// Copyright 2014 The Chromium OS Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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#include "brillo/file_utils.h"
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#include <fcntl.h>
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#include <unistd.h>
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#include <base/files/file_path.h>
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#include <base/files/file_util.h>
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#include <base/files/scoped_file.h>
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#include <base/logging.h>
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#include <base/posix/eintr_wrapper.h>
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#include <base/rand_util.h>
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#include <base/strings/string_number_conversions.h>
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#include <base/time/time.h>
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namespace brillo {
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namespace {
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// Log sync(), fsync(), etc. calls that take this many seconds or longer.
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constexpr const base::TimeDelta kLongSync = base::TimeDelta::FromSeconds(10);
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enum {
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kPermissions600 = S_IRUSR | S_IWUSR,
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kPermissions777 = S_IRWXU | S_IRWXG | S_IRWXO
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};
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// Verify that base file permission enums are compatible with S_Ixxx. If these
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// asserts ever fail, we'll need to ensure that users of these functions switch
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// away from using base permission enums and add a note to the function comments
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// indicating that base enums can not be used.
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static_assert(base::FILE_PERMISSION_READ_BY_USER == S_IRUSR,
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"base file permissions don't match unistd.h permissions");
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static_assert(base::FILE_PERMISSION_WRITE_BY_USER == S_IWUSR,
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"base file permissions don't match unistd.h permissions");
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static_assert(base::FILE_PERMISSION_EXECUTE_BY_USER == S_IXUSR,
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"base file permissions don't match unistd.h permissions");
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static_assert(base::FILE_PERMISSION_READ_BY_GROUP == S_IRGRP,
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"base file permissions don't match unistd.h permissions");
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static_assert(base::FILE_PERMISSION_WRITE_BY_GROUP == S_IWGRP,
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"base file permissions don't match unistd.h permissions");
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static_assert(base::FILE_PERMISSION_EXECUTE_BY_GROUP == S_IXGRP,
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"base file permissions don't match unistd.h permissions");
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static_assert(base::FILE_PERMISSION_READ_BY_OTHERS == S_IROTH,
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"base file permissions don't match unistd.h permissions");
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static_assert(base::FILE_PERMISSION_WRITE_BY_OTHERS == S_IWOTH,
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"base file permissions don't match unistd.h permissions");
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static_assert(base::FILE_PERMISSION_EXECUTE_BY_OTHERS == S_IXOTH,
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"base file permissions don't match unistd.h permissions");
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enum RegularFileOrDeleteResult {
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kFailure = 0, // Failed to delete whatever was at the path.
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kRegularFile = 1, // Regular file existed and was unchanged.
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kEmpty = 2 // Anything that was at the path has been deleted.
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};
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// Checks if a regular file owned by |uid| and |gid| exists at |path|, otherwise
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// deletes anything that might be at |path|. Returns a RegularFileOrDeleteResult
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// enum indicating what is at |path| after the function finishes.
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RegularFileOrDeleteResult RegularFileOrDelete(const base::FilePath& path,
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uid_t uid,
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gid_t gid) {
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// Check for symlinks by setting O_NOFOLLOW and checking for ELOOP. This lets
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// us use the safer fstat() instead of having to use lstat().
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base::ScopedFD scoped_fd(HANDLE_EINTR(openat(
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AT_FDCWD, path.value().c_str(), O_RDONLY | O_CLOEXEC | O_NOFOLLOW)));
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bool path_not_empty = (errno == ELOOP || scoped_fd != -1);
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// If there is a file/directory at |path|, see if it matches our criteria.
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if (scoped_fd != -1) {
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struct stat file_stat;
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if (fstat(scoped_fd.get(), &file_stat) != -1 &&
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S_ISREG(file_stat.st_mode) && file_stat.st_uid == uid &&
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file_stat.st_gid == gid) {
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return kRegularFile;
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}
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}
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// If we get here and anything was at |path|, try to delete it so we can put
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// our file there.
