Add support for expiring files
SUPPLEMENTALLY: - Add an `expiration` field to the `file` table of the database - Produce a migration for the above change - Overhaul the cleanup script, and integrate into fhost.py (now run using FLASK_APP=fhost flask prune) - Replace the old cleanup script with a deprecation notice - Add information about how to expire files to the index - Update the README with information about the new script
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5 changed files with 215 additions and 52 deletions
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@ -27,8 +27,8 @@ For all other servers, set ``FHOST_USE_X_ACCEL_REDIRECT`` to ``False`` and
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Otherwise, Flask will serve the file with chunked encoding, which sucks and
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should be avoided at all costs.
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To make files expire, simply create a cronjob that runs ``cleanup.py`` every
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now and then.
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To make files expire, simply create a cronjob that runs ``FLASK_APP=fhost
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flask prune`` every now and then.
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Before running the service for the first time, run ``FLASK_APP=fhost flask db upgrade``.
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48
cleanup.py
48
cleanup.py
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@ -1,44 +1,8 @@
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#!/usr/bin/env python3
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"""
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Copyright © 2020 Mia Herkt
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Licensed under the EUPL, Version 1.2 or - as soon as approved
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by the European Commission - subsequent versions of the EUPL
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(the "License");
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You may not use this work except in compliance with the License.
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You may obtain a copy of the license at:
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https://joinup.ec.europa.eu/software/page/eupl
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Unless required by applicable law or agreed to in writing,
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software distributed under the License is distributed on an
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"AS IS" basis, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
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either express or implied.
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See the License for the specific language governing permissions
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and limitations under the License.
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"""
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import os
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import sys
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import time
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import datetime
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from fhost import app
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os.chdir(os.path.dirname(sys.argv[0]))
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os.chdir(app.config["FHOST_STORAGE_PATH"])
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files = [f for f in os.listdir(".")]
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maxs = app.config["MAX_CONTENT_LENGTH"]
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mind = 30
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maxd = 365
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for f in files:
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stat = os.stat(f)
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systime = time.time()
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age = datetime.timedelta(seconds=(systime - stat.st_mtime)).days
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maxage = mind + (-maxd + mind) * (stat.st_size / maxs - 1) ** 3
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if age >= maxage:
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os.remove(f)
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print("This script has been replaced!!")
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print("Instead, please run")
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print("")
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print(" $ FLASK_APP=fhost flask prune --legacy")
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print("")
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exit(1);
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187
fhost.py
187
fhost.py
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@ -22,12 +22,17 @@
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from flask import Flask, abort, make_response, redirect, request, send_from_directory, url_for, Response, render_template
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from flask_sqlalchemy import SQLAlchemy
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from flask_migrate import Migrate
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from sqlalchemy import and_
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from jinja2.exceptions import *
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from jinja2 import ChoiceLoader, FileSystemLoader
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from hashlib import sha256
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from magic import Magic
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from mimetypes import guess_extension
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import click
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import os
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import sys
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import time
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import typing
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import requests
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from validators import url as url_valid
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from pathlib import Path
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@ -121,12 +126,14 @@ class File(db.Model):
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addr = db.Column(db.UnicodeText)
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removed = db.Column(db.Boolean, default=False)
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nsfw_score = db.Column(db.Float)
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expiration = db.Column(db.BigInteger)
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def __init__(self, sha256, ext, mime, addr):
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def __init__(self, sha256, ext, mime, addr, expiration):
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self.sha256 = sha256
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self.ext = ext
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self.mime = mime
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self.addr = addr
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self.expiration = expiration
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def getname(self):
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return u"{0}{1}".format(su.enbase(self.id), self.ext)
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@ -139,7 +146,16 @@ class File(db.Model):
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else:
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return url_for("get", path=n, _external=True) + "\n"
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def store(file_, addr):
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"""
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requested_expiration can be:
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- None, to use the longest allowed file lifespan
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- a duration (in hours) that the file should live for
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- a timestamp in epoch millis that the file should expire at
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Any value greater that the longest allowed file lifespan will be rounded down to that
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value.
