blob: e994a01d5c181bae00d59a8f02a9e0c76c74a9e4 [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 <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/bpf_dsl/trap_registry.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_whitelist, write_whitelist);
// 2. CHECK(open_broker.Init(NULL));
// 3. Enable sandbox.
// 4. Use open_broker.Open() to open files.
class SANDBOX_EXPORT BrokerProcess {
// Handler to be used with a bpf_dsl Trap() function to forward system calls
// to the methods below.
static intptr_t SIGSYS_Handler(const arch_seccomp_data& args,
void* aux_broker_process);
// |denied_errno| is the error code returned when methods such as Open()
// or Access() are invoked on a file which is not in the whitelist (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 whitelisted 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,
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(const base::Callback<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;
// The following methods are used in place of the equivalently-named
// syscalls by the trap handler. They, in turn, forward the call onto
// |broker_client_| for further processing. They will all be async signal
// safe. They all return -errno on errors.
// Can be used in place of access().
// X_OK will always return an error in practice since the broker process
// doesn't support execute permissions.
int Access(const char* pathname, int mode) const;
// Can be used in place of mkdir().
int Mkdir(const char* path, int mode) const;
// Can be used in place of open()
// The implementation only supports certain white listed flags and will
// return -EPERM on other flags.
int Open(const char* pathname, int flags) const;
// Can be used in place of readlink().
int Readlink(const char* path, char* buf, size_t bufsize) const;
// Can be used in place of rename().
int Rename(const char* oldpath, const char* newpath) const;
// Can be used in place of rmdir().
int Rmdir(const char* path) const;
// Can be used in place of stat()/stat64()/lstat()/lstat64().
int Stat(const char* pathname, bool follow_links, struct stat* sb) const;
int Stat64(const char* pathname, bool follow_links, struct stat64* sb) const;
// Can be used in place of unlink().
int Unlink(const char* path) const;
friend class BrokerProcessTestHelper;
// Close the IPC channel with the other party. This should only be used
// by tests an none of the class methods should be used afterwards.
void CloseChannel();
bool initialized_; // Whether we've been through Init() yet.
pid_t broker_pid_; // The PID of the broker (child) created in Init().
const bool fast_check_in_client_;
const bool quiet_failures_for_tests_;
syscall_broker::BrokerCommandSet allowed_command_set_;
broker_permission_list_; // File access whitelist.
std::unique_ptr<syscall_broker::BrokerClient> broker_client_;
} // namespace syscall_broker
} // namespace sandbox