Category Archives: Living off the land

RunDll Exporters

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One of the most interesting classes of functions that are exported by DLLs are functions that use the RunDll interface (this archived article describes it).

Thanks to traditional (today kinda old-school) programming conventions, many coders name their exported functions compatible with the RunDll interface in a way that makes them easy to identify. Basically, they often include the reference to ‘rundll’ in a function name.

Knowing that, we can make an attempt to comb through many ‘good’ DLLs to discover a list of libraries where some of the APIs they export… follow this simple naming convention. Analysis of my small DLL repo gave me the results shown below.

Looking at these results I can immediately see that some of them are very familiar Windows API names (f.ex. Control_RunDLL variants), but there are many others that are mostly unknown. And many of libraries that export these functions come from other vendors than Microsoft, the exported APIs have almost no documentation and a minimalistic footprint online – basically, googling some of them brings very limited results.

I have a gut feeling that at least some of them are good lolbin potentials.

549  _InfEngUnInstallINFFile_RunDLL@16
485  InfEngUnInstallINFFile_RunDLL
426  RunDLLEntryW
353  RunDll32Interface
252  ShowHidPropPageRunDll32
252  BluetoothUpdateSendToRunDll32
195  DelNodeRunDLL32
167  RunDLL32EP
133  ShowHidPropPageRunDll32W
132  UninstADrvRunDll
114  Rundll_Dial
 62  RunDLLEntry
 62  Control_RunDLL
 60  SHHelpShortcuts_RunDLL
 60  PrintersGetCommand_RunDLL
 60  OpenAs_RunDLL
 58  SRS_InitializeEndpoints_Rundll32
 58  SRS_CleanupEndpoints_Rundll32
 58  SHHelpShortcuts_RunDLLW
 58  SHHelpShortcuts_RunDLLA
 58  PrintersGetCommand_RunDLLW
 58  PrintersGetCommand_RunDLLA
 58  OpenAs_RunDLLW
 58  OpenAs_RunDLLA
 58  Control_RunDLLW
 58  Control_RunDLLA
 54  RunDllDoPreInstall
 54  Control_FillCache_RunDLL
 52  Control_FillCache_RunDLLW
 52  Control_FillCache_RunDLLA
 50  BTINS_RunDll
 46  _RunDLLEntry@16
 41  ShellExec_RunDLLW
 41  ShellExec_RunDLLA
 41  ShellExec_RunDLL
 41  CplRunDll32
 41  Control_RunDLLAsUserW
 40  RunDll
 39  RunDllW
 38  SHCreateLocalServerRunDll
 38  Options_RunDLLW
 38  Options_RunDLLA
 38  Options_RunDLL
 38  AppCompat_RunDLLW
 32  Activate_RunDLL
 30  RunDll32ShimW
 30  HomeNetWizardRunDll
 25  TestRunDll
 24  ctCVWUtilityRunDLL32EP
 24  ctCVWIntroRunDLL32EP
 24  RundllUninstallA
 24  RundllInstallA
 23  ctCVWConsoleRunDLL32EP
 22  ctCVWParentalRunDLL32EP
 22  RunDllPromptForReboot
 20  SetupRunDll32Entry
 20  SelectSetupRunDll32Ex
 20  RunDllRegister
 19  UpgradePrinterRunDll32Ex
 18  RunDLL_InstallOEMDeviceEx
 18  RunDLL_InstallOEMDevice
 17  DelNodeRunDLL32W
 17  DelNodeRunDLL32A
 16  RunDLL_ExtractCabinetFile
 16  RunDLL32_UnregisterApplication
 16  RunDLL32_RegisterApplication
 16  RunDLL32_FilterRunOnceExRegistration
 15  RunDllEntryPoint
 13  SxsRunDllInstallAssemblyW
 13  SxsRunDllInstallAssembly
 12  IID_IShellRunDll
 11  usb_uninstall_service_np_rundll
 11  usb_install_service_np_rundll
 11  usb_install_driver_np_rundll
 11  TestPrint_RunDLLW
 11  RunDLL_InstallMultipleOEMDevicesEx
 11  @Jvjclutils@RunDll32Internal$qqruix17System@AnsiStringt2t2i
 11  @Jvjclutils@RunDLL32$qqrx17System@AnsiStringt1t1oi
 10  usb_touch_inf_file_np_rundll
  9  @Registryscan@TRegistryScan@HandleRundll32$qqr17System@AnsiStringo
  9  @PRunDLLCommand@saveGuts$xqr6RWFile
  9  @PRunDLLCommand@restoreGuts$qr6RWFile
  9  @PRunDLLCommand@newSpecies$xqv
  9  @PRunDLLCommand@myAtom
  9  @PRunDLLCommand@isA$xqv
  9  @PRunDLLCommand@copy$xqv
  9  @PRunDLLCommand@classIsA$qv
