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a13d27bfb5
Writing the output PDF to stdout (ocrmypdf in.pdf -) previously relied on an honor system: no in-process code -- third-party libraries, plugins, or stray print() calls -- was supposed to write to stdout, enforced only indirectly. A single accidental write to fd 1 would silently corrupt the output PDF. Enforce this at the OS level. At CLI startup, before plugins load or any worker process/thread starts, save the real stdout via os.dup() and point fd 1 at stderr, so stray writes are diverted to stderr while only the final "produce the PDF" step writes to the preserved descriptor. Exposed as the opt-in public API function configure_stdout_protection(), mirroring configure_logging(); it is not enabled inside ocr() so in-process library users keep their own stdout. Also fix check_requested_output_file() to test the preserved real stdout for tty-ness, since after the redirect sys.stdout reports stderr's status. Fold unreleased v17.7.2 notes into v17.8.0.
43 lines
1.1 KiB
Python
43 lines
1.1 KiB
Python
# SPDX-FileCopyrightText: 2024 James R. Barlow
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# SPDX-License-Identifier: MIT
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"""Test plugin that deliberately writes garbage to stdout.
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Used to verify that OCRmyPDF's stdout protection diverts stray writes (from
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plugins or libraries) to stderr, so that a PDF written to stdout is never
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corrupted. Pollutes at three points: plugin import (main process), the
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``validate`` hook (main process), and the ``filter_ocr_image`` hook (worker
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process/thread).
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"""
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from __future__ import annotations
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import os
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import sys
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from ocrmypdf import hookimpl
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POLLUTION = b'POLLUTION'
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def _pollute(where: bytes) -> None:
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# Write to file descriptor 1 directly (as a careless C library might) and
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# via Python's sys.stdout (as a stray print() might).
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os.write(1, POLLUTION + b'-fd1-' + where + b'\n')
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print(POLLUTION.decode() + '-stdout-' + where.decode())
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sys.stdout.flush()
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# Pollute at import time, which happens while plugins are being loaded.
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_pollute(b'import')
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@hookimpl
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def validate(pdfinfo, options):
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_pollute(b'validate')
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@hookimpl
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def filter_ocr_image(page, image):
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_pollute(b'filter_ocr_image')
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return image
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