| // 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 |