systemd/src/bus-proxyd/bus-proxyd.c

/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/

/***
  This file is part of systemd.

  Copyright 2010 Lennart Poettering
  Copyright 2013 Daniel Mack
  Copyright 2014 Kay Sievers

  systemd is free software; you can redistribute it and/or modify it
  under the terms of the GNU Lesser General Public License as published by
  the Free Software Foundation; either version 2.1 of the License, or
  (at your option) any later version.

  systemd is distributed in the hope that it will be useful, but
  WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  Lesser General Public License for more details.

  You should have received a copy of the GNU Lesser General Public License
  along with systemd; If not, see <http://www.gnu.org/licenses/>.
***/

#include <sys/socket.h>
#include <sys/un.h>
#include <sys/types.h>
#include <fcntl.h>
#include <unistd.h>
#include <string.h>
#include <errno.h>
#include <sys/poll.h>
#include <stddef.h>
#include <getopt.h>

#include "log.h"
#include "util.h"
#include "socket-util.h"
#include "sd-daemon.h"
#include "sd-bus.h"
#include "bus-internal.h"
#include "bus-message.h"
#include "bus-util.h"
#include "bus-internal.h"
#include "build.h"
#include "strv.h"
#include "def.h"
#include "capability.h"
#include "bus-policy.h"

static char *arg_address = NULL;
static char *arg_command_line_buffer = NULL;
static bool arg_drop_privileges = false;
static char **arg_configuration = NULL;

static int help(void) {

        printf("%s [OPTIONS...]\n\n"
               "Connect STDIO or a socket to a given bus address.\n\n"
               "  -h --help               Show this help\n"
               "     --version            Show package version\n"
               "     --drop-privileges    Drop privileges\n"
               "     --configuration=PATH Configuration file or directory\n"
               "     --machine=MACHINE    Connect to specified machine\n"
               "     --address=ADDRESS    Connect to the bus specified by ADDRESS\n"
               "                          (default: " DEFAULT_SYSTEM_BUS_PATH ")\n",
               program_invocation_short_name);

        return 0;
}

static int parse_argv(int argc, char *argv[]) {

        enum {
                ARG_VERSION = 0x100,
                ARG_ADDRESS,
                ARG_DROP_PRIVILEGES,
                ARG_CONFIGURATION,
                ARG_MACHINE,
        };

        static const struct option options[] = {
                { "help",            no_argument,       NULL, 'h'                 },
                { "version",         no_argument,       NULL, ARG_VERSION         },
                { "address",         required_argument, NULL, ARG_ADDRESS         },
                { "drop-privileges", no_argument,       NULL, ARG_DROP_PRIVILEGES },
                { "configuration",   required_argument, NULL, ARG_CONFIGURATION   },
                { "machine",         required_argument, NULL, ARG_MACHINE         },
                {},
        };

        int c, r;

        assert(argc >= 0);
        assert(argv);

        while ((c = getopt_long(argc, argv, "h", options, NULL)) >= 0)

                switch (c) {

                case 'h':
                        help();
                        return 0;

                case ARG_VERSION:
                        puts(PACKAGE_STRING);
                        puts(SYSTEMD_FEATURES);
                        return 0;

                case ARG_ADDRESS: {
                        char *a;

                        a = strdup(optarg);
                        if (!a)
                                return log_oom();

                        free(arg_address);
                        arg_address = a;
                        break;
                }

                case ARG_DROP_PRIVILEGES:
                        arg_drop_privileges = true;
                        break;

                case ARG_CONFIGURATION:
                        r = strv_extend(&arg_configuration, optarg);
                        if (r < 0)
                                return log_oom();
                        break;

                case ARG_MACHINE: {
                        _cleanup_free_ char *e = NULL;
                        char *a;

                        e = bus_address_escape(optarg);
                        if (!e)
                                return log_oom();

#ifdef ENABLE_KDBUS
                        a = strjoin("x-container-kernel:machine=", e, ";x-container-unix:machine=", e, NULL);
#else
                        a = strjoin("x-container-unix:machine=", e, NULL);
#endif
                        if (!a)
                                return log_oom();

                        free(arg_address);
                        arg_address = a;

                        break;
                }

                case '?':
                        return -EINVAL;

                default:
                        assert_not_reached("Unhandled option");
                }

        /* If the first command line argument is only "x" characters
         * we'll write who we are talking to into it, so that "ps" is
         * explanatory */
        arg_command_line_buffer = argv[optind];
        if (argc > optind + 1 || (arg_command_line_buffer && !in_charset(arg_command_line_buffer, "x"))) {
                log_error("Too many arguments");
                return -EINVAL;
        }

        if (!arg_address) {
                arg_address = strdup(DEFAULT_SYSTEM_BUS_PATH);
                if (!arg_address)
                        return log_oom();
        }

        return 1;
}

static int rename_service(sd_bus *a, sd_bus *b) {
        _cleanup_bus_creds_unref_ sd_bus_creds *creds = NULL;
        _cleanup_free_ char *p = NULL, *name = NULL;
        const char *comm;
        char **cmdline;
        uid_t uid;
        pid_t pid;
        int r;

        assert(a);
        assert(b);

        r = sd_bus_get_peer_creds(b, SD_BUS_CREDS_UID|SD_BUS_CREDS_PID|SD_BUS_CREDS_CMDLINE|SD_BUS_CREDS_COMM, &creds);
        if (r < 0)
                return r;

        r = sd_bus_creds_get_uid(creds, &uid);
        if (r < 0)
                return r;

        r = sd_bus_creds_get_pid(creds, &pid);
        if (r < 0)
                return r;

        r = sd_bus_creds_get_cmdline(creds, &cmdline);
        if (r < 0)
                return r;

        r = sd_bus_creds_get_comm(creds, &comm);
        if (r < 0)
                return r;

        name = uid_to_name(uid);
        if (!name)
                return -ENOMEM;

        p = strv_join(cmdline, " ");
        if (!p)
                return -ENOMEM;

