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// Copyright 2015 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 "sandbox/linux/services/namespace_sandbox.h"
#include <sched.h>
#include <signal.h>
#include <stdlib.h>
#include <sys/types.h>
#include <unistd.h>
#include <string>
#include <utility>
#include <vector>
#include "base/command_line.h"
#include "base/environment.h"
#include "base/files/scoped_file.h"
#include "base/logging.h"
#include "base/macros.h"
#include "base/posix/eintr_wrapper.h"
#include "base/process/launch.h"
#include "base/process/process.h"
#include "sandbox/linux/services/credentials.h"
#include "sandbox/linux/services/namespace_utils.h"
namespace sandbox {
namespace {
const char kSandboxUSERNSEnvironmentVarName[] = "SBX_USER_NS";
const char kSandboxPIDNSEnvironmentVarName[] = "SBX_PID_NS";
const char kSandboxNETNSEnvironmentVarName[] = "SBX_NET_NS";
#if !defined(OS_NACL_NONSFI)
class WriteUidGidMapDelegate : public base::LaunchOptions::PreExecDelegate {
public:
WriteUidGidMapDelegate()
: uid_(getuid()),
gid_(getgid()),
supports_deny_setgroups_(
NamespaceUtils::KernelSupportsDenySetgroups()) {}
~WriteUidGidMapDelegate() override {}
void RunAsyncSafe() override {
if (supports_deny_setgroups_) {
RAW_CHECK(NamespaceUtils::DenySetgroups());
}
RAW_CHECK(NamespaceUtils::WriteToIdMapFile("/proc/self/uid_map", uid_));
RAW_CHECK(NamespaceUtils::WriteToIdMapFile("/proc/self/gid_map", gid_));
}
private:
const uid_t uid_;
const gid_t gid_;
const bool supports_deny_setgroups_;
DISALLOW_COPY_AND_ASSIGN(WriteUidGidMapDelegate);
};
void SetEnvironForNamespaceType(base::EnvironmentMap* environ,
base::NativeEnvironmentString env_var,
bool value) {
// An empty string causes the env var to be unset in the child process.
(*environ)[env_var] = value ? "1" : "";
}
// Linux supports up to 64 signals. This should be updated if that ever changes.
int g_signal_exit_codes[64];
void TerminationSignalHandler(int sig) {
// Return a special exit code so that the process is detected as terminated by
// a signal.
const size_t sig_idx = static_cast<size_t>(sig);
if (sig_idx < arraysize(g_signal_exit_codes)) {
_exit(g_signal_exit_codes[sig_idx]);
}
_exit(NamespaceSandbox::kDefaultExitCode);
}
#endif // !defined(OS_NACL_NONSFI)
} // namespace
#if !defined(OS_NACL_NONSFI)
// static
base::Process NamespaceSandbox::LaunchProcess(
const base::CommandLine& cmdline,
const base::LaunchOptions& options) {
return LaunchProcess(cmdline.argv(), options);
}
// static
base::Process NamespaceSandbox::LaunchProcess(
const std::vector<std::string>& argv,
const base::LaunchOptions& options) {
int clone_flags = 0;
int ns_types[] = {CLONE_NEWUSER, CLONE_NEWPID, CLONE_NEWNET};
for (const int ns_type : ns_types) {
if (NamespaceUtils::KernelSupportsUnprivilegedNamespace(ns_type)) {
clone_flags |= ns_type;
}
}
CHECK(clone_flags & CLONE_NEWUSER);
// These fields may not be set by the caller.
CHECK(options.pre_exec_delegate == nullptr);
CHECK_EQ(0, options.clone_flags);
WriteUidGidMapDelegate write_uid_gid_map_delegate;
base::LaunchOptions launch_options = options;
launch_options.pre_exec_delegate = &write_uid_gid_map_delegate;
launch_options.clone_flags = clone_flags;
const std::pair<int, const char*> clone_flag_environ[] = {
std::make_pair(CLONE_NEWUSER, kSandboxUSERNSEnvironmentVarName),
std::make_pair(CLONE_NEWPID, kSandboxPIDNSEnvironmentVarName),
std::make_pair(CLONE_NEWNET, kSandboxNETNSEnvironmentVarName),
};
base::EnvironmentMap* environ = &launch_options.environ;
for (const auto& entry : clone_flag_environ) {
const int flag = entry.first;
const char* environ_name = entry.second;
SetEnvironForNamespaceType(environ, environ_name, clone_flags & flag);
}
return base::LaunchProcess(argv, launch_options);
}
// static
pid_t NamespaceSandbox::ForkInNewPidNamespace(bool drop_capabilities_in_child) {
const pid_t pid =
base::ForkWithFlags(CLONE_NEWPID | SIGCHLD, nullptr, nullptr);
if (pid < 0) {
return pid;
}
if (pid == 0) {
DCHECK_EQ(1, getpid());
if (drop_capabilities_in_child) {
// Since we just forked, we are single-threaded, so this should be safe.
CHECK(Credentials::DropAllCapabilitiesOnCurrentThread());
}
return 0;
}
return pid;
}
// static
void NamespaceSandbox::InstallDefaultTerminationSignalHandlers() {
static const int kDefaultTermSignals[] = {
SIGHUP, SIGINT, SIGABRT, SIGQUIT, SIGPIPE, SIGTERM, SIGUSR1, SIGUSR2,
};
for (const int sig : kDefaultTermSignals) {
InstallTerminationSignalHandler(sig, kDefaultExitCode);
}
}
// static
bool NamespaceSandbox::InstallTerminationSignalHandler(
int sig,
int exit_code) {
struct sigaction old_action;
PCHECK(sigaction(sig, nullptr, &old_action) == 0);
if (old_action.sa_flags & SA_SIGINFO &&
old_action.sa_sigaction != nullptr) {
return false;
} else if (old_action.sa_handler != SIG_DFL) {
return false;
}
const size_t sig_idx = static_cast<size_t>(sig);
CHECK_LT(sig_idx, arraysize(g_signal_exit_codes));
DCHECK_GE(exit_code, 0);
DCHECK_LT(exit_code, 256);
g_signal_exit_codes[sig_idx] = exit_code;
struct sigaction action = {};
action.sa_handler = &TerminationSignalHandler;
PCHECK(sigaction(sig, &action, nullptr) == 0);
return true;
}
#endif // !defined(OS_NACL_NONSFI)
// static
bool NamespaceSandbox::InNewUserNamespace() {
return getenv(kSandboxUSERNSEnvironmentVarName) != nullptr;
}
// static
bool NamespaceSandbox::InNewPidNamespace() {
return getenv(kSandboxPIDNSEnvironmentVarName) != nullptr;
}
// static
bool NamespaceSandbox::InNewNetNamespace() {
return getenv(kSandboxNETNSEnvironmentVarName) != nullptr;
}
} // namespace sandbox
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