Add SRS implementation - scripts and configuration files.

files/srs/srs-reverse-map.py

@@ -0,0 +1,112 @@
+#!/usr/bin/python3
+
+import socket
+import socketserver
+
+LISTEN_HOST = "127.0.0.1"
+LISTEN_PORT = 10004
+SRS_HOST = "127.0.0.1"
+SRS_PORT = 10003
+SRS_DOMAIN = "srs.warenform.de"
+
+MAX_REQUEST = 8192
+TIMEOUT = 3
+
+
+def read_netstring(sock):
+    length = bytearray()
+
+    while True:
+        c = sock.recv(1)
+        if not c:
+            raise EOFError()
+        if c == b":":
+            break
+        if not c.isdigit() or len(length) >= 8:
+            raise ValueError("Invalid netstring length")
+        length.extend(c)
+
+    if not length:
+        raise ValueError("Empty netstring length")
+
+    size = int(length)
+    if size > MAX_REQUEST:
+        raise ValueError("Netstring too large")
+
+    data = bytearray()
+    while len(data) < size:
+        chunk = sock.recv(size - len(data))
+        if not chunk:
+            raise EOFError()
+        data.extend(chunk)
+
+    if sock.recv(1) != b",":
+        raise ValueError("Invalid netstring terminator")
+
+    return bytes(data)
+
+
+def netstring(data):
+    return str(len(data)).encode() + b":" + data + b","
+
+
+class Handler(socketserver.BaseRequestHandler):
+    def handle(self):
+        self.request.settimeout(TIMEOUT)
+
+        while True:
+            try:
+                request = read_netstring(self.request)
+            except (EOFError, OSError):
+                return
+            except ValueError:
+                self.request.sendall(netstring(b"PERM Invalid request"))
+                return
+
+            try:
+                operation, address = request.decode("utf-8").split(" ", 1)
+            except (UnicodeError, ValueError):
+                self.request.sendall(netstring(b"PERM Invalid request"))
+                continue
+
+            if operation != "reverse":
+                self.request.sendall(netstring(b"NOTFOUND "))
+                continue
+
+            if "@" not in address:
+                self.request.sendall(netstring(b"NOTFOUND "))
+                continue
+
+            domain = address.rsplit("@", 1)[1].lower()
+
+            if domain != SRS_DOMAIN:
+                self.request.sendall(netstring(b"NOTFOUND "))
+                continue
+
+            try:
+                with socket.create_connection(
+                    (SRS_HOST, SRS_PORT), timeout=TIMEOUT
+                ) as upstream:
+                    upstream.settimeout(TIMEOUT)
+                    upstream.sendall(netstring(request))
+                    response = read_netstring(upstream)
+
+                if response.startswith((b"OK ", b"NOTFOUND ", b"TEMP ", b"PERM ")):
+                    result = response
+                else:
+                    result = b"TEMP Invalid upstream response"
+
+            except (OSError, EOFError, ValueError):
+                result = b"TEMP SRS backend unavailable"
+
+            self.request.sendall(netstring(result))
+
+
+class Server(socketserver.ThreadingTCPServer):
+    allow_reuse_address = True
+    daemon_threads = True
+
+
+if __name__ == "__main__":
+    with Server((LISTEN_HOST, LISTEN_PORT), Handler) as server:
+        server.serve_forever()