#!/usr/bin/python

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

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)

file = sys.argv[1]
name = sys.argv[2]
size = int(sys.argv[3])

f = open(file, "r+b")
print "Opening %s" % file

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)

        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 == name:
                        print "Name %s, offset: %s, size: %s" % (realname,sh[4], sh[5])
            # BEFORE
                    f.seek(curpos-shsize,0)
            sh = unpack("<IIQQQQIIQQ",f.read(shsize))
            print "NAME: %s, TYPE: %s, FLAGS: %s, ADDR: %s, OFFSET: %s, SIZE: %s, LINK: %s, INFO: %s, ALIGN: %s, SIZE: %s" % (sh[0], sh[1], sh[2], sh[3], sh[4], sh[5], sh[6], sh[7], sh[8], sh[9])
            #
            print "Writing new size: %s at %s" % (size,f.tell())
                    f.seek(curpos-shsize+4+4+8+8+8,0)
            f.write(pack('<Q', size))
            # AFTER
                    f.seek(curpos-shsize,0)
            sh = unpack("<IIQQQQIIQQ",f.read(shsize))
            print "NAME: %s, TYPE: %s, FLAGS: %s, ADDR: %s, OFFSET: %s, SIZE: %s, LINK: %s, INFO: %s, ALIGN: %s, SIZE: %s" % (sh[0], sh[1], sh[2], sh[3], sh[4], sh[5], sh[6], sh[7], sh[8], sh[9])
            #
            break
        f.seek(curpos,0)
else:
    print "Not valid ELF file"

f.close()