/
file.go
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/
file.go
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// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// Package pe implements access to PE (Microsoft Windows Portable Executable) files.
package pe
import (
"bytes"
"compress/zlib"
"debug/dwarf"
"encoding/binary"
"fmt"
"io"
"os"
"strings"
)
// Avoid use of post-Go 1.4 io features, to make safe for toolchain bootstrap.
const (
seekStart = 0
seekCurrent = 1
)
// A File represents an open PE file.
type File struct {
DosHeader
DosExists bool
DosStub [64]byte // TODO(capnspacehook) make slice and correctly parse any DOS stub
RichHeader []byte
FileHeader
OptionalHeader interface{} // of type *OptionalHeader32 or *OptionalHeader64
Sections []*Section
BaseRelocationTable *[]RelocationTableEntry
Symbols []*Symbol // COFF symbols with auxiliary symbol records removed
COFFSymbols []COFFSymbol // all COFF symbols (including auxiliary symbol records)
StringTable StringTable
CertificateTable []byte
OptionalHeaderOffset int64 // offset of the start of the Optional Header
InsertionAddr uint32
InsertionBytes []byte
Net Net //If a managed executable, Net provides an interface to some of the metadata
closer io.Closer
}
// Open opens the named file using os.Open and prepares it for use as a PE binary.
func Open(name string) (*File, error) {
f, err := os.Open(name)
if err != nil {
return nil, err
}
ff, err := NewFile(f)
if err != nil {
f.Close()
return nil, err
}
ff.closer = f
return ff, nil
}
// Close closes the File.
// If the File was created using NewFile directly instead of Open,
// Close has no effect.
func (f *File) Close() error {
var err error
if f.closer != nil {
err = f.closer.Close()
f.closer = nil
}
return err
}
var (
sizeofOptionalHeader32 = uint16(binary.Size(OptionalHeader32{}))
sizeofOptionalHeader64 = uint16(binary.Size(OptionalHeader64{}))
)
// TODO(brainman): add Load function, as a replacement for NewFile, that does not call removeAuxSymbols (for performance)
// NewFile creates a new pe.File for accessing a PE binary file in an underlying reader.
func NewFile(r io.ReaderAt) (*File, error) {
return newFileInternal(r, false)
}
// NewFileFromMemory creates a new pe.File for accessing a PE binary in-memory image in an underlying reader.
func NewFileFromMemory(r io.ReaderAt) (*File, error) {
return newFileInternal(r, true)
}
// NewFile creates a new File for accessing a PE binary in an underlying reader.
func newFileInternal(r io.ReaderAt, memoryMode bool) (*File, error) {
f := new(File)
sr := io.NewSectionReader(r, 0, 1<<63-1)
binary.Read(sr, binary.LittleEndian, &f.DosHeader)
dosHeaderSize := binary.Size(f.DosHeader)
if dosHeaderSize < int(f.DosHeader.AddressOfNewExeHeader) {
binary.Read(sr, binary.LittleEndian, &f.DosStub)
f.DosExists = true
} else {
f.DosExists = false
}
possibleRichHeaderStart := dosHeaderSize
if f.DosExists {
possibleRichHeaderStart += binary.Size(f.DosStub)
}
possibleRichHeaderEnd := int(f.DosHeader.AddressOfNewExeHeader)
if possibleRichHeaderEnd > possibleRichHeaderStart {
richHeader := make([]byte, possibleRichHeaderEnd-possibleRichHeaderStart)
binary.Read(sr, binary.LittleEndian, richHeader)
if richIndex := bytes.Index(richHeader, []byte("Rich")); richIndex != -1 {
f.RichHeader = richHeader[:richIndex+8]
}
}
var peHeaderOffset int64
if f.DosHeader.MZSignature == 0x5a4d {
peHeaderOffset = int64(f.DosHeader.AddressOfNewExeHeader)
var sign [4]byte
r.ReadAt(sign[:], peHeaderOffset)
if !(sign[0] == 'P' && sign[1] == 'E' && sign[2] == 0 && sign[3] == 0) {
return nil, fmt.Errorf("Invalid PE COFF file signature of %v", sign)
}
peHeaderOffset += int64(4)
} else {
peHeaderOffset = int64(0)
}
sr.Seek(peHeaderOffset, seekStart)
if err := binary.Read(sr, binary.LittleEndian, &f.FileHeader); err != nil {
return nil, err
}
switch f.FileHeader.Machine {
case IMAGE_FILE_MACHINE_UNKNOWN, IMAGE_FILE_MACHINE_ARMNT, IMAGE_FILE_MACHINE_AMD64, IMAGE_FILE_MACHINE_I386:
default:
return nil, fmt.Errorf("Unrecognised COFF file header machine value of 0x%x", f.FileHeader.Machine)
}
var err error
if memoryMode {
//get strings table location - offset is wrong in the header because we are in memory mode. Can we fix it? Yes we can!