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"""
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def store(file_, requested_expiration: typing.Optional[int], addr):
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data = file_.read()
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digest = sha256(data).hexdigest()
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@ -175,15 +191,51 @@ class File(db.Model):
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return ext[:app.config["FHOST_MAX_EXT_LENGTH"]] or ".bin"
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f = File.query.filter_by(sha256=digest).first()
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# Returns the epoch millisecond that this file should expire
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#
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# Uses the expiration time provided by the user (requested_expiration)
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# upper-bounded by an algorithm that computes the size based on the size of the
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# file.
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#
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# That is, all files are assigned a computed expiration, which can voluntarily
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# shortened by the user either by providing a timestamp in epoch millis or a
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# duration in hours.
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def get_expiration() -> int:
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current_epoch_millis = time.time() * 1000;
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# Maximum lifetime of the file in milliseconds
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this_files_max_lifespan = get_max_lifespan(len(data));
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# The latest allowed expiration date for this file, in epoch millis
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this_files_max_expiration = this_files_max_lifespan + 1000 * time.time();
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if requested_expiration is None:
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return this_files_max_expiration
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elif requested_expiration < 1650460320000:
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# Treat the requested expiration time as a duration in hours
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requested_expiration_ms = requested_expiration * 60 * 60 * 1000
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return min(this_files_max_expiration, current_epoch_millis + requested_expiration_ms)
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else:
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# Treat the requested expiration time as a timestamp in epoch millis
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return min(this_files_max_expiration, requested_expiration);
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f = File.query.filter_by(sha256=digest).first()
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if f:
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# If the file already exists
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if f.removed:
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# The file was removed by moderation, so don't accept it back
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abort(451)
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if f.expiration is None:
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# The file has expired, so give it a new expiration date
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f.expiration = get_expiration()
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else:
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# The file already exists, update the expiration if needed
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f.expiration = max(f.expiration, get_expiration())
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else:
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mime = get_mime()
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ext = get_ext(mime)
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f = File(digest, ext, mime, addr)
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expiration = get_expiration()
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f = File(digest, ext, mime, addr, expiration)
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f.addr = addr
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@ -260,11 +312,20 @@ def in_upload_bl(addr):
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return False
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def store_file(f, addr):
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"""
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requested_expiration can be:
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- None, to use the longest allowed file lifespan
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- a duration (in hours) that the file should live for
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- a timestamp in epoch millis that the file should expire at
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Any value greater that the longest allowed file lifespan will be rounded down to that
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value.
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"""
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def store_file(f, requested_expiration: typing.Optional[int], addr):
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if in_upload_bl(addr):
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return "Your host is blocked from uploading files.\n", 451
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sf = File.store(f, addr)
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sf = File.store(f, requested_expiration, addr)
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return sf.geturl()
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@ -289,7 +350,7 @@ def store_url(url, addr):
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f = urlfile(read=r.raw.read, content_type=r.headers["content-type"], filename="")
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return store_file(f, addr)
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return store_file(f, None, addr)
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else:
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abort(413)
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else:
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@ -336,7 +397,23 @@ def fhost():
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sf = None
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if "file" in request.files:
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return store_file(request.files["file"], request.remote_addr)
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try:
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# Store the file with the requested expiration date
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return store_file(
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request.files["file"],
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int(request.form["expires"]),
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request.remote_addr
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)
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except ValueError:
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# The requested expiration date wasn't properly formed
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abort(400)
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except KeyError:
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# No expiration date was requested, store with the max lifespan
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return store_file(
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request.files["file"],
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None,
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request.remote_addr
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)
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elif "url" in request.form:
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return store_url(request.form["url"], request.remote_addr)
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elif "shorten" in request.form:
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@ -364,3 +441,97 @@ def ehandler(e):
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return render_template(f"{e.code}.html", id=id), e.code
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except TemplateNotFound:
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return "Segmentation fault\n", e.code
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@app.cli.command("prune")
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@click.option(
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'-l', '--legacy',
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is_flag=True,
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default=False,
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help="Also look for legacy files"
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)
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def prune(legacy: bool):
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"""
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Clean up expired files
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Deletes any files from the filesystem which have hit their expiration time. This
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doesn't remove them from the database, only from the filesystem. It's recommended
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that server owners run this command regularly, or set it up on a timer.
