I am seeing (on RHEL 7.4 w/systemd) that halting the system doesn't work. It took me a long time (and a lot of help from Steve L.) to figure out what was going on. It turns out in refpolicy the default label for /usr/lib/systemd/systemd-shutdown is bin_t. But when systemd tried to execve systemd-shutdown it fails because init_t isn't allowed file entrypoint for bin_t. When I labeled systemd-shutdown as init_exec_t shutting down the system works.
I was seeing the following log (from systemd) when I enabled systemd debug logging (which was very useful).
[ 59.745037] systemd[1]: Starting Final Step.
[ 59.746112] systemd[1]: Starting Power-Off...
[ 59.776320] systemd[1]: Shutting down.
[ 59.783559] systemd[1]: Failed to execute shutdown binary, freezing: Operation not permitted
At this point everything locks up instead of actually halting the system.
This is a patch to change the label for systemd-shutdown which solves the problem. I'm happy to go through and make a distinct type of systemd-shutdown if someone doesn't think it is a good idea to share the type with systemd. But based on what is going on, this might be reasonable.
Signed-off-by: Dave Sugar <[email protected]>
---
policy/modules/system/init.fc | 1 +
1 file changed, 1 insertion(+)
diff --git a/policy/modules/system/init.fc b/policy/modules/system/init.fc
index 34bb6a7c..548a8631 100644
--- a/policy/modules/system/init.fc
+++ b/policy/modules/system/init.fc
@@ -29,6 +29,7 @@ ifdef(`distro_gentoo',`
/usr/bin/upstart -- gen_context(system_u:object_r:init_exec_t,s0)
/usr/lib/systemd/systemd -- gen_context(system_u:object_r:init_exec_t,s0)
+/usr/lib/systemd/systemd-shutdown -- gen_context(system_u:object_r:init_exec_t,s0)
/usr/lib/systemd/system-preset(/.*)? gen_context(system_u:object_r:systemd_unit_t,s0)
/usr/lib/systemd/user-preset(/.*)? gen_context(system_u:object_r:systemd_unit_t,s0)
/usr/lib/systemd/ntp-units\.d -d gen_context(system_u:object_r:systemd_unit_t,s0)
--
2.13.6
On Fri, Dec 08, 2017 at 10:30:58PM +0000, David Sugar via refpolicy wrote:
> I am seeing (on RHEL 7.4 w/systemd) that halting the system doesn't work. It took me a long time (and a lot of help from Steve L.) to figure out what was going on. It turns out in refpolicy the default label for /usr/lib/systemd/systemd-shutdown is bin_t. But when systemd tried to execve systemd-shutdown it fails because init_t isn't allowed file entrypoint for bin_t. When I labeled systemd-shutdown as init_exec_t shutting down the system works.
>
> I was seeing the following log (from systemd) when I enabled systemd debug logging (which was very useful).
>
> [ 59.745037] systemd[1]: Starting Final Step.
> [ 59.746112] systemd[1]: Starting Power-Off...
> [ 59.776320] systemd[1]: Shutting down.
> [ 59.783559] systemd[1]: Failed to execute shutdown binary, freezing: Operation not permitted
>
> At this point everything locks up instead of actually halting the system.
>
> This is a patch to change the label for systemd-shutdown which solves the problem. I'm happy to go through and make a distinct type of systemd-shutdown if someone doesn't think it is a good idea to share the type with systemd. But based on what is going on, this might be reasonable.
