*cloud - FileLink for Nextcloud OpenCloud ownCloud

Deutsche Dokumentation

A MailExtension for Thunderbird (115+) that uploads large attachments to your cloud and generates a link you can send by mail instead of the file.

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Information for cloud administrators

What You'll Need (Requirements)

1. Thunderbird 115.0 or newer

2. An account on a server running Nextcloud, OpenCloud or ownCloud:

   • Nextcloud version 32 or newer (older versions might work, but are not supported by Nextcloud)
   • OpenCloud version 3.5 or newer (older versions might work, but have not been tested).
   • ownCloud Classic version 10.0.10 or newer.
   • ownCloud Infinite Scale (oCIS) version 5 or newer (older versions might work, but are not supported by ownCloud)
     Caution: You will need some help from your administrator as oCIS does not support *cloud by default.

   If you can't or don't want to run your own server, many companies offer to run it for you as a hosted service:

   • List of Nextcloud providers
   • List of OpenCloud providers
   • List of ownCloud providers

Install

1. Go to Preferences -> Compose -> Attachments
2. Click the link "Find more providers..." at the bottom of the page.
3. Find *cloud in the list and click the "Add to Thunderbird" button.

Configure

1. In thunderbird go to Preferences -> Compose -> Attachments
2. Click the button "Add *cloud".
3. Only three settings are strictly necessary:
   • Server-URL
   • Username
   • App Token (or password)

Getting an App Token for Nextcloud or ownCloud Classic

1. Open your Nextcloud or ownCloud Classic account in the browser
2. Go to Settings -> Security -> App Token
3. At the bottom of the page generate a new token.
4. Copy&paste it into the "App Token" field of the *cloud preferences page in Thunderbird.
5. Also copy the username into the *cloud preferences page in Thunderbird. It might differ from your login username.

Getting an App Token for OpenCloud

1. Open your OpenCloud account in the browser
2. Go to Preferences -> App Tokens
3. Click the "+ New" button
4. Put a name into the "Note" field (eg. "*cloud") and choose an expiration date for the App Token
5. Copy the App Token from the next dialog and paste it into the "App Token" field of the *cloud preferences page in Thunderbird.

Getting an App Token for ownCloud Infinite Scale (oCIS)

1. Open your oCIS account in the browser
2. Click on the "Application Switcher" in top left corner, left of the ownCloud logo
3. Choose "App Tokens"
   If this option is missing from the Applications menu, ask your cloud administrator to install the "App Tokens" app from the oCIS App Store.
4. Click the "Create" button
5. Copy the App Token in the next dialog and paste it into the "App Token" field of the *cloud preferences page in Thunderbird.

Automatic App Token for Nextcloud

With Nextcloud *cloud will try to obtain an App Token for you:

1. Put your user password into the "App Token" field of the *cloud preferences page in Thunderbird.
2. Click "Save". *cloud will try to get a token from your Nextcloud and use it instead of your password. You will notice the change, because afterwards the password field is filled with dots completely (app tokens are quite long).

Use

After you have added at least one account there are three ways to start the upload:

1. Add an attachment that is larger than the upload threshold. Thunderbird will then show a yellow notification bar at the bottom of the message window with a "Link" button. To get this button for smaller attachments you can change the threshold: Go to Preferences -> Compose -> Attachments and change the value "Offer to share...".
2. In the message window in the attachments menu (downward arrow in the "Attach" button), there is an entry "Filelink". It lets you choose a file and uploads it immediately.
3. After you added an attachment you can choose "Convert to..." from that attachments context menu (right click on the attachment).

Known issues

Files are uploaded correctly but sharing fails

Cause 1: Nextcloud's sharing limit

By default, Nextcloud allows a user to create at most 20 share links within any 10-minute interval. If you send emails with many attachments in a short time, this limit may be reached.

Solution: Ask your cloud administrator to raise the limit. A section in the cloud admin documentation explains how to change the limit.

Cause 2: Invalid download password

The download password has to comply with all the rules for passwords on your cloud, otherwise the upload will fail. There are default rules of Nextcloud, OpenCloud and ownCloud, and your admin might have configured some different rules.

Cause 3: Server misconfiguration

Sharing problems man also be caused by a misconfiguration of the cloud server. Please point your cloud admin to the section on Apache and mod_rewrite in the cloud admin documentation.

Incorrect links for almost identical files

If you share a file that has

• the same name and
• identical size and
• identical modification time (to the second)

as a file that has been shared before, *cloud considers this to be the same file and does not upload it again. Instead, *cloud creates a share link to the first file.

If you've got files that are the same in these three ways but have different content, this can lead to the wrong file being shared. This could happen, for example, if you use a program that generates several files in different folders quickly.

At the moment, the only solution is to change the file names or set different modification times (use the touch command on Unix systems).

