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0x0/fhost.py

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#!/usr/bin/env python3
# -*- coding: utf-8 -*-
"""
Copyright © 2020 Mia Herkt
Licensed under the EUPL, Version 1.2 or - as soon as approved
by the European Commission - subsequent versions of the EUPL
(the "License");
You may not use this work except in compliance with the License.
You may obtain a copy of the license at:
https://joinup.ec.europa.eu/software/page/eupl
Unless required by applicable law or agreed to in writing,
software distributed under the License is distributed on an
"AS IS" basis, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
either express or implied.
See the License for the specific language governing permissions
and limitations under the License.
"""
from flask import Flask, abort, make_response, redirect, request, send_from_directory, url_for, Response, render_template
from flask_sqlalchemy import SQLAlchemy
from flask_migrate import Migrate
from sqlalchemy import and_, or_
from jinja2.exceptions import *
from jinja2 import ChoiceLoader, FileSystemLoader
from hashlib import sha256
from magic import Magic
from mimetypes import guess_extension
import click
import os
import sys
import time
import datetime
import typing
import requests
import secrets
from validators import url as url_valid
from pathlib import Path
app = Flask(__name__, instance_relative_config=True)
app.config.update(
SQLALCHEMY_TRACK_MODIFICATIONS = False,
PREFERRED_URL_SCHEME = "https", # nginx users: make sure to have 'uwsgi_param UWSGI_SCHEME $scheme;' in your config
MAX_CONTENT_LENGTH = 256 * 1024 * 1024,
MAX_URL_LENGTH = 4096,
USE_X_SENDFILE = False,
FHOST_USE_X_ACCEL_REDIRECT = True, # expect nginx by default
FHOST_STORAGE_PATH = "up",
FHOST_MAX_EXT_LENGTH = 9,
FHOST_SECRET_BYTES = 16,
FHOST_EXT_OVERRIDE = {
"audio/flac" : ".flac",
"image/gif" : ".gif",
"image/jpeg" : ".jpg",
"image/png" : ".png",
"image/svg+xml" : ".svg",
"video/webm" : ".webm",
"video/x-matroska" : ".mkv",
"application/octet-stream" : ".bin",
"text/plain" : ".log",
"text/plain" : ".txt",
"text/x-diff" : ".diff",
},
FHOST_MIME_BLACKLIST = [
"application/x-dosexec",
"application/java-archive",
"application/java-vm"
],
FHOST_UPLOAD_BLACKLIST = None,
NSFW_DETECT = False,
NSFW_THRESHOLD = 0.92,
VSCAN_SOCKET = None,
VSCAN_QUARANTINE_PATH = "quarantine",
VSCAN_IGNORE = [
"Eicar-Test-Signature",
"PUA.Win.Packer.XmMusicFile",
],
VSCAN_INTERVAL = datetime.timedelta(days=7),
URL_ALPHABET = "DEQhd2uFteibPwq0SWBInTpA_jcZL5GKz3YCR14Ulk87Jors9vNHgfaOmMXy6Vx-",
)
if not app.config["TESTING"]:
app.config.from_pyfile("config.py")
app.jinja_loader = ChoiceLoader([
FileSystemLoader(str(Path(app.instance_path) / "templates")),
app.jinja_loader
])
if app.config["DEBUG"]:
app.config["FHOST_USE_X_ACCEL_REDIRECT"] = False
if app.config["NSFW_DETECT"]:
from nsfw_detect import NSFWDetector
nsfw = NSFWDetector()
try:
mimedetect = Magic(mime=True, mime_encoding=False)
except:
print("""Error: You have installed the wrong version of the 'magic' module.
