source: MondoRescue/branches/3.3/mindi-busybox/libbb/utmp.c@ 3906

/* vi: set sw=4 ts=4: */
/*
 * utmp/wtmp support routines.
 *
 * Copyright (C) 2010 Denys Vlasenko
 *
 * Licensed under GPLv2, see file LICENSE in this source tree.
 */
#include "libbb.h"

static void touch(const char *filename)
{
    if (access(filename, R_OK | W_OK) == -1)
        close(open(filename, O_WRONLY | O_CREAT, 0664));
}

void FAST_FUNC write_new_utmp(pid_t pid, int new_type, const char *tty_name, const char *username, const char *hostname)
{
    struct utmpx utent;
    char *id;
    unsigned width;

    memset(&utent, 0, sizeof(utent));
    utent.ut_pid = pid;
    utent.ut_type = new_type;
    tty_name = skip_dev_pfx(tty_name);
    safe_strncpy(utent.ut_line, tty_name, sizeof(utent.ut_line));
    if (username)
        safe_strncpy(utent.ut_user, username, sizeof(utent.ut_user));
    if (hostname)
        safe_strncpy(utent.ut_host, hostname, sizeof(utent.ut_host));
    utent.ut_tv.tv_sec = time(NULL);

    /* Invent our own ut_id. ut_id is only 4 chars wide.
     * Try to fit something remotely meaningful... */
    id = utent.ut_id;
    width = sizeof(utent.ut_id);
    if (tty_name[0] == 'p') {
        /* if "ptyXXX", map to "pXXX" */
        /* if "pts/XX", map to "p/XX" */
        *id++ = 'p';
        width--;
    } /* else: usually it's "ttyXXXX", map to "XXXX" */
    if (strlen(tty_name) > 3)
        tty_name += 3;
    strncpy(id, tty_name, width);

    touch(_PATH_UTMPX);
    //utmpxname(_PATH_UTMPX);
    setutxent();
    /* Append new one (hopefully, unless we collide on ut_id) */
    pututxline(&utent);
    endutxent();

#if ENABLE_FEATURE_WTMP
    /* "man utmp" says wtmp file should *not* be created automagically */
    /*touch(bb_path_wtmp_file);*/
    updwtmpx(bb_path_wtmp_file, &utent);
#endif
}

/*
 * Read "man utmp" to make sense out of it.
 */
void FAST_FUNC update_utmp(pid_t pid, int new_type, const char *tty_name, const char *username, const char *hostname)
{
    struct utmpx utent;
    struct utmpx *utp;

    touch(_PATH_UTMPX);
    //utmpxname(_PATH_UTMPX);
    setutxent();

    /* Did init/getty/telnetd/sshd/... create an entry for us?
     * It should be (new_type-1), but we'd also reuse
     * any other potentially stale xxx_PROCESS entry */
    while ((utp = getutxent()) != NULL) {
        if (utp->ut_pid == pid
        // && ut->ut_line[0]
         && utp->ut_id[0] /* must have nonzero id */
         && (  utp->ut_type == INIT_PROCESS
            || utp->ut_type == LOGIN_PROCESS
            || utp->ut_type == USER_PROCESS
            || utp->ut_type == DEAD_PROCESS
            )
        ) {
            if (utp->ut_type >= new_type) {
                /* Stale record. Nuke hostname */
                memset(utp->ut_host, 0, sizeof(utp->ut_host));
            }
            /* NB: pututxline (see later) searches for matching utxent
             * using getutxid(utent) - we must not change ut_id
             * if we want *exactly this* record to be overwritten!
             */
            break;
        }
    }
    //endutxent(); - no need, pututxline can deal with (and actually likes)
    //the situation when utmp file is positioned on found record

    if (!utp) {
        if (new_type != DEAD_PROCESS)
            write_new_utmp(pid, new_type, tty_name, username, hostname);
        else
            endutxent();
        return;
    }

    /* Make a copy. We can't use *utp, pututxline's internal getutxid
     * will overwrite it before it is used! */
    utent = *utp;

    utent.ut_type = new_type;
    if (tty_name)
        safe_strncpy(utent.ut_line, skip_dev_pfx(tty_name), sizeof(utent.ut_line));
    if (username)
        safe_strncpy(utent.ut_user, username, sizeof(utent.ut_user));
    if (hostname)
        safe_strncpy(utent.ut_host, hostname, sizeof(utent.ut_host));
    utent.ut_tv.tv_sec = time(NULL);

    /* Update, or append new one */
    //setutxent();
    pututxline(&utent);
    endutxent();

#if ENABLE_FEATURE_WTMP
    /* "man utmp" says wtmp file should *not* be created automagically */
    /*touch(bb_path_wtmp_file);*/
    updwtmpx(bb_path_wtmp_file, &utent);
#endif
}

/* man utmp:
 * When init(8) finds that a process has exited, it locates its utmp entry
 * by ut_pid, sets ut_type to DEAD_PROCESS, and clears ut_user, ut_host
 * and ut_time with null bytes.
 * [same applies to other processes which maintain utmp entries, like telnetd]
 *
 * We do not bother actually clearing fields:
 * it might be interesting to know who was logged in and from where
 */
void FAST_FUNC update_utmp_DEAD_PROCESS(pid_t pid)
{
    update_utmp(pid, DEAD_PROCESS, NULL, NULL, NULL);
}