/* SPDX-License-Identifier: MIT
*
* Copyright (C) 2017-2026 WireGuard LLC. All Rights Reserved.
*/
package memmod
import (
"errors"
"fmt"
"strings"
"sync"
"syscall"
"unsafe"
"golang.org/x/sys/windows"
)
type addressList struct {
next *addressList
address uintptr
}
func (head *addressList) free() {
for node := head; node != nil; node = node.next {
windows.VirtualFree(node.address, 0, windows.MEM_RELEASE)
}
}
type Module struct {
headers *IMAGE_NT_HEADERS
codeBase uintptr
modules []windows.Handle
initialized bool
isDLL bool
isRelocated bool
nameExports map[string]uint16
entry uintptr
blockedMemory *addressList
runtimeFuncs *windows.RUNTIME_FUNCTION
}
func (module *Module) BaseAddr() uintptr {
return module.codeBase
}
func (module *Module) headerDirectory(idx int) *IMAGE_DATA_DIRECTORY {
return &module.headers.OptionalHeader.DataDirectory[idx]
}
func (module *Module) copySections(address, size uintptr, oldHeaders *IMAGE_NT_HEADERS) error {
sections := module.headers.Sections()
for i := range sections {
if sections[i].SizeOfRawData == 0 {
// Section doesn't contain data in the dll itself, but may define uninitialized data.
sectionSize := oldHeaders.OptionalHeader.SectionAlignment
if sectionSize == 0 {
continue
}
dest, err := windows.VirtualAlloc(module.codeBase+uintptr(sections[i].VirtualAddress),
uintptr(sectionSize),
windows.MEM_COMMIT,
windows.PAGE_READWRITE)
if err != nil {
return fmt.Errorf("Error allocating section: %w", err)
}
// Always use position from file to support alignments smaller than page size (allocation above will align to page size).
dest = module.codeBase + uintptr(sections[i].VirtualAddress)
// NOTE: On 64bit systems we truncate to 32bit here but expand again later when "PhysicalAddress" is used.
sections[i].SetPhysicalAddress((uint32)(dest & 0xffffffff))
dst := unsafe.Slice((*byte)(a2p(dest)), sectionSize)
for j := range dst {
dst[j] = 0
}
continue
}
if size < uintptr(sections[i].PointerToRawData)+uintptr(sections[i].SizeOfRawData) {
return errors.New("Incomplete section")
}
// Commit memory block and copy data from dll.
dest, err := windows.VirtualAlloc(module.codeBase+uintptr(sections[i].VirtualAddress),
uintptr(sections[i].SizeOfRawData),
windows.MEM_COMMIT,
windows.PAGE_READWRITE)
if err != nil {
return fmt.Errorf("Error allocating memory block: %w", err)
}
// Always use position from file to support alignments smaller than page size (allocation above will align to page size).
memcpy(
module.codeBase+uintptr(sections[i].VirtualAddress),
address+uintptr(sections[i].PointerToRawData),
uintptr(sections[i].SizeOfRawData))
// NOTE: On 64bit systems we truncate to 32bit here but expand again later when "PhysicalAddress" is used.
sections[i].SetPhysicalAddress((uint32)(dest & 0xffffffff))
}
return nil
}
func (module *Module) realSectionSize(section *IMAGE_SECTION_HEADER) uintptr {
size := section.SizeOfRawData
if size != 0 {
return uintptr(size)
}
if (section.Characteristics & IMAGE_SCN_CNT_INITIALIZED_DATA) != 0 {
return uintptr(module.headers.OptionalHeader.SizeOfInitializedData)
}
if (section.Characteristics & IMAGE_SCN_CNT_UNINITIALIZED_DATA) != 0 {
return uintptr(module.headers.OptionalHeader.SizeOfUninitializedData)
}
return 0
}
type sectionFinalizeData struct {
address uintptr
alignedAddress uintptr
size uintptr
characteristics uint32
last bool
}
func (module *Module) finalizeSection(sectionData *sectionFinalizeData) error {
if sectionData.size == 0 {
return nil
}
if (sectionData.characteristics & IMAGE_SCN_MEM_DISCARDABLE) != 0 {
// Section is not needed any more and can safely be freed.