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Server owners who recently applied a migration that creates legacy files should run
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this script with the --legacy/-l flag enabled for at least FHOST_MAX_EXPIRATION.
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"""
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current_time = time.time() * 1000;
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# The path to where uploaded files are stored
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storage = Path(app.config["FHOST_STORAGE_PATH"])
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# A list of all files who've passed their expiration times
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expired_files = File.query\
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.where(
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and_(
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File.expiration.is_not(None),
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File.expiration < current_time
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)
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).all()
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files_removed = 0;
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# For every expired file...
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for file in expired_files:
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# Log the file we're about to remove
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file_name = file.getname()
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file_hash = file.sha256
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file_path = storage / file_hash
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print(f"Removing expired file {file_name} [{file_hash}]")
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# Remove it from the file system
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try:
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os.remove(file_path)
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files_removed += 1;
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except FileNotFoundError:
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pass # If the file was already gone, we're good
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except OSError as e:
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print(e)
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print(
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"\n------------------------------------"
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"Encountered an error while trying to remove file {file_path}. Double"
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"check to make sure the server is configured correctly, permissions are"
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"okay, and everything is ship shape, then try again.")
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return;
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# Finally, mark that the file was removed
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file.expiration = None;
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db.session.commit()
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# Prior to 0x0 tracking file expiration times, files were removed by scanning the
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# filesystem. If this system was recently migrated from the old system, there might
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# still be files whose expirations aren't tracked and must be noticed the old way.
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# Therefore, we perform an additional check on files in the upload directory.
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if legacy:
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for file in os.listdir(storage):
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file_path = storage / file
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stat = os.stat(file_path)
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file_age = (current_time - stat.st_mtime * 1000) # How long the file has existed, in ms
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max_age = get_max_lifespan(stat.st_size)
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if file_age > max_age:
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print(f"Removing legacy file {file_path}")
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os.remove(file_path)
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files_removed += 1;
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print(f"\nDone! {files_removed} file(s) removed")
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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 = app.config.get("FHOST_MIN_EXPIRATION", 30 * 24 * 60 * 60 * 1000)
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max_exp = app.config.get("FHOST_MAX_EXPIRATION", 365 * 24 * 60 * 60 * 1000)
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max_size = 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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22
migrations/versions/939a08e1d6e5_.py
Normal file
22
migrations/versions/939a08e1d6e5_.py
Normal file
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"""add file expirations [creates legacy files]
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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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import sqlalchemy as sa
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def upgrade():
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op.add_column('file', sa.Column('expiration', sa.BigInteger()))
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def downgrade():
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op.drop_column('file', 'expiration')
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@ -11,6 +11,12 @@ Or you can shorten URLs:
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File URLs are valid for at least 30 days and up to a year (see below).
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Shortened URLs do not expire.
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Files can be set to expire sooner by adding an "expires" parameter (in hours)
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curl -F'file=@yourfile.png' -F'expires=24' {{ fhost_url }}
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OR by setting "expires" to a timestamp in epoch milliseconds
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curl -F'file=@yourfile.png' -F'expires=1681996320000' {{ fhost_url }}
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{% set max_size = config["MAX_CONTENT_LENGTH"]|filesizeformat(True) %}
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Maximum file size: {{ max_size }}
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Not allowed: {{ config["FHOST_MIME_BLACKLIST"]|join(", ") }}
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