source: MondoRescue/branches/2.2.9/mindi-busybox/loginutils/login.c@ 3320

Last change on this file since 3320 was 3320, checked in by Bruno Cornec, 9 years ago
  • Re-add (thanks git BTW) the 2.2.9 branch which had been destroyed in the move to 3.0
  • Property svn:eol-style set to native
File size: 11.4 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#include "libbb.h"
6#include <syslog.h>
7#if ENABLE_FEATURE_UTMP
8# include <utmp.h> /* USER_PROCESS */
9#endif
10#include <sys/resource.h>
11
12#if ENABLE_SELINUX
13# include <selinux/selinux.h> /* for is_selinux_enabled() */
14# include <selinux/get_context_list.h> /* for get_default_context() */
15# include <selinux/flask.h> /* for security class definitions */
16#endif
17
18#if ENABLE_PAM
19/* PAM may include <locale.h>. We may need to undefine bbox's stub define: */
20# undef setlocale
21/* For some obscure reason, PAM is not in pam/xxx, but in security/xxx.
22 * Apparently they like to confuse people. */
23# include <security/pam_appl.h>
24# include <security/pam_misc.h>
25static const struct pam_conv conv = {
26 misc_conv,
27 NULL
28};
29#endif
30
31enum {
32 TIMEOUT = 60,
33 EMPTY_USERNAME_COUNT = 10,
34 USERNAME_SIZE = 32,
35 TTYNAME_SIZE = 32,
36};
37
38static char* short_tty;
39
40#if ENABLE_FEATURE_NOLOGIN
41static void die_if_nologin(void)
42{
43 FILE *fp;
44 int c;
45 int empty = 1;
46
47 fp = fopen_for_read("/etc/nologin");
48 if (!fp) /* assuming it does not exist */
49 return;
50
51 while ((c = getc(fp)) != EOF) {
52 if (c == '\n')
53 bb_putchar('\r');
54 bb_putchar(c);
55 empty = 0;
56 }
57 if (empty)
58 puts("\r\nSystem closed for routine maintenance\r");
59
60 fclose(fp);
61 fflush_all();
62 /* Users say that they do need this prior to exit: */
63 tcdrain(STDOUT_FILENO);
64 exit(EXIT_FAILURE);
65}
66#else
67# define die_if_nologin() ((void)0)
68#endif
69
70#if ENABLE_FEATURE_SECURETTY && !ENABLE_PAM
71static int check_securetty(void)
72{
73 char *buf = (char*)"/etc/securetty"; /* any non-NULL is ok */
74 parser_t *parser = config_open2("/etc/securetty", fopen_for_read);
75 while (config_read(parser, &buf, 1, 1, "# \t", PARSE_NORMAL)) {
76 if (strcmp(buf, short_tty) == 0)
77 break;
78 buf = NULL;
79 }
80 config_close(parser);
81 /* buf != NULL here if config file was not found, empty
82 * or line was found which equals short_tty */
83 return buf != NULL;
84}
85#else
86static ALWAYS_INLINE int check_securetty(void) { return 1; }
87#endif
88
89#if ENABLE_SELINUX
90static void initselinux(char *username, char *full_tty,
91 security_context_t *user_sid)
92{
93 security_context_t old_tty_sid, new_tty_sid;
94
95 if (!is_selinux_enabled())
96 return;
97
98 if (get_default_context(username, NULL, user_sid)) {
99 bb_error_msg_and_die("can't get SID for %s", username);
100 }
101 if (getfilecon(full_tty, &old_tty_sid) < 0) {
102 bb_perror_msg_and_die("getfilecon(%s) failed", full_tty);
103 }
104 if (security_compute_relabel(*user_sid, old_tty_sid,
105 SECCLASS_CHR_FILE, &new_tty_sid) != 0) {
106 bb_perror_msg_and_die("security_change_sid(%s) failed", full_tty);
107 }
108 if (setfilecon(full_tty, new_tty_sid) != 0) {