        /* The status string gets the full command line ... */
        sd_notifyf(false,
                   "STATUS=Processing requests from client PID "PID_FMT" (%s); UID "UID_FMT" (%s)",
                   pid, p,
                   uid, name);

        /* ... and the argv line only the short comm */
        if (arg_command_line_buffer) {
                size_t m, w;

                m = strlen(arg_command_line_buffer);
                w = snprintf(arg_command_line_buffer, m,
                             "[PID "PID_FMT"/%s; UID "UID_FMT"/%s]",
                             pid, comm,
                             uid, name);

                if (m > w)
                        memzero(arg_command_line_buffer + w, m - w);
        }

        log_debug("Running on behalf of PID "PID_FMT" (%s), UID "UID_FMT" (%s), %s",
                  pid, p,
                  uid, name,
                  a->unique_name);
                ;
        return 0;
}

static int synthesize_name_acquired(sd_bus *a, sd_bus *b, sd_bus_message *m) {
        _cleanup_bus_message_unref_ sd_bus_message *n = NULL;
        const char *name, *old_owner, *new_owner;
        int r;

        assert(a);
        assert(b);
        assert(m);

        /* If we get NameOwnerChanged for our own name, we need to
         * synthesize NameLost/NameAcquired, since socket clients need
         * that, even though it is obsoleted on kdbus */

        if (!a->is_kernel)
                return 0;

        if (!sd_bus_message_is_signal(m, "org.freedesktop.DBus", "NameOwnerChanged") ||
            !streq_ptr(m->path, "/org/freedesktop/DBus") ||
            !streq_ptr(m->sender, "org.freedesktop.DBus"))
                return 0;

        r = sd_bus_message_read(m, "sss", &name, &old_owner, &new_owner);
        if (r < 0)
                return r;

        r = sd_bus_message_rewind(m, true);
        if (r < 0)
                return r;

        if (streq(old_owner, a->unique_name)) {

                r = sd_bus_message_new_signal(
                                b,
                                &n,
                                "/org/freedesktop/DBus",
                                "org.freedesktop.DBus",
                                "NameLost");

        } else if (streq(new_owner, a->unique_name)) {

                r = sd_bus_message_new_signal(
                                b,
                                &n,
                                "/org/freedesktop/DBus",
                                "org.freedesktop.DBus",
                                "NameAcquired");
        } else
                return 0;

        if (r < 0)
                return r;

        r = sd_bus_message_append(n, "s", name);
        if (r < 0)
                return r;

        r = bus_message_append_sender(n, "org.freedesktop.DBus");
        if (r < 0)
                return r;

        r = bus_seal_synthetic_message(b, n);
        if (r < 0)
                return r;

        return sd_bus_send(b, n, NULL);
}

static int process_policy(sd_bus *a, sd_bus *b, sd_bus_message *m) {
        _cleanup_bus_message_unref_ sd_bus_message *n = NULL;
        int r;

        assert(a);
        assert(b);
        assert(m);

        if (!a->is_kernel)
                return 0;

        if (!sd_bus_message_is_method_call(m, "org.freedesktop.DBus.Properties", "GetAll"))
                return 0;

        if (!streq_ptr(m->path, "/org/gnome/DisplayManager/Slave"))
                return 0;

        r = sd_bus_message_new_method_errorf(m, &n, SD_BUS_ERROR_ACCESS_DENIED, "gdm, you are stupid");
        if (r < 0)
                return r;

        r = bus_message_append_sender(n, "org.freedesktop.DBus");
        if (r < 0) {
                log_error("Failed to append sender to gdm reply: %s", strerror(-r));
                return r;
        }

        r = bus_seal_synthetic_message(b, n);
        if (r < 0) {
                log_error("Failed to seal gdm reply: %s", strerror(-r));
                return r;
        }

        r = sd_bus_send(b, n, NULL);
        if (r < 0) {
                log_error("Failed to send gdm reply: %s", strerror(-r));
                return r;
        }

        return 1;
}

static int synthetic_driver_send(sd_bus *b, sd_bus_message *m) {
        int r;

        assert(b);
        assert(m);

        r = bus_message_append_sender(m, "org.freedesktop.DBus");
        if (r < 0)
                return r;

        r = bus_seal_synthetic_message(b, m);
        if (r < 0)
                return r;

        return sd_bus_send(b, m, NULL);
}

static int synthetic_reply_method_error(sd_bus_message *call, const sd_bus_error *e) {
        _cleanup_bus_message_unref_ sd_bus_message *m = NULL;
        int r;

        if (call->header->flags & BUS_MESSAGE_NO_REPLY_EXPECTED)
                return 0;

        r = sd_bus_message_new_method_error(call, &m, e);
        if (r < 0)
                return r;

        return synthetic_driver_send(call->bus, m);
}

static int synthetic_reply_method_errno(sd_bus_message *call, int error, const sd_bus_error *p) {

        _cleanup_bus_error_free_ sd_bus_error berror = SD_BUS_ERROR_NULL;

        if (call->header->flags & BUS_MESSAGE_NO_REPLY_EXPECTED)
                return 0;

        if (sd_bus_error_is_set(p))
                return synthetic_reply_method_error(call, p);

        sd_bus_error_set_errno(&berror, error);

        return synthetic_reply_method_error(call, &berror);
}

static int synthetic_reply_method_return(sd_bus_message *call, const char *types, ...) {
        _cleanup_bus_message_unref_ sd_bus_message *m = NULL;
        int r;

        if (call->header->flags & BUS_MESSAGE_NO_REPLY_EXPECTED)
                return 0;

        r = sd_bus_message_new_method_return(call, &m);
        if (r < 0)
                return r;

        if (!isempty(types)) {
                va_list ap;

                va_start(ap, types);
                r = bus_message_append_ap(m, types, ap);
                va_end(ap);
                if (r < 0)
                        return r;
        }

        return synthetic_driver_send(call->bus, m);
}

static int synthetic_reply_return_strv(sd_bus_message *call, char **l) {
        _cleanup_bus_message_unref_ sd_bus_message *m = NULL;
        int r;

