Thunk table in import address table? - dll

Question

What is a thunk table in relation to the import address table that's used in EXE files to import functions used in external DLLs?
Is this thunk table just a table containing 'Thunks' to other functions?

Answer 1

Thunks are a part of the Import table (IMAGE_DIRECTORY_ENTRY_IMPORT) and Delay Import Table (IMAGE_DIRECTORY_ENTRY_DELAY_IMPORT). They are described http://msdn.microsoft.com/en-us/library/ms809762.aspx.
I'll look at my old source code and will post later a working code which dump both this tables inclusive binding information.
UPDATED:
Here is a code which I fond in one of my old program. It support only 32-bit PE, but can be easy modified to 64-bit. By the way you can see, that it dump also binding information.To test this bind the PE which you want to dump with respect of bind.exe (use for example, bind.exe -u -v Test.dll).
The code consist from about 1000 lines, so I could not post it here. I receive an error message
Oops! Your edit couldn't be submitted because:
body is limited to 30000 characters; you entered 55095
So I placed it here: http://www.ok-soft-gmbh.com/ForStackOverflow/PEInfo.c. I hope the code will help you better as a long description.
UPDATED 2: I see that my old answer is not good for searching engine. So I includes the part of the code of PEInfo.c (the functions DumpImports and DumpExports) below:
void MakeIdent (UINT nOffset)
{
for (; nOffset; nOffset--)
printf (" "); // 4 blanks
}
void DumpDword (UINT nOffset, LPCSTR pszPrefix, DWORD dw)
{
MakeIdent(nOffset);
if (dw < 100)
printf ("%s: %d\n", pszPrefix, dw);
else if (dw%(256*256) == 0)
printf ("%s: 0x%X\n", pszPrefix, dw);
else
printf ("%s: %d (0x%X)\n", pszPrefix, dw, dw);
}
void DumpTimeDateStamp (UINT nOffset, LPCSTR pszTimeDateStampPrefix, DWORD dwTimeDateStamp)
{
//struct tm tmTime;//= localtime_s ((time_t *)&dwTimeDateStamp);
//errno_t err = localtime_s (&tmTime, ((time_t *)&dwTimeDateStamp));
struct tm *ptmTime = _localtime32 ((__time32_t *)&dwTimeDateStamp);
SYSTEMTIME stSystemTime;
static CHAR szString[128];
stSystemTime.wYear = (WORD)(1900 + ptmTime->tm_year);
stSystemTime.wMonth = (WORD)(ptmTime->tm_mon + 1);
stSystemTime.wDay = (WORD)ptmTime->tm_mday;
stSystemTime.wDayOfWeek = (WORD)(ptmTime->tm_wday + 1);
stSystemTime.wHour = (WORD)ptmTime->tm_hour;
stSystemTime.wMinute = (WORD)ptmTime->tm_min;
stSystemTime.wSecond = (WORD)ptmTime->tm_sec;
stSystemTime.wMilliseconds = 0;
MakeIdent(nOffset);
printf ("%s: 0x%8X (", pszTimeDateStampPrefix, dwTimeDateStamp);
if (GetDateFormatA (LOCALE_USER_DEFAULT, 0, &stSystemTime, NULL,
szString, sizeof(szString)/sizeof(TCHAR)) != 0) {
printf (szString);
}
if (GetTimeFormatA (LOCALE_USER_DEFAULT, 0, &stSystemTime, NULL,
szString, sizeof(szString)/sizeof(TCHAR)) != 0) {
if (szString[0] != 0)
printf (" ");
printf (szString);
}
printf (")\n");
}
void DumpImports (UINT nOffset, IMAGE_OPTIONAL_HEADER32 *pOptionalHeader, PBYTE pbyFile,
IMAGE_SECTION_HEADER *pSectionHeader, IMAGE_NT_HEADERS32 *pNtHeader) // header of the section, which contains export section
{
IMAGE_IMPORT_DESCRIPTOR *pImportDescriptor = (IMAGE_IMPORT_DESCRIPTOR *)((PBYTE)pbyFile + pSectionHeader->PointerToRawData +
pOptionalHeader->DataDirectory[IMAGE_DIRECTORY_ENTRY_IMPORT].VirtualAddress - pSectionHeader->VirtualAddress);
