| /* vi: set sw=4 ts=4: */ |
| /* |
| * Licensed under GPLv2 or later, see file LICENSE in this tarball for details. |
| */ |
| |
| #include "busybox.h" |
| #include <utmp.h> |
| #include <sys/resource.h> |
| #include <syslog.h> |
| |
| #ifdef CONFIG_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 */ |
| #include <errno.h> |
| #endif |
| |
| enum { |
| TIMEOUT = 60, |
| EMPTY_USERNAME_COUNT = 10, |
| USERNAME_SIZE = 32, |
| TTYNAME_SIZE = 32, |
| }; |
| |
| static char full_tty[TTYNAME_SIZE]; |
| static char* short_tty = full_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 struct utmp utent; |
| |
| static void read_or_build_utent(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) { |
| utent = *ut; |
| } else { |
| if (picky) |
| bb_error_msg_and_die("no utmp entry found"); |
| |
| memset(&utent, 0, sizeof(utent)); |
| utent.ut_type = LOGIN_PROCESS; |
| utent.ut_pid = pid; |
| strncpy(utent.ut_line, short_tty, sizeof(utent.ut_line)); |
| /* This one is only 4 chars wide. Try to fit something |
| * remotely meaningful by skipping "tty"... */ |
| strncpy(utent.ut_id, short_tty + 3, sizeof(utent.ut_id)); |
| strncpy(utent.ut_user, "LOGIN", sizeof(utent.ut_user)); |
| utent.ut_time = time(NULL); |
| } |
| if (!picky) /* root login */ |
| memset(utent.ut_host, 0, sizeof(utent.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(const char *username) |
| { |
| utent.ut_type = USER_PROCESS; |
| strncpy(utent.ut_user, username, sizeof(utent.ut_user)); |
| utent.ut_time = time(NULL); |
| /* other fields already filled in by read_or_build_utent above */ |
| setutent(); |
| pututline(&utent); |
| 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, &utent); |
| #endif |
| } |
| #else /* !ENABLE_FEATURE_UTMP */ |
| static inline void read_or_build_utent(int ATTRIBUTE_UNUSED picky) {} |
| static inline void write_utent(const char ATTRIBUTE_UNUSED *username) {} |
| #endif /* !ENABLE_FEATURE_UTMP */ |
| |
| static void die_if_nologin_and_non_root(int amroot) |
| { |
| FILE *fp; |
| int c; |
| |
| if (access(bb_path_nologin_file, F_OK)) |
| return; |
| |
| fp = fopen(bb_path_nologin_file, "r"); |
| if (fp) { |
| while ((c = getc(fp)) != EOF) |
| putchar((c=='\n') ? '\r' : c); |
| fflush(stdout); |
| fclose(fp); |
| } else |
| puts("\r\nSystem closed for routine maintenance\r"); |
| if (!amroot) |
| exit(1); |
| puts("\r\n[Disconnect bypassed -- root login allowed.]\r"); |
| } |
| |
| #if ENABLE_FEATURE_SECURETTY |
| static int check_securetty(void) |
| { |
| FILE *fp; |
| int i; |
| char buf[BUFSIZ]; |
| |
| fp = fopen(bb_path_securetty_file, "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]=='\0') || (buf[0]=='#')) |
| continue; |
| if (strcmp(buf, short_tty) == 0) { |
| fclose(fp); |
| return 1; |
| } |
| } |
| fclose(fp); |
| return 0; |
| } |
| #else |
| static 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: |
| /* skip whitespace */ |
| print_login_prompt(); |
| 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) |
| { |
| FILE *fp; |
| int c; |
| |
| fp = fopen(bb_path_motd_file, "r"); |
| if (fp) { |
| while ((c = getc(fp)) != EOF) |
| putchar(c); |
| fclose(fp); |
| } |
| } |
| |
| static void nonblock(int fd) |
| { |
| fcntl(fd, F_SETFL, O_NONBLOCK | fcntl(fd, F_GETFL)); |
| } |
| |
