@attachments should allow sprintf values

[wiibaa]

As found by a user https://discuss.elastic.co/t/dynamic-attachments-to-email-output/41559

the @attachments configuration does not compute sprintf values, this is obvious when looking at the code
https://github.com/logstash-plugins/logstash-output-email/blob/v3.0.2/lib/logstash/outputs/email.rb#L135-L137

Current mail.add_file(fileLocation) should become mail.add_file(event.sprintf(fileLocation))

This needs (maybe my own reminder if I found time for a PR)

• Fix
• Test
• Documentation update

[jstoja]

I'm not sure it's something wanted. @jsvd Any idea if the feature would fit into the vision of the output?

[jsvd]

I'm a bit on the fence of allowing this field to be sprintfed...basically means "here's an event with a path, read that path and send it to me"

If one would craft an event with the path "~/.ssh/ssh_key" or similar you'd send an email with credentials :)

[jsvd]

closing this as I believe this feature could be misused and abused very easily.