please remove permission check that disallows private-group access.

[Dr. Nagy Elemér Kár oly]

Dear Uri,

> Respectfully disagree with your risk-benefit conclusion, and concur with the request to remove this check or 
> modify it to be informative rather than blocking.
I respectfully disagree with you. I am a SSH user (and not an SSH developer) and I find that warning rather useful as it 
helped me a few times out of a thousand setups when I either forgot something or was using imperfect automation tools. I 
want SSH to check it, I would patch it back on my own time if it was removed.

As a matter of fact, I would like that check to be even stronger and check for ACLs as well...

On the other hand, I would support changing the wording from "bad permissions" to "insecure permissions" and "too open" 
to "most probably insecure" as I feel it is more technical and probably more PC as well.

Also, I would support a patch that adds an "ignore-insecure-permissions" option to both the SSH client and the server, 
so you could set up one-user/one-shot/QaD test (virtual) machines with less hassle.

Best wishes:
Elmar

> > We don't plan to remove this check. Accidental key exposure is still an
> > unfortunately common problem and, while this check isn't perfect, I'm
> > pretty sure that it avoids enough real-world misconfiguration to
> > justify it's continued existence.
> > 
> > You're right that it doesn't withstand a determined administrator
> > and that's fine too - it isn't supposed to.
> > 
> > -d
> > 
> >> On Fri, 19 Oct 2018, L A Walsh wrote:
> >> 
> >> Third party programs should not be dictating to users how
> >> to manage their systems.  Things like:
> >> 
> >> @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
> >> @         WARNING: UNPROTECTED PRIVATE KEY FILE!          @
> >> @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
> >> Permissions 0660 for '/Users/law.Bliss/.ssh/id_rsa' are too open.
> >> It is required that your private key files are NOT accessible by others
> >> This private key will be ignored.
> >> Load key "/Users/law.Bliss/.ssh/id_rsa": bad permissions
> >> 
> >> 1) how would you know if they are "too open".  I assign a group to
> >> each user.  How would they claim my permissions are "bad". 
> >> 2) In this specific  case, my local-machine and domain login
> >> are different UID's, so I put them in the same GID to allow
> >> access no matter UID I am logged in with. 
> >> 3) It may give some users a false sense of "security" if they believe
> >> that setting perms to something like 0600 will give them the security of
> >> only their 1 login having access.  They had better not rely on that.
> >> 
> >> 4) I no longer get the warning -- I can simple change the permission
> >> bits to match what is wanted then add my group as an acl -- which
> >> gives the group full access but circumvents the irrelevant warning.
> >> 
> >> 5) since my home directory is exported and mountable via samba, anyone
> >> in the administrators or Domain Admins group (among others) can read it
> >> as well.
> >> 
> >> 6) I.e. the warning message is outdated, inaccurate and not really needed.
> >> 
> >> Thanks much!
> >> -linda