NetworkManager/src/core/nm-hostname-manager.c

/* SPDX-License-Identifier: GPL-2.0-or-later */
/*
 * Copyright (C) 2017 Red Hat, Inc.
 */

#include "src/core/nm-default-daemon.h"

#include "nm-hostname-manager.h"

#include <sys/stat.h>

#if HAVE_SELINUX
    #include <selinux/selinux.h>
    #include <selinux/label.h>
#endif

#include "nm-libnm-core-intern/nm-common-macros.h"
#include "nm-dbus-interface.h"
#include "nm-connection.h"
#include "nm-utils.h"
#include "nm-core-internal.h"

#include "NetworkManagerUtils.h"

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

#define HOSTNAMED_SERVICE_NAME      "org.freedesktop.hostname1"
#define HOSTNAMED_SERVICE_PATH      "/org/freedesktop/hostname1"
#define HOSTNAMED_SERVICE_INTERFACE "org.freedesktop.hostname1"

#define HOSTNAME_FILE_DEFAULT        "/etc/hostname"
#define HOSTNAME_FILE_UCASE_HOSTNAME "/etc/HOSTNAME"
#define HOSTNAME_FILE_GENTOO         "/etc/conf.d/hostname"

#define CONF_DHCP SYSCONFDIR "/sysconfig/network/dhcp"

#if (defined(HOSTNAME_PERSIST_SUSE) + defined(HOSTNAME_PERSIST_SLACKWARE) \
     + defined(HOSTNAME_PERSIST_GENTOO))                                  \
    > 1
    #error "Can only define one of HOSTNAME_PERSIST_*"
#endif

#if defined(HOSTNAME_PERSIST_SUSE)
    #define HOSTNAME_FILE HOSTNAME_FILE_UCASE_HOSTNAME
#elif defined(HOSTNAME_PERSIST_SLACKWARE)
    #define HOSTNAME_FILE HOSTNAME_FILE_UCASE_HOSTNAME
#elif defined(HOSTNAME_PERSIST_GENTOO)
    #define HOSTNAME_FILE HOSTNAME_FILE_GENTOO
#else
    #define HOSTNAME_FILE HOSTNAME_FILE_DEFAULT
#endif

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

NM_GOBJECT_PROPERTIES_DEFINE(NMHostnameManager, PROP_HOSTNAME, );

typedef struct {
    char *        current_hostname;
    GFileMonitor *monitor;
    GFileMonitor *dhcp_monitor;
    gulong        monitor_id;
    gulong        dhcp_monitor_id;
    GDBusProxy *  hostnamed_proxy;
} NMHostnameManagerPrivate;

struct _NMHostnameManager {
    GObject                  parent;
    NMHostnameManagerPrivate _priv;
};

struct _NMHostnameManagerClass {
    GObjectClass parent;
};

G_DEFINE_TYPE(NMHostnameManager, nm_hostname_manager, G_TYPE_OBJECT);

#define NM_HOSTNAME_MANAGER_GET_PRIVATE(self) \
    _NM_GET_PRIVATE(self, NMHostnameManager, NM_IS_HOSTNAME_MANAGER)

NM_DEFINE_SINGLETON_GETTER(NMHostnameManager, nm_hostname_manager_get, NM_TYPE_HOSTNAME_MANAGER);

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

#define _NMLOG_DOMAIN      LOGD_CORE
#define _NMLOG(level, ...) __NMLOG_DEFAULT(level, _NMLOG_DOMAIN, "hostname", __VA_ARGS__)

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

#if defined(HOSTNAME_PERSIST_GENTOO)
static char *
read_hostname_gentoo(const char *path)
{
    gs_free char *     contents  = NULL;
    gs_strfreev char **all_lines = NULL;
    const char *       tmp;
    guint              i;

    if (!g_file_get_contents(path, &contents, NULL, NULL))
        return NULL;

    all_lines = g_strsplit(contents, "\n", 0);
    for (i = 0; all_lines[i]; i++) {
        g_strstrip(all_lines[i]);
        if (all_lines[i][0] == '#' || all_lines[i][0] == '\0')
            continue;
        if (g_str_has_prefix(all_lines[i], "hostname=")) {
            tmp = &all_lines[i][NM_STRLEN("hostname=")];
            return g_shell_unquote(tmp, NULL);
        }
    }
    return NULL;
}
#endif

