From: Johannes Schindelin <Johannes.Schindelin@gmx.de>
To: "Carlo Marcelo Arenas Belón" <carenas@gmail.com>
Cc: git@vger.kernel.org, gitster@pobox.com, bagasdotme@gmail.com,
phillip.wood123@gmail.com, "Guy Maurel" <guy.j@maurel.de>,
"SZEDER Gábor" <szeder.dev@gmail.com>,
"Randall Becker" <rsbecker@nexbridge.com>
Subject: Re: [PATCH v3 2/3] git-compat-util: avoid failing dir ownership checks if running privileged
Date: Thu, 5 May 2022 16:01:21 +0200 (CEST) [thread overview]
Message-ID: <nycvar.QRO.7.76.6.2205051545370.355@tvgsbejvaqbjf.bet> (raw)
In-Reply-To: <20220503065442.95699-3-carenas@gmail.com>
[-- Attachment #1: Type: text/plain, Size: 5560 bytes --]
Hi Carlo,
On Mon, 2 May 2022, Carlo Marcelo Arenas Belón wrote:
> bdc77d1d685 (Add a function to determine whether a path is owned by the
> current user, 2022-03-02) checks for the effective uid of the running
> process using geteuid() but didn't account for cases where that user was
> root (because git was invoked through sudo or a compatible tool) and the
> original uid that repository trusted for its config was no longer known,
> therefore failing the following otherwise safe call:
>
> guy@renard ~/Software/uncrustify $ sudo git describe --always --dirty
> [sudo] password for guy:
> fatal: unsafe repository ('/home/guy/Software/uncrustify' is owned by someone else)
>
> Attempt to detect those cases by using the environment variables that
> those tools create to keep track of the original user id, and do the
> ownership check using that instead.
>
> This assumes the environment the user is running on after going
> privileged can't be tampered with, and also adds code to restrict that
> the new behavior only applies if running as root, therefore keeping the
> most common case, which runs unprivileged, from changing, but because of
> that, it will miss cases where sudo (or an equivalent) was used to change
> to another unprivileged user or where the equivalent tool used to raise
> privileges didn't track the original id in a sudo compatible way.
Hmm. I do realize that this is a quite common scenario, and I wish we
would not need to rush for a fix here: Otherwise we could carefully design
an "untrusted" mode in which Git errors out on spawning user-specified
commands and on writing files (and avoids refreshing the index to avoid
having to write a file), but runs normally if none of that is needed.
> diff --git a/Documentation/config/safe.txt b/Documentation/config/safe.txt
> index 6d764fe0ccf..ee558ced8c7 100644
> --- a/Documentation/config/safe.txt
> +++ b/Documentation/config/safe.txt
> @@ -26,3 +26,12 @@ directory was listed in the `safe.directory` list. If `safe.directory=*`
> is set in system config and you want to re-enable this protection, then
> initialize your list with an empty value before listing the repositories
> that you deem safe.
> ++
> +When git tries to check for ownership of git repositories, it will
> +obviously do so with the uid of the user that is running git itself,
> +but if git is running as root, it will check first if it might have
> +been started through `sudo`, and if that is the case, will instead
> +use the uid of the user that did so.
> +If that is not what you would prefer and want git to only trust
> +repositories that are owned by root instead, then you should remove
> +the `SUDO_UID` variable from root's environment.
> diff --git a/git-compat-util.h b/git-compat-util.h
> index 63ba89dd31d..dfdd3e4f81a 100644
> --- a/git-compat-util.h
> +++ b/git-compat-util.h
> @@ -393,12 +393,50 @@ static inline int git_offset_1st_component(const char *path)
> #endif
>
> #ifndef is_path_owned_by_current_user
> +
> +#ifdef __TANDEM
> +#define ROOT_UID 65535
> +#else
> +#define ROOT_UID 0
> +#endif
I do wonder whether we have to play this kind of fragile game. Why not
simply respect `SUDO_UID` if it is set? It's not like we expect attackers
to have control over the environment and could set this malicously.
