Hi
I am new to selinux and i have a couple basic questions regarding selinux
1.regarding the policy
Are the permissions flexible or rigid like DAC 3 bit rwx allocated to each group or can we add to.
I can see per the common permission we have things like read write getattr but if i wanted to add an additional permission like have read permission when the system is at a state X (assuming the system has a measured state) or allow read only when time is x & y
is it possible??
or would i have to set a conditional policy with the use of boolean values or extended the common permission or the class specific permission
2. regarding security contexts
for example fire fox wants to read a file the lookup inode will query the SID of the source and the targeted files. The LSM hook will relay the SIDs to the security server. which will in-turn map the SID to the security context which will then be crossed checked with the policy rules. my question is so where are the security context actually stored?or accessed by the security server?
and how does the xattr help in getting info on the security context.
Thanx
On Thu, Jan 2, 2014 at 3:53 AM, Russell Coker <russell@xxxxxxxxxxxx> wrote:
On Thu, 2 Jan 2014, bigclouds <bigclouds@xxxxxxx> wrote:
> there are not many document about internal of selinux on the internet.
> could you answer my questions, thanks
> # ps -eZ | grep qemu-kvm
> system_u:system_r:svirt_t:s0:c87,c520 27950 ? 00:00:17 qemu-kvm
>
> 1.there, svirt_t is a domain or a type? how to create a new type , just a
> sample is ok
In the way that SE Linux works internally there isn't a difference. With the
way the policy is written the attribute "domain" is applied to any type that
can be used for labelling a process.
#
# init_t is the domain of the init process.
#
type init_t, initrc_transition_domain;
type init_exec_t;
domain_type(init_t)
domain_entry_file(init_t, init_exec_t)
kernel_domtrans_to(init_t, init_exec_t)
role system_r types init_t;
Above is a snippet from init.te. It creates the "type" (where the word
applies to a policy language keyword) init_t and then uses the interface
"domain_type" to give it the attribute "domain".
> 2.how to know how much authority , on how many files,dirs,sockets....
> the process of qemu-kvm has? is there a command to show that?
The commands "apol" and "sesearch" allow you to discover that.
> 3. s0, if it can be s1,s2....(images have the same s*), if i do so , any
> other requirement? if type is targeted, if targeted has only one level,
> s0? in targeted case, s1,s2...is not valid?
s1 only exists if you use the MLS (Multi Level Security) policy, which you
almost certainly aren't using (it's an advanced feature and not enabled by
default in any distribution you are likely to use).
That level field in the label is also used by MCS (Multi Category Security)
which allows values such as "s0:c0" and "s0:c0,c3". Feel free to experiment
with that, you can use the command "runcon" to launch a process with a
different level and see what access it is permitted to have to files of
different level.
> 4.what does s(sensitive) and c(class) mean?
For MCS it's only s0 so it means nothing for you. MLS is more complex, master
MCS first.
> 5. there are two class, c520,c87. what is the upper limit of class
> amount.
The categories (not classes) are numbered from c0 to c1023, there are 1024 of
them but this is a policy compilation choice, you could rebuild the policy and
use more or less. In MCS to read a file a process needs to have every
category that the file has (or it needs to be in a domain that can override
the MCS controls).
--
My Main Blog http://etbe.coker.com.au/
My Documents Blog http://doc.coker.com.au/
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