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From: Jeff King <peff@peff.net>
To: Karthik Nayak <karthik.188@gmail.com>
Cc: chris.torek@gmail.com, git@vger.kernel.org, gitster@pobox.com, ps@pks.im
Subject: Re: [PATCH v3 0/8] refs: add symref support to 'git-update-ref'
Date: Tue, 23 Apr 2024 18:03:08 -0400	[thread overview]
Message-ID: <20240423220308.GC1172807@coredump.intra.peff.net> (raw)
In-Reply-To: <20240423212818.574123-1-knayak@gitlab.com>

On Tue, Apr 23, 2024 at 11:28:10PM +0200, Karthik Nayak wrote:

> Changes from v2:
> 1. We no longer have separate commands for symrefs, instead the regular
> commands learn to parse 'ref:<target>' as symref targets. This reduces
> the code in this series. Thanks Patrick for the suggestion.

Hmm. I can see how this makes things a lot simpler, but it introduces an
ambiguity, since you can pass full ref expressions to "update-ref" (like
"ref:foo" to find the "foo" entry in ref^{tree}). I see that you only
kick in the symref "ref:" handling if the regular oid lookup failed, so
there's no backwards-compatibility issue (anything that used to work
will still take precedence, and the new code only runs when the old code
would have reported an error).

But I wonder if it would let somebody cause mischief in a repository
they can push to, but which may get updates from other sources. For
example, imagine a forge like GitLab runs the equivalent of:

  echo "create refs/whatever ref:refs/heads/main" |
  git update-ref --stdin

as part of some system process. Now if I push up "refs/heads/ref" that
contains the path "refs/heads/main" in its tree, that will take
precedence, causing the system process to do something it did not
expect.

I think you'd have to pile on a lot of assumptions to get any kind of
security problem. Something like:

 1. The system has a hidden ref namespace like refs/gitlab that normal
    remote push/fetch users are not allowed to read/write to.

 2. The system tries to make a symlink within that namespace. Say,
    "refs/gitlab/metadata/HEAD" to point to
    "refs/gitlab/metadata/branches/main" or something.

 3. The user pushes up "refs/heads/ref" with a tree that contains
    "refs/gitlab/metadata/branches/main". Now when (2) happens, the
    hidden ref points to user-controlled data.

That's pretty convoluted. But we can avoid it entirely if there's no
ambiguity in the protocol at all.

-Peff

  parent reply	other threads:[~2024-04-23 22:03 UTC|newest]

