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refactor(admin): Rewrite Server-Side Encryption chapter

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Updated the server-side encryption documentation.

- Reorganized and streamlined
- Improved clarity throughout
- Fixed a few outdated comments/notes
- Additional reference links
- Added context of "encryption" to help reader understand SSE in the context of other encryption solutions (both within Nextcloud and provided by their OS/etc)
- Expanded/clarified key management modes and encryption methods a bit

Signed-off-by: Josh <josh.t.richards@gmail.com>
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2025-10-05 13:23:08 -04:00
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admin_manual/configuration_files/encryption_configuration.rst
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====================================
Server-side encryption configuration
====================================
======================
Server-side Encryption
======================
The primary purpose of the Nextcloud server-side encryption is to protect users'
files on remote storage, such as Dropbox and Google Drive, and to do it easily
and seamlessly from within Nextcloud.
Overview
--------
Server-side encryption separates encryption of local and remote storage.
This allows you to encrypt remote storage, such as Dropbox and
Google, without having to also encrypt your home storage on your Nextcloud
server (en- or disable the checkbox "enabling encryption on your home
storage" in the **Server-side encryption** section of your Admin page.)
Nextcloud provides several encryption methods to protect your data. These work at
different layers of the system and address different security needs. This guide
focuses on Nextcloud's built-in Server-Side Encryption (SSE).
.. note:: Nextcloud supports Authenticated Encryption for all
newly encrypted files. See https://hackerone.com/reports/108082 for more
technical information about the impact.
For maximum security make sure to configure external storage with "Check for
changes: Never". This will let Nextcloud ignore new files not added via Nextcloud,
so a malicious external storage administrator could not add new files to the
storage without your knowledge. Of course, this is not wise if your external
storage is subject to legitimate external changes.
.. note::
Encryption and risk management is a complex and nuanced topic. Unless you are
already an expert, it is recommended to consult a professional or perform a
deep dive to ensure your approach targets your specific concerns.
You may also find this Nextcloud Blog post helpful:
`Data encryption methods in Nextcloud <https://nextcloud.com/blog/encryption-in-nextcloud/>`_.
It provides a solid high-level overview of the different approaches commonly
considered when using Nextcloud.
Nextcloud server-side encryption encrypts files stored on the Nextcloud server,
and files on remote storage that is connected to your Nextcloud server.
Encryption and decryption are performed on the Nextcloud server. All files sent
to remote storage will be encrypted by the Nextcloud server, and upon retrieval,
decrypted before serving them to you and anyone you have shared them with.
Definitions
-----------
.. note:: Encryption files generate a slight overhead in size by ~1% (35% before Nextcloud 25).
User's quotas are based on the unencrypted file size, and not the encrypted file size.
- **Server-Side Encryption (SSE):** Performed by the Nextcloud server, protecting
files at rest on local and external storage. Encryption keys are stored on the server.
- **End-to-End Encryption (E2EE):** Performed by Nextcloud desktop or mobile clients
before uploading files. Only the client can decrypt, making data inaccessible to
server administrators and external storage providers.
- **Master Key:** A central key controlled by the server, used to encrypt all files.
- **User Keys:** Each user has their own key, protected by their password, to encrypt
their files.
- **Recovery Key:** An admin-defined key to recover files if users lose their passwords.
When files on external storage are encrypted in Nextcloud, you cannot share them
directly from the external storage services, but only through Nextcloud sharing
because the key to decrypt the data never leaves the Nextcloud server.
Encryption Method Comparison
----------------------------
Nextcloud's server-side encryption generates a strong encryption key, which is
unlocked by user's passwords. Your users don't need to track an extra
password, but simply log in as they normally do. It encrypts only the contents
of files, and not filenames and directory structures.
.. list-table::
:header-rows: 1
:widths: 20 20 25 35
You should regularly backup all encryption keys to prevent permanent data loss.
The encryption keys are stored in the following directories:
* - Method
- Encryption Location
- Who Can Decrypt?
- Protects Against
* - SSE (Master Key)
- Server
- Admins & users
- External storage providers
* - SSE (User Keys)
- Server
- Users & malicious admins
- External storage providers
* - SSE (User Keys w/ Recovery)
- Server
- Users & admins with recovery key
- External storage providers
* - E2EE
- Client
- Users only
- Admins, external storage providers
* - Disk/Block Encryption
- Server
- OS admin
- Physical tampering, theft
``data/<user>/files_encryption``
Users' private keys and all other keys necessary to decrypt the users' files
``data/files_encryption``
private keys and all other keys necessary to decrypt the files stored on a
system wide external storage
When encryption is enabled, all files are encrypted and decrypted by the
Nextcloud application, and stored encrypted on your remote storage.