if sectionData.address == sectionData.alignedAddress &&
(sectionData.last ||
(sectionData.size%uintptr(module.headers.OptionalHeader.SectionAlignment)) == 0) {
// Only allowed to decommit whole pages.
windows.VirtualFree(sectionData.address, sectionData.size, windows.MEM_DECOMMIT)
}
return nil
}
// determine protection flags based on characteristics
ProtectionFlags := [8]uint32{
windows.PAGE_NOACCESS, // not writeable, not readable, not executable
windows.PAGE_EXECUTE, // not writeable, not readable, executable
windows.PAGE_READONLY, // not writeable, readable, not executable
windows.PAGE_EXECUTE_READ, // not writeable, readable, executable
windows.PAGE_WRITECOPY, // writeable, not readable, not executable
windows.PAGE_EXECUTE_WRITECOPY, // writeable, not readable, executable
windows.PAGE_READWRITE, // writeable, readable, not executable
windows.PAGE_EXECUTE_READWRITE, // writeable, readable, executable
}
protect := ProtectionFlags[sectionData.characteristics>>29]
if (sectionData.characteristics & IMAGE_SCN_MEM_NOT_CACHED) != 0 {
protect |= windows.PAGE_NOCACHE
}
// Change memory access flags.
var oldProtect uint32
err := windows.VirtualProtect(sectionData.address, sectionData.size, protect, &oldProtect)
if err != nil {
return fmt.Errorf("Error protecting memory page: %w", err)
}
return nil
}
func (module *Module) registerExceptionHandlers() {
directory := module.headerDirectory(IMAGE_DIRECTORY_ENTRY_EXCEPTION)
if directory.Size == 0 || directory.VirtualAddress == 0 {
return
}
runtimeFuncs := (*windows.RUNTIME_FUNCTION)(unsafe.Pointer(module.codeBase + uintptr(directory.VirtualAddress)))
if !windows.RtlAddFunctionTable(runtimeFuncs, uint32(uintptr(directory.Size)/unsafe.Sizeof(*runtimeFuncs)), module.codeBase) {
return
}
module.runtimeFuncs = runtimeFuncs
}
func (module *Module) finalizeSections() error {
sections := module.headers.Sections()
imageOffset := module.headers.OptionalHeader.imageOffset()
sectionData := sectionFinalizeData{}
sectionData.address = uintptr(sections[0].PhysicalAddress()) | imageOffset
sectionData.alignedAddress = alignDown(sectionData.address, uintptr(module.headers.OptionalHeader.SectionAlignment))
sectionData.size = module.realSectionSize(§ions[0])
sections[0].SetVirtualSize(uint32(sectionData.size))
sectionData.characteristics = sections[0].Characteristics
// Loop through all sections and change access flags.
for i := uint16(1); i < module.headers.FileHeader.NumberOfSections; i++ {
sectionAddress := uintptr(sections[i].PhysicalAddress()) | imageOffset
alignedAddress := alignDown(sectionAddress, uintptr(module.headers.OptionalHeader.SectionAlignment))
sectionSize := module.realSectionSize(§ions[i])
sections[i].SetVirtualSize(uint32(sectionSize))
// Combine access flags of all sections that share a page.
// TODO: We currently share flags of a trailing large section with the page of a first small section. This should be optimized.
if sectionData.alignedAddress == alignedAddress || sectionData.address+sectionData.size > alignedAddress {
// Section shares page with previous.