> +
> +/*
> + * this helper function overrides a ROOT_UID with the one provided by
> + * an environment variable, do not use unless the original user is
> + * root
> + */
> +static inline void extract_id_from_env(const char *env, uid_t *id)
> +{
> + const char *real_uid = getenv(env);
> +
> + /* discard any empty values */
> + if (real_uid && *real_uid) {
> + char *endptr;
> + unsigned long env_id;
> + int saved_errno = errno;
> +
> + errno = 0;
> + env_id = strtoul(real_uid, &endptr, 10);
> + if (!errno && !*endptr && env_id <= (uid_t)-1)
We should not look at `errno` here unless the return value of `strtoul()`
indicates that there might have been an error (i.e. when it is
`ULONG_MAX`).
Likewise, we need to either initialize `endptr` or only look at it when
`strtoul()` succeeded.
We could side-step all of this, of course, if we simply did this:
euid = getuid();
if (euid == ROOT_UID)
euid = git_env_ulong("SUDO_UID", euid);
> + *id = env_id;
> +
> + errno = saved_errno;
> + }
> +}
> +
> static inline int is_path_owned_by_current_uid(const char *path)
> {
> struct stat st;
> + uid_t euid;
> +
> if (lstat(path, &st))
> return 0;
> - return st.st_uid == geteuid();
> +
> + euid = geteuid();
> + if (euid == ROOT_UID)
> + extract_id_from_env("SUDO_UID", &euid);
> +
> + return st.st_uid == euid;
Since this code is not even compiled on Windows, I believe we need to
adjust the documentation accordingly ("On systems other than Windows,
where `sudo` is available, ...").
> }
>
> #define is_path_owned_by_current_user is_path_owned_by_current_uid
> diff --git a/t/t0034-root-safe-directory.sh b/t/t0034-root-safe-directory.sh
> index 6dac7a05cfd..dd659aed4e1 100755
> --- a/t/t0034-root-safe-directory.sh
> +++ b/t/t0034-root-safe-directory.sh
> @@ -32,7 +32,7 @@ test_expect_success SUDO 'setup' '
> )
> '
>
> -test_expect_failure SUDO 'sudo git status as original owner' '
> +test_expect_success SUDO 'sudo git status as original owner' '
> (
> cd root/r &&
> git status &&
> --
> 2.36.0.352.g0cd7feaf86f
Again, thank you for working on this!
Dscho
next prev parent reply other threads:[~2022-05-05 14:02 UTC|newest]
Thread overview: 170+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-04-26 18:31 [RFC PATCH] git-compat-util: avoid failing dir ownership checks if running priviledged Carlo Marcelo Arenas Belón
2022-04-26 19:48 ` Derrick Stolee
2022-04-26 19:56 ` Junio C Hamano
2022-04-26 20:10 ` rsbecker
2022-04-26 20:45 ` Carlo Arenas
2022-04-26 21:10 ` Junio C Hamano
2022-04-26 20:12 ` Carlo Arenas
2022-04-26 20:26 ` Carlo Arenas
2022-04-29 16:16 ` Derrick Stolee
2022-04-27 0:05 ` [PATCH] git-compat-util: avoid failing dir ownership checks if running privileged Carlo Marcelo Arenas Belón
2022-04-27 9:33 ` Phillip Wood
2022-04-27 12:30 ` Phillip Wood
2022-04-27 14:15 ` rsbecker
