mirror of
https://github.com/moparisthebest/xeps
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153 lines
6.4 KiB
XML
153 lines
6.4 KiB
XML
<?xml version='1.0' encoding='UTF-8'?>
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<!DOCTYPE xep SYSTEM 'xep.dtd' [
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<!ENTITY % ents SYSTEM 'xep.ent'>
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%ents;
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]>
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<?xml-stylesheet type='text/xsl' href='xep.xsl'?>
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<xep>
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<header>
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<title>File metadata element</title>
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<abstract>This specification defines a generic file metadata element to be used in other specifications.</abstract>
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&LEGALNOTICE;
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<number>0446</number>
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<status>Experimental</status>
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<type>Standards Track</type>
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<sig>Standards</sig>
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<approver>Council</approver>
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<dependencies>
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<spec>XMPP Core</spec>
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<spec>XEP-0001</spec>
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<spec>XEP-0082</spec>
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<spec>XEP-0264</spec>
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<spec>XEP-0300</spec>
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</dependencies>
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<supersedes/>
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<supersededby/>
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<shortname>file-metadata</shortname>
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&larma;
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<revision>
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<version>0.1.0</version>
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<date>2020-11-24</date>
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<initials>XEP Editor (jsc)</initials>
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<remark>Accepted by vote of Council on 2020-11-18.</remark>
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</revision>
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<revision>
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<version>0.0.1</version>
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<date>2020-11-03</date>
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<initials>lmw</initials>
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<remark><p>First draft.</p></remark>
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</revision>
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</header>
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<section1 topic='Introduction' anchor='intro'>
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<p>
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Several existing specification have the need to provide metadata on a file.
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The only specification of an element that contains file metadata so far is
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provided as part of &xep0234;. This resulted in the situation that XEPs like
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&xep0385; depend on the mostly unrelated &xep0166; just for the metadata
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element. The motiviation of this XEP is to get rid of such dependencies and
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have a dedicated place to define a file metadata element.
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</p>
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</section1>
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<section1 topic='Element format' anchor='format'>
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<code><![CDATA[
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<file xmlns='urn:xmpp:file:metadata:0'>
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<media-type>text/plain</media-type>
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<name>test.txt</name>
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<date>2015-07-26T21:46:00+01:00</date>
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<size>6144</size>
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<hash xmlns='urn:xmpp:hashes:2'
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algo='sha-1'>w0mcJylzCn+AfvuGdqkty2+KP48=</hash>
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</file>]]></code>
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<p>The child elements of the <file/> element are as follows:</p>
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<table caption='File Description Elements'>
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<tr>
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<th>Element Name</th>
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<th>Description</th>
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<th>Example</th>
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</tr>
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<tr>
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<td>date</td>
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<td>Timestamp specifying the last modified time of the file (which MUST conform to the DateTime profile of &xep0082;).</td>
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<td><tt>2015-07-26T21:46:00+01:00</tt></td>
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</tr>
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<tr>
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<td>dimensions</td>
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<td>Horizontal and vertical dimensions of image or video files, in pixels.</td>
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<td><tt>1920x1080</tt></td>
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</tr>
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<tr>
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<td>desc</td>
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<td>A human readable description of the file. Multiple <tt><desc/></tt> elements MAY be included if different xml:lang values are specified.</td>
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<td><tt>Picture of 24th XSF Summit</tt></td>
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</tr>
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<tr>
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<td>hash</td>
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<td>A hash of the file content, using the <tt><hash/></tt> element defined in &xep0300; and qualifed by the 'urn:xmpp:hashes:2' namespace. Multiple hashes MAY be included for hash agility.</td>
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<td><em>see specification</em></td>
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</tr>
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<tr>
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<td>length</td>
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<td>Length of an audio or video file, in milliseconds.</td>
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<td><tt>63000</tt></td>
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</tr>
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<tr>
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<td>media-type</td>
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<td>The media type of the file content, which SHOULD be a valid MIME-TYPE as registered with &IANA; (specifically, as listed at <<link url='http://www.iana.org/assignments/media-types'>http://www.iana.org/assignments/media-types</link>>). If not specified, the content is assumed to be "application/octet-stream".</td>
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<td><tt>text/plain</tt></td>
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</tr>
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<tr>
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<td>name</td>
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<td>The name of the file. The name SHOULD NOT contain characters or character sequences that would be interpreted as a directory structure by the local file system (e.g. "/", "\", "../", etc.). If any such characters or character sequences are present (possibly because the local and remote file systems use different syntax for directory structure), they SHOULD be escaped (e.g., via percent-encoding) before using the name as part of any file system operation. See <link url='#security'>Security Considerations</link>.</td>
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<td><tt>text.txt</tt></td>
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</tr>
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<tr>
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<td>size</td>
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<td>The length of the file's content, in bytes.</td>
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<td><tt>6144</tt></td>
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</tr>
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<tr>
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<td>thumbnail</td>
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<td>A thumbnail element of the file, using the <thumbnail/> element defined in &xep0264; and qualified by the 'urn:xmpp:thumbs:1' namespace. Multiple thumbnails MAY be included for media type and size agility.</td>
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<td><em>see specification</em></td>
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</tr>
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</table>
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<p>
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All child elements are OPTIONAL, however, specifications making use of the
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file metadata object MAY require providing some of these elements as part
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of their specification.
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</p>
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</section1>
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<section1 topic='Security Considerations' anchor='security'>
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<p>
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Caution needs to be exercised when using the <tt><name/></tt> of the metadata
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to control any interaction with a file system. For example, a malicious
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user could request a file with <tt><name>/etc/passwd</name></tt> or
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include file system specific control patterns such as
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<tt><name>../../private.txt</name></tt> to try and access a sensitive
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file outside of the set of files intended to be shared. Or a malicious user
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could offer a file named <tt>/etc/passwd</tt> to try and trick the receiver into
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overwriting that or other sensitive files. Therefore, implementations
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SHOULD escape any file system path separators in the <tt><name/></tt> before
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using that value in any file system calls.
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</p>
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<p>
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It is RECOMMENDED for implementations to use the strongest hashing
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algorithm available to both parties. See &xep0300; for further discussion.
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</p>
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</section1>
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<section1 topic='IANA Considerations' anchor='iana'>
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<p>This document requires no interaction with &IANA;.</p>
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</section1>
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<section1 topic='XMPP Registrar Considerations' anchor='registrar'>
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<section2 topic='Protocol Namespaces' anchor='ns'>
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<p>The ®ISTRAR; includes 'urn:xmpp:file:metadata:0' in its registry of protocol namespaces (see &NAMESPACES;).</p>
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<ul>
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<li>urn:xmpp:file:metadata:0</li>
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</ul>
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</section2>
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</section1>
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<section1 topic='Acknowledgements' anchor='ack'>
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<p>Thanks to the authors of &xep0234; which heavily inspired this XEP.</p>
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</section1>
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</xep>
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