Contents of /tags/mkinitrd-6_2_2/busybox/loginutils/login.c
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Sun May 30 12:33:03 2010 UTC (14 years ago) by niro
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File size: 14433 byte(s)
Sun May 30 12:33:03 2010 UTC (14 years ago) by niro
File MIME type: text/plain
File size: 14433 byte(s)
tagged 'mkinitrd-6_2_2'
1 | /* vi: set sw=4 ts=4: */ |
2 | /* |
3 | * Licensed under GPLv2 or later, see file LICENSE in this tarball for details. |
4 | */ |
5 | |
6 | #include "libbb.h" |
7 | #include <syslog.h> |
8 | #include <utmp.h> |
9 | #include <sys/resource.h> |
10 | |
11 | #if ENABLE_SELINUX |
12 | #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 | #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 | enum { |
31 | TIMEOUT = 60, |
32 | EMPTY_USERNAME_COUNT = 10, |
33 | USERNAME_SIZE = 32, |
34 | TTYNAME_SIZE = 32, |
35 | }; |
36 | |
37 | static char* short_tty; |
38 | |
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 | static void read_or_build_utent(struct utmp *utptr, int run_by_root) |
56 | { |
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 | /* 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 | |
74 | // 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 | |
80 | /* 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 | } |
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 | static void write_utent(struct utmp *utptr, const char *username) |
99 | { |
100 | utptr->ut_type = USER_PROCESS; |
101 | strncpy(utptr->ut_user, username, sizeof(utptr->ut_user)); |
102 | utptr->ut_tv.tv_sec = time(NULL); |
103 | /* other fields already filled in by read_or_build_utent above */ |
104 | setutent(); |
105 | pututline(utptr); |
106 | 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 | updwtmp(bb_path_wtmp_file, utptr); |
112 | #endif |
113 | } |
114 | #else /* !ENABLE_FEATURE_UTMP */ |
115 | #define read_or_build_utent(utptr, run_by_root) ((void)0) |
116 | #define write_utent(utptr, username) ((void)0) |
117 | #endif /* !ENABLE_FEATURE_UTMP */ |
118 | |
119 | #if ENABLE_FEATURE_NOLOGIN |
120 | static void die_if_nologin(void) |
121 | { |
122 | FILE *fp; |
123 | int c; |
124 | int empty = 1; |
125 | |
126 | fp = fopen_for_read("/etc/nologin"); |
127 | if (!fp) /* assuming it does not exist */ |
128 | return; |
129 | |
130 | 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 | puts("\r\nSystem closed for routine maintenance\r"); |
138 | |
139 | fclose(fp); |
140 | fflush_all(); |
141 | /* Users say that they do need this prior to exit: */ |
142 | tcdrain(STDOUT_FILENO); |
143 | exit(EXIT_FAILURE); |
144 | } |
145 | #else |
146 | static ALWAYS_INLINE void die_if_nologin(void) {} |
147 | #endif |
148 | |
149 | #if ENABLE_FEATURE_SECURETTY && !ENABLE_PAM |
150 | static int check_securetty(void) |
151 | { |
152 | 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 | } |
159 | 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 | } |
164 | #else |
165 | static ALWAYS_INLINE int check_securetty(void) { return 1; } |
166 | #endif |
167 | |
168 | #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 | static void get_username_or_die(char *buf, int size_buf) |
219 | { |
220 | int c, cntdown; |
221 | |
222 | cntdown = EMPTY_USERNAME_COUNT; |
223 | prompt: |
224 | print_login_prompt(); |
225 | /* skip whitespace */ |
226 | do { |
227 | c = getchar(); |
228 | if (c == EOF) |
229 | exit(EXIT_FAILURE); |
230 | if (c == '\n') { |
231 | if (!--cntdown) |
232 | exit(EXIT_FAILURE); |
233 | goto prompt; |
234 | } |
235 | } while (isspace(c)); /* maybe isblank? */ |
236 | |
237 | *buf++ = c; |
238 | if (!fgets(buf, size_buf-2, stdin)) |
239 | exit(EXIT_FAILURE); |
240 | if (!strchr(buf, '\n')) |
241 | exit(EXIT_FAILURE); |
242 | while ((unsigned char)*buf > ' ') |
243 | buf++; |
244 | *buf = '\0'; |
245 | } |
246 | |
247 | static void motd(void) |
248 | { |
249 | int fd; |
250 | |
251 | fd = open(bb_path_motd_file, O_RDONLY); |
252 | if (fd >= 0) { |
253 | fflush_all(); |
254 | bb_copyfd_eof(fd, STDOUT_FILENO); |
255 | close(fd); |
256 | } |
257 | } |
258 | |
259 | static void alarm_handler(int sig UNUSED_PARAM) |
260 | { |
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 | ndelay_on(1); |
265 | printf("\r\nLogin timed out after %d seconds\r\n", TIMEOUT); |
266 | fflush_all(); |
267 | /* 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 | } |
272 | |
273 | int login_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE; |
274 | int login_main(int argc UNUSED_PARAM, char **argv) |