109 bb_perror_msg_and_die("chsid(%s, %s) failed", full_tty, new_tty_sid);
110 }
111}
112#endif
113
114#if ENABLE_LOGIN_SCRIPTS
115static void run_login_script(struct passwd *pw, char *full_tty)
116{
117 char *t_argv[2];
118
119 t_argv[0] = getenv("LOGIN_PRE_SUID_SCRIPT");
120 if (t_argv[0]) {
121 t_argv[1] = NULL;
122 xsetenv("LOGIN_TTY", full_tty);
123 xsetenv("LOGIN_USER", pw->pw_name);
124 xsetenv("LOGIN_UID", utoa(pw->pw_uid));
125 xsetenv("LOGIN_GID", utoa(pw->pw_gid));
126 xsetenv("LOGIN_SHELL", pw->pw_shell);
127 spawn_and_wait(t_argv); /* NOMMU-friendly */
128 unsetenv("LOGIN_TTY");
129 unsetenv("LOGIN_USER");
130 unsetenv("LOGIN_UID");
131 unsetenv("LOGIN_GID");
132 unsetenv("LOGIN_SHELL");
133 }
134}
135#else
136void run_login_script(struct passwd *pw, char *full_tty);
137#endif
138
139static void get_username_or_die(char *buf, int size_buf)
140{
141 int c, cntdown;
142
143 cntdown = EMPTY_USERNAME_COUNT;
144 prompt:
145 print_login_prompt();
146 /* skip whitespace */
147 do {
148 c = getchar();
149 if (c == EOF)
150 exit(EXIT_FAILURE);
151 if (c == '\n') {
152 if (!--cntdown)
153 exit(EXIT_FAILURE);
154 goto prompt;
155 }
156 } while (isspace(c)); /* maybe isblank? */
157
158 *buf++ = c;
159 if (!fgets(buf, size_buf-2, stdin))
160 exit(EXIT_FAILURE);
161 if (!strchr(buf, '\n'))
162 exit(EXIT_FAILURE);
163 while ((unsigned char)*buf > ' ')
164 buf++;
165 *buf = '\0';
166}
167
168static void motd(void)
169{
170 int fd;
171
172 fd = open(bb_path_motd_file, O_RDONLY);
173 if (fd >= 0) {
174 fflush_all();
175 bb_copyfd_eof(fd, STDOUT_FILENO);
176 close(fd);
177 }
178}
179
180static void alarm_handler(int sig UNUSED_PARAM)
181{
182 /* This is the escape hatch! Poor serial line users and the like
183 * arrive here when their connection is broken.
184 * We don't want to block here */
185 ndelay_on(1);
186 printf("\r\nLogin timed out after %d seconds\r\n", TIMEOUT);
187 fflush_all();
188 /* unix API is brain damaged regarding O_NONBLOCK,
189 * we should undo it, or else we can affect other processes */
190 ndelay_off(1);
191 _exit(EXIT_SUCCESS);
192}
193
194int login_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
195int login_main(int argc UNUSED_PARAM, char **argv)
196{
197 enum {
198 LOGIN_OPT_f = (1<<0),
199 LOGIN_OPT_h = (1<<1),
200 LOGIN_OPT_p = (1<<2),
201 };
202 char *fromhost;
203 char username[USERNAME_SIZE];
204 const char *shell;
205 int run_by_root;
206 unsigned opt;
207 int count = 0;
208 struct passwd *pw;
209 char *opt_host = NULL;
210 char *opt_user = opt_user; /* for compiler */
211 char *full_tty;
212 IF_SELINUX(security_context_t user_sid = NULL;)
213#if ENABLE_PAM
214 int pamret;
215 pam_handle_t *pamh;
216 const char *pamuser;
217 const char *failed_msg;
218 struct passwd pwdstruct;
219 char pwdbuf[256];
220#endif
221
222 username[0] = '\0';
223 signal(SIGALRM, alarm_handler);
224 alarm(TIMEOUT);
225
226 /* More of suid paranoia if called by non-root: */
227 /* Clear dangerous stuff, set PATH */
228 run_by_root = !sanitize_env_if_suid();
229
230 /* Mandatory paranoia for suid applet:
231 * ensure that fd# 0,1,2 are opened (at least to /dev/null)
232 * and any extra open fd's are closed.
