qswiki/sandbox/sandbox-linux.cpp

#include <vector>
#include <initializer_list>
#include <string.h>
#include <sched.h>
#include <unistd.h>
#include <fstream>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <string.h>
#include <filesystem>
#include <sys/mount.h>
#include <sys/capability.h>
#include <qssb.h>
#include "../logger.h"
#include "../utils.h"
#include "../random.h"

#include "sandbox-linux.h"

/* TODO: make a whitelist approach. So far we simply blacklist
 * obvious systemcalls. To whitelist, we need to analyse our
 * dependencies (http library, sqlite wrapper, sqlite lib etc.) */

bool SandboxLinux::enableForInit()
{
	umask(0027);
	struct qssb_policy policy = {0};
	int blacklisted_syscalls[] = {QSSB_SYS(execveat), QSSB_SYS(execve), -1};
	policy.blacklisted_syscalls = blacklisted_syscalls;
	policy.no_new_privs = 1;
	int result = qssb_enable_policy(&policy);
	if(result != 0)
	{
		Logger::error() << "Failed to install sandboxing policy (init): " << result;
		return false;
	}
	return true;
}

bool SandboxLinux::enablePreWorker(std::vector<std::string> fsPaths)
{
	std::sort(fsPaths.begin(), fsPaths.end(),
			  [](const std::string &a, const std::string &b) { return a.length() < b.length(); });

	struct qssb_path_policy *policies = new qssb_path_policy[fsPaths.size()];
	for(unsigned int i = 0; i < fsPaths.size(); i++)
	{
		policies[i].next = policies + (i + 1);
		policies[i].mountpoint = fsPaths[i].c_str();
		policies[i].policy = QSSB_MOUNT_ALLOW_READ | QSSB_MOUNT_ALLOW_WRITE;
	}
	policies[fsPaths.size() - 1].next = NULL;

	struct qssb_policy policy = {0};
	policy.path_policies = policies;
	policy.namespace_options |= QSSB_UNSHARE_MOUNT;
	policy.namespace_options |= QSSB_UNSHARE_USER;
	int blacklisted_syscalls[] = {QSSB_SYS(execveat), QSSB_SYS(execve), -1};
	policy.blacklisted_syscalls = blacklisted_syscalls;
	int result = qssb_enable_policy(&policy);
	if(result != 0)
	{
		Logger::error() << "Failed to install sandboxing policy (preworker): %i" << result;
		return false;
	}
	delete[] policies;
	return true;
}

bool SandboxLinux::supported()
{
	std::fstream stream;
	stream.open("/proc/sys/kernel/unprivileged_userns_clone");
	if(stream.is_open())
	{
		std::string str;
		stream >> str;
		if(str[0] == '0')
		{
			Logger::error() << "Please write '1' to /proc/sys/kernel/unprivileged_userns_clone in order to enable "
							   "sandboxing support on this system";
			return false;
		}
	}
	return true;
}
bool SandboxLinux::enableForWorker()
{
	struct qssb_policy policy = {0};
	policy.drop_caps = 1;
	policy.not_dumpable = 1;
	policy.no_new_privs = 1;

	/* TODO: as said, a whitelist approach is better. As such, this list is bound to be incomplete in the
	 * sense that more could be listed here and some critical ones are probably missing */
	int blacklisted_syscalls[] = {QSSB_SYS(setuid),
								  QSSB_SYS(connect),
								  QSSB_SYS(chroot),
								  QSSB_SYS(pivot_root),
								  QSSB_SYS(mount),
								  QSSB_SYS(setns),
								  QSSB_SYS(unshare),
								  QSSB_SYS(ptrace),
								  QSSB_SYS(personality),
								  QSSB_SYS(prctl),
								  -1};
	policy.blacklisted_syscalls = blacklisted_syscalls;
	if(qssb_enable_policy(&policy) != 0)
	{
		Logger::error() << "Sandbox: Activation of seccomp blacklist failed!";
		return false;
	}

	return true;
}