        r = sd_bus_message_new_method_return(call, &m);
        if (r < 0)
                return synthetic_reply_method_errno(call, r, NULL);

        r = sd_bus_message_append_strv(m, l);
        if (r < 0)
                return synthetic_reply_method_errno(call, r, NULL);

        return synthetic_driver_send(call->bus, m);
}

static int get_creds_by_name(sd_bus *bus, const char *name, uint64_t mask, sd_bus_creds **_creds, sd_bus_error *error) {
        _cleanup_bus_creds_unref_ sd_bus_creds *c = NULL;
        int r;

        assert(bus);
        assert(name);
        assert(_creds);

        assert_return(service_name_is_valid(name), -EINVAL);

        r = sd_bus_get_owner(bus, name, mask, &c);
        if (r == -ESRCH || r == -ENXIO)
                return sd_bus_error_setf(error, SD_BUS_ERROR_NAME_HAS_NO_OWNER, "Name %s is currently not owned by anyone.", name);
        if (r < 0)
                return r;

        if ((c->mask & mask) != mask)
                return -ENOTSUP;

        *_creds = c;
        c = NULL;

        return 0;
}

static int get_creds_by_message(sd_bus *bus, sd_bus_message *m, uint64_t mask, sd_bus_creds **_creds, sd_bus_error *error) {
        const char *name;
        int r;

        assert(bus);
        assert(m);
        assert(_creds);

        r = sd_bus_message_read(m, "s", &name);
        if (r < 0)
                return r;

        return get_creds_by_name(bus, name, mask, _creds, error);
}

static int peer_is_privileged(sd_bus *bus, sd_bus_message *m) {
        _cleanup_bus_creds_unref_ sd_bus_creds *creds = NULL;
        uid_t uid;
        int r;

        r = get_creds_by_message(bus, m, SD_BUS_CREDS_UID, &creds, NULL);
        if (r < 0)
                return r;

        r = sd_bus_creds_get_uid(creds, &uid);
        if (r < 0)
                return r;

        r = sd_bus_creds_has_effective_cap(creds, CAP_SYS_ADMIN);
        if (r > 0)
                return true;

        if (uid == getuid())
                return true;

        return false;
}

static int process_driver(sd_bus *a, sd_bus *b, sd_bus_message *m) {
        int r;

        assert(a);
        assert(b);
        assert(m);

        if (!a->is_kernel)
                return 0;

        if (!streq_ptr(sd_bus_message_get_destination(m), "org.freedesktop.DBus"))
                return 0;

        if (sd_bus_message_is_method_call(m, "org.freedesktop.DBus.Introspectable", "Introspect")) {
                if (0 && !isempty(sd_bus_message_get_signature(m, true))) {
                        _cleanup_bus_error_free_ sd_bus_error error = SD_BUS_ERROR_NULL;

                        r = sd_bus_error_setf(&error, SD_BUS_ERROR_INVALID_ARGS, "Expected no parameters");

                        return synthetic_reply_method_errno(m, r, &error);
                }

                return synthetic_reply_method_return(m, "s",
                        "<!DOCTYPE node PUBLIC \"-//freedesktop//DTD D-BUS Object Introspection 1.0//EN\" "
                          "\"http://www.freedesktop.org/standards/dbus/1.0/introspect.dtd\">\n"
                        "<node>\n"
                        " <interface name=\"org.freedesktop.DBus.Introspectable\">\n"
                        "  <method name=\"Introspect\">\n"
                        "   <arg name=\"data\" type=\"s\" direction=\"out\"/>\n"
                        "  </method>\n"
                        " </interface>\n"
                        " <interface name=\"org.freedesktop.DBus\">\n"
                        "  <method name=\"AddMatch\">\n"
                        "   <arg type=\"s\" direction=\"in\"/>\n"
                        "  </method>\n"
                        "  <method name=\"RemoveMatch\">\n"
                        "   <arg type=\"s\" direction=\"in\"/>\n"
                        "  </method>\n"
                        "  <method name=\"GetConnectionSELinuxSecurityContext\">\n"
                        "   <arg type=\"s\" direction=\"in\"/>\n"
                        "   <arg type=\"ay\" direction=\"out\"/>\n"
                        "  </method>\n"
                        "  <method name=\"GetConnectionUnixProcessID\">\n"
                        "   <arg type=\"s\" direction=\"in\"/>\n"
                        "   <arg type=\"u\" direction=\"out\"/>\n"
                        "  </method>\n"
                        "  <method name=\"GetConnectionUnixUser\">\n"
                        "   <arg type=\"s\" direction=\"in\"/>\n"
                        "   <arg type=\"u\" direction=\"out\"/>\n"
                        "  </method>\n"
                        "  <method name=\"GetId\">\n"
                        "   <arg type=\"s\" direction=\"out\"/>\n"
                        "  </method>\n"
                        "  <method name=\"GetNameOwner\">\n"
                        "   <arg type=\"s\" direction=\"in\"/>\n"
                        "   <arg type=\"s\" direction=\"out\"/>\n"
                        "  </method>\n"
                        "  <method name=\"Hello\">\n"
                        "   <arg type=\"s\" direction=\"out\"/>\n"
                        "  </method>\n"
                        "  <method name=\"ListActivatableNames\">\n"
                        "   <arg type=\"as\" direction=\"out\"/>\n"
                        "  </method>\n"
                        "  <method name=\"ListNames\">\n"
                        "   <arg type=\"as\" direction=\"out\"/>\n"
                        "  </method>\n"
                        "  <method name=\"ListQueuedOwners\">\n"
                        "   <arg type=\"s\" direction=\"in\"/>\n"
                        "   <arg type=\"as\" direction=\"out\"/>\n"
                        "  </method>\n"
                        "  <method name=\"NameHasOwner\">\n"
                        "   <arg type=\"s\" direction=\"in\"/>\n"
                        "   <arg type=\"b\" direction=\"out\"/>\n"
                        "  </method>\n"
                        "  <method name=\"ReleaseName\">\n"
                        "   <arg type=\"s\" direction=\"in\"/>\n"
                        "   <arg type=\"u\" direction=\"out\"/>\n"
                        "  </method>\n"
                        "  <method name=\"ReloadConfig\">\n"
                        "  </method>\n"
                        "  <method name=\"RequestName\">\n"
                        "   <arg type=\"s\" direction=\"in\"/>\n"
                        "   <arg type=\"u\" direction=\"in\"/>\n"
                        "   <arg type=\"u\" direction=\"out\"/>\n"
                        "  </method>\n"
                        "  <method name=\"StartServiceByName\">\n"
                        "   <arg type=\"s\" direction=\"in\"/>\n"
                        "   <arg type=\"u\" direction=\"in\"/>\n"
                        "   <arg type=\"u\" direction=\"out\"/>\n"
                        "  </method>\n"
                        "  <method name=\"UpdateActivationEnvironment\">\n"
                        "   <arg type=\"a{ss}\" direction=\"in\"/>\n"
                        "  </method>\n"
                        "  <signal name=\"NameAcquired\">\n"
                        "   <arg type=\"s\"/>\n"
                        "  </signal>\n"
                        "  <signal name=\"NameLost\">\n"
                        "   <arg type=\"s\"/>\n"
                        "  </signal>\n"
                        "  <signal name=\"NameOwnerChanged\">\n"
                        "   <arg type=\"s\"/>\n"
                        "   <arg type=\"s\"/>\n"
                        "   <arg type=\"s\"/>\n"
                        "  </signal>\n"
                        " </interface>\n"
                        "</node>\n");