if (sections[i].Characteristics&IMAGE_SCN_MEM_DISCARDABLE) == 0 || (sectionData.characteristics&IMAGE_SCN_MEM_DISCARDABLE) == 0 {
sectionData.characteristics = (sectionData.characteristics | sections[i].Characteristics) &^ IMAGE_SCN_MEM_DISCARDABLE
} else {
sectionData.characteristics |= sections[i].Characteristics
}
sectionData.size = sectionAddress + sectionSize - sectionData.address
continue
}
err := module.finalizeSection(§ionData)
if err != nil {
return fmt.Errorf("Error finalizing section: %w", err)
}
sectionData.address = sectionAddress
sectionData.alignedAddress = alignedAddress
sectionData.size = sectionSize
sectionData.characteristics = sections[i].Characteristics
}
sectionData.last = true
err := module.finalizeSection(§ionData)
if err != nil {
return fmt.Errorf("Error finalizing section: %w", err)
}
return nil
}
func (module *Module) executeTLS() {
directory := module.headerDirectory(IMAGE_DIRECTORY_ENTRY_TLS)
if directory.VirtualAddress == 0 {
return
}
tls := (*IMAGE_TLS_DIRECTORY)(a2p(module.codeBase + uintptr(directory.VirtualAddress)))
callback := tls.AddressOfCallbacks
if callback != 0 {
for {
f := *(*uintptr)(a2p(callback))
if f == 0 {
break
}
syscall.SyscallN(f, module.codeBase, DLL_PROCESS_ATTACH, 0)
callback += unsafe.Sizeof(f)
}
}
}
func (module *Module) performBaseRelocation(delta uintptr) (relocated bool, err error) {
directory := module.headerDirectory(IMAGE_DIRECTORY_ENTRY_BASERELOC)
if directory.Size == 0 {
return delta == 0, nil
}
relocBase := module.codeBase + uintptr(directory.VirtualAddress)
relocEnd := relocBase + uintptr(directory.Size)
relocationHdr := (*IMAGE_BASE_RELOCATION)(a2p(relocBase))
for uintptr(unsafe.Pointer(relocationHdr))+unsafe.Sizeof(*relocationHdr) <= relocEnd && relocationHdr.VirtualAddress > 0 {
if uintptr(relocationHdr.SizeOfBlock) < unsafe.Sizeof(*relocationHdr) {
return false, errors.New("Invalid relocation block size")
}
if uintptr(unsafe.Pointer(relocationHdr))+uintptr(relocationHdr.SizeOfBlock) > relocEnd {
return false, errors.New("Relocation block exceeds directory bounds")
}
dest := module.codeBase + uintptr(relocationHdr.VirtualAddress)
relInfos := unsafe.Slice(
(*uint16)(a2p(uintptr(unsafe.Pointer(relocationHdr))+unsafe.Sizeof(*relocationHdr))),
(uintptr(relocationHdr.SizeOfBlock)-unsafe.Sizeof(*relocationHdr))/unsafe.Sizeof(uint16(0)))
for _, relInfo := range relInfos {
// The upper 4 bits define the type of relocation.
relType := relInfo >> 12
// The lower 12 bits define the offset.
relOffset := uintptr(relInfo & 0xfff)
switch relType {
case IMAGE_REL_BASED_ABSOLUTE:
// Skip relocation.