233 * (The name of the function is misleading. Not daemonizing here.) */
234 bb_daemonize_or_rexec(DAEMON_ONLY_SANITIZE | DAEMON_CLOSE_EXTRA_FDS, NULL);
235
236 opt = getopt32(argv, "f:h:p", &opt_user, &opt_host);
237 if (opt & LOGIN_OPT_f) {
238 if (!run_by_root)
239 bb_error_msg_and_die("-f is for root only");
240 safe_strncpy(username, opt_user, sizeof(username));
241 }
242 argv += optind;
243 if (argv[0]) /* user from command line (getty) */
244 safe_strncpy(username, argv[0], sizeof(username));
245
246 /* Let's find out and memorize our tty */
247 if (!isatty(STDIN_FILENO) || !isatty(STDOUT_FILENO) || !isatty(STDERR_FILENO))
248 return EXIT_FAILURE; /* Must be a terminal */
249 full_tty = xmalloc_ttyname(STDIN_FILENO);
250 if (!full_tty)
251 full_tty = xstrdup("UNKNOWN");
252 short_tty = skip_dev_pfx(full_tty);
253
254 if (opt_host) {
255 fromhost = xasprintf(" on '%s' from '%s'", short_tty, opt_host);
256 } else {
257 fromhost = xasprintf(" on '%s'", short_tty);
258 }
259
260 /* Was breaking "login <username>" from shell command line: */
261 /*bb_setpgrp();*/
262
263 openlog(applet_name, LOG_PID | LOG_CONS, LOG_AUTH);
264
265 while (1) {
266 /* flush away any type-ahead (as getty does) */
267 tcflush(0, TCIFLUSH);
268
269 if (!username[0])
270 get_username_or_die(username, sizeof(username));
271
272#if ENABLE_PAM
273 pamret = pam_start("login", username, &conv, &pamh);
274 if (pamret != PAM_SUCCESS) {
275 failed_msg = "start";
276 goto pam_auth_failed;
277 }
278 /* set TTY (so things like securetty work) */
279 pamret = pam_set_item(pamh, PAM_TTY, short_tty);
280 if (pamret != PAM_SUCCESS) {
281 failed_msg = "set_item(TTY)";
282 goto pam_auth_failed;
283 }
284 pamret = pam_authenticate(pamh, 0);
285 if (pamret != PAM_SUCCESS) {
286 failed_msg = "authenticate";
287 goto pam_auth_failed;
288 /* TODO: or just "goto auth_failed"
289 * since user seems to enter wrong password
290 * (in this case pamret == 7)
291 */
292 }
293 /* check that the account is healthy */
294 pamret = pam_acct_mgmt(pamh, 0);
295 if (pamret != PAM_SUCCESS) {
296 failed_msg = "acct_mgmt";
297 goto pam_auth_failed;
298 }
299 /* read user back */
300 pamuser = NULL;
301 /* gcc: "dereferencing type-punned pointer breaks aliasing rules..."
302 * thus we cast to (void*) */
303 if (pam_get_item(pamh, PAM_USER, (void*)&pamuser) != PAM_SUCCESS) {
304 failed_msg = "get_item(USER)";
305 goto pam_auth_failed;
306 }
307 if (!pamuser || !pamuser[0])
308 goto auth_failed;
309 safe_strncpy(username, pamuser, sizeof(username));
310 /* Don't use "pw = getpwnam(username);",
311 * PAM is said to be capable of destroying static storage
312 * used by getpwnam(). We are using safe(r) function */
313 pw = NULL;
314 getpwnam_r(username, &pwdstruct, pwdbuf, sizeof(pwdbuf), &pw);
315 if (!pw)
316 goto auth_failed;
317 pamret = pam_open_session(pamh, 0);
318 if (pamret != PAM_SUCCESS) {
319 failed_msg = "open_session";
320 goto pam_auth_failed;
321 }
322 pamret = pam_setcred(pamh, PAM_ESTABLISH_CRED);
323 if (pamret != PAM_SUCCESS) {
324 failed_msg = "setcred";
325 goto pam_auth_failed;
326 }
327 break; /* success, continue login process */
328
329 pam_auth_failed:
330 /* syslog, because we don't want potential attacker
331 * to know _why_ login failed */
332 syslog(LOG_WARNING, "pam_%s call failed: %s (%d)", failed_msg,
