syscall-sysret.cpp File Reference

!syscall and !sysret commands More...

#include "pch.h"

Functions
VOID	CommandSyscallHelp ()
	help of the !syscall command
VOID	CommandSysretHelp ()
	help of the !sysret command
VOID	CommandSyscallAndSysret (vector< CommandToken > CommandTokens, string Command)
	!syscall, !syscall2 and !sysret, !sysret2 commands handler

Detailed Description

!syscall and !sysret commands

Author

Sina Karvandi (sina@.nosp@m.hype.nosp@m.rdbg..nosp@m.org)

Version

0.1

Date

2020-05-27

Copyright

This project is released under the GNU Public License v3.

Function Documentation

CommandSyscallAndSysret()

VOID CommandSyscallAndSysret	(	vector< CommandToken >	CommandTokens,
		string	Command )

!syscall, !syscall2 and !sysret, !sysret2 commands handler

Parameters

CommandTokens
Command

Returns

VOID

{
    PDEBUGGER_GENERAL_EVENT_DETAIL     Event                 = NULL;
    PDEBUGGER_GENERAL_ACTION           ActionBreakToDebugger = NULL;
    PDEBUGGER_GENERAL_ACTION           ActionCustomCode      = NULL;
    PDEBUGGER_GENERAL_ACTION           ActionScript          = NULL;
    UINT32                             EventLength;
    UINT32                             ActionBreakToDebuggerLength = 0;
    UINT32                             ActionCustomCodeLength      = 0;
    UINT32                             ActionScriptLength          = 0;
    UINT64                             SpecialTarget               = DEBUGGER_EVENT_SYSCALL_ALL_SYSRET_OR_SYSCALLS;
    BOOLEAN                            GetSyscallNumber            = FALSE;
    DEBUGGER_EVENT_PARSING_ERROR_CAUSE EventParsingErrorCause;
    string                             Cmd;
 
    //
    // Interpret and fill the general event and action fields
    //
    //
    Cmd = GetLowerStringFromCommandToken(CommandTokens.at(0));
 
    if (!Cmd.compare("!syscall") || !Cmd.compare("!syscall2"))
    {
        if (!InterpretGeneralEventAndActionsFields(
                &CommandTokens,
                SYSCALL_HOOK_EFER_SYSCALL,
                &Event,
                &EventLength,
                &ActionBreakToDebugger,
                &ActionBreakToDebuggerLength,
                &ActionCustomCode,
                &ActionCustomCodeLength,
                &ActionScript,
                &ActionScriptLength,
                &EventParsingErrorCause))
        {
            return;
        }
    }
    else
    {
        if (!InterpretGeneralEventAndActionsFields(
                &CommandTokens,
                SYSCALL_HOOK_EFER_SYSRET,
                &Event,
                &EventLength,
                &ActionBreakToDebugger,
                &ActionBreakToDebuggerLength,
                &ActionCustomCode,
                &ActionCustomCodeLength,
                &ActionScript,
                &ActionScriptLength,
                &EventParsingErrorCause))
        {
            return;
        }
    }
 
    //
    // Interpret command specific details (if any)
    //
 
    //
    // Currently we do not support any extra argument for !sysret command
    // it is because we don't know how to find syscall number in sysret
    // and we don't wanna deal with dynamic mapping of rcx (user stack)
    // in vmx-root
    //
    if (!Cmd.compare("!syscall") || !Cmd.compare("!syscall2"))
    {
        for (auto Section : CommandTokens)
        {
            if (CompareLowerCaseStrings(Section, "!syscall") ||
                CompareLowerCaseStrings(Section, "!syscall2") ||
                CompareLowerCaseStrings(Section, "!sysret") ||
                CompareLowerCaseStrings(Section, "!sysret2"))
            {
                continue;
            }
 
            else if (!GetSyscallNumber)
            {
                //
                // It's probably a syscall address
                //
                if (!SymbolConvertNameOrExprToAddress(
                        GetCaseSensitiveStringFromCommandToken(Section),
                        &SpecialTarget))
                {
                    //
                    // Unknown parameter
                    //
                    ShowMessages("unknown parameter '%s'\n\n",
                                 GetCaseSensitiveStringFromCommandToken(Section).c_str());
 
                    if (!Cmd.compare("!syscall") || !Cmd.compare("!syscall2"))
                    {
                        CommandSyscallHelp();
                    }
                    else
                    {
                        CommandSysretHelp();
                    }
 
                    FreeEventsAndActionsMemory(Event, ActionBreakToDebugger, ActionCustomCode, ActionScript);
                    return;
                }
                else
                {
                    GetSyscallNumber = TRUE;
                }
            }
            else
            {
                //
                // Unknown parameter
                //
                ShowMessages("unknown parameter '%s'\n\n",
                             GetCaseSensitiveStringFromCommandToken(Section).c_str());
 
                if (!Cmd.compare("!syscall") || !Cmd.compare("!syscall2"))
                {
                    CommandSyscallHelp();
                }
                else
                {
                    CommandSysretHelp();
                }
 
                FreeEventsAndActionsMemory(Event, ActionBreakToDebugger, ActionCustomCode, ActionScript);
                return;
            }
        }
 
        //
        // Set the target syscall
        //
        Event->Options.OptionalParam1 = SpecialTarget;
    }
 
