How to get fully qualified domain name on Windows in Delphi

Question

I need to get a fully qualified domain name for a Windows machine on a domain in Delphi.

I've tried to use LookupAccountSid but it gives me only the netbios domain name, in my case it is "intranet" but I need the full "intranet.companyname.com"

Any Ideas?

Answer 1

Try the GetUserNameEx Windows API function.

const
  NameUnknown            = 0;
  NameFullyQualifiedDN   = 1;
  NameSamCompatible      = 2;
  NameDisplay            = 3;
  NameUniqueId           = 6;
  NameCanonical          = 7;
  NameUserPrincipal      = 8;
  NameCanonicalEx        = 9;
  NameServicePrincipal   = 10;
  NameDnsDomain          = 12;

function GetUserNameExString(ANameFormat: DWORD): string;
var
  Buf: array[0..256] of Char;
  BufSize: DWORD;
  GetUserNameEx: function (NameFormat: DWORD; lpNameBuffer: LPSTR;
    var nSize: ULONG): BOOL; stdcall;
begin
  Result := '';
  BufSize := SizeOf(Buf) div SizeOf(Buf[0]);
  GetUserNameEx := GetProcAddress(GetModuleHandle('secur32.dll'), 'GetUserNameExA');
  if Assigned(GetUserNameEx) then
    if GetUserNameEx(ANameFormat, Buf, BufSize) then
      Result := Buf;
end;

using the NameDnsDomain format for example, will result www.mydomain.com\user_name if you are logged into "www.mydomain.com" domain.

---

Since I now implemented this for my own needs in our application, @iPath's comment was quit right. better use GetComputerNameEx, and specify one of the COMPUTER_NAME_FORMAT for your own needs.

A Delphi implementation would look like this (Unicode version):

interface
...
type
  COMPUTER_NAME_FORMAT = (
    ComputerNameNetBIOS,
    ComputerNameDnsHostname,
    ComputerNameDnsDomain,
    ComputerNameDnsFullyQualified,
    ComputerNamePhysicalNetBIOS,
    ComputerNamePhysicalDnsHostname,
    ComputerNamePhysicalDnsDomain,
    ComputerNamePhysicalDnsFullyQualified,
    ComputerNameMax);

function GetComputerNameExString(ANameFormat: COMPUTER_NAME_FORMAT): WideString;

implementation
...
function GetComputerNameExW(NameType: COMPUTER_NAME_FORMAT; lpBuffer: LPWSTR;
  var nSize: DWORD): BOOL; stdcall; external kernel32 name 'GetComputerNameExW';

function GetComputerNameExString(ANameFormat: COMPUTER_NAME_FORMAT): WideString;
var
  nSize: DWORD;
begin
  nSize := 1024;
  SetLength(Result, nSize);
  if GetComputerNameExW(ANameFormat, PWideChar(Result), nSize) then
    SetLength(Result, nSize)
  else
    Result := '';
end;

Answer 2

NetGetJoinInformation should work fine.

MSDN:

http://msdn.microsoft.com/en-us/library/windows/desktop/aa370423(v=vs.85).aspx

Example:

type
  PWKSTA_INFO_100 = ^WKSTA_INFO_100;

  WKSTA_INFO_100 = packed record
    wki100_platform_id: DWord;
    wki100_computername: PWChar;
    wki100_langroup: PWChar;
    wki100_ver_major: DWord;
    wki100_ver_minor: DWord;
  end;

  TNetSetupJoinStatus =
  (
    NetSetupUnknownStatus,
    NetSetupUnjoined,
    NetSetupWorkgroupName,
    NetSetupDomainName
  );

  TNetApiBufferFreeFunction = function(ABuffer: Pointer): DWORD; stdcall;
  TNetWkstaGetInfoFunction  = function(const AServername: PWChar; const ALevel: DWord; const ABufptr: Pointer): DWORD; stdcall;
  TNetGetJoinInformationFunction = function(const AServerName: PWChar; out ANameBuffer: PWChar; out ABufferType: TNetSetupJoinStatus): DWORD; stdcall;

const
  NERR_SUCCESS = 0;

function GetLocalComputerDomainName: string;
var
  NetApiBuffer: Pointer;
  NetApi: THandle;
  NetApiBufferFree: TNetApiBufferFreeFunction;
  NetWkstaGetInfo: TNetWkstaGetInfoFunction;
  NetGetJoinInformation: TNetGetJoinInformationFunction;
  NetSetupJoinStatus: TNetSetupJoinStatus;
  NameBuffer: PWideChar;
begin
  Result := '';
  NetApi := LoadLibrary('netapi32.dll');
  if NetApi <> 0 then
  begin
    NetApiBufferFree      := TNetApiBufferFreeFunction(     GetProcAddress(NetApi, 'NetApiBufferFree'));
    NetGetJoinInformation := TNetGetJoinInformationFunction(GetProcAddress(NetApi, 'NetGetJoinInformation'));
    NetWkstaGetInfo       := TNetWkstaGetInfoFunction(      GetProcAddress(NetApi, 'NetWkstaGetInfo'));
    if @NetApiBufferFree <> nil then
    begin
      if @NetSetupJoinStatus <> nil then
      begin
        if NetGetJoinInformation(nil, NameBuffer, NetSetupJoinStatus) = NERR_SUCCESS then
        begin
          if NetSetupJoinStatus = NetSetupDomainName then
          begin
            Result := NameBuffer;
          end;
          NetApiBufferFree(NameBuffer);
        end;
      end;
    end;
    FreeLibrary(NetApi);
  end;
end;