DWORD dwBoundImportVA = pOptionalHeader->DataDirectory[IMAGE_DIRECTORY_ENTRY_BOUND_IMPORT].VirtualAddress;
IMAGE_BOUND_IMPORT_DESCRIPTOR *pFirstBoundImportDescriptor = NULL, *pBoundImportDescriptor;
//DumpDword (nOffset, TEXT("Characteristics"), pImportDescriptor->Characteristics);
if (dwBoundImportVA) {
UINT i;
IMAGE_SECTION_HEADER *pFirstSectionHeader = (IMAGE_SECTION_HEADER *)((PBYTE)pOptionalHeader + //sizeof(IMAGE_OPTIONAL_HEADER32));
pNtHeader->FileHeader.SizeOfOptionalHeader);
for (i=0; i<pNtHeader->FileHeader.NumberOfSections; i++) {
if (pFirstSectionHeader[i].VirtualAddress <= dwBoundImportVA &&
dwBoundImportVA < pFirstSectionHeader[i].VirtualAddress + pFirstSectionHeader[i].Misc.VirtualSize) {
pFirstBoundImportDescriptor = (IMAGE_BOUND_IMPORT_DESCRIPTOR *)((PBYTE)pbyFile + pFirstSectionHeader[i].PointerToRawData +
dwBoundImportVA - pFirstSectionHeader[i].VirtualAddress);
break;
}
}
if (i >= pNtHeader->FileHeader.NumberOfSections)
pFirstBoundImportDescriptor = (IMAGE_BOUND_IMPORT_DESCRIPTOR *)((PBYTE)pbyFile + dwBoundImportVA);
}
for (;pImportDescriptor->Characteristics; pImportDescriptor++) {
IMAGE_THUNK_DATA *pOriginalFirstThunk = (IMAGE_THUNK_DATA *)((PBYTE)pbyFile + pSectionHeader->PointerToRawData +
pImportDescriptor->OriginalFirstThunk - pSectionHeader->VirtualAddress);
IMAGE_THUNK_DATA *pFirstThunk = (IMAGE_THUNK_DATA *)((PBYTE)pbyFile + pSectionHeader->PointerToRawData +
pImportDescriptor->FirstThunk - pSectionHeader->VirtualAddress);
IMAGE_THUNK_DATA *pOriginalThunk, *pThunk;
MakeIdent(nOffset);
printf ("%s ", pbyFile + pSectionHeader->PointerToRawData + pImportDescriptor->Name - pSectionHeader->VirtualAddress);
//DumpDword (nOffset, TEXT("Ordinal Base"), pExportDirectory->Base);
if (pImportDescriptor->TimeDateStamp == 0) {
//MakeIdent(nOffset);
printf ("(DLL is Not bound)\n");
}
else if (pImportDescriptor->TimeDateStamp == -1) {
//if bound, and real date\time stamp
// // in IMAGE_DIRECTORY_ENTRY_BOUND_IMPORT (new BIND)
//MakeIdent(nOffset);
printf ("(DLL bound with New BIND)\n");
}
else {
//MakeIdent(nOffset);
printf ("(DLL bound with Old BIND) ");
DumpTimeDateStamp (nOffset, "TimeDateStamp", pImportDescriptor->TimeDateStamp);
}
MakeIdent(nOffset+1);
if (pImportDescriptor->TimeDateStamp) // if bound
printf (TEXT(" Ordinal hint BoundAddrs Name\n"));
else
printf (TEXT(" Ordinal hint Name\n"));
for (pOriginalThunk=pOriginalFirstThunk, pThunk=pFirstThunk; pOriginalThunk->u1.AddressOfData; pOriginalThunk++, pThunk++) {
if (IMAGE_SNAP_BY_ORDINAL32(pOriginalThunk->u1.Ordinal)) {
MakeIdent(nOffset+1);
// Ordinal
if (pImportDescriptor->TimeDateStamp)
printf (TEXT("%4u (0x%04X) 0x%08X\n"),
pOriginalThunk->u1.Ordinal & ~IMAGE_ORDINAL_FLAG32,
pOriginalThunk->u1.Ordinal^IMAGE_ORDINAL_FLAG32,
pThunk->u1.AddressOfData);
else
// pThunk->u1.AddressOfData == pOriginalThunk->u1.Ordinal so don't print it
printf (TEXT("%4u (0x%04X)\n"),
pOriginalThunk->u1.Ordinal & ~IMAGE_ORDINAL_FLAG32,
pOriginalThunk->u1.Ordinal^IMAGE_ORDINAL_FLAG32);
}
else {
IMAGE_IMPORT_BY_NAME *pImportByName = (IMAGE_IMPORT_BY_NAME *) (pOriginalThunk->u1.AddressOfData +
(PBYTE)pbyFile + pSectionHeader->PointerToRawData - pSectionHeader->VirtualAddress);
MakeIdent(nOffset+1);
// Hint - Index into the Export Name Pointer Table. A match is attempted first with this value.