  9  @PRunDLLCommand@binaryStoreSize$xqv
  9  @PRunDLLCommand@UnExecute$qv
  9  @PRunDLLCommand@SetThirdParam$qrx9RWCString
  9  @PRunDLLCommand@SetSecondParam$qrx9RWCString
  9  @PRunDLLCommand@SetFunctionType$q12ERunDLLTypes
  9  @PRunDLLCommand@SetFunctionName$qrx9RWCString
  9  @PRunDLLCommand@SetFirstParam$qrx9RWCString
  9  @PRunDLLCommand@SetDLLName$qrx9RWCString
  9  @PRunDLLCommand@GetVersion$xqv
  9  @PRunDLLCommand@GetThirdParam$xqv
  9  @PRunDLLCommand@GetSecondParam$xqv
  9  @PRunDLLCommand@GetFunctionType$xqv
  9  @PRunDLLCommand@GetFunctionName$xqv
  9  @PRunDLLCommand@GetFirstParam$xqv
  9  @PRunDLLCommand@GetDLLReturnValue$xqv
  9  @PRunDLLCommand@GetDLLName$xqv
  9  @PRunDLLCommand@Execute$qv
  9  @PRunDLLCommand@$beql$xqrx11MPersistent
  9  @PRunDLLCommand@$bdtr$qv
  9  @PRunDLLCommand@$bctr$qv
  9  @PRunDLLCommand@$bctr$qrx14PRunDLLCommand
  9  @PRunDLLCommand@$basg$qrx14PRunDLLCommand
  8  _Java_com_sun_java_accessibility_AccessBridge_runDLL@8
  8  InstallSecurityPromptRunDllW
  8  DeviceProperties_RunDLLW
  8  DeviceProperties_RunDLLA
  7  DriverStoreRunDllW
  7  DeviceProblenWizard_RunDLLW
  7  DeviceProblenWizard_RunDLLA
  7  ?runDll@SV_HttpdAPI@@AAE_NPBD@Z
  6  extract_RunDLL
  6  WOW64Uninstall_RunDLLW
  6  UsersRunDll
  6  SxspRunDllDeleteDirectoryW
  6  SxspRunDllDeleteDirectory
  6  S3Disp_RunDll
  6  Rundll32RegisterServer
  6  RunDllProcW
  6  RunDllProcA
  6  RunDllEntry
  6  RunAsNewUser_RunDLLW
  6  PrepareDiscForBurnRunDllW
  6  LaunchMSHelp_RunDLLW
  6  AddNetPlaceRunDll
  6  @Jcldotnet@RunDll32ShimW$qqsxuixuipbxi
  5  RunDll_SetDefaultPrinter
  5  RunDll32Main
  5  PublishRunDll
  5  PassportWizardRunDll
  5  CscPolicyProcessing_RunDLLW
  5  CSCOptions_RunDLLW
  5  CSCOptions_RunDLLA
  5  CSCOptions_RunDLL
  4  update_start_rundll_old
  4  update_start_rundll
  4  uninstall_start_rundll_old
  4  uninstall_start_rundll
  4  rundll32_shellexec
  4  Wizard_RunDLL
  4  Rundll_EntryPoint
  4  DiskCopyRunDllW
  4  DiskCopyRunDll
  4  CI3_CreateShortcut_RUNDLL_32
  3  fnRunDll32
  3  _rundll32_shellexec@16
  3  WdipLaunchRunDLLUserHost
  3  Rundll32
  3  RunDll_UpdateDriver
  3  RunDll_Reenumerate
  3  RunDllHardwareTest
  3  RunDllA
  3  News_RunDLL
  3  NdfRunDllHelpTopic
  3  NdfRunDllDuplicateIPOffendingSystem
  3  NdfRunDllDuplicateIPDefendingSystem
  3  NdfRunDllDiagnoseWithAnswerFile
  3  NdfRunDllDiagnoseNetConnectionIncident
  3  NdfRunDllDiagnoseIncident
  3  Mail_RunDLL
  3  LogOffRunDLL
  3  Java_com_sun_java_accessibility_AccessBridge_runDLL
  3  CreateRegWizard_RunDll
  3  BoxedAppSDK_RunDll32_Callback
  2  rundll_analyze
  2  rundllIsAdmin
  2  _RunDll
  2  _RunDLLReport@16
  2  ShowRunDLLW
  2  ShowRunDLL
  2  ServiceRunDll
  2  RunDll32
  2  RunDLL_SaveImageFile
  2  RunDLL_RemoveDevice
  2  RunDLL_MountFileW
  2  RunDLL_MountFile
  2  RunDLL_DoCleanupW
  2  RunDLL_DoCleanupA
  2  RunDLLReport
  2  NotifyDevicesNeedRebootRunDllW
  2  ICRemoveByRundll
  2  ICInstallByRundll
  2  GetRunDllModule
  2  FromRunDll
  2  DllUnregisterServer_RunDll
  2  DllRegisterServer_RunDll
  2  DllIsRegisterServer_RunDll
  1  rundll_install_npq2f_srv2003
  1  rundll_install_npq2f
  1  rundll_install_ex
  1  rundll_install
  1  rundll_config
  1  dtuSerialRunDll
  1  dpuRunDllXML
  1  _RunDLL_SaveImageFile@16
  1  _RunDLL_RemoveDevice@16
  1  _RunDLL_MountFileW@16
  1  _RunDLL_MountFile@16
  1  UsersRunDllW
  1  Rundll32Call
  1  RunDllUnregisterMAPI
  1  RunDllRegisterMAPI
  1  RunDllInterfaceW
  1  RunDLLCommand
  1  RunDLL
  1  RegisterRunDll
  1  NetAccWizRunDll
  1  MigrateRunDll32
  1  ManageCardSpace_RunDll
  1  InstallReg_RunDLL
  1  ImportInformationCard_RunDllW
  1  ImportInformationCard_RunDllA