It is very hard to target systemd-shutdown so it may indeed not be worth the trouble. I actually did confine systemd-shutdown in my personal policy but i am not sure if i would do it again with today's knowledge
A couple of aspects that make it hard:
systemd-shutdown actually becomes pid one
systemd-shutdown does a lot of work when pretty much all logging has seized. With a serial console you will be able to get some info but not all, so at some point developing policy for it takes "brute force"/ "reverse engineering"
Its a great exercise though and it give one a great feeling when/if you actually succeed
>
> Signed-off-by: Dave Sugar <[email protected]>
> ---
> policy/modules/system/init.fc | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/policy/modules/system/init.fc b/policy/modules/system/init.fc
> index 34bb6a7c..548a8631 100644
> --- a/policy/modules/system/init.fc
> +++ b/policy/modules/system/init.fc
> @@ -29,6 +29,7 @@ ifdef(`distro_gentoo',`
> /usr/bin/upstart -- gen_context(system_u:object_r:init_exec_t,s0)
>
> /usr/lib/systemd/systemd -- gen_context(system_u:object_r:init_exec_t,s0)
> +/usr/lib/systemd/systemd-shutdown -- gen_context(system_u:object_r:init_exec_t,s0)
> /usr/lib/systemd/system-preset(/.*)? gen_context(system_u:object_r:systemd_unit_t,s0)
> /usr/lib/systemd/user-preset(/.*)? gen_context(system_u:object_r:systemd_unit_t,s0)
> /usr/lib/systemd/ntp-units\.d -d gen_context(system_u:object_r:systemd_unit_t,s0)
> --
> 2.13.6
> _______________________________________________
> refpolicy mailing list
> refpolicy at oss.tresys.com
> http://oss.tresys.com/mailman/listinfo/refpolicy
--
Key fingerprint = 5F4D 3CDB D3F8 3652 FBD8 02D5 3B6C 5F1D 2C7B 6B02
https://sks-keyservers.net/pks/lookup?op=get&search=0x3B6C5F1D2C7B6B02
Dominick Grift
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: application/pgp-signature
Size: 659 bytes
Desc: not available
Url : http://oss.tresys.com/pipermail/refpolicy/attachments/20171209/a85e7b1d/attachment.bin
On 12/08/2017 05:30 PM, David Sugar via refpolicy wrote:
> I am seeing (on RHEL 7.4 w/systemd) that halting the system doesn't work. It took me a long time (and a lot of help from Steve L.) to figure out what was going on. It turns out in refpolicy the default label for /usr/lib/systemd/systemd-shutdown is bin_t. But when systemd tried to execve systemd-shutdown it fails because init_t isn't allowed file entrypoint for bin_t. When I labeled systemd-shutdown as init_exec_t shutting down the system works.
>
> I was seeing the following log (from systemd) when I enabled systemd debug logging (which was very useful).
>
> [ 59.745037] systemd[1]: Starting Final Step.
> [ 59.746112] systemd[1]: Starting Power-Off...
> [ 59.776320] systemd[1]: Shutting down.
> [ 59.783559] systemd[1]: Failed to execute shutdown binary, freezing: Operation not permitted
>
> At this point everything locks up instead of actually halting the system.
>
> This is a patch to change the label for systemd-shutdown which solves the problem. I'm happy to go through and make a distinct type of systemd-shutdown if someone doesn't think it is a good idea to share the type with systemd. But based on what is going on, this might be reasonable.
>
> Signed-off-by: Dave Sugar <[email protected]>
> ---
> policy/modules/system/init.fc | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/policy/modules/system/init.fc b/policy/modules/system/init.fc
> index 34bb6a7c..548a8631 100644
> --- a/policy/modules/system/init.fc
> +++ b/policy/modules/system/init.fc
> @@ -29,6 +29,7 @@ ifdef(`distro_gentoo',`
> /usr/bin/upstart -- gen_context(system_u:object_r:init_exec_t,s0)
>
> /usr/lib/systemd/systemd -- gen_context(system_u:object_r:init_exec_t,s0)
> +/usr/lib/systemd/systemd-shutdown -- gen_context(system_u:object_r:init_exec_t,s0)
> /usr/lib/systemd/system-preset(/.*)? gen_context(system_u:object_r:systemd_unit_t,s0)
> /usr/lib/systemd/user-preset(/.*)? gen_context(system_u:object_r:systemd_unit_t,s0)
> /usr/lib/systemd/ntp-units\.d -d gen_context(system_u:object_r:systemd_unit_t,s0)
Merged.
--
Chris PeBenito