Create CrashReportDatabase interface, a test, and a Mac implementation.

client/crash_report_database_mac.mm

Index: client/crash_report_database_mac.mm
diff --git a/client/crash_report_database_mac.mm b/client/crash_report_database_mac.mm
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+// Copyright 2015 The Crashpad Authors. All rights reserved.
+//
+// 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
+//
+//     http://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.
+
+#include "client/crash_report_database.h"
+
+#include <errno.h>
+#include <fcntl.h>
+#import <Foundation/Foundation.h>
+#include <stdio.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <unistd.h>
+#include <uuid/uuid.h>
+
+#include "base/logging.h"
+#include "base/posix/eintr_wrapper.h"
+#include "base/scoped_generic.h"
+#include "base/strings/string_piece.h"
+#include "base/strings/stringprintf.h"
+#include "base/strings/sys_string_conversions.h"
+#include "util/file/file_io.h"
+#include "util/mac/xattr.h"
+
+namespace crashpad {
+
+namespace {
+
+const char kDatabaseDirectoryName[] = "Crashpad";
+
+const char kWriteDirectory[] = "new";
+const char kUploadPendingDirectory[] = "pending";
+const char kCompletedDirectory[] = "completed";
+
+const char* const kReportDirectories[] = {
+  kWriteDirectory,
+  kUploadPendingDirectory,
+  kCompletedDirectory,
+};
+
+const char kCrashReportFileExtension[] = "dmp";
+
+const char kXattrUUID[] = "uuid";
+const char kXattrCollectorID[] = "id";
+const char kXattrCreationTime[] = "creation_time";
+const char kXattrIsUploaded[] = "uploaded";
+const char kXattrLastUploadTime[] = "last_upload_time";
+const char kXattrUploadAttemptCount[] = "upload_count";
+
+const char kXattrDatabaseInitialized[] = "initialized";
+
+// Ensures that the node at |path| is a directory, and creates it if it does
+// not exist. If the |path| points to a file, rather than a directory, or the
+// directory could not be created, returns false. Otherwise, returns true,
+// indicating that |path| already was or now is a directory.
+bool CreateOrEnsureDirectoryExists(const base::FilePath& path) {
+  if (mkdir(path.value().c_str(), 0755) == 0) {
+    return true;
+  } else if (errno == EEXIST) {
+    struct stat st;
+    if (stat(path.value().c_str(), &st) != 0) {
+      PLOG(ERROR) << "stat";
+      return false;
+    }
+    if (S_ISDIR(st.st_mode)) {
+      return true;
+    } else {
+      LOG(ERROR) << "not a directory";
+      return false;
+    }
+  } else {
+    PLOG(ERROR) << "mkdir";
+    return false;
+  }
+}
+
+//! \brief A CrashReportDatabase that uses HFS+ extended attributes to store
+//!     report metadata.
+//!
+//! The database maintains three directories of reports: `"new"` to hold crash
+//! reports that are in the process of being written, `"completed"` to hold
+//! reports that have been written and are awaing upload, and `"uploaded"` to
+//! hold reports successfully uploaded to a collection server. If the user has
+//! opted out of report collection, reports will still be written and moved
+//! to the completed directory, but they just will not be uploaded.
+//!
+//! The database stores its metadata in extended filesystem attributes. To
+//! ensure safe access, the report file is locked using `O_EXLOCK` during all
+//! extended attribute operations. The lock should be obtained using
+//! ObtainReportLock().
