241 lines
4.7 KiB
C++
241 lines
4.7 KiB
C++
/*++
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Copyright (c) 2000-2002 Microsoft Corporation
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Module Name:
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EmulateEnvironmentBlock.cpp
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Abstract:
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Shrink the enviroment strings to avoid memory corruption experienced by
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some apps when they get a larger than expected enviroment.
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Notes:
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This is a general purpose shim.
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History:
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01/19/2001 linstev Created
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02/18/2002 mnikkel modified to use strsafe routines.
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--*/
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#include "precomp.h"
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IMPLEMENT_SHIM_BEGIN(EmulateEnvironmentBlock)
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#include "ShimHookMacro.h"
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APIHOOK_ENUM_BEGIN
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APIHOOK_ENUM_ENTRY(GetEnvironmentStrings)
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APIHOOK_ENUM_ENTRY(GetEnvironmentStringsA)
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APIHOOK_ENUM_ENTRY(GetEnvironmentStringsW)
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APIHOOK_ENUM_ENTRY(FreeEnvironmentStringsA)
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APIHOOK_ENUM_ENTRY(FreeEnvironmentStringsW)
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APIHOOK_ENUM_END
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#define MAX_ENV 1024
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CHAR g_szBlockA[MAX_ENV];
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WCHAR g_szBlockW[MAX_ENV];
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WCHAR *g_szEnv[] = {
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L"TMP=%TMP%",
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L"TEMP=%TEMP%",
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L"PROMPT=%PROMPT%",
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L"winbootdir=%WINDIR%",
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L"PATH=%WINDIR%",
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L"COMSPEC=%COMSPEC%",
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L"WINDIR=%WINDIR%",
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NULL
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};
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/*++
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Build a reasonable looking environment block
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--*/
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BOOL BuildEnvironmentStrings()
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{
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WCHAR *pPtr = g_szBlockW;
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WCHAR szTmp[MAX_PATH];
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DWORD dwSize = 0; DWORD i = 0;
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DPFN( eDbgLevelError, "Building Environment Block");
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// Calculate the remaining block size, subtract one so we can add extra null
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// terminator after all variables are added.
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DWORD dwRemainingBlockSize = ARRAYSIZE(g_szBlockW)-1;
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//
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// Run g_szEnv, expand all the strings and cat them together to form the
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// new block. pPtr points to current location to write to in g_szBlockW.
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//
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while (g_szEnv[i])
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{
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// Expand the environment string, Note: dwSize DOES include the null terminator.
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dwSize = ExpandEnvironmentStringsW(g_szEnv[i], szTmp, MAX_PATH);
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if ((dwSize > 0) && (dwSize <= MAX_PATH))
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{
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// If expansion was successful add the string to our environment block
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// if there is room.
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if (dwSize <= dwRemainingBlockSize &&
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S_OK == StringCchCopy(pPtr, dwRemainingBlockSize, szTmp))
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{
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// update the block size remaining and move the location pointer.
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dwRemainingBlockSize -= dwSize;
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pPtr += dwSize;
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DPFN( eDbgLevelError, "\tAdding: %S", szTmp);
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}
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else
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{
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DPFN( eDbgLevelError, "Enviroment > %08lx, ignoring %S", MAX_ENV, szTmp);
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}
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}
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i++;
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}
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//
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// Add the extra null terminator and calculate size of env block.
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//
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*pPtr = L'\0';
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pPtr++;
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dwSize = pPtr - g_szBlockW;
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//
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// ANSI conversion for the A functions
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//
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WideCharToMultiByte(
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CP_ACP,
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0,
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(LPWSTR) g_szBlockW,
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dwSize,
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(LPSTR) g_szBlockA,
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dwSize,
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0,
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0);
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return TRUE;
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}
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/*++
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Return our block
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--*/
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LPVOID
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APIHOOK(GetEnvironmentStrings)()
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{
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return (LPVOID) g_szBlockA;
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}
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/*++
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Return our block
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--*/
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LPVOID
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APIHOOK(GetEnvironmentStringsA)()
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{
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return (LPVOID) g_szBlockA;
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}
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/*++
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Return our block
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--*/
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LPVOID
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APIHOOK(GetEnvironmentStringsW)()
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{
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return (LPVOID) g_szBlockW;
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}
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/*++
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Check for our block.
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--*/
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BOOL
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APIHOOK(FreeEnvironmentStringsA)(
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LPSTR lpszEnvironmentBlock
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)
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{
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if ((lpszEnvironmentBlock == (LPSTR)&g_szBlockA[0]) ||
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(lpszEnvironmentBlock == (LPSTR)&g_szBlockW[0]))
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{
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return TRUE;
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}
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else
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{
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return ORIGINAL_API(FreeEnvironmentStringsA)(lpszEnvironmentBlock);
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}
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}
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/*++
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Check for our block.
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--*/
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BOOL
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APIHOOK(FreeEnvironmentStringsW)(
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LPWSTR lpszEnvironmentBlock
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)
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{
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if ((lpszEnvironmentBlock == (LPWSTR)&g_szBlockA[0]) ||
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(lpszEnvironmentBlock == (LPWSTR)&g_szBlockW[0]))
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{
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return TRUE;
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}
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else
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{
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return ORIGINAL_API(FreeEnvironmentStringsW)(lpszEnvironmentBlock);
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}
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}
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/*++
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Register hooked functions
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--*/
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BOOL
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NOTIFY_FUNCTION(
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DWORD fdwReason
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)
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{
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if (fdwReason == DLL_PROCESS_ATTACH)
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{
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return BuildEnvironmentStrings();
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}
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return TRUE;
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}
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HOOK_BEGIN
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CALL_NOTIFY_FUNCTION
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APIHOOK_ENTRY(KERNEL32.DLL, GetEnvironmentStrings)
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APIHOOK_ENTRY(KERNEL32.DLL, GetEnvironmentStringsA)
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APIHOOK_ENTRY(KERNEL32.DLL, GetEnvironmentStringsW)
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APIHOOK_ENTRY(KERNEL32.DLL, FreeEnvironmentStringsA)
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APIHOOK_ENTRY(KERNEL32.DLL, FreeEnvironmentStringsW)
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HOOK_END
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IMPLEMENT_SHIM_END
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