I have a bunch of users, who with SSH keys have access to accounts on other servers. Currently I have a script which collects up the ssh public keys and distributes them to the correct account on the correct servers.

What I want to do, is get that script to check that any given users ssh key has a passphrase before accepting the public key and distributing it.

I've tried a number of things, like using an ssh-agent and ssh-add and then the problem comes when ssh-add gets asked for passphrase.

Is there a way to get something like openssl to check for passphrase, fail slightly with a return code of 1 if the key has a passphrase?


  • Could you clarify whether the requirement is to have a passphrase or not to have it - and because of what reasons?
    – user1686
    Oct 19 '10 at 13:13
  • grawity: My requirement is to make sure users have set passphrases on their ssh keys, only keys with passphrases will get distributed to the other servers. Oct 19 '10 at 13:39

If a keyfile uses a passphrase it has "Proc-Type:" attribute set with the word "ENCRYPTED" appended.

So, you can determine if a keyfile uses passphrase by running it through find and grep to see if it has the string 'ENCRYPTED'.

# list keyfiles that USE a passphrase
HOMES=/home /mnt/nfs_home
find $HOMES -maxdepth 3 -type f -path '*/.ssh/id* -name "id_[dr]sa*" -exec grep -q "ENCRYPTED" {} \; -print

prints a list of files that have passphrases. Then you can match those against a list of all keyfiles to single out those that doesn't use a passphrase. A list of all keyfiles can be obtained e.g. by leaving the -exec parameter out, as follows:

# list all keyfiles
HOMES=/home /mnt/nfs_home
find $HOMES -maxdepth 3 -type f -path '*/.ssh/id* -name "id_[dr]sa*" -print
  • 2
    No longer possible with new SSH key format, the Proc-Type header is not written to the file, despite being encrypted.
    – Oneiroi
    Aug 2 '19 at 14:29

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.