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function old new delta setup_environment 191 205 +14 login_main 1002 987 -15 su_main 474 458 -16 ------------------------------------------------------------------------------ (add/remove: 0/0 grow/shrink: 1/2 up/down: 14/-31) Total: -17 bytes Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
445 lines
12 KiB
C
445 lines
12 KiB
C
/* vi: set sw=4 ts=4: */
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/*
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* Licensed under GPLv2 or later, see file LICENSE in this source tree.
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*/
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#include "libbb.h"
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#include <syslog.h>
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#include <sys/resource.h>
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#if ENABLE_SELINUX
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# include <selinux/selinux.h> /* for is_selinux_enabled() */
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# include <selinux/get_context_list.h> /* for get_default_context() */
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# include <selinux/flask.h> /* for security class definitions */
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#endif
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#if ENABLE_PAM
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/* PAM may include <locale.h>. We may need to undefine bbox's stub define: */
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# undef setlocale
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/* For some obscure reason, PAM is not in pam/xxx, but in security/xxx.
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* Apparently they like to confuse people. */
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# include <security/pam_appl.h>
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# include <security/pam_misc.h>
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static const struct pam_conv conv = {
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misc_conv,
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NULL
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};
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#endif
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enum {
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TIMEOUT = 60,
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EMPTY_USERNAME_COUNT = 10,
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USERNAME_SIZE = 32,
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TTYNAME_SIZE = 32,
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};
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static char* short_tty;
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#if ENABLE_FEATURE_NOLOGIN
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static void die_if_nologin(void)
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{
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FILE *fp;
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int c;
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int empty = 1;
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fp = fopen_for_read("/etc/nologin");
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if (!fp) /* assuming it does not exist */
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return;
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while ((c = getc(fp)) != EOF) {
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if (c == '\n')
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bb_putchar('\r');
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bb_putchar(c);
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empty = 0;
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}
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if (empty)
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puts("\r\nSystem closed for routine maintenance\r");
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fclose(fp);
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fflush_all();
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/* Users say that they do need this prior to exit: */
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tcdrain(STDOUT_FILENO);
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exit(EXIT_FAILURE);
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}
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#else
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# define die_if_nologin() ((void)0)
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#endif
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#if ENABLE_FEATURE_SECURETTY && !ENABLE_PAM
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static int check_securetty(void)
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{
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char *buf = (char*)"/etc/securetty"; /* any non-NULL is ok */
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parser_t *parser = config_open2("/etc/securetty", fopen_for_read);
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while (config_read(parser, &buf, 1, 1, "# \t", PARSE_NORMAL)) {
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if (strcmp(buf, short_tty) == 0)
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break;
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buf = NULL;
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}
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config_close(parser);
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/* buf != NULL here if config file was not found, empty
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* or line was found which equals short_tty */
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return buf != NULL;
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}
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#else
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static ALWAYS_INLINE int check_securetty(void) { return 1; }
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#endif
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#if ENABLE_SELINUX
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static void initselinux(char *username, char *full_tty,
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security_context_t *user_sid)
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{
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security_context_t old_tty_sid, new_tty_sid;
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if (!is_selinux_enabled())
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return;
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if (get_default_context(username, NULL, user_sid)) {
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bb_error_msg_and_die("can't get SID for %s", username);
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}
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if (getfilecon(full_tty, &old_tty_sid) < 0) {
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bb_perror_msg_and_die("getfilecon(%s) failed", full_tty);
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}
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if (security_compute_relabel(*user_sid, old_tty_sid,
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SECCLASS_CHR_FILE, &new_tty_sid) != 0) {
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bb_perror_msg_and_die("security_change_sid(%s) failed", full_tty);
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}
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if (setfilecon(full_tty, new_tty_sid) != 0) {
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bb_perror_msg_and_die("chsid(%s, %s) failed", full_tty, new_tty_sid);
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}
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}
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#endif
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#if ENABLE_LOGIN_SCRIPTS
