cpython/Lib/base64.py

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#! /usr/bin/env python3
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"""Base16, Base32, Base64 (RFC 3548), Base85 and Ascii85 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
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import re
import struct
import binascii
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__all__ = [
# Legacy interface exports traditional RFC 1521 Base64 encodings
'encode', 'decode', 'encodebytes', 'decodebytes',
# Generalized interface for other encodings
'b64encode', 'b64decode', 'b32encode', 'b32decode',
'b16encode', 'b16decode',
# Base85 and Ascii85 encodings
'b85encode', 'b85decode', 'a85encode', 'a85decode',
# 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',
]
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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')
if isinstance(s, bytes_types):
return s
try:
return memoryview(s).tobytes()
except TypeError:
raise TypeError("argument should be a bytes-like object or ASCII "
"string, not %r" % s.__class__.__name__) from None
# 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.
"""
encoded = binascii.b2a_base64(s, newline=False)
if altchars is not None:
assert len(altchars) == 2, repr(altchars)
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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)
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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)
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_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
'/'.
"""
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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 '/'.
"""
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s = _bytes_from_decode_data(s)
s = s.translate(_urlsafe_decode_translation)
return b64decode(s)
# Base32 encoding/decoding must be done in Python
_b32alphabet = b'ABCDEFGHIJKLMNOPQRSTUVWXYZ234567'
_b32tab2 = None
_b32rev = None
def b32encode(s):
"""Encode a byte string using Base32.
s is the byte string to encode. The encoded byte string is returned.
"""
global _b32tab2
# Delay the initialization of the table to not waste memory
# if the function is never called
if _b32tab2 is None:
b32tab = [bytes((i,)) for i in _b32alphabet]
_b32tab2 = [a + b for a in b32tab for b in b32tab]
b32tab = None
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if not isinstance(s, bytes_types):
s = memoryview(s).tobytes()
leftover = len(s) % 5
# Pad the last quantum with zero bits if necessary
if leftover:
s = s + bytes(5 - leftover) # Don't use += !
encoded = bytearray()
from_bytes = int.from_bytes
b32tab2 = _b32tab2
for i in range(0, len(s), 5):
c = from_bytes(s[i: i + 5], 'big')
encoded += (b32tab2[c >> 30] + # bits 1 - 10
b32tab2[(c >> 20) & 0x3ff] + # bits 11 - 20
b32tab2[(c >> 10) & 0x3ff] + # bits 21 - 30
b32tab2[c & 0x3ff] # bits 31 - 40
)
# Adjust for any leftover partial quanta
if leftover == 1:
encoded[-6:] = b'======'
elif leftover == 2:
encoded[-4:] = b'===='
elif leftover == 3:
encoded[-3:] = b'==='
elif leftover == 4:
encoded[-1:] = b'='
return bytes(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.
"""
global _b32rev
# Delay the initialization of the table to not waste memory
# if the function is never called
if _b32rev is None:
_b32rev = {v: k for k, v in enumerate(_b32alphabet)}
s = _bytes_from_decode_data(s)
if len(s) % 8:
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)
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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.
l = len(s)
s = s.rstrip(b'=')
padchars = l - len(s)
# Now decode the full quanta
decoded = bytearray()
b32rev = _b32rev
for i in range(0, len(s), 8):
quanta = s[i: i + 8]
acc = 0
try:
for c in quanta:
acc = (acc << 5) + b32rev[c]
except KeyError:
raise binascii.Error('Non-base32 digit found') from None
decoded += acc.to_bytes(5, 'big')
# Process the last, partial quanta
if padchars:
acc <<= 5 * padchars
last = acc.to_bytes(5, 'big')
if padchars == 1:
decoded[-5:] = last[:-1]
elif padchars == 3:
decoded[-5:] = last[:-2]
elif padchars == 4:
decoded[-5:] = last[:-3]
elif padchars == 6:
decoded[-5:] = last[:-4]
else:
raise binascii.Error('Incorrect padding')
return bytes(decoded)
# 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.
"""
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)
#
# Ascii85 encoding/decoding
#
_a85chars = None
_a85chars2 = None
_A85START = b"<~"
_A85END = b"~>"
def _85encode(b, chars, chars2, pad=False, foldnuls=False, foldspaces=False):
# Helper function for a85encode and b85encode
if not isinstance(b, bytes_types):
b = memoryview(b).tobytes()
padding = (-len(b)) % 4
if padding:
b = b + b'\0' * padding
words = struct.Struct('!%dI' % (len(b) // 4)).unpack(b)
chunks = [b'z' if foldnuls and not word else
b'y' if foldspaces and word == 0x20202020 else
(chars2[word // 614125] +
chars2[word // 85 % 7225] +
chars[word % 85])
for word in words]
if padding and not pad:
if chunks[-1] == b'z':
chunks[-1] = chars[0] * 5
chunks[-1] = chunks[-1][:-padding]
return b''.join(chunks)
def a85encode(b, *, foldspaces=False, wrapcol=0, pad=False, adobe=False):
"""Encode a byte string using Ascii85.
b is the byte string to encode. The encoded byte string is returned.
foldspaces is an optional flag that uses the special short sequence 'y'
instead of 4 consecutive spaces (ASCII 0x20) as supported by 'btoa'. This
feature is not supported by the "standard" Adobe encoding.
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wrapcol controls whether the output should have newline ('\\n') characters
added to it. If this is non-zero, each output line will be at most this
many characters long.
pad controls whether the input string is padded to a multiple of 4 before
encoding. Note that the btoa implementation always pads.
adobe controls whether the encoded byte sequence is framed with <~ and ~>,
which is used by the Adobe implementation.
