kopia lustrzana https://github.com/micropython/micropython-lib
481 wiersze
14 KiB
Python
481 wiersze
14 KiB
Python
#! /usr/bin/env python3
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"""RFC 3548: Base16, Base32, Base64 Data Encodings"""
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# Modified 04-Oct-1995 by Jack Jansen to use binascii module
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# Modified 30-Dec-2003 by Barry Warsaw to add full RFC 3548 support
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# Modified 22-May-2007 by Guido van Rossum to use bytes everywhere
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import re
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import struct
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import binascii
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__all__ = [
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# Legacy interface exports traditional RFC 1521 Base64 encodings
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"encode",
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"decode",
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"encodebytes",
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"decodebytes",
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# Generalized interface for other encodings
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"b64encode",
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"b64decode",
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"b32encode",
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"b32decode",
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"b16encode",
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"b16decode",
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# Standard Base64 encoding
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"standard_b64encode",
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"standard_b64decode",
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# Some common Base64 alternatives. As referenced by RFC 3458, see thread
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# starting at:
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#
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# http://zgp.org/pipermail/p2p-hackers/2001-September/000316.html
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"urlsafe_b64encode",
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"urlsafe_b64decode",
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]
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bytes_types = (bytes, bytearray) # Types acceptable as binary data
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def _bytes_from_decode_data(s):
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if isinstance(s, str):
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try:
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return s.encode("ascii")
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# except UnicodeEncodeError:
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except:
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raise ValueError("string argument should contain only ASCII characters")
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elif isinstance(s, bytes_types):
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return s
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else:
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raise TypeError("argument should be bytes or ASCII string, not %s" % s.__class__.__name__)
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def _maketrans(f, t):
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"""Re-implement bytes.maketrans() as there is no such function in micropython"""
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if len(f) != len(t):
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raise ValueError("maketrans arguments must have same length")
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translation_table = dict(zip(f, t))
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return translation_table
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def _translate(input_bytes, trans_table):
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"""Re-implement bytes.translate() as there is no such function in micropython"""
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result = bytearray()
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for byte in input_bytes:
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translated_byte = trans_table.get(byte, byte)
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result.append(translated_byte)
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return bytes(result)
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# Base64 encoding/decoding uses binascii
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def b64encode(s, altchars=None):
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"""Encode a byte string using Base64.
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s is the byte string to encode. Optional altchars must be a byte
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string of length 2 which specifies an alternative alphabet for the
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'+' and '/' characters. This allows an application to
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e.g. generate url or filesystem safe Base64 strings.
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The encoded byte string is returned.
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"""
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if not isinstance(s, bytes_types):
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raise TypeError("expected bytes, not %s" % s.__class__.__name__)
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# Strip off the trailing newline
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encoded = binascii.b2a_base64(s)[:-1]
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if altchars is not None:
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if not isinstance(altchars, bytes_types):
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raise TypeError("expected bytes, not %s" % altchars.__class__.__name__)
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assert len(altchars) == 2, repr(altchars)
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encoded = _translate(encoded, _maketrans(b"+/", altchars))
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return encoded
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def b64decode(s, altchars=None, validate=False):
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"""Decode a Base64 encoded byte string.
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s is the byte string to decode. Optional altchars must be a
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string of length 2 which specifies the alternative alphabet used
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instead of the '+' and '/' characters.
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The decoded string is returned. A binascii.Error is raised if s is
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incorrectly padded.
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If validate is False (the default), non-base64-alphabet characters are
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discarded prior to the padding check. If validate is True,
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non-base64-alphabet characters in the input result in a binascii.Error.
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"""
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s = _bytes_from_decode_data(s)
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if altchars is not None:
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altchars = _bytes_from_decode_data(altchars)
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assert len(altchars) == 2, repr(altchars)
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s = _translate(s, _maketrans(altchars, b"+/"))
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if validate and not re.match(b"^[A-Za-z0-9+/]*=*$", s):
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raise binascii.Error("Non-base64 digit found")
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return binascii.a2b_base64(s)
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def standard_b64encode(s):
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"""Encode a byte string using the standard Base64 alphabet.
