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// Copyright 2015 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef SANDBOX_LINUX_SERVICES_NAMESPACE_SANDBOX_H_
#define SANDBOX_LINUX_SERVICES_NAMESPACE_SANDBOX_H_
#include <sys/types.h>
#include <string>
#include <vector>
#include "base/command_line.h"
#include "base/process/launch.h"
#include "base/process/process.h"
#include "sandbox/sandbox_export.h"
namespace sandbox {
// Helper class for starting a process inside a new user, PID, and network
// namespace. Before using a namespace sandbox, check for namespaces support
// using Credentials::CanCreateProcessInNewUserNS.
//
// A typical use for "A" launching a sandboxed process "B" would be:
// 1. A sets up a command line and launch options for process B.
// 2. A launches B with LaunchProcess.
// 3. B should be prepared to assume the role of init(1). In particular, apart
// from SIGKILL and SIGSTOP, B cannot receive any signal for which it does
// not have an explicit signal handler registered.
// If B dies, all the processes in the namespace will die.
// B can fork() and the parent can assume the role of init(1), by using
// CreateInitProcessReaper().
// 4. B chroots using Credentials::MoveToNewUserNS() and
// Credentials::DropFileSystemAccess()
// 5. B drops capabilities gained by entering the new user namespace with
// Credentials::DropAllCapabilities().
class SANDBOX_EXPORT NamespaceSandbox {
public:
struct Options {
Options();
~Options();
// Bitmask of namespace types. Must be some combination of CLONE_NEWUSER
// (required), CLONE_NEWPID, and CLONE_NEWNET. Defaults to all of the above.
int ns_types;
// Fail if any of the namespace types are not supported. Defaults to false.
bool fail_on_unsupported_ns_type;
};
NamespaceSandbox() = delete;
NamespaceSandbox(const NamespaceSandbox&) = delete;
NamespaceSandbox& operator=(const NamespaceSandbox&) = delete;
// Launch a new process inside its own user/PID/network namespaces (depending
// on kernel support). Requires at a minimum that user namespaces are
// supported (use Credentials::CanCreateProcessInNewUserNS to check this).
//
// pre_exec_delegate and clone_flags fields of LaunchOptions should be nullptr
// and 0, respectively, since this function makes a copy of options and
// overrides them.
static base::Process LaunchProcess(const base::CommandLine& cmdline,
const base::LaunchOptions& launch_options);
static base::Process LaunchProcess(const std::vector<std::string>& argv,
const base::LaunchOptions& launch_options);
// Versions which take namespace sandbox options. These allow fine grained
// control over the types of namespaces used.
static base::Process LaunchProcessWithOptions(
const base::CommandLine& cmdline,
const base::LaunchOptions& launch_options,
const Options& ns_sandbox_options);
static base::Process LaunchProcessWithOptions(
const std::vector<std::string>& argv,
const base::LaunchOptions& launch_options,
const Options& ns_sandbox_options);
// Forks a process in its own PID namespace. The child process is the init
// process inside of the PID namespace, so if the child needs to fork further,
// it should call CreateInitProcessReaper, which turns the init process into a
// reaper process.
//
// Otherwise, the child should setup handlers for signals which should
// terminate the process using InstallDefaultTerminationSignalHandlers or
// InstallTerminationSignalHandler. This works around the fact that init
// processes ignore such signals unless they have an explicit handler set.
//
// This function requries CAP_SYS_ADMIN. If |drop_capabilities_in_child| is
// true, then capabilities are dropped in the child.
static pid_t ForkInNewPidNamespace(bool drop_capabilities_in_child);
// Installs a signal handler for:
//
// SIGHUP, SIGINT, SIGABRT, SIGQUIT, SIGPIPE, SIGTERM, SIGUSR1, SIGUSR2
//
// that exits with SignalExitCode(sig). These are signals whose default action
// is to terminate the program (apart from SIGILL, SIGFPE, and SIGSEGV, which
// will still terminate the process if e.g. an illegal instruction is
// encountered, etc.).
//
// If any of these already had a signal handler installed, this function will
// not override them.
static void InstallDefaultTerminationSignalHandlers();
// Installs a signal handler for |sig| which exits with |exit_code|. If a
// signal handler was already present for |sig|, does nothing and returns
// false.
static bool InstallTerminationSignalHandler(int sig, int exit_code);
// Returns an exit code corresponding to the process being killed by sig. This
// is the same as exit code that NaCl's default signal handler uses.
static int SignalExitCode(int sig) { return -sig & 0xff; }
// Returns whether the namespace sandbox created a new user, PID, and network
// namespace. In particular, InNewUserNamespace should return true iff the
// process was started via this class.
static bool InNewUserNamespace();
static bool InNewPidNamespace();
static bool InNewNetNamespace();
};
} // namespace sandbox
#endif // SANDBOX_LINUX_SERVICES_NAMESPACE_SANDBOX_H_
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