Bug#420829: ssh-add: please check file type and test if it's actually a [private] key

[Justin Pryzby <justinpryzby@users.sourceforge.net>]

Package: openssh-client
Version: 1:4.3p2-9
Severity: normal

Please test the filetype and content before warning and prompting.

Ideally you could strip off the conventional .pub if you find the public
key component.

ssh-add /tmp
Enter passphrase for /tmp: 
Bad passphrase, try again for /tmp: 

ssh-add .ssh/id_rsa.pub
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
@         WARNING: UNPROTECTED PRIVATE KEY FILE!          @