Delphi: Prompt for UAC elevation when needed - delphi

Question

We need to change some settings to the HKEY_LOCAL_MACHINE at runtime.
Is it possible to prompt for uac elevation if needed at runtime, or do I have to launch a second elevated process to do 'the dirty work'?

Answer 1

i would relaunch yourself as elevated, passing command line parameters indicating what elevated thing you want to do. You can then jump right to the appropriate form, or just save your HKLM stuff.
function RunAsAdmin(hWnd: HWND; filename: string; Parameters: string): Boolean;
{
See Step 3: Redesign for UAC Compatibility (UAC)
http://msdn.microsoft.com/en-us/library/bb756922.aspx
This code is released into the public domain. No attribution required.
}
var
sei: TShellExecuteInfo;
begin
ZeroMemory(#sei, SizeOf(sei));
sei.cbSize := SizeOf(TShellExecuteInfo);
sei.Wnd := hwnd;
sei.fMask := SEE_MASK_FLAG_DDEWAIT or SEE_MASK_FLAG_NO_UI;
sei.lpVerb := PChar('runas');
sei.lpFile := PChar(Filename); // PAnsiChar;
if parameters <> '' then
sei.lpParameters := PChar(parameters); // PAnsiChar;
sei.nShow := SW_SHOWNORMAL; //Integer;
Result := ShellExecuteEx(#sei);
end;
The other Microsoft suggested solution is to create an COM object out of process (using the specially created CoCreateInstanceAsAdmin function). i don't like this idea because you have to write and register a COM object.
Note: There is no "CoCreateInstanceAsAdmin" API call. It's just some code floating around. Here's the Dephi version i stumbled around for. It is apparently based on the trick of prefixing a class guid string with the "Elevation:Administrator!new:" prefix when normally hidden code internally calls CoGetObject:
function CoGetObject(pszName: PWideChar; pBindOptions: PBindOpts3;
const iid: TIID; ppv: PPointer): HResult; stdcall; external 'ole32.dll';
procedure CoCreateInstanceAsAdmin(const Handle: HWND;
const ClassID, IID: TGuid; PInterface: PPointer);
var
BindOpts: TBindOpts3;
MonikerName: WideString;
Res: HRESULT;
begin
//This code is released into the public domain. No attribution required.
ZeroMemory(#BindOpts, Sizeof(TBindOpts3));
BindOpts.cbStruct := Sizeof(TBindOpts3);
BindOpts.hwnd := Handle;
BindOpts.dwClassContext := CLSCTX_LOCAL_SERVER;
MonikerName := 'Elevation:Administrator!new:' + GUIDToString(ClassID);
Res := CoGetObject(PWideChar(MonikerName), #BindOpts, IID, PInterface);
if Failed(Res) then
raise Exception.Create(SysErrorMessage(Res));
end;
One other question: How do you handle someone running as standard user in Windows XP?

Answer 2

You can't "elevate" an existing process. Elevated processes under UAC have a different token with a different LUID, different mandatory integrity level, and different group membership. This level of change can't be done within a running process - and it would be a security problem if that could happen.
You need to launch a second process elevated that would do the work or by creating a COM object that runs in an elevated dllhost.
http://msdn.microsoft.com/en-us/library/bb756922.aspx gives an example "RunAsAdmin" function and a "CoCreateInstanceAsAdmin" function.
EDIT: I just saw "Delphi" in your title. Everything I listed is obviously native, but if Delphi provides access to ShellExecute-like functionality you should be able to adapt the code from the link.