+class CrashReportDatabaseMac : public CrashReportDatabase {
+ public:
+  explicit CrashReportDatabaseMac(const base::FilePath& path);
+  virtual ~CrashReportDatabaseMac();
+
+  bool Initialize();
+
+  // CrashReportDatabase:
+  OperationStatus PrepareNewCrashReport(NewReport** report) override;
+  OperationStatus FinishedWritingCrashReport(NewReport* report,
+                                             UUID* uuid) override;
+  OperationStatus LookUpCrashReport(const UUID& uuid,
+                                    Report* report) override;
+  OperationStatus GetPendingReports(
+      std::vector<const Report>* reports) override;
+  OperationStatus GetCompletedReports(
+      std::vector<const Report>* reports) override;
+  OperationStatus GetReportForUploading(const UUID& uuid,
+                                        const Report** report) override;
+  OperationStatus RecordUploadAttempt(const Report* report,
+                                      bool successful,
+                                      const std::string& id) override;
+  OperationStatus SkipReportUpload(const UUID& uuid) override;
+
+ private:
+  //! \brief A private extension of the Report class that maintains bookkeeping
+  //!    information of the database.
+  struct UploadReport : public Report {
+    //! \brief Stores the flock of the file for the duration of
+    //!     GetReportForUploading() and RecordUploadAttempt().
+    int lock_fd;
+  };
+
+  //! \brief Locates a crash report in the database by UUID.
+  //!
+  //! \param[in] uuid The UUID of the crash report to locate.
+  //!
+  //! \return The full path to the report file, or an empty path if it cannot be
+  //!     found.
+  base::FilePath LocateCrashReport(const UUID& uuid);
+
+  //! \brief Obtains an exclusive advisory lock on a file.
+  //!
+  //! The flock is used to prevent cross-process concurrent metadata reads or
+  //! writes. While xattrs do not observe the lock, if the lock-then-mutate
+  //! protocol is observed by all clients of the database, it still enforces
+  //! synchronization.
+  //!
+  //! This does not block, and so callers must ensure that the lock is valid
+  //! after calling.
+  //!
+  //! \param[in] path The path of the file to lcok.
+  //!
+  //! \return A scoped lock object. If the result is not valid, an error is
+  //!     logged.
+  static base::ScopedFD ObtainReportLock(const base::FilePath& path);
+
+  //! \brief Reads all the database xattrs from a file into a Report. The file
+  //!     must be locked with ObtainReportLock.
+  //!
+  //! \param[in] path The path of the report.
+  //! \param[out] report The object into which data will be read.
+  //!
+  //! \return `true` if all the metadata was read successfully, `false`
+  //!     otherwise.
+  static bool ReadReportMetadataLocked(const base::FilePath& path,
+                                       Report* report);
+
+  //! \brief Reads the metadata from all the reports in a database subdirectory.
+  //!      Invalid reports are skipped.
+  //!
+  //! \param[in] path The database subdirectory path.
+  //! \param[out] reports An empty vector of reports, which will be filled.
+  //!
+  //! \return The operation status code.
+  static OperationStatus ReportsInDirectory(const base::FilePath& path,
+                                            std::vector<const Report>* reports);
+
+
+  //! \brief Creates a database xattr name from the short constant name.
+  //!
+  //! \param[in] name The short name of the extended attribute.
+  //!
+  //! \return The long name of the extended attribute.
+  static std::string XattrName(const base::StringPiece& name);
+
+  base::FilePath base_dir_;
+
+  DISALLOW_COPY_AND_ASSIGN(CrashReportDatabaseMac);
+};
+
+CrashReportDatabaseMac::CrashReportDatabaseMac(const base::FilePath& path)
+    : CrashReportDatabase(), base_dir_(path) {
+}
+
+CrashReportDatabaseMac::~CrashReportDatabaseMac() {}
+
+bool CrashReportDatabaseMac::Initialize() {
+  // Check if the database already exists.
+  if (!CreateOrEnsureDirectoryExists(base_dir_))
+    return false;
+
+  // Create the three processing directories for the database.
+  for (size_t i = 0; i < arraysize(kReportDirectories); ++i) {
+    if (!CreateOrEnsureDirectoryExists(base_dir_.Append(kReportDirectories[i])))
+      return false;
+  }
+
+  // Write an xattr as the last step, to ensure the filesystem has support for
+  // them. This attribute will never be read.