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s is the byte string to encode. The encoded byte string is returned.
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"""
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return b64encode(s)
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def standard_b64decode(s):
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"""Decode a byte string encoded with the standard Base64 alphabet.
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s is the byte string to decode. The decoded byte string is
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returned. binascii.Error is raised if the input is incorrectly
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padded or if there are non-alphabet characters present in the
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input.
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"""
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return b64decode(s)
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# _urlsafe_encode_translation = _maketrans(b'+/', b'-_')
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# _urlsafe_decode_translation = _maketrans(b'-_', b'+/')
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def urlsafe_b64encode(s):
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"""Encode a byte string using a url-safe Base64 alphabet.
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s is the byte string to encode. The encoded byte string is
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returned. The alphabet uses '-' instead of '+' and '_' instead of
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'/'.
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"""
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# return b64encode(s).translate(_urlsafe_encode_translation)
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return b64encode(s, b"-_").rstrip(b"\n")
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def urlsafe_b64decode(s):
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"""Decode a byte string encoded with the standard Base64 alphabet.
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s is the byte string to decode. The decoded byte string is
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returned. binascii.Error is raised if the input is incorrectly
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padded or if there are non-alphabet characters present in the
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input.
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The alphabet uses '-' instead of '+' and '_' instead of '/'.
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"""
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# s = _bytes_from_decode_data(s)
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# s = s.translate(_urlsafe_decode_translation)
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# return b64decode(s)
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raise NotImplementedError()
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# Base32 encoding/decoding must be done in Python
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_b32alphabet = {
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0: b"A",
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9: b"J",
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18: b"S",
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27: b"3",
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1: b"B",
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10: b"K",
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19: b"T",
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28: b"4",
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2: b"C",
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11: b"L",
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20: b"U",
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29: b"5",
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3: b"D",
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12: b"M",
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21: b"V",
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30: b"6",
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4: b"E",
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13: b"N",
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22: b"W",
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31: b"7",
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5: b"F",
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14: b"O",
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23: b"X",
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6: b"G",
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15: b"P",
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24: b"Y",
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7: b"H",
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16: b"Q",
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25: b"Z",
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8: b"I",
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17: b"R",
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26: b"2",
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}
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_b32tab = [v[0] for k, v in sorted(_b32alphabet.items())]
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_b32rev = dict([(v[0], k) for k, v in _b32alphabet.items()])
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def b32encode(s):
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"""Encode a byte string using Base32.
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s is the byte string to encode. The encoded byte string is returned.
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"""
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if not isinstance(s, bytes_types):
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raise TypeError("expected bytes, not %s" % s.__class__.__name__)
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quanta, leftover = divmod(len(s), 5)
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# Pad the last quantum with zero bits if necessary
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if leftover:
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s = s + bytes(5 - leftover) # Don't use += !
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quanta += 1
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encoded = bytearray()
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for i in range(quanta):
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# c1 and c2 are 16 bits wide, c3 is 8 bits wide. The intent of this
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# code is to process the 40 bits in units of 5 bits. So we take the 1
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# leftover bit of c1 and tack it onto c2. Then we take the 2 leftover
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# bits of c2 and tack them onto c3. The shifts and masks are intended
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# to give us values of exactly 5 bits in width.