case IMAGE_REL_BASED_LOW:
*(*uint16)(a2p(dest + relOffset)) += uint16(delta & 0xffff)
break
case IMAGE_REL_BASED_HIGH:
*(*uint16)(a2p(dest + relOffset)) += uint16(uint32(delta) >> 16)
break
case IMAGE_REL_BASED_HIGHLOW:
*(*uint32)(a2p(dest + relOffset)) += uint32(delta)
case IMAGE_REL_BASED_DIR64:
*(*uint64)(a2p(dest + relOffset)) += uint64(delta)
case IMAGE_REL_BASED_THUMB_MOV32:
inst := *(*uint32)(a2p(dest + relOffset))
imm16 := ((inst << 1) & 0x0800) + ((inst << 12) & 0xf000) +
((inst >> 20) & 0x0700) + ((inst >> 16) & 0x00ff)
if (inst & 0x8000fbf0) != 0x0000f240 {
return false, fmt.Errorf("Wrong Thumb2 instruction %08x, expected MOVW", inst)
}
imm16 += uint32(delta) & 0xffff
hiDelta := (uint32(delta&0xffff0000) >> 16) + ((imm16 & 0xffff0000) >> 16)
*(*uint32)(a2p(dest + relOffset)) = (inst & 0x8f00fbf0) + ((imm16 >> 1) & 0x0400) +
((imm16 >> 12) & 0x000f) +
((imm16 << 20) & 0x70000000) +
((imm16 << 16) & 0xff0000)
if hiDelta != 0 {
inst = *(*uint32)(a2p(dest + relOffset + 4))
imm16 = ((inst << 1) & 0x0800) + ((inst << 12) & 0xf000) +
((inst >> 20) & 0x0700) + ((inst >> 16) & 0x00ff)
if (inst & 0x8000fbf0) != 0x0000f2c0 {
return false, fmt.Errorf("Wrong Thumb2 instruction %08x, expected MOVT", inst)
}
imm16 += hiDelta
if imm16 > 0xffff {
return false, fmt.Errorf("Resulting immediate value won't fit: %08x", imm16)
}
*(*uint32)(a2p(dest + relOffset + 4)) = (inst & 0x8f00fbf0) +
((imm16 >> 1) & 0x0400) +
((imm16 >> 12) & 0x000f) +
((imm16 << 20) & 0x70000000) +
((imm16 << 16) & 0xff0000)
}
default:
return false, fmt.Errorf("Unsupported relocation: %v", relType)
}
}
// Advance to next relocation block.
relocationHdr = (*IMAGE_BASE_RELOCATION)(a2p(uintptr(unsafe.Pointer(relocationHdr)) + uintptr(relocationHdr.SizeOfBlock)))
}
return true, nil
}
func (module *Module) buildImportTable() error {
directory := module.headerDirectory(IMAGE_DIRECTORY_ENTRY_IMPORT)
if directory.Size == 0 {
return nil
}
module.modules = make([]windows.Handle, 0, 16)
importDesc := (*IMAGE_IMPORT_DESCRIPTOR)(a2p(module.codeBase + uintptr(directory.VirtualAddress)))
for importDesc.Name != 0 {
handle, err := windows.LoadLibraryEx(windows.BytePtrToString((*byte)(a2p(module.codeBase+uintptr(importDesc.Name)))), 0, windows.LOAD_LIBRARY_SEARCH_SYSTEM32)
if err != nil {
return fmt.Errorf("Error loading module: %w", err)
}
var thunkRef, funcRef *uintptr
if importDesc.OriginalFirstThunk() != 0 {
thunkRef = (*uintptr)(a2p(module.codeBase + uintptr(importDesc.OriginalFirstThunk())))
funcRef = (*uintptr)(a2p(module.codeBase + uintptr(importDesc.FirstThunk)))
} else {
// No hint table.
thunkRef = (*uintptr)(a2p(module.codeBase + uintptr(importDesc.FirstThunk)))
funcRef = (*uintptr)(a2p(module.codeBase + uintptr(importDesc.FirstThunk)))
}
for *thunkRef != 0 {
if IMAGE_SNAP_BY_ORDINAL(*thunkRef) {
*funcRef, err = windows.GetProcAddressByOrdinal(handle, IMAGE_ORDINAL(*thunkRef))
} else {
thunkData := (*IMAGE_IMPORT_BY_NAME)(a2p(module.codeBase + *thunkRef))
*funcRef, err = windows.GetProcAddress(handle, windows.BytePtrToString(&thunkData.Name[0]))
}
if err != nil {
windows.FreeLibrary(handle)
return fmt.Errorf("Error getting function address: %w", err)
}
thunkRef = (*uintptr)(a2p(uintptr(unsafe.Pointer(thunkRef)) + unsafe.Sizeof(*thunkRef)))
funcRef = (*uintptr)(a2p(uintptr(unsafe.Pointer(funcRef)) + unsafe.Sizeof(*funcRef)))
}
module.modules = append(module.modules, handle)
importDesc = (*IMAGE_IMPORT_DESCRIPTOR)(a2p(uintptr(unsafe.Pointer(importDesc)) + unsafe.Sizeof(*importDesc)))
}
return nil
}