+  return WriteXattrBool(base_dir_, XattrName(kXattrDatabaseInitialized), true);
+}
+
+CrashReportDatabase::OperationStatus
+CrashReportDatabaseMac::PrepareNewCrashReport(NewReport** out_report) {
+  uuid_t uuid_gen;
+  uuid_generate(uuid_gen);
+  UUID uuid(uuid_gen);
+
+  scoped_ptr<NewReport> report(new NewReport());
+
+  report->path =
+      base_dir_.Append(kWriteDirectory)
+               .Append(uuid.ToString() + "." + kCrashReportFileExtension);
+
+  report->handle = HANDLE_EINTR(open(report->path.value().c_str(),
+                                     O_CREAT | O_WRONLY | O_EXCL | O_EXLOCK,
+                                     0600));
+  if (report->handle < 0) {
+    PLOG(ERROR) << "open " << report->path.value();
+    return kFileSystemError;
+  }
+
+  // TODO(rsesek): Potentially use an fsetxattr() here instead.
+  if (!WriteXattr(report->path, XattrName(kXattrUUID), uuid.ToString())) {
+    PLOG_IF(ERROR, IGNORE_EINTR(close(report->handle)) != 0) << "close";
+    return kDatabaseError;
+  }
+
+  *out_report = report.release();
+
+  return kNoError;
+}
+
+CrashReportDatabase::OperationStatus
+CrashReportDatabaseMac::FinishedWritingCrashReport(NewReport* report,
+                                                   UUID* uuid) {
+  // Takes ownership of the |handle| and the O_EXLOCK.
+  base::ScopedFD lock(report->handle);
+
+  // Take ownership of the report.
+  scoped_ptr<NewReport> scoped_report(report);
+
+  // Get the report's UUID to return.
+  std::string uuid_string;
+  if (ReadXattr(report->path, XattrName(kXattrUUID),
+                &uuid_string) != XattrStatus::kOK ||
+      !uuid->InitializeFromString(uuid_string)) {
+    LOG(ERROR) << "Failed to read UUID for crash report "
+               << report->path.value();
+    return kDatabaseError;
+  }
+
+  // Record the creation time of this report.
+  if (!WriteXattrTimeT(report->path, XattrName(kXattrCreationTime),
+                       time(nullptr))) {
+    return kDatabaseError;
+  }
+
+  // Move the report to its new location for uploading.
+  base::FilePath new_path =
+      base_dir_.Append(kUploadPendingDirectory).Append(report->path.BaseName());
+  if (rename(report->path.value().c_str(), new_path.value().c_str()) != 0) {
+    PLOG(ERROR) << "rename " << report->path.value() << " to "
+                << new_path.value();
+    return kFileSystemError;
+  }
+
+  return kNoError;
+}
+
+CrashReportDatabase::OperationStatus
+CrashReportDatabaseMac::LookUpCrashReport(const UUID& uuid,
+                                          CrashReportDatabase::Report* report) {
+  base::FilePath path = LocateCrashReport(uuid);
+  if (path.empty())
+    return kReportNotFound;
+
+  base::ScopedFD lock(ObtainReportLock(path));
+  if (!lock.is_valid())
+    return kBusyError;
+
+  *report = Report();
+  report->file_path = path;
+  if (!ReadReportMetadataLocked(path, report))
+    return kDatabaseError;
+
+  return kNoError;
+}
+
+CrashReportDatabase::OperationStatus
+CrashReportDatabaseMac::GetPendingReports(
+    std::vector<const CrashReportDatabase::Report>* reports) {
+  return ReportsInDirectory(base_dir_.Append(kUploadPendingDirectory), reports);
+}
+
+CrashReportDatabase::OperationStatus
+CrashReportDatabaseMac::GetCompletedReports(
+    std::vector<const CrashReportDatabase::Report>* reports) {
+  return ReportsInDirectory(base_dir_.Append(kCompletedDirectory), reports);
+}
+
+CrashReportDatabase::OperationStatus
+CrashReportDatabaseMac::GetReportForUploading(const UUID& uuid,
