Chad Sellers wrote:
On 4/16/09 2:10 PM, "Eric Paris" <eparis@xxxxxxxxxx> wrote:
He's some concerns/thoughts.
domain_t calls access(W_OK) on file_t.
This generates a denial
denied { access_write } scontext=domain_t tcontext=file_t tclass=file
Which audit2allow will gladly turn into:
allow domain_t file_t:file { access_write }
Load that module and then, POP the next time
denied { write } scontext=domain_t tcontext=file_t tclass=file
So somewhere we need some sort of synchronization.
---
I suggested to Dan that audit2allow should should, given the above
access_write denial output:
allow domain_t file_t:file { write }
and the tool chain just automatically maps all write rule to both allow
bits for BOTH write and access_write.
---
We could also have the tool chain just run in both directions and leave
audit2allow alone. Any rule with access_write would cause the tool
chain to add write and any rule with write would cause us to add
access_write.
From the point of view of policy analysis I think think that makes
things worse. Now the access_write rule really means something. That's
fine with me, but I have a feeling the people who care about policy
analysis might not like that idea.....
I think these issues point to how inelegant this solution is. Relying on the
toolchain to special case this and modify all results is going to be
painful. Another example of this comes up when applying analysis tools to
the policy. SETools will now show rules in a binary policy that can only be
traced back to the source policy if you understand how the compiler mangling
works. Managed policy has allowed us to decrease the amount of policy
mangling we do, and this strategy seems to be going the other direction.
I'd like to put in a vote for having access call the _noaudit interface to
suppress the audit record. I agree with Alexey though that it would need to
have something in /selinux to toggle this on/off. Then, when debugging a
policy and not getting denials, you'd throw this switch when to the point of
disabling dontaudits. We could even have semodule -D toggle this as well, if
we really want to bake this into the toolchain somewhere. As far as probing
attacks go, systems with more stringent security requirements that want to
see all possible probing attacks could turn this flag on all the time.
I agree with this, Eric's description of what needs to happen above makes me
cringe. There is very limited utility to having 2 parallel sets of permissions
that need to be synchronized by the toolchain and quite a bit of potential pain.
One example of horrific pain would be if both the access_write and write rules
were present in policy, and someone wanted to remove the write access. They do
the necessary searching and find where write is granted, remove it and viola -
nothing happens, write access is still granted. Very confusing, I could see even
experienced policy writers getting bitten by this enough to curse the day these
permissions were added.
--
This message was distributed to subscribers of the selinux mailing list.
If you no longer wish to subscribe, send mail to majordomo@xxxxxxxxxxxxx with
the words "unsubscribe selinux" without quotes as the message.
