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[msvc] add provision to prevent DLL search order hijacking through delay loading

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* Hypothetically if the user's current directory contains a malicious DLL that DLL
  could be loaded instead of the one in System32.
* Whereas the previous patch should have taken care of the one DLL referenced by
  Rufus that may be vulnerable to this attack (version.dll), we nonetheless add
  delay loading for all the libraries we reference as a precautionary measure.
* One can confirm that this works by using dumpbin.exe /IMPORTS to make sure
  a specific DLL is delay loaded. Then putting a breakpoint in the delay load
  hook should also confirm that the hook is used.
* Closes #1838
This commit is contained in:
Austin Wise 2021-12-11 16:57:26 -08:00 committed by Pete Batard
parent f6ac559f4d
commit ef2ff7179d
No known key found for this signature in database
GPG key ID: 38E0CF5E69EDD671
3 changed files with 37 additions and 20 deletions
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8
.vs/rufus.vcxproj
View file

@ -133,11 +133,12 @@
<AdditionalOptions>/utf-8 $(ExternalCompilerOptions) %(AdditionalOptions)</AdditionalOptions>
</ClCompile>
<Link>
<AdditionalDependencies>advapi32.lib;comctl32.lib;comdlg32.lib;crypt32.lib;gdi32.lib;ole32.lib;setupapi.lib;shell32.lib;shlwapi.lib;wintrust.lib;psapi.lib;%(AdditionalDependencies)</AdditionalDependencies>
<AdditionalDependencies>advapi32.lib;comctl32.lib;comdlg32.lib;crypt32.lib;gdi32.lib;ole32.lib;setupapi.lib;shell32.lib;shlwapi.lib;wintrust.lib;%(AdditionalDependencies)</AdditionalDependencies>
<UACExecutionLevel>RequireAdministrator</UACExecutionLevel>
<GenerateDebugInformation>true</GenerateDebugInformation>
<SubSystem>Windows</SubSystem>
<TargetMachine>MachineX86</TargetMachine>
<DelayLoadDLLs>advapi32.dll;comctl32.dll;comdlg32.dll;crypt32.dll;gdi32.dll;ole32.dll;setupapi.dll;shell32.dll;shlwapi.dll;wintrust.dll;%(DelayLoadDLLs)</DelayLoadDLLs>
</Link>
<ResourceCompile>
<PreprocessorDefinitions>_UNICODE;UNICODE;RUFUS_LOC;%(PreprocessorDefinitions)</PreprocessorDefinitions>
@ -162,6 +163,7 @@
<GenerateDebugInformation>true</GenerateDebugInformation>
<SubSystem>Windows</SubSystem>
<AdditionalLibraryDirectories>C:\Program Files (x86)\Windows Kits\10\Lib\10.0.15063.0\um\arm</AdditionalLibraryDirectories>
<DelayLoadDLLs>advapi32.dll;comctl32.dll;comdlg32.dll;crypt32.dll;gdi32.dll;ole32.dll;setupapi.dll;shell32.dll;shlwapi.dll;wintrust.dll;ole32.dll;advapi32.dll;gdi32.dll;shell32.dll;comdlg32.dll;%(DelayLoadDLLs)</DelayLoadDLLs>
</Link>
<ResourceCompile>
<PreprocessorDefinitions>_UNICODE;UNICODE;RUFUS_LOC;%(PreprocessorDefinitions)</PreprocessorDefinitions>
@ -188,6 +190,7 @@
<GenerateDebugInformation>true</GenerateDebugInformation>
<SubSystem>Windows</SubSystem>
<AdditionalLibraryDirectories>C:\Program Files (x86)\Windows Kits\10\Lib\10.0.16299.0\um\arm64</AdditionalLibraryDirectories>
<DelayLoadDLLs>advapi32.dll;comctl32.dll;comdlg32.dll;crypt32.dll;gdi32.dll;ole32.dll;setupapi.dll;shell32.dll;shlwapi.dll;wintrust.dll;ole32.dll;advapi32.dll;gdi32.dll;shell32.dll;comdlg32.dll;%(DelayLoadDLLs)</DelayLoadDLLs>
</Link>
<ResourceCompile>
<PreprocessorDefinitions>_UNICODE;UNICODE;RUFUS_LOC;%(PreprocessorDefinitions)</PreprocessorDefinitions>
@ -214,11 +217,12 @@
<AdditionalOptions>/utf-8 $(ExternalCompilerOptions) %(AdditionalOptions)</AdditionalOptions>
</ClCompile>
<Link>
<AdditionalDependencies>advapi32.lib;comctl32.lib;comdlg32.lib;crypt32.lib;gdi32.lib;ole32.lib;setupapi.lib;shell32.lib;shlwapi.lib;wintrust.lib;psapi.lib;%(AdditionalDependencies)</AdditionalDependencies>
<AdditionalDependencies>advapi32.lib;comctl32.lib;comdlg32.lib;crypt32.lib;gdi32.lib;ole32.lib;setupapi.lib;shell32.lib;shlwapi.lib;wintrust.lib;%(AdditionalDependencies)</AdditionalDependencies>
<UACExecutionLevel>RequireAdministrator</UACExecutionLevel>
<GenerateDebugInformation>true</GenerateDebugInformation>
<SubSystem>Windows</SubSystem>
<TargetMachine>MachineX64</TargetMachine>
<DelayLoadDLLs>advapi32.dll;comctl32.dll;comdlg32.dll;crypt32.dll;gdi32.dll;ole32.dll;setupapi.dll;shell32.dll;shlwapi.dll;wintrust.dll;%(DelayLoadDLLs)</DelayLoadDLLs>
</Link>
<ResourceCompile>
<PreprocessorDefinitions>_UNICODE;UNICODE;RUFUS_LOC;%(PreprocessorDefinitions)</PreprocessorDefinitions>

