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- /* 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>
- #include <utmp.h>
- #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_UTMP
- /* vv Taken from tinylogin utmp.c vv */
- /*
- * read_or_build_utent - see if utmp file is correct for this process
- *
- * System V is very picky about the contents of the utmp file
- * and requires that a slot for the current process exist.
- * The utmp file is scanned for an entry with the same process
- * ID. If no entry exists the process exits with a message.
- *
- * The "picky" flag is for network and other logins that may
- * use special flags. It allows the pid checks to be overridden.
- * This means that getty should never invoke login with any
- * command line flags.
- */
- static void read_or_build_utent(struct utmp *utptr, int picky)
- {
- struct utmp *ut;
- pid_t pid = getpid();
- setutent();
- /* First, try to find a valid utmp entry for this process. */
- while ((ut = getutent()))
- if (ut->ut_pid == pid && ut->ut_line[0] && ut->ut_id[0] &&
- (ut->ut_type == LOGIN_PROCESS || ut->ut_type == USER_PROCESS))
- break;
- /* If there is one, just use it, otherwise create a new one. */
- if (ut) {
- *utptr = *ut;
- } else {
- if (picky)
- bb_error_msg_and_die("no utmp entry found");
- memset(utptr, 0, sizeof(*utptr));
- utptr->ut_type = LOGIN_PROCESS;
- utptr->ut_pid = pid;
- strncpy(utptr->ut_line, short_tty, sizeof(utptr->ut_line));
- /* This one is only 4 chars wide. Try to fit something
- * remotely meaningful by skipping "tty"... */
- strncpy(utptr->ut_id, short_tty + 3, sizeof(utptr->ut_id));
- strncpy(utptr->ut_user, "LOGIN", sizeof(utptr->ut_user));
- utptr->ut_time = time(NULL);
- }
- if (!picky) /* root login */
- memset(utptr->ut_host, 0, sizeof(utptr->ut_host));
- }
- /*
- * write_utent - put a USER_PROCESS entry in the utmp file
- *
- * write_utent changes the type of the current utmp entry to
- * USER_PROCESS. the wtmp file will be updated as well.
- */
- static void write_utent(struct utmp *utptr, const char *username)
- {
- utptr->ut_type = USER_PROCESS;
- strncpy(utptr->ut_user, username, sizeof(utptr->ut_user));
- utptr->ut_time = time(NULL);
- /* other fields already filled in by read_or_build_utent above */
- setutent();
- pututline(utptr);
- endutent();
- #if ENABLE_FEATURE_WTMP
- if (access(bb_path_wtmp_file, R_OK|W_OK) == -1) {
- close(creat(bb_path_wtmp_file, 0664));
- }
- updwtmp(bb_path_wtmp_file, utptr);
- #endif
- }
- #else /* !ENABLE_FEATURE_UTMP */
- #define read_or_build_utent(utptr, picky) ((void)0)
- #define write_utent(utptr, username) ((void)0)
- #endif /* !ENABLE_FEATURE_UTMP */
- #if ENABLE_FEATURE_NOLOGIN
- static void die_if_nologin(void)
- {
- FILE *fp;
- int c;
- if (access("/etc/nologin", F_OK))
- return;
- fp = fopen("/etc/nologin", "r");
- if (fp) {
- while ((c = getc(fp)) != EOF)
- bb_putchar((c=='\n') ? '\r' : c);
- fflush(stdout);
- fclose(fp);
- } else
- puts("\r\nSystem closed for routine maintenance\r");
- exit(1);
- }
- #else
- static ALWAYS_INLINE void die_if_nologin(void) {}
- #endif
- #if ENABLE_FEATURE_SECURETTY && !ENABLE_PAM
- static int check_securetty(void)
- {
- FILE *fp;
- int i;
- char buf[256];
- fp = fopen("/etc/securetty", "r");
- if (!fp) {
- /* A missing securetty file is not an error. */
- return 1;
- }
- while (fgets(buf, sizeof(buf)-1, fp)) {
- for (i = strlen(buf)-1; i >= 0; --i) {
- if (!isspace(buf[i]))
- break;
- }
- buf[++i] = '\0';
- if (!buf[0] || (buf[0] == '#'))
- continue;
- if (strcmp(buf, short_tty) == 0) {
- fclose(fp);
- return 1;
- }
- }
- fclose(fp);
- return 0;