#if defined(HOSTNAME_PERSIST_SLACKWARE)
static char *
read_hostname_slackware(const char *path)
{
    gs_free char *     contents  = NULL;
    gs_strfreev char **all_lines = NULL;
    guint              i         = 0;

    if (!g_file_get_contents(path, &contents, NULL, NULL))
        return NULL;

    all_lines = g_strsplit(contents, "\n", 0);
    for (i = 0; all_lines[i]; i++) {
        g_strstrip(all_lines[i]);
        if (all_lines[i][0] == '#' || all_lines[i][0] == '\0')
            continue;
        return g_shell_unquote(&all_lines[i][0], NULL);
    }
    return NULL;
}
#endif

#if defined(HOSTNAME_PERSIST_SUSE)
static gboolean
hostname_is_dynamic(void)
{
    GIOChannel *channel;
    char *      str     = NULL;
    gboolean    dynamic = FALSE;

    channel = g_io_channel_new_file(CONF_DHCP, "r", NULL);
    if (!channel)
        return dynamic;

    while (g_io_channel_read_line(channel, &str, NULL, NULL, NULL) != G_IO_STATUS_EOF) {
        if (str) {
            g_strstrip(str);
            if (g_str_has_prefix(str, "DHCLIENT_SET_HOSTNAME="))
                dynamic = strcmp(&str[NM_STRLEN("DHCLIENT_SET_HOSTNAME=")], "\"yes\"") == 0;
            g_free(str);
        }
    }

    g_io_channel_shutdown(channel, FALSE, NULL);
    g_io_channel_unref(channel);

    return dynamic;
}
#endif

/* Returns an allocated string which the caller owns and must eventually free */
char *
nm_hostname_manager_read_hostname(NMHostnameManager *self)
{
    NMHostnameManagerPrivate *priv     = NM_HOSTNAME_MANAGER_GET_PRIVATE(self);
    char *                    hostname = NULL;

    if (priv->hostnamed_proxy) {
        hostname = g_strdup(priv->current_hostname);
        goto out;
    }

#if defined(HOSTNAME_PERSIST_SUSE)
    if (priv->dhcp_monitor_id && hostname_is_dynamic())
        return NULL;
#endif

#if defined(HOSTNAME_PERSIST_GENTOO)
    hostname = read_hostname_gentoo(HOSTNAME_FILE);
#elif defined(HOSTNAME_PERSIST_SLACKWARE)
    hostname = read_hostname_slackware(HOSTNAME_FILE);
#else
    if (g_file_get_contents(HOSTNAME_FILE, &hostname, NULL, NULL))
        g_strchomp(hostname);
#endif

out:
    if (hostname && !hostname[0]) {
        g_free(hostname);
        return NULL;
    }

    return hostname;
}

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

const char *
nm_hostname_manager_get_hostname(NMHostnameManager *self)
{
    g_return_val_if_fail(NM_IS_HOSTNAME_MANAGER(self), NULL);
    return NM_HOSTNAME_MANAGER_GET_PRIVATE(self)->current_hostname;
}

static void
_set_hostname_take(NMHostnameManager *self, char *hostname)
{
    NMHostnameManagerPrivate *priv = NM_HOSTNAME_MANAGER_GET_PRIVATE(self);

    _LOGI("hostname changed from %s%s%s to %s%s%s",
          NM_PRINT_FMT_QUOTED(priv->current_hostname, "\"", priv->current_hostname, "\"", "(none)"),
          NM_PRINT_FMT_QUOTED(hostname, "\"", hostname, "\"", "(none)"));

    g_free(priv->current_hostname);
    priv->current_hostname = hostname;
    _notify(self, PROP_HOSTNAME);
}

static void
_set_hostname(NMHostnameManager *self, const char *hostname)
{
    NMHostnameManagerPrivate *priv = NM_HOSTNAME_MANAGER_GET_PRIVATE(self);

    hostname = nm_str_not_empty(hostname);
    if (!nm_streq0(hostname, priv->current_hostname))
        _set_hostname_take(self, g_strdup(hostname));
}

static void
_set_hostname_read(NMHostnameManager *self)
{
    NMHostnameManagerPrivate *priv = NM_HOSTNAME_MANAGER_GET_PRIVATE(self);
    char *                    hostname;

    if (priv->hostnamed_proxy) {
        /* read-hostname returns the current hostname with hostnamed. */
        return;
    }

    hostname = nm_hostname_manager_read_hostname(self);

    if (nm_streq0(hostname, priv->current_hostname)) {
        g_free(hostname);
        return;
    }