333 pam_strerror(pamh, pamret), pamret);
334 safe_strncpy(username, "UNKNOWN", sizeof(username));
335#else /* not PAM */
336 pw = getpwnam(username);
337 if (!pw) {
338 strcpy(username, "UNKNOWN");
339 goto fake_it;
340 }
341
342 if (pw->pw_passwd[0] == '!' || pw->pw_passwd[0] == '*')
343 goto auth_failed;
344
345 if (opt & LOGIN_OPT_f)
346 break; /* -f USER: success without asking passwd */
347
348 if (pw->pw_uid == 0 && !check_securetty())
349 goto auth_failed;
350
351 /* Don't check the password if password entry is empty (!) */
352 if (!pw->pw_passwd[0])
353 break;
354 fake_it:
355 /* authorization takes place here */
356 if (correct_password(pw))
357 break;
358#endif /* ENABLE_PAM */
359 auth_failed:
360 opt &= ~LOGIN_OPT_f;
361 bb_do_delay(FAIL_DELAY);
362 /* TODO: doesn't sound like correct English phrase to me */
363 puts("Login incorrect");
364 if (++count == 3) {
365 syslog(LOG_WARNING, "invalid password for '%s'%s",
366 username, fromhost);
367
368 if (ENABLE_FEATURE_CLEAN_UP)
369 free(fromhost);
370
371 return EXIT_FAILURE;
372 }
373 username[0] = '\0';
374 } /* while (1) */
375
376 alarm(0);
377 /* We can ignore /etc/nologin if we are logging in as root,
378 * it doesn't matter whether we are run by root or not */
379 if (pw->pw_uid != 0)
380 die_if_nologin();
381
382 IF_SELINUX(initselinux(username, full_tty, &user_sid));
383
384 /* Try these, but don't complain if they fail.
385 * _f_chown is safe wrt race t=ttyname(0);...;chown(t); */
386 fchown(0, pw->pw_uid, pw->pw_gid);
387 fchmod(0, 0600);
388
389 update_utmp(getpid(), USER_PROCESS, short_tty, username, run_by_root ? opt_host : NULL);
390
391 /* We trust environment only if we run by root */
392 if (ENABLE_LOGIN_SCRIPTS && run_by_root)
393 run_login_script(pw, full_tty);
394
395 change_identity(pw);
396 shell = pw->pw_shell;
397 if (!shell || !shell[0])
398 shell = DEFAULT_SHELL;
399 setup_environment(shell,
400 (!(opt & LOGIN_OPT_p) * SETUP_ENV_CLEARENV) + SETUP_ENV_CHANGEENV,
401 pw);
402
403 motd();
404
405 if (pw->pw_uid == 0)
406 syslog(LOG_INFO, "root login%s", fromhost);
407
408 if (ENABLE_FEATURE_CLEAN_UP)
409 free(fromhost);
410
411 /* well, a simple setexeccon() here would do the job as well,
412 * but let's play the game for now */
413 IF_SELINUX(set_current_security_context(user_sid);)
414
415 // util-linux login also does:
416 // /* start new session */
417 // setsid();
418 // /* TIOCSCTTY: steal tty from other process group */
419 // if (ioctl(0, TIOCSCTTY, 1)) error_msg...
420 // BBox login used to do this (see above):
421 // bb_setpgrp();
422 // If this stuff is really needed, add it and explain why!
423
424 /* Set signals to defaults */
425 /* Non-ignored signals revert to SIG_DFL on exec anyway */
426 /*signal(SIGALRM, SIG_DFL);*/
427
428 /* Is this correct? This way user can ctrl-c out of /etc/profile,
429 * potentially creating security breach (tested with bash 3.0).
430 * But without this, bash 3.0 will not enable ctrl-c either.
431 * Maybe bash is buggy?
432 * Need to find out what standards say about /bin/login -
433 * should we leave SIGINT etc enabled or disabled? */
434 signal(SIGINT, SIG_DFL);
435
436 /* Exec login shell with no additional parameters */
437 run_shell(shell, 1, NULL, NULL);
438
439 /* return EXIT_FAILURE; - not reached */
440}
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