func (module *Module) buildNameExports() error {
directory := module.headerDirectory(IMAGE_DIRECTORY_ENTRY_EXPORT)
if directory.Size == 0 {
return errors.New("No export table found")
}
exports := (*IMAGE_EXPORT_DIRECTORY)(a2p(module.codeBase + uintptr(directory.VirtualAddress)))
if exports.NumberOfFunctions == 0 {
return errors.New("No functions exported")
}
if exports.NumberOfNames == 0 {
return errors.New("No functions exported by name")
}
nameRefs := unsafe.Slice((*uint32)(a2p(module.codeBase+uintptr(exports.AddressOfNames))), exports.NumberOfNames)
ordinals := unsafe.Slice((*uint16)(a2p(module.codeBase+uintptr(exports.AddressOfNameOrdinals))), exports.NumberOfNames)
module.nameExports = make(map[string]uint16)
for i := range nameRefs {
nameArray := windows.BytePtrToString((*byte)(a2p(module.codeBase + uintptr(nameRefs[i]))))
module.nameExports[nameArray] = ordinals[i]
}
return nil
}
type addressRange struct {
start uintptr
end uintptr
}
var (
loadedAddressRanges []addressRange
loadedAddressRangesMu sync.RWMutex
haveHookedRtlPcToFileHeader sync.Once
hookRtlPcToFileHeaderResult error
)
func hookRtlPcToFileHeader() error {
var kernelBase windows.Handle
err := windows.GetModuleHandleEx(windows.GET_MODULE_HANDLE_EX_FLAG_UNCHANGED_REFCOUNT, windows.StringToUTF16Ptr("kernelbase.dll"), &kernelBase)
if err != nil {
return err
}
imageBase := unsafe.Pointer(kernelBase)
dosHeader := (*IMAGE_DOS_HEADER)(imageBase)
ntHeaders := (*IMAGE_NT_HEADERS)(unsafe.Add(imageBase, dosHeader.E_lfanew))
importsDirectory := ntHeaders.OptionalHeader.DataDirectory[IMAGE_DIRECTORY_ENTRY_IMPORT]
importDescriptor := (*IMAGE_IMPORT_DESCRIPTOR)(unsafe.Add(imageBase, importsDirectory.VirtualAddress))
for ; importDescriptor.Name != 0; importDescriptor = (*IMAGE_IMPORT_DESCRIPTOR)(unsafe.Add(unsafe.Pointer(importDescriptor), unsafe.Sizeof(*importDescriptor))) {
libraryName := windows.BytePtrToString((*byte)(unsafe.Add(imageBase, importDescriptor.Name)))
if strings.EqualFold(libraryName, "ntdll.dll") {
break
}
}
if importDescriptor.Name == 0 {
return errors.New("ntdll.dll not found")
}
originalThunk := (*uintptr)(unsafe.Add(imageBase, importDescriptor.OriginalFirstThunk()))
thunk := (*uintptr)(unsafe.Add(imageBase, importDescriptor.FirstThunk))
for ; *originalThunk != 0; originalThunk = (*uintptr)(unsafe.Add(unsafe.Pointer(originalThunk), unsafe.Sizeof(*originalThunk))) {
if *originalThunk&IMAGE_ORDINAL_FLAG == 0 {
function := (*IMAGE_IMPORT_BY_NAME)(unsafe.Add(imageBase, *originalThunk))
name := windows.BytePtrToString(&function.Name[0])
if name == "RtlPcToFileHeader" {
break
}
}
thunk = (*uintptr)(unsafe.Add(unsafe.Pointer(thunk), unsafe.Sizeof(*thunk)))
}
if *originalThunk == 0 {
return errors.New("RtlPcToFileHeader not found")
}
var oldProtect uint32
err = windows.VirtualProtect(uintptr(unsafe.Pointer(thunk)), unsafe.Sizeof(*thunk), windows.PAGE_READWRITE, &oldProtect)
if err != nil {
return err
}
originalRtlPcToFileHeader := *thunk
*thunk = windows.NewCallback(func(pcValue uintptr, baseOfImage *uintptr) uintptr {
loadedAddressRangesMu.RLock()
for i := range loadedAddressRanges {
if pcValue >= loadedAddressRanges[i].start && pcValue < loadedAddressRanges[i].end {
pcValue = *thunk
break
}
}
loadedAddressRangesMu.RUnlock()
ret, _, _ := syscall.SyscallN(originalRtlPcToFileHeader, pcValue, uintptr(unsafe.Pointer(baseOfImage)))
return ret
})
err = windows.VirtualProtect(uintptr(unsafe.Pointer(thunk)), unsafe.Sizeof(*thunk), oldProtect, &oldProtect)
if err != nil {
return err
}
return nil
}
// LoadLibrary loads module image to memory.