    _set_hostname_take(self, hostname);
}

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

typedef struct {
    char *                         hostname;
    NMHostnameManagerSetHostnameCb cb;
    gpointer                       user_data;
} SetHostnameInfo;

static void
set_transient_hostname_done(GObject *object, GAsyncResult *res, gpointer user_data)
{
    GDBusProxy *proxy                 = G_DBUS_PROXY(object);
    gs_free SetHostnameInfo *info     = user_data;
    gs_unref_variant GVariant *result = NULL;
    gs_free_error GError *error       = NULL;

    result = g_dbus_proxy_call_finish(proxy, res, &error);

    if (error) {
        _LOGW("couldn't set the system hostname to '%s' using hostnamed: %s",
              info->hostname,
              error->message);
    }

    info->cb(info->hostname, !error, info->user_data);
    g_free(info->hostname);
}

void
nm_hostname_manager_set_transient_hostname(NMHostnameManager *            self,
                                           const char *                   hostname,
                                           NMHostnameManagerSetHostnameCb cb,
                                           gpointer                       user_data)
{
    NMHostnameManagerPrivate *priv;
    SetHostnameInfo *         info;

    g_return_if_fail(NM_IS_HOSTNAME_MANAGER(self));

    priv = NM_HOSTNAME_MANAGER_GET_PRIVATE(self);

    if (!priv->hostnamed_proxy) {
        cb(hostname, FALSE, user_data);
        return;
    }

    info            = g_new0(SetHostnameInfo, 1);
    info->hostname  = g_strdup(hostname);
    info->cb        = cb;
    info->user_data = user_data;

    g_dbus_proxy_call(priv->hostnamed_proxy,
                      "SetHostname",
                      g_variant_new("(sb)", hostname, FALSE),
                      G_DBUS_CALL_FLAGS_NONE,
                      -1,
                      NULL,
                      set_transient_hostname_done,
                      info);
}

gboolean
nm_hostname_manager_get_transient_hostname(NMHostnameManager *self, char **hostname)
{
    NMHostnameManagerPrivate *priv = NM_HOSTNAME_MANAGER_GET_PRIVATE(self);
    GVariant *                v_hostname;

    if (!priv->hostnamed_proxy)
        return FALSE;

    v_hostname = g_dbus_proxy_get_cached_property(priv->hostnamed_proxy, "Hostname");
    if (!v_hostname) {
        _LOGT("transient hostname retrieval failed");
        return FALSE;
    }

    *hostname = g_variant_dup_string(v_hostname, NULL);
    g_variant_unref(v_hostname);

    return TRUE;
}

gboolean
nm_hostname_manager_write_hostname(NMHostnameManager *self, const char *hostname)
{
    NMHostnameManagerPrivate *priv;
    char *                    hostname_eol;
    gboolean                  ret;
    gs_free_error GError *error     = NULL;
    const char *          file      = HOSTNAME_FILE;
    gs_free char *        link_path = NULL;
    gs_unref_variant GVariant *var  = NULL;
    struct stat                file_stat;
#if HAVE_SELINUX
    gboolean fcon_was_set = FALSE;
    char *   fcon_prev    = NULL;
#endif

    g_return_val_if_fail(NM_IS_HOSTNAME_MANAGER(self), FALSE);

    priv = NM_HOSTNAME_MANAGER_GET_PRIVATE(self);

    if (priv->hostnamed_proxy) {
        var = g_dbus_proxy_call_sync(priv->hostnamed_proxy,
                                     "SetStaticHostname",
                                     g_variant_new("(sb)", hostname, FALSE),
                                     G_DBUS_CALL_FLAGS_NONE,
                                     -1,
                                     NULL,
                                     &error);
        if (error)
            _LOGW("could not set hostname: %s", error->message);

        return !error;
    }

    /* If the hostname file is a symbolic link, follow it to find where the
     * real file is located, otherwise g_file_set_contents will attempt to
     * replace the link with a plain file.
     */
    if (lstat(file, &file_stat) == 0 && S_ISLNK(file_stat.st_mode)
        && (link_path = nm_utils_read_link_absolute(file, NULL)))
        file = link_path;

