Hi,
The MLS policy is defined via the MLS contraints file (http://oss.tresys.com/projects/refpolicy/browser/trunk/policy/mls).
The default MLS policy in SELinux a modified Bell-LaPadula that enforces "no
read up, write equal".
The process clearance label isn't going to really come up
into play for these access decisions, the effective SL of process is the key
factor being utilized, as known as "l1" in the mls constraint language.
The type of the process of the process is very important
when analyzing the results. There are certain types, such as sysadm_t, which
have mls privileges, such as mlsfileread (http://oss.tresys.com/projects/refpolicy/browser/trunk/policy/modules/system/userdomain.if#L1214).
All of this impacts the ability to read and write files on
the system.
A couple fo slidesets on the MLS implementation are
available below....
-Chad
Dear All,
From: fedora-selinux-list-bounces@xxxxxxxxxx [mailto:fedora-selinux-list-bounces@xxxxxxxxxx] On Behalf Of Mohammad zoroufi
Sent: Thursday, April 23, 2009 6:45 AM
To: fedora-selinux-list@xxxxxxxxxx
Subject: No Read Up No Write Down
After switching on SELinux in MLS enforcing mode, I'd like to know how the slogan of "no read up, no write
down" works.
I created some text files with the following descriptions
TestFile_S0 system_u:object_r:usr_t:s0
TestFile_S0C2 system_u:object_r:usr_t:s0:c2
TestFile_S1 system_u:object_r:usr_t:s1
TestFile_S2 system_u:object_r:usr_t:s2
TestFile_S2C11 system_u:object_r:usr_t:s2:c11
TestFile_S2C5 system_u:object_r:usr_t:s2:c5
TestFile_S3 system_u:object_r:usr_t:s3
TestFile_S3C14 system_u:object_r:usr_t:s3:c14
TestFile_S3C5 system_u:object_r:usr_t:s3:c5
After creating these text file, I went to create users having different security clearance;
The clearance of each created user is listed bellow:
Login Name SELinux User Role MLS/MCS Range
first x_first xguest_r s0
second x_second sysadm_r s3-s3:c5.c15
third x_third sysadm_r s1:c3.c15-s3:c5.c10
forth x_forth system_r s1-s1:c0.c10
root root system_r s0-s15:c0.c1023
having the clearance delegated for each user I expect user first have read write access to TestFile_S0 and just
write access to all other files; user second have read access to files such as TestFile_S0, TestFile_S0C2,
TestFile_S2, TestFile_S2C5, TestFile_S2C11 and only write access to TestFile_S3, TestFile_S3C14.
when I switch to MLS enforcing mode I see something else.
These users have no permission to write to files they expect they have write access to.
I'd like to know the where this problem originates
Moreover when user first wants to take a list of the directory contents only TestFile_S0, TestFile_S1,
TestFile_S2 are listed not else; user second sees TestFile_S0, TestFile_S1, TestFile2, TestFile3; users
third and root sees all files; user forth sees just TestFile_S0 not more.
I don't know why such lists are taken when I'd like to take a list.
Any comment is wellcome
Best Regards
-- fedora-selinux-list mailing list fedora-selinux-list@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/fedora-selinux-list
