#! /usr/bin/env python3

"""RFC 3548: Base16, Base32, Base64 Data Encodings"""

# Modified 04-Oct-1995 by Jack Jansen to use binascii module

# Modified 30-Dec-2003 by Barry Warsaw to add full RFC 3548 support

# Modified 22-May-2007 by Guido van Rossum to use bytes everywhere

import re

import struct

import binascii

__all__ = [

# Legacy interface exports traditional RFC 1521 Base64 encodings

'encode', 'decode', 'encodebytes', 'decodebytes',

# Generalized interface for other encodings

'b64encode', 'b64decode', 'b32encode', 'b32decode',

'b16encode', 'b16decode',

# Standard Base64 encoding

'standard_b64encode', 'standard_b64decode',

# Some common Base64 alternatives. As referenced by RFC 3458, see thread

# starting at:

#

# http://zgp.org/pipermail/p2p-hackers/2001-September/000316.html

'urlsafe_b64encode', 'urlsafe_b64decode',

]

bytes_types = (bytes, bytearray) # Types acceptable as binary data

def _bytes_from_decode_data(s):

if isinstance(s, str):

try:

return s.encode('ascii')

except UnicodeEncodeError:

raise ValueError('string argument should contain only ASCII characters')

elif isinstance(s, bytes_types):

return s

else:

raise TypeError("argument should be bytes or ASCII string, not %s" % s.__class__.__name__)

# Base64 encoding/decoding uses binascii

def b64encode(s, altchars=None):

"""Encode a byte string using Base64.

s is the byte string to encode. Optional altchars must be a byte

string of length 2 which specifies an alternative alphabet for the

'+' and '/' characters. This allows an application to

e.g. generate url or filesystem safe Base64 strings.

The encoded byte string is returned.

"""

if not isinstance(s, bytes_types):

raise TypeError("expected bytes, not %s" % s.__class__.__name__)

# Strip off the trailing newline

encoded = binascii.b2a_base64(s)[:-1]

if altchars is not None:

if not isinstance(altchars, bytes_types):

raise TypeError("expected bytes, not %s"

% altchars.__class__.__name__)

assert len(altchars) == 2, repr(altchars)

return encoded.translate(bytes.maketrans(b'+/', altchars))

return encoded

def b64decode(s, altchars=None, validate=False):

"""Decode a Base64 encoded byte string.

s is the byte string to decode. Optional altchars must be a

string of length 2 which specifies the alternative alphabet used

instead of the '+' and '/' characters.

The decoded string is returned. A binascii.Error is raised if s is

incorrectly padded.

If validate is False (the default), non-base64-alphabet characters are

discarded prior to the padding check. If validate is True,

non-base64-alphabet characters in the input result in a binascii.Error.

"""

s = _bytes_from_decode_data(s)

if altchars is not None:

altchars = _bytes_from_decode_data(altchars)

assert len(altchars) == 2, repr(altchars)

s = s.translate(bytes.maketrans(altchars, b'+/'))

if validate and not re.match(b'^[A-Za-z0-9+/]*={0,2}$', s):

raise binascii.Error('Non-base64 digit found')

return binascii.a2b_base64(s)

def standard_b64encode(s):

"""Encode a byte string using the standard Base64 alphabet.

s is the byte string to encode. The encoded byte string is returned.

"""

return b64encode(s)

def standard_b64decode(s):

"""Decode a byte string encoded with the standard Base64 alphabet.

s is the byte string to decode. The decoded byte string is

returned. binascii.Error is raised if the input is incorrectly

padded or if there are non-alphabet characters present in the

input.

"""

return b64decode(s)

_urlsafe_encode_translation = bytes.maketrans(b'+/', b'-_')

_urlsafe_decode_translation = bytes.maketrans(b'-_', b'+/')

def urlsafe_b64encode(s):

"""Encode a byte string using a url-safe Base64 alphabet.

s is the byte string to encode. The encoded byte string is

returned. The alphabet uses '-' instead of '+' and '_' instead of

'/'.

"""

return b64encode(s).translate(_urlsafe_encode_translation)

def urlsafe_b64decode(s):

"""Decode a byte string encoded with the standard Base64 alphabet.

s is the byte string to decode. The decoded byte string is

returned. binascii.Error is raised if the input is incorrectly

padded or if there are non-alphabet characters present in the

input.

The alphabet uses '-' instead of '+' and '_' instead of '/'.

