codec – Data transformation

This module contains functions that allow you to manipulate, encode or decode strings and byte sequences.

pwnypack.codec.xor(key, data)

Perform cyclical exclusive or operations on data.

The key can be a an integer (0 <= key < 256) or a byte sequence. If the key is smaller than the provided data, the key will be repeated.

Parameters:

• key (int or bytes) – The key to xor data with.
• data (bytes) – The data to perform the xor operation on.

Returns:

The result of the exclusive or operation.

Return type:

bytes

Examples

>>> from pwny import *
>>> xor(5, b'ABCD')
b'DGFA'
>>> xor(5, b'DGFA')
b'ABCD'
>>> xor(b'pwny', b'ABCDEFGHIJKLMNOPQRSTUVWXYZ')
b'15-=51)19=%5=9!)!%=-%!9!)-'
>>> xor(b'pwny', b'15-=51)19=%5=9!)!%=-%!9!)-')
b'ABCDEFGHIJKLMNOPQRSTUVWXYZ'

pwnypack.codec.find_xor_mask(data, alphabet=None, max_depth=3, min_depth=0, iv=None)

Produce a series of bytestrings that when XORed together end up being equal to data and only contain characters from the giving alphabet. The initial state (or previous state) can be given as iv.

Parameters:

• data (bytes) – The data to recreate as a series of XOR operations.
• alphabet (bytes) – The bytestring containing the allowed characters for the XOR values. If None, all characters except NUL bytes, carriage returns and newlines will be allowed.
• max_depth (int) – The maximum depth to look for a solution.
• min_depth (int) – The minimum depth to look for a solution.
• iv (bytes) – Initialization vector. If None, it will be assumed the operation starts at an all zero string.

Returns:

A list of bytestrings that, when XOR’ed with iv (or just eachother if iv` is not providede) will be the same as ``data.

Examples

Produce a series of strings that when XORed together will result in the string ‘pwnypack’ using only ASCII characters in the range 65 to 96:

>>> from pwny import *
>>> find_xor_mask('pwnypack', alphabet=''.join(chr(c) for c in range(65, 97)))
[b'````````', b'AAAAABAA', b'QVOXQCBJ']
>>> xor(xor(b'````````', b'AAAAABAA'), b'QVOXQCBJ')
'pwnypack'

pwnypack.codec.rot13(d)

Rotate all characters in the alphabets A-Z and a-z by 13 positions in the alphabet. This is a caesar() shift of 13 along the fixed alphabets A-Z and a-z.

Parameters:d (str) – The string to the apply the cipher to. Returns:The string with the rot13 cipher applied. Return type:str

Examples

>>> rot13('whax')
'junk'
>>> rot13('junk')
'whax'

pwnypack.codec.caesar(shift, data, shift_ranges=('az', 'AZ'))

Apply a caesar cipher to a string.

The caesar cipher is a substition cipher where each letter in the given alphabet is replaced by a letter some fixed number down the alphabet.

If shift is 1, A will become B, B will become C, etc…

You can define the alphabets that will be shift by specifying one or more shift ranges. The characters will than be shifted within the given ranges.

Parameters:

• shift (int) – The shift to apply.
• data (str) – The string to apply the cipher to.
• shift_ranges (list of str) – Which alphabets to shift.

Returns:

The string with the caesar cipher applied.

Return type:

str

Examples

>>> caesar(16, 'Pwnypack')
'Fmdofqsa'
>>> caesar(-16, 'Fmdofqsa')
'Pwnypack'
>>> caesar(16, 'PWNYpack', shift_ranges=('AZ',))
'FMDOpack'
>>> caesar(16, 'PWNYpack', shift_ranges=('Az',))
'`g^iFqsA'

pwnypack.codec.enhex(d, separator='')

Convert bytes to their hexadecimal representation, optionally joined by a given separator.

Parameters:

• d (bytes) – The data to convert to hexadecimal representation.
• separator (str) – The separator to insert between hexadecimal tuples.

Returns:

The hexadecimal representation of d.

Return type:

str

Examples

>>> from pwny import *
>>> enhex(b'pwnypack')
'70776e797061636b'
>>> enhex(b'pwnypack', separator=' ')
'70 77 6e 79 70 61 63 6b'

pwnypack.codec.dehex(d)

Convert a hexadecimal representation of a byte sequence to bytes. All non-hexadecimal characters will be removed from the input.

Parameters:d (str) – The string of hexadecimal tuples. Returns:The byte sequence represented by d. Return type:bytes

Examples

>>> from pwny import *
>>> dehex('70776e797061636b')
b'pwnypack'
>>> dhex('70 77 6e 79 70 61 63 6b')
b'pwnypack'

pwnypack.codec.enb64(d)

Convert bytes to their base64 representation.

Parameters:d (bytes) – The data to convert to its base64 representation. Returns:The base64 representation of d. Return type:str

Example

>>> from pwny import *
>>> enb64(b'pwnypack')
'cHdueXBhY2s='

pwnypack.codec.deb64(d)

Convert a base64 representation back to its original bytes.

Parameters:d (str) – The base64 representation to decode. Returns:The bytes represented by d. Return type:bytes

Example

>>> from pwny import *
>>> deb64('cHdueXBhY2s=')
b'pwnypack'

pwnypack.codec.enurlform(q)

Convert a dictionary to a URL encoded query string.

Parameters:q (dict) – The query to encode. Returns:The urlencoded representation of q. Return type:str

Example

>>> from pwny import *
>>> enurlform({'foo': 'bar', 'baz': ['quux', 'corge']})
'foo=bar&baz=quux&baz=corge'

pwnypack.codec.deurlform(d)

Convert a URL encoded query string to a dictionary.

Parameters:d (str) – The URL encoded query string. Returns:A dictionary containing each key and all its values as a list. Return type:dict

Example

>>> from pwny import *
>>> deurlform('foo=bar&baz=quux&baz=corge')
{'foo': ['bar'], 'baz': ['quux', 'corge']}

pwnypack.codec.enurlquote(v, plus=False)

Percent encode a string for use in an URL.

Parameters:

• v (str) – The value to percent encode.
• plus (bool) – Use a plus symbol for spaces, otherwise use %20.

Returns:

The percent encoded string.

Return type:

str

Example

>>> from pwny import *
>>> enurlquote('Foo Bar/Baz', True)
'Foo+Bar/Baz

pwnypack.codec.deurlquote(d, plus=False)

Decode a percent encoded string.

Parameters:

• d (str) – The percent encoded value to decode.
• plus (bool) – Parse a plus symbol as a space.

Returns:

The decoded version of the percent encoded of d.

Return type:

str

Example

>>> from pwny import *
>>> deurlquote('Foo+Bar/Baz')
'Foo Bar/Baz'

pwnypack.codec.frequency(v)

Perform a frequency analysis on a byte sequence or string.

Parameters:d (bytes or str) – The sequence to analyse. Returns:A dictionary of unique elements in d and how often the occur. Return type:dict

Example

>>> frequency('pwnypack')
{'a': 1, 'c': 1, 'k': 1, 'n': 1, 'p': 2, 'w': 1, 'y': 1}