wehub-resource-sync
54 lines
1.6 KiB
Python
54 lines
1.6 KiB
Python
# Copyright (C) CVAT.ai Corporation
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#
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# SPDX-License-Identifier: MIT
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from __future__ import annotations
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from pathlib import Path, PurePath
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from typing import TYPE_CHECKING
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if TYPE_CHECKING:
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from _typeshed import StrPath
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def problem_with_untrusted_path(
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untrusted_path: str, /, *, allow_trailing_slash: bool = False
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) -> str | None:
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"""
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If untrusted_path is a valid relative path in canonical form, returns None.
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Otherwise, returns a string describing the problem.
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"""
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p = PurePath(untrusted_path)
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if not p.parts:
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return "path is empty"
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if p.root or p.drive:
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return "path is not relative"
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if ".." in p.parts:
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return "path contains a '..' segment"
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if untrusted_path.endswith("/") and not allow_trailing_slash:
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return "path has a trailing slash"
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if p.as_posix() != untrusted_path.removesuffix("/"):
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return "path is not in canonical form"
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return None
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def join_untrusted_path(root: StrPath, untrusted_path: StrPath, /) -> Path:
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"""
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Returns the result of joining root and untrusted_path, if the result is a child of root.
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Otherwise, raises ValueError.
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This function should be used as a second line of defense against path traversal attacks.
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If possible, any paths received from the user should first be validated with problem_with_untrusted_path,
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which doesn't require a root and provides more specific error messages.
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"""
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joined = Path(root, untrusted_path).resolve()
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joined.relative_to(root) # Will raise ValueError if joined is not a child of root.
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return joined
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