/*      $OpenBSD: failedlogin.c,v 1.19 2021/10/24 21:24:16 deraadt Exp $        */

/*
 * Copyright (c) 1996 Todd C. Miller <millert@openbsd.org>
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

/*
 * failedlogin.c
 *      Log to failedlogin file and read from it, reporting the number of
 *      failed logins since the last good login and when/from where
 *      the last failed login was.
 */

#include <sys/stat.h>
#include <sys/time.h>

#include <fcntl.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <utmp.h>

#include "pathnames.h"

struct badlogin {
        char    bl_line[UT_LINESIZE];   /* tty used */
        char    bl_name[UT_NAMESIZE];   /* remote username */
        char    bl_host[UT_HOSTSIZE];   /* remote host */
        time_t  bl_time;                /* time of the login attempt */
        size_t  count;                  /* number of bad logins */
};

void     log_failedlogin(uid_t, char *, char *, char *);
int      check_failedlogin(uid_t);

/*
 * Log a bad login to the failedlogin file.
 */
void
log_failedlogin(uid_t uid, char *host, char *name, char *tty)
{
        struct badlogin failedlogin;
        int fd;

        /* Add O_CREAT if you want to create failedlogin if it doesn't exist */
        if ((fd = open(_PATH_FAILEDLOGIN, O_RDWR)) >= 0) {
                (void)lseek(fd, (off_t)uid * sizeof(failedlogin), SEEK_SET);

                /* Read in last bad login so can get the count */
                if (read(fd, (char *)&failedlogin, sizeof(failedlogin)) !=
                        sizeof(failedlogin) || failedlogin.bl_time == 0)
                        memset((void *)&failedlogin, 0, sizeof(failedlogin));

                (void)lseek(fd, (off_t)uid * sizeof(failedlogin), SEEK_SET);
                /* Increment count of bad logins */
                ++failedlogin.count;
                (void)time(&failedlogin.bl_time);
                strncpy(failedlogin.bl_line, tty, sizeof(failedlogin.bl_line));
                if (host)
                        strncpy(failedlogin.bl_host, host, sizeof(failedlogin.bl_host));
                else
                        *failedlogin.bl_host = '\0';    /* NULL host field */
                if (name)
                        strncpy(failedlogin.bl_name, name, sizeof(failedlogin.bl_name));
                else
                        *failedlogin.bl_name = '\0';    /* NULL name field */
                (void)write(fd, (char *)&failedlogin, sizeof(failedlogin));
                (void)close(fd);
        }
}

/*
 * Check the failedlogin file and report about the number of unsuccessful
 * logins and info about the last one in lastlogin style.
 * NOTE: zeros the count field since this is assumed to be called after the
 * user has been validated.
 */
int
check_failedlogin(uid_t uid)
{
        struct badlogin failedlogin;
        int fd, was_bad = 0;

        (void)memset((void *)&failedlogin, 0, sizeof(failedlogin));

        if ((fd = open(_PATH_FAILEDLOGIN, O_RDWR)) >= 0) {
                (void)lseek(fd, (off_t)uid * sizeof(failedlogin), SEEK_SET);
                if (read(fd, (char *)&failedlogin, sizeof(failedlogin)) ==
                    sizeof(failedlogin) && failedlogin.count > 0 ) {
                        /* There was a bad login */
                        was_bad = 1;
                        if (failedlogin.count > 1)
                                (void)printf("There have been %lu unsuccessful "
                                    "login attempts to your account.\n",
                                    (u_long)failedlogin.count);
                        (void)printf("Last unsuccessful login: %.*s", 24-5,
                                (char *)ctime(&failedlogin.bl_time));
                        (void)printf(" on %.*s",
                            (int)sizeof(failedlogin.bl_line),
                            failedlogin.bl_line);
                        if (*failedlogin.bl_host != '\0') {
                                if (*failedlogin.bl_name != '\0')
                                        (void)printf(" from %.*s@%.*s",
                                            (int)sizeof(failedlogin.bl_name),
                                            failedlogin.bl_name,
                                            (int)sizeof(failedlogin.bl_host),
                                            failedlogin.bl_host);
                                else
                                        (void)printf(" from %.*s",
                                            (int)sizeof(failedlogin.bl_host),
                                            failedlogin.bl_host);
                        }
                        (void)putchar('\n');

                        /* Reset since this is a good login and write record */
                        failedlogin.count = 0;
                        (void)lseek(fd, (off_t)uid * sizeof(failedlogin),
                            SEEK_SET);
                        (void)write(fd, (char *)&failedlogin,
                            sizeof(failedlogin));
                }
                (void)close(fd);
        }
        return(was_bad);
}