networkd: Change to a non-privileged user right away

[network.git] / src / networkd / main.c

/*#############################################################################
#                                                                             #
# IPFire.org - A linux based firewall                                         #
# Copyright (C) 2023 IPFire Network Development Team                          #
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# 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           #
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# This program is distributed in the hope that it will be useful,             #
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the               #
# GNU General Public License for more details.                                #
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# You should have received a copy of the GNU General Public License           #
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#############################################################################*/

#include <grp.h>
#include <pwd.h>
#include <stddef.h>
#include <sys/prctl.h>
#include <sys/types.h>
#include <unistd.h>

#include "daemon.h"
#include "logging.h"

static int drop_privileges(const char* user) {
	struct passwd* passwd = NULL;
	int r;

	// Fetch the current user
	uid_t current_uid = getuid();

	// If we have not been launched by root, we will assume that we have already
	// been launched with a minimal set of privileges.
	if (current_uid > 0)
		return 0;

	DEBUG("Dropping privileges...\n");

	// Fetch information about the desired user
	passwd = getpwnam(user);
	if (!passwd) {
		ERROR("Could not find user %s: %m\n", user);
		return 1;
	}

	uid_t uid = passwd->pw_uid;
	gid_t gid = passwd->pw_gid;

	// Change group
	r = setresgid(gid, gid, gid);
	if (r) {
		ERROR("Could not change group to %d: %m\n", gid);
		return 1;
	}

	// Set any supplementary groups
	r = setgroups(0, NULL);
	if (r) {
		ERROR("Could not set supplementary groups: %m\n");
		return 1;
	}

	// Do not drop any capabilities when we change to the new user
	r = prctl(PR_SET_KEEPCAPS, 1);
	if (r) {
		ERROR("Could not set PR_SET_KEEPCAPS: %m\n");
		return 1;
	}

	// Change to the new user
	r = setresuid(uid, uid, uid);
	if (r) {
		ERROR("Could not change user to %d: %m\n", uid);
		return 1;
	}

	// Reset PR_SET_KEEPCAPS
	r = prctl(PR_SET_KEEPCAPS, 0);
	if (r) {
		ERROR("Could not set PR_SET_KEEPCAPS: %m\n");
		return 1;
	}

	return 0;
}

int main(int argc, char** argv) {
	struct nw_daemon* daemon = NULL;
	int r;

	// Drop privileges
	r = drop_privileges("network");
	if (r)
		return r;

	// Create the daemon
	r = nw_daemon_create(&daemon);
	if (r)
		return r;

	// Run the daemon
	r = nw_daemon_run(daemon);

	// Cleanup
	if (daemon)
		nw_daemon_unref(daemon);

	return r;
}