86 lines
2.7 KiB
Python
86 lines
2.7 KiB
Python
"""add file expirations
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Revision ID: 939a08e1d6e5
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Revises: 7e246705da6a
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Create Date: 2022-11-22 12:16:32.517184
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"""
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# revision identifiers, used by Alembic.
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revision = '939a08e1d6e5'
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down_revision = '7e246705da6a'
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from alembic import op
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from flask import current_app
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from flask_sqlalchemy import SQLAlchemy
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from pathlib import Path
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import sqlalchemy as sa
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from sqlalchemy.ext.automap import automap_base
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from sqlalchemy.orm import Session
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import os
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import time
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""" For a file of a given size, determine the largest allowed lifespan of that file
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Based on the current app's configuration: Specifically, the MAX_CONTENT_LENGTH, as well
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as FHOST_{MIN,MAX}_EXPIRATION.
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This lifespan may be shortened by a user's request, but no files should be allowed to
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expire at a point after this number.
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Value returned is a duration in milliseconds.
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"""
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def get_max_lifespan(filesize: int) -> int:
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min_exp = current_app.config.get("FHOST_MIN_EXPIRATION", 30 * 24 * 60 * 60 * 1000)
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max_exp = current_app.config.get("FHOST_MAX_EXPIRATION", 365 * 24 * 60 * 60 * 1000)
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max_size = current_app.config.get("MAX_CONTENT_LENGTH", 256 * 1024 * 1024)
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return min_exp + int((-max_exp + min_exp) * (filesize / max_size - 1) ** 3)
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Base = automap_base()
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def upgrade():
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op.add_column('file', sa.Column('expiration', sa.BigInteger()))
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bind = op.get_bind()
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Base.prepare(autoload_with=bind)
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File = Base.classes.file
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session = Session(bind=bind)
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storage = Path(current_app.config["FHOST_STORAGE_PATH"])
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current_time = time.time() * 1000;
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# List of file hashes which have not expired yet
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# This could get really big for some servers
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try:
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unexpired_files = os.listdir(storage)
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except FileNotFoundError:
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return # There are no currently unexpired files
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# Calculate an expiration date for all existing files
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q = session.scalars(
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sa.select(File)
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.where(
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sa.not_(File.removed)
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)
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)
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updates = [] # We coalesce updates to the database here
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# SQLite has a hard limit on the number of variables so we
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# need to do this the slow way
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files = [f for f in q if f.sha256 in unexpired_files]
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for file in files:
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file_path = storage / file.sha256
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stat = os.stat(file_path)
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max_age = get_max_lifespan(stat.st_size) # How long the file is allowed to live, in ms
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file_birth = stat.st_mtime * 1000 # When the file was created, in ms
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updates.append({'id': file.id, 'expiration': int(file_birth + max_age)})
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# Apply coalesced updates
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session.bulk_update_mappings(File, updates)
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session.commit()
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def downgrade():
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op.drop_column('file', 'expiration')
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