Please install python-magic.""")
sys.exit(1)
db = SQLAlchemy(app)
migrate = Migrate(app, db)
class URL(db.Model):
__tablename__ = "URL"
id = db.Column(db.Integer, primary_key = True)
url = db.Column(db.UnicodeText, unique = True)
def __init__(self, url):
self.url = url
def getname(self):
return su.enbase(self.id)
def geturl(self):
return url_for("get", path=self.getname(), _external=True) + "\n"
def get(url):
u = URL.query.filter_by(url=url).first()
if not u:
u = URL(url)
db.session.add(u)
db.session.commit()
return u
class File(db.Model):
id = db.Column(db.Integer, primary_key = True)
sha256 = db.Column(db.String, unique = True)
ext = db.Column(db.UnicodeText)
mime = db.Column(db.UnicodeText)
addr = db.Column(db.UnicodeText)
ua = db.Column(db.UnicodeText)
removed = db.Column(db.Boolean, default=False)
nsfw_score = db.Column(db.Float)
expiration = db.Column(db.BigInteger)
mgmt_token = db.Column(db.String)
secret = db.Column(db.String)
last_vscan = db.Column(db.DateTime)
size = db.Column(db.BigInteger)
def __init__(self, sha256, ext, mime, addr, ua, expiration, mgmt_token):
self.sha256 = sha256
self.ext = ext
self.mime = mime
self.addr = addr
self.ua = ua
self.expiration = expiration
self.mgmt_token = mgmt_token
@property
def is_nsfw(self) -> bool:
return self.nsfw_score and self.nsfw_score > app.config["NSFW_THRESHOLD"]
def getname(self):
return u"{0}{1}".format(su.enbase(self.id), self.ext)
def geturl(self):
n = self.getname()
if self.is_nsfw:
return url_for("get", path=n, secret=self.secret, _external=True, _anchor="nsfw") + "\n"
else:
return url_for("get", path=n, secret=self.secret, _external=True) + "\n"
def getpath(self) -> Path:
return Path(app.config["FHOST_STORAGE_PATH"]) / self.sha256
def delete(self, permanent=False):
self.expiration = None
self.mgmt_token = None
self.removed = permanent
self.getpath().unlink(missing_ok=True)
# Returns the epoch millisecond that a file should expire
#
# Uses the expiration time provided by the user (requested_expiration)
# upper-bounded by an algorithm that computes the size based on the size of the
# file.
#
# That is, all files are assigned a computed expiration, which can voluntarily
# shortened by the user either by providing a timestamp in epoch millis or a
# duration in hours.
def get_expiration(requested_expiration, size) -> int:
current_epoch_millis = time.time() * 1000;
# Maximum lifetime of the file in milliseconds
this_files_max_lifespan = get_max_lifespan(size);
# The latest allowed expiration date for this file, in epoch millis
this_files_max_expiration = this_files_max_lifespan + 1000 * time.time();
if requested_expiration is None:
return this_files_max_expiration
elif requested_expiration < 1650460320000:
# Treat the requested expiration time as a duration in hours
requested_expiration_ms = requested_expiration * 60 * 60 * 1000
return min(this_files_max_expiration, current_epoch_millis + requested_expiration_ms)
else:
# Treat the requested expiration time as a timestamp in epoch millis
return min(this_files_max_expiration, requested_expiration)
"""
requested_expiration can be:
- None, to use the longest allowed file lifespan
- a duration (in hours) that the file should live for
- a timestamp in epoch millis that the file should expire at
Any value greater that the longest allowed file lifespan will be rounded down to that
value.
