Strange that .ssh/authorized_keys will not work if it is a chmod of 664?

I开发者_运维知识库 was trying to set up automatic log in using ssh, but it didn't work, and saw the file as

rw-rw-r--

on the server, so it is 664. But it can't automatic log in, until I chmod to 600 for it, and then all of a sudden, it can automatic log in. Is there a requirement that says it must be 600 for it to work?

644 is fine too. It just can't be group and/or other writable.

Setting StrictModes no in sshd_config will remove this restriction. But it's not recommended.