BUILD: Make Windows installer run unprivileged for non-admin users

1 files changed, 137 insertions, 6 deletions

diff --git a/dists/win32/ScummVM.iss b/dists/win32/ScummVM.iss
index e85975f108..38745c885a 100644
--- a/dists/win32/ScummVM.iss
+++ b/dists/win32/ScummVM.iss
@@ -1,18 +1,20 @@
+#define AppName "ScummVM"
+
 [Setup]
 AppCopyright=2018
-AppName=ScummVM
-AppVerName=ScummVM Git
+AppName={#AppName}
+AppVerName={#AppName} Git
 AppPublisher=The ScummVM Team
 AppPublisherURL=http://www.scummvm.org/
 AppSupportURL=http://www.scummvm.org/
 AppUpdatesURL=http://www.scummvm.org/
-DefaultDirName={pf}\ScummVM
-DefaultGroupName=ScummVM
+DefaultDirName={pf}\{#AppName}
+DefaultGroupName={#AppName}
 AllowNoIcons=true
 AlwaysUsePersonalGroup=false
 EnableDirDoesntExistWarning=false
 Compression=lzma
-OutputDir=C:\ScummVM
+OutputDir=C:\{#AppName}
 OutputBaseFilename=scummvm-win32
 DisableStartupPrompt=true
 AppendDefaultDirName=false
@@ -22,7 +24,136 @@ SetupIconFile=graphics\scummvm-install.ico
 WizardImageFile=graphics\left.bmp
 ShowLanguageDialog=yes
 LanguageDetectionMethod=uilanguage
-PrivilegesRequired=lowest
+PrivilegesRequired=none
+
+; This privilege escalation code comes from
+; https://stackoverflow.com/a/35435534/252087
+
+#define InnoSetupReg \
+  "Software\Microsoft\Windows\CurrentVersion\Uninstall\" + AppName + "_is1"
+#define InnoSetupAppPathReg "Inno Setup: App Path"
+
+[Code]
+function IsWinVista: Boolean;
+begin
+  Result := (GetWindowsVersion >= $06000000);
+end;
+
+function IsElevated: Boolean;
+begin
+  Result := IsAdminLoggedOn or IsPowerUserLoggedOn;
+end;
+
+function HaveWriteAccessToApp: Boolean;
+var
+  FileName: string;
+begin
+  FileName := AddBackslash(WizardDirValue) + 'writetest.tmp';
+  Result := SaveStringToFile(FileName, 'test', False);
+  if Result then
+  begin
+    Log(Format(
+      'Have write access to the last installation path [%s]', [WizardDirValue]));
+    DeleteFile(FileName);
+  end
+    else
+  begin
+    Log(Format('Does not have write access to the last installation path [%s]', [
+      WizardDirValue]));
+  end;
+end;
+
+procedure ExitProcess(uExitCode: UINT);
+  external 'ExitProcess@kernel32.dll stdcall';
+function ShellExecute(hwnd: HWND; lpOperation: string; lpFile: string;
+  lpParameters: string; lpDirectory: string; nShowCmd: Integer): THandle;
+  external 'ShellExecuteW@shell32.dll stdcall';
+
+function Elevate: Boolean;
+var
+  I: Integer;
+  RetVal: Integer;
+  Params: string;
+  S: string;
+begin
+  { Collect current instance parameters }
+  for I := 1 to ParamCount do
+  begin
+    S := ParamStr(I);
+    { Unique log file name for the elevated instance }
+    if CompareText(Copy(S, 1, 5), '/LOG=') = 0 then
+    begin
+      S := S + '-elevated';
+    end;
+    { Do not pass our /SL5 switch }
+    if CompareText(Copy(S, 1, 5), '/SL5=') <> 0 then
+    begin
+      Params := Params + AddQuotes(S) + ' ';
+    end;
+  end;
+
+  { ... and add selected language }
+  Params := Params + '/LANG=' + ActiveLanguage;
+
+  Log(Format('Elevating setup with parameters [%s]', [Params]));
+  RetVal := ShellExecute(0, 'runas', ExpandConstant('{srcexe}'), Params, '', SW_SHOW);
+  Log(Format('Running elevated setup returned [%d]', [RetVal]));
+  Result := (RetVal > 32);
+  { if elevated executing of this setup succeeded, then... }
+  if Result then
+  begin
+    Log('Elevation succeeded');
+    { exit this non-elevated setup instance }
+    ExitProcess(0);
+  end
+    else
+  begin
+    Log(Format('Elevation failed [%s]', [SysErrorMessage(RetVal)]));
+  end;
+end;
+
+procedure InitializeWizard;
+var
+  S: string;
+  Upgrade: Boolean;
+begin
+  Upgrade :=
+    RegQueryStringValue(HKLM, '{#InnoSetupReg}', '{#InnoSetupAppPathReg}', S) or
+    RegQueryStringValue(HKCU, '{#InnoSetupReg}', '{#InnoSetupAppPathReg}', S);
+
+  { elevate }
+
+  if not IsWinVista then
+  begin
+    Log(Format('This version of Windows [%x] does not support elevation', [
+      GetWindowsVersion]));
+  end
+    else
+  if IsElevated then
+  begin
+    Log('Running elevated');
+  end
+    else
+  begin
+    Log('Running non-elevated');
+    if Upgrade then
+    begin
+      if not HaveWriteAccessToApp then
+      begin
+        Elevate;
+      end;
+    end
+      else
+    begin
+      if not Elevate then
+      begin
+        WizardForm.DirEdit.Text := ExpandConstant('{localappdata}\{#AppName}');
+        Log(Format('Falling back to local application user folder [%s]', [
+          WizardForm.DirEdit.Text]));
+      end;
+    end;
+  end;
+end;
 
 [Languages]
 Name: en; MessagesFile: compiler:Default.isl