cpython/Lib/base64.py

619 lines
22 KiB
Python

"""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
import struct
import binascii
__all__ = [
# Legacy interface exports traditional RFC 2045 Base64 encodings
'encode', 'decode', 'encodebytes', 'decodebytes',
# Generalized interface for other encodings
'b64encode', 'b64decode', 'b32encode', 'b32decode',
'b32hexencode', 'b32hexdecode', 'b16encode', 'b16decode',
# Base85 and Ascii85 encodings
'b85encode', 'b85decode', 'a85encode', 'a85decode', 'z85encode', 'z85decode',
# 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')
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, *, wrapcol=0):
"""Encode the bytes-like object s using Base64 and return a bytes object.
Optional altchars should 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.
If wrapcol is non-zero, insert a newline (b'\\n') character after at most
every wrapcol characters.
"""
encoded = binascii.b2a_base64(s, wrapcol=wrapcol, newline=False)
if altchars is not None:
assert len(altchars) == 2, repr(altchars)
return encoded.translate(bytes.maketrans(b'+/', altchars))
return encoded
def b64decode(s, altchars=None, validate=False):
"""Decode the Base64 encoded bytes-like object or ASCII string s.
Optional altchars must be a bytes-like object or ASCII string of length 2
which specifies the alternative alphabet used instead of the '+' and '/'
characters.
The result is returned as a bytes object. A binascii.Error is raised if
s is incorrectly padded.
If validate is False (the default), characters that are neither in the
normal base-64 alphabet nor the alternative alphabet are discarded prior
to the padding check. If validate is True, these non-alphabet characters
in the input result in a binascii.Error.
For more information about the strict base64 check, see:
https://docs.python.org/3.11/library/binascii.html#binascii.a2b_base64
"""
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'+/'))
return binascii.a2b_base64(s, strict_mode=validate)
def standard_b64encode(s):
"""Encode bytes-like object s using the standard Base64 alphabet.
The result is returned as a bytes object.
"""
return b64encode(s)
def standard_b64decode(s):
"""Decode bytes encoded with the standard Base64 alphabet.
Argument s is a bytes-like object or ASCII string to decode. The result
is returned as a bytes object. A binascii.Error is raised if the input
is incorrectly padded. Characters that are not in the standard alphabet
are discarded prior to the padding check.
"""
return b64decode(s)
_urlsafe_encode_translation = bytes.maketrans(b'+/', b'-_')
_urlsafe_decode_translation = bytes.maketrans(b'-_', b'+/')
def urlsafe_b64encode(s):
"""Encode bytes using the URL- and filesystem-safe Base64 alphabet.
Argument s is a bytes-like object to encode. The result is returned as a
bytes object. The alphabet uses '-' instead of '+' and '_' instead of
'/'.
"""
return b64encode(s).translate(_urlsafe_encode_translation)
def urlsafe_b64decode(s):
"""Decode bytes using the URL- and filesystem-safe Base64 alphabet.
Argument s is a bytes-like object or ASCII string to decode. The result
is returned as a bytes object. A binascii.Error is raised if the input
is incorrectly padded. Characters that are not in the URL-safe base-64
alphabet, and are not a plus '+' or slash '/', are discarded prior to the
padding check.
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
_B32_ENCODE_DOCSTRING = '''
Encode the bytes-like objects using {encoding} and return a bytes object.
'''
_B32_DECODE_DOCSTRING = '''
Decode the {encoding} encoded bytes-like object or ASCII string s.
Optional casefold is a flag specifying whether a lowercase alphabet is
acceptable as input. For security purposes, the default is False.
{extra_args}
The result is returned as a bytes object. A binascii.Error is raised if
the input is incorrectly padded or if there are non-alphabet
characters present in the input.
'''
_B32_DECODE_MAP01_DOCSTRING = '''
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.