func LoadLibrary(data []byte) (module *Module, err error) {
size := uintptr(len(data))
if size < unsafe.Sizeof(IMAGE_DOS_HEADER{}) {
return nil, errors.New("Incomplete IMAGE_DOS_HEADER")
}
addr := uintptr(unsafe.Pointer(&data[0]))
dosHeader := (*IMAGE_DOS_HEADER)(a2p(addr))
if dosHeader.E_magic != IMAGE_DOS_SIGNATURE {
return nil, fmt.Errorf("Not an MS-DOS binary (provided: %x, expected: %x)", dosHeader.E_magic, IMAGE_DOS_SIGNATURE)
}
if dosHeader.E_lfanew < 0 || (size < uintptr(dosHeader.E_lfanew)+unsafe.Sizeof(IMAGE_NT_HEADERS{})) {
return nil, errors.New("Incomplete IMAGE_NT_HEADERS")
}
oldHeader := (*IMAGE_NT_HEADERS)(a2p(addr + uintptr(dosHeader.E_lfanew)))
if oldHeader.Signature != IMAGE_NT_SIGNATURE {
return nil, fmt.Errorf("Not an NT binary (provided: %x, expected: %x)", oldHeader.Signature, IMAGE_NT_SIGNATURE)
}
if oldHeader.FileHeader.Machine != imageFileProcess {
return nil, fmt.Errorf("Foreign platform (provided: %x, expected: %x)", oldHeader.FileHeader.Machine, imageFileProcess)
}
if oldHeader.OptionalHeader.SectionAlignment == 0 || (oldHeader.OptionalHeader.SectionAlignment&(oldHeader.OptionalHeader.SectionAlignment-1)) != 0 {
return nil, errors.New("Unaligned section")
}
if oldHeader.FileHeader.NumberOfSections == 0 {
return nil, errors.New("No sections")
}
if uintptr(oldHeader.FileHeader.SizeOfOptionalHeader) < unsafe.Sizeof(oldHeader.OptionalHeader) {
return nil, errors.New("Incomplete optional header")
}
if oldHeader.OptionalHeader.NumberOfRvaAndSizes < IMAGE_NUMBEROF_DIRECTORY_ENTRIES {
return nil, errors.New("Incomplete data directory")
}
sectionHeadersEnd := uintptr(dosHeader.E_lfanew) + unsafe.Offsetof(oldHeader.OptionalHeader) + uintptr(oldHeader.FileHeader.SizeOfOptionalHeader) +
uintptr(oldHeader.FileHeader.NumberOfSections)*unsafe.Sizeof(IMAGE_SECTION_HEADER{})
if size < sectionHeadersEnd {
return nil, errors.New("Incomplete section headers")
}
lastSectionEnd := uintptr(0)
sections := oldHeader.Sections()
optionalSectionSize := oldHeader.OptionalHeader.SectionAlignment
for i := range sections {
var endOfSection uintptr
if sections[i].SizeOfRawData == 0 {
// Section without data in the DLL
endOfSection = uintptr(sections[i].VirtualAddress) + uintptr(optionalSectionSize)
} else {
endOfSection = uintptr(sections[i].VirtualAddress) + uintptr(sections[i].SizeOfRawData)
}
if endOfSection > lastSectionEnd {
lastSectionEnd = endOfSection
}
}
alignedImageSize := alignUp(uintptr(oldHeader.OptionalHeader.SizeOfImage), uintptr(oldHeader.OptionalHeader.SectionAlignment))
if alignedImageSize != alignUp(lastSectionEnd, uintptr(oldHeader.OptionalHeader.SectionAlignment)) {
return nil, errors.New("Section is not page-aligned")
}
module = &Module{isDLL: (oldHeader.FileHeader.Characteristics & IMAGE_FILE_DLL) != 0}
defer func() {
if err != nil {
module.Free()
module = nil
}
}()
// Reserve memory for image of library.