This protects your data on externally hosted storage. The Nextcloud
admin and the storage admin will see only encrypted files when browsing backend
storage.
.. warning:: Encryption keys are stored only on the Nextcloud server, eliminating
exposure of your data to third-party storage providers. The encryption app
does **not** protect your data if your Nextcloud server is compromised, and it
does not prevent Nextcloud administrators from reading user's files. This
would require client-side encryption, which this app does not provide. If
your Nextcloud server is not connected to any external storage services then
it is better to use other encryption tools, such as file-level or
whole-disk encryption.
Note also that SSL terminates at or before Apache on the Nextcloud server, and
all files will exist in an unencrypted state between the SSL connection
termination and the Nextcloud code that encrypts and decrypts files. This is
also potentially exploitable by anyone with administrator access to your
server. Read `How Nextcloud uses encryption to protect your data
<https://nextcloud.com/blog/encryption-in-nextcloud/>`_ for more information.
Before enabling encryption
--------------------------
Key Points & Limitations
------------------------
Plan very carefully before enabling encryption because it is not reversible via
the Nextcloud Web interface. If you lose your encryption keys your files are not
recoverable. Always have backups of your encryption keys stored in a safe
location, and consider enabling all recovery options.
- Encryption methods are not interchangeable; each is designed for specific risks.
- SSE is mainly for protecting files on external, third-party storage.
- E2EE is for scenarios where server administrators must not access data.
- SSE does **not** encrypt filenames or folder structures, only file contents.
- SSE does not protect data from a compromised Nextcloud server or malicious administrator.
Use E2EE for this threat.
- Server-Side Encryption cannot be reversed via the Nextcloud Web interface.
- Troubleshooting SSE matters generally requires ``occ`` command access. Make sure you have
it before enabling SSE!
- Losing encryption keys or your instance secret results in permanent data loss.
- Nextcloud quotas are based on unencrypted file size; encrypted files may be ~1% larger
(was 35% before Nextcloud 25).
- SSL/TLS (HTTPS) terminates before files are encrypted, so files may be exposed in memory
between SSL/TLS and Nextcloud’s encryption code.
- When files on external storage are encrypted in Nextcloud, you cannot share them directly
from the external storage provider; sharing is only possible via Nextcloud, since the
decryption key never leaves the Nextcloud server.
- For local storage, it may be better to use other encryption tools, such as disk/block device
encryption (e.g., LUKS) provided by your operating system. This protects against other concerns,
such as theft of your physical server, which is not SSE's goal.
There are two encryption mode, `master key` and `user keys`. By default, `master key` is used.
.. note::
Don't confuse Nextcloud's SSE with S3 SSE-C (also supported).
If you do not want to use a master key setup, but wish to use user key encryption
instead, please run the following command before enabling the encryption::
.. note::
Nextcloud (since v9.0.0) supports Authenticated Encryption for all newly encrypted files.
See https://hackerone.com/reports/108082 for technical details.
occ encryption:disable-master-key
.. note::
For maximum security, configure external storage with "Check for changes: Never".
This causes Nextcloud to ignore new files not added via Nextcloud, preventing unauthorized
additions by external storage admins. Do not use this if your storage is subject to legitimate
external changes.
You have more options via the ``occ`` command (see :ref:`occ_encryption_label`).
Before You Enable Encryption
----------------------------
.. _enable_encryption_label:
1. Read this guide fully and understand the risks.
2. Back up your instance configuration and all encryption keys in a safe location before proceeding.
3. Decide which key management mode suits your needs (see below).
Enabling encryption
-------------------
Key Management Modes
--------------------
Nextcloud encryption consists of two parts. The base encryption system is
enabled and disabled on your Admin page. First you must enable this, and then
select an encryption module to load. Currently the only available encryption
module is the Nextcloud Default Encryption Module.
**Master Key (default):**
First go to the **Server-side encryption** section of your Admin page and check
**Enable server-side encryption**. You have one last chance to change your mind.
- All files are encrypted with a central server-controlled key.
- Admins can decrypt any user’s files.
- Offers better performance and compatibility with more login/authentication modes.
- Best for organizations that need to recover files if users forget their passwords.
**User Keys:**
- Each user’s files are encrypted with a password-protected key.
- Admins cannot (readily) decrypt files without the user's password, unless a recovery key is defined.