#if defined(HOSTNAME_PERSIST_GENTOO)
    hostname_eol = g_strdup_printf("#Generated by NetworkManager\n"
                                   "hostname=\"%s\"\n",
                                   hostname);
#else
    hostname_eol = g_strdup_printf("%s\n", hostname);
#endif

#if HAVE_SELINUX
    /* Get default context for hostname file and set it for fscreate */
    {
        struct selabel_handle *handle;

        handle = selabel_open(SELABEL_CTX_FILE, NULL, 0);
        if (handle) {
            mode_t st_mode = 0;
            char * fcon    = NULL;

            if (stat(file, &file_stat) == 0)
                st_mode = file_stat.st_mode;

            if ((selabel_lookup(handle, &fcon, file, st_mode) == 0)
                && (getfscreatecon(&fcon_prev) == 0)) {
                setfscreatecon(fcon);
                fcon_was_set = TRUE;
            }

            selabel_close(handle);
            freecon(fcon);
        }
    }
#endif

    ret = g_file_set_contents(file, hostname_eol, -1, &error);

#if HAVE_SELINUX
    /* Restore previous context and cleanup */
    if (fcon_was_set)
        setfscreatecon(fcon_prev);
    if (fcon_prev)
        freecon(fcon_prev);
#endif

    g_free(hostname_eol);

    if (!ret) {
        _LOGW("could not save hostname to %s: %s", file, error->message);
        return FALSE;
    }

    return TRUE;
}

gboolean
nm_hostname_manager_validate_hostname(const char *hostname)
{
    const char *p;
    gboolean    dot = TRUE;

    if (!hostname || !hostname[0])
        return FALSE;

    for (p = hostname; *p; p++) {
        if (*p == '.') {
            if (dot)
                return FALSE;
            dot = TRUE;
        } else {
            if (!g_ascii_isalnum(*p) && (*p != '-') && (*p != '_'))
                return FALSE;
            dot = FALSE;
        }
    }

    if (dot)
        return FALSE;

    return (p - hostname <= HOST_NAME_MAX);
}

static void
hostname_file_changed_cb(GFileMonitor *    monitor,
                         GFile *           file,
                         GFile *           other_file,
                         GFileMonitorEvent event_type,
                         gpointer          user_data)
{
    _set_hostname_read(user_data);
}

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

static void
hostnamed_properties_changed(GDBusProxy *proxy,
                             GVariant *  changed_properties,
                             char **     invalidated_properties,
                             gpointer    user_data)
{
    NMHostnameManager *       self = user_data;
    NMHostnameManagerPrivate *priv = NM_HOSTNAME_MANAGER_GET_PRIVATE(self);
    GVariant *                v_hostname;

    v_hostname = g_dbus_proxy_get_cached_property(priv->hostnamed_proxy, "StaticHostname");
    if (v_hostname) {
        _set_hostname(self, g_variant_get_string(v_hostname, NULL));
        g_variant_unref(v_hostname);
    }
}

static void
setup_hostname_file_monitors(NMHostnameManager *self)
{
    NMHostnameManagerPrivate *priv = NM_HOSTNAME_MANAGER_GET_PRIVATE(self);
    GFileMonitor *            monitor;
    const char *              path      = HOSTNAME_FILE;
    char *                    link_path = NULL;
    struct stat               file_stat;
    GFile *                   file;

    /* resolve the path to the hostname file if it is a symbolic link */
    if (lstat(path, &file_stat) == 0 && S_ISLNK(file_stat.st_mode)
        && (link_path = nm_utils_read_link_absolute(path, NULL))) {
        path = link_path;
        if (lstat(link_path, &file_stat) == 0 && S_ISLNK(file_stat.st_mode)) {
            _LOGW("only one level of symbolic link indirection is allowed when "
                  "monitoring " HOSTNAME_FILE);
        }
    }

    /* monitor changes to hostname file */
    file    = g_file_new_for_path(path);
    monitor = g_file_monitor_file(file, G_FILE_MONITOR_NONE, NULL, NULL);
    g_object_unref(file);
    g_free(link_path);
    if (monitor) {
        priv->monitor_id =
            g_signal_connect(monitor, "changed", G_CALLBACK(hostname_file_changed_cb), self);
        priv->monitor = monitor;
    }