"""

s = _bytes_from_decode_data(s)

s = s.translate(_urlsafe_decode_translation)

return b64decode(s)

# Base32 encoding/decoding must be done in Python

_b32alphabet = {

0: b'A', 9: b'J', 18: b'S', 27: b'3',

1: b'B', 10: b'K', 19: b'T', 28: b'4',

2: b'C', 11: b'L', 20: b'U', 29: b'5',

3: b'D', 12: b'M', 21: b'V', 30: b'6',

4: b'E', 13: b'N', 22: b'W', 31: b'7',

5: b'F', 14: b'O', 23: b'X',

6: b'G', 15: b'P', 24: b'Y',

7: b'H', 16: b'Q', 25: b'Z',

8: b'I', 17: b'R', 26: b'2',

}

_b32tab = [v[0] for k, v in sorted(_b32alphabet.items())]

_b32rev = dict([(v[0], k) for k, v in _b32alphabet.items()])

def b32encode(s):

"""Encode a byte string using Base32.

s is the byte string to encode. The encoded byte string is returned.

"""

if not isinstance(s, bytes_types):

raise TypeError("expected bytes, not %s" % s.__class__.__name__)

quanta, leftover = divmod(len(s), 5)

# Pad the last quantum with zero bits if necessary

if leftover:

s = s + bytes(5 - leftover) # Don't use += !

quanta += 1

encoded = bytes()

for i in range(quanta):

# c1 and c2 are 16 bits wide, c3 is 8 bits wide. The intent of this

# code is to process the 40 bits in units of 5 bits. So we take the 1

# leftover bit of c1 and tack it onto c2. Then we take the 2 leftover

# bits of c2 and tack them onto c3. The shifts and masks are intended

# to give us values of exactly 5 bits in width.

c1, c2, c3 = struct.unpack('!HHB', s[i*5:(i+1)*5])

c2 += (c1 & 1) << 16 # 17 bits wide

c3 += (c2 & 3) << 8 # 10 bits wide

encoded += bytes([_b32tab[c1 >> 11], # bits 1 - 5

_b32tab[(c1 >> 6) & 0x1f], # bits 6 - 10

_b32tab[(c1 >> 1) & 0x1f], # bits 11 - 15

_b32tab[c2 >> 12], # bits 16 - 20 (1 - 5)

_b32tab[(c2 >> 7) & 0x1f], # bits 21 - 25 (6 - 10)

_b32tab[(c2 >> 2) & 0x1f], # bits 26 - 30 (11 - 15)

_b32tab[c3 >> 5], # bits 31 - 35 (1 - 5)

_b32tab[c3 & 0x1f], # bits 36 - 40 (1 - 5)

])

# Adjust for any leftover partial quanta

if leftover == 1:

return encoded[:-6] + b'======'

elif leftover == 2:

return encoded[:-4] + b'===='

elif leftover == 3:

return encoded[:-3] + b'==='

elif leftover == 4:

return encoded[:-1] + b'='

return encoded

def b32decode(s, casefold=False, map01=None):

"""Decode a Base32 encoded byte string.

s is the byte string to decode. Optional casefold is a flag

specifying whether a lowercase alphabet is acceptable as input.

For security purposes, the default is False.

RFC 3548 allows for optional mapping of the digit 0 (zero) to the

letter O (oh), and for optional mapping of the digit 1 (one) to

either the letter I (eye) or letter L (el). The optional argument

map01 when not None, specifies which letter the digit 1 should be

mapped to (when map01 is not None, the digit 0 is always mapped to

the letter O). For security purposes the default is None, so that

0 and 1 are not allowed in the input.

The decoded byte string is returned. binascii.Error is raised if

the input is incorrectly padded or if there are non-alphabet

characters present in the input.

"""

s = _bytes_from_decode_data(s)

quanta, leftover = divmod(len(s), 8)

if leftover:

raise binascii.Error('Incorrect padding')

# Handle section 2.4 zero and one mapping. The flag map01 will be either

# False, or the character to map the digit 1 (one) to. It should be

# either L (el) or I (eye).

if map01 is not None:

map01 = _bytes_from_decode_data(map01)

assert len(map01) == 1, repr(map01)

s = s.translate(bytes.maketrans(b'01', b'O' + map01))

if casefold:

s = s.upper()

# Strip off pad characters from the right. We need to count the pad

# characters because this will tell us how many null bytes to remove from

# the end of the decoded string.

padchars = 0

mo = re.search(b'(?P<pad>[=]*)$', s)

if mo:

padchars = len(mo.group('pad'))

if padchars > 0:

s = s[:-padchars]

