// 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 (
"debug/dwarf"
"encoding/binary"
"errors"
"fmt"
"io"
"os"
"strconv"
)
// A File represents an open PE file.
type File struct {
FileHeader
OptionalHeader interface{} // of type *OptionalHeader32 or *OptionalHeader64
Sections []*Section
Symbols []*Symbol
closer io.Closer
}
type SectionHeader struct {
Name string
VirtualSize uint32
VirtualAddress uint32
Size uint32
Offset uint32
PointerToRelocations uint32
PointerToLineNumbers uint32
NumberOfRelocations uint16
NumberOfLineNumbers uint16
Characteristics uint32
}
type Section struct {
SectionHeader
// Embed ReaderAt for ReadAt method.
// Do not embed SectionReader directly
// to avoid having Read and Seek.
// If a client wants Read and Seek it must use
// Open() to avoid fighting over the seek offset
// with other clients.
io.ReaderAt
sr *io.SectionReader
}
type Symbol struct {
Name string
Value uint32
SectionNumber int16
Type uint16
StorageClass uint8
}
type ImportDirectory struct {
OriginalFirstThunk uint32
TimeDateStamp uint32
ForwarderChain uint32
Name uint32
FirstThunk uint32
dll string
}
// Data reads and returns the contents of the PE section.
func (s *Section) Data() ([]byte, error) {
dat := make([]byte, s.sr.Size())
n, err := s.sr.ReadAt(dat, 0)
if n == len(dat) {
err = nil
}
return dat[0:n], err
}
// Open returns a new ReadSeeker reading the PE section.
func (s *Section) Open() io.ReadSeeker { return io.NewSectionReader(s.sr, 0, 1<<63-1) }
type FormatError struct {
off int64
msg string
val interface{}
}
func (e *FormatError) Error() string {
msg := e.msg
if e.val != nil {
msg += fmt.Sprintf(" '%v'", e.val)
}
msg += fmt.Sprintf(" in record at byte %#x", e.off)
return msg
}
// 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{}))
)
// NewFile creates a new File for accessing a PE binary in an underlying reader.
func NewFile(r io.ReaderAt) (*File, error) {
f := new(File)
sr := io.NewSectionReader(r, 0, 1<<63-1)
var dosheader [96]byte
if _, err := r.ReadAt(dosheader[0:], 0); err != nil {
return nil, err
}
var base int64
if dosheader[0] == 'M' && dosheader[1] == 'Z' {
signoff := int64(binary.LittleEndian.Uint32(dosheader[0x3c:]))
var sign [4]byte
r.ReadAt(sign[:], signoff)
if !(sign[0] == 'P' && sign[1] == 'E' && sign[2] == 0 && sign[3] == 0) {
return nil, errors.New("Invalid PE File Format.")
}
base = signoff + 4
} else {
base = int64(0)
}
sr.Seek(base, os.SEEK_SET)
if err := binary.Read(sr, binary.LittleEndian, &f.FileHeader); err != nil {
return nil, err
}
if f.FileHeader.Machine != IMAGE_FILE_MACHINE_UNKNOWN && f.FileHeader.Machine != IMAGE_FILE_MACHINE_AMD64 && f.FileHeader.Machine != IMAGE_FILE_MACHINE_I386 {
return nil, errors.New("Invalid PE File Format.")
}
var ss []byte
if f.FileHeader.NumberOfSymbols > 0 {
// Get COFF string table, which is located at the end of the COFF symbol table.
sr.Seek(int64(f.FileHeader.PointerToSymbolTable+COFFSymbolSize*f.FileHeader.NumberOfSymbols), os.SEEK_SET)
var l uint32
if err := binary.Read(sr, binary.LittleEndian, &l); err != nil {
return nil, err
}
ss = make([]byte, l)
if _, err := r.ReadAt(ss, int64(f.FileHeader.PointerToSymbolTable+COFFSymbolSize*f.FileHeader.NumberOfSymbols)); err != nil {
return nil, err
}
// Process COFF symbol table.