- If a user forgets their password and no recovery key exists, their files are lost.
**How to choose:**
- If you trust your server administrators, use master key mode.
- If you need to prevent admins from accessing files, use E2EE.
- User key mode offers some protection against malicious server administrators, but has limitations.
**To select user key mode:**
Run:
.. code-block:: bash
occ encryption:disable-master-key
before enabling encryption.
Enabling Encryption (Step-by-Step)
----------------------------------
1. Go to the **Server-side encryption** section of your Admin page.
2. Check **Enable server-side encryption**.
3. You’ll see a message: "No encryption module loaded."
Go to your Apps page and enable the Nextcloud Default Encryption Module.
4. Return to your Admin page. The module will appear and be auto-selected.
5. Log out and log back in to initialize your encryption keys.
6. Optional: Un-check the box for encrypting home storage if you wish to keep local files unencrypted.
.. figure:: images/encryption3.png
After clicking the **Enable Encryption** button you see the message "No
encryption module loaded, please load a encryption module in the app menu", so
go to your Apps page to enable the Nextcloud Default Encryption Module.
.. figure:: images/encryption1.png
Return to your Admin page to see the Nextcloud Default Encryption
Module added to the module selector, and automatically selected. Now you must
log out and then log back in to initialize your encryption keys.
.. figure:: images/encryption14.png
When you log back in, there is a checkbox for enabling encryption on your home
storage. This is checked by default. Un-check to avoid encrypting your home
storage.
.. figure:: images/encryption15.png
Encrypting external mountpoints
-------------------------------
Backups
-------
You and your users can encrypt individual external mountpoints. You must have
external storage enabled on your Admin page, and enabled for your users.
Encryption keys are stored in:
Encryption settings can be configured in the mount options for an external
storage mount, see :ref:`external_storage_mount_options_label`
(:doc:`external_storage_configuration_gui`)
- ``data/<user>/files_encryption`` (per-user keys)
- ``data/files_encryption`` (system-wide/external storage keys)
Encrypting External Mountpoints and Team Folders
------------------------------------------------
Encrypting team folders
-----------------------
- You and your users can encrypt external mountpoints.
By default team folder are not encrypted. If you want to encrypt your team folders
as well you need to run following occ command::
- Set encryption options in the mount configuration for each external storage.
- See :ref:`external_storage_mount_options_label` in :doc:`external_storage_configuration_gui`.
occ config:app:set groupfolders enable_encryption --value=true
- To encrypt Team Folders, run:
Like for all other files and server-side-encryption in general, this will not encrypt
already existing files in team folders but only new or updated files after
the occ command was executed.
.. code-block:: bash
.. _occ_encryption_label:
occ config:app:set groupfolders enable_encryption --value=true
occ encryption commands
-----------------------
.. note::
Only new or updated files in team folders will be encrypted.
If you have shell access you may use the ``occ`` command to perform encryption
operations, and you have additional options such as decryption and creating a
single master encryption key. See :ref:`encryption_label` for detailed
instructions on using ``occ``.
Managing Encryption via occ Commands
------------------------------------
Get the current status of encryption and the loaded encryption module::
Here is a reference table for common occ commands:
occ encryption:status
- enabled: false
- defaultModule: OC_DEFAULT_MODULE
.. list-table::
:header-rows: 1
:widths: 35 65
This is equivalent to checking **Enable server-side encryption** on your Admin
page::
* - Command
- Description
* - occ encryption:status
- Show encryption status and module
* - occ encryption:enable
- Enable server-side encryption
* - occ encryption:list-modules
- List available encryption modules
* - occ encryption:set-default-module [Module ID]
- Select default encryption module
* - occ encryption:encrypt-all
- Encrypt all files for all users
* - occ encryption:decrypt-all [user]
- Decrypt all files (or for one user)
* - occ encryption:show-key-storage-root
- Show key storage location
* - occ encryption:change-key-storage-root [dir]
- Move key storage directory
* - occ encryption:enable-master-key
- Enable master key mode
* - occ encryption:disable-master-key
- Enable user key mode
* - occ encryption:fix-encrypted-version
- Fix bad signature errors
* - occ encryption:fix-key-location [user]
- Fix key not found errors
occ encryption:enable
Encryption enabled
**Example: Move keys to a new directory (Ubuntu Linux):**
Default module: OC_DEFAULT_MODULE
.. code-block:: bash
List the available encryption modules::
cd /your/nextcloud/data
mkdir keys
chown -R root:www-data keys
chmod -R 0770 keys
occ encryption:change-key-storage-root keys
occ encryption:list-modules
- OC_DEFAULT_MODULE: Default encryption module [default*]
Select a different default Encryption module (currently the only available
module is OC_DEFAULT_MODULE)::
occ encryption:set-default-module [Module ID].
