On Mon, Mar 15, 2021 at 10:31 PM Lukas Javorsky <ljavorsk@redhat.com> wrote:

So IIRC, we don't need the setuid/setgid capability in Fedora/RHEL OS because we use systemd services right?

correct

Seems using mariadb memlock requires a LimitMEMLOCK too which needs extended documentation in https://mariadb.com/kb/en/systemd/.

Packaging / selinux related:

1. /etc/my.cnf.d/mariadb-server.cnf

contains log-error=/var/log/mariadb/mariadb.log

Without log-error set, the service will output to stdout/error and be captured by journald. Would this be better packaging for you?

This would help your outstanding rhbz on logrotation that I also haven't fixed upstream.

2. exec names now mariadb

in 10.4 we put mariadb names on executables a symlinks to mysql named binaries.

in 10.5 this was reverse.

This is a slow move to phase out these mysql names that I hope you can help with.

e.g. (10.4)

ls -al /usr/libexec/mariadbd
lrwxrwxrwx. 1 root root 6 Nov 12 11:44 /usr/libexec/mariadbd -> mysqld

What would help significantly is if the mariadb names got into the selinux fc file.

In https://github.com/fedora-selinux/selinux-policy/blob/rawhide/policy/modules/contrib/mysql.fc, I'm

With this the executables in the service could change.

2. mariadb.service

/usr/libexec/mysql-check-socket

is excessive - recent systemd won't allow a second process in the same cgroup when it has SendSIGKILL=no

(https://github.com/systemd/systemd/issues/8630)

On other Start{Pre,Post} in the service would you consider changing the name to mariadb?

Documentation="man:mariadbd(8)"

There's a fair few comments in https://github.com/MariaDB/server/blob/10.5/support-files/mariadb.service.in and its history that are probably relevant.

selinux and the mariadb PAM probably need a test/investigation too.

Happy to help if I can.

Thanks for clarifying

Lukas

On Sun, Mar 14, 2021 at 12:42 AM Daniel Black <daniel@mariadb.org> wrote:

This was relaxed in https://github.com/MariaDB/server/commit/27e6fd9a5968 where the setuid is only tried if mariadbd --user is specified.

This isn't the case with systemd service files (which set the user) https://github.com/MariaDB/server/blob/10.5/support-files/mariadb.service.in#L50 where

the CAP_IPC_LOCK capability gives the user the memlock rather than setuid.

So maybe it is safe to drop the mysqld_t setgid setuid from the policy for the common case of a user running systemd service which also works if they are using memlock.

While we are looking at the list, assuming sys_resource maps to CAP_SYS_RESOURCE that would only be raising the rlimit nofile, which is done in the systemd service.

in the server code this is capped anyway - https://github.com/MariaDB/server/blob/10.5/mysys/my_file.c#L42

sys_nice - seems to be related to a innodb setpriority(PRIO_PROCESS, tid, -20), which isn't fatal if it doesn't succeed. no other CAP_SYS_NICE are used.

Maybe we should have https://www.freedesktop.org/software/systemd/man/systemd.exec.html#LimitNICE= instead. Advice welcome.

allow mysqld_t self:shm create_shm_perms - not required in 10.5+ - shm no longer used for large pages - anon mmap is used.

rw_fifo_file_perms - one test case created a fifo - mysql-test/main/log_errchk.test, the server has some code to handle if log files externally created are fifos, but it doesn't create them itself.

galera code mentions fifo's a lot, however its an internal structure. Script https://github.com/MariaDB/server/blob/10.5/scripts/wsrep_sst_mariabackup.sh#L454 mentios fifos, however this

appears to just be using pv to rate limit.

https://github.com/MariaDB/server/pull/1553 is probably needed too.

I see https://github.com/fedora-selinux/selinux-policy/blob/rawhide/policy/modules/contrib/mysql.te#L106 probably covers https://github.com/MariaDB/server/pull/1131.

On Fri, Mar 12, 2021 at 10:14 PM Sergei Golubchik <serg@mariadb.org> wrote:

Hi, Lukas!

> I found that setuid/setgid is used inside mysqld_safe_helper
> (mariadbd-safe-helper).
> Are there any other cases when MariaDB uses these functions?

Yes, in the server. If the server is started with --memlock it does

  mlockall(MCL_CURRENT)

to prevent itself from being swapped. This needs root, and the server
uses setuid/setgid to drop root privileges after mlockall.

Regards,
Sergei
VP of MariaDB Server Engineering
and security@mariadb.org

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--

S pozdravom/ Best regards

Lukáš Javorský

Associate Software Engineer, Core service - Databases

Red Hat

Purkyňova 115 (TPB-C)

612 00 Brno - Královo Pole

ljavorsk@redhat.com