雷电芽衣
ed34831c20
_managed_files owns the file snapshot reader and public metadata helpers used by pinned directories, durable copies, and opaque snapshots; transaction staging owns read_target and same_identity_and_contents; dead helpers removed; hook_template no longer re-exports the guard generator; mypy targets win32 so _windows_security type-checks. Claude-Session: https://claude.ai/code/session_01Agoc9bRVE9KL7mmWtey9Vq
102 lines
3.2 KiB
Python
102 lines
3.2 KiB
Python
"""Bounded-memory snapshots for identity-sensitive opaque files."""
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from __future__ import annotations
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from dataclasses import dataclass
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import hashlib
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import os
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import stat
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from typing import Optional
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from ._managed_files import same_file_metadata
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from ._pinned_directory import PinnedDirectory
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_HASH_CHUNK_BYTES = 1024 * 1024
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@dataclass(frozen=True)
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class OpaqueFileSnapshot:
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"""Device, inode, mode, size, and SHA-256 without retaining the bytes."""
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device: int
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inode: int
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mode: int
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size: int
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sha256: str
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def _require_regular(
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metadata: os.stat_result,
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file_path: str,
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label: str,
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require_owner_only: bool,
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) -> None:
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if not stat.S_ISREG(metadata.st_mode) or stat.S_ISLNK(metadata.st_mode):
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raise OSError(f"{label} path is not a physical file: {file_path}")
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if os.name != "nt" and require_owner_only and metadata.st_mode & 0o077:
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raise PermissionError(
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f"{label} must be accessible only by its owner: {file_path}"
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)
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def stream_opaque_snapshot(
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directory: PinnedDirectory,
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file_path: str,
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label: str,
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*,
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require_owner_only: bool = True,
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) -> Optional[OpaqueFileSnapshot]:
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"""Hash one no-follow regular file in bounded chunks through a pinned parent."""
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name = directory.name_for(file_path)
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try:
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before = directory.stat_file(name)
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except FileNotFoundError:
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return None
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except OSError as error:
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raise OSError(f"Inspect {label} at {file_path}: {error}") from error
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_require_regular(before, file_path, label, require_owner_only)
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flags = os.O_RDONLY | getattr(os, "O_BINARY", 0)
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flags |= getattr(os, "O_CLOEXEC", 0) | getattr(os, "O_NOFOLLOW", 0)
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descriptor = -1
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try:
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descriptor = directory.open_file(name, flags)
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opened = os.fstat(descriptor)
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_require_regular(opened, file_path, label, require_owner_only)
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if not same_file_metadata(opened, before):
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raise OSError(f"{label} changed while opening: {file_path}")
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digest = hashlib.sha256()
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while True:
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chunk = os.read(descriptor, _HASH_CHUNK_BYTES)
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if not chunk:
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break
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digest.update(chunk)
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finished = os.fstat(descriptor)
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_require_regular(finished, file_path, label, require_owner_only)
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if not same_file_metadata(finished, opened):
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raise OSError(f"{label} changed while hashing: {file_path}")
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except OSError as error:
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raise OSError(f"Read {label} at {file_path}: {error}") from error
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finally:
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if descriptor >= 0:
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os.close(descriptor)
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try:
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visible = directory.stat_file(name)
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except FileNotFoundError as error:
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raise OSError(f"{label} changed while hashing: {file_path}") from error
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_require_regular(visible, file_path, label, require_owner_only)
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if not same_file_metadata(visible, finished):
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raise OSError(f"{label} changed while hashing: {file_path}")
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return OpaqueFileSnapshot(
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finished.st_dev,
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finished.st_ino,
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stat.S_IMODE(finished.st_mode),
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finished.st_size,
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digest.hexdigest(),
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)
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__all__ = ["OpaqueFileSnapshot", "stream_opaque_snapshot"]
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