9pfs: local: forbid client access to metadata (CVE-2017-7493)

[mirror_qemu.git] / blockdev-nbd.c

/*
 * Serving QEMU block devices via NBD
 *
 * Copyright (c) 2012 Red Hat, Inc.
 *
 * Author: Paolo Bonzini <pbonzini@redhat.com>
 *
 * This work is licensed under the terms of the GNU GPL, version 2 or
 * later.  See the COPYING file in the top-level directory.
 */

#include "qemu/osdep.h"
#include "sysemu/blockdev.h"
#include "sysemu/block-backend.h"
#include "hw/block/block.h"
#include "qapi/qmp/qerror.h"
#include "sysemu/sysemu.h"
#include "qmp-commands.h"
#include "block/nbd.h"
#include "io/channel-socket.h"

typedef struct NBDServerData {
    QIOChannelSocket *listen_ioc;
    int watch;
    QCryptoTLSCreds *tlscreds;
} NBDServerData;

static NBDServerData *nbd_server;

static void nbd_blockdev_client_closed(NBDClient *client, bool ignored)
{
    nbd_client_put(client);
}

static gboolean nbd_accept(QIOChannel *ioc, GIOCondition condition,
                           gpointer opaque)
{
    QIOChannelSocket *cioc;

    if (!nbd_server) {
        return FALSE;
    }

    cioc = qio_channel_socket_accept(QIO_CHANNEL_SOCKET(ioc),
                                     NULL);
    if (!cioc) {
        return TRUE;
    }

    qio_channel_set_name(QIO_CHANNEL(cioc), "nbd-server");
    nbd_client_new(NULL, cioc,
                   nbd_server->tlscreds, NULL,
                   nbd_blockdev_client_closed);
    object_unref(OBJECT(cioc));
    return TRUE;
}


static void nbd_server_free(NBDServerData *server)
{
    if (!server) {
        return;
    }

    if (server->watch != -1) {
        g_source_remove(server->watch);
    }
    object_unref(OBJECT(server->listen_ioc));
    if (server->tlscreds) {
        object_unref(OBJECT(server->tlscreds));
    }

    g_free(server);
}

static QCryptoTLSCreds *nbd_get_tls_creds(const char *id, Error **errp)
{
    Object *obj;
    QCryptoTLSCreds *creds;

    obj = object_resolve_path_component(
        object_get_objects_root(), id);
    if (!obj) {
        error_setg(errp, "No TLS credentials with id '%s'",
                   id);
        return NULL;
    }
    creds = (QCryptoTLSCreds *)
        object_dynamic_cast(obj, TYPE_QCRYPTO_TLS_CREDS);
    if (!creds) {
        error_setg(errp, "Object with id '%s' is not TLS credentials",
                   id);
        return NULL;
    }

    if (creds->endpoint != QCRYPTO_TLS_CREDS_ENDPOINT_SERVER) {
        error_setg(errp,
                   "Expecting TLS credentials with a server endpoint");
        return NULL;
    }
    object_ref(obj);
    return creds;
}


void qmp_nbd_server_start(SocketAddress *addr,
                          bool has_tls_creds, const char *tls_creds,
                          Error **errp)
{
    if (nbd_server) {
        error_setg(errp, "NBD server already running");
        return;
    }

    nbd_server = g_new0(NBDServerData, 1);
    nbd_server->watch = -1;
    nbd_server->listen_ioc = qio_channel_socket_new();
    qio_channel_set_name(QIO_CHANNEL(nbd_server->listen_ioc),
                         "nbd-listener");
    if (qio_channel_socket_listen_sync(
            nbd_server->listen_ioc, addr, errp) < 0) {
        goto error;
    }

    if (has_tls_creds) {
        nbd_server->tlscreds = nbd_get_tls_creds(tls_creds, errp);
        if (!nbd_server->tlscreds) {
            goto error;
        }

        /* TODO SOCKET_ADDRESS_KIND_FD where fd has AF_INET or AF_INET6 */
        if (addr->type != SOCKET_ADDRESS_KIND_INET) {
            error_setg(errp, "TLS is only supported with IPv4/IPv6");
            goto error;
        }
    }

    nbd_server->watch = qio_channel_add_watch(
        QIO_CHANNEL(nbd_server->listen_ioc),
        G_IO_IN,
        nbd_accept,
        NULL,
        NULL);

    return;

 error:
    nbd_server_free(nbd_server);
    nbd_server = NULL;
}

void qmp_nbd_server_add(const char *device, bool has_writable, bool writable,
                        Error **errp)
{
    BlockDriverState *bs = NULL;
    BlockBackend *on_eject_blk;
    NBDExport *exp;

    if (!nbd_server) {
        error_setg(errp, "NBD server not running");
        return;
    }

    if (nbd_export_find(device)) {
        error_setg(errp, "NBD server already exporting device '%s'", device);
        return;
    }

    on_eject_blk = blk_by_name(device);

    bs = bdrv_lookup_bs(device, device, errp);
    if (!bs) {
        return;
    }

    if (!has_writable) {
        writable = false;
    }
    if (bdrv_is_read_only(bs)) {
        writable = false;
    }

    exp = nbd_export_new(bs, 0, -1, writable ? 0 : NBD_FLAG_READ_ONLY,
                         NULL, false, on_eject_blk, errp);
    if (!exp) {
        return;
    }

    nbd_export_set_name(exp, device);

    /* The list of named exports has a strong reference to this export now and
     * our only way of accessing it is through nbd_export_find(), so we can drop
     * the strong reference that is @exp. */
    nbd_export_put(exp);
}

void qmp_nbd_server_stop(Error **errp)
{
    nbd_export_close_all();

    nbd_server_free(nbd_server);
    nbd_server = NULL;
}