From: Fabian Stelzer <fs@gigacodes.de>
To: Damien Miller <djm@mindrot.org>
Cc: Jeff King <peff@peff.net>,
Johannes Schindelin via GitGitGadget <gitgitgadget@gmail.com>,
git@vger.kernel.org,
Johannes Schindelin <johannes.schindelin@gmx.de>,
pedro martelletto <pedro@yubico.com>,
Junio C Hamano <gitster@pobox.com>
Subject: Re: [PATCH] gpg-interface: trim CR from ssh-keygen -Y find-principals
Date: Mon, 6 Dec 2021 09:39:25 +0100 [thread overview]
Message-ID: <20211206083925.tuy2w3wzlgpc36bj@fs> (raw)
In-Reply-To: <70cee773-9547-e3cf-9327-ac0213d327e@mindrot.org>
On 06.12.2021 10:06, Damien Miller wrote:
>On Sat, 4 Dec 2021, Fabian Stelzer wrote:
>
>> > I'm guessing probably not, but when it comes to something with security
>> > implications like this, it pays to be extra careful. I'm hoping somebody
>> > familiar with the ssh-keygen side and how the rest of the parsing works
>> > (like Fabian) can verify that this is OK.
>> >
>>
>> A good point. I just tested this and CR is a valid character to use in a
>> principal name in the allowed signers file and as of now the principal will be
>> passed to the verify call `as is` and everything works just fine. When we
>> introduce the patch above a principal with a CR in it will fail to verify.
>
>Are you sure? I thought that we split principals in allowed_signers on
>most whitespace, including \r. Follow:
>
>https://github.com/openssh/openssh-portable/blob/e9c7149/sshsig.c#L742
>https://github.com/openssh/openssh-portable/blob/e9c7149/misc.c#L452
>https://github.com/openssh/openssh-portable/blob/e9c7149/misc.c#L408
>
Sorry, I should have mentioned that I quoted the principal. Within the
quotes whitespace (and \r) works. Since find-principals then returns one
principal per line the line ending issue can come up.
>> I've added Damien Miller to this thread. He knows more about what the expected
>> behaviour for the principal would/should be. I think at the moment almost
>> everything except \n or \0 goes. Maybe restricting \r as well would make life
>> easier for other uses too?
>
>IMO sensible content for the principals section would be printable, non-
>whitespace characters, excluding wildcards ('*', '?'). ssh-keygen mostly
>assumes that the file is in good order, but maybe it could be stricter.
>
Ok, I think we can make sure of that when adding principals and use Junios
suggested patch for trimming the \r at the line ending.
>> If we add `trust on first use` in a future series I would assume we use the
>> email address from the commit/tag author ident when adding a new principal to
>> the file. Can the ident contain a CR?
>> Even if it did, I would only allow a list of allowed alphanumeric chars to be
>> added anyway since a principal can contain wildcards which we obviously don't
>> want to trust on first use ;).
>
>Yeah. my mental model for the allowed_signers file is that it's similar
>to ~/.ssh/authorized_keys in that it directly controls authn/authz
>decisions, and if you put bad stuff in there then you're going to have
>a bad day...
>
Thanks for your input.
next prev parent reply other threads:[~2021-12-06 8:40 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-12-03 13:31 [PATCH] gpg-interface: trim CR from ssh-keygen -Y find-principals Johannes Schindelin via GitGitGadget
2021-12-03 14:18 ` Fabian Stelzer
2021-12-03 15:58 ` Jeff King
2021-12-04 13:11 ` Fabian Stelzer
2021-12-05 5:50 ` Junio C Hamano
[not found] ` <CABPYr=y+sDDko9zPxQTOM6Tz4E7CafH7hJc6oB1zv7XYA9KH1A@mail.gmail.com>
2021-12-09 16:33 ` Fabian Stelzer
[not found] ` <CABPYr=xfotWvTQK9k1eKHa0kP4SsB=TKKuM0d8cpMb5BtuUZLA@mail.gmail.com>
2021-12-09 17:20 ` Fabian Stelzer
2021-12-30 10:25 ` Fabian Stelzer
2021-12-05 23:06 ` Damien Miller
2021-12-06 8:39 ` Fabian Stelzer [this message]
2022-01-03 9:53 ` [PATCH v2] gpg-interface: trim CR from ssh-keygen Fabian Stelzer
2022-01-03 17:17 ` Eric Sunshine
2022-01-03 23:34 ` Junio C Hamano
2022-01-04 0:41 ` Eric Sunshine
2022-01-04 1:19 ` Junio C Hamano
2022-01-04 3:06 ` Eric Sunshine
2022-01-04 12:55 ` Fabian Stelzer
2022-01-04 19:33 ` Junio C Hamano
2022-01-05 7:09 ` Eric Sunshine
2022-01-05 10:36 ` Fabian Stelzer
2022-01-05 20:40 ` Junio C Hamano
2022-01-06 10:26 ` Fabian Stelzer
2022-01-06 17:50 ` Junio C Hamano
2022-01-09 20:49 ` Eric Sunshine
2022-01-10 12:28 ` Fabian Stelzer
2022-01-07 9:07 ` [PATCH v3] " Fabian Stelzer
2022-01-09 21:37 ` Eric Sunshine
2022-01-10 12:59 ` Fabian Stelzer
2022-01-10 17:51 ` Junio C Hamano
2022-01-10 17:03 ` Junio C Hamano
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