- }
- #else
- static ALWAYS_INLINE int check_securetty(void) { return 1; }
- #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(1);
- if (c == '\n') {
- if (!--cntdown) exit(1);
- goto prompt;
- }
- } while (isspace(c));
- *buf++ = c;
- if (!fgets(buf, size_buf-2, stdin))
- exit(1);
- if (!strchr(buf, '\n'))
- exit(1);
- while (isgraph(*buf)) buf++;
- *buf = '\0';
- }
- static void motd(void)
- {
- int fd;
- fd = open(bb_path_motd_file, O_RDONLY);
- if (fd >= 0) {
- fflush(stdout);
- bb_copyfd_eof(fd, STDOUT_FILENO);
- close(fd);
- }
- }
- static void alarm_handler(int sig ATTRIBUTE_UNUSED)
- {
- /* 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(stdout);
- /* 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 ATTRIBUTE_UNUSED, 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 *tmp;
- int amroot;
- unsigned opt;
- int count = 0;
- struct passwd *pw;
- char *opt_host = opt_host; /* for compiler */
- char *opt_user = opt_user; /* for compiler */
- char full_tty[TTYNAME_SIZE];
- USE_SELINUX(security_context_t user_sid = NULL;)
- USE_FEATURE_UTMP(struct utmp utent;)
- #if ENABLE_PAM
- int pamret;
- pam_handle_t *pamh;
- const char *pamuser;
- const char *failed_msg;
- struct passwd pwdstruct;
- char pwdbuf[256];
- #endif
- short_tty = full_tty;
- username[0] = '\0';
- signal(SIGALRM, alarm_handler);
- alarm(TIMEOUT);
- /* More of suid paranoia if called by non-root */
- amroot = !sanitize_env_if_suid(); /* Clear dangerous stuff, set PATH */
- /* 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 (!amroot)
- 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(0) || !isatty(1) || !isatty(2))
- return EXIT_FAILURE; /* Must be a terminal */
- safe_strncpy(full_tty, "UNKNOWN", sizeof(full_tty));
- tmp = ttyname(0);
- if (tmp) {
- safe_strncpy(full_tty, tmp, sizeof(full_tty));
- if (strncmp(full_tty, "/dev/", 5) == 0)
- short_tty = full_tty + 5;
- }
- read_or_build_utent(&utent, !amroot);
- if (opt & LOGIN_OPT_h) {
- USE_FEATURE_UTMP(
- safe_strncpy(utent.ut_host, opt_host, sizeof(utent.ut_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_NOWAIT, 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:
- bb_error_msg("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';
- }
- alarm(0);
- if (!amroot)
- die_if_nologin();
- write_utent(&utent, username);
- #if ENABLE_SELINUX
- if (is_selinux_enabled()) {
- security_context_t old_tty_sid, new_tty_sid;
- if (get_default_context(username, NULL, &user_sid)) {
- bb_error_msg_and_die("cannot 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
- /* 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);
- /* We trust environment only if we run by root */
- if (ENABLE_LOGIN_SCRIPTS && amroot) {
- 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");
- }
- }
- change_identity(pw);
- tmp = pw->pw_shell;
- if (!tmp || !*tmp)
- tmp = DEFAULT_SHELL;
- /* setup_environment params: shell, clear_env, change_env, pw */
- setup_environment(tmp, !(opt & LOGIN_OPT_p), 1, pw);
- motd();
- if (pw->pw_uid == 0)
- syslog(LOG_INFO, "root login%s", fromhost);
- #if ENABLE_SELINUX
- /* well, a simple setexeccon() here would do the job as well,
- * but let's play the game for now */
- set_current_security_context(user_sid);
- #endif
- // 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 */
- 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 it leave SIGINT etc enabled or disabled? */
- signal(SIGINT, SIG_DFL);
- /* Exec login shell with no additional parameters */
- run_shell(tmp, 1, NULL, NULL);
- /* return EXIT_FAILURE; - not reached */
- }
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