#! /usr/bin/env python
"""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 _translate(s, altchars):
if not isinstance(s, bytes_types):
raise TypeError("expected bytes, not %s" % s.__class__.__name__)
translation = bytearray(range(256))
for k, v in altchars.items():
translation[ord(k)] = v[0]
return s.translate(translation)
# 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 _translate(encoded, {'+': altchars[0:1], '/': altchars[1:2]})
return encoded
def b64decode(s, altchars=None):
"""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 byte string is returned. binascii.Error is raised if
s were incorrectly padded or if there are non-alphabet characters
present in the string.
"""
if not isinstance(s, bytes_types):
raise TypeError("expected bytes, not %s" % s.__class__.__name__)
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)
s = _translate(s, {chr(altchars[0]): b'+', chr(altchars[1]): b'/'})
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)
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, b'-_')
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 '/'.
"""
return b64decode(s, b'-_')
# 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.
"""
if not isinstance(s, bytes_types):
raise TypeError("expected bytes, not %s" % s.__class__.__name__)
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:
if not isinstance(map01, bytes_types):
raise TypeError("expected bytes, not %s" % map01.__class__.__name__)
assert len(map01) == 1, repr(map01)
s = _translate(s, {b'0': b'O', b'1': 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('%010x' % acc))
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.
"""
if not isinstance(s, bytes_types):
raise TypeError("expected bytes, not %s" % s.__class__.__name__)
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] != '-':
func(open(args[0], 'rb'), sys.stdout)
else:
func(sys.stdin, sys.stdout)
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()
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