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Date:      Sat, 3 Oct 2015 10:28:06 -0700
From:      Bryan Drewery <bdrewery@FreeBSD.org>
To:        "Simon J. Gerraty" <sjg@juniper.net>
Cc:        Jilles Tjoelker <jilles@stack.nl>, freebsd-arch@freebsd.org
Subject:   Re: login -f changing session getlogin(2)
Message-ID:  <56101026.7060206@FreeBSD.org>
In-Reply-To: <28007.1443892369@chaos>
References:  <560D826D.7000302@FreeBSD.org> <20151001203436.GA22737@stack.nl> <560DAD6D.7050007@FreeBSD.org> <28007.1443892369@chaos>

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On 10/3/2015 10:12 AM, Simon J. Gerraty wrote:
> Hi Bryan
>=20
>>>> It makes me wonder if there's bigger architectural issues here that =
need
>>>> addressing with session and login. Perhaps login -f is just a specia=
l
>>>> case though.
>=20
> As others have indicated your use of 'login -f' is "unexpected".
>=20
>> Well, none of that is documented or its use discouraged. It has been
>=20
> People document what they expect others need to know - and that is
> framed by their own expectations of usage.
> Thus lack of a documented admonition against every possible usage, does=

> not constitute a guarantee of support.
>=20
> When eventually someone uses something in an "unexpected" way,
> and encounters problems, there are basically three options.
>=20
> 1/ document that that should not be done, or that problems may arise
>=20
> 2/ prevent it being done
>=20
> 3/ make it work
>=20
>> And actually, 'su -l' NOT calling setlogin(2) is another surprise. I
>> have used 'login -f' precisely because it simulates a real login and
>> sets up the environment as the user. If I am dropping into a user's
>> shell I expect things like 'mail' to have their FROM not root or
>> wherever I came from in my session.
>=20
> Masquerading as another user to that extent, sounds somewhat disturbing=

> actually, and not something that should really be optimized for.
>=20
> So I'd guess in this case that #1 is the correct option.
>=20

This still ignores that 'su -l' does the opposite.

Sometimes sysadmins need to masquerade as users for support. Having a
user hand over their SSH password, or adding a password to a service
user that should NOT have remote access, is not the answer.  There needs
to be a way to login fully as a user for debugging issues as that user.

--=20
Regards,
Bryan Drewery


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