Answer 3

A sample of ready-to-use code:
Usage example:
unit Unit1;
interface
uses
Windows{....};
type
TForm1 = class(TForm)
Label1: TLabel;
Label2: TLabel;
Label3: TLabel;
Label4: TLabel;
Button1: TButton;
Button2: TButton;
procedure FormCreate(Sender: TObject);
procedure Button1Click(Sender: TObject);
procedure Button2Click(Sender: TObject);
private
procedure StartWait;
procedure EndWait;
end;
var
Form1: TForm1;
implementation
uses
RunElevatedSupport;
{$R *.dfm}
const
ArgInstallUpdate = '/install_update';
ArgRegisterExtension = '/register_global_file_associations';
procedure TForm1.FormCreate(Sender: TObject);
begin
Label1.Caption := Format('IsAdministrator: %s', [BoolToStr(IsAdministrator, True)]);
Label2.Caption := Format('IsAdministratorAccount: %s', [BoolToStr(IsAdministratorAccount, True)]);
Label3.Caption := Format('IsUACEnabled: %s', [BoolToStr(IsUACEnabled, True)]);
Label4.Caption := Format('IsElevated: %s', [BoolToStr(IsElevated, True)]);
Button1.Caption := 'Install updates';
SetButtonElevated(Button1.Handle);
Button2.Caption := 'Register file associations for all users';
SetButtonElevated(Button2.Handle);
end;
procedure TForm1.Button1Click(Sender: TObject);
begin
StartWait;
try
SetLastError(RunElevated(ArgInstallUpdate, Handle, Application.ProcessMessages));
if GetLastError <> ERROR_SUCCESS then
RaiseLastOSError;
finally
EndWait;
end;
end;
procedure TForm1.Button2Click(Sender: TObject);
begin
StartWait;
try
SetLastError(RunElevated(ArgRegisterExtension, Handle, Application.ProcessMessages));
if GetLastError <> ERROR_SUCCESS then
RaiseLastOSError;
finally
EndWait;
end;
end;
function DoElevatedTask(const AParameters: String): Cardinal;
procedure InstallUpdate;
var
Msg: String;
begin
Msg := 'Hello from InstallUpdate!' + sLineBreak +
sLineBreak +
'This function is running elevated under full administrator rights.' + sLineBreak +
'This means that you have write-access to Program Files folder and you''re able to overwrite files (e.g. install updates).' + sLineBreak +
'However, note that your executable is still running.' + sLineBreak +
sLineBreak +
'IsAdministrator: ' + BoolToStr(IsAdministrator, True) + sLineBreak +
'IsAdministratorAccount: ' + BoolToStr(IsAdministratorAccount, True) + sLineBreak +
'IsUACEnabled: ' + BoolToStr(IsUACEnabled, True) + sLineBreak +
'IsElevated: ' + BoolToStr(IsElevated, True);
MessageBox(0, PChar(Msg), 'Hello from InstallUpdate!', MB_OK or MB_ICONINFORMATION);
end;
procedure RegisterExtension;
var
Msg: String;
begin
Msg := 'Hello from RegisterExtension!' + sLineBreak +
sLineBreak +
'This function is running elevated under full administrator rights.' + sLineBreak +
'This means that you have write-access to HKEY_LOCAL_MACHINE key and you''re able to write keys and values (e.g. register file extensions globally/for all users).' + sLineBreak +
'However, note that this is usually not a good idea. It is better to register your file extensions under HKEY_CURRENT_USER\Software\Classes.' + sLineBreak +
sLineBreak +
'IsAdministrator: ' + BoolToStr(IsAdministrator, True) + sLineBreak +
'IsAdministratorAccount: ' + BoolToStr(IsAdministratorAccount, True) + sLineBreak +
