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authorSerge E. Hallyn <serue@us.ibm.com>2008-08-26 14:47:57 -0500
committerJames Morris <jmorris@namei.org>2008-08-27 08:54:08 +1000
commit93c06cbbf9fea5d5be1778febb7fa9ab1a74e5f5 (patch)
treede0ba51a2901097b7ab28483a040dc6ee5c9bc7d /Documentation/SELinux.txt
parent3f23d815c5049c9d7022226cec2242e384dd0b43 (diff)
downloadlinux-linaro-android-93c06cbbf9fea5d5be1778febb7fa9ab1a74e5f5.tar.gz
selinux: add support for installing a dummy policy (v2)
In August 2006 I posted a patch generating a minimal SELinux policy. This week, David P. Quigley posted an updated version of that as a patch against the kernel. It also had nice logic for auto-installing the policy. Following is David's original patch intro (preserved especially bc it has stats on the generated policies): se interested in the changes there were only two significant changes. The first is that the iteration through the list of classes used NULL as a sentinel value. The problem with this is that the class_to_string array actually has NULL entries in its table as place holders for the user space object classes. The second change was that it would seem at some point the initial sids table was NULL terminated. This is no longer the case so that iteration has to be done on array length instead of looking for NULL. Some statistics on the policy that it generates: The policy consists of 523 lines which contain no blank lines. Of those 523 lines 453 of them are class, permission, and initial sid definitions. These lines are usually little to no concern to the policy developer since they will not be adding object classes or permissions. Of the remaining 70 lines there is one type, one role, and one user statement. The remaining lines are broken into three portions. The first group are TE allow rules which make up 29 of the remaining lines, the second is assignment of labels to the initial sids which consist of 27 lines, and file system labeling statements which are the remaining 11. In addition to the policy.conf generated there is a single file_contexts file containing two lines which labels the entire system with base_t. This policy generates a policy.23 binary that is 7920 bytes. (then a few versions later...): The new policy is 587 lines (stripped of blank lines) with 476 of those lines being the boilerplate that I mentioned last time. The remaining 111 lines have the 3 lines for type, user, and role, 70 lines for the allow rules (one for each object class including user space object classes), 27 lines to assign types to the initial sids, and 11 lines for file system labeling. The policy binary is 9194 bytes. Changelog: Aug 26: Added Documentation/SELinux.txt Aug 26: Incorporated a set of comments by Stephen Smalley: 1. auto-setup SELINUXTYPE=dummy 2. don't auto-install if selinux is enabled with non-dummy policy 3. don't re-compute policy version 4. /sbin/setfiles not /usr/sbin/setfiles Aug 22: As per JMorris comments, made sure make distclean cleans up the mdp directory. Removed a check for file_contexts which is now created in the same file as the check, making it superfluous. Signed-off-by: Serge Hallyn <serue@us.ibm.com> Signed-off-by: David Quigley <dpquigl@tycho.nsa.gov> Signed-off-by: James Morris <jmorris@namei.org>
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+If you want to use SELinux, chances are you will want
+to use the distro-provided policies, or install the
+latest reference policy release from
+ http://oss.tresys.com/projects/refpolicy
+
+However, if you want to install a dummy policy for
+testing, you can do using 'mdp' provided under
+scripts/selinux. Note that this requires the selinux
+userspace to be installed - in particular you will
+need checkpolicy to compile a kernel, and setfiles and
+fixfiles to label the filesystem.
+
+ 1. Compile the kernel with selinux enabled.
+ 2. Type 'make' to compile mdp.
+ 3. Make sure that you are not running with
+ SELinux enabled and a real policy. If
+ you are, reboot with selinux disabled
+ before continuing.
+ 4. Run install_policy.sh:
+ cd scripts/selinux
+ sh install_policy.sh
+
+Step 4 will create a new dummy policy valid for your
+kernel, with a single selinux user, role, and type.
+It will compile the policy, will set your SELINUXTYPE to
+dummy in /etc/selinux/config, install the compiled policy
+as 'dummy', and relabel your filesystem.