#!/usr/bin/python

import sys, os, zlib, io
from struct import pack, unpack

def copyproc(src,dst,size):
    while size:
        block = min(1024,size)
        data = src.read(block)
        dst.write(data)
        size -= block

def read_ntstr(f):
        bytes = 1
        str = ""
        chr = f.read(1)
        while ord(chr):
                str += chr
                bytes += 1
                chr = f.read(1)
        return (str, bytes)

if len(sys.argv) < 2:
    print "Wrong"
    exit(1)

oldfile = sys.argv[1]
newfile = sys.argv[2]

f = open(oldfile, "r+b")
f2 = open(newfile,'r+b')
print "Opening: %s and new %s" % (oldfile,newfile)
f.seek(0,0)

if tuple(unpack("<cccc",f.read(4))) == ('\x7f', 'E', 'L', 'F'):
    f.seek(40,0)
    shoff = (unpack("<Q",f.read(8)))[0]
    f.seek(10,1)
        shsize = (unpack("<H",f.read(2)))[0]
        shnum = (unpack("<H",f.read(2)))[0]
        shidx = (unpack("<H",f.read(2)))[0]
    print "SH Offset: %s, SH Num: %s, SH Size: %s, SH Index: %s" % (shoff, shnum, shsize, shidx)

        f.seek(shoff+(shidx * shsize),0)
        shtextoff = unpack("<IIQQQQIIQQ",f.read(shsize))[4]
        f.seek(shoff,0)

    f2strtaboff = 0

    # Find and copy our string table (it's in front of the section headers, behind the fs block)
        for i in range(shnum):
                sh = unpack("<IIQQQQIIQQ",f.read(shsize))
                curpos = f.tell()
                f.seek(shtextoff+sh[0])
                realname = read_ntstr(f)[0]
        if realname == ".shstrtab":
            print "OLD Name %s, offset: %s, size: %s" % (realname,sh[4], sh[5])
            f.seek(sh[4],0)
            f2.seek(0, io.SEEK_END)
            f2strtaboff = f2.tell()
            copyproc(f,f2,sh[5])
                f.seek(curpos,0)

    # Moving SH headers to new file (strict alignment on 8 seems to be required)
    f2.seek(0, io.SEEK_END)
    f2end = f2.tell()
    if (f2end)%8 != 0 :
            f2end += (8 - (f2end)%8)
            f2.seek(f2end,0)
        print "Shifting to %s" % (f2end)

    f.seek(shoff,0)
    f2shoff = int(f2.tell())
    copyproc(f,f2,shnum*shsize)

    # Done with copy, put the offset @ ELF header
    f2.seek(40,0)
    f2.write(pack('<Q', f2shoff))

    # Fix section headers
    f2.seek(f2shoff+(14*shsize)+24,0)
    print "Writing Partnand offset: %s at: %s" % (f2strtaboff,f2.tell())
    f2.write(pack('<Q', f2strtaboff))

    f2.seek(f2shoff+(15*shsize)+24,0)
    print "Writing SH Text offset: %s at: %s" % (f2strtaboff,f2.tell())
    f2.write(pack('<Q', f2strtaboff))

    print "We installed shoff: %s and strtable: %s in file %s" % (f2shoff, f2strtaboff, newfile)

else:
    print "Not valid ELF file"

f.close()
f2.close()