| /* 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 |
| |
| 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; |
| bb_do_delay(LOGIN_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); |
| |
| 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 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(child_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); |
| |
| 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); |
| 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 */ |
| run_shell(pw->pw_shell, 1, NULL); |
| |
| /* return EXIT_FAILURE; - not reached */ |
| } |