141 lines
3.9 KiB
C++
141 lines
3.9 KiB
C++
// Copyright 2019 Google LLC
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// https://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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#include "sandboxed_api/embed_file.h"
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#include <fcntl.h>
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#include <sys/stat.h>
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#include <unistd.h>
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#include <string>
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#include "sandboxed_api/file_toc.h"
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#include "absl/strings/str_cat.h"
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#include "absl/synchronization/mutex.h"
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#include "sandboxed_api/sandbox2/util.h"
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#include "sandboxed_api/util/fileops.h"
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#include "sandboxed_api/util/raw_logging.h"
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namespace sapi {
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namespace {
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#ifndef F_ADD_SEALS
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#define F_ADD_SEALS 1033
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#define F_SEAL_SEAL 0x0001
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#define F_SEAL_SHRINK 0x0002
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#define F_SEAL_GROW 0x0004
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#define F_SEAL_WRITE 0x0008
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#endif
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bool SealFile(int fd) {
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constexpr int kMaxRetries = 10;
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for (int i = 0; i < kMaxRetries; ++i) {
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if (fcntl(fd, F_ADD_SEALS,
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F_SEAL_SEAL | F_SEAL_SHRINK | F_SEAL_GROW | F_SEAL_WRITE) == 0) {
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return true;
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}
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}
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return false;
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}
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} // namespace
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EmbedFile* EmbedFile::instance() {
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static auto* embed_file_instance = new EmbedFile();
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return embed_file_instance;
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}
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int EmbedFile::CreateFdForFileToc(const FileToc* toc) {
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// Create a memfd/temp file and write contents of the SAPI library to it.
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int fd = -1;
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if (!sandbox2::util::CreateMemFd(&fd, toc->name)) {
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SAPI_RAW_LOG(ERROR, "Couldn't create a temporary file for TOC name '%s'",
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toc->name);
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return -1;
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}
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file_util::fileops::FDCloser embed_fd(fd);
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if (!file_util::fileops::WriteToFD(embed_fd.get(), toc->data, toc->size)) {
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SAPI_RAW_PLOG(ERROR, "Couldn't write SAPI embed file '%s' to memfd file",
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toc->name);
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return -1;
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}
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// Make the underlying file non-writeable.
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if (fchmod(embed_fd.get(),
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S_IRUSR | S_IXUSR | S_IRGRP | S_IXGRP | S_IROTH | S_IXOTH) == -1) {
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SAPI_RAW_PLOG(ERROR, "Could't make FD=%d RX-only", embed_fd.get());
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return -1;
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}
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// Seal the file
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if (!SealFile(embed_fd.get())) {
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SAPI_RAW_PLOG(ERROR, "Couldn't apply file seals to FD=%d", embed_fd.get());
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return -1;
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}
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// Instead of working around problems with CRIU we reopen the file as
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// read-only.
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fd = open(absl::StrCat("/proc/", getpid(), "/fd/", embed_fd.get()).c_str(),
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O_RDONLY | O_CLOEXEC);
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if (fd == -1) {
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SAPI_RAW_PLOG(ERROR, "Couldn't reopen '%d' read-only through /proc",
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embed_fd.get());
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return -1;
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}
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return fd;
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}
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int EmbedFile::GetFdForFileToc(const FileToc* toc) {
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// Access to file_tocs_ must be guarded.
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absl::MutexLock lock{&file_tocs_mutex_};
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// If a file-descriptor for this toc already exists, just return it.
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auto entry = file_tocs_.find(toc);
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if (entry != file_tocs_.end()) {
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SAPI_RAW_VLOG(3,
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"Returning pre-existing embed file entry for '%s', fd: %d "
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"(orig name: '%s')",
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toc->name, entry->second, entry->first->name);
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return entry->second;
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}
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int embed_fd = CreateFdForFileToc(toc);
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if (embed_fd == -1) {
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SAPI_RAW_LOG(ERROR, "Cannot create a file for FileTOC: '%s'", toc->name);
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return -1;
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}
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SAPI_RAW_VLOG(1, "Created new embed file entry for '%s' with fd: %d",
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toc->name, embed_fd);
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file_tocs_[toc] = embed_fd;
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return embed_fd;
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}
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int EmbedFile::GetDupFdForFileToc(const FileToc* toc) {
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int fd = GetFdForFileToc(toc);
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if (fd == -1) {
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return -1;
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}
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fd = dup(fd);
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if (fd == -1) {
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SAPI_RAW_PLOG(ERROR, "dup failed");
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}
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return fd;
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}
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} // namespace sapi
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