Add selective Postfix SRS installation and management

files/srs/srs-forward.py

@@ -0,0 +1,177 @@
+#!/usr/bin/python3
+
+import smtplib
+import subprocess
+import sys
+
+SMTP_HOST = "127.0.0.1"
+SMTP_PORT = 10028
+
+DECISION_SCRIPT = "/usr/local/sbin/srs-alias-decision.py"
+SRS_MAP = "socketmap:inet:127.0.0.1:10003:forward"
+
+EX_TEMPFAIL = 75
+EX_UNAVAILABLE = 69
+
+
+def run_command(args):
+    result = subprocess.run(
+        args,
+        capture_output=True,
+        text=True,
+        timeout=30
+    )
+
+    if result.returncode != 0:
+        raise RuntimeError(
+            result.stderr.strip()
+            or result.stdout.strip()
+            or f"Exit-Code {result.returncode}"
+        )
+
+    return result.stdout.strip()
+
+
+def determine_sender(sender, recipient, original_recipient):
+    decision = run_command([
+        DECISION_SCRIPT,
+        sender,
+        recipient,
+        original_recipient
+    ])
+
+    if decision.startswith("NO_SRS:"):
+        return sender
+
+    if not decision.startswith("SRS:"):
+        raise RuntimeError(
+            f"Keine eindeutige SRS-Entscheidung: {decision}"
+        )
+
+    rewritten_sender = run_command([
+        "/usr/sbin/postmap",
+        "-q",
+        sender,
+        SRS_MAP
+    ])
+
+    if not rewritten_sender:
+        raise RuntimeError("PostSRSd lieferte keinen Absender")
+
+    if not rewritten_sender.lower().endswith("@srs.warenform.de"):
+        raise RuntimeError(
+            f"Unerwartete SRS-Domain: {rewritten_sender}"
+        )
+
+    if not rewritten_sender.upper().startswith(("SRS0=", "SRS1=")):
+        raise RuntimeError(
+            f"Ungueltige SRS-Adresse: {rewritten_sender}"
+        )
+
+    return rewritten_sender
+
+
+def main():
+    if len(sys.argv) not in (5, 6):
+        print(
+            "Aufruf: srs-forward.py "
+            "sender recipient original_recipient queue_id [envid]",
+            file=sys.stderr
+        )
+        return EX_TEMPFAIL
+
+    sender, recipient, original_recipient, queue_id = sys.argv[1:5]
+    envid = sys.argv[5] if len(sys.argv) == 6 else ""
+
+    if envid.startswith("envid="):
+        envid = envid[len("envid="):]
+
+    try:
+        envelope_sender = determine_sender(
+            sender,
+            recipient,
+            original_recipient
+        )
+
+        message = sys.stdin.buffer.read()
+
+        with smtplib.SMTP(
+            SMTP_HOST,
+            SMTP_PORT,
+            timeout=30
+        ) as smtp:
+            smtp.ehlo()
+
+            mail_options = []
+            rcpt_options = []
+
+            if envid:
+                if not smtp.has_extn("dsn"):
+                    raise RuntimeError(
+                        "SMTP-Ziel unterstuetzt kein DSN/ENVID"
+                    )
+                mail_options.append(f"ENVID={envid}")
+
+            if original_recipient and smtp.has_extn("dsn"):
+                rcpt_options.append(
+                    f"ORCPT=rfc822;{original_recipient}"
+                )
+
+            smtp.sendmail(
+                envelope_sender,
+                [recipient],
+                message,
+                mail_options=mail_options,
+                rcpt_options=rcpt_options
+            )
+
+    except smtplib.SMTPRecipientsRefused as exc:
+        codes = [
+            code
+            for code, response in exc.recipients.values()
+        ]
+
+        permanent = bool(codes) and all(
+            500 <= code < 600 for code in codes
+        )
+
+        result = EX_UNAVAILABLE if permanent else EX_TEMPFAIL
+        enhanced_status = "5.0.0" if permanent else "4.0.0"
+
+        print(
+            f"{enhanced_status} SRS queue_id={queue_id}: "
+            f"SMTP-Empfaengerablehnung: {exc.recipients!r}",
+            file=sys.stderr
+        )
+        return result
+
+    except smtplib.SMTPResponseException as exc:
+        code = exc.smtp_code
+        result = EX_UNAVAILABLE if 500 <= code < 600 else EX_TEMPFAIL
+
+        enhanced_status = "5.0.0" if result == EX_UNAVAILABLE else "4.0.0"
+
+        print(
+            f"{enhanced_status} SRS queue_id={queue_id}: "
+            f"SMTP {code}: {exc.smtp_error!r}",
+            file=sys.stderr
+        )
+        return result
+
+    except (
+        subprocess.TimeoutExpired,
+        RuntimeError,
+        smtplib.SMTPException,
+        OSError
+    ) as exc:
+        print(
+            f"SRS queue_id={queue_id}: temporaerer Fehler: {exc}",
+            file=sys.stderr
+        )
+        return EX_TEMPFAIL
+
+    return 0
+
+
+if __name__ == "__main__":
+    sys.exit(main())