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#!/usr/bin/env python3
import re
import os
from flask import Flask, abort, request, Response
import filecrypt
app = Flask(__name__)
BASE64_RE = re.compile('^[A-Za-z0-9+-_]+=*$')
@app.route('/<file_id>/<token>/<filename>')
def download(file_id, token, filename):
if not BASE64_RE.match(file_id) or len(file_id) != filecrypt.FILE_ID_LENGTH:
abort(400, 'Invalid file ID format')
if not BASE64_RE.match(token) or len(token) != filecrypt.TOKEN_LENGTH:
abort(400, 'Invalid token format')
path = f'{file_id}.enc'
if not os.path.isfile(path):
abort(403) # forbidden
size = filecrypt.payload_size(path)
range_header = re.match('^bytes=([0-9]+)-([0-9]*)$', request.headers.get('Range', ''))
if not range_header:
try:
generator = filecrypt.decrypt_generator(path, filename, token)
except ValueError: # MAC check failed
abort(403) # forbidden
response = Response(generator, mimetype='application/octet-stream')
response.headers['Content-Length'] = size
else:
range_start, range_end = range_header.groups()
range_start = int(range_start)
range_end = int(range_end) if range_end else size-1
if range_start < 0 or range_end >= size or range_start >= range_end:
abort(416) # range not satisfiable
try:
generator = filecrypt.decrypt_generator(path, filename, token, seek=range_start, end=range_end)
except ValueError: # MAC check failed
abort(403) # forbidden
response = Response(generator, status=206, mimetype='application/octet-stream')
response.headers['Content-Range'] = f'bytes {range_start}-{range_end}/{size}'
response.headers['Content-Length'] = range_end - range_start + 1
response.headers['Accept-Ranges'] = 'bytes'
response.headers['Content-Disposition'] = f'attachment {filename}'
return response
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