Extract logic to separate package, move command to cmd/goupx

1 files changed, 159 insertions, 0 deletions

diff --git a/hemfix/hemfix.go b/hemfix/hemfix.go
new file mode 100644
index 0000000..2425df1
--- /dev/null
+++ b/hemfix/hemfix.go
@@ -0,0 +1,159 @@
+package hemfix
+
+/*
+
+goupx: Fix compiled go binaries so that they can be packed by
+       the universal packer for executables (upx)
+
+Copyright (c) 2012 Peter Waller <[email protected]>
+All rights reserved.
+
+Based on code found at http://sourceforge.net/tracker/?func=detail&atid=102331&aid=3408066&group_id=2331
+
+Based on hemfix.c Copyright (C) 2012 John Reiser, BitWagon Software LLC
+
+  This program is free software; you can redistribute it and/or modify
+  it under the terms of the GNU General Public License as published by
+  the Free Software Foundation; either version 3, or (at your option)
+  any later version.
+
+  This program is distributed in the hope that it will be useful,
+  but WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+  GNU General Public License for more details.
+
+  You should have received a copy of the GNU General Public License
+  along with this program; if not, write to the Free Software Foundation,
+  Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+*/
+
+import (
+	ELF "debug/elf"
+	"encoding/binary"
+	"errors"
+	"io"
+	"log"
+	"os"
+)
+
+// The functions gethdr and writephdr are heavily influenced by code found at
+// http://golang.org/src/pkg/debug/elf/file.go
+
+// Returns the Prog header offset and size
+func gethdr(f *ELF.File, sr io.ReadSeeker) (int64, int, error) {
+	sr.Seek(0, os.SEEK_SET)
+
+	switch f.Class {
+	case ELF.ELFCLASS32:
+		hdr := new(ELF.Header32)
+		if err := binary.Read(sr, f.ByteOrder, hdr); err != nil {
+			return 0, 0, err
+		}
+		return int64(hdr.Phoff), int(hdr.Phentsize), nil
+
+	case ELF.ELFCLASS64:
+		hdr := new(ELF.Header64)
+		if err := binary.Read(sr, f.ByteOrder, hdr); err != nil {
+			return 0, 0, err
+		}
+		return int64(hdr.Phoff), int(hdr.Phentsize), nil
+	}
+	return 0, 0, errors.New("Unexpected ELF class")
+}
+
+// Write out a Prog header to an elf with a given destination
+// Writes out `p` to `sw` at `dst` using information from `f`
+func writephdr(f *ELF.File, dst int64, sw io.WriteSeeker, p *ELF.Prog) error {
+	sw.Seek(dst, os.SEEK_SET)
+
+	switch f.Class {
+	case ELF.ELFCLASS32:
+		hdr := ELF.Prog32{
+			Type:   uint32(p.Type),
+			Flags:  uint32(p.Flags),
+			Off:    uint32(p.Off),
+			Vaddr:  uint32(p.Vaddr),
+			Paddr:  uint32(p.Paddr),
+			Filesz: uint32(p.Filesz),
+			Memsz:  uint32(p.Memsz),
+			Align:  uint32(p.Align),
+		}
+		if err := binary.Write(sw, f.ByteOrder, hdr); err != nil {
+			return err
+		}
+
+	case ELF.ELFCLASS64:
+		hdr := ELF.Prog64{
+			Type:   uint32(p.Type),
+			Flags:  uint32(p.Flags),
+			Off:    p.Off,
+			Vaddr:  p.Vaddr,
+			Paddr:  p.Paddr,
+			Filesz: p.Filesz,
+			Memsz:  p.Memsz,
+			Align:  p.Align,
+		}
+		if err := binary.Write(sw, f.ByteOrder, hdr); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+func fixelf(elf *ELF.File, fd io.ReadWriteSeeker) error {
+
+	// Determine where to write header (need
+	off, sz, err := gethdr(elf, fd)
+	if err != nil {
+		return err
+	}
+
+	for i := range elf.Progs {
+		p := elf.Progs[i]
+
+		if p.ProgHeader.Type != ELF.PT_LOAD {
+			// Only consider PT_LOAD sections
+			continue
+		}
+
+		mask := -p.Align
+		if ^mask&p.Vaddr != 0 && (^mask&(p.Vaddr-p.Off)) == 0 {
+			log.Printf("Hemming PT_LOAD section")
+			hem := ^mask & p.Off
+			p.Off -= hem
+			p.Vaddr -= hem
+			if p.Paddr != 0 {
+				p.Paddr -= hem
+			}
+			p.Filesz += hem
+			p.Memsz += hem
+
+			dst := off + int64(sz*i)
+			writephdr(elf, dst, fd, p)
+		}
+	}
+	return nil
+}
+
+func FixFile(filename string) error {
+	fd, err := os.OpenFile(filename, os.O_RDWR, 0)
+	if err != nil {
+		return err
+	}
+	defer fd.Close()
+
+	elf, err := ELF.NewFile(fd)
+	if err != nil {
+		log.Print("Failed to parse ELF. This can happen if the binary is already packed.")
+		return err
+	}
+	defer elf.Close()
+
+	log.Printf("%+v", elf.FileHeader)
+	err = fixelf(elf, fd)
+	if err != nil {
+		log.Fatal("Failure to read ELF header")
+		return err
+	}
+	return nil
+}