components/browser_watcher/crash_reporting_metrics_win.cc

// 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 "components/browser_watcher/crash_reporting_metrics_win.h"

#include <algorithm>
#include "base/atomicops.h"
#include "base/guid.h"
#include "base/logging.h"
#include "base/strings/safe_sprintf.h"
#include "base/strings/string_util.h"
#include "base/strings/utf_string_conversions.h"
#include "base/win/registry.h"

namespace browser_watcher {

namespace {

// The prior implementation used 0 and 1. Its data collection is inconsistent
// with ours and it's best to just ignore its records. So we start at 2.
const DWORD kCrashDumpAttempt = 2;
const DWORD kDumpWithoutCrashAttempt = 3;
const DWORD kCrashDumpSuccess = 4;
const DWORD kCrashDumpFailure = 5;
const DWORD kDumpWithoutCrashSuccess = 6;
const DWORD kDumpWithoutCrashFailure = 7;

// A prefix intended to avoid registry value name collisions with other
// processes (or modules within a single process). It is not necessary for the
// reading and writing instances to share the prefix value. This array is sized
// to hold a null-terminated string as generated by base::GenerateGUID.
char g_unique_prefix[36 + 1] = {0};

// An atomic counter intended  to make each registry value name unique within
// this process and module.
base::subtle::Atomic32 g_record_count = 0;

// The length of a null-terminated string consisting of "{GUID}-{COUNT}".
const size_t kValueNameSize = 36 + 1 + 8 + 1;

void WriteValue(const base::string16& key_path, DWORD value) {
  // Generate the final value name we'll use (appends the crash number to the
  // base value name).
  char value_name_ascii[kValueNameSize] = "";
  base::char16 value_name_utf16[kValueNameSize] = L"";

  if (base::strings::SafeSPrintf(
          value_name_ascii, "%s-%x", g_unique_prefix,
          base::subtle::NoBarrier_AtomicIncrement(&g_record_count, 1)) <= 0) {
    NOTREACHED();
  } else {
    // Since it's an ASCII string, the UTF-16 form is identical with leading 0
    // bytes. We're avoiding unnecessary heap operations since we're running in
    // a compromised process.
    std::copy(value_name_ascii, value_name_ascii + kValueNameSize,
              value_name_utf16);

    base::win::RegKey reg_key;
    if (reg_key.Create(HKEY_CURRENT_USER, key_path.c_str(), KEY_SET_VALUE) !=
        ERROR_SUCCESS) {
      NOTREACHED();
    } else {
      reg_key.WriteValue(value_name_utf16, value);
    }
  }

}

}  // namespace

CrashReportingMetrics::CrashReportingMetrics(
    const base::string16& registry_path)
    : registry_path_(registry_path) {
  if (g_unique_prefix[0] == 0) {
    std::string guid = base::GenerateGUID();
    // It seems reasonable to assume that the worst possible outcome of two
    // separate threads trying to do the following would be to store a GUID
    // value that is a hybrid of the two intended values. Hence we can avoid any
    // thread-safety caveats in our public API.
    size_t copied_size = base::strlcpy(g_unique_prefix, guid.c_str(),
                                       arraysize(g_unique_prefix));
    DCHECK_EQ(copied_size, guid.length());
  }
}

void CrashReportingMetrics::RecordCrashDumpAttempt() {
  WriteValue(registry_path_, kCrashDumpAttempt);
}

void CrashReportingMetrics::RecordDumpWithoutCrashAttempt() {
  WriteValue(registry_path_, kDumpWithoutCrashAttempt);
}
void CrashReportingMetrics::RecordCrashDumpAttemptResult(bool succeeded) {
  WriteValue(registry_path_, succeeded ? kCrashDumpSuccess : kCrashDumpFailure);
}
void CrashReportingMetrics::RecordDumpWithoutCrashAttemptResult(
    bool succeeded) {
  WriteValue(registry_path_,
             succeeded ? kDumpWithoutCrashSuccess : kDumpWithoutCrashFailure);
}

CrashReportingMetrics::Values CrashReportingMetrics::RetrieveAndResetMetrics() {
  Values values = {0};

  // Open the registry key for iteration.
  base::win::RegKey regkey;
  if (regkey.Open(HKEY_CURRENT_USER, registry_path_.c_str(),
                  KEY_QUERY_VALUE | KEY_SET_VALUE) != ERROR_SUCCESS) {
    return values;
  }

  // Track a list of values to delete. We don't modify the registry key while
  // we're iterating over its values.
  typedef std::vector<base::string16> StringVector;
  StringVector to_delete;

  // Iterate over the values in the key counting dumps with and without crashes.
  // We directly walk the values instead of using RegistryValueIterator in order
  // to read all of the values as DWORDS instead of strings.
  base::string16 name;
  DWORD value = 0;
  for (int i = regkey.GetValueCount() - 1; i >= 0; --i) {
    if (regkey.GetValueNameAt(i, &name) == ERROR_SUCCESS &&
        regkey.ReadValueDW(name.c_str(), &value) == ERROR_SUCCESS) {
      to_delete.push_back(name);
      switch (value) {
        case kCrashDumpAttempt:
          ++values.crash_dump_attempts;
          break;
        case kCrashDumpSuccess:
          ++values.successful_crash_dumps;
          break;
        case kCrashDumpFailure:
          ++values.failed_crash_dumps;
          break;
        case kDumpWithoutCrashAttempt:
          ++values.dump_without_crash_attempts;
          break;
        case kDumpWithoutCrashSuccess:
          ++values.successful_dumps_without_crash;
          break;
        case kDumpWithoutCrashFailure:
          ++values.failed_dumps_without_crash;
          break;
        default:
          // Presumably a pre-existing record from the previous implementation.
          // We will delete it.
          break;
      }
    }
  }

  // Delete the registry keys we've just counted.
  for (const auto& value_name : to_delete)
    regkey.DeleteValue(value_name.c_str());

  return values;
}

}  // namespace browser_watcher