mirror of
https://github.com/sheumann/hush.git
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470 lines
12 KiB
C
470 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 tarball for details.
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*/
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#include "libbb.h"
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#include <utmp.h>
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#include <sys/resource.h>
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#include <syslog.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_UTMP
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/* vv Taken from tinylogin utmp.c vv */
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/*
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* read_or_build_utent - see if utmp file is correct for this process
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*
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* System V is very picky about the contents of the utmp file
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* and requires that a slot for the current process exist.
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* The utmp file is scanned for an entry with the same process
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* ID. If no entry exists the process exits with a message.
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*
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* The "picky" flag is for network and other logins that may
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* use special flags. It allows the pid checks to be overridden.
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* This means that getty should never invoke login with any
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* command line flags.
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*/
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static void read_or_build_utent(struct utmp *utptr, int picky)
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{
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struct utmp *ut;
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pid_t pid = getpid();
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setutent();
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/* First, try to find a valid utmp entry for this process. */
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while ((ut = getutent()))
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if (ut->ut_pid == pid && ut->ut_line[0] && ut->ut_id[0] &&
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(ut->ut_type == LOGIN_PROCESS || ut->ut_type == USER_PROCESS))
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break;
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/* If there is one, just use it, otherwise create a new one. */
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if (ut) {
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*utptr = *ut;
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} else {
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if (picky)
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bb_error_msg_and_die("no utmp entry found");
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memset(utptr, 0, sizeof(*utptr));
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utptr->ut_type = LOGIN_PROCESS;
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utptr->ut_pid = pid;
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strncpy(utptr->ut_line, short_tty, sizeof(utptr->ut_line));
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/* This one is only 4 chars wide. Try to fit something
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* remotely meaningful by skipping "tty"... */
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strncpy(utptr->ut_id, short_tty + 3, sizeof(utptr->ut_id));
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strncpy(utptr->ut_user, "LOGIN", sizeof(utptr->ut_user));
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utptr->ut_time = time(NULL);
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}
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if (!picky) /* root login */
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memset(utptr->ut_host, 0, sizeof(utptr->ut_host));
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}
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/*
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* write_utent - put a USER_PROCESS entry in the utmp file
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*
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* write_utent changes the type of the current utmp entry to
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* USER_PROCESS. the wtmp file will be updated as well.
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*/
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static void write_utent(struct utmp *utptr, const char *username)
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{
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utptr->ut_type = USER_PROCESS;
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strncpy(utptr->ut_user, username, sizeof(utptr->ut_user));
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utptr->ut_time = time(NULL);
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/* other fields already filled in by read_or_build_utent above */
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setutent();
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pututline(utptr);
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endutent();
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#if ENABLE_FEATURE_WTMP
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if (access(bb_path_wtmp_file, R_OK|W_OK) == -1) {
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close(creat(bb_path_wtmp_file, 0664));
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}
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updwtmp(bb_path_wtmp_file, utptr);
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#endif
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}
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#else /* !ENABLE_FEATURE_UTMP */
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#define read_or_build_utent(utptr, picky) ((void)0)
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#define write_utent(utptr, username) ((void)0)
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#endif /* !ENABLE_FEATURE_UTMP */
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#if ENABLE_FEATURE_NOLOGIN
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static void die_if_nologin_and_non_root(int amroot)
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{
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FILE *fp;
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int c;
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if (access("/etc/nologin", F_OK))
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return;
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fp = fopen("/etc/nologin", "r");
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if (fp) {
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while ((c = getc(fp)) != EOF)
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putchar((c=='\n') ? '\r' : c);
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fflush(stdout);
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fclose(fp);
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} else
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puts("\r\nSystem closed for routine maintenance\r");
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if (!amroot)
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exit(1);
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puts("\r\n[Disconnect bypassed -- root login allowed]\r");
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}
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#else
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static ALWAYS_INLINE void die_if_nologin_and_non_root(int amroot) {}
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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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FILE *fp;
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int i;
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char buf[256];
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fp = fopen("/etc/securetty", "r");
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if (!fp) {
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/* A missing securetty file is not an error. */
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return 1;
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}
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while (fgets(buf, sizeof(buf)-1, fp)) {
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for (i = strlen(buf)-1; i >= 0; --i) {
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if (!isspace(buf[i]))
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break;
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}
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buf[++i] = '\0';
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if (!buf[0] || (buf[0] == '#'))
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continue;
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if (strcmp(buf, short_tty) == 0) {
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fclose(fp);
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return 1;
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}
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}
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fclose(fp);
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return 0;
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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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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) exit(1);