        } else if (sd_bus_message_is_method_call(m, "org.freedesktop.DBus", "AddMatch")) {
                const char *match;

                r = sd_bus_message_read(m, "s", &match);
                if (r < 0)
                        return synthetic_reply_method_errno(m, r, NULL);

                r = sd_bus_add_match(a, NULL, match, NULL, NULL);
                if (r < 0)
                        return synthetic_reply_method_errno(m, r, NULL);

                return synthetic_reply_method_return(m, NULL);

        } else if (sd_bus_message_is_method_call(m, "org.freedesktop.DBus", "RemoveMatch")) {
                const char *match;

                r = sd_bus_message_read(m, "s", &match);
                if (r < 0)
                        return synthetic_reply_method_errno(m, r, NULL);

                r = bus_remove_match_by_string(a, match, NULL, NULL);
                if (r == 0)
                        return synthetic_reply_method_error(m, &SD_BUS_ERROR_MAKE_CONST(SD_BUS_ERROR_MATCH_RULE_NOT_FOUND, "Match rule not found"));
                if (r < 0)
                        return synthetic_reply_method_errno(m, r, NULL);

                return synthetic_reply_method_return(m, NULL);

        } else if (sd_bus_message_is_method_call(m, "org.freedesktop.DBus", "GetConnectionSELinuxSecurityContext")) {
                _cleanup_bus_creds_unref_ sd_bus_creds *creds = NULL;

                r = get_creds_by_message(a, m, SD_BUS_CREDS_SELINUX_CONTEXT, &creds, NULL);
                if (r < 0)
                        return synthetic_reply_method_errno(m, r, NULL);

                return synthetic_reply_method_return(m, "y", creds->label, strlen(creds->label));

        } else if (sd_bus_message_is_method_call(m, "org.freedesktop.DBus", "GetConnectionUnixProcessID")) {
                _cleanup_bus_creds_unref_ sd_bus_creds *creds = NULL;

                r = get_creds_by_message(a, m, SD_BUS_CREDS_PID, &creds, NULL);
                if (r < 0)
                        return synthetic_reply_method_errno(m, r, NULL);

                return synthetic_reply_method_return(m, "u", (uint32_t) creds->pid);

        } else if (sd_bus_message_is_method_call(m, "org.freedesktop.DBus", "GetConnectionUnixUser")) {
                _cleanup_bus_creds_unref_ sd_bus_creds *creds = NULL;

                r = get_creds_by_message(a, m, SD_BUS_CREDS_UID, &creds, NULL);
                if (r < 0)
                        return synthetic_reply_method_errno(m, r, NULL);

                return synthetic_reply_method_return(m, "u", (uint32_t) creds->uid);

        } else if (sd_bus_message_is_method_call(m, "org.freedesktop.DBus", "GetId")) {
                sd_id128_t server_id;
                char buf[SD_ID128_STRING_MAX];

                r = sd_bus_get_server_id(a, &server_id);
                if (r < 0)
                        return synthetic_reply_method_errno(m, r, NULL);

                return synthetic_reply_method_return(m, "s", sd_id128_to_string(server_id, buf));

        } else if (sd_bus_message_is_method_call(m, "org.freedesktop.DBus", "GetNameOwner")) {
                const char *name;
                _cleanup_bus_creds_unref_ sd_bus_creds *creds = NULL;
                _cleanup_bus_error_free_ sd_bus_error error = SD_BUS_ERROR_NULL;

                r = sd_bus_message_read(m, "s", &name);
                if (r < 0)
                        return synthetic_reply_method_errno(m, r, NULL);

                if (streq(name, "org.freedesktop.DBus"))
                        return synthetic_reply_method_return(m, "s", "org.freedesktop.DBus");

                r = get_creds_by_name(a, name, SD_BUS_CREDS_UNIQUE_NAME, &creds, &error);
                if (r < 0)
                        return synthetic_reply_method_errno(m, r, &error);

                return synthetic_reply_method_return(m, "s", creds->unique_name);

        /* "Hello" is handled in process_hello() */

        } else if (sd_bus_message_is_method_call(m, "org.freedesktop.DBus", "ListActivatableNames")) {
                _cleanup_strv_free_ char **names = NULL;

                r = sd_bus_list_names(a, NULL, &names);
                if (r < 0)
                        return synthetic_reply_method_errno(m, r, NULL);

                /* Let's sort the names list to make it stable */
                strv_sort(names);

                return synthetic_reply_return_strv(m, names);