# Now decode the full quanta

parts = []

acc = 0

shift = 35

for c in s:

val = _b32rev.get(c)

if val is None:

raise TypeError('Non-base32 digit found')

acc += _b32rev[c] << shift

shift -= 5

if shift < 0:

parts.append(binascii.unhexlify(bytes('%010x' % acc, "ascii")))

acc = 0

shift = 35

# Process the last, partial quanta

last = binascii.unhexlify(bytes('%010x' % acc, "ascii"))

if padchars == 0:

last = b'' # No characters

elif padchars == 1:

last = last[:-1]

elif padchars == 3:

last = last[:-2]

elif padchars == 4:

last = last[:-3]

elif padchars == 6:

last = last[:-4]

else:

raise binascii.Error('Incorrect padding')

parts.append(last)

return b''.join(parts)

# RFC 3548, Base 16 Alphabet specifies uppercase, but hexlify() returns

# lowercase. The RFC also recommends against accepting input case

# insensitively.

def b16encode(s):

"""Encode a byte string using Base16.

s is the byte string to encode. The encoded byte string is returned.

"""

if not isinstance(s, bytes_types):

raise TypeError("expected bytes, not %s" % s.__class__.__name__)

return binascii.hexlify(s).upper()

def b16decode(s, casefold=False):

"""Decode a Base16 encoded byte string.

s is the byte string to decode. Optional casefold is a flag

specifying whether a lowercase alphabet is acceptable as input.

For security purposes, the default is False.

The decoded byte string is returned. binascii.Error is raised if

s were incorrectly padded or if there are non-alphabet characters

present in the string.

"""

s = _bytes_from_decode_data(s)

if casefold:

s = s.upper()

if re.search(b'[^0-9A-F]', s):

raise binascii.Error('Non-base16 digit found')

return binascii.unhexlify(s)

# Legacy interface. This code could be cleaned up since I don't believe

# binascii has any line length limitations. It just doesn't seem worth it

# though. The files should be opened in binary mode.

MAXLINESIZE = 76 # Excluding the CRLF

MAXBINSIZE = (MAXLINESIZE//4)*3

def encode(input, output):

"""Encode a file; input and output are binary files."""

while True:

s = input.read(MAXBINSIZE)

if not s:

break

while len(s) < MAXBINSIZE:

ns = input.read(MAXBINSIZE-len(s))

if not ns:

break

s += ns

line = binascii.b2a_base64(s)

output.write(line)

def decode(input, output):

"""Decode a file; input and output are binary files."""

while True:

line = input.readline()

if not line:

break

s = binascii.a2b_base64(line)

output.write(s)

def encodebytes(s):

"""Encode a bytestring into a bytestring containing multiple lines

of base-64 data."""

if not isinstance(s, bytes_types):

raise TypeError("expected bytes, not %s" % s.__class__.__name__)

pieces = []

for i in range(0, len(s), MAXBINSIZE):

chunk = s[i : i + MAXBINSIZE]

pieces.append(binascii.b2a_base64(chunk))

return b"".join(pieces)

def encodestring(s):

"""Legacy alias of encodebytes()."""

import warnings

warnings.warn("encodestring() is a deprecated alias, use encodebytes()",

DeprecationWarning, 2)

return encodebytes(s)

def decodebytes(s):

"""Decode a bytestring of base-64 data into a bytestring."""

if not isinstance(s, bytes_types):

raise TypeError("expected bytes, not %s" % s.__class__.__name__)

return binascii.a2b_base64(s)

def decodestring(s):

"""Legacy alias of decodebytes()."""

import warnings

warnings.warn("decodestring() is a deprecated alias, use decodebytes()",

DeprecationWarning, 2)

return decodebytes(s)

# Usable as a script...

def main():

"""Small main program"""

import sys, getopt

try:

opts, args = getopt.getopt(sys.argv[1:], 'deut')

except getopt.error as msg:

sys.stdout = sys.stderr

print(msg)

print("""usage: %s [-d|-e|-u|-t] [file|-]

-d, -u: decode

-e: encode (default)

-t: encode and decode string 'Aladdin:open sesame'"""%sys.argv[0])

sys.exit(2)

func = encode

for o, a in opts:

if o == '-e': func = encode

if o == '-d': func = decode

if o == '-u': func = decode

if o == '-t': test(); return

if args and args[0] != '-':

with open(args[0], 'rb') as f:

func(f, sys.stdout.buffer)

else:

func(sys.stdin.buffer, sys.stdout.buffer)

def test():

s0 = b"Aladdin:open sesame"

print(repr(s0))

s1 = encodebytes(s0)

print(repr(s1))

s2 = decodebytes(s1)

print(repr(s2))

assert s0 == s2

if __name__ == '__main__':

main()