| 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 */ |
| nonblock(1); |
| nonblock(2); |
| bb_info_msg("\r\nLogin timed out after %d seconds\r", TIMEOUT); |
| exit(EXIT_SUCCESS); |
| } |
| |
| int login_main(int argc, char **argv); |
| int login_main(int argc, char **argv) |
| { |
| enum { |
| LOGIN_OPT_f = (1<<0), |
| LOGIN_OPT_h = (1<<1), |
| LOGIN_OPT_p = (1<<2), |
| }; |
| char fromhost[512]; |
| char username[USERNAME_SIZE]; |
| const char *tmp; |
| int amroot; |
| unsigned opt; |
| int count = 0; |
| struct passwd *pw; |
| char *opt_host = NULL; |
| char *opt_user = NULL; |
| USE_SELINUX(security_context_t user_sid = NULL;) |
| |
| username[0] = '\0'; |
| amroot = (getuid() == 0); |
| signal(SIGALRM, alarm_handler); |
| alarm(TIMEOUT); |
| |
| opt = getopt32(argc, 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)); |
| } |
| if (optind < argc) /* user from command line (getty) */ |
| safe_strncpy(username, argv[optind], 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(!amroot); |
| |
| if (opt_host) { |
| USE_FEATURE_UTMP( |
| safe_strncpy(utent.ut_host, opt_host, sizeof(utent.ut_host)); |
| ) |
| snprintf(fromhost, sizeof(fromhost)-1, " on '%.100s' from " |
| "'%.200s'", short_tty, opt_host); |
| } |
| else |
| snprintf(fromhost, sizeof(fromhost)-1, " on '%.100s'", short_tty); |
| |
| bb_setpgrp; |
| |
| openlog(applet_name, LOG_PID | LOG_CONS | LOG_NOWAIT, LOG_AUTH); |
| |
| while (1) { |
| if (!username[0]) |
| get_username_or_die(username, sizeof(username)); |
| |
| pw = getpwnam(username); |
| if (!pw) { |
| safe_strncpy(username, "UNKNOWN", sizeof(username)); |
| goto auth_failed; |
| } |
| |
| 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; |
| |
| /* authorization takes place here */ |
| if (correct_password(pw)) |
| break; |
| |
| auth_failed: |
| opt &= ~LOGIN_OPT_f; |
| bb_do_delay(FAIL_DELAY); |
| puts("Login incorrect"); |
| if (++count == 3) { |
| syslog(LOG_WARNING, "invalid password for '%s'%s", |
| username, fromhost); |
| return EXIT_FAILURE; |
| } |
| username[0] = '\0'; |
| } |
| |
| alarm(0); |
| die_if_nologin_and_non_root(pw->pw_uid == 0); |
| |
| write_utent(username); |
| |
| #ifdef CONFIG_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); |
| |
| /* TODO: be nommu-friendly, use spawn? */ |
| if (ENABLE_LOGIN_SCRIPTS) { |
| char *script = getenv("LOGIN_PRE_SUID_SCRIPT"); |
| if (script) { |
| char *t_argv[2] = { script, NULL }; |
| switch (fork()) { |
| case -1: break; |
| case 0: /* child */ |
| xchdir("/"); |
| setenv("LOGIN_TTY", full_tty, 1); |
| setenv("LOGIN_USER", pw->pw_name, 1); |
| setenv("LOGIN_UID", utoa(pw->pw_uid), 1); |
| setenv("LOGIN_GID", utoa(pw->pw_gid), 1); |
| setenv("LOGIN_SHELL", pw->pw_shell, 1); |
| execvp(script, t_argv); |
| exit(1); |
| default: /* parent */ |
| wait(NULL); |
| } |
| } |
| } |
| |
| change_identity(pw); |
| tmp = pw->pw_shell; |
| if (!tmp || !*tmp) |
| tmp = DEFAULT_SHELL; |
| setup_environment(tmp, 1, !(opt & LOGIN_OPT_p), pw); |
| |
| motd(); |
| |
| if (pw->pw_uid == 0) |
| syslog(LOG_INFO, "root login%s", fromhost); |
| #ifdef CONFIG_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... |
| |
| /* 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); |
| |
| run_shell(tmp, 1, 0, 0); /* exec the shell finally */ |
| |
| return EXIT_FAILURE; |
| } |