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OWASP CRS - Nextcloud Rule Exclusions Plugin

Integration tests

Description

This plugin contains rule exclusions for Nextcloud, a productivity platform and file hosting service. These rule exclusions are designed to resolve common false positives and allow for easier integration with the OWASP CRS (CRS).

Supported apps

Due to how feature rich Nextcloud is, not all apps in Nextcloud can be supported (Especially 3rd party apps). False positives that are due to unsupported apps within Nextcloud must be resolved by a custom rule exclusion.

Additional apps may be supported if there is enough demand from the community, but in general, support for apps made by 3rd parties (not Nextcloud) won't be added.

App Name Status
Nextcloud Files Supported ✅
Nextcloud Photos Supported ✅
Nextcloud Calendar Supported ✅
Nextcloud Contacts Supported ✅
Nextcloud Teams (Formerly Circles) Supported ✅
Nextcloud Mail Supported ✅
Nextcloud Deck Supported ✅
Nextcloud Office Supported ✅
Nextcloud Notes Supported ✅
Nextcloud Text Editor Supported ✅
Nextcloud Recognize Supported ✅
Nextcloud Cookbook Supported ✅
Nextcloud Talk Not supported ❌
Nextcloud Forms Not supported ❌
Nextcloud Polls Not supported ❌
Nextcloud Unspash Not supported ❌
Nextcloud Collectives Not supported ❌
Nextcloud News Not supported ❌
Nextcloud Maps Not supported ❌
Cospend Not supported ❌
Breeze Dark Not supported ❌
OnlyOffice Not supported ❌
Nextcloud Tables Not supported ❌
Nextcloud Assistant Not supported ❌
ownCloud Music Not supported ❌

Installation

For full and up to date instructions for the different available plugin installation methods, refer to How to Install a Plugin in the official CRS documentation.

Conditionally enable plugins for multi-application environments

For full and up to date instructions on how to conditionally enable/disable this plugin on a multisite environment, please refer to Conditionally enable plugins for multi-application environments in the official CRS documentation.

Increasing max upload size

Large uploads can be modified with SecRequestBodyLimit. Or they can be more controlled by using the following:

Apache with ModSecurity2:

SecRule REQUEST_FILENAME "@rx (?:/index\.php/apps/files/ajax/upload\.php|/remote\.php/dav/(?:bulk|files/|uploads/))" \
    "id:9508610,\
    phase:1,\
    t:none,\
    nolog,\
    ctl:requestBodyLimit=1073741824"

ctl:requestBodyLimit is not supported in libmodsecurity3, Nginx users can increase max upload size by using the following:

location ~ (?:/index\.php/apps/files/ajax/upload\.php|/remote\.php/dav/(?:bulk|files/|uploads/)) { modsecurity_rules 'SecRequestBodyLimit 1073741824'; }

Apache libmodsecurity3 Example:

<LocationMatch "(?:/index\.php/apps/files/ajax/upload\.php|/remote\.php/dav/(?:bulk|files/|uploads/))">
    modsecurity_rules 'SecRequestBodyLimit 1073741824'
</LocationMatch>

Relaxing file upload restrictions

To relax upload restrictions for only the php files that need it, you put something like this in crs-setup.conf:

SecRule REQUEST_FILENAME "@rx /(?:remote\.php|index\.php)/" \
    "id:9508600,\
    phase:2,\
    t:none,\
    nolog,\
    pass,\
    setvar:'tx.restricted_extensions=.bak/ .config/ .conf/'"

Increasing max request body size

The Nextcloud desktop client occasionally sends large request bodies not containing any uploaded files. ModSecurity will block request bodies larger than 131KB, adjusting SecRequestBodyNoFilesLimit to 141KB works for all scenarios tested.

Nginx libmodsecurity3 Example:

location /remote.php/dav/files/ { modsecurity_rules 'SecRequestBodyNoFilesLimit 144384'; }

Apache modsecurity2 Example:

<location "/remote.php/dav/files/">
   SecRequestBodyNoFilesLimit 144384
</location>

Apache libmodsecurity3 Example:

<location "/remote.php/dav/files/">
   modsecurity_rules 'SecRequestBodyNoFilesLimit 144384'
</location>

Testing

After the plugin is enabled, Nextcloud should work without problems caused by CRS (for example, false positives while blocking requests). If problems still occur then please file a new issue on GitHub. (Note that high paranoia level deployments may require additional tuning beyond this plugin.)

License

Copyright (c) 2022-2024 OWASP CRS project. All rights reserved.

The OWASP CRS and its official plugins are distributed under Apache Software License (ASL) version 2. Please see the enclosed LICENSE file for full details.