'''
_b32alphabet = b'ABCDEFGHIJKLMNOPQRSTUVWXYZ234567'
_b32hexalphabet = b'0123456789ABCDEFGHIJKLMNOPQRSTUV'
_b32tab2 = {}
_b32rev = {}
def _b32encode(alphabet, s):
# Delay the initialization of the table to not waste memory
# if the function is never called
if alphabet not in _b32tab2:
b32tab = [bytes((i,)) for i in alphabet]
_b32tab2[alphabet] = [a + b for a in b32tab for b in b32tab]
b32tab = None
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 + b'\0' * (5 - leftover) # Don't use += !
encoded = bytearray()
from_bytes = int.from_bytes
b32tab2 = _b32tab2[alphabet]
for i in range(0, len(s), 5):
c = from_bytes(s[i: i + 5]) # big endian
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 encoded.take_bytes()
def _b32decode(alphabet, s, casefold=False, map01=None):
# Delay the initialization of the table to not waste memory
# if the function is never called
if alphabet not in _b32rev:
_b32rev[alphabet] = {v: k for k, v in enumerate(alphabet)}
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)
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[alphabet]
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 endian
# Process the last, partial quanta
if l % 8 or padchars not in {0, 1, 3, 4, 6}:
raise binascii.Error('Incorrect padding')
if padchars and decoded:
acc <<= 5 * padchars
last = acc.to_bytes(5) # big endian
leftover = (43 - 5 * padchars) // 8 # 1: 4, 3: 3, 4: 2, 6: 1
decoded[-5:] = last[:leftover]
return decoded.take_bytes()
def b32encode(s):
return _b32encode(_b32alphabet, s)
b32encode.__doc__ = _B32_ENCODE_DOCSTRING.format(encoding='base32')
def b32decode(s, casefold=False, map01=None):
return _b32decode(_b32alphabet, s, casefold, map01)
b32decode.__doc__ = _B32_DECODE_DOCSTRING.format(encoding='base32',
extra_args=_B32_DECODE_MAP01_DOCSTRING)
def b32hexencode(s):
return _b32encode(_b32hexalphabet, s)
b32hexencode.__doc__ = _B32_ENCODE_DOCSTRING.format(encoding='base32hex')
def b32hexdecode(s, casefold=False):
# base32hex does not have the 01 mapping
return _b32decode(_b32hexalphabet, s, casefold)
b32hexdecode.__doc__ = _B32_DECODE_DOCSTRING.format(encoding='base32hex',
extra_args='')
# RFC 3548, Base 16 Alphabet specifies uppercase, but hexlify() returns
# lowercase. The RFC also recommends against accepting input case
# insensitively.
def b16encode(s):
"""Encode the bytes-like object s using Base16 and return a bytes object.
"""
return binascii.hexlify(s).upper()
def b16decode(s, casefold=False):
"""Decode the Base16 encoded bytes-like object or ASCII string s.
Optional casefold is a flag specifying whether a lowercase alphabet is
acceptable as input. For security purposes, the default is False.
The result is returned as a bytes object. A binascii.Error is raised if
s is incorrectly padded or if there are non-alphabet characters present
in the input.
"""
s = _bytes_from_decode_data(s)
if casefold:
s = s.upper()
if s.translate(None, delete=b'0123456789ABCDEF'):
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 bytes-like object b using Ascii85 and return a bytes object.
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.
If wrapcol is non-zero, insert a newline (b'\\n') character after at most
every wrapcol characters.
pad controls whether the input 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 _a85chars2 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 the Ascii85 encoded bytes-like object or ASCII string b.
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.
The result is returned as a bytes object.
"""
b = _bytes_from_decode_data(b)
if adobe:
if not b.endswith(_A85END):
raise ValueError(
"Ascii85 encoded byte sequences must end "
"with {!r}".format(_A85END)
)
if b.startswith(_A85START):
b = b[2:-2] # Strip off start/end markers
else:
b = b[:-2]
#
# 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!#$%&()*+-;<=>?@^_`{|}~")
_b85chars = None
_b85chars2 = None
_b85dec = None
def b85encode(b, pad=False):
"""Encode bytes-like object b in base85 format and return a bytes object.
If pad is true, the input is padded with b'\\0' so its length is a multiple of
4 bytes before encoding.