275 | { |
276 | enum { |
277 | LOGIN_OPT_f = (1<<0), |
278 | LOGIN_OPT_h = (1<<1), |
279 | LOGIN_OPT_p = (1<<2), |
280 | }; |
281 | char *fromhost; |
282 | char username[USERNAME_SIZE]; |
283 | const char *tmp; |
284 | int run_by_root; |
285 | unsigned opt; |
286 | int count = 0; |
287 | struct passwd *pw; |
288 | char *opt_host = opt_host; /* for compiler */ |
289 | char *opt_user = opt_user; /* for compiler */ |
290 | char *full_tty; |
291 | IF_SELINUX(security_context_t user_sid = NULL;) |
292 | IF_FEATURE_UTMP(struct utmp utent;) |
293 | #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 | |
302 | username[0] = '\0'; |
303 | signal(SIGALRM, alarm_handler); |
304 | alarm(TIMEOUT); |
305 | |
306 | /* 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 | if (opt & LOGIN_OPT_f) { |
318 | if (!run_by_root) |
319 | bb_error_msg_and_die("-f is for root only"); |
320 | safe_strncpy(username, opt_user, sizeof(username)); |
321 | } |
322 | argv += optind; |
323 | if (argv[0]) /* user from command line (getty) */ |
324 | safe_strncpy(username, argv[0], sizeof(username)); |
325 | |
326 | /* Let's find out and memorize our tty */ |
327 | if (!isatty(STDIN_FILENO) || !isatty(STDOUT_FILENO) || !isatty(STDERR_FILENO)) |
328 | return EXIT_FAILURE; /* Must be a terminal */ |
329 | 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 | |
336 | read_or_build_utent(&utent, run_by_root); |
337 | |
338 | if (opt & LOGIN_OPT_h) { |
339 | IF_FEATURE_UTMP(safe_strncpy(utent.ut_host, opt_host, sizeof(utent.ut_host));) |
340 | fromhost = xasprintf(" on '%s' from '%s'", short_tty, opt_host); |
341 | } else { |
342 | fromhost = xasprintf(" on '%s'", short_tty); |
343 | } |
344 | |
345 | /* Was breaking "login <username>" from shell command line: */ |
346 | /*bb_setpgrp();*/ |
347 | |
348 | openlog(applet_name, LOG_PID | LOG_CONS, LOG_AUTH); |
349 | |
350 | while (1) { |
351 | /* flush away any type-ahead (as getty does) */ |
352 | ioctl(0, TCFLSH, TCIFLUSH); |
353 | |
354 | if (!username[0]) |
355 | get_username_or_die(username, sizeof(username)); |
356 | |
357 | #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 | /* 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 | pam_strerror(pamh, pamret), pamret); |
419 | safe_strncpy(username, "UNKNOWN", sizeof(username)); |
420 | #else /* not PAM */ |
421 | pw = getpwnam(username); |
422 | if (!pw) { |
423 | strcpy(username, "UNKNOWN"); |
424 | goto fake_it; |
425 | } |
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 | fake_it: |
440 | /* authorization takes place here */ |
441 | if (correct_password(pw)) |
442 | break; |
443 | #endif /* ENABLE_PAM */ |
444 | auth_failed: |
445 | opt &= ~LOGIN_OPT_f; |
446 | bb_do_delay(FAIL_DELAY); |
447 | /* TODO: doesn't sound like correct English phrase to me */ |
448 | 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 | } /* while (1) */ |
456 | |
457 | alarm(0); |
458 | /* 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 | |
463 | write_utent(&utent, username); |
464 | |
465 | IF_SELINUX(initselinux(username, full_tty, &user_sid)); |
466 | |
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 | /* We trust environment only if we run by root */ |
473 | if (ENABLE_LOGIN_SCRIPTS && run_by_root) |
474 | run_login_script(pw, full_tty); |
475 | |
476 | change_identity(pw); |
477 | tmp = pw->pw_shell; |
478 | if (!tmp || !*tmp) |
479 | tmp = DEFAULT_SHELL; |
480 | /* setup_environment params: shell, clear_env, change_env, pw */ |
481 | setup_environment(tmp, !(opt & LOGIN_OPT_p), 1, pw); |
482 | |
483 | motd(); |
484 | |
485 | if (pw->pw_uid == 0) |
486 | syslog(LOG_INFO, "root login%s", fromhost); |
487 | |
488 | /* well, a simple setexeccon() here would do the job as well, |
489 | * but let's play the game for now */ |
490 | IF_SELINUX(set_current_security_context(user_sid);) |
491 | |
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 | // BBox login used to do this (see above): |
498 | // bb_setpgrp(); |
499 | // If this stuff is really needed, add it and explain why! |
500 | |
501 | /* Set signals to defaults */ |
502 | /* Non-ignored signals revert to SIG_DFL on exec anyway */ |
503 | /*signal(SIGALRM, SIG_DFL);*/ |
504 | |
505 | /* 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 | * should we leave SIGINT etc enabled or disabled? */ |
511 | signal(SIGINT, SIG_DFL); |
512 | |
513 | /* Exec login shell with no additional parameters */ |
514 | run_shell(tmp, 1, NULL, NULL); |
515 | |
516 | /* return EXIT_FAILURE; - not reached */ |
517 | } |