restore, err := sr.Seek(0, seekCurrent)
if err != nil {
return nil, fmt.Errorf("Had a bad time getting restore point: %v", err)
}
//seek to table start (skip the headers)
sr.Seek(peHeaderOffset+int64(binary.Size(f.FileHeader))+int64(f.FileHeader.SizeOfOptionalHeader), seekStart)
//iterate through the sections to find the raw offset value that matches the original symbol table value
for i := 0; i < int(f.FileHeader.NumberOfSections); i++ {
sh := new(SectionHeader32)
if err := binary.Read(sr, binary.LittleEndian, sh); err != nil {
return nil, err
}
//original offset matches the pointer to the symbol table, update the header so other things can reference it good again
if sh.PointerToRawData == f.FileHeader.PointerToSymbolTable {
f.FileHeader.PointerToSymbolTable = sh.VirtualAddress
}
}
//restore the original location of sr (this shouldn't actually be required, but just in case)
sr.Seek(restore, seekStart)
}
// Read string table.
f.StringTable, err = readStringTable(&f.FileHeader, sr)
if err != nil {
return nil, err
}
// Read symbol table.
f.COFFSymbols, err = readCOFFSymbols(&f.FileHeader, sr)
if err != nil {
return nil, err
}
f.Symbols, err = removeAuxSymbols(f.COFFSymbols, f.StringTable)
if err != nil {
return nil, err
}
// Read optional header.
f.OptionalHeaderOffset = peHeaderOffset + int64(binary.Size(f.FileHeader))
sr.Seek(f.OptionalHeaderOffset, seekStart)
var oh32 OptionalHeader32
var oh64 OptionalHeader64
switch f.FileHeader.SizeOfOptionalHeader {
case sizeofOptionalHeader32:
if err := binary.Read(sr, binary.LittleEndian, &oh32); err != nil {
return nil, err
}
if oh32.Magic != 0x10b { // PE32
return nil, fmt.Errorf("pe32 optional header has unexpected Magic of 0x%x", oh32.Magic)
}
f.OptionalHeader = &oh32
case sizeofOptionalHeader64:
if err := binary.Read(sr, binary.LittleEndian, &oh64); err != nil {
return nil, err
}
if oh64.Magic != 0x20b { // PE32+
return nil, fmt.Errorf("pe32+ optional header has unexpected Magic of 0x%x", oh64.Magic)
}
f.OptionalHeader = &oh64
}
// Process sections.
f.Sections = make([]*Section, f.FileHeader.NumberOfSections)
for i := 0; i < int(f.FileHeader.NumberOfSections); i++ {
sh := new(SectionHeader32)
if err := binary.Read(sr, binary.LittleEndian, sh); err != nil {
return nil, err
}
name, err := sh.fullName(f.StringTable)
if err != nil {
return nil, err
}
s := new(Section)
s.SectionHeader = SectionHeader{
Name: name,
OriginalName: sh.Name,
VirtualSize: sh.VirtualSize,
VirtualAddress: sh.VirtualAddress,
Size: sh.SizeOfRawData,
Offset: sh.PointerToRawData,
PointerToRelocations: sh.PointerToRelocations,
PointerToLineNumbers: sh.PointerToLineNumbers,
NumberOfRelocations: sh.NumberOfRelocations,
NumberOfLineNumbers: sh.NumberOfLineNumbers,
Characteristics: sh.Characteristics,
}
r2 := r
if sh.PointerToRawData == 0 { // .bss must have all 0s
r2 = zeroReaderAt{}
}
if !memoryMode {
s.sr = io.NewSectionReader(r2, int64(s.SectionHeader.Offset), int64(s.SectionHeader.Size))
} else {
s.sr = io.NewSectionReader(r2, int64(s.SectionHeader.VirtualAddress), int64(s.SectionHeader.Size))
}
s.ReaderAt = s.sr
f.Sections[i] = s
}
for i := range f.Sections {
var err error
f.Sections[i].Relocs, err = readRelocs(&f.Sections[i].SectionHeader, sr)
if err != nil {
return nil, err
}
}
// Read Base Relocation Block and Items
f.BaseRelocationTable, err = f.readBaseRelocationTable()
if err != nil {
return nil, err
}
// Read certificate table (only in disk mode)
if !memoryMode {
f.CertificateTable, err = readCertTable(f, sr)
if err != nil {
return nil, err
}
}
//fill net info
if f.IsManaged() {
var va, size uint32
//determine location of the COM descriptor directory
switch v := f.OptionalHeader.(type) {
case *OptionalHeader32:
va = v.DataDirectory[IMAGE_DIRECTORY_ENTRY_COM_DESCRIPTOR].VirtualAddress
size = v.DataDirectory[IMAGE_DIRECTORY_ENTRY_COM_DESCRIPTOR].Size
case *OptionalHeader64:
va = v.DataDirectory[IMAGE_DIRECTORY_ENTRY_COM_DESCRIPTOR].VirtualAddress
size = v.DataDirectory[IMAGE_DIRECTORY_ENTRY_COM_DESCRIPTOR].Size
}
//I'm unsure how to get a reader (not a readerat) for a particular thing, so copying buffers around.. this could be more optimal
buff := make([]byte, size)
//none of these reads have errors being caught either, which is probably not ideal
if !memoryMode {
r.ReadAt(buff, int64(f.RVAToFileOffset(va)))
} else {
r.ReadAt(buff, int64(va))
}
binary.Read(bytes.NewReader(buff), binary.LittleEndian, &f.Net.NetDirectory)
//Now that we have the COR20 header (COM descriptor directory header), we can get the metadata section header, which has the version
buff = make([]byte, f.Net.NetDirectory.MetaDataSize)
//again, none of the reads are error checked :shrug:
if !memoryMode {
r.ReadAt(buff, int64(f.RVAToFileOffset(f.Net.NetDirectory.MetaDataRVA)))
} else {
r.ReadAt(buff, int64(f.Net.NetDirectory.MetaDataRVA))
}
f.Net.MetaData, _ = newMetadataHeader(bytes.NewReader(buff))
}
return f, nil
}
// zeroReaderAt is ReaderAt that reads 0s.
