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base64.py
#! /usr/bin/python3.9 """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 re 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', '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', ] 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 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. """ encoded = binascii.b2a_base64(s, 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. """ 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.fullmatch(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 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 _b32alphabet = b'ABCDEFGHIJKLMNOPQRSTUVWXYZ234567' _b32tab2 = None _b32rev = None def b32encode(s): """Encode the bytes-like object s using Base32 and return a bytes object. """ 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 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 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 the Base32 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. 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 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. """ 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) 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 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') leftover = (43 - 5 * padchars) // 8 # 1: 4, 3: 3, 4: 2, 6: 1 decoded[-5:] = last[:leftover] 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 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 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 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. wrapcol controls whether the output should have newline (b'\\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 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: _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 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 _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) 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 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 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()
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