/* SPDX-License-Identifier: LGPL-2.1-or-later */

#include <errno.h>

#include <fcntl.h>

#include <poll.h>

#include <stddef.h>

#include <stdio.h>

#include <stdlib.h>

#include <sys/time.h>

#include <sys/utsname.h>

#include <unistd.h>

#include <utmpx.h>

#include "alloc-util.h"

#include "fd-util.h"

#include "hostname-util.h"

#include "io-util.h"

#include "macro.h"

#include "memory-util.h"

#include "path-util.h"

#include "string-util.h"

#include "terminal-util.h"

#include "time-util.h"

#include "user-util.h"

#include "utmp-wtmp.h"

int utmp_get_runlevel(int *runlevel, int *previous) {

        _unused_ _cleanup_(utxent_cleanup) bool utmpx = false;

        struct utmpx *found, lookup = { .ut_type = RUN_LVL };

        const char *e;

        assert(runlevel);

        /* If these values are set in the environment this takes

         * precedence. Presumably, sysvinit does this to work around a

         * race condition that would otherwise exist where we'd always

         * go to disk and hence might read runlevel data that might be

         * very new and not apply to the current script being executed. */

        e = getenv("RUNLEVEL");

        if (!isempty(e)) {

                *runlevel = e[0];

                if (previous)

                        *previous = 0;

                return 0;

        }

        if (utmpxname(_PATH_UTMPX) < 0)

                return -errno;

        utmpx = utxent_start();

        found = getutxid(&lookup);

        if (!found)

                return -errno;

        *runlevel = found->ut_pid & 0xFF;

        if (previous)

                *previous = (found->ut_pid >> 8) & 0xFF;

        return 0;

}

static void init_timestamp(struct utmpx *store, usec_t t) {

        assert(store);

        if (t <= 0)

                t = now(CLOCK_REALTIME);

        store->ut_tv.tv_sec = t / USEC_PER_SEC;

        store->ut_tv.tv_usec = t % USEC_PER_SEC;

}

static void init_entry(struct utmpx *store, usec_t t) {

        struct utsname uts = {};

        assert(store);

        init_timestamp(store, t);

        if (uname(&uts) >= 0)

                strncpy(store->ut_host, uts.release, sizeof(store->ut_host));

        strncpy(store->ut_line, "~", sizeof(store->ut_line));  /* or ~~ ? */

        strncpy(store->ut_id, "~~", sizeof(store->ut_id));

}

static int write_entry_utmp(const struct utmpx *store) {

        _unused_ _cleanup_(utxent_cleanup) bool utmpx = false;

        assert(store);

        /* utmp is similar to wtmp, but there is only one entry for

         * each entry type resp. user; i.e. basically a key/value

         * table. */

        if (utmpxname(_PATH_UTMPX) < 0)

                return -errno;

        utmpx = utxent_start();

        if (pututxline(store))

                return 0;

        if (errno == ENOENT) {

                /* If utmp/wtmp have been disabled, that's a good thing, hence ignore the error. */

                log_debug_errno(errno, "Not writing utmp: %m");

                return 0;

        }

        return -errno;

}

static int write_entry_wtmp(const struct utmpx *store) {

        assert(store);

        /* wtmp is a simple append-only file where each entry is

         * simply appended to the end; i.e. basically a log. */

        errno = 0;

        updwtmpx(_PATH_WTMPX, store);

        if (errno == ENOENT) {

                /* If utmp/wtmp have been disabled, that's a good thing, hence ignore the error. */

                log_debug_errno(errno, "Not writing wtmp: %m");

                return 0;

        }

        if (errno == EROFS) {

                log_warning_errno(errno, "Failed to write wtmp record, ignoring: %m");

                return 0;

        }

        return -errno;

}

static int write_utmp_wtmp(const struct utmpx *store_utmp, const struct utmpx *store_wtmp) {

        int r, s;

        r = write_entry_utmp(store_utmp);

        s = write_entry_wtmp(store_wtmp);

        return r < 0 ? r : s;

}

static int write_entry_both(const struct utmpx *store) {

        return write_utmp_wtmp(store, store);

}

int utmp_put_shutdown(void) {

        struct utmpx store = {};

        init_entry(&store, 0);

        store.ut_type = RUN_LVL;

        strncpy(store.ut_user, "shutdown", sizeof(store.ut_user));

        return write_entry_both(&store);

}

int utmp_put_reboot(usec_t t) {

        struct utmpx store = {};

        init_entry(&store, t);

        store.ut_type = BOOT_TIME;

        strncpy(store.ut_user, "reboot", sizeof(store.ut_user));

        return write_entry_both(&store);

}

static void copy_suffix(char *buf, size_t buf_size, const char *src) {

        size_t l;

        l = strlen(src);

        if (l < buf_size)

                strncpy(buf, src, buf_size);

        else

                memcpy(buf, src + l - buf_size, buf_size);

}

int utmp_put_init_process(const char *id, pid_t pid, pid_t sid, const char *line, int ut_type, const char *user) {

        struct utmpx store = {

                .ut_type = INIT_PROCESS,

                .ut_pid = pid,

                .ut_session = sid,

        };

        int r;

        assert(id);

        init_timestamp(&store, 0);

        /* Copy the whole string if it fits, or just the suffix without the terminating NUL. */

        copy_suffix(store.ut_id, sizeof(store.ut_id), id);

        if (line)

                strncpy_exact(store.ut_line, line, sizeof(store.ut_line));

        r = write_entry_both(&store);

        if (r < 0)

                return r;

        if (IN_SET(ut_type, LOGIN_PROCESS, USER_PROCESS)) {

                store.ut_type = LOGIN_PROCESS;

                r = write_entry_both(&store);

                if (r < 0)

