106 lines
4.5 KiB
Markdown
106 lines
4.5 KiB
Markdown
# File Upload Notification
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## Introduction
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When sending files relevant to a current discussion, it sometimes happens that the conversation
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moves on while waiting for the file to be uploaded, for example by using [HTTP-Upload](https://xmpp.org/extensions/xep-0363.html).
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This causes the file to be sent at a later date.
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File Upload Notifications are a way to allow supporting clients to place a pseudo-message
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that will be replaced once the file has been uploaded.
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## Pre-Upload
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```xml
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<message from="some.user@some.server/abc123" to="someone.else@other.server" id="aaaaa">
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<file-upload xmlns="proto:urn:xmpp:fun:0">
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<file xmlns="urn:xmpp:file:metadata:0">
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<name>vacation.jpg</name>
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<media-type>image/jpeg</media-type>
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</file>
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<thumbnail type="blurhash" xmlns="proto:urn:xmpp:file-thumbnails:0">
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<blurhash>LEHV6nWB2yk8pyoJadR*.7kCMdnj</blurhash>
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</thumbnail>
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<thumbnail type="base64-bob" xmlns="proto:urn:xmpp:file-thumbnails:0">
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<base64-bob uri="cid:sha1+...@bob.xmpp.org" media-type="image/png" width="128" height="96" />
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</thumbnail>
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</file-upload>
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<origin-id xmlns="urn:xmpp:sid:0" id="ccccc" />
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<no-permanent-store xmlns="urn:xmpp:hints" />
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</message>
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```
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The `<file-upload>` element indicates that a message should be replaced with the actual
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file embed once the upload is done. Metadata about the file should be included
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as specified by [File metadata element](https://xmpp.org/extensions/xep-0446.html).
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The metadata should include only the bare minimum, i.e. the mime type and filename.
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Additionally, zero or more thumbnails can be sent with the notification in order to allow clients
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to already show a preview. The `<file-thumbnail />` element is specified by [File Thumbnails](https://github.com/PapaTutuWawa/custom-xeps/blob/master/xep-xxxx-file-thumbnails.md).
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Note that [Unique and Stable Origin IDs](https://xmpp.org/extensions/xep-0359.html) must be used when the message is sent to a
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groupchat.
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Since this message carries no meaning to anyone retrieving it after the file upload has been
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completed, a `<no-permanent-store />` element should be added (See [Message Processing Hints](https://xmpp.org/extensions/xep-0334.html)).
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## Post-Upload
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After the file upload has been completed, the sending client includes a `<replaces />` element
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in the message to inform clients which messages should be replaced.
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```xml
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<message from="some.user@some.server/abc123" to="someone.else@other.server" id="bbbbb">
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<body>...</body>
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<x xmlns="jabber:x:oob">
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<url>...</url>
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</x>
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<replaces xmlns="proto:urn:xmpp:fun:0" id="ccccc" />
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<origin-id xmlns="urn:xmpp:sid:0" id="ddddd" />
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</message>
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```
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The `id` attribute of the `<replaces />` element refers to either the stanza ID or the
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origin ID of the message that contained the original `<file-upload />`.
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If sent to a groupchat, the origin ID must be used.
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Note the the actual method of communicating a file is of no relevance here, as long as the
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method allows a client to show it inline. Examples for such methods are
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[Out of Band Data](https://xmpp.org/extensions/xep-0066.html)
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and [Stateless Inline Media Sharing](https://xmpp.org/extensions/xep-0385.html).
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In case the sender uses methods like [Stateless Inline Media Sharing](https://xmpp.org/extensions/xep-0385.html)
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or [Stateless File Sharing](https://xmpp.org/extensions/xep-0447.html) which allow specifying
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a thumbnail, then the client should do here as well to allow clients catching up using
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[Message Archive Management](https://xmpp.org/extensions/xep-0313.html) to also provide a thumbnail to their users.
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## Cancelled Upload
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If the uploading entity has cancelled the upload, then it should indicate so to the other communicating entities.
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```xml
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<message from="some.user@some.server/abc123" to="someone.else@other.server" id="bbbbb">
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<cancelled xmlns="proto:urn:xmpp:fun:0" />
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<replaces xmlns="proto:urn:xmpp:fun:0" id="ccccc" />
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<origin-id xmlns="urn:xmpp:sid:0" id="ddddd" />
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</message>
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```
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In this example, the uploading entity just sends a message containing a `<cancelled />` tag to indicate the
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cancellation, allowing receiving clients to perhaps stop showing loading spinners and the like. The
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`<replaces />` is used to indicate what original message this cancellation applies to.
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## Security Considerations
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A client receiveing a message with an `<replaces />` element must verify if the message it
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is supposed to replace was actually sent by the sender of the `<replaces />` element to
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prevent arbitrary messages to be replaced.
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## Info
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| Key | Value |
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| --- | --- |
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| Author | PapaTutuWawa |
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| Version | 0.0.4 |
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| Short name | fun |
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