'IsUACEnabled: ' + BoolToStr(IsUACEnabled, True) + sLineBreak +
'IsElevated: ' + BoolToStr(IsElevated, True);
MessageBox(0, PChar(Msg), 'Hello from RegisterExtension!', MB_OK or MB_ICONINFORMATION);
end;
begin
Result := ERROR_SUCCESS;
if AParameters = ArgInstallUpdate then
InstallUpdate
else
if AParameters = ArgRegisterExtension then
RegisterExtension
else
Result := ERROR_GEN_FAILURE;
end;
procedure TForm1.StartWait;
begin
Cursor := crHourglass;
Screen.Cursor := crHourglass;
Button1.Enabled := False;
Button2.Enabled := False;
Application.ProcessMessages;
end;
procedure TForm1.EndWait;
begin
Cursor := crDefault;
Screen.Cursor := crDefault;
Button1.Enabled := True;
Button2.Enabled := True;
Application.ProcessMessages;
end;
initialization
OnElevateProc := DoElevatedTask;
CheckForElevatedTask;
end.
And support unit itself:
unit RunElevatedSupport;
{$WARN SYMBOL_PLATFORM OFF}
{$R+}
interface
uses
Windows;
type
TElevatedProc = function(const AParameters: String): Cardinal;
TProcessMessagesMeth = procedure of object;
var
// Warning: this function will be executed in external process.
// Do not use any global variables inside this routine!
// Use only supplied AParameters.
OnElevateProc: TElevatedProc;
// Call this routine after you have assigned OnElevateProc
procedure CheckForElevatedTask;
// Runs OnElevateProc under full administrator rights
function RunElevated(const AParameters: String; const AWnd: HWND = 0; const AProcessMessages: TProcessMessagesMeth = nil): Cardinal; overload;
function IsAdministrator: Boolean;
function IsAdministratorAccount: Boolean;
function IsUACEnabled: Boolean;
function IsElevated: Boolean;
procedure SetButtonElevated(const AButtonHandle: THandle);
implementation
uses
SysUtils, Registry, ShellAPI, ComObj;
const
RunElevatedTaskSwitch = '0CC5C50CB7D643B68CB900BF000FFFD5'; // some unique value, just a GUID with removed '[', ']', and '-'
function CheckTokenMembership(TokenHandle: THANDLE; SidToCheck: Pointer; var IsMember: BOOL): BOOL; stdcall; external advapi32 name 'CheckTokenMembership';
function RunElevated(const AParameters: String; const AWnd: HWND = 0; const AProcessMessages: TProcessMessagesMeth = nil): Cardinal; overload;
var
SEI: TShellExecuteInfo;
Host: String;
Args: String;
begin
Assert(Assigned(OnElevateProc), 'OnElevateProc must be assigned before calling RunElevated');
if IsElevated then
begin
if Assigned(OnElevateProc) then
Result := OnElevateProc(AParameters)
else
Result := ERROR_PROC_NOT_FOUND;
Exit;
end;
Host := ParamStr(0);
Args := Format('/%s %s', [RunElevatedTaskSwitch, AParameters]);
FillChar(SEI, SizeOf(SEI), 0);
SEI.cbSize := SizeOf(SEI);
SEI.fMask := SEE_MASK_NOCLOSEPROCESS;
{$IFDEF UNICODE}
SEI.fMask := SEI.fMask or SEE_MASK_UNICODE;
{$ENDIF}
SEI.Wnd := AWnd;
SEI.lpVerb := 'runas';
SEI.lpFile := PChar(Host);
SEI.lpParameters := PChar(Args);
SEI.nShow := SW_NORMAL;
if not ShellExecuteEx(#SEI) then
RaiseLastOSError;
try
Result := ERROR_GEN_FAILURE;
if Assigned(AProcessMessages) then
begin
repeat
if not GetExitCodeProcess(SEI.hProcess, Result) then
Result := ERROR_GEN_FAILURE;
AProcessMessages;
until Result <> STILL_ACTIVE;
end
else
begin
if WaitForSingleObject(SEI.hProcess, INFINITE) <> WAIT_OBJECT_0 then