Thread overview: 194+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2024-03-30 22:46 [PATCH 0/8] update-ref: add support for update-symref option Karthik Nayak
2024-03-30 22:46 ` [PATCH 1/8] files-backend: extract out `create_symref_lock` Karthik Nayak
2024-04-02 12:20   ` Patrick Steinhardt
2024-04-03 14:52     ` Karthik Nayak
2024-03-30 22:46 ` [PATCH 2/8] reftable-backend: extract out `write_symref_with_log` Karthik Nayak
2024-04-02 12:20   ` Patrick Steinhardt
2024-03-30 22:46 ` [PATCH 3/8] reftable-backend: move `write_symref_with_log` up Karthik Nayak
2024-03-30 22:46 ` [PATCH 4/8] refs: accept symref in `ref_transaction_add_update` Karthik Nayak
2024-03-30 22:46 ` [PATCH 5/8] refs/files-backend: add support for symref updates Karthik Nayak
2024-04-02 12:20   ` Patrick Steinhardt
2024-03-30 22:46 ` [PATCH 6/8] refs/reftable-backend: " Karthik Nayak
2024-04-02 12:20   ` Patrick Steinhardt
2024-03-30 22:46 ` [PATCH 7/8] refs: add 'update-symref' command to 'update-ref' Karthik Nayak
2024-03-31 22:08   ` Junio C Hamano
2024-03-31 22:27     ` Chris Torek
2024-03-31 23:14       ` Junio C Hamano
2024-04-01  1:31         ` Junio C Hamano
2024-04-02 12:20           ` Patrick Steinhardt
2024-04-02 16:40             ` Junio C Hamano
2024-04-09 11:55               ` Patrick Steinhardt
2024-04-09 16:15                 ` Karthik Nayak
2024-04-10  4:20                   ` Patrick Steinhardt
2024-04-10 16:06                     ` Junio C Hamano
2024-04-10 17:31                       ` Patrick Steinhardt
2024-04-01 10:38       ` Karthik Nayak
2024-04-01 11:48     ` Karthik Nayak
2024-04-01 16:17       ` Junio C Hamano
2024-04-01 20:40         ` Junio C Hamano
2024-04-01 22:37         ` Karthik Nayak
2024-03-30 22:46 ` [PATCH 8/8] refs: support symrefs in 'reference-transaction' hook Karthik Nayak
2024-04-02 12:20   ` Patrick Steinhardt
2024-04-12  9:59 ` [PATCH v2 0/7] update-ref: add symref oriented commands Karthik Nayak
2024-04-12  9:59   ` [PATCH v2 1/7] refs: accept symref values in `ref_transaction[_add]_update` Karthik Nayak
2024-04-18 14:25     ` Christian Couder
2024-04-19 10:28       ` Karthik Nayak
2024-04-18 15:08     ` Phillip Wood
2024-04-19  9:40       ` Patrick Steinhardt
2024-04-19 15:47       ` Karthik Nayak
2024-05-04 15:15         ` phillip.wood123
2024-04-19  9:40     ` Patrick Steinhardt
2024-04-19 18:09       ` Karthik Nayak
2024-04-23  6:31         ` Patrick Steinhardt
2024-04-23 10:48           ` Karthik Nayak
2024-04-12  9:59   ` [PATCH v2 2/7] update-ref: add support for symref-verify Karthik Nayak
2024-04-18 14:26     ` Christian Couder
2024-04-19 21:21       ` Karthik Nayak
2024-04-19  9:40     ` Patrick Steinhardt
2024-04-19 21:53       ` Karthik Nayak
2024-04-12  9:59   ` [PATCH v2 3/7] update-ref: add support for symref-delete Karthik Nayak
2024-04-18 14:52     ` Christian Couder
2024-04-21 10:43       ` Karthik Nayak
2024-04-19  9:40     ` Patrick Steinhardt
2024-04-21 10:45       ` Karthik Nayak
2024-04-12  9:59   ` [PATCH v2 4/7] files-backend: extract out `create_symref_lock` Karthik Nayak
2024-04-12  9:59   ` [PATCH v2 5/7] update-ref: add support for symref-create Karthik Nayak
2024-04-19  9:40     ` Patrick Steinhardt
2024-04-19 15:48       ` Junio C Hamano
2024-04-21 12:50       ` Karthik Nayak
2024-04-21 15:57         ` Karthik Nayak
2024-04-23  6:39         ` Patrick Steinhardt
2024-04-23 10:52           ` Karthik Nayak
2024-04-12  9:59   ` [PATCH v2 6/7] update-ref: add support for symref-update Karthik Nayak
2024-04-19  9:40     ` Patrick Steinhardt
2024-04-21 19:00       ` Karthik Nayak
2024-04-23  6:49         ` Patrick Steinhardt
2024-04-23 11:30           ` Karthik Nayak
2024-04-12  9:59   ` [PATCH v2 7/7] refs: support symrefs in 'reference-transaction' hook Karthik Nayak
2024-04-12 18:01   ` [PATCH v2 0/7] update-ref: add symref oriented commands Junio C Hamano
2024-04-12 18:49     ` Karthik Nayak
2024-04-18 15:05   ` Christian Couder
2024-04-21 19:06     ` Karthik Nayak
2024-04-20  6:16   ` Patrick Steinhardt
2024-04-21 19:11     ` Karthik Nayak
2024-04-23 21:28   ` [PATCH v3 0/8] refs: add symref support to 'git-update-ref' Karthik Nayak
2024-04-23 21:28     ` [PATCH v3 1/8] refs: accept symref values in `ref_transaction[_add]_update` Karthik Nayak
2024-04-23 21:28     ` [PATCH v3 2/8] update-ref: support parsing ref targets in `parse_next_oid` Karthik Nayak
