reimplement exeption.rs

[sha0coder]

• Support the three typical exceptions handling systems of windows (SEH, VEH and UEF)

  • SEH: structured exception handler (try/catch, stack items)

  • VEH: vectorized exception handler (API) ntdll!RtlAddVectoredExceptionHandler ntdll!RtlRemoveVectoredExceptionHandler

  • UEF: unhandled exception filter (API) ntdll!RtlSetUnhandledExceptionFilter kernelbase!SetUnhandledExceptionFilter

• implement also the tests to trigger different types of handlers and also resume the execution:

  • exception_handler32
  • exception_handler64

• rename emu.feh to emu.uef for the unhandled exception filter

• implement missing winapis to schedule or free the exception handler.

note: The VEH was totally ok in theory, in the past I tested it with a chunk of guloader.

[sha0coder]

        If the handler return the search constant will jump to next handler in this order:
            VEH -> SEH1 -> SEH2 -> ... -> SEHn -> UEF -> terminate process


        unhandling:
            VEH:
                - the api RemoveVectoredExceptionHandler removes the handler
            SEH:
                - automatically when is triggered. SEH point to next SEH.
            UEF:
                - SetUnhandledExceptionFilter updates the handler


        Responses:

            VEH:
                - EXCEPTION_CONTINUE_EXECUTION (continue to eip/rip which could be modified)
                - EXCEPTION_CONTINUE_SEARCH (jump to next handler SEH -> UEF -> end proces)

            SEH:
                - EXCEPTION_CONTINUE_EXECUTION (continue and not jump to except)
                - EXCEPTION_CONTINUE_SEARCH (jump to next handler SEH -> UEF -> end process)
                - EXCEPTION_EXECUTE_HANDLER (jump to except)

            UEF:
                - EXCEPTION_CONTINUE_EXECUTION (continue to eip/rip which could be modified)
                - EXCEPTION_CONTINUE_SEARCH (end process)

        64bits SEH:
            - is not a stack chain
            - search RUNTIME_FUNCTION entry in the .pdata table using BeginAddress ≤ RIP < EndAddress
            - in that entry there is the RVA of UNWIND_INFO struct on the .xdata


            - at .pdata, 12 bytes of runtime entries:

                typedef struct _RUNTIME_FUNCTION {
                    DWORD BeginAddress;
                    DWORD EndAddress;
                    DWORD UnwindInfo;    // RVA to UNWIND_INFO at .xdata
                } RUNTIME_FUNCTION, *PRUNTIME_FUNCTION;

            - unwind info in the .xdata:

                typedef struct _UNWIND_INFO {
                    UBYTE Version : 3;   // always 1
                    UBYTE Flags   : 5;   // 0, EHANDLER, UHANDLER, etc.
                    UBYTE SizeOfProlog;
                    UBYTE CountOfCodes;  // Nº of UNWIND_CODE
                    UBYTE FrameRegister : 4; // (ie. RBP=5)
                    UBYTE FrameOffset   : 4; // frame scale
                    UNWIND_CODE UnwindCode[]; // descriptors
                    // opcional:
                    //  DWORD ExceptionHandler;   // RVA to handler if Flags indicate it
                    //  DWORD ExceptionData[];    // extra data for handler
                } UNWIND_INFO, *PUNWIND_INFO;