The [module ID] is taken from the ``encryption:list-modules`` command.
Encrypt all data files for all users. For performance reasons, when you enable
encryption on a Nextcloud server only new and changed files are encrypted. This
command gives you the option to encrypt all files.
Run ``occ``::
occ encryption:encrypt-all
You are about to start to encrypt all files stored in your Nextcloud.
It will depend on the encryption module you use which files get encrypted.
Depending on the number and size of your files this can take some time.
Please make sure that no users access their files during this process!
Do you really want to continue? (y/n)
When you type ``y`` it creates a key pair for each of your users, and then
encrypts their files, displaying progress until all user files are encrypted.
Decrypt all user data files, or optionally a single user::
occ encryption:decrypt-all [username]
View current location of keys::
occ encryption:show-key-storage-root
Current key storage root: default storage location (data/)
Move keys to a different folder, either locally or on a different server.
The folder must already exist, be owned by root and your HTTP group, and be
restricted to root and your HTTP group. Further the folder needs to be located
somewhere in your Nextcloud data folder, either physically, or as a mount.
This example is for Ubuntu Linux. Note that the new folder is relative to your ``occ`` directory::
cd /your/nextcloud/data
mkdir keys
chown -R root:www-data keys
chmod -R 0770 keys
occ encryption:change-key-storage-root keys
Start to move keys:
4 [============================]
Key storage root successfully changed to keys
Create a new master key. Use this when you have a single-sign on
infrastructure. Use this only on fresh installations with no existing data, or
on systems where encryption has not already been enabled. It is not possible to
disable it::
occ encryption:enable-master-key
Fix Bad signature errors::
occ encryption:fix-encrypted-version --all
occ encryption:fix-encrypted-version <userid>
occ encryption:fix-encrypted-version <userid> -p <path>
Fix key not found errors::
occ encryption:fix-key-location <userid>
.. _occ_disable_encryption_label:
Disabling encryption
Encrypting All Files
--------------------
You may disable encryption only with ``occ``. Make sure you have backups of all
encryption keys, including users'.
Disable your encryption module with this command::
By default, only new and changed files are encrypted when you enable SSE.
To encrypt all files for all users run:
occ encryption:decrypt-all
.. code-block:: bash
It will put your server into maintenance mode and back.
It also takes care of disabling encryption when all files have been decrypted.
If the command is aborted some files have been decrypted and others are still encrypted.
In this case the command will keep the encryption turned on
and Nextcloud can handle this situation fine.
You can proceed decrypting the remaining files by calling the command again
once the problems that caused the abortion have been resolved.
occ encryption:encrypt-all
.. warning:: Disabling encryption without decrypting all the files will lead to decryption errors in the future as this state causes unpredictable behaviors.
.. note:: The ``occ encryption:decrypt-all`` can take a lot of time. You can run one user at a time like so: ``occ encryption:decrypt-all <user-id>``.
- **Make sure you have backups before running.**
- The command creates a key pair for each user and encrypts their files.
- Progress is displayed until all files are encrypted.
- **Make sure no users access files during this process.**
Files not encrypted
Decrypting Files / Disabling Encryption
---------------------------------------
- Only possible via occ.
- First, decrypt all files:
.. code-block:: bash
occ encryption:decrypt-all
- **Make sure you have backups before running.**
- Server enters maintenance mode. If interrupted, rerun until complete.
- If some files remain encrypted, rerun the command after resolving issues.
- **Warning:** Disabling encryption without decrypting all files will cause unpredictable errors.
You can decrypt for individual users:
.. code-block:: bash
occ encryption:decrypt-all <user-id>
Data Not Encrypted
-------------------
Only the data in the files in ``data/user/files`` are encrypted, and not the
filenames or folder structures. These files are never encrypted:
Only file contents is encrypted. The following are **not** encrypted:
- Existing files in the trash bin & Versions. Only new and changed files after
encryption is enabled are encrypted.
- Existing files in Versions
- Image thumbnails from the Gallery app
- Previews from the Files app
- The search index from the full text search app
- Third-party app data
.. list-table::
:header-rows: 1
There may be other files that are not encrypted; only files that are exposed to
third-party storage providers are guaranteed to be encrypted.