You don't like the text/HTML/links inserted into the message

Many users would like to change the text that is inserted into the message along with the download url, eg add the expiration date, change the cloud service link, remove some of the text or style the HTML less prominently. Addons like *cloud have no chance to do that, because the template text surrounding the url is part of Thunderbird. The Addon only supplies the url, Thunderbird wraps its template around it and inserts the whole thing into your message.

URL works in browser but not in *cloud

In some situations the url you use to access your Nextcloud/OpenCloud/ownCloud account in the browser doesn't work as the server URL in *cloud.

Cause 1: Redirect

If your access url is redirected to the actual cloud location (plus some technicality), *cloud can't find the actual url.

If this happens to you, point *cloud to the actual cloud location:

1. Open your cloud in a browser.
2. Log in.
3. Depending on your cloud version you now have different views:
   • In Nextcloud you see the "Dashboard", just continue to the next step.
   • In Opencloud, ownCloud Classic and ownCloud Infinite Scale your see the "Files" app. Continue to the next step.
   • If you are neither in the "Dashboard" nor the "Files" app, click on the folder icon in the cloud's top menu to go to the "Files" app.
4. Copy the complete url from the url bar of your browser
5. Paste it into the server url field in *cloud's configuration (in Thunderbird).

As soon as you save the settings, *cloud will remove unnecessary parts.

Cause 2: https certificate

If the admin of your cloud used something called a "self signed certificate", Thunderbird (not *cloud) refuses to connect to the server. There are two solutions:

1. (preferred) Tell your admin about the problem. She might install another type of certificate, which Thunderbird accepts.
2. (if 1. is not possible) Force Thunderbird to accept the certificate:
   1. Open Thunderbird's preferences
   2. Go to "Privacy & Security"
   3. Scroll down to "Certificates"
   4. Click on "Manage Certificates"
   5. Choose "Servers"
   6. Click on "Add Exception"
   7. Enter your cloud's address in the "Location" field
   8. Click "Get Certificate"
   9. Click "Confirm Security Exception"

Still not working?

If things still don't work, I'd appreciate a problem report by email. Thanks.

Good to know

Download passwords

If you use download passwords, don't put them into an email, but give them to the recipient via a separate, secure channel eg a messenger or a telephone call.

Why? As a security measure the generated download links contain a long, almost random part. So an attacker (let's call her Eve) can't guess the link for a file or scan all possible links to find a file. The only reasonable way for Eve to gain access to your file is to intercept the email. (If you are interested in technical details, read this post).

So the links are fairly secure by themselves and quite comfortable for the recipient, because she only has to click the link.

If you use download passwords, never put them into the same email as the link. Because if Eve can read the link, she can also read the password. So a download password in the same email doesn't make the transfer more secure, but only more complicated for the recipient. The same goes for a separate email with the password: If Eve can intercept the first email with the link, she is very probably also able to intercept the second email.

Handling of existing files

If you attach a file that's already in the attachments folder in your cloud with identical contents, that file is not uploaded again. Instead the existing file is shared.

To make this possible, *cloud never deletes files in your cloud. Over time your attachments folder may grow to considerable size. It's safe to delete old attachments. Your admin may automate that, using "Flows" in Nextcloud or ownCloud Classic.

You can use this behavior if you want to share large (or many) files: Sync your attachments folder to a folder on your computer using the desktop client. If you then attach a synced file from your computer to a message, *cloud will notice that it's already uploaded.

If you attach a file with the same name but different contents as a cloud file, the cloud file will not be overwritten. Instead *cloud moves the existing file to a subfolder of the attachments folder; the original share link will remain valid and point to the old content.
Then the new file is uploaded and shared with a new share link.

*cloud uses a similar method as the Nextcloud/OpenCloud/ownCloud desktop clients to decide if the local and remote files are identical:

• identical name and
• identical size (in bytes) and
• last modification within the same second.

Contributions

• Johannes Endres, initial implementation, maintainer
• Josep Manel Mendoza, Catalan and Spanish localizations
• Gorom, French localization
• Jun Futagawa, implementation of generated random passwords
• Lionel Elie Mamane, solution of the LDAP/getapppassword problem
• Óvári, Hungarian localization
• Pietro Federico Sacchi, Italian localization
• Asier Iturralde Sarasola, Basque localization
• Anatolii Balbutckii, Russian localization
• Aleš Petržík, Czech localization
• mixneko, traditional Chinese localization
• Based on FileLink Provider for Dropbox by Geoff Lankow
• Inspired by Nextcloud for Filelink by Olivier Paroz and Guillaume Viguier-Just.
• Thanks to @JasonBayton for his Nextcloud demo servers of many (old) versions, that helped in the initial testing a lot.
• Contains punycode.js, Copyright Mathias Bynens, MIT license
• Contains photon-components-web