sendreply.c

/*
    Copyright (C) 2020 Martin Sandsmark

    This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.

    This program 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 General Public License for more details.

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

#include <systemd/sd-bus.h>
#include <systemd/sd-journal.h>
#include <unistd.h>
#include <stdlib.h>
#include <errno.h>

int main(int argc, char *argv[])
{
    if (argc != 3) {
        sd_journal_print(LOG_ERR, "Invalid args passed, need cookie and authed ID");
        return EPERM;
    }

    if (getuid()) {
        sd_journal_print(LOG_ERR, "warning: This needs to run as root");
        return EPERM;
    }

    sd_bus *bus = NULL;
    int ret = sd_bus_open_system(&bus);
    if (ret < 0) {
        sd_journal_print(LOG_ERR, "Failed to connect to system bus: %s", strerror(-ret));
        return -ret;
    }

    sd_journal_print(LOG_NOTICE, "Responding, cookie: %s, authed uid: %d\n", argv[1], atoi(argv[2]));

    sd_bus_error error = SD_BUS_ERROR_NULL;
    sd_bus_message *dbusRet = NULL;
    ret = sd_bus_call_method(bus,
                    "org.freedesktop.PolicyKit1",            /* service to contact */
                    "/org/freedesktop/PolicyKit1/Authority", /* object path */
                    "org.freedesktop.PolicyKit1.Authority",  /* interface name */
                    "AuthenticationAgentResponse2",          /* method name */
                    &error,                                  /* object to return error in */
                    &dbusRet,                                /* return message on success */
                    "us(sa{sv})",                            /* input signature */

                    // arguments
                    atoi(argv[2]), /* UID of our parent/user that su-ed, should always be the same as authed */
                    argv[1],       /* cookie */
                    "unix-user",   /* map key name ID type (UID) */
                    1,             /* number of elements in a(rray), actually a map, describing unix-user */
                    "uid",         /* the key for the entry in the map */
                    "u",           /* map value v(ariant)'s real type */
                    atoi(argv[2])  /* authed UID */
                    );

    if (ret < 0) {
        sd_journal_print(LOG_ERR, "Failed to issue method call: %s (%s, %s)\n", error.message, strerror(errno), strerror(-ret));
    }

    sd_bus_error_free(&error);
    sd_bus_message_unref(dbusRet);
    sd_bus_unref(bus);

    return -ret; /* systemd flips the sign */
}