ssh won't connect with too many permissions
 

I connect through ssh (putty) using a user authentication public key stored on the ssh server in ~/.ssh/authorized_keys. Permissions for ~ are 750. When I change them to 757 I can't connect anymore - connection by key is not accepted by server. How is this possible?

it's possible because that's the way it works. that data is PRIVATE and you're making ANYONE able to read it. So another user could trivially add a key to YOUR config and login as you. Why would you want to change it in the first place??

You say that sshd checks the permissions for the home directory where ~/.ssh/authorized_keys is stored? The permissions for ~/.ssh are still 700, and for authorized_keys are 644 (read for everbody, write for owner).

I did this stupid thing while trying to make local mail work, but now it works with the right permissions. Anyway, are you sure that sshd is checking the permissions of the ~ directory? I did not expect this behaviour.

Thank you for your answer.

OpenSSH
 

Yes, it checks the permissions on your home folder.

Check out the man page.

Yes. It's enabled by default (StrictModes), and this is a good thing.