* - Not Encrypted
* - Filenames and folder structures
* - Existing trash bin files
* - Existing historical file versions
* - Image thumbnails
* - Image previews
* - Full text search index
* - Application data that isn't file-based (e.g., Deck, Tables)
User Keys: Sharing & Recovery
-----------------------------
Using user keys
---------------
**Sharing encrypted files:**
If you disabled master key and are using user keys instead, mind the following information:
Sharing encrypted files
^^^^^^^^^^^^^^^^^^^^^^^
After encryption is enabled your users must also log out and log back in to
generate their personal encryption keys. They will see a yellow warning banner
that says "Encryption App is enabled but your keys are not initialized, please
log-out and log-in again."
Share owners may need to re-share files after encryption is enabled; users
trying to access the share will see a message advising them to ask the share
owner to re-share the file with them. For individual shares, un-share and
re-share the file. For group shares, share with any individuals who can't access
the share. This updates the encryption, and then the share owner can remove the
individual shares.
- After enabling user key mode, users must log out and log in to generate keys.
- Users who see "Encryption App is enabled but your keys are not initialized..." must log out and back in.
- Shared files may need to be re-shared after encryption is enabled.
- For individual shares: un-share and re-share the file.
- For group shares: share with any individuals who cannot access the share, then remove their individual shares.
.. figure:: images/encryption9.png
.. _enable-file-recovery-key:
**Enabling file recovery keys:**
Enabling users file recovery keys
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
If you lose your Nextcloud password, then you lose access to your encrypted
files. If one of your users loses their Nextcloud password their files are
unrecoverable. You cannot reset their password in the normal way; you'll see a
yellow banner warning "Please provide an admin recovery password, otherwise all
user data will be lost".
To avoid all this, create a Recovery Key. Go to the Encryption section of your
Admin page and set a recovery key password.
- If you lose your Nextcloud password, you lose access to your encrypted files.
- If a user loses their password, their files are unrecoverable unless a recovery key is enabled.
- To enable recovery, go to Encryption in Admin page and set a recovery key password.
- Users must enable password recovery in their Personal settings for the Recovery Key to work.
- For users who have enabled password recovery, admins can reset passwords and recover files using the Recovery Key.
.. figure:: images/encryption10.png
Then your users have the option of enabling password recovery on their Personal
pages. If they do not do this, then the Recovery Key won't work for them.
.. figure:: images/encryption7.png
For users who have enabled password recovery, give them a new password and
recover access to their encrypted files by supplying the Recovery Key on the
Users page.
.. figure:: images/encryption8.png
You may change your Recovery Key password.
.. figure:: images/encryption12.png
Please check the various key types in detail `here <encryption_details.html>`_
LDAP and External User Backends
-------------------------------
LDAP and other external user back-ends
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
If you use an external user back-end, such as an LDAP or Samba server, and you
change a user's password on the back-end, the user will be prompted to change
their Nextcloud login to match on their next Nextcloud login. The user will need
both their old and new passwords to do this. If you have enabled the Recovery
Key then you can change a user's password in the Nextcloud Users panel to match
their back-end password, and then, of course, notify the user and give them
their new password.
- If using LDAP/Samba and changing passwords on the backend, users will need both their old and new passwords on next login.
- If recovery key is enabled, admins can reset the password via Nextcloud and notify users.
Troubleshooting
---------------
Invalid private key for encryption app
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
- **Invalid private key for encryption app:**
See `GitHub Issue #8546 <https://github.com/nextcloud/server/issues/8546>`_ and
`workaround <https://github.com/nextcloud/server/issues/8546#issuecomment-514139714>`_.
This `issue <https://github.com/nextcloud/server/issues/8546>`_ is being worked
on. In the meantime there is a
`workaround <https://github.com/nextcloud/server/issues/8546#issuecomment-514139714>`_
which unfortunately is only suitable for administrators comfortable with the
command line.
Further Reading
---------------
- `How Nextcloud uses encryption to protect your data <https://nextcloud.com/blog/encryption-in-nextcloud/>`_
- `Technical impact of Authenticated Encryption <https://hackerone.com/reports/108082>`_
- `Nextcloud SSE Implementation Details <encryption_details.html>`_
- `Nextcloud Encryption (SSE & E2EE) Recovery Tools <https://github.com/nextcloud/encryption-recovery-tools>`_
- `Nextcloud E2EE Server API App (required for E2EE usage) <https://github.com/nextcloud/end_to_end_encryption/>`_