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seclabel: extend XML to allow per-disk label overrides

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When doing security relabeling, there are cases where a per-file
override might be appropriate.  For example, with a static label
and relabeling, it might be appropriate to skip relabeling on a
particular disk, where the backing file lives on NFS that lacks
the ability to track labeling.  Or with dynamic labeling, it might
be appropriate to use a custom (non-dynamic) label for a disk
specifically intended to be shared across domains.

The new XML resembles the top-level <seclabel>, but with fewer
options (basically relabel='no', or <label>text</label>):

<domain ...>
  ...
  <devices>
    <disk type='file' device='disk'>
      <source file='/path/to/image1'>
        <seclabel relabel='no'/> <!-- override for just this disk -->
      </source>
      ...
    </disk>
    <disk type='file' device='disk'>
      <source file='/path/to/image1'>
        <seclabel relabel='yes'> <!-- override for just this disk -->
          <label>system_u:object_r:shared_content_t:s0</label>
        </seclabel>
      </source>
      ...
    </disk>
    ...
  </devices>
  <seclabel type='dynamic' model='selinux'>
    <baselabel>text</baselabel> <!-- used for all devices without override -->
  </seclabel>
</domain>

This patch only introduces the XML and documentation; future patches
will actually parse and make use of it.  The intent is that we can
further extend things as needed, adding a per-device <seclabel> in
more places (such as the source of a console device), and possibly
allowing a <baselabel> instead of <label> for labeling where we want
to reuse the cNNN,cNNN pair of a dynamically labeled domain but a
different base label.

First suggested by Daniel P. Berrange here:
https://www.redhat.com/archives/libvir-list/2011-December/msg00258.html

* docs/schemas/domaincommon.rng (devSeclabel): New define.
(disk): Use it.
* docs/formatdomain.html.in (elementsDisks, seclabel): Document
the new XML.
* tests/qemuxml2argvdata/qemuxml2argv-seclabel-dynamic-override.xml:
New test, to validate RNG.
This commit is contained in:
Eric Blake 2011-12-22 17:47:49 -07:00 committed by Daniel Veillard
parent e83837945c
commit 6cb4acce8b
3 changed files with 91 additions and 7 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

29
docs/formatdomain.html.in
View File

@ -947,7 +947,9 @@
&lt;devices&gt;
&lt;disk type='file' snapshot='external'&gt;
&lt;driver name="tap" type="aio" cache="default"/&gt;
&lt;source file='/var/lib/xen/images/fv0' startupPolicy='optional'/&gt;
&lt;source file='/var/lib/xen/images/fv0'/ startupPolicy='optional'&gt;
&lt;seclabel relabel='no'/&gt;
&lt;/source&gt;
&lt;target dev='hda' bus='ide'/&gt;
&lt;iotune&gt;
&lt;total_bytes_sec&gt;10000000&lt;/total_bytes_sec&gt;
@ -1023,7 +1025,11 @@
path to the file holding the disk. If the disk
<code>type</code> is "block", then the <code>dev</code>
attribute specifies the path to the host device to serve as
the disk. If the disk <code>type</code> is "dir", then the
the disk. With both "file" and "block", an optional
sub-element <code>seclabel</code>, <a href="#seclabel">described
below</a> (and <span class="since">since 0.9.9</span>), can be
used to override the domain security labeling policy for just
that source file. If the disk <code>type</code> is "dir", then the
<code>dir</code> attribute specifies the fully-qualified path
to the directory to use as the disk. If the disk <code>type</code>
is "network", then the <code>protocol</code> attribute specifies
@ -1031,7 +1037,7 @@
are "nbd", "rbd", and "sheepdog". If the <code>protocol</code>
attribute is "rbd" or "sheepdog", an additional
attribute <code>name</code> is mandatory to specify which
image to be used. When the disk <code>type</code> is
image will be used. When the disk <code>type</code> is
"network", the <code>source</code> may have zero or
more <code>host</code> sub-elements used to specify the hosts
to connect.
@ -3372,11 +3378,11 @@ qemu-kvm -net nic,model=? /dev/null
With static label assignment, by default, the administrator
or application must ensure labels are set correctly on any
resources, however, automatic relabeling can be enabled
if desired
if desired.
</p>
<p>
Valid input XML configurations for the security label
Valid input XML configurations for the top-level security label
are:
</p>
@ -3435,6 +3441,19 @@ qemu-kvm -net nic,model=? /dev/null
</dd>
</dl>
<p>When relabeling is in effect, it is also possible to fine-tune
the labeling done for specific source file names, by either
disabling the labeling (useful if the file lives on NFS or other
file system that lacks security labeling) or requesting an
alternate label (useful when a management application creates a
special label to allow sharing of some, but not all, resources
between domains), <span class="since">since 0.9.9</span>. When
a <code>seclabel</code> element is attached to a specific path
rather than the top-level domain assignment, only the
attribute <code>relabel</code> or the
sub-element <code>label</code> are supported.
</p>
<h2><a name="examples">Example configs</a></h2>
<p>