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if (path_not_empty) {
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if (!base::DeleteFile(path, true)) {
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PLOG(WARNING) << "Failed to delete entity at \"" << path.value() << '"';
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return kFailure;
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}
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}
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return kEmpty;
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}
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// Handles common touch functionality but also provides an optional |fd_out|
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// so that any further modifications to the file (e.g. permissions) can safely
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// use the fd rather than the path. |fd_out| will only be set if a new file
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// is created, otherwise it will be unchanged.
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// If |fd_out| is null, this function will close the file, otherwise it's
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// expected that |fd_out| will close the file when it goes out of scope.
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bool TouchFileInternal(const base::FilePath& path,
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uid_t uid,
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gid_t gid,
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base::ScopedFD* fd_out) {
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RegularFileOrDeleteResult result = RegularFileOrDelete(path, uid, gid);
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switch (result) {
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case kFailure:
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return false;
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case kRegularFile:
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return true;
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case kEmpty:
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break;
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}
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// base::CreateDirectory() returns true if the directory already existed.
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if (!base::CreateDirectory(path.DirName())) {
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PLOG(WARNING) << "Failed to create directory for \"" << path.value() << '"';
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return false;
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}
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// Create the file as owner-only initially.
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base::ScopedFD scoped_fd(HANDLE_EINTR(openat(
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AT_FDCWD, path.value().c_str(),
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O_RDONLY | O_NOFOLLOW | O_CREAT | O_EXCL | O_CLOEXEC, kPermissions600)));
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if (scoped_fd == -1) {
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PLOG(WARNING) << "Failed to create file \"" << path.value() << '"';
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return false;
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}
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if (fd_out) {
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fd_out->swap(scoped_fd);
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}
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return true;
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}
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std::string GetRandomSuffix() {
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const int kBufferSize = 6;
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unsigned char buffer[kBufferSize];
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base::RandBytes(buffer, arraysize(buffer));
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std::string suffix;
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for (int i = 0; i < kBufferSize; ++i) {
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int random_value = buffer[i] % (2 * 26 + 10);
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if (random_value < 26) {
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suffix.push_back('a' + random_value);
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} else if (random_value < 2 * 26) {
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suffix.push_back('A' + random_value - 26);
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} else {
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suffix.push_back('0' + random_value - 2 * 26);
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}
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}
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return suffix;
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}
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} // namespace
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bool TouchFile(const base::FilePath& path,
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int new_file_permissions,
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uid_t uid,
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gid_t gid) {
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// Make sure |permissions| doesn't have any out-of-range bits.
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if (new_file_permissions & ~kPermissions777) {
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LOG(WARNING) << "Illegal permissions: " << new_file_permissions;
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return false;
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}
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base::ScopedFD scoped_fd;
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if (!TouchFileInternal(path, uid, gid, &scoped_fd)) {
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return false;
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}
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// scoped_fd is valid only if a new file was created.
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if (scoped_fd != -1 &&
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HANDLE_EINTR(fchmod(scoped_fd.get(), new_file_permissions)) == -1) {
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PLOG(WARNING) << "Failed to set permissions for \"" << path.value() << '"';
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base::DeleteFile(path, false);
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return false;
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}
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return true;
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}
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bool TouchFile(const base::FilePath& path) {
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// Use TouchFile() instead of TouchFileInternal() to explicitly set
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// permissions to 600 in case umask is set strangely.
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return TouchFile(path, kPermissions600, geteuid(), getegid());
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}
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bool WriteBlobToFile(const base::FilePath& path, const Blob& blob) {
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return WriteToFile(path, reinterpret_cast<const char*>(blob.data()),
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blob.size());
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}
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bool WriteStringToFile(const base::FilePath& path, const std::string& data) {
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return WriteToFile(path, data.data(), data.size());
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}
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bool WriteToFile(const base::FilePath& path, const char* data, size_t size) {
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if (!base::DirectoryExists(path.DirName())) {
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if (!base::CreateDirectory(path.DirName())) {
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LOG(ERROR) << "Cannot create directory: " << path.DirName().value();
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return false;
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}
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}
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// base::WriteFile takes an int size.