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static void run_login_script(struct passwd *pw, char *full_tty)
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{
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char *t_argv[2];
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t_argv[0] = getenv("LOGIN_PRE_SUID_SCRIPT");
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if (t_argv[0]) {
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t_argv[1] = NULL;
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xsetenv("LOGIN_TTY", full_tty);
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xsetenv("LOGIN_USER", pw->pw_name);
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xsetenv("LOGIN_UID", utoa(pw->pw_uid));
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xsetenv("LOGIN_GID", utoa(pw->pw_gid));
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xsetenv("LOGIN_SHELL", pw->pw_shell);
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spawn_and_wait(t_argv); /* NOMMU-friendly */
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unsetenv("LOGIN_TTY");
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unsetenv("LOGIN_USER");
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unsetenv("LOGIN_UID");
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unsetenv("LOGIN_GID");
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unsetenv("LOGIN_SHELL");
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}
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}
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#else
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void run_login_script(struct passwd *pw, char *full_tty);
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#endif
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static void get_username_or_die(char *buf, int size_buf)
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{
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int c, cntdown;
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cntdown = EMPTY_USERNAME_COUNT;
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prompt:
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print_login_prompt();
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/* skip whitespace */
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do {
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c = getchar();
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if (c == EOF)
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exit(EXIT_FAILURE);
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if (c == '\n') {
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if (!--cntdown)
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exit(EXIT_FAILURE);
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goto prompt;
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}
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} while (isspace(c)); /* maybe isblank? */
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*buf++ = c;
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if (!fgets(buf, size_buf-2, stdin))
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exit(EXIT_FAILURE);
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if (!strchr(buf, '\n'))
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exit(EXIT_FAILURE);
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while ((unsigned char)*buf > ' ')
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buf++;
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*buf = '\0';
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}
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static void motd(void)
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{
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int fd;
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fd = open(bb_path_motd_file, O_RDONLY);
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if (fd >= 0) {
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fflush_all();
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bb_copyfd_eof(fd, STDOUT_FILENO);
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close(fd);
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}
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}
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static void alarm_handler(int sig UNUSED_PARAM)
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{
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/* This is the escape hatch! Poor serial line users and the like
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* arrive here when their connection is broken.
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* We don't want to block here */
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ndelay_on(1);
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printf("\r\nLogin timed out after %d seconds\r\n", TIMEOUT);
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fflush_all();
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/* unix API is brain damaged regarding O_NONBLOCK,
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* we should undo it, or else we can affect other processes */
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ndelay_off(1);
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_exit(EXIT_SUCCESS);
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}
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int login_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
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int login_main(int argc UNUSED_PARAM, char **argv)
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{
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enum {
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LOGIN_OPT_f = (1<<0),
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LOGIN_OPT_h = (1<<1),
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LOGIN_OPT_p = (1<<2),
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};
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char *fromhost;
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char username[USERNAME_SIZE];
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int run_by_root;
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unsigned opt;
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int count = 0;
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struct passwd *pw;
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char *opt_host = NULL;
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char *opt_user = opt_user; /* for compiler */
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char *full_tty;
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IF_SELINUX(security_context_t user_sid = NULL;)
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#if ENABLE_PAM
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int pamret;
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pam_handle_t *pamh;
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const char *pamuser;
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const char *failed_msg;
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struct passwd pwdstruct;
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char pwdbuf[256];
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char **pamenv;
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#endif
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username[0] = '\0';
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signal(SIGALRM, alarm_handler);
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alarm(TIMEOUT);
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/* More of suid paranoia if called by non-root: */
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/* Clear dangerous stuff, set PATH */
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run_by_root = !sanitize_env_if_suid();
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/* Mandatory paranoia for suid applet:
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* ensure that fd# 0,1,2 are opened (at least to /dev/null)
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* and any extra open fd's are closed.