sr.Seek(int64(f.FileHeader.PointerToSymbolTable), os.SEEK_SET)
aux := uint8(0)
for i := 0; i < int(f.FileHeader.NumberOfSymbols); i++ {
cs := new(COFFSymbol)
if err := binary.Read(sr, binary.LittleEndian, cs); err != nil {
return nil, err
}
if aux > 0 {
aux--
continue
}
var name string
if cs.Name[0] == 0 && cs.Name[1] == 0 && cs.Name[2] == 0 && cs.Name[3] == 0 {
si := int(binary.LittleEndian.Uint32(cs.Name[4:]))
name, _ = getString(ss, si)
} else {
name = cstring(cs.Name[:])
}
aux = cs.NumberOfAuxSymbols
s := &Symbol{
Name: name,
Value: cs.Value,
SectionNumber: cs.SectionNumber,
Type: cs.Type,
StorageClass: cs.StorageClass,
}
f.Symbols = append(f.Symbols, s)
}
}
// Read optional header.
sr.Seek(base, os.SEEK_SET)
if err := binary.Read(sr, binary.LittleEndian, &f.FileHeader); err != nil {
return nil, err
}
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
}
var name string
if sh.Name[0] == '\x2F' {
si, _ := strconv.Atoi(cstring(sh.Name[1:]))
name, _ = getString(ss, si)
} else {
name = cstring(sh.Name[0:])
}
s := new(Section)
s.SectionHeader = SectionHeader{
Name: 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,
}
s.sr = io.NewSectionReader(r, int64(s.SectionHeader.Offset), int64(s.SectionHeader.Size))
s.ReaderAt = s.sr
f.Sections[i] = s
}
return f, nil
}
func cstring(b []byte) string {
var i int
for i = 0; i < len(b) && b[i] != 0; i++ {
}
return string(b[0:i])
}
// 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) {
// There are many other DWARF sections, but these
// are the ones the debug/dwarf package uses.
// Don't bother loading others.
var names = [...]string{"abbrev", "info", "line", "str"}
var dat [len(names)][]byte
for i, name := range names {
name = ".debug_" + name
s := f.Section(name)
if s == nil {
continue
}
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]
}
dat[i] = b
}
abbrev, info, line, str := dat[0], dat[1], dat[2], dat[3]
return dwarf.New(abbrev, nil, nil, info, line, nil, nil, str)
}
// ImportedSymbols returns the names of all symbols
// referred to by the binary f that are expected to be
// satisfied by other libraries at dynamic load time.
// It does not return weak symbols.
func (f *File) ImportedSymbols() ([]string, error) {
pe64 := f.Machine == IMAGE_FILE_MACHINE_AMD64
ds := f.Section(".idata")
if ds == nil {
// not dynamic, so no libraries
return nil, nil
}
d, err := ds.Data()
if err != nil {
return nil, err
}
var ida []ImportDirectory
for len(d) > 0 {
var dt ImportDirectory
dt.OriginalFirstThunk = binary.LittleEndian.Uint32(d[0:4])
dt.Name = binary.LittleEndian.Uint32(d[12:16])
dt.FirstThunk = binary.LittleEndian.Uint32(d[16:20])
d = d[20:]
if dt.OriginalFirstThunk == 0 {
break
}
ida = append(ida, dt)
}
names, _ := ds.Data()
var all []string
for _, dt := range ida {
dt.dll, _ = getString(names, int(dt.Name-ds.VirtualAddress))
d, _ = ds.Data()
// seek to OriginalFirstThunk
d = d[dt.OriginalFirstThunk-ds.VirtualAddress:]
for len(d) > 0 {
if pe64 { // 64bit
va := binary.LittleEndian.Uint64(d[0:8])
d = d[8:]
if va == 0 {
break
}
if va&0x8000000000000000 > 0 { // is Ordinal
// TODO add dynimport ordinal support.
} else {
fn, _ := getString(names, int(uint32(va)-ds.VirtualAddress+2))
all = append(all, fn+":"+dt.dll)
}
} else { // 32bit
va := binary.LittleEndian.Uint32(d[0:4])
d = d[4:]
if va == 0 {
break
}
if va&0x80000000 > 0 { // is Ordinal
// TODO add dynimport ordinal support.
//ord := va&0x0000FFFF
} else {
fn, _ := getString(names, int(va-ds.VirtualAddress+2))
all = append(all, fn+":"+dt.dll)
}
}
}
}
return all, nil
}
// ImportedLibraries returns the names of all libraries
// referred to by the binary f that are expected to be
// linked with the binary at dynamic link time.
func (f *File) ImportedLibraries() ([]string, error) {
// TODO
// cgo -dynimport don't use this for windows PE, so just return.
return nil, nil
}