2022-04-27 15:58 ` Carlo Arenas
2022-04-27 16:14 ` Phillip Wood
2022-04-27 18:54 ` Junio C Hamano
2022-04-27 20:59 ` Carlo Arenas
2022-04-27 21:09 ` rsbecker
2022-04-27 21:25 ` Junio C Hamano
2022-04-28 17:56 ` Phillip Wood
2022-04-27 15:38 ` Carlo Arenas
2022-04-27 15:50 ` rsbecker
2022-04-27 16:19 ` Junio C Hamano
2022-04-27 16:45 ` Carlo Arenas
2022-04-27 17:22 ` Phillip Wood
2022-04-27 17:49 ` rsbecker
2022-04-27 17:54 ` Carlo Arenas
2022-04-27 18:05 ` rsbecker
2022-04-27 18:11 ` Carlo Arenas
2022-04-27 18:16 ` rsbecker
2022-04-27 16:31 ` Phillip Wood
2022-04-27 16:54 ` Carlo Arenas
2022-04-27 17:28 ` Phillip Wood
2022-04-27 17:49 ` Carlo Arenas
2022-04-27 22:26 ` [RFC PATCH v2] " Carlo Marcelo Arenas Belón
2022-04-27 22:33 ` Junio C Hamano
2022-04-28 3:35 ` [PATCH 0/2] fix `sudo make install` regression in maint Carlo Marcelo Arenas Belón
2022-04-28 3:35 ` [PATCH 1/2] Documentation: explain how safe.directory works when running under sudo Carlo Marcelo Arenas Belón
2022-04-28 5:17 ` Junio C Hamano
2022-04-28 5:58 ` Carlo Arenas
2022-04-28 6:41 ` Junio C Hamano
2022-04-28 3:35 ` [PATCH 2/2] t: add tests for safe.directory when running with sudo Carlo Marcelo Arenas Belón
2022-04-28 5:34 ` Junio C Hamano
2022-04-28 4:57 ` [PATCH 0/2] fix `sudo make install` regression in maint Junio C Hamano
2022-04-28 10:58 ` [PATCH v2 0/3] " Carlo Marcelo Arenas Belón
2022-04-28 10:58 ` [PATCH v2 1/3] git-compat-util: avoid failing dir ownership checks if running privileged Carlo Marcelo Arenas Belón
2022-04-28 18:02 ` Phillip Wood
2022-04-28 18:57 ` Carlo Arenas
2022-04-28 10:58 ` [PATCH v2 2/3] Documentation: explain how safe.directory works when running under sudo Carlo Marcelo Arenas Belón
2022-04-30 6:17 ` Bagas Sanjaya
2022-04-30 6:39 ` Junio C Hamano
2022-04-30 14:15 ` Carlo Marcelo Arenas Belón
2022-04-28 10:58 ` [PATCH v2 3/3] t: add tests for safe.directory when running with sudo Carlo Marcelo Arenas Belón
2022-04-28 16:55 ` Junio C Hamano
2022-04-28 18:08 ` Phillip Wood
2022-04-28 18:12 ` Junio C Hamano
2022-05-06 17:50 ` Carlo Arenas
2022-05-06 21:43 ` Junio C Hamano
2022-05-06 22:57 ` Carlo Arenas
2022-05-06 23:55 ` Junio C Hamano
2022-05-07 11:57 ` Carlo Marcelo Arenas Belón
2022-04-28 19:53 ` rsbecker
2022-04-28 20:22 ` Carlo Arenas
2022-04-28 20:43 ` rsbecker
2022-04-28 20:51 ` Junio C Hamano
2022-04-28 20:56 ` Carlo Arenas
2022-04-28 21:55 ` rsbecker
2022-04-28 22:21 ` Junio C Hamano
2022-04-28 22:45 ` rsbecker
2022-04-28 20:46 ` Junio C Hamano
2022-04-28 20:32 ` Junio C Hamano
2022-04-28 20:40 ` rsbecker
2022-04-28 20:48 ` Carlo Arenas
2022-04-28 21:02 ` Carlo Arenas
2022-04-28 21:07 ` Junio C Hamano
2022-04-29 1:24 ` Carlo Marcelo Arenas Belón
2022-04-29 18:50 ` Junio C Hamano
2022-04-29 20:05 ` Carlo Marcelo Arenas Belón
2022-05-02 18:39 ` [RFC PATCH v3 0/3] fix `sudo make install` regression in maint Carlo Marcelo Arenas Belón
