OS X has a command line tool called security that is made for working with keychains. The man page has examples of how to export all items of a specific type / all items for a specific keychain - but I don't understand how to export / import a single item.
What I would really like to do is update the password on a single IPSec XAuth Password
item but I think maybe exporting, possibly deleting, then importing would be the closest thing to what I want.
I haven't had any luck finding examples or related questions for this task, and I've not used the security
tool other than to list available keychains.