+                                              const Report** report) {
+  base::FilePath report_path = LocateCrashReport(uuid);
+  if (report_path.empty())
+    return kReportNotFound;
+
+  scoped_ptr<UploadReport> upload_report(new UploadReport());
+  upload_report->file_path = report_path;
+
+  base::ScopedFD lock(ObtainReportLock(report_path));
+  if (!lock.is_valid())
+    return kBusyError;
+
+  if (!ReadReportMetadataLocked(report_path, upload_report.get()))
+    return kDatabaseError;
+
+  upload_report->lock_fd = lock.release();
+  *report = upload_report.release();
+  return kNoError;
+}
+
+CrashReportDatabase::OperationStatus
+CrashReportDatabaseMac::RecordUploadAttempt(const Report* report,
+                                            bool successful,
+                                            const std::string& id) {
+  DCHECK(report);
+  DCHECK(successful || id.empty());
+
+  base::FilePath report_path = LocateCrashReport(report->uuid);
+  if (report_path.empty())
+    return kReportNotFound;
+
+  scoped_ptr<const UploadReport> upload_report(
+      static_cast<const UploadReport*>(report));
+
+  base::ScopedFD lock(upload_report->lock_fd);
+  if (!lock.is_valid())
+    return kBusyError;
+
+  if (successful) {
+    base::FilePath new_path =
+        base_dir_.Append(kCompletedDirectory).Append(report_path.BaseName());
+    if (rename(report_path.value().c_str(), new_path.value().c_str()) != 0) {
+      PLOG(ERROR) << "rename " << report_path.value() << " to "
+                  << new_path.value();
+      return kFileSystemError;
+    }
+    report_path = new_path;
+  }
+
+  if (!WriteXattrBool(report_path, XattrName(kXattrIsUploaded), successful)) {
+    return kDatabaseError;
+  }
+  if (!WriteXattr(report_path, XattrName(kXattrCollectorID), id)) {
+    return kDatabaseError;
+  }
+  if (!WriteXattrTimeT(report_path,
+                       XattrName(kXattrLastUploadTime),
+                       time(nullptr))) {
+    return kDatabaseError;
+  }
+
+  int upload_attempts = 0;
+  std::string name = XattrName(kXattrUploadAttemptCount);
+  if (ReadXattrInt(report_path, name, &upload_attempts) ==
+          XattrStatus::kOtherError) {
+    return kDatabaseError;
+  }
+  if (!WriteXattrInt(report_path, name, ++upload_attempts)) {
+    return kDatabaseError;
+  }
+
+  return kNoError;
+}
+
+CrashReportDatabase::OperationStatus CrashReportDatabaseMac::SkipReportUpload(
+    const UUID& uuid) {
+  base::FilePath report_path = LocateCrashReport(uuid);
+  if (report_path.empty())
+    return kReportNotFound;
+
+  base::ScopedFD lock(ObtainReportLock(report_path));
+  if (!lock.is_valid())
+    return kBusyError;
+
+  base::FilePath new_path =
+      base_dir_.Append(kCompletedDirectory).Append(report_path.BaseName());
+  if (rename(report_path.value().c_str(), new_path.value().c_str()) != 0) {
+    PLOG(ERROR) << "rename " << report_path.value() << " to "
+                << new_path.value();
+    return kFileSystemError;
+  }
+
+  return kNoError;
+}
+
+base::FilePath CrashReportDatabaseMac::LocateCrashReport(const UUID& uuid) {
+  const std::string target_uuid = uuid.ToString();
+  for (size_t i = 0; i < arraysize(kReportDirectories); ++i) {
+    base::FilePath path =
+       base_dir_.Append(kReportDirectories[i])
+                .Append(target_uuid + "." + kCrashReportFileExtension);
+
+    // Test if the path exists.
+    struct stat st;
+    if (lstat(path.value().c_str(), &st)) {
+      continue;
+    }
+
+    // Check that the UUID of the report matches.