2022-05-02 18:39 ` [RFC PATCH v3 1/3] t: document regression git safe.directory when using sudo Carlo Marcelo Arenas Belón
2022-05-02 21:35 ` Junio C Hamano
2022-05-02 23:07 ` Carlo Arenas
2022-05-02 18:39 ` [RFC PATCH v3 2/3] git-compat-util: avoid failing dir ownership checks if running privileged Carlo Marcelo Arenas Belón
2022-05-02 18:39 ` [RFC PATCH v3 3/3] t0034: enhance framework to allow testing more commands under sudo Carlo Marcelo Arenas Belón
2022-05-02 22:10 ` Junio C Hamano
2022-05-03 0:00 ` Carlo Arenas
2022-05-03 6:54 ` [PATCH v3 0/3] fix `sudo make install` regression in maint Carlo Marcelo Arenas Belón
2022-05-03 6:54 ` [PATCH v3 1/3] t: document regression git safe.directory when using sudo Carlo Marcelo Arenas Belón
2022-05-03 14:03 ` Phillip Wood
2022-05-03 15:56 ` Carlo Marcelo Arenas Belón
2022-05-04 11:15 ` Phillip Wood
2022-05-04 13:02 ` Carlo Arenas
2022-05-04 14:11 ` Phillip Wood
2022-05-05 13:44 ` Johannes Schindelin
2022-05-05 14:34 ` Phillip Wood
2022-05-05 15:50 ` Junio C Hamano
2022-05-05 18:33 ` Junio C Hamano
2022-05-05 19:39 ` Junio C Hamano
2022-05-06 21:03 ` Carlo Arenas
2022-05-09 8:21 ` Phillip Wood
2022-05-09 14:51 ` Carlo Arenas
2022-05-09 15:18 ` Phillip Wood
2022-05-09 16:01 ` Junio C Hamano
2022-05-09 16:21 ` Carlo Arenas
2022-05-06 17:39 ` Carlo Arenas
2022-05-03 6:54 ` [PATCH v3 2/3] git-compat-util: avoid failing dir ownership checks if running privileged Carlo Marcelo Arenas Belón
2022-05-05 14:01 ` Johannes Schindelin [this message]
2022-05-05 14:32 ` Phillip Wood
2022-05-06 19:15 ` Carlo Arenas
2022-05-06 20:00 ` Junio C Hamano
2022-05-06 20:22 ` Carlo Arenas
2022-05-06 20:59 ` Junio C Hamano
2022-05-06 21:40 ` Carlo Arenas
2022-05-06 21:07 ` rsbecker
2022-05-05 16:09 ` Junio C Hamano
2022-05-06 20:02 ` Carlo Arenas
2022-05-03 6:54 ` [PATCH v3 3/3] t0034: enhance framework to allow testing more commands under sudo Carlo Marcelo Arenas Belón
2022-05-03 14:12 ` Phillip Wood
2022-05-03 15:27 ` Junio C Hamano
2022-05-06 16:54 ` Carlo Arenas
2022-05-07 16:35 ` [RFC PATCH v4 0/3] fix `sudo make install` regression in maint Carlo Marcelo Arenas Belón
2022-05-07 16:35 ` [RFC PATCH v4 1/3] t: regression git needs safe.directory when using sudo Carlo Marcelo Arenas Belón
2022-05-07 16:35 ` [RFC PATCH v4 2/3] git-compat-util: avoid failing dir ownership checks if running privileged Carlo Marcelo Arenas Belón
2022-05-07 17:34 ` Junio C Hamano
2022-05-07 18:56 ` Carlo Marcelo Arenas Belón
2022-05-09 16:54 ` Junio C Hamano
2022-05-09 17:36 ` rsbecker
2022-05-09 18:48 ` Carlo Arenas
2022-05-09 19:16 ` rsbecker
2022-05-09 19:41 ` Junio C Hamano
2022-05-07 16:35 ` [RFC PATCH v4 3/3] t0034: add negative tests and allow git init to mostly work under sudo Carlo Marcelo Arenas Belón