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c1, c2, c3 = struct.unpack("!HHB", s[i * 5 : (i + 1) * 5])
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c2 += (c1 & 1) << 16 # 17 bits wide
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c3 += (c2 & 3) << 8 # 10 bits wide
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encoded += bytes(
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[
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_b32tab[c1 >> 11], # bits 1 - 5
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_b32tab[(c1 >> 6) & 0x1F], # bits 6 - 10
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_b32tab[(c1 >> 1) & 0x1F], # bits 11 - 15
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_b32tab[c2 >> 12], # bits 16 - 20 (1 - 5)
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_b32tab[(c2 >> 7) & 0x1F], # bits 21 - 25 (6 - 10)
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_b32tab[(c2 >> 2) & 0x1F], # bits 26 - 30 (11 - 15)
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_b32tab[c3 >> 5], # bits 31 - 35 (1 - 5)
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_b32tab[c3 & 0x1F], # bits 36 - 40 (1 - 5)
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]
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)
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# Adjust for any leftover partial quanta
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if leftover == 1:
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encoded = encoded[:-6] + b"======"
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elif leftover == 2:
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encoded = encoded[:-4] + b"===="
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elif leftover == 3:
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encoded = encoded[:-3] + b"==="
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elif leftover == 4:
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encoded = encoded[:-1] + b"="
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return bytes(encoded)
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def b32decode(s, casefold=False, map01=None):
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"""Decode a Base32 encoded byte string.
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s is the byte string to decode. Optional casefold is a flag
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specifying whether a lowercase alphabet is acceptable as input.
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For security purposes, the default is False.
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RFC 3548 allows for optional mapping of the digit 0 (zero) to the
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letter O (oh), and for optional mapping of the digit 1 (one) to
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either the letter I (eye) or letter L (el). The optional argument
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map01 when not None, specifies which letter the digit 1 should be
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mapped to (when map01 is not None, the digit 0 is always mapped to
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the letter O). For security purposes the default is None, so that
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0 and 1 are not allowed in the input.
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The decoded byte string is returned. binascii.Error is raised if
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the input is incorrectly padded or if there are non-alphabet
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characters present in the input.
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"""
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s = _bytes_from_decode_data(s)
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quanta, leftover = divmod(len(s), 8)
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if leftover:
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raise binascii.Error("Incorrect padding")
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# Handle section 2.4 zero and one mapping. The flag map01 will be either
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# False, or the character to map the digit 1 (one) to. It should be
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# either L (el) or I (eye).
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if map01 is not None:
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map01 = _bytes_from_decode_data(map01)
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assert len(map01) == 1, repr(map01)
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s = _translate(s, _maketrans(b"01", b"O" + map01))
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if casefold:
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s = s.upper()
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# Strip off pad characters from the right. We need to count the pad
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# characters because this will tell us how many null bytes to remove from
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# the end of the decoded string.
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padchars = s.find(b"=")
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if padchars > 0:
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padchars = len(s) - padchars
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s = s[:-padchars]
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else:
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padchars = 0
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# Now decode the full quanta
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parts = []
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acc = 0
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shift = 35
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for c in s:
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val = _b32rev.get(c)
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if val is None:
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raise binascii.Error("Non-base32 digit found")
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acc += _b32rev[c] << shift
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shift -= 5
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if shift < 0:
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parts.append(binascii.unhexlify(bytes("%010x" % acc, "ascii")))
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acc = 0
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shift = 35
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# Process the last, partial quanta
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last = binascii.unhexlify(bytes("%010x" % acc, "ascii"))
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if padchars == 0:
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last = b"" # No characters
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elif padchars == 1:
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last = last[:-1]
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elif padchars == 3:
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last = last[:-2]
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elif padchars == 4:
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last = last[:-3]
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elif padchars == 6:
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last = last[:-4]
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else:
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raise binascii.Error("Incorrect padding")
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parts.append(last)
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return b"".join(parts)
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# RFC 3548, Base 16 Alphabet specifies uppercase, but hexlify() returns
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# lowercase. The RFC also recommends against accepting input case
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# insensitively.
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def b16encode(s):
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"""Encode a byte string using Base16.
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s is the byte string to encode. The encoded byte string is returned.
