[RFC] Source Policy, CIL, and High Level Languages

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In January, we sent an RFC [1] to update userspace to integrate CIL
[2] and source policy. And in April, we sent an updated RFC [3] which
added support for high level languages and a tool to convert policy
package (pp) files to CIL. After getting some good feedback, we have
made some more changes, mostly to maintain ABI compatibility. The
major changes made since the last patchset are:

- Change how semanage_set_root was re-added to use the source policy
  infrastructure. Fixes were made so that semanage.conf was looked for
  inside the root. Also adds an semanage_root() function to get the
  current root.
- In previous patchsets, the semanage_module_upgrade* and
  semanage_module_install_base* functions were removed from the API,
  and semanage_module_install* had modified parameters. However, these
  changes broke the API and ABI. To maintain ABI compatibility, we've
  now added symbolic versioning to support the old version of the
  functions, which now just call the new install functions. semodule
  is updated to support --base and --upgrade, but with the addition of
  a deprecation message. API compatability is not maintained.
- Likewise, symbolic versioning was added to support the old module
  enable/disable functions, which call the new enable/disable
  functions.
- Modify the libsepol Makefile to now make including CIL optional via
  the DISABLE_CIL build flag. This only affects libsepol (not
  libsemanage), primarily so that SE for Android does not need to
  include unused CIL cruft.

With these changes, ABI compatibility is maintained. Additionally, we
have tested these changes with the userspace tests and against the
kernel test suite, and no new failures were discovered. We have
also tested this patchset with both Fedora 20 policy and with reference
policy and found no errors.

Because of the size of the patchset (67 file changes, ~8300
insertions, ~1800 deletions), all the changes have been pushed to the
selinux git repository to the 'integration' branch for
comments/review. Unlike the previous RFCs, for simplicity there is now
only a single branch, containing three types of changes:

Reverts
   Reverts changes made to master that conflict with the new source
   policy infrastructure (e.g. how paths are handled,
   enabled/disable modules). Rather than dealing with a large amount
   of conflicts with the source policy work, it was easier to just
   remove the commits that added conflicting features, rebase the old
   source policy work on top of that, and add back any features in a
   manner consistent with source policy. The only conflicts were
   related to enabling/disabling of modules, and semanage_set_root.

Source Policy
   This is a rebase of the old src-policy branch on top of the
   reverted commits.  The goal of these changes is to improve the API
   for module handling, add support for source policies, module
   priorities, enabling/disabling of modules, and moving the policy
   store from /etc/selinux/<store>/ to /var/lib/selinux/<store>/.

CIL Integration
   These changes build CIL into libsepol, and updates libsepol,
   libsemanage, semodule, and semanage to work with and understand CIL
   files and manage /var/lib/selinux and /etc/selinux. Switching to
   CIL has a few side effects, such as removing base modules,
   versions, and upgrades.

   This also adds a new tool (installed to
   /usr/libexec/selinux/hll/pp), which is an HLL compiler that
   converts binary pp modules to CIL. The infrastructure to use this
   compiler (or any other HLL compiler) was added to compile HLL
   modules to CIL, which is accomplished by writing the HLL data to
   the stdin of the compiler and reading the equivilent CIL from
   stdout. The resulting CIL is then cached in the policy store so
   this compilation does not need to take place during future store
   updates. Cached CIL modules can be ignored using a new semodule
   flag (-C/--ignore-cache) or a new configuration option in
   semanage.conf (ignore-cache). Other configuration options were
   added to semanage.conf to manage the path to HLL compilers
   (compiler-directory) and the policy store (store-root). Semodule
   was also modified to support changing the policy store with the
   -S/--store-root option.

   Lastly, the CIL integration changes required changes to the API,
   but symbolic versioning was used to maintain ABI compatibility.
   Because of this, the .so version is no longer incremented like in
   the previous version of this RFC.

With these changes, it is possible to build and manage SELinux
policy using pp and CIL modules and the familiar semodule/semanage
tools.

To make this easier to experiment with and test, below are the steps
needed to install the updated userspace and migrate a minimal Fedora 20
installation to the new policy store.

Thanks, and we look forward to any questions/comments.

- Steve

[1] http://marc.info/?l=selinux&m=138921403805934&w=2
[2] https://github.com/SELinuxProject/cil/wiki
[3] http://marc.info/?l=selinux&m=139878606630921&w=2


Steps to Install SELinux Userspace with source policy, CIL, and HLL

# Start with a fresh Fedora 20-x86_64 Mimimal Installation

# Install SELinux userspace dependencies
$ yum install audit-libs-devel bison bzip2-devel dbus-devel
dbus-glib-devel flex flex-static gcc git glib2-devel libcap-ng-devel
libcgroup-devel libsepol-static pcre-devel python-devel python-IPy
setools-devel swig ustr-devel

# Update to the latest targeted policy
$ yum update selinux-policy-targeted

# Clone the repos and checkout branches
$ git clone -b integration https://github.com/SELinuxProject/selinux.git
$ git clone -b master https://github.com/SELinuxProject/cil.git

# Create a symlink to the cil repo so CIL can be built into libsepol
$ ln -s ~/cil/ selinux/libsepol/cil

# Install SELinux userspace with CIL integration and HLL support
$ make -C selinux LIBDIR=/usr/lib64 SHLIBDIR=/lib64 install install-pywrap

# Migrate to the new source policy infrastructure
$ ./selinux/libsemanage/utils/semanage_migrate_etc_to_var.py

# List the installed modules, showing priority and HLL
$ semodule --list=full
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