29
docs/schemas/domaincommon.rng
View File

@ -116,6 +116,27 @@
</choice>
</element>
</define>
<define name="devSeclabel">
<element name="seclabel">
<!-- A per-device seclabel override is more limited, either
relabel=no or a <label> must be present. -->
<choice>
<attribute name='relabel'>
<value>no</value>
</attribute>
<group>
<optional>
<attribute name='relabel'>
<value>yes</value>
</attribute>
</optional>
<element name='label'>
<text/>
</element>
</group>
</choice>
</element>
</define>
<define name="hvs">
<attribute name="type">
<choice>
@ -795,7 +816,9 @@
<optional>
<ref name="startupPolicy"/>
</optional>
<empty/>
<optional>
<ref name='devSeclabel'/>
</optional>
</element>
</optional>
<ref name="diskspec"/>
@ -811,7 +834,9 @@
<attribute name="dev">
<ref name="absFilePath"/>
</attribute>
<empty/>
<optional>
<ref name='devSeclabel'/>
</optional>
</element>
</optional>
<ref name="diskspec"/>

40
tests/qemuxml2argvdata/qemuxml2argv-seclabel-dynamic-override.xml Normal file
View File

@ -0,0 +1,40 @@
<domain type='qemu'>
<name>QEMUGuest1</name>
<uuid>c7a5fdbd-edaf-9455-926a-d65c16db1809</uuid>
<memory>219100</memory>
<currentMemory>219100</currentMemory>
<vcpu cpuset='1-4,8-20,525'>1</vcpu>
<os>
<type arch='i686' machine='pc'>hvm</type>
<boot dev='hd'/>
</os>
<clock offset='utc'/>
<on_poweroff>destroy</on_poweroff>
<on_reboot>restart</on_reboot>
<on_crash>destroy</on_crash>
<devices>
<emulator>/usr/bin/qemu</emulator>
<disk type='block' device='disk'>
<source dev='/dev/HostVG/QEMUGuest1'>
<seclabel relabel='no'/>
</source>
<target dev='hda' bus='ide'/>
<address type='drive' controller='0' bus='0' unit='0'/>
</disk>
<disk type='block' device='disk'>
<source dev='/dev/HostVG/QEMUGuest2'>
<seclabel relabel='yes'>
<label>system_u:system_r:public_content_t:s0</label>
</seclabel>
</source>
<target dev='hdb' bus='ide'/>
<readonly/>
<address type='drive' controller='0' bus='0' unit='0'/>
</disk>
<controller type='ide' index='0'/>
<memballoon model='virtio'/>
</devices>
<seclabel type='dynamic' model='selinux' relabel='yes'>
<baselabel>system_u:system_r:svirt_custom_t:s0</baselabel>
</seclabel>
</domain>