/* SPDX-License-Identifier: GPL-2.0-or-later */
/*
 * Copyright (C) 2008 - 2015 Red Hat, Inc.
 * Author: David Zeuthen <davidz@redhat.com>
 * Author: Dan Williams <dcbw@redhat.com>
 * Author: Matthias Clasen
 * Author: Pavel Šimerda <psimerda@redhat.com>
 */
#include "nm-default.h"

#include "nm-session-monitor.h"

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

#if SESSION_TRACKING_SYSTEMD && SESSION_TRACKING_ELOGIND
    #error Cannot build both systemd-logind and elogind support
#endif

#if SESSION_TRACKING_SYSTEMD
    #include <systemd/sd-login.h>
    #define LOGIND_NAME "systemd-logind"
#endif

#if SESSION_TRACKING_ELOGIND
    #include <elogind/sd-login.h>
    #define LOGIND_NAME "elogind"
#endif

#include "NetworkManagerUtils.h"

#define SESSION_TRACKING_XLOGIND (SESSION_TRACKING_SYSTEMD || SESSION_TRACKING_ELOGIND)

#define CKDB_PATH "/run/ConsoleKit/database"

/*****************************************************************************/

enum {
    CHANGED,
    LAST_SIGNAL,
};

static guint signals[LAST_SIGNAL] = {0};

struct _NMSessionMonitor {
    GObject parent;

#if SESSION_TRACKING_XLOGIND
    struct {
        sd_login_monitor *monitor;
        GSource *         watch;
    } sd;
#endif

#if SESSION_TRACKING_CONSOLEKIT
    struct {
        GFileMonitor *monitor;
        GHashTable *  cache;
        time_t        timestamp;
    } ck;
#endif
};

struct _NMSessionMonitorClass {
    GObjectClass parent;
};

G_DEFINE_TYPE(NMSessionMonitor, nm_session_monitor, G_TYPE_OBJECT);

#define _NMLOG_DOMAIN      LOGD_CORE
#define _NMLOG(level, ...) __NMLOG_DEFAULT(level, _NMLOG_DOMAIN, "session-monitor", __VA_ARGS__)

/*****************************************************************************/

#if SESSION_TRACKING_XLOGIND
static gboolean
st_sd_session_exists(NMSessionMonitor *monitor, uid_t uid, gboolean active)
{
    int status;

    if (!monitor->sd.monitor)
        return FALSE;

    status = sd_uid_get_sessions(uid, active, NULL);

    if (status < 0)
        _LOGE("failed to get " LOGIND_NAME " sessions for uid %d: %d", uid, status);

    return status > 0;
}

static gboolean
st_sd_changed(int fd, GIOCondition condition, gpointer user_data)
{
    NMSessionMonitor *monitor = user_data;

    g_signal_emit(monitor, signals[CHANGED], 0);

    sd_login_monitor_flush(monitor->sd.monitor);

    return G_SOURCE_CONTINUE;
}

static void
st_sd_init(NMSessionMonitor *monitor)
{
    int status;

    if (!g_file_test("/run/systemd/seats/", G_FILE_TEST_EXISTS))
        return;

    if ((status = sd_login_monitor_new(NULL, &monitor->sd.monitor)) < 0) {
        _LOGE("failed to create " LOGIND_NAME " monitor: %d", status);
        return;
    }

    monitor->sd.watch = nm_g_unix_fd_source_new(sd_login_monitor_get_fd(monitor->sd.monitor),
                                                G_IO_IN,
                                                G_PRIORITY_DEFAULT,
                                                st_sd_changed,
                                                monitor,
                                                NULL);
    g_source_attach(monitor->sd.watch, NULL);
}

static void
st_sd_finalize(NMSessionMonitor *monitor)
{
    if (monitor->sd.monitor) {
        sd_login_monitor_unref(monitor->sd.monitor);
        monitor->sd.monitor = NULL;
    }
    nm_clear_g_source_inst(&monitor->sd.watch);
}
#endif /* SESSION_TRACKING_XLOGIND */

/*****************************************************************************/

#if SESSION_TRACKING_CONSOLEKIT
typedef struct {
    gboolean active;
} CkSession;

static gboolean
ck_load_cache(GHashTable *cache)
{
    GKeyFile *keyfile = g_key_file_new();
    char **   groups  = NULL;
    GError *  error   = NULL;
    gsize     i, len;
    gboolean  finished = FALSE;

    if (!g_key_file_load_from_file(keyfile, CKDB_PATH, G_KEY_FILE_NONE, &error))
        goto out;

    if (!(groups = g_key_file_get_groups(keyfile, &len))) {
        _LOGE("could not load groups from " CKDB_PATH);
        goto out;
    }

    g_hash_table_remove_all(cache);

    for (i = 0; i < len; i++) {
        guint     uid     = G_MAXUINT;
        CkSession session = {.active = FALSE};

        if (!g_str_has_prefix(groups[i], "Session "))
            continue;

        uid = g_key_file_get_integer(keyfile, groups[i], "uid", &error);
        if (error)
            goto out;

        session.active = g_key_file_get_boolean(keyfile, groups[i], "is_active", &error);
        if (error)
            goto out;

        g_hash_table_insert(cache, GUINT_TO_POINTER(uid), nm_memdup(&session, sizeof session));
    }

    finished = TRUE;
out:
    if (error)
        _LOGE("failed to load ConsoleKit database: %s", error->message);
    g_clear_error(&error);
    nm_clear_pointer(&groups, g_strfreev);
    nm_clear_pointer(&keyfile, g_key_file_free);

    return finished;
}

static gboolean
ck_update_cache(NMSessionMonitor *monitor)
{
    struct stat statbuf;
    int         errsv;

    if (!monitor->ck.cache)
        return FALSE;