                        return r;

        }

        if (ut_type == USER_PROCESS) {

                store.ut_type = USER_PROCESS;

                strncpy(store.ut_user, user, sizeof(store.ut_user)-1);

                r = write_entry_both(&store);

                if (r < 0)

                        return r;

        }

        return 0;

}

int utmp_put_dead_process(const char *id, pid_t pid, int code, int status) {

        _unused_ _cleanup_(utxent_cleanup) bool utmpx = false;

        struct utmpx lookup = {

                .ut_type = INIT_PROCESS /* looks for DEAD_PROCESS, LOGIN_PROCESS, USER_PROCESS, too */

        }, store, store_wtmp, *found;

        assert(id);

        utmpx = utxent_start();

        /* Copy the whole string if it fits, or just the suffix without the terminating NUL. */

        copy_suffix(store.ut_id, sizeof(store.ut_id), id);

        found = getutxid(&lookup);

        if (!found)

                return 0;

        if (found->ut_pid != pid)

                return 0;

        memcpy(&store, found, sizeof(store));

        store.ut_type = DEAD_PROCESS;

        store.ut_exit.e_termination = code;

        store.ut_exit.e_exit = status;

        zero(store.ut_user);

        zero(store.ut_host);

        zero(store.ut_tv);

        memcpy(&store_wtmp, &store, sizeof(store_wtmp));

        /* wtmp wants the current time */

        init_timestamp(&store_wtmp, 0);

        return write_utmp_wtmp(&store, &store_wtmp);

}

int utmp_put_runlevel(int runlevel, int previous) {

        struct utmpx store = {};

        int r;

        assert(runlevel > 0);

        if (previous <= 0) {

                /* Find the old runlevel automatically */

                r = utmp_get_runlevel(&previous, NULL);

                if (r < 0) {

                        if (r != -ESRCH)

                                return r;

                        previous = 0;

                }

        }

        if (previous == runlevel)

                return 0;

        init_entry(&store, 0);

        store.ut_type = RUN_LVL;

        store.ut_pid = (runlevel & 0xFF) | ((previous & 0xFF) << 8);

        strncpy(store.ut_user, "runlevel", sizeof(store.ut_user));

        return write_entry_both(&store);

}

#define TIMEOUT_USEC (50 * USEC_PER_MSEC)

static int write_to_terminal(const char *tty, const char *message) {

        _cleanup_close_ int fd = -1;

        const char *p;

        size_t left;

        usec_t end;

        assert(tty);

        assert(message);

        fd = open(tty, O_WRONLY|O_NONBLOCK|O_NOCTTY|O_CLOEXEC);

        if (fd < 0 || !isatty(fd))

                return -errno;

        p = message;

        left = strlen(message);

        end = now(CLOCK_MONOTONIC) + TIMEOUT_USEC;

        while (left > 0) {

                ssize_t n;

                usec_t t;

                int k;

                t = now(CLOCK_MONOTONIC);

                if (t >= end)

                        return -ETIME;

                k = fd_wait_for_event(fd, POLLOUT, end - t);

                if (k < 0)

                        return k;

                if (k == 0)

                        return -ETIME;

                n = write(fd, p, left);

                if (n < 0) {

                        if (errno == EAGAIN)

                                continue;

                        return -errno;

                }

                assert((size_t) n <= left);

                p += n;

                left -= n;

        }

        return 0;

}

int utmp_wall(

        const char *message,

        const char *username,

        const char *origin_tty,

        bool (*match_tty)(const char *tty, void *userdata),

        void *userdata) {

        _unused_ _cleanup_(utxent_cleanup) bool utmpx = false;

        _cleanup_free_ char *text = NULL, *hn = NULL, *un = NULL, *stdin_tty = NULL;

        struct utmpx *u;

        int r;

        hn = gethostname_malloc();

        if (!hn)

                return -ENOMEM;

        if (!username) {

                un = getlogname_malloc();

                if (!un)

                        return -ENOMEM;

        }

        if (!origin_tty) {

                getttyname_harder(STDIN_FILENO, &stdin_tty);

                origin_tty = stdin_tty;

        }

        if (asprintf(&text,

                     "\a\r\n"

                     "Broadcast message from %s@%s%s%s (%s):\r\n\r\n"

                     "%s\r\n\r\n",

                     un ?: username, hn,

                     origin_tty ? " on " : "", strempty(origin_tty),

                     FORMAT_TIMESTAMP(now(CLOCK_REALTIME)),

                     message) < 0)

                return -ENOMEM;

        utmpx = utxent_start();

        r = 0;

        while ((u = getutxent())) {

                _cleanup_free_ char *buf = NULL;

                const char *path;

                int q;

                if (u->ut_type != USER_PROCESS || u->ut_user[0] == 0)

                        continue;

                /* this access is fine, because STRLEN("/dev/") << 32 (UT_LINESIZE) */

                if (path_startswith(u->ut_line, "/dev/"))

                        path = u->ut_line;

                else {

                        if (asprintf(&buf, "/dev/%.*s", (int) sizeof(u->ut_line), u->ut_line) < 0)

                                return -ENOMEM;

                        path = buf;

                }

                if (!match_tty || match_tty(path, userdata)) {

                        q = write_to_terminal(path, text);

                        if (q < 0)

                                r = q;

                }

        }

        return r;

}