        } else if (sd_bus_message_is_method_call(m, "org.freedesktop.DBus", "ListNames")) {
                _cleanup_strv_free_ char **names = NULL;

                r = sd_bus_list_names(a, &names, NULL);
                if (r < 0)
                        return synthetic_reply_method_errno(m, r, NULL);

                r = strv_extend(&names, "org.freedesktop.DBus");
                if (r < 0)
                        return synthetic_reply_method_errno(m, r, NULL);

                /* Let's sort the names list to make it stable */
                strv_sort(names);

                return synthetic_reply_return_strv(m, names);

        } else if (sd_bus_message_is_method_call(m, "org.freedesktop.DBus", "ListQueuedOwners")) {
                struct kdbus_cmd_name_list cmd = {};
                struct kdbus_name_list *name_list;
                struct kdbus_cmd_name *name;
                _cleanup_strv_free_ char **owners = NULL;
                char *arg0;
                int err = 0;

                r = sd_bus_message_read(m, "s", &arg0);
                if (r < 0)
                        return synthetic_reply_method_errno(m, r, NULL);

                if (!service_name_is_valid(arg0))
                        return synthetic_reply_method_errno(m, -EINVAL, NULL);

                cmd.flags = KDBUS_NAME_LIST_QUEUED;
                r = ioctl(a->input_fd, KDBUS_CMD_NAME_LIST, &cmd);
                if (r < 0)
                        return synthetic_reply_method_errno(m, -errno, NULL);

                name_list = (struct kdbus_name_list *) ((uint8_t *) a->kdbus_buffer + cmd.offset);

                KDBUS_ITEM_FOREACH(name, name_list, names) {
                        char *n;

                        if (name->size <= sizeof(*name))
                                continue;

                        if (!streq(name->name, arg0))
                                continue;

                        if (asprintf(&n, ":1.%llu", (unsigned long long) name->owner_id) < 0) {
                                err  = -ENOMEM;
                                break;
                        }

                        r = strv_consume(&owners, n);
                        if (r < 0) {
                                err = r;
                                break;
                        }
                }

                r = ioctl(a->input_fd, KDBUS_CMD_FREE, &cmd.offset);
                if (r < 0)
                        return synthetic_reply_method_errno(m, r, NULL);

                if (err < 0)
                        return synthetic_reply_method_errno(m, err, NULL);

                return synthetic_reply_return_strv(m, owners);

        } else if (sd_bus_message_is_method_call(m, "org.freedesktop.DBus", "NameHasOwner")) {
                const char *name;

                r = sd_bus_message_read(m, "s", &name);
                if (r < 0)
                        return synthetic_reply_method_errno(m, r, NULL);

                if (!service_name_is_valid(name))
                        return synthetic_reply_method_errno(m, -EINVAL, NULL);

                if (streq(name, "org.freedesktop.DBus"))
                        return synthetic_reply_method_return(m, "b", true);

                r = sd_bus_get_owner(a, name, 0, NULL);
                if (r < 0 && r != -ESRCH && r != -ENXIO)
                        return synthetic_reply_method_errno(m, r, NULL);

                return synthetic_reply_method_return(m, "b", r >= 0);

        } else if (sd_bus_message_is_method_call(m, "org.freedesktop.DBus", "ReleaseName")) {
                const char *name;

                r = sd_bus_message_read(m, "s", &name);
                if (r < 0)
                        return synthetic_reply_method_errno(m, r, NULL);

                if (!service_name_is_valid(name))
                        return synthetic_reply_method_errno(m, -EINVAL, NULL);

                r = sd_bus_release_name(a, name);
                if (r < 0) {
                        if (r == -ESRCH)
                                return synthetic_reply_method_return(m, "u", BUS_NAME_NON_EXISTENT);
                        if (r == -EADDRINUSE)
                                return synthetic_reply_method_return(m, "u", BUS_NAME_NOT_OWNER);

                        return synthetic_reply_method_errno(m, r, NULL);
                }

                return synthetic_reply_method_return(m, "u", BUS_NAME_RELEASED);

        } else if (sd_bus_message_is_method_call(m, "org.freedesktop.DBus", "ReloadConfig")) {
                _cleanup_bus_error_free_ sd_bus_error error = SD_BUS_ERROR_NULL;

                r = sd_bus_error_setf(&error, SD_BUS_ERROR_NOT_SUPPORTED, "%s() is not supported", sd_bus_message_get_member(m));

                return synthetic_reply_method_errno(m, r, &error);

        } else if (sd_bus_message_is_method_call(m, "org.freedesktop.DBus", "RequestName")) {
                const char *name;
                uint32_t flags;

                r = sd_bus_message_read(m, "su", &name, &flags);
                if (r < 0)
                        return synthetic_reply_method_errno(m, r, NULL);

                if (!service_name_is_valid(name))
                        return synthetic_reply_method_errno(m, -EINVAL, NULL);
                if ((flags & ~(BUS_NAME_ALLOW_REPLACEMENT|BUS_NAME_REPLACE_EXISTING|BUS_NAME_DO_NOT_QUEUE)) != 0)
                        return synthetic_reply_method_errno(m, -EINVAL, NULL);

                r = sd_bus_request_name(a, name, flags);
                if (r < 0) {
                        if (r == -EEXIST)
                                return synthetic_reply_method_return(m, "u", BUS_NAME_EXISTS);
                        if (r == -EALREADY)
                                return synthetic_reply_method_return(m, "u", BUS_NAME_ALREADY_OWNER);
                        return synthetic_reply_method_errno(m, r, NULL);
                }

                if (r == 0)
                        return synthetic_reply_method_return(m, "u", BUS_NAME_IN_QUEUE);

                return synthetic_reply_method_return(m, "u", BUS_NAME_PRIMARY_OWNER);