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* (The name of the function is misleading. Not daemonizing here.) */
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bb_daemonize_or_rexec(DAEMON_ONLY_SANITIZE | DAEMON_CLOSE_EXTRA_FDS, NULL);
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opt = getopt32(argv, "f:h:p", &opt_user, &opt_host);
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if (opt & LOGIN_OPT_f) {
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if (!run_by_root)
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bb_error_msg_and_die("-f is for root only");
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safe_strncpy(username, opt_user, sizeof(username));
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}
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argv += optind;
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if (argv[0]) /* user from command line (getty) */
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safe_strncpy(username, argv[0], sizeof(username));
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/* Let's find out and memorize our tty */
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if (!isatty(STDIN_FILENO) || !isatty(STDOUT_FILENO) || !isatty(STDERR_FILENO))
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return EXIT_FAILURE; /* Must be a terminal */
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full_tty = xmalloc_ttyname(STDIN_FILENO);
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if (!full_tty)
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full_tty = xstrdup("UNKNOWN");
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short_tty = skip_dev_pfx(full_tty);
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if (opt_host) {
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fromhost = xasprintf(" on '%s' from '%s'", short_tty, opt_host);
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} else {
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fromhost = xasprintf(" on '%s'", short_tty);
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}
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/* Was breaking "login <username>" from shell command line: */
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/*bb_setpgrp();*/
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openlog(applet_name, LOG_PID | LOG_CONS, LOG_AUTH);
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while (1) {
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/* flush away any type-ahead (as getty does) */
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tcflush(0, TCIFLUSH);
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if (!username[0])
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get_username_or_die(username, sizeof(username));
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#if ENABLE_PAM
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pamret = pam_start("login", username, &conv, &pamh);
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if (pamret != PAM_SUCCESS) {
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failed_msg = "start";
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goto pam_auth_failed;
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}
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/* set TTY (so things like securetty work) */
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pamret = pam_set_item(pamh, PAM_TTY, short_tty);
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if (pamret != PAM_SUCCESS) {
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failed_msg = "set_item(TTY)";
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goto pam_auth_failed;
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}
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pamret = pam_authenticate(pamh, 0);
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if (pamret != PAM_SUCCESS) {
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failed_msg = "authenticate";
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goto pam_auth_failed;
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/* TODO: or just "goto auth_failed"
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* since user seems to enter wrong password
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* (in this case pamret == 7)
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*/
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}
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/* check that the account is healthy */
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pamret = pam_acct_mgmt(pamh, 0);
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if (pamret != PAM_SUCCESS) {
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failed_msg = "acct_mgmt";
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goto pam_auth_failed;
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}
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/* read user back */
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pamuser = NULL;
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/* gcc: "dereferencing type-punned pointer breaks aliasing rules..."
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* thus we cast to (void*) */
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if (pam_get_item(pamh, PAM_USER, (void*)&pamuser) != PAM_SUCCESS) {
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failed_msg = "get_item(USER)";
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goto pam_auth_failed;
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}
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if (!pamuser || !pamuser[0])
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goto auth_failed;
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safe_strncpy(username, pamuser, sizeof(username));
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/* Don't use "pw = getpwnam(username);",
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* PAM is said to be capable of destroying static storage
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* used by getpwnam(). We are using safe(r) function */
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pw = NULL;
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getpwnam_r(username, &pwdstruct, pwdbuf, sizeof(pwdbuf), &pw);
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if (!pw)
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goto auth_failed;
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pamret = pam_open_session(pamh, 0);
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if (pamret != PAM_SUCCESS) {
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failed_msg = "open_session";
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goto pam_auth_failed;
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}
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pamret = pam_setcred(pamh, PAM_ESTABLISH_CRED);
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if (pamret != PAM_SUCCESS) {
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failed_msg = "setcred";
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goto pam_auth_failed;
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}
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break; /* success, continue login process */
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pam_auth_failed:
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/* syslog, because we don't want potential attacker
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* to know _why_ login failed */
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syslog(LOG_WARNING, "pam_%s call failed: %s (%d)", failed_msg,
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pam_strerror(pamh, pamret), pamret);