// TODO: Is it correct to commit the complete memory region at once? Calling DllEntry raises an exception if we don't.
module.codeBase, err = windows.VirtualAlloc(oldHeader.OptionalHeader.ImageBase,
alignedImageSize,
windows.MEM_RESERVE|windows.MEM_COMMIT,
windows.PAGE_READWRITE)
if err != nil {
// Try to allocate memory at arbitrary position.
module.codeBase, err = windows.VirtualAlloc(0,
alignedImageSize,
windows.MEM_RESERVE|windows.MEM_COMMIT,
windows.PAGE_READWRITE)
if err != nil {
err = fmt.Errorf("Error allocating code: %w", err)
return
}
}
err = module.check4GBBoundaries(alignedImageSize)
if err != nil {
err = fmt.Errorf("Error reallocating code: %w", err)
return
}
if size < uintptr(oldHeader.OptionalHeader.SizeOfHeaders) {
err = errors.New("Incomplete headers")
return
}
// Commit memory for headers.
headers, err := windows.VirtualAlloc(module.codeBase,
uintptr(oldHeader.OptionalHeader.SizeOfHeaders),
windows.MEM_COMMIT,
windows.PAGE_READWRITE)
if err != nil {
err = fmt.Errorf("Error allocating headers: %w", err)
return
}
// Copy PE header to code.
memcpy(headers, addr, uintptr(oldHeader.OptionalHeader.SizeOfHeaders))
module.headers = (*IMAGE_NT_HEADERS)(a2p(headers + uintptr(dosHeader.E_lfanew)))
// Update position.
module.headers.OptionalHeader.ImageBase = module.codeBase
// Copy sections from DLL file block to new memory location.
err = module.copySections(addr, size, oldHeader)
if err != nil {
err = fmt.Errorf("Error copying sections: %w", err)
return
}
// Adjust base address of imported data.
locationDelta := module.headers.OptionalHeader.ImageBase - oldHeader.OptionalHeader.ImageBase
if locationDelta != 0 {
module.isRelocated, err = module.performBaseRelocation(locationDelta)
if err != nil {
err = fmt.Errorf("Error relocating module: %w", err)
return
}
if !module.isRelocated {
err = errors.New("Module could not be relocated")
return
}
} else {
module.isRelocated = true
}
// Load required dlls and adjust function table of imports.
err = module.buildImportTable()
if err != nil {
err = fmt.Errorf("Error building import table: %w", err)
return
}
// Mark memory pages depending on section headers and release sections that are marked as "discardable".
err = module.finalizeSections()
if err != nil {
err = fmt.Errorf("Error finalizing sections: %w", err)
return
}
// Register exception tables, if they exist.
module.registerExceptionHandlers()
// Register function PCs.
loadedAddressRangesMu.Lock()
loadedAddressRanges = append(loadedAddressRanges, addressRange{module.codeBase, module.codeBase + alignedImageSize})
loadedAddressRangesMu.Unlock()
haveHookedRtlPcToFileHeader.Do(func() {
hookRtlPcToFileHeaderResult = hookRtlPcToFileHeader()
})
err = hookRtlPcToFileHeaderResult
if err != nil {
return
}
// TLS callbacks are executed BEFORE the main loading.
module.executeTLS()
// Get entry point of loaded module.
