sandboxed-api/sandboxed_api/sandbox2/executor.cc

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// Copyright 2019 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
// Implementation of the sandbox2::Executor class
#include "sandboxed_api/sandbox2/executor.h"
#include <fcntl.h>
#include <libgen.h>
#include <sys/socket.h>
#include <unistd.h>
#include <climits>
#include <cstddef>
#include <string_view>
#include "absl/memory/memory.h"
#include "absl/status/status.h"
#include "absl/strings/match.h"
#include "absl/strings/str_cat.h"
#include "absl/strings/string_view.h"
#include "sandboxed_api/config.h"
#include "sandboxed_api/sandbox2/fork_client.h"
#include "sandboxed_api/sandbox2/forkserver.pb.h"
#include "sandboxed_api/sandbox2/global_forkclient.h"
#include "sandboxed_api/sandbox2/ipc.h"
#include "sandboxed_api/sandbox2/util.h"
#include "sandboxed_api/util/fileops.h"
namespace sandbox2 {
namespace file_util = ::sapi::file_util;
namespace {
void DisableCompressStackDepot(ForkRequest& request) {
auto disable_compress_stack_depot = [&request](absl::string_view sanitizer) {
auto prefix = absl::StrCat(sanitizer, "_OPTIONS=");
auto it = std::find_if(request.mutable_envs()->begin(),
request.mutable_envs()->end(),
[&prefix](const std::string& env) {
return absl::StartsWith(env, prefix);
});
constexpr absl::string_view option = "compress_stack_depot=0";
if (it != request.mutable_envs()->end()) {
// If it's already there, the last value will be used.
absl::StrAppend(&*it, ":", option);
return;
}
request.add_envs(absl::StrCat(prefix, option));
};
if constexpr (sapi::sanitizers::IsASan()) {
disable_compress_stack_depot("ASAN");
}
if constexpr (sapi::sanitizers::IsMSan()) {
disable_compress_stack_depot("MSAN");
}
if constexpr (sapi::sanitizers::IsLSan()) {
disable_compress_stack_depot("LSAN");
}
if constexpr (sapi::sanitizers::IsHwASan()) {
disable_compress_stack_depot("HWSAN");
}
if constexpr (sapi::sanitizers::IsTSan()) {
disable_compress_stack_depot("TSAN");
}
}
} // namespace
std::vector<std::string> Executor::CopyEnviron() {
return util::CharPtrArray(environ).ToStringVector();
}
absl::StatusOr<Executor::Process> Executor::StartSubProcess(
int32_t clone_flags, const Namespace* ns, const std::vector<int>& caps) {
if (started_) {
return absl::FailedPreconditionError(
"This executor has already been started");
}
if (!path_.empty()) {
exec_fd_ = file_util::fileops::FDCloser(open(path_.c_str(), O_PATH));
if (exec_fd_.get() < 0) {
if (errno == ENOENT) {
return absl::ErrnoToStatus(errno, path_);
}
return absl::ErrnoToStatus(errno,
absl::StrCat("Could not open file ", path_));
}
}
if (libunwind_sbox_for_pid_ != 0) {
VLOG(1) << "StartSubProcces, starting libunwind";
} else if (exec_fd_.get() < 0) {
VLOG(1) << "StartSubProcess, with [Fork-Server]";
} else if (!path_.empty()) {
VLOG(1) << "StartSubProcess, with file " << path_;
} else {
VLOG(1) << "StartSubProcess, with fd " << exec_fd_.get();
}
ForkRequest request;
*request.mutable_args() = {argv_.begin(), argv_.end()};
*request.mutable_envs() = {envp_.begin(), envp_.end()};
// Add LD_ORIGIN_PATH to envs, as it'll make the amount of syscalls invoked by
// ld.so smaller.
if (!path_.empty()) {
request.add_envs(absl::StrCat("LD_ORIGIN_PATH=",
file_util::fileops::StripBasename(path_)));
}
// Disable optimization to avoid related syscalls.
if constexpr (sapi::sanitizers::IsAny()) {
DisableCompressStackDepot(request);
}
// If neither the path, nor exec_fd is specified, just assume that we need to
// send a fork request.
//
// Otherwise, it's either sandboxing pre- or post-execve with the global
// Fork-Server.
if (libunwind_sbox_for_pid_ != 0) {
request.set_mode(FORKSERVER_FORK_JOIN_SANDBOX_UNWIND);
} else if (exec_fd_.get() == -1) {
request.set_mode(FORKSERVER_FORK);
} else if (enable_sandboxing_pre_execve_) {
request.set_mode(FORKSERVER_FORK_EXECVE_SANDBOX);
} else {
request.set_mode(FORKSERVER_FORK_EXECVE);
}
if (ns) {
clone_flags |= ns->GetCloneFlags();
*request.mutable_mount_tree() = ns->mounts().GetMountTree();
request.set_hostname(ns->hostname());
request.set_allow_mount_propagation(ns->allow_mount_propagation());
}
request.set_clone_flags(clone_flags);
for (auto cap : caps) {
request.add_capabilities(cap);
}
file_util::fileops::FDCloser ns_fd;
if (libunwind_sbox_for_pid_ != 0) {
const std::string ns_path =
absl::StrCat("/proc/", libunwind_sbox_for_pid_, "/ns/user");
ns_fd = file_util::fileops::FDCloser(open(ns_path.c_str(), O_RDONLY));
if (ns_fd.get() == -1) {
return absl::ErrnoToStatus(
errno, absl::StrCat("Could not open user ns fd (", ns_path, ")"));
}
}
Process process;
if (fork_client_) {
process.main_pid = fork_client_->SendRequest(
request, exec_fd_.get(), client_comms_fd_.get(), ns_fd.get(),
&process.init_pid);
} else {
process.main_pid = GlobalForkClient::SendRequest(
request, exec_fd_.get(), client_comms_fd_.get(), ns_fd.get(),
&process.init_pid);
}
started_ = true;
client_comms_fd_.Close();
exec_fd_.Close();
VLOG(1) << "StartSubProcess returned with: " << process.main_pid;
return process;
}
std::unique_ptr<ForkClient> Executor::StartForkServer() {
// This flag is set explicitly to 'true' during object instantiation, and
// custom fork-servers should never be sandboxed.
set_enable_sandbox_before_exec(false);
absl::StatusOr<Process> process = StartSubProcess(0);
if (!process.ok()) {
return nullptr;
}
return absl::make_unique<ForkClient>(process->main_pid, ipc_.comms());
}
void Executor::SetUpServerSideCommsFd() {
int sv[2];
if (socketpair(AF_UNIX, SOCK_STREAM, 0, sv) == -1) {
PLOG(FATAL) << "socketpair(AF_UNIX, SOCK_STREAM) failed";
}
client_comms_fd_ = file_util::fileops::FDCloser(sv[0]);
ipc_.SetUpServerSideComms(sv[1]);
}
} // namespace sandbox2