2024-04-23 21:28     ` [PATCH v3 3/8] files-backend: extract out `create_symref_lock` Karthik Nayak
2024-04-23 21:28     ` [PATCH v3 4/8] update-ref: support symrefs in the verify command Karthik Nayak
2024-04-23 21:28     ` [PATCH v3 5/8] update-ref: support symrefs in the delete command Karthik Nayak
2024-04-23 21:28     ` [PATCH v3 6/8] update-ref: support symrefs in the create command Karthik Nayak
2024-04-23 21:28     ` [PATCH v3 7/8] update-ref: support symrefs in the update command Karthik Nayak
2024-04-23 21:28     ` [PATCH v3 8/8] ref: support symrefs in 'reference-transaction' hook Karthik Nayak
2024-04-23 22:03     ` Jeff King [this message]
2024-04-24  1:17       ` [PATCH v3 0/8] refs: add symref support to 'git-update-ref' Junio C Hamano
2024-04-24 16:25       ` Karthik Nayak
2024-04-25  6:40         ` Patrick Steinhardt
2024-04-25 21:12           ` Karthik Nayak
2024-04-25 18:01         ` Junio C Hamano
2024-04-25 21:14           ` Karthik Nayak
2024-04-25 21:55             ` Junio C Hamano
2024-04-26 12:48               ` Karthik Nayak
2024-04-26 20:41         ` Jeff King
2024-04-25 17:09     ` Junio C Hamano
2024-04-25 21:07       ` Karthik Nayak
2024-04-26 15:24     ` [PATCH v4 0/7] add symref-* commands to 'git-update-ref --stdin' Karthik Nayak
2024-04-26 15:24       ` [PATCH v4 1/7] refs: accept symref values in `ref_transaction[_add]_update` Karthik Nayak
2024-04-26 19:31         ` Junio C Hamano
2024-04-26 21:15           ` Jeff King
2024-04-29  7:02             ` Patrick Steinhardt
2024-04-29  7:55               ` Jeff King
2024-04-29  9:29                 ` phillip.wood123
2024-04-29  9:32             ` phillip.wood123
2024-04-29 16:18               ` Junio C Hamano
2024-04-30 10:33                 ` Jeff King
2024-04-30 10:30               ` Jeff King
2024-04-28 19:36           ` Karthik Nayak
2024-04-29 13:38         ` Phillip Wood
2024-04-29 14:01           ` Karthik Nayak
2024-04-26 15:24       ` [PATCH v4 2/7] files-backend: extract out `create_symref_lock` Karthik Nayak
2024-04-26 21:39         ` Junio C Hamano
2024-04-28 19:57           ` Karthik Nayak
2024-04-26 15:24       ` [PATCH v4 3/7] update-ref: add support for 'symref-verify' command Karthik Nayak
2024-04-26 22:51         ` Junio C Hamano
2024-04-28 22:28           ` Karthik Nayak
2024-04-26 15:24       ` [PATCH v4 4/7] update-ref: add support for 'symref-delete' command Karthik Nayak
2024-04-26 15:24       ` [PATCH v4 5/7] update-ref: add support for 'symref-create' command Karthik Nayak
2024-04-26 15:24       ` [PATCH v4 6/7] update-ref: add support for 'symref-update' command Karthik Nayak
2024-04-26 15:24       ` [PATCH v4 7/7] ref: support symrefs in 'reference-transaction' hook Karthik Nayak
2024-04-30 10:14       ` [PATCH v4 0/7] add symref-* commands to 'git-update-ref --stdin' Karthik Nayak
2024-05-01 20:22       ` [PATCH v5 0/7] refs: add support for transactional symref updates Karthik Nayak
2024-05-01 20:22         ` [PATCH v5 1/7] refs: accept symref values in `ref_transaction_update()` Karthik Nayak
2024-05-01 20:22         ` [PATCH v5 2/7] files-backend: extract out `create_symref_lock()` Karthik Nayak
2024-05-01 22:06           ` Junio C Hamano
2024-05-02  7:47             ` Patrick Steinhardt
2024-05-02 11:05               ` Karthik Nayak
2024-05-02 16:49               ` Junio C Hamano
2024-05-01 20:22         ` [PATCH v5 3/7] refs: support symrefs in 'reference-transaction' hook Karthik Nayak
2024-05-01 23:05           ` Junio C Hamano
2024-05-02  5:32             ` Karthik Nayak
2024-05-01 20:22         ` [PATCH v5 4/7] refs: add support for transactional symref updates Karthik Nayak
2024-05-01 23:52           ` Junio C Hamano
2024-05-02  5:50             ` Karthik Nayak
2024-05-02  7:47               ` Patrick Steinhardt
2024-05-02 11:10                 ` Karthik Nayak
2024-05-02 16:51                 ` Junio C Hamano
2024-05-02 16:00               ` Junio C Hamano
2024-05-02 17:53           ` Junio C Hamano
2024-05-01 20:22         ` [PATCH v5 5/7] refs: use transaction in `refs_create_symref()` Karthik Nayak
2024-05-02  7:47           ` Patrick Steinhardt
2024-05-01 20:22         ` [PATCH v5 6/7] refs: rename `refs_create_symref()` to `refs_update_symref()` Karthik Nayak
2024-05-02  7:47           ` Patrick Steinhardt
2024-05-02 11:34             ` Karthik Nayak