39
src/rufus.c
View file

@ -36,6 +36,7 @@
#include <io.h>
#include <getopt.h>
#include <assert.h>
#include <delayimp.h>
#include "rufus.h"
#include "missing.h"
@ -3191,6 +3192,23 @@ static HANDLE SetHogger(void)
return hogmutex;
}
// For delay-loaded DLLs, use LOAD_LIBRARY_SEARCH_SYSTEM32 to avoid DLL search order hijacking.
FARPROC WINAPI dllDelayLoadHook(unsigned dliNotify, PDelayLoadInfo pdli)
{
if (dliNotify == dliNotePreLoadLibrary) {
// Windows 7 without KB2533623 does not support the LOAD_LIBRARY_SEARCH_SYSTEM32 flag.
// That is is OK, because the delay load handler will interrupt the NULL return value
// to mean that it should perform a normal LoadLibrary.
return (FARPROC)LoadLibraryExA(pdli->szDll, NULL, LOAD_LIBRARY_SEARCH_SYSTEM32);
}
return NULL;
}
#if defined(_MSC_VER)
// By default the Windows SDK headers have a `const` while MinGW does not.
const
#endif
PfnDliHook __pfnDliNotifyHook2 = dllDelayLoadHook;
/*
* Application Entrypoint
@ -3202,7 +3220,6 @@ int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine
#endif
{
const char* rufus_loc = "rufus.loc";
wchar_t kernel32_path[MAX_PATH];
int i, opt, option_index = 0, argc = 0, si = 0, lcid = GetUserDefaultUILanguage();
int wait_for_mutex = 0;
FILE* fd;
@ -3238,22 +3255,18 @@ int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine
// Still, we invoke it, for platforms where the following call might actually work...
SetDllDirectoryA("");
// Also, even if you use SetDefaultDllDirectories(LOAD_LIBRARY_SEARCH_SYSTEM32), you're
// still going to be brought down if you link to wininet.lib or dwmapi.lib, as these two
// perform their DLL invocations before you've had a chance to execute anything.
// Of course, this is not something that security "researchers" will bother looking into
// to try to help fellow developers, when they can get an ego fix by simply throwing
// generic URLs around and deliberately refusing to practice *responsible disclosure*...
// For libraries on the KnownDLLs list, the system will always load them from System32.
// For other DLLs we link directly to, we can delay load the DLL and use a delay load
// hook to load them from System32. Note that, for this to work, something like:
// 'somelib.dll;%(DelayLoadDLLs)' must be added to the 'Delay Loaded Dlls' option of
// the linker properties in Visual Studio (which means this won't work with MinGW).
// For all other DLLs, use SetDefaultDllDirectories(LOAD_LIBRARY_SEARCH_SYSTEM32).
// Finally, we need to perform the whole gymkhana below, where we can't call on
// SetDefaultDllDirectories() directly, because Windows 7 doesn't have the API exposed.
GetSystemDirectoryW(kernel32_path, ARRAYSIZE(kernel32_path));
wcsncat(kernel32_path, L"\\kernel32.dll", ARRAYSIZE(kernel32_path) - wcslen(kernel32_path) - 1);
// NB: Because kernel32 should already be loaded, what we do above to ensure that we
// (re)pick the system one is mostly unnecessary. But since for a hammer everything is a
// nail... Also, no, Coverity, we never need to care about freeing kernel32 as a library.
// Also, no, Coverity, we never need to care about freeing kernel32 as a library.
// coverity[leaked_storage]
pfSetDefaultDllDirectories = (SetDefaultDllDirectories_t)
GetProcAddress(LoadLibraryW(kernel32_path), "SetDefaultDllDirectories");
GetProcAddress(LoadLibraryW(L"kernel32.dll"), "SetDefaultDllDirectories");
if (pfSetDefaultDllDirectories != NULL)
pfSetDefaultDllDirectories(LOAD_LIBRARY_SEARCH_SYSTEM32);

