Fixes the generation of keys on systems with newer OpenSSH versions (>= 7.8)

[danielrs]

The OpenSSH release:

https://www.openssh.com/txt/release-7.8

Changes the default format when generating private keys, this pull requests fixes that by letting the users on systems with newer OpenSSH versions specify if they want to use the old PEM format by passing the flag --use-pem to the generate-keys.sh script.

#23

[pivotal-issuemaster]

@danielrs Please sign the Contributor License Agreement!

Click here to manually synchronize the status of this Pull Request.

See the FAQ for frequently asked questions.

[pivotal-issuemaster]

@danielrs Thank you for signing the Contributor License Agreement!

[ahaczewski]

Wouldn't it be possible to detect ssh version and then check whether it is greater than 7.8?

Like

verle() {
    [  "$1" = "`echo -e "$1\n$2" | sort -V | head -n1`" ]
}
sshver=`ssh -V 2>&1 | cut -d, -f1 | cut -d' ' -f1 | cut -d_ -f2`
param=`verle 7.8 $sshver && echo "-m PEM" || echo ""`

[larssb]

Let's get this in :-). Would be great as newcomers would then not bump their heads into this issue.

Thnx

[vito]

Happy to merge this in since the problem seems to be particular acute for new users. Auto-detecting it and/or implementing the key generation stuff mentioned in concourse/docs#124 would be better IMO but for now, documenting it is better than nothing.

Thanks!