"""
def store(file_, requested_expiration: typing.Optional[int], addr, ua, secret: bool):
data = file_.read()
digest = sha256(data).hexdigest()
def get_mime():
guess = mimedetect.from_buffer(data)
app.logger.debug(f"MIME - specified: '{file_.content_type}' - detected: '{guess}'")
if not file_.content_type or not "/" in file_.content_type or file_.content_type == "application/octet-stream":
mime = guess
else:
mime = file_.content_type
if mime in app.config["FHOST_MIME_BLACKLIST"] or guess in app.config["FHOST_MIME_BLACKLIST"]:
abort(415)
if len(mime) > 128:
abort(400)
if mime.startswith("text/") and not "charset" in mime:
mime += "; charset=utf-8"
return mime
def get_ext(mime):
ext = "".join(Path(file_.filename).suffixes[-2:])
if len(ext) > app.config["FHOST_MAX_EXT_LENGTH"]:
ext = Path(file_.filename).suffixes[-1]
gmime = mime.split(";")[0]
guess = guess_extension(gmime)
app.logger.debug(f"extension - specified: '{ext}' - detected: '{guess}'")
if not ext:
if gmime in app.config["FHOST_EXT_OVERRIDE"]:
ext = app.config["FHOST_EXT_OVERRIDE"][gmime]
elif guess:
ext = guess
else:
ext = ""
return ext[:app.config["FHOST_MAX_EXT_LENGTH"]] or ".bin"
expiration = File.get_expiration(requested_expiration, len(data))
isnew = True
f = File.query.filter_by(sha256=digest).first()
if f:
# If the file already exists
if f.removed:
# The file was removed by moderation, so don't accept it back
abort(451)
if f.expiration is None:
# The file has expired, so give it a new expiration date
f.expiration = expiration
# Also generate a new management token
f.mgmt_token = secrets.token_urlsafe()
else:
# The file already exists, update the expiration if needed
f.expiration = max(f.expiration, expiration)
isnew = False
else:
mime = get_mime()
ext = get_ext(mime)
mgmt_token = secrets.token_urlsafe()
f = File(digest, ext, mime, addr, ua, expiration, mgmt_token)
f.addr = addr
f.ua = ua
if isnew:
f.secret = None
if secret:
f.secret = secrets.token_urlsafe(app.config["FHOST_SECRET_BYTES"])
storage = Path(app.config["FHOST_STORAGE_PATH"])
storage.mkdir(parents=True, exist_ok=True)
p = storage / digest
if not p.is_file():
with open(p, "wb") as of:
of.write(data)
f.size = len(data)
if not f.nsfw_score and app.config["NSFW_DETECT"]:
f.nsfw_score = nsfw.detect(str(p))
db.session.add(f)
db.session.commit()
return f, isnew
class UrlEncoder(object):
def __init__(self,alphabet, min_length):
self.alphabet = alphabet
self.min_length = min_length
def enbase(self, x):
n = len(self.alphabet)
str = ""
while x > 0:
str = (self.alphabet[int(x % n)]) + str
x = int(x // n)
padding = self.alphabet[0] * (self.min_length - len(str))
return '%s%s' % (padding, str)
def debase(self, x):
n = len(self.alphabet)
result = 0
for i, c in enumerate(reversed(x)):
result += self.alphabet.index(c) * (n ** i)
return result
su = UrlEncoder(alphabet=app.config["URL_ALPHABET"], min_length=1)
def fhost_url(scheme=None):
if not scheme:
return url_for(".fhost", _external=True).rstrip("/")
else:
return url_for(".fhost", _external=True, _scheme=scheme).rstrip("/")
def is_fhost_url(url):
return url.startswith(fhost_url()) or url.startswith(fhost_url("https"))
def shorten(url):
if len(url) > app.config["MAX_URL_LENGTH"]:
abort(414)
if not url_valid(url) or is_fhost_url(url) or "\n" in url:
abort(400)
u = URL.get(url)
return u.geturl()
def in_upload_bl(addr):
if app.config["FHOST_UPLOAD_BLACKLIST"]:
with app.open_instance_resource(app.config["FHOST_UPLOAD_BLACKLIST"], "r") as bl:
check = addr.lstrip("::ffff:")
for l in bl.readlines():
if not l.startswith("#"):
if check == l.rstrip():
return True
return False
"""
requested_expiration can be:
- None, to use the longest allowed file lifespan
- a duration (in hours) that the file should live for
- a timestamp in epoch millis that the file should expire at
Any value greater that the longest allowed file lifespan will be rounded down to that
value.
