Prototype working

server.py

@@ -0,0 +1,46 @@
+#!/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+-_]+=*$')
+
+@app.route('/<file_id>/<token>/<filename>')
+def download(file_id, token, filename):
+    if not BASE64_RE.match(file_id) or len(file_id) != filecrypt.FILE_ID_LENGTH:
+        abort(400, 'Invalid file ID format')
+    if not BASE64_RE.match(token) or len(token) != filecrypt.TOKEN_LENGTH:
+        abort(400, 'Invalid token format')
+
+    path = f'{file_id}.enc'
+    size = filecrypt.payload_size(path)
+
+    range_header = re.match('^bytes=([0-9]+)-([0-9]*)$', request.headers.get('Range', ''))
+    if not range_header:
+        response = Response(
+                filecrypt.decrypt_generator(path, token),
+                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)
+
+        response = Response(
+                filecrypt.decrypt_generator(path, token, seek=range_start, end=range_end),
+                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
+