Add a new function for getting a deterministic machine ID

chrome/browser/prefs/tracked/device_id_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 "chrome/browser/prefs/tracked/device_id.h"
+
+#include <windows.h>
+#include <sddl.h>  // For ConvertSidToStringSidA.
+
+#include <cwchar>
+
+#include "base/macros.h"
+#include "base/memory/scoped_ptr.h"
+#include "base/logging.h"
+
+namespace tracked_prefs {
+
+MachineIdStatus GetDeterministicMachineSpecificId(std::string* machine_id) {
+  DCHECK(machine_id);
+
+  wchar_t computer_name[MAX_COMPUTERNAME_LENGTH + 1] = {};
+  DWORD computer_name_size = arraysize(computer_name);
+
+  if (!::GetComputerNameW(computer_name, &computer_name_size))
+    return FAILURE;
+
+  DWORD sid_size = SECURITY_MAX_SID_SIZE;
+  char sid_buffer[SECURITY_MAX_SID_SIZE];
+  SID* sid = reinterpret_cast<SID*>(sid_buffer);
+  DWORD domain_size = 128;  // Will expand if needed.

[gab, 2015/01/26 19:40:46]

s/Will expand if needed/Will expand below if needed

[alito, 2015/01/26 21:01:11]

Done.

+  scoped_ptr<wchar_t[]> domain_buffer(new wchar_t[domain_size]);
+  SID_NAME_USE sid_name_use;
+
+  if (!::LookupAccountNameW(NULL, computer_name, sid, &sid_size,
+                            domain_buffer.get(), &domain_size,
+                            &sid_name_use)) {
+    // If the initial size of domain_buffer was too small, the
+    // required size is now found in domain_size. Resize and try

[gab, 2015/01/26 19:40:46]

s/domain_buffer/|domain_buffer|

same for domain_size

[alito, 2015/01/26 21:01:11]

Done.

+    // again.
+    if (::GetLastError() != ERROR_INSUFFICIENT_BUFFER)
+      return FAILURE;
+
+    domain_buffer.reset(new wchar_t[domain_size]);
+    if (!::LookupAccountNameW(NULL, computer_name, sid, &sid_size,
+                              domain_buffer.get(), &domain_size,
+                              &sid_name_use)) {
+      return FAILURE;
+    }
+  }
+
+  // We want to ensure that the correct type of SID was obtained. The

[gab, 2015/01/26 19:40:46]

Pronouns in comments are frowned upon in Chromium.

s/We want to ensure/Ensure

[alito, 2015/01/26 21:01:11]

Done.

+  // |LookupAccountNameW()| function seems to always return
+  // |SidTypeDomain| instead of |SidTypeComputer| when the computer name
+  // is passed in as its second argument and therefore we will accept

[gab, 2015/01/26 19:40:46]

s/second argument and therefore we will accept either of the two enum
values/second argument and therefore both values will be considered acceptable.

[alito, 2015/01/26 21:01:11]

Done.

+  // either of the two enum values. If the computer name and user name
+  // coincide, |LookupAccountNameW()| seems to always return the machine
+  // SID and set the returned enum to |SidTypeDomain|.
+  if (sid_name_use != SID_NAME_USE::SidTypeComputer &&

[gab, 2015/01/26 19:40:46]

Let's just assume this is correct and not handle failure, i.e.:

DCHECK(sid_name_use == SID_NAME_USE::SidTypeComputer || sid_name_use ==
SID_NAME_USE::SidTypeDomain);

[alito, 2015/01/26 21:01:11]

Done.

+      sid_name_use != SID_NAME_USE::SidTypeDomain) {
+    return FAILURE;
+  }
+
+  char* sid_string = NULL;
+  if (!::ConvertSidToStringSidA(sid, &sid_string))
+    return FAILURE;
+
+  *machine_id = sid_string;
+  ::LocalFree(sid_string);
+
+  return SUCCESS;
+}
+
+}  // namespace tracked_prefs