A daemon written in Go that accepts and rewrites email addresses according to the Sender Rewriting System.
The daemon listens on a Unix socket for requests to rewrite email addresses either for forwarding or in reverse for bounce handling.
The mileusna/srs package is used perform the rewriting.
From the source directory, run go build to produce a srsd executable.
srsd uses a JSON configuration file. A sample is provided as srsd.json. A default secret can be provided in addition to secrets for specific target SRS domains.
Secrets in the configuration file must be encoded using base64. 64 random bytes are recommended (used for an SHA-1 HMAC). Suitable secrets can be generated by running:
head -c64 /dev/urandom | base64 -w0
Start the daemon by running srsd.
By default, srsd will look for a configuration file named srsd.json in the
current directory and open a socket named srsd.sock in the current directory.
The socket will be created with access permissions set to 0770. To specify
different configuration file and socket locations, use the -config-file and
-socket-path options respectively. To specify different access permissions use
the -socket-access option. For example:
srsd -config-file /etc/srsd.conf -socket-path /run/srsd/srsd.sock -socket-access 0777
The process will remain running in the foreground when started. To terminate send the process an INT or TERM signal.
srsd accepts connections made to the Unix socket. Each connection can be used to
perform multiple operations (provided a syntax error is not encountered).
Rewrite commands are issued one per line (terminated with a line feed \n).
Requesting a forwarding rewrite for the sender address from@example.org using the SRS domain srs.example.com:
> Fsrs.example.com:from@example.org
< SRS0=PmRI=YB=example.org=from@srs.example.com
Requesting a reverse rewrite for the SRS address SRS0=PmRI=YB=example.org=from@srs.example.com:
> RSRS0=PmRI=YB=example.org=from@srs.example.com
< from@example.org
Errors will be reported prefixed with "ERROR: ":
> RSRS0=aaaa=YB=example.org=from@srs.example.com
< ERROR: Hash invalid in SRS address
> RSRS0=PmRI=aa=example.org=from@srs.example.com
< ERROR: Time stamp out of date
> Ffrom@example.org
< ERROR: Missing SRS domain or email address
The final error in the above example will result in the connection being closed due to the syntax error.
A systemd service file is provided as srsd.service.