2024-05-01 20:22         ` [PATCH v5 7/7] refs: remove `create_symref` and associated dead code Karthik Nayak
2024-05-02  7:47           ` Patrick Steinhardt
2024-05-02 16:53             ` Junio C Hamano
2024-05-02  0:20         ` [PATCH v5 0/7] refs: add support for transactional symref updates Junio C Hamano
2024-05-02  5:53           ` Karthik Nayak
2024-05-03 12:41         ` [PATCH v6 " Karthik Nayak
2024-05-03 12:41           ` [PATCH v6 1/7] refs: accept symref values in `ref_transaction_update()` Karthik Nayak
2024-05-04 15:18             ` Phillip Wood
2024-05-05 15:10               ` Karthik Nayak
2024-05-05 15:19                 ` phillip.wood123
2024-05-03 12:41           ` [PATCH v6 2/7] files-backend: extract out `create_symref_lock()` Karthik Nayak
2024-05-03 12:41           ` [PATCH v6 3/7] refs: support symrefs in 'reference-transaction' hook Karthik Nayak
2024-05-03 12:41           ` [PATCH v6 4/7] refs: add support for transactional symref updates Karthik Nayak
2024-05-05 14:09             ` Phillip Wood
2024-05-05 16:09               ` Karthik Nayak
2024-05-06  9:35                 ` Phillip Wood
2024-05-06 11:19                   ` Karthik Nayak
2024-05-06 13:19                     ` Phillip Wood
2024-05-06  9:54                 ` Phillip Wood
2024-05-06 11:22                   ` Karthik Nayak
2024-05-06 13:17                     ` Phillip Wood
2024-05-03 12:41           ` [PATCH v6 5/7] refs: use transaction in `refs_create_symref()` Karthik Nayak
2024-05-03 12:41           ` [PATCH v6 6/7] refs: rename `refs_create_symref()` to `refs_update_symref()` Karthik Nayak
2024-05-03 12:41           ` [PATCH v6 7/7] refs: remove `create_symref` and associated dead code Karthik Nayak
2024-05-03 23:09             ` Junio C Hamano
2024-05-04  9:30               ` Karthik Nayak
2024-05-03 16:45           ` [PATCH v6 0/7] refs: add support for transactional symref updates Junio C Hamano
2024-05-06  7:36           ` Patrick Steinhardt
2024-05-07  6:00           ` [PATCH v7 0/8] " Karthik Nayak
2024-05-07  6:00             ` [PATCH v7 1/8] refs: accept symref values in `ref_transaction_update()` Karthik Nayak
2024-05-07  6:00             ` [PATCH v7 2/8] files-backend: extract out `create_symref_lock()` Karthik Nayak
2024-05-07  6:00             ` [PATCH v7 3/8] refs: support symrefs in 'reference-transaction' hook Karthik Nayak
2024-05-07  6:00             ` [PATCH v7 4/8] refs: move `original_update_refname` to 'refs.c' Karthik Nayak
2024-05-07  6:00             ` [PATCH v7 5/8] refs: add support for transactional symref updates Karthik Nayak
2024-05-07  6:00             ` [PATCH v7 6/8] refs: use transaction in `refs_create_symref()` Karthik Nayak
2024-05-07  6:00             ` [PATCH v7 7/8] refs: rename `refs_create_symref()` to `refs_update_symref()` Karthik Nayak
2024-05-07  6:00             ` [PATCH v7 8/8] refs: remove `create_symref` and associated dead code Karthik Nayak
2024-05-07  6:25             ` [PATCH v7 0/8] refs: add support for transactional symref updates Junio C Hamano
2024-05-07  6:31               ` Junio C Hamano
2024-05-07 12:58             ` [PATCH v8 " Karthik Nayak
2024-05-07 12:58               ` [PATCH v8 1/8] refs: accept symref values in `ref_transaction_update()` Karthik Nayak
2024-05-07 12:58               ` [PATCH v8 2/8] files-backend: extract out `create_symref_lock()` Karthik Nayak
2024-05-07 12:58               ` [PATCH v8 3/8] refs: support symrefs in 'reference-transaction' hook Karthik Nayak
2024-05-07 12:58               ` [PATCH v8 4/8] refs: move `original_update_refname` to 'refs.c' Karthik Nayak
2024-05-07 12:58               ` [PATCH v8 5/8] refs: add support for transactional symref updates Karthik Nayak
2024-05-07 12:58               ` [PATCH v8 6/8] refs: use transaction in `refs_create_symref()` Karthik Nayak
2024-05-07 12:58               ` [PATCH v8 7/8] refs: rename `refs_create_symref()` to `refs_update_symref()` Karthik Nayak
2024-05-07 12:58               ` [PATCH v8 8/8] refs: remove `create_symref` and associated dead code Karthik Nayak
2024-05-07 15:50               ` [PATCH v8 0/8] refs: add support for transactional symref updates phillip.wood123
2024-05-07 16:32               ` Junio C Hamano
2024-05-12 17:17                 ` Karthik Nayak
2024-05-13 17:15                   ` Junio C Hamano

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