#if defined(HOSTNAME_PERSIST_SUSE)
    /* monitor changes to dhcp file to know whether the hostname is valid */
    file    = g_file_new_for_path(CONF_DHCP);
    monitor = g_file_monitor_file(file, G_FILE_MONITOR_NONE, NULL, NULL);
    g_object_unref(file);
    if (monitor) {
        priv->dhcp_monitor_id =
            g_signal_connect(monitor, "changed", G_CALLBACK(hostname_file_changed_cb), self);
        priv->dhcp_monitor = monitor;
    }
#endif

    _set_hostname_read(self);
}

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

static void
get_property(GObject *object, guint prop_id, GValue *value, GParamSpec *pspec)
{
    NMHostnameManager *self = NM_HOSTNAME_MANAGER(object);

    switch (prop_id) {
    case PROP_HOSTNAME:
        g_value_set_string(value, nm_hostname_manager_get_hostname(self));
        break;
    default:
        G_OBJECT_WARN_INVALID_PROPERTY_ID(object, prop_id, pspec);
        break;
    }
}

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

static void
nm_hostname_manager_init(NMHostnameManager *self)
{}

static void
constructed(GObject *object)
{
    NMHostnameManager *       self = NM_HOSTNAME_MANAGER(object);
    NMHostnameManagerPrivate *priv = NM_HOSTNAME_MANAGER_GET_PRIVATE(self);
    GDBusProxy *              proxy;
    GVariant *                variant;
    gs_free_error GError *error = NULL;

    proxy = g_dbus_proxy_new_for_bus_sync(G_BUS_TYPE_SYSTEM,
                                          0,
                                          NULL,
                                          HOSTNAMED_SERVICE_NAME,
                                          HOSTNAMED_SERVICE_PATH,
                                          HOSTNAMED_SERVICE_INTERFACE,
                                          NULL,
                                          &error);
    if (proxy) {
        variant = g_dbus_proxy_get_cached_property(proxy, "StaticHostname");
        if (variant) {
            _LOGI("hostname: using hostnamed");
            priv->hostnamed_proxy = proxy;
            g_signal_connect(proxy,
                             "g-properties-changed",
                             G_CALLBACK(hostnamed_properties_changed),
                             self);
            hostnamed_properties_changed(proxy, NULL, NULL, self);
            g_variant_unref(variant);
        } else {
            _LOGI("hostname: couldn't get property from hostnamed");
            g_object_unref(proxy);
        }
    } else {
        _LOGI("hostname: hostnamed not used as proxy creation failed with: %s", error->message);
        g_clear_error(&error);
    }

    if (!priv->hostnamed_proxy)
        setup_hostname_file_monitors(self);

    G_OBJECT_CLASS(nm_hostname_manager_parent_class)->constructed(object);
}

static void
dispose(GObject *object)
{
    NMHostnameManager *       self = NM_HOSTNAME_MANAGER(object);
    NMHostnameManagerPrivate *priv = NM_HOSTNAME_MANAGER_GET_PRIVATE(self);

    if (priv->hostnamed_proxy) {
        g_signal_handlers_disconnect_by_func(priv->hostnamed_proxy,
                                             G_CALLBACK(hostnamed_properties_changed),
                                             self);
        g_clear_object(&priv->hostnamed_proxy);
    }

    if (priv->monitor) {
        if (priv->monitor_id)
            g_signal_handler_disconnect(priv->monitor, priv->monitor_id);

        g_file_monitor_cancel(priv->monitor);
        g_clear_object(&priv->monitor);
    }

    if (priv->dhcp_monitor) {
        if (priv->dhcp_monitor_id)
            g_signal_handler_disconnect(priv->dhcp_monitor, priv->dhcp_monitor_id);

        g_file_monitor_cancel(priv->dhcp_monitor);
        g_clear_object(&priv->dhcp_monitor);
    }

    nm_clear_g_free(&priv->current_hostname);

    G_OBJECT_CLASS(nm_hostname_manager_parent_class)->dispose(object);
}

static void
nm_hostname_manager_class_init(NMHostnameManagerClass *class)
{
    GObjectClass *object_class = G_OBJECT_CLASS(class);

    object_class->constructed  = constructed;
    object_class->get_property = get_property;
    object_class->dispose      = dispose;

    obj_properties[PROP_HOSTNAME] = g_param_spec_string(NM_HOSTNAME_MANAGER_HOSTNAME,
                                                        "",
                                                        "",
                                                        NULL,
                                                        G_PARAM_READABLE | G_PARAM_STATIC_STRINGS);

    g_object_class_install_properties(object_class, _PROPERTY_ENUMS_LAST, obj_properties);
}