Archive discontinued selective SRS implementation

2026-10-20 14:41:48 +02:00
parent 3af1c29a16
commit 39b933b798
25 changed files with 488 additions and 0 deletions
@@ -0,0 +1,113 @@
+#!/usr/bin/env python3
+
+import socket
+import sys
+
+SRS_DOMAIN = "srs.warenform.de"
+SOCKET_HOST = "127.0.0.1"
+SOCKET_PORT = 10003
+TIMEOUT = 5
+MAX_RESPONSE = 4096
+
+
+def read_netstring(sock):
+    length_bytes = bytearray()
+
+    while True:
+        char = sock.recv(1)
+        if not char:
+            raise ValueError("Incomplete netstring length")
+        if char == b":":
+            break
+        if char < b"0" or char > b"9" or len(length_bytes) >= 8:
+            raise ValueError("Invalid netstring length")
+        length_bytes.extend(char)
+
+    if not length_bytes:
+        raise ValueError("Empty netstring length")
+
+    length = int(length_bytes)
+
+    if length > MAX_RESPONSE:
+        raise ValueError("Netstring response too large")
+
+    data = bytearray()
+
+    while len(data) < length + 1:
+        chunk = sock.recv(length + 1 - len(data))
+        if not chunk:
+            raise ValueError("Incomplete netstring response")
+        data.extend(chunk)
+
+    if data[-1:] != b",":
+        raise ValueError("Invalid netstring terminator")
+
+    return bytes(data[:-1]).decode("utf-8")
+
+
+def verify_srs(address):
+    request = f"reverse {address}".encode("utf-8")
+    packet = str(len(request)).encode("ascii") + b":" + request + b","
+
+    with socket.create_connection(
+        (SOCKET_HOST, SOCKET_PORT), timeout=TIMEOUT
+    ) as sock:
+        sock.settimeout(TIMEOUT)
+        sock.sendall(packet)
+        response = read_netstring(sock)
+
+    if response.startswith("OK "):
+        original = response[3:]
+        if not original or "@" not in original:
+            raise ValueError("Invalid reverse result")
+        return "OK"
+
+    if response.startswith("NOTFOUND "):
+        return "REJECT 550 5.1.1 Invalid SRS address"
+
+    raise ValueError(f"Unexpected socketmap response: {response}")
+
+
+def check_recipient(recipient):
+    if "@" not in recipient:
+        return "DUNNO"
+
+    localpart, domain = recipient.rsplit("@", 1)
+
+    if domain.lower() != SRS_DOMAIN:
+        return "DUNNO"
+
+    if not localpart.upper().startswith(("SRS0=", "SRS1=")):
+        return "REJECT 550 5.1.1 Invalid SRS address"
+
+    try:
+        return verify_srs(recipient)
+    except (OSError, UnicodeError, ValueError) as exc:
+        print(f"SRS verification error: {exc}", file=sys.stderr)
+        return "DEFER 451 4.3.0 SRS verification unavailable"
+
+
+def main():
+    while True:
+        attributes = {}
+
+        for line in sys.stdin:
+            line = line.rstrip("\r\n")
+
+            if not line:
+                break
+
+            if "=" in line:
+                key, value = line.split("=", 1)
+                attributes[key] = value
+        else:
+            return
+
+        recipient = attributes.get("recipient", "")
+        action = check_recipient(recipient)
+
+        print(f"action={action}\n", flush=True)
+
+
+if __name__ == "__main__":
+    main()