Convert single line RSA private ssh key to multi line

Question

I have these private keys that have been converted to single line equivalent.

These keys are quite a lot.

So I decided to invest some time to write a script to convert.

This has not yielded to much.

-----BEGIN RSA PRIVATE KEY----pEdInVAbH4d0PH4=pEdInVAbH4d0PH4=pEdInVAbH4d0PH4=pEdInVAbH4d0PH4= pEdInVAbH4d0PH4=pEdInVAbH4d0PH4=pEdInVAbH4d0PH4=pEdInVAbH4d0PH4= pEdInVAbH4d0PH4=pEdInVAbH4d0PH4=pEdInVAbH4d0PH4=pEdInVAbH4d0PH4= pEdInVAbH4d0PH4=pEdInVAbH4d0PH4=pEdInVAbH4d0PH4=pEdInVAbH4d0PH4= pEdInVAbH4d0PH4=pEdInVAbH4d0PH4=pEdInVAbH4d0PH4=pEdInVAbH4d0PH4= -----END RSA PRIVATE KEY-----

I am using echo ~/.ssh/id_rsa | tr " " "\n"

This returns:

-----BEGIN 
RSA 
PRIVATE 
KEY----- 
pEdInVAbH4d0PH4=pEdInVAbH4d0PH4=pEdInVAbH4d0PH4=pEdInVAbH4d0PH4=
pEdInVAbH4d0PH4=pEdInVAbH4d0PH4=pEdInVAbH4d0PH4=pEdInVAbH4d0PH4=
pEdInVAbH4d0PH4=pEdInVAbH4d0PH4=pEdInVAbH4d0PH4=pEdInVAbH4d0PH4=
pEdInVAbH4d0PH4=pEdInVAbH4d0PH4=pEdInVAbH4d0PH4=pEdInVAbH4d0PH4=
pEdInVAbH4d0PH4=pEdInVAbH4d0PH4=pEdInVAbH4d0PH4=pEdInVAbH4d0PH4=
-----END
RSA
PRIVATE
KEY-----

I have been trying to figure out the best possible way to get this back to the right format.

Answer 1

Assuming a standard RSA private key that just had the newlines removed, a couple of sed replacements will get you back to the original format:

sed -e "s/-----BEGIN RSA PRIVATE KEY-----/&\n/"\
    -e "s/-----END RSA PRIVATE KEY-----/\n&/"\
    -e "s/\S\{64\}/&\n/g"\
    ~/.ssh/id_rsa

The standard key format requires the BEGIN and END statements to be on a separate line, and the base64-encoded key to be formatted at 64 columns. The above command will get you there.

Answer 2

@robby Thanks from your answer I adapted the following which worked for me.

sed -e "s/-----BEGIN RSA PRIVATE KEY-----/&\n/" -e "s/\S\{64\}/&\n/g" | sed "s/^\s//g" ~/.ssh/id_rsa

Answer 3

I adapted the solution to ed25519 algorithm to talk to Gitlab via SSH. Thanks @Robby!

RUN sed -i -e "s/-----BEGIN OPENSSH PRIVATE KEY-----/&\n/"\
    -e "s/-----END OPENSSH PRIVATE KEY-----/\n&/"\
    -e "s/\S\{70\}/&\n/g"\
    /root/.ssh/id_ed25519

Input

-----BEGIN OPENSSH PRIVATE KEY----- XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX== -----END OPENSSH PRIVATE 
KEY-----

Output

-----BEGIN OPENSSH PRIVATE KEY-----
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX==
-----END OPENSSH PRIVATE KEY-----