2022-05-10 14:17 ` [RFC PATCH v4 0/3] fix `sudo make install` regression in maint Phillip Wood
2022-05-10 15:47 ` Carlo Arenas
2022-05-10 17:46 ` [PATCH " Carlo Marcelo Arenas Belón
2022-05-10 17:46 ` [PATCH v4 1/3] t: regression git needs safe.directory when using sudo Carlo Marcelo Arenas Belón
2022-05-10 22:10 ` Junio C Hamano
2022-05-10 23:11 ` Carlo Arenas
2022-05-10 23:44 ` Junio C Hamano
2022-05-11 0:56 ` Carlo Arenas
2022-05-11 1:11 ` Junio C Hamano
2022-05-10 17:46 ` [PATCH v4 2/3] git-compat-util: avoid failing dir ownership checks if running privileged Carlo Marcelo Arenas Belón
2022-05-10 22:57 ` Junio C Hamano
2022-05-11 7:34 ` Carlo Arenas
2022-05-11 14:58 ` Junio C Hamano
2022-05-10 17:46 ` [PATCH v4 3/3] t0034: add negative tests and allow git init to mostly work under sudo Carlo Marcelo Arenas Belón
2022-05-10 23:11 ` Junio C Hamano
2022-05-10 23:25 ` Junio C Hamano
2022-05-11 14:04 ` Carlo Arenas
2022-05-11 15:29 ` Junio C Hamano
2022-05-13 1:00 ` [PATCH v5 0/4] fix `sudo make install` regression in maint Carlo Marcelo Arenas Belón
2022-05-13 1:00 ` [PATCH v5 1/4] t: regression git needs safe.directory when using sudo Carlo Marcelo Arenas Belón
2022-06-03 12:12 ` SZEDER Gábor
2022-05-13 1:00 ` [PATCH v5 2/4] git-compat-util: avoid failing dir ownership checks if running privileged Carlo Marcelo Arenas Belón
2022-06-03 11:05 ` SZEDER Gábor
2022-06-03 16:54 ` Junio C Hamano
2022-06-03 17:34 ` SZEDER Gábor
2022-05-13 1:00 ` [PATCH v5 3/4] t0034: add negative tests and allow git init to mostly work under sudo Carlo Marcelo Arenas Belón
2022-05-13 1:20 ` Junio C Hamano
2022-05-14 14:36 ` Carlo Arenas
2022-05-15 16:54 ` Junio C Hamano
2022-05-15 19:21 ` Carlo Arenas
2022-05-16 5:27 ` Junio C Hamano
2022-05-16 13:07 ` Carlo Marcelo Arenas Belón
2022-05-16 16:25 ` Junio C Hamano
2022-05-13 1:00 ` [PATCH v5 4/4] git-compat-util: allow root to access both SUDO_UID and root owned Carlo Marcelo Arenas Belón
2022-06-15 14:02 ` Johannes Schindelin
2022-06-17 14:26 ` Carlo Arenas
2022-06-17 16:00 ` Junio C Hamano
2022-06-17 20:23 ` [PATCH v6] " Carlo Marcelo Arenas Belón
2022-06-17 21:02 ` Junio C Hamano
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
List information: http://vger.kernel.org/majordomo-info.html
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=nycvar.QRO.7.76.6.2205051545370.355@tvgsbejvaqbjf.bet \
--to=johannes.schindelin@gmx.de \
--cc=bagasdotme@gmail.com \
--cc=carenas@gmail.com \
--cc=git@vger.kernel.org \
--cc=gitster@pobox.com \
--cc=guy.j@maurel.de \
--cc=phillip.wood123@gmail.com \
--cc=rsbecker@nexbridge.com \
--cc=szeder.dev@gmail.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
Code repositories for project(s) associated with this public inbox
https://80x24.org/mirrors/git.git
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).