// If it fails, a binary search is performed on the DLL’s Export Name Pointer Table.
if (pImportDescriptor->TimeDateStamp) // if bound
printf (TEXT("%18u (0x%04X) 0x%08X %hs\n"), pImportByName->Hint, pImportByName->Hint, pThunk->u1.AddressOfData,
pImportByName->Name);
else
printf (TEXT("%18u (0x%04X) %hs\n"), pImportByName->Hint, pImportByName->Hint, pImportByName->Name);
}
}
}
if (pFirstBoundImportDescriptor) {
MakeIdent(nOffset);
printf ("PE Header contains the following bound import information:\n");
for (pBoundImportDescriptor=pFirstBoundImportDescriptor; pBoundImportDescriptor->TimeDateStamp;
pBoundImportDescriptor = (IMAGE_BOUND_IMPORT_DESCRIPTOR *)((PBYTE)(pBoundImportDescriptor+1) + pBoundImportDescriptor->NumberOfModuleForwarderRefs*sizeof(IMAGE_BOUND_FORWARDER_REF))) {
PSTR pszDllName = (PSTR) ((DWORD)pFirstBoundImportDescriptor + pBoundImportDescriptor->OffsetModuleName);
IMAGE_BOUND_FORWARDER_REF *pRef = (IMAGE_BOUND_FORWARDER_REF *)(pBoundImportDescriptor+1);
MakeIdent(nOffset+1);
printf ("Bound to %hs", pszDllName);
DumpTimeDateStamp (0, "", pBoundImportDescriptor->TimeDateStamp);
if (pBoundImportDescriptor->NumberOfModuleForwarderRefs) {
UINT i;
for (i=0;i<pBoundImportDescriptor->NumberOfModuleForwarderRefs;i++) {
PSTR pszDllName = (PSTR) ((DWORD)pFirstBoundImportDescriptor + pRef->OffsetModuleName);
MakeIdent(nOffset+2);
printf ("Contained forwarders bound to %hs", pszDllName);
DumpTimeDateStamp (0, "", pRef->TimeDateStamp);
}
}
}
}
}
void DumpExports (UINT nOffset, IMAGE_OPTIONAL_HEADER32 *pOptionalHeader, PBYTE pbyFile,
IMAGE_SECTION_HEADER *pSectionHeader) // header of the section, which contains export section
{
UINT i;
UINT iNames;
PDWORD pdwAddressOfFunctions;
PWORD pwOrdinals;
PDWORD pdwNameRVA;
IMAGE_EXPORT_DIRECTORY *pExportDirectory = (IMAGE_EXPORT_DIRECTORY *)((PBYTE)pbyFile + pSectionHeader->PointerToRawData +
pOptionalHeader->DataDirectory[IMAGE_DIRECTORY_ENTRY_EXPORT].VirtualAddress - pSectionHeader->VirtualAddress);
DWORD dwVAExportStart = pOptionalHeader->DataDirectory[IMAGE_DIRECTORY_ENTRY_EXPORT].VirtualAddress;
DWORD dwVAExportEnd = pOptionalHeader->DataDirectory[IMAGE_DIRECTORY_ENTRY_EXPORT].VirtualAddress +
pOptionalHeader->DataDirectory[IMAGE_DIRECTORY_ENTRY_EXPORT].Size;
DumpDword (nOffset, TEXT("Characteristics"), pExportDirectory->Characteristics);
DumpTimeDateStamp (nOffset, "TimeDateStamp", pExportDirectory->TimeDateStamp);
MakeIdent(nOffset);
printf ("DllName: %s\n", pbyFile + pSectionHeader->PointerToRawData + pExportDirectory->Name - pSectionHeader->VirtualAddress);
DumpDword (nOffset, TEXT("Ordinal Base"), pExportDirectory->Base);
MakeIdent(nOffset);
printf (TEXT("Version: %d.%d\n"), pExportDirectory->MajorVersion, pExportDirectory->MinorVersion);
DumpDword (nOffset, TEXT("Number of exported functions"), pExportDirectory->NumberOfFunctions);