if module.headers.OptionalHeader.AddressOfEntryPoint != 0 {
module.entry = module.codeBase + uintptr(module.headers.OptionalHeader.AddressOfEntryPoint)
if module.isDLL {
// Notify library about attaching to process.
r0, _, _ := syscall.SyscallN(module.entry, module.codeBase, DLL_PROCESS_ATTACH, 0)
successful := r0 != 0
if !successful {
err = windows.ERROR_DLL_INIT_FAILED
return
}
module.initialized = true
}
}
module.buildNameExports()
return
}
// Free releases module resources and unloads it.
func (module *Module) Free() {
if module.initialized {
// Notify library about detaching from process.
syscall.SyscallN(module.entry, module.codeBase, DLL_PROCESS_DETACH, 0)
module.initialized = false
}
if module.modules != nil {
// Free previously opened libraries.
for _, handle := range module.modules {
windows.FreeLibrary(handle)
}
module.modules = nil
}
if module.runtimeFuncs != nil {
windows.RtlDeleteFunctionTable(module.runtimeFuncs)
module.runtimeFuncs = nil
}
if module.codeBase != 0 {
loadedAddressRangesMu.Lock()
for i := range loadedAddressRanges {
if loadedAddressRanges[i].start == module.codeBase {
loadedAddressRanges = append(loadedAddressRanges[:i], loadedAddressRanges[i+1:]...)
break
}
}
loadedAddressRangesMu.Unlock()
windows.VirtualFree(module.codeBase, 0, windows.MEM_RELEASE)
module.codeBase = 0
}
if module.blockedMemory != nil {
module.blockedMemory.free()
module.blockedMemory = nil
}
}
// ProcAddressByName returns function address by exported name.
func (module *Module) ProcAddressByName(name string) (uintptr, error) {
directory := module.headerDirectory(IMAGE_DIRECTORY_ENTRY_EXPORT)
if directory.Size == 0 {
return 0, errors.New("No export table found")
}
exports := (*IMAGE_EXPORT_DIRECTORY)(a2p(module.codeBase + uintptr(directory.VirtualAddress)))
if module.nameExports == nil {
return 0, errors.New("No functions exported by name")
}
if idx, ok := module.nameExports[name]; ok {
if uint32(idx) >= exports.NumberOfFunctions {
return 0, errors.New("Ordinal number too high")
}
// AddressOfFunctions contains the RVAs to the "real" functions.
return module.codeBase + uintptr(*(*uint32)(a2p(module.codeBase + uintptr(exports.AddressOfFunctions) + uintptr(idx)*4))), nil
}
return 0, errors.New("Function not found by name")
}
// ProcAddressByOrdinal returns function address by exported ordinal.
func (module *Module) ProcAddressByOrdinal(ordinal uint16) (uintptr, error) {
directory := module.headerDirectory(IMAGE_DIRECTORY_ENTRY_EXPORT)
if directory.Size == 0 {
return 0, errors.New("No export table found")
}
exports := (*IMAGE_EXPORT_DIRECTORY)(a2p(module.codeBase + uintptr(directory.VirtualAddress)))
if uint32(ordinal) < exports.Base {
return 0, errors.New("Ordinal number too low")
}
idx := ordinal - uint16(exports.Base)
if uint32(idx) >= exports.NumberOfFunctions {
return 0, errors.New("Ordinal number too high")
}
// AddressOfFunctions contains the RVAs to the "real" functions.
return module.codeBase + uintptr(*(*uint32)(a2p(module.codeBase + uintptr(exports.AddressOfFunctions) + uintptr(idx)*4))), nil
}
func alignDown(value, alignment uintptr) uintptr {
return value & ^(alignment - 1)
}
func alignUp(value, alignment uintptr) uintptr {
return (value + alignment - 1) & ^(alignment - 1)
}
func a2p(addr uintptr) unsafe.Pointer {
return unsafe.Pointer(addr)
}
func memcpy(dst, src, size uintptr) {
copy(unsafe.Slice((*byte)(a2p(dst)), size), unsafe.Slice((*byte)(a2p(src)), size))
}