On 01/21/2015 12:28 AM, Bhuvan Gupta
wrote:
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
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