type zeroReaderAt struct{}
// ReadAt writes len(p) 0s into p.
func (w zeroReaderAt) ReadAt(p []byte, off int64) (n int, err error) {
for i := range p {
p[i] = 0
}
return len(p), nil
}
// getString extracts a string from symbol string table.
func getString(section []byte, start int) (string, bool) {
if start < 0 || start >= len(section) {
return "", false
}
for end := start; end < len(section); end++ {
if section[end] == 0 {
return string(section[start:end]), true
}
}
return "", false
}
// Section returns the first section with the given name, or nil if no such
// section exists.
func (f *File) Section(name string) *Section {
for _, s := range f.Sections {
if s.Name == name {
return s
}
}
return nil
}
func (f *File) DWARF() (*dwarf.Data, error) {
dwarfSuffix := func(s *Section) string {
switch {
case strings.HasPrefix(s.Name, ".debug_"):
return s.Name[7:]
case strings.HasPrefix(s.Name, ".zdebug_"):
return s.Name[8:]
default:
return ""
}
}
// sectionData gets the data for s and checks its size.
sectionData := func(s *Section) ([]byte, error) {
b, err := s.Data()
if err != nil && uint32(len(b)) < s.Size {
return nil, err
}
if 0 < s.VirtualSize && s.VirtualSize < s.Size {
b = b[:s.VirtualSize]
}
if len(b) >= 12 && string(b[:4]) == "ZLIB" {
dlen := binary.BigEndian.Uint64(b[4:12])
dbuf := make([]byte, dlen)
r, err := zlib.NewReader(bytes.NewBuffer(b[12:]))
if err != nil {
return nil, err
}
if _, err := io.ReadFull(r, dbuf); err != nil {
return nil, err
}
if err := r.Close(); err != nil {
return nil, err
}
b = dbuf
}
return b, nil
}
// There are many other DWARF sections, but these
// are the ones the debug/dwarf package uses.
// Don't bother loading others.
var dat = map[string][]byte{"abbrev": nil, "info": nil, "str": nil, "line": nil, "ranges": nil}
for _, s := range f.Sections {
suffix := dwarfSuffix(s)
if suffix == "" {
continue
}
if _, ok := dat[suffix]; !ok {
continue
}
b, err := sectionData(s)
if err != nil {
return nil, err
}
dat[suffix] = b
}
d, err := dwarf.New(dat["abbrev"], nil, nil, dat["info"], dat["line"], nil, dat["ranges"], dat["str"])
if err != nil {
return nil, err
}
// Look for DWARF4 .debug_types sections.
for i, s := range f.Sections {
suffix := dwarfSuffix(s)
if suffix != "types" {
continue
}
b, err := sectionData(s)
if err != nil {
return nil, err
}
err = d.AddTypes(fmt.Sprintf("types-%d", i), b)
if err != nil {
return nil, err
}
}
return d, nil
}
// FormatError is unused.
// The type is retained for compatibility.
type FormatError struct {
}
func (e *FormatError) Error() string {
return "unknown error"
}
// RVAToFileOffset Converts a Relative offset to the actual offset in the file.
func (f *File) RVAToFileOffset(rva uint32) uint32 {
var offset uint32
for _, section := range f.Sections {
if rva >= section.SectionHeader.VirtualAddress && rva <= section.SectionHeader.VirtualAddress+section.SectionHeader.Size {
offset = section.SectionHeader.Offset + (rva - section.SectionHeader.VirtualAddress)
}
}
return offset
}
// IsManaged returns true if the loaded PE file references the CLR header (aka is a .net exe)
func (f *File) IsManaged() bool {
switch v := f.OptionalHeader.(type) {
case *OptionalHeader32:
if v.DataDirectory[IMAGE_DIRECTORY_ENTRY_COM_DESCRIPTOR].VirtualAddress != 0 {
return true
}
case *OptionalHeader64:
if v.DataDirectory[IMAGE_DIRECTORY_ENTRY_COM_DESCRIPTOR].VirtualAddress != 0 {
return true
}
}
return false
}