MacOS – Keychain: how to set expiration time to `Internet password`

I'm not sure how to prevent the creation of the credentials in the first place, but you can remove items from the Keychain using the security command, which is easily scriptable.

The command you want is security delete-internet-password -s server, where server is the hostname or address of the proxy server without the protocol (i.e. 192.168.0.1, not https://192.168.0.1). Alternatively you can use -l label to match the name of the keychain item, or various other search parameters, which you can find detailed on the man page.

You can have this command run at logout for each user by saving it as an executable script in a location readable by all users (make sure the file is executable for all users as well). Then run sudo defaults write com.apple.loginwindow LogoutHook /path/to/script.

That is many questions all in one. In order to manage our search engine, we prefer to have 1 question at the time.

1) I'd prefer Chrome to save the credentials in its own storage, instead sharing one with Safari. 2) If not, I'd rather it to not ask me about that. 3) Failing that, it should at least give me the right credentials.

To prevent the pop up is done with granting the Access Control in the key-chain.

Here is a sample:

Open the relevant key chain item and click on access control.

Add and allow Google Chrome to use it.