🐶️ lext

Length Extension Attack-tool
SHA1, SHA256, SHA512, MD5

Simple install

git clone https://github.com/mumubebe/lext.git
cd lext/

Run as module:

$ python3 -m lext \
      --data 'count=10&lat=37.351&user_id=1&long=-119.827&waffle=eggo' \
      --inject '&waffle=liege' \
      --signature '6d5f807e23db210bc254a28be2d6759a0f5f5d99' \
      --secret_length 14 \
      --method 'sha1'
  
b'count=10&lat=37.351&user_id=1&long=-119.827&waffle=eggo\x80\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x02(&waffle=liege'
0e41270260895979317fff3898ab85668953aaa2

or

>>> from lext import lext
>>> inj, sig = lext(
...     data=b"count=10&lat=37.351&user_id=1&long=-119.827&waffle=eggo",
...     inject=b"&waffle=liege",
...     signature="6d5f807e23db210bc254a28be2d6759a0f5f5d99",
...     secret_length=14,
...     method="sha1"
... )
>>> print(sig)
0e41270260895979317fff3898ab85668953aaa2
>>> print(inj)
b'count=10&lat=37.351&user_id=1&long=-119.827&waffle=eggo\x80\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x02(&waffle=liege'

Note that output format for signature and data differs as default; signature as hex and data as bytes string.

About

usage: __main__.py [-h] [-m {sha1,sha256,sha512,md5}] -d DATA -i INJECT -s SIGNATURE -l SECRET_LENGTH [--no-signature] [--no-outputdata]
                   [--base64]

Length Extension Attack-tool

optional arguments:
  -h, --help            show this help message and exit
  -m {sha1,sha256,sha512,md5}, --method {sha1,sha256,sha512,md5}
                        Hash method
  -d DATA, --data DATA  The original data known message from server. This data is prepend with a hidden secret unknown to client.
  -i INJECT, --inject INJECT
                        Additional message to append to the original data
  -s SIGNATURE, --signature SIGNATURE
                        Signature of original data
  -l SECRET_LENGTH, --secret_length SECRET_LENGTH
                        Length of the hidden secret that is hidden from client
  --no-signature        Ignore output return of signature
  --no-outputdata       Ignore output return of new data message
  --base64              Format output as base64. Note that both signature and data will be converted (default for signature is hex string
                        and byte string for data output)

Note that the implemented hash algorithms are not optimized in any way.

Similar tools:
https://github.com/stephenbradshaw/hlextend
https://github.com/bwall/HashPump