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if (size > std::numeric_limits<int>::max()) {
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LOG(ERROR) << "Cannot write to " << path.value()
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<< ". Data is too large: " << size << " bytes.";
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return false;
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}
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int data_written = base::WriteFile(path, data, size);
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return data_written == static_cast<int>(size);
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}
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bool SyncFileOrDirectory(const base::FilePath& path,
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bool is_directory,
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bool data_sync) {
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const base::TimeTicks start = base::TimeTicks::Now();
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data_sync = data_sync && !is_directory;
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int flags = (is_directory ? O_RDONLY | O_DIRECTORY : O_WRONLY);
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int fd = HANDLE_EINTR(open(path.value().c_str(), flags));
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if (fd < 0) {
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PLOG(WARNING) << "Could not open " << path.value() << " for syncing";
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return false;
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}
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// POSIX specifies EINTR as a possible return value of fsync() but not for
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// fdatasync(). To be on the safe side, it is handled in both cases.
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int result =
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(data_sync ? HANDLE_EINTR(fdatasync(fd)) : HANDLE_EINTR(fsync(fd)));
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if (result < 0) {
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PLOG(WARNING) << "Failed to sync " << path.value();
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close(fd);
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return false;
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}
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// close() may not be retried on error.
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result = IGNORE_EINTR(close(fd));
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if (result < 0) {
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PLOG(WARNING) << "Failed to close after sync " << path.value();
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return false;
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}
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const base::TimeDelta delta = base::TimeTicks::Now() - start;
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if (delta > kLongSync) {
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LOG(WARNING) << "Long " << (data_sync ? "fdatasync" : "fsync") << "() of "
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<< path.value() << ": " << delta.InSeconds() << " seconds";
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}
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return true;
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}
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bool WriteToFileAtomic(const base::FilePath& path,
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const char* data,
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size_t size,
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mode_t mode) {
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if (!base::DirectoryExists(path.DirName())) {
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if (!base::CreateDirectory(path.DirName())) {
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LOG(ERROR) << "Cannot create directory: " << path.DirName().value();
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return false;
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}
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}
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std::string random_suffix = GetRandomSuffix();
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if (random_suffix.empty()) {
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PLOG(WARNING) << "Could not compute random suffix";
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return false;
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}
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std::string temp_name = path.AddExtension(random_suffix).value();
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int fd =
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HANDLE_EINTR(open(temp_name.c_str(), O_CREAT | O_EXCL | O_WRONLY, mode));
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if (fd < 0) {
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PLOG(WARNING) << "Could not open " << temp_name << " for atomic write";
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unlink(temp_name.c_str());
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return false;
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}
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size_t position = 0;
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while (position < size) {
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ssize_t bytes_written =
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HANDLE_EINTR(write(fd, data + position, size - position));
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if (bytes_written < 0) {
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PLOG(WARNING) << "Could not write " << temp_name;
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close(fd);
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unlink(temp_name.c_str());
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return false;
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}
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position += bytes_written;
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}
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if (HANDLE_EINTR(fdatasync(fd)) < 0) {
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PLOG(WARNING) << "Could not fsync " << temp_name;
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close(fd);
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unlink(temp_name.c_str());
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return false;
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}
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if (close(fd) < 0) {
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PLOG(WARNING) << "Could not close " << temp_name;
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unlink(temp_name.c_str());
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return false;
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}
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if (rename(temp_name.c_str(), path.value().c_str()) < 0) {
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PLOG(WARNING) << "Could not close " << temp_name;
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unlink(temp_name.c_str());
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return false;
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}
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return true;
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}
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bool WriteBlobToFileAtomic(const base::FilePath& path,
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const Blob& blob,
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mode_t mode) {
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return WriteToFileAtomic(path, reinterpret_cast<const char*>(blob.data()),
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blob.size(), mode);
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}
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} // namespace brillo
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