blob: 3cd01bceda9e43c4a213165c2666e59e543f38e9 [file] [log] [blame]
// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include <sys/stat.h>
#include <memory>
#include <string>
#include <vector>
#include "base/callback_forward.h"
#include "base/macros.h"
#include "base/pickle.h"
#include "base/process/process.h"
#include "sandbox/linux/syscall_broker/broker_command.h"
#include "sandbox/linux/syscall_broker/broker_permission_list.h"
#include "sandbox/sandbox_export.h"
namespace sandbox {
namespace syscall_broker {
class BrokerClient;
class BrokerFilePermission;
// Create a new "broker" process to which we can send requests via an IPC
// channel by forking the current process.
// This is a low level IPC mechanism that is suitable to be called from a
// signal handler.
// A process would typically create a broker process before entering
// sandboxing.
// 1. BrokerProcess open_broker(read_allowlist, write_allowlist);
// 2. CHECK(open_broker.Init(NULL));
// 3. Enable sandbox.
// 4. Use open_broker.Open() to open files.
class SANDBOX_EXPORT BrokerProcess {
enum class BrokerType { SIGNAL_BASED };
// |denied_errno| is the error code returned when methods such as Open()
// or Access() are invoked on a file which is not in the allowlist (EACCESS
// would be a typical value). |allowed_command_mask| is a bitwise-or of
// kBrokerCommand*Mask constants from broker_command.h that further restrict
// the syscalls to execute. |permissions| describes the allowlisted set
// of files the broker is is allowed to access. |fast_check_in_client|
// controls whether doomed requests are first filtered on the client side
// before being proxied. Apart from tests, this should always be true since
// our main clients are not always well-behaved. They may have third party
// libraries that don't know about sandboxing, and typically try to open all
// sorts of stuff they don't really need. It's important to reduce this load
// given that there is only one pipeline to the broker process, and it is
// not multi-threaded. |quiet_failures_for_tests| is reserved for unit tests,
// don't use it.
int denied_errno,
const syscall_broker::BrokerCommandSet& allowed_command_set,
const std::vector<syscall_broker::BrokerFilePermission>& permissions,
BrokerType broker_type,
bool fast_check_in_client = true,
bool quiet_failures_for_tests = false);
// Will initialize the broker process. There should be no threads at this
// point, since we need to fork().
// broker_process_init_callback will be called in the new broker process,
// after fork() returns.
bool Init(base::OnceCallback<bool(void)> broker_process_init_callback);
// Return the PID of the child created by Init().
int broker_pid() const { return broker_pid_; }
// Can be used in bpf_dsl::Policy::EvaluateSyscall() implementations to
// determine if the system call |sysno| should be trapped and forwarded
// to the broker process for handling. This examines the
// |allowed_command_set_| iff |fast_check_in_client_| is true. If
// the fast checks are disabled, then all possible brokerable system
// calls are forwarded to the broker process for handling.
bool IsSyscallAllowed(int sysno) const;
// Gets the signal-based BrokerClient created by Init().
syscall_broker::BrokerClient* GetBrokerClientSignalBased() const {
return broker_client_.get();
friend class BrokerProcessTestHelper;
friend class HandleFilesystemViaBrokerPolicy;
// IsSyscallBrokerable() answers the same question as IsSyscallAllowed(),
// but takes |fast_check| as a parameter. If |fast_check| is false, do not
// check |allowed_command_set_| before returning true for a syscall that is
// brokerable.
bool IsSyscallBrokerable(int sysno, bool fast_check) const;
// Close the IPC channel with the other party. This should only be used
// by tests and none of the class methods should be used afterwards.
void CloseChannel();
// Forks the signal-based broker, where syscall emulation is performed using
// signals in the sandboxed process that connect to the broker via Unix
// socket.
bool ForkSignalBasedBroker(
base::OnceCallback<bool(void)> broker_process_init_callback);
bool initialized_; // Whether we've been through Init() yet.
pid_t broker_pid_; // The PID of the broker (child) created in Init().
const BrokerType broker_type_;
const bool fast_check_in_client_;
const bool quiet_failures_for_tests_;
syscall_broker::BrokerCommandSet allowed_command_set_;
broker_permission_list_; // File access allowlist.
std::unique_ptr<syscall_broker::BrokerClient> broker_client_;
} // namespace syscall_broker
} // namespace sandbox