10
src/rufus.rc
View file

@ -33,7 +33,7 @@ LANGUAGE LANG_NEUTRAL, SUBLANG_NEUTRAL
IDD_DIALOG DIALOGEX 12, 12, 232, 326
STYLE DS_SETFONT | DS_MODALFRAME | DS_CENTER | WS_MINIMIZEBOX | WS_POPUP | WS_CAPTION | WS_SYSMENU
EXSTYLE WS_EX_ACCEPTFILES
CAPTION "Rufus 3.18.1857"
CAPTION "Rufus 3.18.1858"
FONT 9, "Segoe UI Symbol", 400, 0, 0x0
BEGIN
LTEXT "Drive Properties",IDS_DRIVE_PROPERTIES_TXT,8,6,53,12,NOT WS_GROUP
@ -395,8 +395,8 @@ END
//
VS_VERSION_INFO VERSIONINFO
FILEVERSION 3,18,1857,0
PRODUCTVERSION 3,18,1857,0
FILEVERSION 3,18,1858,0
PRODUCTVERSION 3,18,1858,0
FILEFLAGSMASK 0x3fL
#ifdef _DEBUG
FILEFLAGS 0x1L
@ -414,13 +414,13 @@ BEGIN
VALUE "Comments", "https://rufus.ie"
VALUE "CompanyName", "Akeo Consulting"
VALUE "FileDescription", "Rufus"
VALUE "FileVersion", "3.18.1857"
VALUE "FileVersion", "3.18.1858"
VALUE "InternalName", "Rufus"
VALUE "LegalCopyright", "© 2011-2021 Pete Batard (GPL v3)"
VALUE "LegalTrademarks", "https://www.gnu.org/licenses/gpl-3.0.html"
VALUE "OriginalFilename", "rufus-3.18.exe"
VALUE "ProductName", "Rufus"
VALUE "ProductVersion", "3.18.1857"
VALUE "ProductVersion", "3.18.1858"
END
END
BLOCK "VarFileInfo"