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"""
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if not isinstance(s, bytes_types):
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raise TypeError("expected bytes, not %s" % s.__class__.__name__)
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return binascii.hexlify(s).upper()
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def b16decode(s, casefold=False):
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"""Decode a Base16 encoded byte string.
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s is the byte string to decode. Optional casefold is a flag
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specifying whether a lowercase alphabet is acceptable as input.
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For security purposes, the default is False.
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The decoded byte string is returned. binascii.Error is raised if
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s were incorrectly padded or if there are non-alphabet characters
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present in the string.
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"""
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s = _bytes_from_decode_data(s)
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if casefold:
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s = s.upper()
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if re.search(b"[^0-9A-F]", s):
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raise binascii.Error("Non-base16 digit found")
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return binascii.unhexlify(s)
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# Legacy interface. This code could be cleaned up since I don't believe
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# binascii has any line length limitations. It just doesn't seem worth it
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# though. The files should be opened in binary mode.
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MAXLINESIZE = 76 # Excluding the CRLF
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MAXBINSIZE = (MAXLINESIZE // 4) * 3
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def encode(input, output):
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"""Encode a file; input and output are binary files."""
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while True:
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s = input.read(MAXBINSIZE)
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if not s:
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break
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while len(s) < MAXBINSIZE:
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ns = input.read(MAXBINSIZE - len(s))
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if not ns:
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break
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s += ns
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line = binascii.b2a_base64(s)
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output.write(line)
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def decode(input, output):
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"""Decode a file; input and output are binary files."""
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while True:
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line = input.readline()
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if not line:
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break
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s = binascii.a2b_base64(line)
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output.write(s)
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def encodebytes(s):
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"""Encode a bytestring into a bytestring containing multiple lines
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of base-64 data."""
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if not isinstance(s, bytes_types):
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raise TypeError("expected bytes, not %s" % s.__class__.__name__)
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pieces = []
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for i in range(0, len(s), MAXBINSIZE):
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chunk = s[i : i + MAXBINSIZE]
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pieces.append(binascii.b2a_base64(chunk))
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return b"".join(pieces)
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def encodestring(s):
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"""Legacy alias of encodebytes()."""
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import warnings
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warnings.warn("encodestring() is a deprecated alias, use encodebytes()", DeprecationWarning, 2)
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return encodebytes(s)
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def decodebytes(s):
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"""Decode a bytestring of base-64 data into a bytestring."""
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if not isinstance(s, bytes_types):
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raise TypeError("expected bytes, not %s" % s.__class__.__name__)
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return binascii.a2b_base64(s)
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def decodestring(s):
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"""Legacy alias of decodebytes()."""
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import warnings
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warnings.warn("decodestring() is a deprecated alias, use decodebytes()", DeprecationWarning, 2)
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return decodebytes(s)
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# Usable as a script...
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def main():
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"""Small main program"""
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import sys, getopt
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try:
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opts, args = getopt.getopt(sys.argv[1:], "deut")
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except getopt.error as msg:
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sys.stdout = sys.stderr
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print(msg)
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print(
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"""usage: %s [-d|-e|-u|-t] [file|-]
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-d, -u: decode
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-e: encode (default)
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-t: encode and decode string 'Aladdin:open sesame'"""
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% sys.argv[0]
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)
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sys.exit(2)
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func = encode
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for o, a in opts:
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if o == "-e":
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func = encode
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if o == "-d":
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func = decode
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if o == "-u":
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func = decode
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if o == "-t":
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test()
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return
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if args and args[0] != "-":
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with open(args[0], "rb") as f:
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func(f, sys.stdout.buffer)
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else:
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func(sys.stdin.buffer, sys.stdout.buffer)
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def test():
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s0 = b"Aladdin:open sesame"
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print(repr(s0))
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s1 = encodebytes(s0)
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print(repr(s1))
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s2 = decodebytes(s1)
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print(repr(s2))
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assert s0 == s2
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if __name__ == "__main__":
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main()
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