("-f is for root only");
284 safe_strncpy(username, opt_user, sizeof(username));
285 }
286 argv += optind;
287 if (argv[0]) /* user from command line (getty) */
288 safe_strncpy(username, argv[0], sizeof(username));
289
290 /* Save tty attributes - and by doing it, check that it's indeed a tty */
291 if (tcgetattr(STDIN_FILENO, &G.tty_attrs) < 0
292 || !isatty(STDOUT_FILENO)
293 /*|| !isatty(STDERR_FILENO) - no, guess some people might want to redirect this */
294 ) {
295 return EXIT_FAILURE; /* Must be a terminal */
296 }
297
298 /* We install timeout handler only _after_ we saved G.tty_attrs */
299 signal(SIGALRM, alarm_handler);
300 alarm(TIMEOUT);
301
302 /* Find out and memorize our tty name */
303 full_tty = xmalloc_ttyname(STDIN_FILENO);
304 if (!full_tty)
305 full_tty = xstrdup("UNKNOWN");
306 short_tty = skip_dev_pfx(full_tty);
307
308 if (opt_host) {
309 fromhost = xasprintf(" on '%s' from '%s'", short_tty, opt_host);
310 } else {
311 fromhost = xasprintf(" on '%s'", short_tty);
312 }
313
314 /* Was breaking "login <username>" from shell command line: */
315 /*bb_setpgrp();*/
316
317 openlog(applet_name, LOG_PID | LOG_CONS, LOG_AUTH);
318
319 while (1) {
320 /* flush away any type-ahead (as getty does) */
321 tcflush(0, TCIFLUSH);
322
323 if (!username[0])
324 get_username_or_die(username, sizeof(username));
325
326#if ENABLE_PAM
327 pamret = pam_start("login", username, &conv, &pamh);
328 if (pamret != PAM_SUCCESS) {
329 failed_msg = "start";
330 goto pam_auth_failed;
331 }
332 /* set TTY (so things like securetty work) */
333 pamret = pam_set_item(pamh, PAM_TTY, short_tty);
334 if (pamret != PAM_SUCCESS) {
335 failed_msg = "set_item(TTY)";
336 goto pam_auth_failed;
337 }
338 /* set RHOST */
339 if (opt_host) {
340 pamret = pam_set_item(pamh, PAM_RHOST, opt_host);
341 if (pamret != PAM_SUCCESS) {
342 failed_msg = "set_item(RHOST)";
343 goto pam_auth_failed;
344 }
345 }
346 if (!(opt & LOGIN_OPT_f)) {
347 pamret = pam_authenticate(pamh, 0);
348 if (pamret != PAM_SUCCESS) {
349 failed_msg = "authenticate";
350 goto pam_auth_failed;
351 /* TODO: or just "goto auth_failed"
352 * since user seems to enter wrong password
353 * (in this case pamret == 7)
354 */
355 }
356 }
357 /* check that the account is healthy */
358 pamret = pam_acct_mgmt(pamh, 0);
359 if (pamret != PAM_SUCCESS) {
360 failed_msg = "acct_mgmt";
361 goto pam_auth_failed;
362 }
363 /* read user back */
364 pamuser = NULL;
365 /* gcc: "dereferencing type-punned pointer breaks aliasing rules..."
366 * thus we cast to (void*) */
367 if (pam_get_item(pamh, PAM_USER, (void*)&pamuser) != PAM_SUCCESS) {
368 failed_msg = "get_item(USER)";
369 goto pam_auth_failed;
370 }
371 if (!pamuser || !pamuser[0])
372 goto auth_failed;
373 safe_strncpy(username, pamuser, sizeof(username));
374 /* Don't use "pw = getpwnam(username);",
375 * PAM is said to be capable of destroying static storage
376 * used by getpwnam(). We are using safe(r) function */
377 pw = NULL;
378 getpwnam_r(username, &pwdstruct, pwdbuf, sizeof(pwdbuf), &pw);
379 if (!pw)
380 goto auth_failed;
381 pamret = pam_open_session(pamh, 0);
382 if (pamret != PAM_SUCCESS) {
383 failed_msg = "open_session";
384 goto pam_auth_failed;
385 }
386 pamret = pam_setcred(pamh, PAM_ESTABLISH_CRED);
387 if (pamret != PAM_SUCCESS) {
388 failed_msg = "setcred";
389 goto pam_auth_failed;
390 }
391 break; /* success, continue login process */
392
393 pam_auth_failed:
394 /* syslog, because we don't want potential attacker
395 * to know _why_ login failed */
396 syslog(LOG_WARNING, "pam_%s call failed: %s (%d)", failed_msg,
397 pam_strerror(pamh, pamret), pamret);
398 safe_strncpy(username, "UNKNOWN", sizeof(username));
399#else /* not PAM */
400 pw = getpwnam(username);
401 if (!pw) {
402 strcpy(username, "UNKNOWN");
403 goto fake_it;
404 }
405
406 if (pw->pw_passwd[0] == '!' || pw->pw_passwd[0] == '*')
407 goto auth_failed;
408
409 if (opt & LOGIN_OPT_f)
410 break; /* -f USER: success without asking passwd */
411
412 if (pw->pw_uid == 0 && !check_securetty(short_tty))
413 goto auth_failed;
414
415 /* Don't check the password if password entry is empty (!) */
416 if (!pw->pw_passwd[0])
417 break;
418 fake_it:
419 /* Password reading and authorization takes place here.