        } else if (sd_bus_message_is_method_call(m, "org.freedesktop.DBus", "StartServiceByName")) {
                _cleanup_bus_message_unref_ sd_bus_message *msg = NULL;
                const char *name;
                uint32_t flags;

                r = sd_bus_message_read(m, "su", &name, &flags);
                if (r < 0)
                        return synthetic_reply_method_errno(m, r, NULL);

                if (!service_name_is_valid(name))
                        return synthetic_reply_method_errno(m, -EINVAL, NULL);
                if (flags != 0)
                        return synthetic_reply_method_errno(m, -EINVAL, NULL);

                r = sd_bus_get_owner(a, name, 0, NULL);
                if (r >= 0 || streq(name, "org.freedesktop.DBus"))
                        return synthetic_reply_method_return(m, "u", BUS_START_REPLY_ALREADY_RUNNING);
                if (r != -ESRCH)
                        return synthetic_reply_method_errno(m, r, NULL);

                r = sd_bus_message_new_method_call(
                                a,
                                &msg,
                                name,
                                "/",
                                "org.freedesktop.DBus.Peer",
                                "Ping");
                if (r < 0)
                        return synthetic_reply_method_errno(m, r, NULL);

                r = sd_bus_send(a, msg, NULL);
                if (r < 0)
                        return synthetic_reply_method_errno(m, r, NULL);

                return synthetic_reply_method_return(m, "u", BUS_START_REPLY_SUCCESS);

        } else if (sd_bus_message_is_method_call(m, "org.freedesktop.DBus", "UpdateActivationEnvironment")) {
                _cleanup_bus_message_unref_ sd_bus_message *msg = NULL;
                _cleanup_strv_free_ char **args = NULL;

                if (!peer_is_privileged(a, m))
                        return synthetic_reply_method_errno(m, -EPERM, NULL);

                r = sd_bus_message_enter_container(m, SD_BUS_TYPE_ARRAY, "{ss}");
                if (r < 0)
                        return synthetic_reply_method_errno(m, r, NULL);

                while ((r = sd_bus_message_enter_container(m, SD_BUS_TYPE_DICT_ENTRY, "ss")) > 0) {
                        _cleanup_free_ char *s = NULL;
                        const char *key;
                        const char *value;

                        r = sd_bus_message_read(m, "ss", &key, &value);
                        if (r < 0)
                                return synthetic_reply_method_errno(m, r, NULL);

                        s = strjoin(key, "=", value, NULL);
                        if (!s)
                                return synthetic_reply_method_errno(m, -ENOMEM, NULL);

                        r  = strv_extend(&args, s);
                        if (r < 0)
                                return synthetic_reply_method_errno(m, r, NULL);

                        r = sd_bus_message_exit_container(m);
                        if (r < 0)
                                return synthetic_reply_method_errno(m, r, NULL);
                }

                r = sd_bus_message_exit_container(m);
                if (r < 0)
                        return synthetic_reply_method_errno(m, r, NULL);

                if (!args)
                        return synthetic_reply_method_errno(m, -EINVAL, NULL);

                r = sd_bus_message_new_method_call(
                                a,
                                &msg,
                                "org.freedesktop.systemd1",
                                "/org/freedesktop/systemd1",
                                "org.freedesktop.systemd1.Manager",
                                "SetEnvironment");
                if (r < 0)
                        return synthetic_reply_method_errno(m, r, NULL);

                r = sd_bus_message_append_strv(msg, args);
                if (r < 0)
                        return synthetic_reply_method_errno(m, r, NULL);

                r = sd_bus_call(a, msg, 0, NULL, NULL);
                if (r < 0)
                        return synthetic_reply_method_errno(m, r, NULL);

               return synthetic_reply_method_return(m, NULL);

        } else {
                _cleanup_bus_error_free_ sd_bus_error error = SD_BUS_ERROR_NULL;

                r = sd_bus_error_setf(&error, SD_BUS_ERROR_UNKNOWN_METHOD, "Unknown method '%s'.", m->member);

                return synthetic_reply_method_errno(m, r, &error);
        }
}

static int process_hello(sd_bus *a, sd_bus *b, sd_bus_message *m, bool *got_hello) {
        _cleanup_bus_message_unref_ sd_bus_message *n = NULL;
        bool is_hello;
        int r;

        assert(a);
        assert(b);
        assert(m);
        assert(got_hello);

        /* As reaction to hello we need to respond with two messages:
         * the callback reply and the NameAcquired for the unique
         * name, since hello is otherwise obsolete on kdbus. */

        is_hello =
                sd_bus_message_is_method_call(m, "org.freedesktop.DBus", "Hello") &&
                streq_ptr(m->destination, "org.freedesktop.DBus");

        if (!is_hello) {

                if (*got_hello)
                        return 0;

                log_error("First packet isn't hello (it's %s.%s), aborting.", m->interface, m->member);
                return -EIO;
        }

        if (*got_hello) {
                log_error("Got duplicate hello, aborting.");
                return -EIO;
        }

        *got_hello = true;

        if (!a->is_kernel)
                return 0;

        r = sd_bus_message_new_method_return(m, &n);
        if (r < 0) {
                log_error("Failed to generate HELLO reply: %s", strerror(-r));
                return r;
        }

        r = sd_bus_message_append(n, "s", a->unique_name);
        if (r < 0) {
                log_error("Failed to append unique name to HELLO reply: %s", strerror(-r));
                return r;
        }

        r = bus_message_append_sender(n, "org.freedesktop.DBus");
        if (r < 0) {
                log_error("Failed to append sender to HELLO reply: %s", strerror(-r));
                return r;
        }

        r = bus_seal_synthetic_message(b, n);
        if (r < 0) {
                log_error("Failed to seal HELLO reply: %s", strerror(-r));
                return r;
        }

        r = sd_bus_send(b, n, NULL);
        if (r < 0) {
                log_error("Failed to send HELLO reply: %s", strerror(-r));
                return r;
        }

        n = sd_bus_message_unref(n);
        r = sd_bus_message_new_signal(
                        b,
                        &n,
                        "/org/freedesktop/DBus",
                        "org.freedesktop.DBus",
                        "NameAcquired");
        if (r < 0) {
                log_error("Failed to allocate initial NameAcquired message: %s", strerror(-r));
                return r;
        }

        r = sd_bus_message_append(n, "s", a->unique_name);
        if (r < 0) {
                log_error("Failed to append unique name to NameAcquired message: %s", strerror(-r));
                return r;
        }

        r = bus_message_append_sender(n, "org.freedesktop.DBus");
        if (r < 0) {
                log_error("Failed to append sender to NameAcquired message: %s", strerror(-r));
                return r;
        }

        r = bus_seal_synthetic_message(b, n);
        if (r < 0) {
                log_error("Failed to seal NameAcquired message: %s", strerror(-r));
                return r;
        }

        r = sd_bus_send(b, n, NULL);
        if (r < 0) {
                log_error("Failed to send NameAcquired message: %s", strerror(-r));
                return r;
        }

        return 1;
}

static int patch_sender(sd_bus *a, sd_bus_message *m) {
        char **well_known = NULL;
        sd_bus_creds *c;
        int r;

        assert(a);
        assert(m);

        if (!a->is_kernel)
                return 0;

