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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 | /* vi: set sw=4 ts=4: */ /* * Licensed under GPLv2 or later, see file LICENSE in this tarball for details. */ #include "libbb.h" #include <syslog.h> #if ENABLE_FEATURE_UTMP # include <utmp.h> /* USER_PROCESS */ #endif #include <sys/resource.h> #if ENABLE_SELINUX # include <selinux/selinux.h> /* for is_selinux_enabled() */ # include <selinux/get_context_list.h> /* for get_default_context() */ # include <selinux/flask.h> /* for security class definitions */ #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> static const struct pam_conv conv = { misc_conv, NULL }; #endif enum { TIMEOUT = 60, EMPTY_USERNAME_COUNT = 10, USERNAME_SIZE = 32, TTYNAME_SIZE = 32, }; static char* short_tty; #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_FEATURE_SECURETTY && !ENABLE_PAM static int check_securetty(void) { char *buf = (char*)"/etc/securetty"; /* any non-NULL is ok */ parser_t *parser = config_open2("/etc/securetty", fopen_for_read); while (config_read(parser, &buf, 1, 1, "# \t", PARSE_NORMAL)) { if (strcmp(buf, short_tty) == 0) break; buf = NULL; } config_close(parser); /* buf != NULL here if config file was not found, empty * or line was found which equals short_tty */ return buf != NULL; } #else static ALWAYS_INLINE int check_securetty(void) { return 1; } #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 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(1); printf("\r\nLogin timed out after %d 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(1); _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]; const char *shell; 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; 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]; #endif username[0] = '\0'; signal(SIGALRM, alarm_handler); alarm(TIMEOUT); /* 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. * (The name of the function is misleading. Not daemonizing here.) */ bb_daemonize_or_rexec(DAEMON_ONLY_SANITIZE | DAEMON_CLOSE_EXTRA_FDS, NULL); opt = getopt32(argv, "f:h:p", &opt_user, &opt_host); if (opt & LOGIN_OPT_f) { if (!run_by_root) bb_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)); /* Let's find out and memorize our tty */ if (!isatty(STDIN_FILENO) || !isatty(STDOUT_FILENO) || !isatty(STDERR_FILENO)) return EXIT_FAILURE; /* Must be a terminal */ 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) */ ioctl(0, TCFLSH, 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; } 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); 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 && !check_securetty()) goto auth_failed; /* Don't check the password if password entry is empty (!) */ if (!pw->pw_passwd[0]) break; fake_it: /* authorization takes place here */ if (correct_password(pw)) break; #endif /* ENABLE_PAM */ auth_failed: opt &= ~LOGIN_OPT_f; bb_do_delay(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); 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_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); shell = pw->pw_shell; if (!shell || !shell[0]) shell = DEFAULT_SHELL; setup_environment(shell, (!(opt & LOGIN_OPT_p) * SETUP_ENV_CLEARENV) + SETUP_ENV_CHANGEENV, pw); motd(); if (pw->pw_uid == 0) syslog(LOG_INFO, "root login%s", 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(shell, 1, NULL, NULL); /* return EXIT_FAILURE; - not reached */ } |