"""
def store_file(f, requested_expiration: typing.Optional[int], addr, ua, secret: bool):
if in_upload_bl(addr):
return "Your host is blocked from uploading files.\n", 451
sf, isnew = File.store(f, requested_expiration, addr, ua, secret)
response = make_response(sf.geturl())
response.headers["X-Expires"] = sf.expiration
if isnew:
response.headers["X-Token"] = sf.mgmt_token
return response
def store_url(url, addr, ua, secret: bool):
if is_fhost_url(url):
abort(400)
h = { "Accept-Encoding" : "identity" }
r = requests.get(url, stream=True, verify=False, headers=h)
try:
r.raise_for_status()
except requests.exceptions.HTTPError as e:
return str(e) + "\n"
if "content-length" in r.headers:
l = int(r.headers["content-length"])
if l <= app.config["MAX_CONTENT_LENGTH"]:
def urlfile(**kwargs):
return type('',(),kwargs)()
f = urlfile(read=r.raw.read, content_type=r.headers["content-type"], filename="")
return store_file(f, None, addr, ua, secret)
else:
abort(413)
else:
abort(411)
def manage_file(f):
try:
assert(request.form["token"] == f.mgmt_token)
except:
abort(401)
if "delete" in request.form:
f.delete()
db.session.commit()
return ""
if "expires" in request.form:
try:
requested_expiration = int(request.form["expires"])
except ValueError:
abort(400)
f.expiration = File.get_expiration(requested_expiration, f.size)
db.session.commit()
return "", 202
abort(400)
@app.route("/<path:path>", methods=["GET", "POST"])
@app.route("/s/<secret>/<path:path>", methods=["GET", "POST"])
def get(path, secret=None):
p = Path(path.split("/", 1)[0])
sufs = "".join(p.suffixes[-2:])
name = p.name[:-len(sufs) or None]
if "." in name:
abort(404)
id = su.debase(name)
if sufs:
f = File.query.get(id)
if f and f.ext == sufs:
if f.secret != secret:
abort(404)
if f.removed:
abort(451)
fpath = f.getpath()
if not fpath.is_file():
abort(404)
if request.method == "POST":
return manage_file(f)
if app.config["FHOST_USE_X_ACCEL_REDIRECT"]:
response = make_response()
response.headers["Content-Type"] = f.mime
response.headers["Content-Length"] = f.size
response.headers["X-Accel-Redirect"] = "/" + str(fpath)
else:
response = send_from_directory(app.config["FHOST_STORAGE_PATH"], f.sha256, mimetype = f.mime)
response.headers["X-Expires"] = f.expiration
return response
else:
if request.method == "POST":
abort(405)
if "/" in path:
abort(404)
u = URL.query.get(id)
if u:
return redirect(u.url)
abort(404)
@app.route("/", methods=["GET", "POST"])
def fhost():
if request.method == "POST":
sf = None
secret = "secret" in request.form
if "file" in request.files:
try:
# Store the file with the requested expiration date
return store_file(
request.files["file"],
int(request.form["expires"]),
request.remote_addr,
request.user_agent.string,
secret
)
except ValueError:
# The requested expiration date wasn't properly formed
abort(400)
except KeyError:
# No expiration date was requested, store with the max lifespan
return store_file(
request.files["file"],
None,
request.remote_addr,
request.user_agent.string,
secret
)
elif "url" in request.form:
return store_url(
request.form["url"],
request.remote_addr,
request.user_agent.string,
secret
)
elif "shorten" in request.form:
return shorten(request.form["shorten"])
abort(400)
else:
return render_template("index.html")
@app.route("/robots.txt")
def robots():
return """User-agent: *
Disallow: /
"""
@app.errorhandler(400)
@app.errorhandler(401)
@app.errorhandler(404)
@app.errorhandler(411)
@app.errorhandler(413)
@app.errorhandler(414)
@app.errorhandler(415)
@app.errorhandler(451)
def ehandler(e):
try:
return render_template(f"{e.code}.html", id=id, request=request), e.code
except TemplateNotFound:
return "Segmentation fault\n", e.code
@app.cli.command("prune")
def prune():
"""
Clean up expired files
Deletes any files from the filesystem which have hit their expiration time. This
doesn't remove them from the database, only from the filesystem. It's recommended
that server owners run this command regularly, or set it up on a timer.