        /* We will change the sender of messages from the bus driver
         * so that they originate from the bus driver. This is a
         * speciality originating from dbus1, where the bus driver did
         * not have a unique id, but only the well-known name. */

        c = sd_bus_message_get_creds(m);
        if (!c)
                return 0;

        r = sd_bus_creds_get_well_known_names(c, &well_known);
        if (r < 0)
                return r;

        if (strv_contains(well_known, "org.freedesktop.DBus"))
                m->sender = "org.freedesktop.DBus";

        return 0;
}

int main(int argc, char *argv[]) {

        _cleanup_bus_close_unref_ sd_bus *a = NULL, *b = NULL;
        sd_id128_t server_id;
        int r, in_fd, out_fd;
        bool got_hello = false;
        bool is_unix;
        struct ucred ucred = {};
        _cleanup_free_ char *peersec = NULL;
        Policy policy = {};

        log_set_target(LOG_TARGET_JOURNAL_OR_KMSG);
        log_parse_environment();
        log_open();

        r = parse_argv(argc, argv);
        if (r <= 0)
                goto finish;

        r = policy_load(&policy, arg_configuration);
        if (r < 0) {
                log_error("Failed to load policy: %s", strerror(-r));
                goto finish;
        }

        /* policy_dump(&policy); */

        r = sd_listen_fds(0);
        if (r == 0) {
                in_fd = STDIN_FILENO;
                out_fd = STDOUT_FILENO;
        } else if (r == 1) {
                in_fd = SD_LISTEN_FDS_START;
                out_fd = SD_LISTEN_FDS_START;
        } else {
                log_error("Illegal number of file descriptors passed");
                goto finish;
        }

        is_unix =
                sd_is_socket(in_fd, AF_UNIX, 0, 0) > 0 &&
                sd_is_socket(out_fd, AF_UNIX, 0, 0) > 0;

        if (is_unix) {
                getpeercred(in_fd, &ucred);
                getpeersec(in_fd, &peersec);
        }

        if (arg_drop_privileges) {
                const char *user = "systemd-bus-proxy";
                uid_t uid;
                gid_t gid;

                r = get_user_creds(&user, &uid, &gid, NULL, NULL);
                if (r < 0) {
                        log_error("Cannot resolve user name %s: %s", user, strerror(-r));
                        goto finish;
                }

                r = drop_privileges(uid, gid, 1ULL << CAP_IPC_OWNER);
                if (r < 0)
                        goto finish;
        }

        r = sd_bus_new(&a);
        if (r < 0) {
                log_error("Failed to allocate bus: %s", strerror(-r));
                goto finish;
        }

        r = sd_bus_set_name(a, "sd-proxy");
        if (r < 0) {
                log_error("Failed to set bus name: %s", strerror(-r));
                goto finish;
        }

        r = sd_bus_set_address(a, arg_address);
        if (r < 0) {
                log_error("Failed to set address to connect to: %s", strerror(-r));
                goto finish;
        }

        r = sd_bus_negotiate_fds(a, is_unix);
        if (r < 0) {
                log_error("Failed to set FD negotiation: %s", strerror(-r));
                goto finish;
        }

        if (ucred.pid > 0) {
                a->fake_creds.pid = ucred.pid;
                a->fake_creds.uid = ucred.uid;
                a->fake_creds.gid = ucred.gid;
                a->fake_creds_valid = true;
        }

        if (peersec) {
                a->fake_label = peersec;
                peersec = NULL;
        }

        a->manual_peer_interface = true;

        r = sd_bus_start(a);
        if (r < 0) {
                log_error("Failed to start bus client: %s", strerror(-r));
                goto finish;
        }

        r = sd_bus_get_server_id(a, &server_id);
        if (r < 0) {
                log_error("Failed to get server ID: %s", strerror(-r));
                goto finish;
        }

        r = sd_bus_new(&b);
        if (r < 0) {
                log_error("Failed to allocate bus: %s", strerror(-r));
                goto finish;
        }

        r = sd_bus_set_fd(b, in_fd, out_fd);
        if (r < 0) {
                log_error("Failed to set fds: %s", strerror(-r));
                goto finish;
        }

        r = sd_bus_set_server(b, 1, server_id);
        if (r < 0) {
                log_error("Failed to set server mode: %s", strerror(-r));
                goto finish;
        }

        r = sd_bus_negotiate_fds(b, is_unix);
        if (r < 0) {
                log_error("Failed to set FD negotiation: %s", strerror(-r));
                goto finish;
        }

        r = sd_bus_set_anonymous(b, true);
        if (r < 0) {
                log_error("Failed to set anonymous authentication: %s", strerror(-r));
                goto finish;
        }

        b->manual_peer_interface = true;

        r = sd_bus_start(b);
        if (r < 0) {
                log_error("Failed to start bus client: %s", strerror(-r));
                goto finish;
        }

        r = rename_service(a, b);
        if (r < 0)
                log_debug("Failed to rename process: %s", strerror(-r));

        if (a->is_kernel) {
                _cleanup_free_ char *match = NULL;
                const char *unique;

                r = sd_bus_get_unique_name(a, &unique);
                if (r < 0) {
                        log_error("Failed to get unique name: %s", strerror(-r));
                        goto finish;
                }