    //
    // Set whether it's !syscall or !syscall2 or !sysret or !sysret2
    //
    if (!Cmd.compare("!syscall2") || !Cmd.compare("!sysret2"))
    {
        //
        // It's a !syscall2 or !sysret2
        //
        Event->Options.OptionalParam2 = DEBUGGER_EVENT_SYSCALL_SYSRET_HANDLE_ALL_UD;
    }
    else
    {
        //
        // It's a !syscall or !sysret
        //
        Event->Options.OptionalParam2 = DEBUGGER_EVENT_SYSCALL_SYSRET_SAFE_ACCESS_MEMORY;
    }
 
    //
    // Send the ioctl to the kernel for event registration
    //
    if (!SendEventToKernel(Event, EventLength))
    {
        //
        // There was an error, probably the handle was not initialized
        // we have to free the Action before exit, it is because, we
        // already freed the Event and string buffers
        //
 
        FreeEventsAndActionsMemory(Event, ActionBreakToDebugger, ActionCustomCode, ActionScript);
        return;
    }
 
    //
    // Add the event to the kernel
    //
    if (!RegisterActionToEvent(Event,
                               ActionBreakToDebugger,
                               ActionBreakToDebuggerLength,
                               ActionCustomCode,
                               ActionCustomCodeLength,
                               ActionScript,
                               ActionScriptLength))
    {
        //
        // There was an error
        //
 
        FreeEventsAndActionsMemory(Event, ActionBreakToDebugger, ActionCustomCode, ActionScript);
        return;
    }
}

CommandSyscallHelp()

VOID CommandSyscallHelp

(

)

help of the !syscall command

Returns

VOID

{
    ShowMessages("!syscall : monitors and hooks all execution of syscall "
                 "instructions (by accessing memory and checking for instructions).\n\n");
    ShowMessages("!syscall2 : monitors and hooks all execution of syscall "
                 "instructions (by emulating all #UDs).\n\n");
 
    ShowMessages("syntax : \t!syscall [SyscallNumber (hex)] [pid ProcessId (hex)] [core CoreId (hex)] "
                 "[imm IsImmediate (yesno)] [sc EnableShortCircuiting (onoff)] [stage CallingStage (prepostall)] "
                 "[buffer PreAllocatedBuffer (hex)] [script { Script (string) }] [asm condition { Condition (assembly/hex) }] "
                 "[asm code { Code (assembly/hex) }] [output {OutputName (string)}]\n");
    ShowMessages("syntax : \t!syscall2 [SyscallNumber (hex)] [pid ProcessId (hex)] [core CoreId (hex)] "
                 "[imm IsImmediate (yesno)] [sc EnableShortCircuiting (onoff)] [stage CallingStage (prepostall)] "
                 "[buffer PreAllocatedBuffer (hex)] [script { Script (string) }] [asm condition { Condition (assembly/hex) }] "
                 "[asm code { Code (assembly/hex) }] [output {OutputName (string)}]\n");
 
    ShowMessages("\n");
    ShowMessages("\t\te.g : !syscall\n");
    ShowMessages("\t\te.g : !syscall2\n");
    ShowMessages("\t\te.g : !syscall 0x55\n");
    ShowMessages("\t\te.g : !syscall2 0x55\n");
    ShowMessages("\t\te.g : !syscall 0x55 pid 400\n");
    ShowMessages("\t\te.g : !syscall 0x55 core 2 pid 400\n");
    ShowMessages("\t\te.g : !syscall2 0x55 core 2 pid 400\n");
    ShowMessages("\t\te.g : !syscall script { printf(\"system-call num: %%llx, at process id: %%x\\n\", @rax, $pid); }\n");
    ShowMessages("\t\te.g : !syscall asm code { nop; nop; nop }\n");
}

CommandSysretHelp()

VOID CommandSysretHelp

(

)

help of the !sysret command

Returns

VOID

{
    ShowMessages("!sysret : monitors and hooks all execution of sysret "
                 "instructions (by accessing memory and checking for instructions).\n\n");
    ShowMessages("!sysret2 : monitors and hooks all execution of sysret "
                 "instructions (by emulating all #UDs).\n\n");
 
    ShowMessages("syntax : \t!sysret [pid ProcessId (hex)] [core CoreId (hex)] "
                 "[imm IsImmediate (yesno)] [sc EnableShortCircuiting (onoff)] [buffer PreAllocatedBuffer (hex)] "
                 "[script { Script (string) }] [asm condition { Condition (assembly/hex) }] [asm code { Code (assembly/hex) }]\n");
 
    ShowMessages("\n");
    ShowMessages("\t\te.g : !sysret\n");
    ShowMessages("\t\te.g : !sysret2\n");
    ShowMessages("\t\te.g : !sysret pid 400\n");
    ShowMessages("\t\te.g : !sysret2 pid 400\n");
    ShowMessages("\t\te.g : !sysret core 2 pid 400\n");
    ShowMessages("\t\te.g : !sysret2 core 2 pid 400\n");
    ShowMessages("\t\te.g : !sysret script { printf(\"SYSRET instruction is executed at process id: %%x\\n\", $pid); }\n");
    ShowMessages("\t\te.g : !sysret asm code { nop; nop; nop }\n");
}