add selinux plugin

This patch adds an selinux plugin that sets up an environment with
selinux turned *off* in the build chroot. How does this work? From the
author's description:

It is done the same as the patch sent by Thomas Liu in bz 614440 does.
Actually, this proceeding was suggested by Dan Walsh in bz 573111.

1.) Fake /proc/filesystems is created in conf["cachedir"]. It includes the
same content as the same file in host environment, except line with selinuxfs.
This file is bind mounted into build environment.

2.) Option '--setopt=tsflags=nocontext' is added to yum commands. This is done
by wrapping mock.util.do with _selinuxDoYum in "preyum" hook. This function
just adds the option and passes the command to original mock.util.do function.
The wrapping is removed in "postyum" hook.
I didn't find cleaner method, without modifying main code.

Signed-off-by: Clark Williams <williams@redhat.com>

3 files changed, 103 insertions, 2 deletions

diff --git a/Makefile.am b/Makefile.am
index ca05ec6..b9ef2fa 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -47,7 +47,9 @@ plugins_PYTHON = \
     py/mock/plugins/ccache.py     \
     py/mock/plugins/root_cache.py \
     py/mock/plugins/tmpfs.py \
-    py/mock/plugins/yum_cache.py
+    py/mock/plugins/yum_cache.py \
+    py/mock/plugins/selinux.py
+
 
 pkgpython_PYTHON = \
     py/mock/__init__.py        \
diff --git a/py/mock.py b/py/mock.py
index dd002de..a0e585d 100755
--- a/py/mock.py
+++ b/py/mock.py
@@ -244,7 +244,7 @@ def setup_default_config_opts(config_opts, unprivUid):
     #    root_cache next.
     #    after that, any plugins that must create dirs (yum_cache)
     #    any plugins without preinit hooks should be last.
-    config_opts['plugins'] = ('tmpfs', 'root_cache', 'yum_cache', 'bind_mount', 'ccache')
+    config_opts['plugins'] = ('tmpfs', 'root_cache', 'yum_cache', 'bind_mount', 'ccache', 'selinux')
     config_opts['plugin_dir'] = os.path.join(PKGPYTHONDIR, "plugins")
     config_opts['plugin_conf'] = {
             'ccache_enable': True,
@@ -273,6 +273,8 @@ def setup_default_config_opts(config_opts, unprivUid):
             'tmpfs_opts': {
                 'required_ram_mb': 900,
                 'max_fs_size': None},
+            'selinux_enable': True,
+            'selinux_opts': {},
             }
 
     # dependent on guest OS
diff --git a/py/mock/plugins/selinux.py b/py/mock/plugins/selinux.py
new file mode 100644
index 0000000..6d15a94
--- /dev/null
+++ b/py/mock/plugins/selinux.py
@@ -0,0 +1,97 @@
+# vim:expandtab:autoindent:tabstop=4:shiftwidth=4:filetype=python:textwidth=0:
+# License: GPL2 or later see COPYING
+# Written by Jan Vcelak
+# Copyright (C) 2010 Jan Vcelak <jvcelak@redhat.com>
+
+# python library imports
+import os
+import sys
+
+# our imports
+from mock.trace_decorator import decorate, traceLog, getLog
+import mock.util
+
+requires_api_version = "1.0"
+
+# plugin entry point
+decorate(traceLog())
+def init(rootObj, conf):
+    if mock.util.selinuxEnabled():
+        getLog().info("selinux enabled")
+        SELinux(rootObj, conf)
+    else:
+        getLog().info("selinux disabled")
+
+# classes
+class SELinux(object):
+    """On SELinux enabled box, this plugin will pretend, that SELinux is disabled in build environment.
+
+       - fake /proc/filesystems is mounted into build enviroment, excluding selinuxfs
+       - option '--setopt=tsflags=nocontext' is appended to each 'yum' command
+    """
+
+    decorate(traceLog())
+    def __init__(self, rootObj, conf):
+        self.rootObj = rootObj
+        self.conf = conf
+
+        self.filesystems = os.path.join(conf["cachedir"], "filesystems")
+        self.chrootFilesystems = rootObj.makeChrootPath("/proc/filesystems")
+
+        rootObj.addHook("preinit", self._selinuxPreInitHook)
+        rootObj.addHook("postbuild", self._selinuxPostBuildHook)
+        rootObj.addHook("initfailed", self._selinuxPostBuildHook)
+        if self._selinuxYumIsSetoptSupported():
+            rootObj.addHook("preyum", self._selinuxPreYumHook)
+            rootObj.addHook("postyum", self._selinuxPostYumHook)
+        else:
+            getLog().warn("selinux: 'yum' does not support '--setopt' option")
+
+    decorate(traceLog())
+    def _selinuxPreInitHook(self):
+        host = open("/proc/filesystems")
+        build = open(self.filesystems, "w")
+
+        for line in host:
+            if not "selinuxfs" in line:
+                build.write(line)
+
+        build.close()
+        host.close()
+
+        self.rootObj.mountCmds.append("mount -n --bind %s %s" % (self.filesystems, self.chrootFilesystems))
+        self.rootObj.umountCmds.insert(0, "umount -n %s" % self.chrootFilesystems)
+
+    decorate(traceLog())
+    def _selinuxPostBuildHook(self):
+        os.unlink(self.filesystems)
+
+    decorate(traceLog())
+    def _selinuxPreYumHook(self):
+        self._originalUtilDo = mock.util.do
+        mock.util.do = self._selinuxDoYum
+
+    decorate(traceLog())
+    def _selinuxPostYumHook(self):
+        mock.util.do = self._originalUtilDo
+
+    decorate(traceLog())
+    def _selinuxDoYum(self, command, *args, **kargs):
+        option = "--setopt=tsflags=nocontexts"
+
+        if type(command) is list:
+            command.append(option)
+        elif type(command) is str:
+            command += " %s" % option
+
+        return self._originalUtilDo(command, *args, **kargs)
+
+    decorate(traceLog())
+    def _selinuxYumIsSetoptSupported(self):
+        # ugly hack: discover, whether yum supports --setopt option
+        sys.path.insert(0, '/usr/share/yum-cli')
+        import cli
+        supported = hasattr(cli.YumBaseCli, "_parseSetOpts")
+        sys.path.pop(0)
+
+        return supported