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c4eedd7930
The encryption was buggy and qemu actually dropped it upstream. Forbid it for all versions since it would cause other problems too. Problems with the old encryption include weak crypto, corruption of images with blockjobs and a lot of usability problems. This requires changing of the encryption type for the encrypted disk tests. Signed-off-by: Peter Krempa <pkrempa@redhat.com> Reviewed-by: Ján Tomko <jtomko@redhat.com>
168 lines
7.1 KiB
XML
168 lines
7.1 KiB
XML
<?xml version="1.0" encoding="UTF-8"?>
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<!DOCTYPE html>
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<html xmlns="http://www.w3.org/1999/xhtml">
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<body>
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<h1>Storage volume encryption XML format</h1>
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<ul id="toc"></ul>
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<h2><a id="StorageEncryption">Storage volume encryption XML</a></h2>
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<p>
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Storage volumes may be encrypted, the XML snippet described below is used
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to represent the details of the encryption. It can be used as a part
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of a domain or storage configuration.
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</p>
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<p>
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The top-level tag of volume encryption specification
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is <code>encryption</code>, with a mandatory
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attribute <code>format</code>. Currently defined values
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of <code>format</code> are <code>default</code>, <code>qcow</code>,
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and <code>luks</code>.
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Each value of <code>format</code> implies some expectations about the
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content of the <code>encryption</code> tag. Other format values may be
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defined in the future.
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</p>
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<p>
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The <code>encryption</code> tag can currently contain a sequence of
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<code>secret</code> tags, each with mandatory attributes <code>type</code>
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and either <code>uuid</code> or <code>usage</code>
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(<span class="since">since 2.1.0</span>). The only currently defined
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value of <code>type</code> is <code>volume</code>. The
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<code>uuid</code> is "uuid" of the <code>secret</code> while
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<code>usage</code> is the "usage" subelement field.
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A secret value can be set in libvirt by the
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<a href="html/libvirt-libvirt-secret.html#virSecretSetValue">
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<code>virSecretSetValue</code></a> API. Alternatively, if supported
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by the particular volume format and driver, automatically generate a
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secret value at the time of volume creation, and store it using the
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specified <code>uuid</code>.
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</p>
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<h3><a id="StorageEncryptionDefault">"default" format</a></h3>
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<p>
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<code><encryption format="default"/></code> can be specified only
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when creating a qcow volume. If the volume is successfully created, the
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encryption formats, parameters and secrets will be auto-generated by
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libvirt and the attached <code>encryption</code> tag will be updated.
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The unmodified contents of the <code>encryption</code> tag can be used
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in later operations with the volume, or when setting up a domain that
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uses the volume.
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</p>
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<h3><a id="StorageEncryptionQcow">"qcow" format</a></h3>
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<p>
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The <code>qcow</code> format specifies that the built-in encryption
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support in <code>qcow</code>- or <code>qcow2</code>-formatted volume
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images should be used. A single
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<code><secret type='passphrase'></code> element is expected. Note
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that this encryption is inherently broken and should not be used any more.
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</p>
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<h3><a id="StorageEncryptionLuks">"luks" format</a></h3>
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<p>
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The <code>luks</code> format is specific to a luks encrypted volume
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and the secret is used in order to either encrypt during volume creation
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or decrypt the volume for usage by the domain. A single
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<code><secret type='passphrase'...></code> element is expected.
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<span class="since">Since 2.1.0</span>.
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</p>
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<p>
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For volume creation, it is possible to specify the encryption
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algorithm used to encrypt the luks volume. The following two
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optional elements may be provided for that purpose. It is hypervisor
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dependent as to which algorithms are supported. The default algorithm
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used by the storage driver backend when using qemu-img to create
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the volume is 'aes-256-cbc' using 'essiv' for initialization vector
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generation and 'sha256' hash algorithm for both the cipher and the
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initialization vector generation.
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</p>
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<dl>
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<dt><code>cipher</code></dt>
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<dd>This element describes the cipher algorithm to be used to either
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encrypt or decrypt the luks volume. This element has the following
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attributes:
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<dl>
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<dt><code>name</code></dt>
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<dd>The name of the cipher algorithm used for data encryption,
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such as 'aes', 'des', 'cast5', 'serpent', 'twofish', etc.
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Support of the specific algorithm is storage driver
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implementation dependent.</dd>
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<dt><code>size</code></dt>
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<dd>The size of the cipher in bits, such as '256', '192', '128',
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etc. Support of the specific size for a specific cipher is
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hypervisor dependent.</dd>
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<dt><code>mode</code></dt>
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<dd>An optional cipher algorithm mode such as 'cbc', 'xts',
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'ecb', etc. Support of the specific cipher mode is
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hypervisor dependent.</dd>
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<dt><code>hash</code></dt>
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<dd>An optional master key hash algorithm such as 'md5', 'sha1',
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'sha256', etc. Support of the specific hash algorithm is
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hypervisor dependent.</dd>
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</dl>
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</dd>
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<dt><code>ivgen</code></dt>
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<dd>This optional element describes the initialization vector
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generation algorithm used in conjunction with the
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<code>cipher</code>. If the <code>cipher</code> is not provided,
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then an error will be generated by the parser.
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<dl>
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<dt><code>name</code></dt>
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<dd>The name of the algorithm, such as 'plain', 'plain64',
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'essiv', etc. Support of the specific algorithm is hypervisor
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dependent.</dd>
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<dt><code>hash</code></dt>
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<dd>An optional hash algorithm such as 'md5', 'sha1', 'sha256',
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etc. Support of the specific ivgen hash algorithm is hypervisor
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dependent.</dd>
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</dl>
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</dd>
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</dl>
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<h2><a id="example">Examples</a></h2>
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<p>
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Here is a simple example, specifying use of the <code>qcow</code> format:
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</p>
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<pre>
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<encryption format='qcow'>
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<secret type='passphrase' uuid='c1f11a6d-8c5d-4a3e-ac7a-4e171c5e0d4a' />
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</encryption></pre>
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<p>
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Assuming a <a href="formatsecret.html#VolumeUsageType">
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<code>luks volume type secret</code></a> is already defined,
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a simple example specifying use of the <code>luks</code> format
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for either volume creation without a specific cipher being defined or
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as part of a domain volume definition:
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</p>
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<pre>
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<encryption format='luks'>
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<secret type='passphrase' uuid='f52a81b2-424e-490c-823d-6bd4235bc572'/>
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</encryption>
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</pre>
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<p>
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Here is an example specifying use of the <code>luks</code> format for
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a specific cipher algorithm for volume creation:
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</p>
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<pre>
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<volume>
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<name>twofish.luks</name>
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<capacity unit='G'>5</capacity>
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<target>
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<path>/var/lib/libvirt/images/demo.luks</path>
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<format type='raw'/>
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<encryption format='luks'>
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<secret type='passphrase' uuid='f52a81b2-424e-490c-823d-6bd4235bc572'/>
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<cipher name='twofish' size='256' mode='cbc' hash='sha256'/>
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<ivgen name='plain64' hash='sha256'/>
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</encryption>
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</target>
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</volume>
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</pre>
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</body>
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</html>
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