"""
global _a85chars, _a85chars2
# Delay the initialization of tables to not waste memory
# if the function is never called
if _a85chars is None:
_a85chars = [bytes((i,)) for i in range(33, 118)]
_a85chars2 = [(a + b) for a in _a85chars for b in _a85chars]
result = _85encode(b, _a85chars, _a85chars2, pad, True, foldspaces)
if adobe:
result = _A85START + result
if wrapcol:
wrapcol = max(2 if adobe else 1, wrapcol)
chunks = [result[i: i + wrapcol]
for i in range(0, len(result), wrapcol)]
if adobe:
if len(chunks[-1]) + 2 > wrapcol:
chunks.append(b'')
result = b'\n'.join(chunks)
if adobe:
result += _A85END
return result
def a85decode(b, *, foldspaces=False, adobe=False, ignorechars=b' \t\n\r\v'):
"""Decode an Ascii85 encoded byte string.
s is the byte string to decode.
foldspaces is a flag that specifies whether the 'y' short sequence should be
accepted as shorthand for 4 consecutive spaces (ASCII 0x20). This feature is
not supported by the "standard" Adobe encoding.
adobe controls whether the input sequence is in Adobe Ascii85 format (i.e.
is framed with <~ and ~>).
ignorechars should be a byte string containing characters to ignore from the
input. This should only contain whitespace characters, and by default
contains all whitespace characters in ASCII.
"""
b = _bytes_from_decode_data(b)
if adobe:
if not (b.startswith(_A85START) and b.endswith(_A85END)):
raise ValueError("Ascii85 encoded byte sequences must be bracketed "
"by {!r} and {!r}".format(_A85START, _A85END))
b = b[2:-2] # Strip off start/end markers
#
# We have to go through this stepwise, so as to ignore spaces and handle
# special short sequences
#
packI = struct.Struct('!I').pack
decoded = []
decoded_append = decoded.append
curr = []
curr_append = curr.append
curr_clear = curr.clear
for x in b + b'u' * 4:
if b'!'[0] <= x <= b'u'[0]:
curr_append(x)
if len(curr) == 5:
acc = 0
for x in curr:
acc = 85 * acc + (x - 33)
try:
decoded_append(packI(acc))
except struct.error:
raise ValueError('Ascii85 overflow') from None
curr_clear()
elif x == b'z'[0]:
if curr:
raise ValueError('z inside Ascii85 5-tuple')
decoded_append(b'\0\0\0\0')
elif foldspaces and x == b'y'[0]:
if curr:
raise ValueError('y inside Ascii85 5-tuple')
decoded_append(b'\x20\x20\x20\x20')
elif x in ignorechars:
# Skip whitespace
continue
else:
raise ValueError('Non-Ascii85 digit found: %c' % x)
result = b''.join(decoded)
padding = 4 - len(curr)
if padding:
# Throw away the extra padding
result = result[:-padding]
return result
# The following code is originally taken (with permission) from Mercurial
_b85alphabet = (b"0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ"
b"abcdefghijklmnopqrstuvwxyz!#$%&()*+-;<=>?@^_`{|}~")
_b85chars = None
_b85chars2 = None
_b85dec = None
def b85encode(b, pad=False):
"""Encode an ASCII-encoded byte array in base85 format.
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If pad is true, the input is padded with "\\0" so its length is a multiple of
4 characters before encoding.
"""
global _b85chars, _b85chars2
# Delay the initialization of tables to not waste memory
# if the function is never called
if _b85chars is None:
_b85chars = [bytes((i,)) for i in _b85alphabet]
_b85chars2 = [(a + b) for a in _b85chars for b in _b85chars]
return _85encode(b, _b85chars, _b85chars2, pad)
def b85decode(b):
"""Decode base85-encoded byte array"""
global _b85dec
# Delay the initialization of tables to not waste memory
# if the function is never called
if _b85dec is None:
_b85dec = [None] * 256
for i, c in enumerate(_b85alphabet):
_b85dec[c] = i
b = _bytes_from_decode_data(b)
padding = (-len(b)) % 5
b = b + b'~' * padding
out = []
packI = struct.Struct('!I').pack
for i in range(0, len(b), 5):
chunk = b[i:i + 5]
acc = 0
try:
for c in chunk:
acc = acc * 85 + _b85dec[c]
except TypeError:
for j, c in enumerate(chunk):
if _b85dec[c] is None:
raise ValueError('bad base85 character at position %d'
% (i + j)) from None
raise
try:
out.append(packI(acc))
except struct.error:
raise ValueError('base85 overflow in hunk starting at byte %d'
% i) from None
result = b''.join(out)
if padding:
result = result[:-padding]
return result
# 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
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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)
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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)
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def _input_type_check(s):
try:
m = memoryview(s)
except TypeError as err:
msg = "expected bytes-like object, not %s" % s.__class__.__name__
raise TypeError(msg) from err
if m.format not in ('c', 'b', 'B'):
msg = ("expected single byte elements, not %r from %s" %
(m.format, s.__class__.__name__))
raise TypeError(msg)
if m.ndim != 1:
msg = ("expected 1-D data, not %d-D data from %s" %
(m.ndim, s.__class__.__name__))
raise TypeError(msg)
def encodebytes(s):
"""Encode a bytestring into a bytestring containing multiple lines
of base-64 data."""
_input_type_check(s)
pieces = []
for i in range(0, len(s), MAXBINSIZE):
chunk = s[i : i + MAXBINSIZE]
pieces.append(binascii.b2a_base64(chunk))
return b"".join(pieces)
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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."""
_input_type_check(s)
return binascii.a2b_base64(s)
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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)
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def test():
s0 = b"Aladdin:open sesame"
print(repr(s0))
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s1 = encodebytes(s0)
print(repr(s1))
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s2 = decodebytes(s1)
print(repr(s2))
assert s0 == s2
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if __name__ == '__main__':
main()