"""
current_time = time.time() * 1000;
# The path to where uploaded files are stored
storage = Path(app.config["FHOST_STORAGE_PATH"])
# A list of all files who've passed their expiration times
expired_files = File.query\
.where(
and_(
File.expiration.is_not(None),
File.expiration < current_time
)
)
files_removed = 0;
# For every expired file...
for file in expired_files:
# Log the file we're about to remove
file_name = file.getname()
file_hash = file.sha256
file_path = storage / file_hash
print(f"Removing expired file {file_name} [{file_hash}]")
# Remove it from the file system
try:
os.remove(file_path)
files_removed += 1;
except FileNotFoundError:
pass # If the file was already gone, we're good
except OSError as e:
print(e)
print(
"\n------------------------------------"
"Encountered an error while trying to remove file {file_path}. Double"
"check to make sure the server is configured correctly, permissions are"
"okay, and everything is ship shape, then try again.")
return;
# Finally, mark that the file was removed
file.expiration = None;
db.session.commit()
print(f"\nDone! {files_removed} file(s) removed")
""" For a file of a given size, determine the largest allowed lifespan of that file
Based on the current app's configuration: Specifically, the MAX_CONTENT_LENGTH, as well
as FHOST_{MIN,MAX}_EXPIRATION.
This lifespan may be shortened by a user's request, but no files should be allowed to
expire at a point after this number.
Value returned is a duration in milliseconds.
"""
def get_max_lifespan(filesize: int) -> int:
min_exp = app.config.get("FHOST_MIN_EXPIRATION", 30 * 24 * 60 * 60 * 1000)
max_exp = app.config.get("FHOST_MAX_EXPIRATION", 365 * 24 * 60 * 60 * 1000)
max_size = app.config.get("MAX_CONTENT_LENGTH", 256 * 1024 * 1024)
return min_exp + int((-max_exp + min_exp) * (filesize / max_size - 1) ** 3)
def do_vscan(f):
if f["path"].is_file():
with open(f["path"], "rb") as scanf:
try:
f["result"] = list(app.config["VSCAN_SOCKET"].instream(scanf).values())[0]
except:
f["result"] = ("SCAN FAILED", None)
else:
f["result"] = ("FILE NOT FOUND", None)
return f
@app.cli.command("vscan")
def vscan():
if not app.config["VSCAN_SOCKET"]:
print("""Error: Virus scanning enabled but no connection method specified.
Please set VSCAN_SOCKET.""")
sys.exit(1)
qp = Path(app.config["VSCAN_QUARANTINE_PATH"])
qp.mkdir(parents=True, exist_ok=True)
from multiprocessing import Pool
with Pool() as p:
if isinstance(app.config["VSCAN_INTERVAL"], datetime.timedelta):
scandate = datetime.datetime.now() - app.config["VSCAN_INTERVAL"]
res = File.query.filter(or_(File.last_vscan < scandate,
File.last_vscan == None),
File.removed == False)
else:
res = File.query.filter(File.last_vscan == None, File.removed == False)
work = [{"path" : f.getpath(), "name" : f.getname(), "id" : f.id} for f in res]
results = []
for i, r in enumerate(p.imap_unordered(do_vscan, work)):
if r["result"][0] != "OK":
print(f"{r['name']}: {r['result'][0]} {r['result'][1] or ''}")
found = False
if r["result"][0] == "FOUND":
if not r["result"][1] in app.config["VSCAN_IGNORE"]:
r["path"].rename(qp / r["name"])
found = True
results.append({
"id" : r["id"],
"last_vscan" : None if r["result"][0] == "SCAN FAILED" else datetime.datetime.now(),
"removed" : found})
db.session.bulk_update_mappings(File, results)
db.session.commit()
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