On 01/21/2015 12:28 AM, Bhuvan Gupta wrote:
I am working with selinux sandbox
"http://danwalsh.livejournal.com/28545.html".
Blog clearing mentions that the sandbox "Can not Open or Create any
files on the system " except the the shared libraries.
But current sandbox allow to read dir stuff which i think should not
be allowed:
currently i can successfully ran: /
"sandbox ls /usr"/
ls -Z for my /usr is:
/drwxr-xr-x. root root system_u:object_r:usr_t:s0 usr/
Right this is system objects. You are allowed to read/execute most
content under /usr, since sandbox needs to execute programs.
Now i used sesearch based policy analysis tool to find the allow
rules
and i have listed few which i can understand and think should not be
there:
[1] /allow sandbox_domain default_t : file { ioctl read write getattr
lock append } ; / # sandbox_t is allow to read write to file having
type as default_t, but it doesnt allow to open it..so whats the
significance of {read write}
This is for leaking a file descriptor into the
container. cat /foo/bar
| sandbox app > /tmp/output
We want to allow a user to open a file descriptor to any object on the
machine and then leak the file descriptor into the sandboxed app. The
sandboxed app is not allowed to Open any files on the system except
content with base labels, like usr_t, etc_t, bin_t, lib_t. And these
labels it is not allowed to write.
[2] /allow domain usr_t : dir { ioctl read getattr lock search open }
/
Added my system details and also attached the completed allowed list .
I have started with selinux about 1 week back so there might be
problem with my thinking model.
/*Does the above stuff make sense from logical point of view and
should fixed ?*/
Initially i thought that i will just disallow what i dont want...but
know i have realised that selinux is denial by default model and we
can only allow stuff.
Correct. If you want to write a more confined SELinux Type, you can,
but you have to start from scratch. And then you allow what you want.
There is an effort to build
a new language called CIL, which would allow you to take an existing
type and create a new type based on that type and remove access. But we
currently do not use this language
>>yum list installed | grep selinux
libselinux.x86_64 2.2.2-6.el7
libselinux-python.x86_64 2.2.2-6.el7
libselinux-utils.x86_64 2.2.2-6.el7
selinux-policy.noarch 3.12.1-153.el7_0.13
selinux-policy-devel.noarch 3.12.1-153.el7_0.13
selinux-policy-sandbox.noarch 3.12.1-153.el7_0.13
selinux-policy-targeted.noarch 3.12.1-153.el7_0.13
>> yum list installed | grep sandbox
selinux-policy-sandbox.noarch 3.12.1-153.el7_0.13
Thanks
Bhuvan
On Tue, Jan 20, 2015 at 2:36 AM, Daniel J Walsh <dwalsh(a)redhat.com
<mailto:dwalsh@redhat.com>> wrote:
What do you want to Disallow?
On 01/18/2015 06:34 AM, Bhuvan Gupta wrote:
> Hello,
>
> "Audit2allow" can add rule to allow some operation.
> But let say we want to disallow some operation which is allowed
> by some policy module. let say open operation on some files.
>
> Is there a easy way to achieve that ?
>
> Or i do have to:
> [1] get the policy source.
> [2] edit it accordingly
> [3] build and reinstall the policy.
>
>
> Thanks
> Bhuvan
>
>
>
>
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