"""
global _b85chars, _b85chars2
# Delay the initialization of tables to not waste memory
# if the function is never called
if _b85chars2 is None:
_b85chars = [bytes((i,)) for i in _b85alphabet]
_b85chars2 = [(a + b) for a in _b85chars for b in _b85chars]
return _85encode(b, _b85chars, _b85chars2, pad)
def b85decode(b):
"""Decode the base85-encoded bytes-like object or ASCII string b
The result is returned as a bytes object.
"""
global _b85dec
# Delay the initialization of tables to not waste memory
# if the function is never called
if _b85dec is None:
# we don't assign to _b85dec directly to avoid issues when
# multiple threads call this function simultaneously
b85dec_tmp = [None] * 256
for i, c in enumerate(_b85alphabet):
b85dec_tmp[c] = i
_b85dec = b85dec_tmp
b = _bytes_from_decode_data(b)
padding = (-len(b)) % 5
b = b + b'~' * padding
out = []
packI = struct.Struct('!I').pack
for i in range(0, len(b), 5):
chunk = b[i:i + 5]
acc = 0
try:
for c in chunk:
acc = acc * 85 + _b85dec[c]
except TypeError:
for j, c in enumerate(chunk):
if _b85dec[c] is None:
raise ValueError('bad base85 character at position %d'
% (i + j)) from None
raise
try:
out.append(packI(acc))
except struct.error:
raise ValueError('base85 overflow in hunk starting at byte %d'
% i) from None
result = b''.join(out)
if padding:
result = result[:-padding]
return result
_z85alphabet = (b'0123456789abcdefghijklmnopqrstuvwxyz'
b'ABCDEFGHIJKLMNOPQRSTUVWXYZ.-:+=^!/*?&<>()[]{}@%$#')
# Translating b85 valid but z85 invalid chars to b'\x00' is required
# to prevent them from being decoded as b85 valid chars.
_z85_b85_decode_diff = b';_`|~'
_z85_decode_translation = bytes.maketrans(
_z85alphabet + _z85_b85_decode_diff,
_b85alphabet + b'\x00' * len(_z85_b85_decode_diff)
)
_z85_encode_translation = bytes.maketrans(_b85alphabet, _z85alphabet)
def z85encode(s, pad=False):
"""Encode bytes-like object b in z85 format and return a bytes object."""
return b85encode(s, pad).translate(_z85_encode_translation)
def z85decode(s):
"""Decode the z85-encoded bytes-like object or ASCII string b
The result is returned as a bytes object.
"""
s = _bytes_from_decode_data(s)
s = s.translate(_z85_decode_translation)
try:
return b85decode(s)
except ValueError as e:
raise ValueError(e.args[0].replace('base85', 'z85')) from None
# 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 s := input.read(MAXBINSIZE):
while len(s) < MAXBINSIZE and (ns := input.read(MAXBINSIZE-len(s))):
s += ns
line = binascii.b2a_base64(s)
output.write(line)
def decode(input, output):
"""Decode a file; input and output are binary files."""
while line := input.readline():
s = binascii.a2b_base64(line)
output.write(s)
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 bytes object containing multiple lines
of base-64 data."""
_input_type_check(s)
result = binascii.b2a_base64(s, wrapcol=MAXLINESIZE)
if result == b'\n':
return b''
return result
def decodebytes(s):
"""Decode a bytestring of base-64 data into a bytes object."""
_input_type_check(s)
return binascii.a2b_base64(s)
# Usable as a script...
def main():
"""Small main program"""
import sys, getopt
usage = f"""usage: {sys.argv[0]} [-h|-d|-e|-u] [file|-]
-h: print this help message and exit
-d, -u: decode
-e: encode (default)"""
try:
opts, args = getopt.getopt(sys.argv[1:], 'hdeu')
except getopt.error as msg:
sys.stdout = sys.stderr
print(msg)
print(usage)
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 == '-h': print(usage); return
if args and args[0] != '-':
with open(args[0], 'rb') as f:
func(f, sys.stdout.buffer)
else:
if sys.stdin.isatty():
# gh-138775: read terminal input data all at once to detect EOF
import io
data = sys.stdin.buffer.read()
buffer = io.BytesIO(data)
else:
buffer = sys.stdin.buffer
func(buffer, sys.stdout.buffer)
if __name__ == '__main__':
main()