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# Copyright 2016-present MongoDB, Inc.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
#
# Some changes copyright 2021-present Matthias Valvekens,
# licensed under the license of the pyHanko project (see LICENSE file).
"""An implementation of RFC4013 SASLprep."""
__all__ = ["saslprep"]
import stringprep
import unicodedata
from typing import Callable, Tuple
from pdf2zh.pdfexceptions import PDFValueError
# RFC4013 section 2.3 prohibited output.
_PROHIBITED: Tuple[Callable[[str], bool], ...] = (
# A strict reading of RFC 4013 requires table c12 here, but
# characters from it are mapped to SPACE in the Map step. Can
# normalization reintroduce them somehow?
stringprep.in_table_c12,
stringprep.in_table_c21_c22,
stringprep.in_table_c3,
stringprep.in_table_c4,
stringprep.in_table_c5,
stringprep.in_table_c6,
stringprep.in_table_c7,
stringprep.in_table_c8,
stringprep.in_table_c9,
)
def saslprep(data: str, prohibit_unassigned_code_points: bool = True) -> str:
"""An implementation of RFC4013 SASLprep.
:param data:
The string to SASLprep.
:param prohibit_unassigned_code_points:
RFC 3454 and RFCs for various SASL mechanisms distinguish between
`queries` (unassigned code points allowed) and
`stored strings` (unassigned code points prohibited). Defaults
to ``True`` (unassigned code points are prohibited).
:return: The SASLprep'ed version of `data`.
"""
if prohibit_unassigned_code_points:
prohibited = _PROHIBITED + (stringprep.in_table_a1,)
else:
prohibited = _PROHIBITED
# RFC3454 section 2, step 1 - Map
# RFC4013 section 2.1 mappings
# Map Non-ASCII space characters to SPACE (U+0020). Map
# commonly mapped to nothing characters to, well, nothing.
in_table_c12 = stringprep.in_table_c12
in_table_b1 = stringprep.in_table_b1
data = "".join(
[
"\u0020" if in_table_c12(elt) else elt
for elt in data
if not in_table_b1(elt)
],
)
# RFC3454 section 2, step 2 - Normalize
# RFC4013 section 2.2 normalization
data = unicodedata.ucd_3_2_0.normalize("NFKC", data)
in_table_d1 = stringprep.in_table_d1
if in_table_d1(data[0]):
if not in_table_d1(data[-1]):
# RFC3454, Section 6, #3. If a string contains any
# RandALCat character, the first and last characters
# MUST be RandALCat characters.
raise PDFValueError("SASLprep: failed bidirectional check")
# RFC3454, Section 6, #2. If a string contains any RandALCat
# character, it MUST NOT contain any LCat character.
prohibited = prohibited + (stringprep.in_table_d2,)
else:
# RFC3454, Section 6, #3. Following the logic of #3, if
# the first character is not a RandALCat, no other character
# can be either.
prohibited = prohibited + (in_table_d1,)
# RFC3454 section 2, step 3 and 4 - Prohibit and check bidi
for char in data:
if any(in_table(char) for in_table in prohibited):
raise PDFValueError("SASLprep: failed prohibited character check")
return data
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