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safe_strncpy(username, "UNKNOWN", sizeof(username));
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#else /* not PAM */
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pw = getpwnam(username);
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if (!pw) {
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strcpy(username, "UNKNOWN");
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goto fake_it;
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}
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if (pw->pw_passwd[0] == '!' || pw->pw_passwd[0] == '*')
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goto auth_failed;
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if (opt & LOGIN_OPT_f)
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break; /* -f USER: success without asking passwd */
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if (pw->pw_uid == 0 && !check_securetty())
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goto auth_failed;
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/* Don't check the password if password entry is empty (!) */
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if (!pw->pw_passwd[0])
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break;
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fake_it:
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/* authorization takes place here */
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if (correct_password(pw))
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break;
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#endif /* ENABLE_PAM */
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auth_failed:
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opt &= ~LOGIN_OPT_f;
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bb_do_delay(FAIL_DELAY);
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/* TODO: doesn't sound like correct English phrase to me */
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puts("Login incorrect");
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if (++count == 3) {
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syslog(LOG_WARNING, "invalid password for '%s'%s",
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username, fromhost);
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if (ENABLE_FEATURE_CLEAN_UP)
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free(fromhost);
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return EXIT_FAILURE;
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}
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username[0] = '\0';
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} /* while (1) */
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alarm(0);
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/* We can ignore /etc/nologin if we are logging in as root,
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* it doesn't matter whether we are run by root or not */
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if (pw->pw_uid != 0)
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die_if_nologin();
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IF_SELINUX(initselinux(username, full_tty, &user_sid));
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/* Try these, but don't complain if they fail.
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* _f_chown is safe wrt race t=ttyname(0);...;chown(t); */
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fchown(0, pw->pw_uid, pw->pw_gid);
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fchmod(0, 0600);
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update_utmp(getpid(), USER_PROCESS, short_tty, username, run_by_root ? opt_host : NULL);
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/* We trust environment only if we run by root */
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if (ENABLE_LOGIN_SCRIPTS && run_by_root)
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run_login_script(pw, full_tty);
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change_identity(pw);
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setup_environment(pw->pw_shell,
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(!(opt & LOGIN_OPT_p) * SETUP_ENV_CLEARENV) + SETUP_ENV_CHANGEENV,
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pw);
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#if ENABLE_PAM
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/* Modules such as pam_env will setup the PAM environment,
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* which should be copied into the new environment. */
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pamenv = pam_getenvlist(pamh);
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if (pamenv) while (*pamenv) {
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putenv(*pamenv);
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pamenv++;
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}
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#endif
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motd();
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if (pw->pw_uid == 0)
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syslog(LOG_INFO, "root login%s", fromhost);
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if (ENABLE_FEATURE_CLEAN_UP)
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free(fromhost);
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/* well, a simple setexeccon() here would do the job as well,
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* but let's play the game for now */
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IF_SELINUX(set_current_security_context(user_sid);)
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// util-linux login also does:
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// /* start new session */
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// setsid();
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// /* TIOCSCTTY: steal tty from other process group */
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// if (ioctl(0, TIOCSCTTY, 1)) error_msg...
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// BBox login used to do this (see above):
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// bb_setpgrp();
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// If this stuff is really needed, add it and explain why!
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/* Set signals to defaults */
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/* Non-ignored signals revert to SIG_DFL on exec anyway */
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/*signal(SIGALRM, SIG_DFL);*/
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/* Is this correct? This way user can ctrl-c out of /etc/profile,
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* potentially creating security breach (tested with bash 3.0).
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* But without this, bash 3.0 will not enable ctrl-c either.
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* Maybe bash is buggy?
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* Need to find out what standards say about /bin/login -
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* should we leave SIGINT etc enabled or disabled? */
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signal(SIGINT, SIG_DFL);
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/* Exec login shell with no additional parameters */
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run_shell(pw->pw_shell, 1, NULL, NULL);
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/* return EXIT_FAILURE; - not reached */
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}
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