{*******************************************************}
{                                                       }
{       ApiHookNet                                      }
{                                                       }
{       Copyright (C) 2023 kku                          }
{                                                       }
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unit ApiHookNet;

interface

uses
  Winapi.Windows, EM.Dnsapi, System.SysUtils;

const
  DNS_ERROR_RCODE_YXDOMAIN = $232E;

type
  TFun_DnsQuery_A = function(lpstrName: LPSTR; wType: WORD; fOptions: DWORD; aipServers: PDWORD;
                           var ppQueryResultsSet: PDWORD; pReserved:pdword): DWORD; stdcall;
  TFun_DnsQuery_UTF8 = function(lpstrName: LPSTR; wType: WORD; fOptions: DWORD; aipServers: PDWORD;
                           var ppQueryResultsSet: PDWORD; pReserved:pdword): DWORD; stdcall;
  TFun_DnsQuery_W = function(lpstrName: LPWSTR; wType: WORD; fOptions: DWORD; aipServers: PDWORD;
                           var ppQueryResultsSet: PDWORD; pReserved:pdword): DWORD; stdcall;
  TFun_DnsQueryEx = function(pQueryRequest: PDnsQueryRequest; pQueryResults, pCancelHandle: Pointer): DWORD; stdcall;

var
  ozDnsQuery_A: TFun_DnsQuery_A = nil;
  ozDnsQuery_UTF8: TFun_DnsQuery_UTF8 = nil;
  ozDnsQuery_W: TFun_DnsQuery_W = nil;
  ozDnsQueryEx: TFun_DnsQueryEx = nil;

implementation

function CheckBlockDomain(sDomain: String): Boolean;
begin
//  _AppHook.Log('CheckBlockDomain() ..');
  Result := Pos('google', LowerCase(sDomain)) > 0;
end;

function DnsQuery_AHook(lpstrName: LPSTR; wType: WORD; fOptions: DWORD; aipServers: PDWORD;
                        var ppQueryResultsSet: PDWORD; pReserved:pdword): DWORD; stdcall;
begin
  if CheckBlockDomain(StrPas(lpstrName)) then
    Result := DNS_ERROR_RCODE_YXDOMAIN
  else
    Result := ozDnsQuery_A(lpstrName, wType, fOptions, aipServers, ppQueryResultsSet, pReserved);
end;

function DnsQuery_UTF8Hook(lpstrName: LPSTR; wType: WORD; fOptions: DWORD; aipServers: PDWORD;
                           var ppQueryResultsSet: PDWORD; pReserved:pdword): DWORD; stdcall;
begin
  if CheckBlockDomain(StrPas(lpstrName)) then
    Result := DNS_ERROR_RCODE_YXDOMAIN
  else
    Result := ozDnsQuery_UTF8(lpstrName, wType, fOptions, aipServers, ppQueryResultsSet, pReserved);
end;

function DnsQuery_WHook(lpstrName: LPWSTR; wType: WORD; fOptions: DWORD; aipServers: PDWORD;
                           var ppQueryResultsSet: PDWORD; pReserved:pdword): DWORD; stdcall;
begin
  if CheckBlockDomain(StrPas(lpstrName)) then
    Result := DNS_ERROR_RCODE_YXDOMAIN
  else
    Result := ozDnsQuery_W(lpstrName, wType, fOptions, aipServers, ppQueryResultsSet, pReserved);
end;

function DnsQueryExHook(pQueryRequest: PDnsQueryRequest; pQueryResults, pCancelHandle: Pointer): DWORD; stdcall;
begin
  if CheckBlockDomain(StrPas(pQueryRequest.sQueryName)) then
    Result := ERROR_INVALID_PARAMETER
  else
    Result := ozDnsQueryEx(pQueryRequest, pQueryResults, pCancelHandle);
end;

end.