How to get fully qualified domain name on Windows in Delphi - windows

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;

Answer 3

I tried all of the above, but without success. In the end, I settled for simply grabbing the environment variable.
uses jclSysInfo;
function GetDomain:string;
begin
result:=GetEnvironmentVariable('USERDNSDOMAIN');
end;
Tested on Server 2008 R2 - works fine. Returns "server.home.lan".
Results in an empty string on a Windows 7 non-domain connected PC.

Answer 4

The only correct api to use is DsGetDcName.
Because NetGetJoinInformation is still from the 'lanmanager age' so, the domain is LM compliant.
The code here is C, but you are smart enough to do the same in Delphi :)
PDOMAIN_CONTROLLER_INFOW pdomInfo ;
auto result1 = ::DsGetDcNameW(nullptr, nullptr, nullptr, nullptr, DS_DIRECTORY_SERVICE_PREFERRED | DS_RETURN_DNS_NAME, &pdomInfo);
if (result1 == ERROR_SUCCESS) {
auto retVal = SysAllocString(pdomInfo->DomainName);
::NetApiBufferFree(pdomInfo);
}