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// Package zipexe attempts to open an executable binary file as a zip file.
package zipexe
import (
"archive/zip"
"debug/elf"
"debug/macho"
"debug/pe"
"errors"
"io"
"os"
)
// Opens a zip file by path.
func Open(path string) (*zip.Reader, error) {
_, rd, err := OpenCloser(path)
return rd, err
}
// OpenCloser is like Open but returns an additional Closer to avoid leaking open files.
func OpenCloser(path string) (io.Closer, *zip.Reader, error) {
file, err := os.Open(path)
if err != nil {
return nil, nil, err
}
finfo, err := file.Stat()
if err != nil {
return nil, nil, err
}
zr, err := NewReader(file, finfo.Size())
if err != nil {
return nil, nil, err
}
return file, zr, nil
}
// Open a zip file, specially handling various binaries that may have been
// augmented with zip data.
func NewReader(rda io.ReaderAt, size int64) (*zip.Reader, error) {
handlers := []func(io.ReaderAt, int64) (*zip.Reader, error){
zip.NewReader,
zipExeReaderMacho,
zipExeReaderElf,
zipExeReaderPe,
}
for _, handler := range handlers {
zfile, err := handler(rda, size)
if err == nil {
return zfile, nil
}
}
return nil, errors.New("Couldn't Open As Executable")
}
// zipExeReaderMacho treats the file as a Mach-O binary
// (Mac OS X / Darwin executable) and attempts to find a zip archive.
func zipExeReaderMacho(rda io.ReaderAt, size int64) (*zip.Reader, error) {
file, err := macho.NewFile(rda)
if err != nil {
return nil, err
}
var max int64
for _, load := range file.Loads {
seg, ok := load.(*macho.Segment)
if ok {
// Check if the segment contains a zip file
if zfile, err := zip.NewReader(seg, int64(seg.Filesz)); err == nil {
return zfile, nil
}
// Otherwise move end of file pointer
end := int64(seg.Offset + seg.Filesz)
if end > max {
max = end
}
}
}
// No zip file within binary, try appended to end
section := io.NewSectionReader(rda, max, size-max)
return zip.NewReader(section, section.Size())
}
// zipExeReaderPe treats the file as a Portable Exectuable binary
// (Windows executable) and attempts to find a zip archive.
func zipExeReaderPe(rda io.ReaderAt, size int64) (*zip.Reader, error) {
file, err := pe.NewFile(rda)
if err != nil {
return nil, err
}
var max int64
for _, sec := range file.Sections {
// Check if this section has a zip file
if zfile, err := zip.NewReader(sec, int64(sec.Size)); err == nil {
return zfile, nil
}
// Otherwise move end of file pointer
end := int64(sec.Offset + sec.Size)
if end > max {
max = end
}
}
// No zip file within binary, try appended to end
section := io.NewSectionReader(rda, max, size-max)
return zip.NewReader(section, section.Size())
}
// zipExeReaderElf treats the file as a ELF binary
// (linux/BSD/etc... executable) and attempts to find a zip archive.
func zipExeReaderElf(rda io.ReaderAt, size int64) (*zip.Reader, error) {
file, err := elf.NewFile(rda)
if err != nil {
return nil, err
}
var max int64
for _, sect := range file.Sections {
if sect.Type == elf.SHT_NOBITS {
continue
}
// Check if this section has a zip file
if zfile, err := zip.NewReader(sect, int64(sect.Size)); err == nil {
return zfile, nil
}
// Otherwise move end of file pointer
end := int64(sect.Offset + sect.Size)
if end > max {
max = end
}
}
// No zip file within binary, try appended to end
section := io.NewSectionReader(rda, max, size-max)
return zip.NewReader(section, section.Size())
}
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