File metadata element This specification defines a generic file metadata element to be used in other specifications. This XMPP Extension Protocol is copyright © 1999 – 2024 by the XMPP Standards Foundation (XSF). Permission is hereby granted, free of charge, to any person obtaining a copy of this specification (the "Specification"), to make use of the Specification without restriction, including without limitation the rights to implement the Specification in a software program, deploy the Specification in a network service, and copy, modify, merge, publish, translate, distribute, sublicense, or sell copies of the Specification, and to permit persons to whom the Specification is furnished to do so, subject to the condition that the foregoing copyright notice and this permission notice shall be included in all copies or substantial portions of the Specification. Unless separate permission is granted, modified works that are redistributed shall not contain misleading information regarding the authors, title, number, or publisher of the Specification, and shall not claim endorsement of the modified works by the authors, any organization or project to which the authors belong, or the XMPP Standards Foundation. ## NOTE WELL: This Specification is provided on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, express or implied, including, without limitation, any warranties or conditions of TITLE, NON-INFRINGEMENT, MERCHANTABILITY, or FITNESS FOR A PARTICULAR PURPOSE. ## In no event and under no legal theory, whether in tort (including negligence), contract, or otherwise, unless required by applicable law (such as deliberate and grossly negligent acts) or agreed to in writing, shall the XMPP Standards Foundation or any author of this Specification be liable for damages, including any direct, indirect, special, incidental, or consequential damages of any character arising from, out of, or in connection with the Specification or the implementation, deployment, or other use of the Specification (including but not limited to damages for loss of goodwill, work stoppage, computer failure or malfunction, or any and all other commercial damages or losses), even if the XMPP Standards Foundation or such author has been advised of the possibility of such damages. This XMPP Extension Protocol has been contributed in full conformance with the XSF's Intellectual Property Rights Policy (a copy of which can be found at <https://xmpp.org/about/xsf/ipr-policy> or obtained by writing to XMPP Standards Foundation, P.O. Box 787, Parker, CO 80134 USA). 0446 Experimental Standards Track Standards Council XMPP Core XEP-0001 XEP-0082 XEP-0264 XEP-0300 file-metadata Marvin Wißfeld xmpp@larma.de jabber@larma.de 0.2.0 2022-07-17 lmw Use height/width instead of dimensions 0.1.0 2020-11-24 XEP Editor (jsc) Accepted by vote of Council on 2020-11-18. 0.0.1 2020-11-03 lmw

First draft.

Several existing specification have the need to provide metadata on a file. The only specification of an element that contains file metadata so far is provided as part of Jingle File Transfer (XEP-0234) XEP-0234: Jingle File Transfer <https://xmpp.org/extensions/xep-0234.html>.. This resulted in the situation that XEPs like Stateless Inline Media Sharing (XEP-0385) XEP-0385: Stateless Inline Media Sharing (SIMS) <https://xmpp.org/extensions/xep-0385.html>. depend on the mostly unrelated Jingle (XEP-0166) XEP-0166: Jingle <https://xmpp.org/extensions/xep-0166.html>. just for the metadata element. The motiviation of this XEP is to get rid of such dependencies and have a dedicated place to define a file metadata element.

text/plain test.txt 2015-07-26T21:46:00+01:00 6144 w0mcJylzCn+AfvuGdqkty2+KP48= ]]>

The child elements of the <file/> element are as follows:

Element Name Description Example
date Timestamp specifying the last modified time of the file (which MUST conform to the DateTime profile of XMPP Date and Time Profiles (XEP-0082) XEP-0082: XMPP Date and Time Profiles <https://xmpp.org/extensions/xep-0082.html>.). 2015-07-26T21:46:00+01:00
desc A human readable description of the file. Multiple <desc/> elements MAY be included if different xml:lang values are specified. Picture of 24th XSF Summit
hash A hash of the file content, using the <hash/> element defined in Use of Cryptographic Hash Functions in XMPP (XEP-0300) XEP-0300: Use of Cryptographic Hash Functions in XMPP <https://xmpp.org/extensions/xep-0300.html>. and qualifed by the 'urn:xmpp:hashes:2' namespace. Multiple hashes MAY be included for hash agility. see specification
height Vertical dimensions of image or video files, in pixels. 1920
length Length of an audio or video file, in milliseconds. 63000
media-type The media type of the file content, which SHOULD be a valid MIME-TYPE as registered with the Internet Assigned Numbers Authority (IANA) The Internet Assigned Numbers Authority (IANA) is the central coordinator for the assignment of unique parameter values for Internet protocols, such as port numbers and URI schemes. For further information, see <http://www.iana.org/>. (specifically, as listed at <http://www.iana.org/assignments/media-types>). If not specified, the content is assumed to be "application/octet-stream". text/plain
name 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 Security Considerations. text.txt
size The length of the file's content, in bytes. 6144
thumbnail A thumbnail element of the file, using the <thumbnail/> element defined in File Transfer Thumbnails (XEP-0264) XEP-0264: File Transfer Thumbnails <https://xmpp.org/extensions/xep-0264.html>. and qualified by the 'urn:xmpp:thumbs:1' namespace. Multiple thumbnails MAY be included for media type and size agility. see specification
width Horizontal dimensions of image or video files, in pixels. 1080

All child elements are OPTIONAL, however, specifications making use of the file metadata object MAY require providing some of these elements as part of their specification.

Caution needs to be exercised when using the <name/> of the metadata to control any interaction with a file system. For example, a malicious user could request a file with <name>/etc/passwd</name> or include file system specific control patterns such as <name>../../private.txt</name> to try and access a sensitive file outside of the set of files intended to be shared. Or a malicious user could offer a file named /etc/passwd to try and trick the receiver into overwriting that or other sensitive files. Therefore, implementations SHOULD escape any file system path separators in the <name/> before using that value in any file system calls.

It is RECOMMENDED for implementations to use the strongest hashing algorithm available to both parties. See Use of Cryptographic Hash Functions in XMPP (XEP-0300) XEP-0300: Use of Cryptographic Hash Functions in XMPP <https://xmpp.org/extensions/xep-0300.html>. for further discussion.

This document requires no interaction with the Internet Assigned Numbers Authority (IANA) The Internet Assigned Numbers Authority (IANA) is the central coordinator for the assignment of unique parameter values for Internet protocols, such as port numbers and URI schemes. For further information, see <http://www.iana.org/>..

The XMPP Registrar The XMPP Registrar maintains a list of reserved protocol namespaces as well as registries of parameters used in the context of XMPP extension protocols approved by the XMPP Standards Foundation. For further information, see <https://xmpp.org/registrar/>. includes 'urn:xmpp:file:metadata:0' in its registry of protocol namespaces (see <https://xmpp.org/registrar/namespaces.html>).

  • urn:xmpp:file:metadata:0

Thanks to the authors of Jingle File Transfer (XEP-0234) XEP-0234: Jingle File Transfer <https://xmpp.org/extensions/xep-0234.html>. which heavily inspired this XEP.