I don’t include sample hashes this time as I don’t want to make your life easier.

DLL ForwardSideloading, Part 2

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The 2nd part following my first take on this subject was kinda inevitable.

Why?

Sixtyvividtails is one of my fav researchers, because a) he reads my posts, breaks them apart, and usually comes up with some amazing/creative comments/additional thoughts that often lead us to some new, cool discoveries (see f.ex. this) b) he also made a social media bet that I (obviously) couldn’t leave unchallenged. Thank you Sixtyvividtails, you are an inspiration and I love your research and creative ideas a lot!

So, to business…

My first find was this unsigned Realtek DLL (RealWoWDLL.dll – VT Link) that exported the intriguing forward:

testker -> kerberos.Spinitialize

Then… I went for holidays 🙂

I did go there with an idea though that after coming back I will do a more structured follow-up research…

So when I came back, I immediately got to work.

The first target was an obvious one – run the very same forwarder-extractor script over the Windows 2025 server files. The results are here. Many of these combos can be used for DLL ForwardSideloading.

The second target was bigger. I checked my repo of ‘good’ files only to discover that I am sitting on around 700K ‘clean’ DLLs, both 32- and 64-bit. Sadly, I don know which ones of them are truly signed or not, unless the actual PE file of the DLL is physically signed (aka not via a catalogue). Still, 700K files is a lot, and there is a hope that it’s worth analyzing them all to see how many of them are non-Microsoft, and actually use/leverage the forwarded exports…

So, I ran my script over the last weekend and after few days it spat out its results.

And here’s the catch:

  • yes, some vendors do appear to be using forwarded functions same as Microsoft and Realtek
  • many functions that have their names exported by DLLs (mapping present in the export table) are not necessarily meant to be used by any other program, but since some do include a “.” character in their name, they could actually be used to facilitate DLL ForwardSideloading !

See the (filtered) results here.