                match = strjoin("type='signal',"
                                "sender='org.freedesktop.DBus',"
                                "path='/org/freedesktop/DBus',"
                                "interface='org.freedesktop.DBus',"
                                "member='NameOwnerChanged',"
                                "arg1='",
                                unique,
                                "'",
                                NULL);
                if (!match) {
                        log_oom();
                        goto finish;
                }

                r = sd_bus_add_match(a, NULL, match, NULL, NULL);
                if (r < 0) {
                        log_error("Failed to add match for NameLost: %s", strerror(-r));
                        goto finish;
                }

                free(match);
                match = strjoin("type='signal',"
                                "sender='org.freedesktop.DBus',"
                                "path='/org/freedesktop/DBus',"
                                "interface='org.freedesktop.DBus',"
                                "member='NameOwnerChanged',"
                                "arg2='",
                                unique,
                                "'",
                                NULL);
                if (!match) {
                        log_oom();
                        goto finish;
                }

                r = sd_bus_add_match(a, NULL, match, NULL, NULL);
                if (r < 0) {
                        log_error("Failed to add match for NameAcquired: %s", strerror(-r));
                        goto finish;
                }
        }

        for (;;) {
                _cleanup_bus_message_unref_ sd_bus_message *m = NULL;
                int events_a, events_b, fd;
                uint64_t timeout_a, timeout_b, t;
                struct timespec _ts, *ts;
                struct pollfd *pollfd;
                int k;

                if (got_hello) {
                        r = sd_bus_process(a, &m);
                        if (r < 0) {
                                /* treat 'connection reset by peer' as clean exit condition */
                                if (r == -ECONNRESET)
                                        r = 0;
                                else
                                        log_error("Failed to process bus a: %s", strerror(-r));

                                goto finish;
                        }

                        if (m) {
                                /* We officially got EOF, let's quit */
                                if (sd_bus_message_is_signal(m, "org.freedesktop.DBus.Local", "Disconnected")) {
                                        r = 0;
                                        goto finish;
                                }

                                k = synthesize_name_acquired(a, b, m);
                                if (k < 0) {
                                        r = k;
                                        log_error("Failed to synthesize message: %s", strerror(-r));
                                        goto finish;
                                }

                                patch_sender(a, m);

                                k = sd_bus_send(b, m, NULL);
                                if (k < 0) {
                                        if (k == -ECONNRESET)
                                                r = 0;
                                        else {
                                                r = k;
                                                log_error("Failed to send message: %s", strerror(-r));
                                        }

                                        goto finish;
                                }
                        }

                        if (r > 0)
                                continue;
                }

                r = sd_bus_process(b, &m);
                if (r < 0) {
                        /* treat 'connection reset by peer' as clean exit condition */
                        if (r == -ECONNRESET)
                                r = 0;
                        else
                                log_error("Failed to process bus b: %s", strerror(-r));

                        goto finish;
                }

                if (m) {
                        /* We officially got EOF, let's quit */
                        if (sd_bus_message_is_signal(m, "org.freedesktop.DBus.Local", "Disconnected")) {
                                r = 0;
                                goto finish;
                        }

                        k = process_hello(a, b, m, &got_hello);
                        if (k < 0) {
                                r = k;
                                log_error("Failed to process HELLO: %s", strerror(-r));
                                goto finish;
                        }

                        if (k > 0)
                                r = k;
                        else {
                                k = process_policy(a, b, m);
                                if (k < 0) {
                                        r = k;
                                        log_error("Failed to process policy: %s", strerror(-r));
                                        goto finish;
                                }

                                k = process_driver(a, b, m);
                                if (k < 0) {
                                        r = k;
                                        log_error("Failed to process driver calls: %s", strerror(-r));
                                        goto finish;
                                }

                                if (k > 0)
                                        r = k;
                                else {
                                        k = sd_bus_send(a, m, NULL);
                                        if (k < 0) {
                                                if (k == -ECONNRESET)
                                                        r = 0;
                                                else {
                                                        r = k;
                                                        log_error("Failed to send message: %s", strerror(-r));
                                                }

                                                goto finish;
                                        }
                                }
                        }
                }

                if (r > 0)
                        continue;

                fd = sd_bus_get_fd(a);
                if (fd < 0) {
                        log_error("Failed to get fd: %s", strerror(-r));
                        goto finish;
                }

                events_a = sd_bus_get_events(a);
                if (events_a < 0) {
                        log_error("Failed to get events mask: %s", strerror(-r));
                        goto finish;
                }

                r = sd_bus_get_timeout(a, &timeout_a);
                if (r < 0) {
                        log_error("Failed to get timeout: %s", strerror(-r));
                        goto finish;
                }

                events_b = sd_bus_get_events(b);
                if (events_b < 0) {
                        log_error("Failed to get events mask: %s", strerror(-r));
                        goto finish;
                }

                r = sd_bus_get_timeout(b, &timeout_b);
                if (r < 0) {
                        log_error("Failed to get timeout: %s", strerror(-r));
                        goto finish;
                }

                t = timeout_a;
                if (t == (uint64_t) -1 || (timeout_b != (uint64_t) -1 && timeout_b < timeout_a))
                        t = timeout_b;

                if (t == (uint64_t) -1)
                        ts = NULL;
                else {
                        usec_t nw;

                        nw = now(CLOCK_MONOTONIC);
                        if (t > nw)
                                t -= nw;
                        else
                                t = 0;

                        ts = timespec_store(&_ts, t);
                }

                pollfd = (struct pollfd[3]) {
                        {.fd = fd,     .events = events_a,           },
                        {.fd = in_fd,  .events = events_b & POLLIN,  },
                        {.fd = out_fd, .events = events_b & POLLOUT, }
                };

                r = ppoll(pollfd, 3, ts, NULL);
                if (r < 0) {
                        log_error("ppoll() failed: %m");
                        goto finish;
                }
        }

finish:
        policy_free(&policy);
        strv_free(arg_configuration);
        free(arg_address);

        return r < 0 ? EXIT_FAILURE : EXIT_SUCCESS;
}