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159 lines
4.0 KiB
Python
159 lines
4.0 KiB
Python
"""
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A module that loads pre-generated test vectors.
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:ivar DATA_PATH: The path of the file containing test vectors.
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:ivar capabilities: The capability test vectors.
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"""
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from __future__ import annotations
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from typing import TextIO
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from attrs import frozen
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from yaml import safe_load
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from base64 import b64encode, b64decode
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from twisted.python.filepath import FilePath
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from ..util import CHK, SSK
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DATA_PATH: FilePath = FilePath(__file__).sibling("test_vectors.yaml")
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# The version of the persisted test vector data this code can interpret.
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CURRENT_VERSION: str = "2023-01-16.2"
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@frozen
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class Sample:
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"""
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Some instructions for building a long byte string.
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:ivar seed: Some bytes to repeat some times to produce the string.
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:ivar length: The length of the desired byte string.
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"""
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seed: bytes
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length: int
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@frozen
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class Param:
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"""
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Some ZFEC parameters.
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"""
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required: int
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total: int
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# CHK have a max of 256 shares. SDMF / MDMF have a max of 255 shares!
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# Represent max symbolically and resolve it when we know what format we're
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# dealing with.
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MAX_SHARES = "max"
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@frozen
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class SeedParam:
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"""
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Some ZFEC parameters, almost.
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:ivar required: The number of required shares.
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:ivar total: Either the number of total shares or the constant
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``MAX_SHARES`` to indicate that the total number of shares should be
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the maximum number supported by the object format.
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"""
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required: int
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total: int | str
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def realize(self, max_total: int) -> Param:
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"""
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Create a ``Param`` from this object's values, possibly
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substituting the given real value for total if necessary.
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:param max_total: The value to use to replace ``MAX_SHARES`` if
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necessary.
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"""
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if self.total == MAX_SHARES:
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return Param(self.required, max_total)
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return Param(self.required, self.total)
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@frozen
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class Case:
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"""
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Represent one case for which we want/have a test vector.
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"""
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seed_params: Param
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convergence: bytes
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seed_data: Sample
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fmt: CHK | SSK
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@property
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def data(self):
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return stretch(self.seed_data.seed, self.seed_data.length)
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@property
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def params(self):
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return self.seed_params.realize(self.fmt.max_shares)
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def encode_bytes(b: bytes) -> str:
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"""
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Base64 encode some bytes to text so they are representable in JSON.
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"""
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return b64encode(b).decode("ascii")
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def decode_bytes(b: str) -> bytes:
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"""
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Base64 decode some text to bytes.
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"""
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return b64decode(b.encode("ascii"))
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def stretch(seed: bytes, size: int) -> bytes:
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"""
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Given a simple description of a byte string, return the byte string
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itself.
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"""
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assert isinstance(seed, bytes)
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assert isinstance(size, int)
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assert size > 0
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assert len(seed) > 0
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multiples = size // len(seed) + 1
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return (seed * multiples)[:size]
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def load_format(serialized: dict) -> CHK | SSK:
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if serialized["kind"] == "chk":
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return CHK.load(serialized["params"])
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elif serialized["kind"] == "ssk":
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return SSK.load(serialized["params"])
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else:
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raise ValueError(f"Unrecognized format: {serialized}")
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def load_capabilities(f: TextIO) -> dict[Case, str]:
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data = safe_load(f)
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if data is None:
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return {}
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if data["version"] != CURRENT_VERSION:
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print(
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f"Current version is {CURRENT_VERSION}; "
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f"cannot load version {data['version']} data."
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)
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return {}
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return {
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Case(
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seed_params=SeedParam(case["zfec"]["required"], case["zfec"]["total"]),
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convergence=decode_bytes(case["convergence"]),
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seed_data=Sample(decode_bytes(case["sample"]["seed"]), case["sample"]["length"]),
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fmt=load_format(case["format"]),
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): case["expected"]
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for case
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in data["vector"]
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}
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try:
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with DATA_PATH.open() as f:
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capabilities: dict[Case, str] = load_capabilities(f)
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except FileNotFoundError:
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capabilities = {}
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