DumpDword (nOffset, TEXT("Number of functions exported by name"), pExportDirectory->NumberOfNames);
MakeIdent(nOffset+1);
printf (TEXT("Ordn hint RVA Name\n"));
pdwAddressOfFunctions = (PDWORD)(pbyFile + pSectionHeader->PointerToRawData + pExportDirectory->AddressOfFunctions - pSectionHeader->VirtualAddress);
pwOrdinals = (PWORD)(pbyFile + pSectionHeader->PointerToRawData + pExportDirectory->AddressOfNameOrdinals - pSectionHeader->VirtualAddress);
pdwNameRVA = (PDWORD)(pbyFile + pSectionHeader->PointerToRawData + pExportDirectory->AddressOfNames - pSectionHeader->VirtualAddress);
for (iNames = 0; iNames < pExportDirectory->NumberOfNames; iNames++) {
MakeIdent(nOffset+1);
// AddressOfFunctions MUST be ouf of Export Directory. If it is not so, it is a Forwarding entry
if (pdwAddressOfFunctions[pwOrdinals[iNames]] < dwVAExportStart ||
pdwAddressOfFunctions[pwOrdinals[iNames]] > dwVAExportEnd)
// AddressOfFunctions is normaly in .text section and export table in .edata or .rdata section, so
// AddressOfFunctions must be not in Export Directory
printf("%4u %4u %08X %s\n",
pwOrdinals[iNames] + pExportDirectory->Base, iNames, pdwAddressOfFunctions[pwOrdinals[iNames]],
(pbyFile + pSectionHeader->PointerToRawData + pdwNameRVA[iNames] - pSectionHeader->VirtualAddress));
else
printf("%4u %4u %s (forwarded to %s)\n",
pwOrdinals[iNames] + pExportDirectory->Base, iNames,
(pbyFile + pSectionHeader->PointerToRawData + pdwNameRVA[iNames] - pSectionHeader->VirtualAddress),
(PSTR)(pbyFile + pSectionHeader->PointerToRawData + pdwAddressOfFunctions[pwOrdinals[iNames]] - pSectionHeader->VirtualAddress));
}
// print functions exported by ordinal
for (i = 0; i < pExportDirectory->NumberOfFunctions; i++) {
if (pdwAddressOfFunctions[i] != 0) {
// if EXPORTS in DEF-file look like
//
// EXPORTS
// Message1 #100
// Message2 #200
// Message3 #300
// Message4 #400
// Message5 #500
// it will be added in export section 401 (500-100+1) entries. 5 from there with not 0 address and the rest
// empty entries with 0
// we will dump only not empty entries
UINT iNames;
WORD wOrdinal = (WORD)(i + pExportDirectory->Base);
// try to find (i + pExportDirectory->Base) ordinal in the list of pwOrdinals
for (iNames = 0; iNames<pExportDirectory->NumberOfNames; iNames++) {
if (pdwAddressOfFunctions[pwOrdinals[iNames]] == pdwAddressOfFunctions[i])
break;
}
if (iNames >= pExportDirectory->NumberOfNames) {
// if not found as exported by name, print it here
MakeIdent(nOffset+1);
if (pdwAddressOfFunctions[i] < pSectionHeader->VirtualAddress ||
pdwAddressOfFunctions[i] > pSectionHeader->VirtualAddress + pSectionHeader->Misc.VirtualSize)
printf("%4u %08X [NONAME]\n", wOrdinal, pdwAddressOfFunctions[i]);
else
printf("%4u [NONAME] (forwarded to %s)\n",
wOrdinal, (PSTR)(pbyFile + pSectionHeader->PointerToRawData + pdwAddressOfFunctions[i] - pSectionHeader->VirtualAddress));
}
}
}
}