First working version: allows downloading binaries

.gitignore

+__pycache__
+*.key
+.env

gakeshadeba.py

+# Gakeshadeba – Simple ShaCache and ShaDir implementation in plain Python
+
+import hashlib
+import json
+import os
+
+from base64 import b64encode, b64decode
+from OpenSSL import crypto
+
+class Gakeshadeba():
+    def __init__(self, content_dir, sr_file):
+        self.content_dir = content_dir
+        self.sr_file = sr_file
+
+        self.sr_md5_dir = {}
+        self.file_sha512_dir = {}
+
+        self.key = None
+
+    def set_signing_key(self, key_file_name):
+        with open(key_file_name) as key_file:
+           self.key = crypto.load_privatekey(crypto.FILETYPE_PEM, key_file.read())
+
+    def build_sr_dir(self):
+        r_file_sha512_dir = dict([reversed(i) for i in self.file_sha512_dir.items()])
+
+        sr_file_handle = open(self.sr_file, "r")
+        sr_file_json = sr_file_handle.read()
+        sr_file_content = json.loads(sr_file_json)
+
+        for sr_el in sr_file_content:
+            sr = sr_el["software_release"]
+            file = sr_el["cache_file"]
+            sr_md5 = hashlib.md5(sr.encode("utf8"))
+            file_sha512 = r_file_sha512_dir.get(file)
+
+            if file_sha512:
+                entry = {
+                    "sha512": file_sha512,
+                    "software_url": sr,
+                    # Should be flexible
+                    "software_root": sr_el["software_root"],
+                    "multiarch": sr_el["multiarch"],
+                    "os": sr_el["os"],
+                    # Useless fields, don't ask.
+                    "file": "file",
+                    "urlmd5": "urlmd5",
+                }
+                entry_json = json.dumps(entry)
+                entry_signature = b64encode(crypto.sign(self.key, entry_json, "sha1")).decode()
+                self.sr_md5_dir[sr_md5.hexdigest()] = [entry_json, entry_signature]
+
+    def build_file_cache(self):
+        for file_name in os.listdir(self.content_dir):
+            fullpath = os.path.join(self.content_dir, file_name)
+            sha512 = hashlib.sha512()
+
+            with open(fullpath, "rb") as handle:
+                for chunk in iter(lambda: handle.read(4096), b""):
+                    sha512.update(chunk)
+
+            self.file_sha512_dir[sha512.hexdigest()] = file_name
+
+    def serve_sr_dir_entry(self, md5):
+        dir_content = self.sr_md5_dir.get(md5)
+
+        if dir_content:
+            return json.dumps([self.sr_md5_dir[md5]])
+        else:
+            return None
+
+    def find_file_cache_entry(self, sha512):
+        file_name = self.file_sha512_dir.get(sha512)
+        if file_name:
+            return file_name
+        else:
+            return None
+

server.py

+from flask import Flask, send_from_directory
+from gakeshadeba import Gakeshadeba
+
+content_dir = "./files"
+
+gsha = Gakeshadeba("./files", "./sr_list.json")
+gsha.set_signing_key("tmp.key")
+gsha.build_file_cache()
+gsha.build_sr_dir()
+
+app = Flask(__name__)
+
+@app.route("/bdir/<md5>")
+def binary_dir(md5):
+    return gsha.serve_sr_dir_entry(md5)
+
+@app.route("/bcache/<sha512>")
+def binary_cache(sha512):
+    file_name = gsha.find_file_cache_entry(sha512)
+    if file_name is None:
+        return "Not found\n", 404
+
+    return send_from_directory(content_dir, file_name, as_attachment=True)
+