fritzchecksum 0.0.4

AVM Fritz!Box Checksum Calculator/Overwriter

Update 0.0.4

Support for the new XXXXB64FILE sections in Firmware Versions > 7.12

Introduction

Small pip installable module and Windows GUI (32 & 64 bits) to calculate the CRC of an AVM’s Fritz!Box configuration file.

The command line/gui versions allow to overwrite the CRC directly in the read file or save it to a new file.

Installation

• GUI (look in Releases for the latest zip files)

  The zip files contain standalone versions that need no installation. Any settings/paths will be saved to the ini file in the same directory.

  Simply unpack and run

• Command Line and module

  Simply run:

  pip install fritzchecksum

  The command line utility is also named fritzchecksum

Command Line Utility

The usage is as follows:

$ fritzchecksum --help
usage: fritzchecksum-script.py [-h] [--change | --output OUTPUT] input

FritzChecksum Calculator/Overwriter

positional arguments:
  input                 Write input to output with new CRC

optional arguments:
  -h, --help            show this help message and exit
  --change, -c          Change CRC directly in input file
  --output OUTPUT, -o OUTPUT
                        Write input to output with new CRC

Module fritzchecksum

In your code do things like:

import fritzchecksum

...
...

myexport = open('myexportdatei', 'r')
oldcrc, newcrc = fritzchecksum.calc_crc32(myexport)

...

The module contains two Python 1st class citizens:

• function calc_crc32(fin, fout=None, logcb=log_null)

  Calculates the CRC of a Fritz!Box configuration export file and writes the new CRC sum to a new configuration file

  Accepts:

  • fin: a file-like

  • fout: None or a file-like object. If a file, then the input will be written to the output with the new calculated CRC

  • logcb (default: log_null which is an empty stub) a logger which must a accepts *args (print will work)

  Returns:

  (oldcrc, newcrc) -> tuple

  oldcrc and newcrc will be strings representing a CRC32 in hexadecimal format if everything went fine

  oldcrc can be None which means an IOError exception has been raised and the operation has not completed successfully. In that case the 2nd value in the tuple contains the raised exception

  Note: the escape character ‘' is escaped iself in some of the lines. CRC calculation will be wrong if the character is not un-escaped.

  The file is composed of the following:

  • A global “CONFIGURATION EXPORT” section

    Some variables (a=b) may be defined at this level. This definition contributes to the the CRC calculation by concatenating a and b and null terminating the result.

  • Subsections:

    The name (null terminated) of the subsection contributes to the CRC calculation

    • XXXBINFILE Section

      Lines represent hexadecimal values. The values (binary converted) are used directly in the calculation of the CRC (stripping eol before)

    • CFGFILE Section

      It is a textfile embedded in the larger export file. All lines including ‘n’ contribute to the CRC except the last line which must be stripped of the EOL character before being included in the CRC calculation

• class ExportFile

  Class to encapsulate the parsing of an export file and overwriting of the CRC value

  After loading a file it keeps the loaded content in an internal fout

  With the following methods:

  • load(self, fin, out=True)

    Loads from a file-like/string object fin and will update internal status, error, oldcrc and newcrc

    if out is False no internal buffering of the loaded input will be made

    Returns:

    tuple -> (status, error)

    If status is ST_OK (True) error will be None If status is ST_ERROR (False) error will be the raised exception

  • load_file(self, fin, out=True)

    Loads from a file-like object fin and will update internal status, error, oldcrc and newcrc

    if out is False no internal buffering of the loaded input will be made

    Returns:

    tuple -> (status, error)

    If status is ST_OK (True) error will be None If status is ST_ERROR (False) error will be the raised exception

  • save(self, fout)

    Writes the internal self.fout file to a file-like/string fout

    Returns:

    tuple -> (status, error)

    If status is ST_OK (True) error will be None If status is ST_ERROR (False) error will be the raised exception

  • save_file(self, fout)

    Writes the internal self.fout file to a file-like object fout

    Returns:

    tuple -> (status, error)

    If status is ST_OK (True) error will be None If status is ST_ERROR (False) error will be the raised exception