+    std::string uuid_string;
+    if (ReadXattr(path, XattrName(kXattrUUID),
+                  &uuid_string) == XattrStatus::kOK &&
+        uuid_string == target_uuid) {
+      return path;
+    }
+  }
+
+  return base::FilePath();
+}
+
+// static
+base::ScopedFD CrashReportDatabaseMac::ObtainReportLock(
+    const base::FilePath& path) {
+  int fd = HANDLE_EINTR(open(path.value().c_str(),
+                             O_RDONLY | O_EXLOCK | O_CLOEXEC | O_NONBLOCK));
+  PLOG_IF(ERROR, fd < 0) << "open lock " << path.value();
+  return base::ScopedFD(fd);
+}
+
+// static
+bool CrashReportDatabaseMac::ReadReportMetadataLocked(
+    const base::FilePath& path, Report* report) {
+  std::string uuid_string;
+  if (ReadXattr(path, XattrName(kXattrUUID),
+                &uuid_string) != XattrStatus::kOK ||
+      !report->uuid.InitializeFromString(uuid_string)) {
+    return false;
+  }
+
+  if (ReadXattrTimeT(path, XattrName(kXattrCreationTime),
+                     &report->creation_time) != XattrStatus::kOK) {
+    return false;
+  }
+
+  report->id = std::string();
+  if (ReadXattr(path, XattrName(kXattrCollectorID),
+                &report->id) == XattrStatus::kOtherError) {
+    return false;
+  }
+
+  report->uploaded = false;
+  if (ReadXattrBool(path, XattrName(kXattrIsUploaded),
+                    &report->uploaded) == XattrStatus::kOtherError) {
+    return false;
+  }
+
+  report->last_upload_attempt_time = 0;
+  if (ReadXattrTimeT(path, XattrName(kXattrLastUploadTime),
+                     &report->last_upload_attempt_time) ==
+          XattrStatus::kOtherError) {
+    return false;
+  }
+
+  report->upload_attempts = 0;
+  if (ReadXattrInt(path, XattrName(kXattrUploadAttemptCount),
+                   &report->upload_attempts) == XattrStatus::kOtherError) {
+    return false;
+  }
+
+  return true;
+}
+
+// static
+CrashReportDatabase::OperationStatus
+CrashReportDatabaseMac::ReportsInDirectory(
+    const base::FilePath& path,
+    std::vector<const CrashReportDatabase::Report>* reports) {
+  DCHECK(reports->empty());
+
+  NSError* error = nil;
+  NSArray* paths = [[NSFileManager defaultManager]
+      contentsOfDirectoryAtPath:base::SysUTF8ToNSString(path.value())
+                          error:&error];
+  if (error) {
+    LOG(ERROR) << "Failed to enumerate reports in directory " << path.value()
+               << ": " << [[error description] UTF8String];
+    return kFileSystemError;
+  }
+
+  reports->reserve([paths count]);
+  for (NSString* entry in paths) {
+    base::FilePath report_path = path.Append([entry fileSystemRepresentation]);
+    base::ScopedFD lock(ObtainReportLock(report_path));
+    if (!lock.is_valid())
+      continue;
+
+    Report report;
+    if (!ReadReportMetadataLocked(report_path, &report)) {
+      LOG(WARNING) << "Failed to read report metadata for "
+                   << report_path.value();
+      continue;
+    }
+    reports->push_back(report);
+  }
+
+  return kNoError;
+}
+
+// static
+std::string CrashReportDatabaseMac::XattrName(const base::StringPiece& name) {
+  return base::StringPrintf("com.googlecode.crashpad.%s", name.data());
+}
+
+}  // namespace
+
+// static
+scoped_ptr<CrashReportDatabase> CrashReportDatabase::Initialize(
+    const base::FilePath& path) {
+  scoped_ptr<CrashReportDatabaseMac> database_mac(
+      new CrashReportDatabaseMac(path.Append(kDatabaseDirectoryName)));
+  if (!database_mac->Initialize())
+    database_mac.reset();
+
+  return scoped_ptr<CrashReportDatabase>(database_mac.release());
+}
+
+}  // namespace crashpad