[OpenWrt-Devel] [LEDE-DEV] [PATCH v1 1/1] openssh: disable passwords for openssh server

Yousong Zhou yszhou4tech at gmail.com
Wed Feb 14 03:06:11 EST 2018

On 14 February 2018 at 11:53, Philip Prindeville
<philipp_subx at redfish-solutions.com> wrote:
>> On Feb 11, 2018, at 3:54 AM, Yousong Zhou <yszhou4tech at gmail.com> wrote:
>> On 9 February 2018 at 08:28, Philip Prindeville
>> <philipp at redfish-solutions.com> wrote:
>>> From: Philip Prindeville <philipp at redfish-solutions.com>
>>> Allowing password logins leaves you vulnerable to dictionary
>>> attacks.  We disable password-based authentication, limiting
>>> authentication to keys only which are more secure.
>>> Note: You'll need to pre-populate your image with some initial
>>> keys. To do this:
>>> 1. Create the appropriate directory as "mkdir -p files/root/.ssh"
>>>   from your top-level directory;
>>> 2. Copy your "~/.ssh/id_rsa.pub" (or as appropriate) into
>>>   "files/root/.ssh/authorized_keys" and indeed, you can collect
>>>   keys from several sources this way by concatenating them;
>>> 3. Set the permissions on "authorized_keys" to 644 or 640.
>> If forgetting doing this means I may need physical connection like vga
>> monitor or serial connection to "unlock" the device, very likely I
>> will hate this security enforcement...  It's just the inconvenience
>> regardless of whether the said situation should happen.  As a user I'd
>> like to keep this level of convenience as using password
>> authentication and turn it off when I see it appropriate.
>>                yousong
> Well, we’re at an impasse because some people have said “this should be the new norm and it’s a mistake not to disable it unconditionally” and others have said the opposite, “yes, okay, let’s do this but only as an option”.
> So I’m happy to go other way but we should reach a consensus.
> What if it *is* an option but depends on a virtual package that takes a value (like CONFIG_SSH_PUBLIC_KEYS) and squirts that into the /root/.ssh/authorized_keys file.
> Would that work for everyone?
> You could still lock yourself out of a box by (a) mis-formatting the keys or (b) getting the wrong public keys that don’t match your installed private keys, but getting this to be absolutely foolproof is a fool's errand.
> So what constitutes “good enough”?
> -Philip

No, it's just complicating things up.  When people really cares about
the default settings' security, the will override the default by also
specifying files/etc/ssh/sshd_config besides
files/root/.ssh/authorized_keys.  No need to pass on such complexity
as virtual packages and another config options for others.

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