420 * Note that reads (in no-echo mode) trash tty attributes.
421 * If we get interrupted by SIGALRM, we need to restore attrs.
422 */
423 if (correct_password(pw))
424 break;
425#endif /* ENABLE_PAM */
426 auth_failed:
427 opt &= ~LOGIN_OPT_f;
428 bb_do_delay(LOGIN_FAIL_DELAY);
429 /* TODO: doesn't sound like correct English phrase to me */
430 puts("Login incorrect");
431 if (++count == 3) {
432 syslog(LOG_WARNING, "invalid password for '%s'%s",
433 username, fromhost);
434
435 if (ENABLE_FEATURE_CLEAN_UP)
436 free(fromhost);
437
438 return EXIT_FAILURE;
439 }
440 username[0] = '\0';
441 } /* while (1) */
442
443 alarm(0);
444 /* We can ignore /etc/nologin if we are logging in as root,
445 * it doesn't matter whether we are run by root or not */
446 if (pw->pw_uid != 0)
447 die_if_nologin();
448
449#if ENABLE_LOGIN_SESSION_AS_CHILD
450 child_pid = vfork();
451 if (child_pid != 0) {
452 if (child_pid < 0)
453 bb_perror_msg("vfork");
454 else {
455 if (safe_waitpid(child_pid, NULL, 0) == -1)
456 bb_perror_msg("waitpid");
457 update_utmp(child_pid, DEAD_PROCESS, NULL, NULL, NULL);
458 }
459 IF_PAM(login_pam_end(pamh);)
460 return 0;
461 }
462#endif
463
464 IF_SELINUX(initselinux(username, full_tty, &user_sid);)
465
466 /* Try these, but don't complain if they fail.
467 * _f_chown is safe wrt race t=ttyname(0);...;chown(t); */
468 fchown(0, pw->pw_uid, pw->pw_gid);
469 fchmod(0, 0600);
470
471 update_utmp(getpid(), USER_PROCESS, short_tty, username, run_by_root ? opt_host : NULL);
472
473 /* We trust environment only if we run by root */
474 if (ENABLE_LOGIN_SCRIPTS && run_by_root)
475 run_login_script(pw, full_tty);
476
477 change_identity(pw);
478 setup_environment(pw->pw_shell,
479 (!(opt & LOGIN_OPT_p) * SETUP_ENV_CLEARENV) + SETUP_ENV_CHANGEENV,
480 pw);
481
482#if ENABLE_PAM
483 /* Modules such as pam_env will setup the PAM environment,
484 * which should be copied into the new environment. */
485 pamenv = pam_getenvlist(pamh);
486 if (pamenv) while (*pamenv) {
487 putenv(*pamenv);
488 pamenv++;
489 }
490#endif
491
492 motd();
493
494 if (pw->pw_uid == 0)
495 syslog(LOG_INFO, "root login%s", fromhost);
496
497 if (ENABLE_FEATURE_CLEAN_UP)
498 free(fromhost);
499
500 /* well, a simple setexeccon() here would do the job as well,
501 * but let's play the game for now */
502 IF_SELINUX(set_current_security_context(user_sid);)
503
504 // util-linux login also does:
505 // /* start new session */
506 // setsid();
507 // /* TIOCSCTTY: steal tty from other process group */
508 // if (ioctl(0, TIOCSCTTY, 1)) error_msg...
509 // BBox login used to do this (see above):
510 // bb_setpgrp();
511 // If this stuff is really needed, add it and explain why!
512
513 /* Set signals to defaults */
514 /* Non-ignored signals revert to SIG_DFL on exec anyway */
515 /*signal(SIGALRM, SIG_DFL);*/
516
517 /* Is this correct? This way user can ctrl-c out of /etc/profile,
518 * potentially creating security breach (tested with bash 3.0).
519 * But without this, bash 3.0 will not enable ctrl-c either.
520 * Maybe bash is buggy?
521 * Need to find out what standards say about /bin/login -
522 * should we leave SIGINT etc enabled or disabled? */
523 signal(SIGINT, SIG_DFL);
524
525 /* Exec login shell with no additional parameters */
526 run_shell(pw->pw_shell, 1, NULL, NULL);
527
528 /* return EXIT_FAILURE; - not reached */
529}
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