if not GetExitCodeProcess(SEI.hProcess, Result) then
Result := ERROR_GEN_FAILURE;
end;
finally
CloseHandle(SEI.hProcess);
end;
end;
function IsAdministrator: Boolean;
var
psidAdmin: Pointer;
B: BOOL;
const
SECURITY_NT_AUTHORITY: TSidIdentifierAuthority = (Value: (0, 0, 0, 0, 0, 5));
SECURITY_BUILTIN_DOMAIN_RID = $00000020;
DOMAIN_ALIAS_RID_ADMINS = $00000220;
SE_GROUP_USE_FOR_DENY_ONLY = $00000010;
begin
psidAdmin := nil;
try
// Создаём SID группы админов для проверки
Win32Check(AllocateAndInitializeSid(SECURITY_NT_AUTHORITY, 2,
SECURITY_BUILTIN_DOMAIN_RID, DOMAIN_ALIAS_RID_ADMINS, 0, 0, 0, 0, 0, 0,
psidAdmin));
// Проверяем, входим ли мы в группу админов (с учётов всех проверок на disabled SID)
if CheckTokenMembership(0, psidAdmin, B) then
Result := B
else
Result := False;
finally
if psidAdmin <> nil then
FreeSid(psidAdmin);
end;
end;
{$R-}
function IsAdministratorAccount: Boolean;
var
psidAdmin: Pointer;
Token: THandle;
Count: DWORD;
TokenInfo: PTokenGroups;
HaveToken: Boolean;
I: Integer;
const
SECURITY_NT_AUTHORITY: TSidIdentifierAuthority = (Value: (0, 0, 0, 0, 0, 5));
SECURITY_BUILTIN_DOMAIN_RID = $00000020;
DOMAIN_ALIAS_RID_ADMINS = $00000220;
SE_GROUP_USE_FOR_DENY_ONLY = $00000010;
begin
Result := Win32Platform <> VER_PLATFORM_WIN32_NT;
if Result then
Exit;
psidAdmin := nil;
TokenInfo := nil;
HaveToken := False;
try
Token := 0;
HaveToken := OpenThreadToken(GetCurrentThread, TOKEN_QUERY, True, Token);
if (not HaveToken) and (GetLastError = ERROR_NO_TOKEN) then
HaveToken := OpenProcessToken(GetCurrentProcess, TOKEN_QUERY, Token);
if HaveToken then
begin
Win32Check(AllocateAndInitializeSid(SECURITY_NT_AUTHORITY, 2,
SECURITY_BUILTIN_DOMAIN_RID, DOMAIN_ALIAS_RID_ADMINS, 0, 0, 0, 0, 0, 0,
psidAdmin));
if GetTokenInformation(Token, TokenGroups, nil, 0, Count) or
(GetLastError <> ERROR_INSUFFICIENT_BUFFER) then
RaiseLastOSError;
TokenInfo := PTokenGroups(AllocMem(Count));
Win32Check(GetTokenInformation(Token, TokenGroups, TokenInfo, Count, Count));
for I := 0 to TokenInfo^.GroupCount - 1 do
begin
Result := EqualSid(psidAdmin, TokenInfo^.Groups[I].Sid);
if Result then
Break;
end;
end;
finally
if TokenInfo <> nil then
FreeMem(TokenInfo);
if HaveToken then
CloseHandle(Token);
if psidAdmin <> nil then
FreeSid(psidAdmin);
end;
end;
{$R+}
function IsUACEnabled: Boolean;
var
Reg: TRegistry;
begin
Result := CheckWin32Version(6, 0);
if Result then
begin
Reg := TRegistry.Create(KEY_READ);
try
Reg.RootKey := HKEY_LOCAL_MACHINE;
if Reg.OpenKey('\Software\Microsoft\Windows\CurrentVersion\Policies\System', False) then
if Reg.ValueExists('EnableLUA') then
Result := (Reg.ReadInteger('EnableLUA') <> 0)
else
Result := False
else
Result := False;
finally
FreeAndNil(Reg);
end;
end;
end;
function IsElevated: Boolean;
const
TokenElevation = TTokenInformationClass(20);
type
TOKEN_ELEVATION = record
TokenIsElevated: DWORD;
end;
var
TokenHandle: THandle;
ResultLength: Cardinal;
ATokenElevation: TOKEN_ELEVATION;
HaveToken: Boolean;
begin
if CheckWin32Version(6, 0) then
begin
TokenHandle := 0;
HaveToken := OpenThreadToken(GetCurrentThread, TOKEN_QUERY, True, TokenHandle);
if (not HaveToken) and (GetLastError = ERROR_NO_TOKEN) then
