Problem: I can’t set up an automated login (passwordless with ssh agent) to one of my servers.

Tip: Best way to debug SSH problems is by using ssh -vvvv server. The extra verbosity flags will tell you exactly what is going on at each interaction.

Details:
I was receiving the following code:
debug1: Trying private key: /Users/inderpreetsingh/.ssh/id_rsa
debug1: PEM_read_PrivateKey failed
debug1: read PEM private key done: type
debug3: Not a RSA1 key file /Users/inderpreetsingh/.ssh/id_rsa.
debug1: read PEM private key done: type RSA
Identity added: /Users/inderpreetsingh/.ssh/id_rsa (/Users/inderpreetsingh/.ssh/id_rsa)
debug1: read PEM private key done: type RSA
debug3: sign_and_send_pubkey
debug2: we sent a publickey packet, wait for reply
debug1: Authentications that can continue: publickey,password,hostbased
debug1: Trying private key: /Users/inderpreetsingh/.ssh/id_dsa
debug3: no such identity: /Users/inderpreetsingh/.ssh/id_dsa
debug2: we did not send a packet, disable method
debug3: authmethod_lookup password
debug3: remaining preferred: ,password
debug3: authmethod_is_enabled password
debug1: Next authentication method: password
inderpreetsingh@server's password:

Analysis: The errors are misleading. They seem to indicate that the identity file on our own machine is the culprit. But the problem was the .ssh directory and the authorized_keys file permissions. They may be too lax or too restrictive.

Fix: From your home directory, fire the following permissions:

chmod 700 ~/.ssh
chmod 600 ~/.ssh/authorized_keys

And for good measure, make sure you alone own the files:

chown username:username ~/.ssh
chown username:username ~/.ssh/authorized_keys

And passwordless SSH here I come.