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if (c == '\n') {
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if (!--cntdown) exit(1);
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goto prompt;
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}
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} while (isspace(c));
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*buf++ = c;
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if (!fgets(buf, size_buf-2, stdin))
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exit(1);
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if (!strchr(buf, '\n'))
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exit(1);
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while (isgraph(*buf)) 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) {
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fflush(stdout);
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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 ATTRIBUTE_UNUSED)
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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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ndelay_on(2);
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printf("\r\nLogin timed out after %d seconds\r\n", TIMEOUT);
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exit(EXIT_SUCCESS);
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}
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int login_main(int argc, char **argv);
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int login_main(int argc, 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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const char *tmp;
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int amroot;
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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 = NULL;
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char full_tty[TTYNAME_SIZE];
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USE_SELINUX(security_context_t user_sid = NULL;)
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USE_FEATURE_UTMP(struct utmp utent;)
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USE_PAM(pam_handle_t *pamh;)
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USE_PAM(int pamret;)
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USE_PAM(const char *failed_msg;)
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short_tty = full_tty;
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username[0] = '\0';
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amroot = (getuid() == 0);
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signal(SIGALRM, alarm_handler);
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alarm(TIMEOUT);
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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 (!amroot)
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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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if (optind < argc) /* user from command line (getty) */
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safe_strncpy(username, argv[optind], sizeof(username));
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/* Let's find out and memorize our tty */
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if (!isatty(0) || !isatty(1) || !isatty(2))
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return EXIT_FAILURE; /* Must be a terminal */
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safe_strncpy(full_tty, "UNKNOWN", sizeof(full_tty));
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tmp = ttyname(0);
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if (tmp) {
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safe_strncpy(full_tty, tmp, sizeof(full_tty));
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if (strncmp(full_tty, "/dev/", 5) == 0)
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short_tty = full_tty + 5;
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}
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read_or_build_utent(&utent, !amroot);
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if (opt_host) {
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USE_FEATURE_UTMP(
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safe_strncpy(utent.ut_host, opt_host, sizeof(utent.ut_host));
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)
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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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/* 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_NOWAIT, LOG_AUTH);
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while (1) {
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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 = "pam_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 = "pam_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 = "pam_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 = "account setup";
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goto pam_auth_failed;
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}
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/* read user back */
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{
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const char *pamuser;
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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 = "pam_get_item(USER)";
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goto pam_auth_failed;
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}
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safe_strncpy(username, pamuser, sizeof(username));
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}
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/* If we get here, the user was authenticated, and is
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* granted access. */
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pw = getpwnam(username);
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if (pw)
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break;
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goto auth_failed;
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pam_auth_failed:
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bb_error_msg("%s failed: %s (%d)", failed_msg, 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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return EXIT_FAILURE;
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}
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username[0] = '\0';
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}
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alarm(0);
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die_if_nologin_and_non_root(pw->pw_uid == 0);
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write_utent(&utent, username);
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#if ENABLE_SELINUX
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if (is_selinux_enabled()) {
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security_context_t old_tty_sid, new_tty_sid;
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if (get_default_context(username, NULL, &user_sid)) {
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bb_error_msg_and_die("cannot get SID for %s",
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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",
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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",
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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",
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full_tty, new_tty_sid);
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}
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}
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#endif
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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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if (ENABLE_LOGIN_SCRIPTS) {
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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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xspawn(t_argv); /* NOMMU-friendly */
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/* All variables are unset by setup_environment */
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wait(NULL);
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}
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}
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change_identity(pw);
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tmp = pw->pw_shell;
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if (!tmp || !*tmp)
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tmp = DEFAULT_SHELL;
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setup_environment(tmp, 1, !(opt & LOGIN_OPT_p), pw);
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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_SELINUX
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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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set_current_security_context(user_sid);
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#endif
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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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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 it leave SIGINT etc enabled or disabled? */
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signal(SIGINT, SIG_DFL);
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run_shell(tmp, 1, 0, 0); /* exec the shell finally */
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return EXIT_FAILURE;
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}
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