HaveToken := OpenProcessToken(GetCurrentProcess, TOKEN_QUERY, TokenHandle);
if HaveToken then
begin
try
ResultLength := 0;
if GetTokenInformation(TokenHandle, TokenElevation, #ATokenElevation, SizeOf(ATokenElevation), ResultLength) then
Result := ATokenElevation.TokenIsElevated <> 0
else
Result := False;
finally
CloseHandle(TokenHandle);
end;
end
else
Result := False;
end
else
Result := IsAdministrator;
end;
procedure SetButtonElevated(const AButtonHandle: THandle);
const
BCM_SETSHIELD = $160C;
var
Required: BOOL;
begin
if not CheckWin32Version(6, 0) then
Exit;
if IsElevated then
Exit;
Required := True;
SendMessage(AButtonHandle, BCM_SETSHIELD, 0, LPARAM(Required));
end;
procedure CheckForElevatedTask;
function GetArgsForElevatedTask: String;
function PrepareParam(const ParamNo: Integer): String;
begin
Result := ParamStr(ParamNo);
if Pos(' ', Result) > 0 then
Result := AnsiQuotedStr(Result, '"');
end;
var
X: Integer;
begin
Result := '';
for X := 1 to ParamCount do
begin
if (AnsiUpperCase(ParamStr(X)) = ('/' + RunElevatedTaskSwitch)) or
(AnsiUpperCase(ParamStr(X)) = ('-' + RunElevatedTaskSwitch)) then
Continue;
Result := Result + PrepareParam(X) + ' ';
end;
Result := Trim(Result);
end;
var
ExitCode: Cardinal;
begin
if not FindCmdLineSwitch(RunElevatedTaskSwitch) then
Exit;
ExitCode := ERROR_GEN_FAILURE;
try
if not IsElevated then
ExitCode := ERROR_ACCESS_DENIED
else
if Assigned(OnElevateProc) then
ExitCode := OnElevateProc(GetArgsForElevatedTask)
else
ExitCode := ERROR_PROC_NOT_FOUND;
except
on E: Exception do
begin
if E is EAbort then
ExitCode := ERROR_CANCELLED
else
if E is EOleSysError then
ExitCode := Cardinal(EOleSysError(E).ErrorCode)
else
if E is EOSError then
else
ExitCode := ERROR_GEN_FAILURE;
end;
end;
if ExitCode = STILL_ACTIVE then
ExitCode := ERROR_GEN_FAILURE;
TerminateProcess(GetCurrentProcess, ExitCode);
end;
end.

Answer 4

Usually, putting the text "Setup" or "Install" somewhere in your EXE name is enough to make Windows run with elevated privileges automatically, and is well worth doing if it is a setup utility you are writing, as it's so easy to do.
I am now running into problems though on Windows 7, when not logged in as an Administrator, and am having to use the right-click Run As Administrator when running manually (running the program via Wise installation wizard is still fine)
I see though that Delphi 10.1 Berlin has a very easy to use new option under Project Options | Application. Just tick Enable Administrator Privileges, and the manifest is done for you, so easy!
NB. make sure you only do these kind of changes via a separate setup program, running your application with elevated privileges all the time can cause problems with other things, for example e-mail, where the default mail profile no longer gets picked up.
Edit: Jan 2018: since writing this answer in August 2017, it seems a lot of Windows updates have come out, that now require the user to right-click and Run As Administrator on just about everything, even on installation exe's built with Wise. Even Outlook is no longer installing properly without running as administrator. There is no more automated elevation at all it seems.