    /* Check the database file */
    if (stat(CKDB_PATH, &statbuf) != 0) {
        errsv = errno;
        _LOGE("failed to check ConsoleKit timestamp: %s", nm_strerror_native(errsv));
        return FALSE;
    }
    if (statbuf.st_mtime == monitor->ck.timestamp)
        return TRUE;

    /* Update the cache */
    if (!ck_load_cache(monitor->ck.cache))
        return FALSE;

    monitor->ck.timestamp = statbuf.st_mtime;

    return TRUE;
}

static gboolean
ck_session_exists(NMSessionMonitor *monitor, uid_t uid, gboolean active)
{
    CkSession *session;

    if (!ck_update_cache(monitor))
        return FALSE;

    session = g_hash_table_lookup(monitor->ck.cache, GUINT_TO_POINTER(uid));

    if (!session)
        return FALSE;
    if (active && !session->active)
        return FALSE;

    return TRUE;
}

static void
ck_changed(GFileMonitor *    file_monitor,
           GFile *           file,
           GFile *           other_file,
           GFileMonitorEvent event_type,
           gpointer          user_data)
{
    g_signal_emit(user_data, signals[CHANGED], 0);
}

static void
ck_init(NMSessionMonitor *monitor)
{
    GFile * file  = g_file_new_for_path(CKDB_PATH);
    GError *error = NULL;

    if (g_file_query_exists(file, NULL)) {
        if ((monitor->ck.monitor = g_file_monitor_file(file, G_FILE_MONITOR_NONE, NULL, &error))) {
            monitor->ck.cache = g_hash_table_new_full(nm_direct_hash, NULL, NULL, g_free);
            g_signal_connect(monitor->ck.monitor, "changed", G_CALLBACK(ck_changed), monitor);
        } else {
            _LOGE("error monitoring " CKDB_PATH ": %s", error->message);
            g_clear_error(&error);
        }
    }

    g_object_unref(file);
}

static void
ck_finalize(NMSessionMonitor *monitor)
{
    nm_clear_pointer(&monitor->ck.cache, g_hash_table_unref);
    g_clear_object(&monitor->ck.monitor);
}
#endif /* SESSION_TRACKING_CONSOLEKIT */

/*****************************************************************************/

NM_DEFINE_SINGLETON_GETTER(NMSessionMonitor, nm_session_monitor_get, NM_TYPE_SESSION_MONITOR);

/**
 * nm_session_monitor_session_exists:
 * @self: the session monitor
 * @uid: A user ID.
 * @active: Ignore inactive sessions.
 *
 * Checks whether the given @uid is logged into an active session. Don't
 * use this feature for security purposes. It is there just to allow you
 * to prefer an agent from an active session over an agent from an
 * inactive one.
 *
 * Returns: %FALSE if @error is set otherwise %TRUE if the given @uid is
 * logged into an active session.
 */
gboolean
nm_session_monitor_session_exists(NMSessionMonitor *self, uid_t uid, gboolean active)
{
    g_return_val_if_fail(NM_IS_SESSION_MONITOR(self), FALSE);

#if SESSION_TRACKING_XLOGIND
    if (st_sd_session_exists(self, uid, active))
        return TRUE;
#endif

#if SESSION_TRACKING_CONSOLEKIT
    if (ck_session_exists(self, uid, active))
        return TRUE;
#endif

    return FALSE;
}

/*****************************************************************************/

static void
nm_session_monitor_init(NMSessionMonitor *monitor)
{
#if SESSION_TRACKING_XLOGIND
    st_sd_init(monitor);
    _LOGD("using " LOGIND_NAME " session tracking");
#endif

#if SESSION_TRACKING_CONSOLEKIT
    ck_init(monitor);
    _LOGD("using ConsoleKit session tracking");
#endif
}

static void
finalize(GObject *object)
{
#if SESSION_TRACKING_XLOGIND
    st_sd_finalize(NM_SESSION_MONITOR(object));
#endif

#if SESSION_TRACKING_CONSOLEKIT
    ck_finalize(NM_SESSION_MONITOR(object));
#endif

    G_OBJECT_CLASS(nm_session_monitor_parent_class)->finalize(object);
}

static void
nm_session_monitor_class_init(NMSessionMonitorClass *klass)
{
    GObjectClass *gobject_class = G_OBJECT_CLASS(klass);

    gobject_class->finalize = finalize;

    /**
     * NMSessionMonitor::changed:
     * @monitor: A #NMSessionMonitor
     *
     * Emitted when something changes.
     */
    signals[CHANGED] = g_signal_new(NM_SESSION_MONITOR_CHANGED,
                                    NM_TYPE_SESSION_MONITOR,
                                    G_SIGNAL_RUN_LAST,
                                    0,
                                    NULL,
                                    NULL,
                                    g_cclosure_marshal_VOID__VOID,
                                    G_TYPE_NONE,
                                    0);
}