3 Ways Collabora Online Secures your Document Containers

Ensuring the utmost security of your documents and data is paramount. Collabora Online, a powerful document editing solution, goes above and beyond to fortify your security, providing you with a robust shield against potential threats. In this blog post, we’ll delve into some of the central security features that make Collabora Online the trusted choice for so many – including Seccomp BPF, Sparse File Systems, and Chroot. These are the pillars upon which our security stands. We’ll explore how these technologies work together to create a document environment that’s not only highly efficient but also exceptionally secure.

It is worth noting, in order to enact some these security measures, Collabora Online requires enhanced privileges to start with in order to limit access to the rest of a system. These are swiftly dropped after they are used to lock-down each document. This methodology may seem paradoxical at first, but we hope that in this post you will see why these widely-recognized industry-standard1,2 security layers, in fact bring about the greatest safety for your file storage and editing solutions.


Seccomp BPF

Seccomp BPF is a Linux kernel feature that enhances security by restricting the system calls a process can make3. This technology significantly reduces the total kernel attack surface, minimizing the risk of potential security breaches. It lets us shrink the access of Collabora Online document processes to system calls that have been problematic in the past4. All unexpected requests can then be instantly recognized as a malicious attack and cause immediate termination of the the relevant document process by the operating system.

One example threat that this eliminates would be an escaped application attaching a hand-crafted debugger (using the ptrace system call) to try and access data or disrupt other system operations. In this instance however, the use of ptrace or ‘kill’ system calls would be immediately recognized as illegitimate, not performed, the attempt logged, and the document immediately terminated.

As mentioned in the introduction, in order to provide this layer of protection, Collabora Online requires sysadmin capabilities, however these are rapidly dropped after startup, and provide one of the strongest security pillars. By enabling Seccomp BPF within Collabora Online containers, partners can rest assured that their document environment remains safeguarded from a whole set of malicious activities.

The Collabora Online ‘Security Onion’


Chroot, short for “change root,” is a mechanism that runs a process and its children within a confined directory, isolating them from the rest of the system. Integrating Collabora Online with chroot ensures that the application and its dependencies are enclosed within a controlled environment, minimizing the potential for conflicts with other software, and again ensuring any security breaches are isolated by default, greatly reducing the possibility of any system-wide disruption.

What this means in Collabora Online is that every document user is only able to access the document data served to them in the first instance, and cannot acquire access to the rest of the system files, or use the file-system to communicate or disrupt other documents. Similar to the way fire doors are used to prevent the spread of a fire through a building, except in this case the door is fireproof, and there is no key.

Sparse File Systems

Collabora Online has been optimized in many ways to streamline resource utilization whilst bolstering security measures at the same time. One key security optimization is the sparse file system setup.

With a sparse file system setup, Collabora Online minimizes its footprint by exclusively installing the libraries and fonts essential for operation. Unlike other installations that may include unnecessary elements, this streamlined approach both saves on system resource usage, and as with Seccomp BPF above, further reduces the potential system attack surface area.

Examples of exclusions from the Collabora Online chroot would be shell tools, or unnecessary device nodes. By heavily restricting access to system device nodes Collabora Online operates with a very limited set of resources, making it very difficult for any attack to develop within the system. Following on in the fire safety analogy, this would be like removing flammable materials from a building to prevent fires starting or spreading.

In order to remove unnecessary and potentially dangerous functionality from the Collabora Online chroot, enhanced privileges are required. As mentioned above however, this privilege is dropped rapidly after entering the chroot. By only incorporating the resources that are absolutely necessary, Collabora Online further fortifies your system against potential security breaches.

Sharing memory

So why does Collabora need its own containment system? In short – for memory efficiency.

Technologies like Copy on Write (COW) and virtual memory sharing are essential components of Collabora Online’s resource-efficient yet highly-secure environment. When documents are opened in Collabora Online, COW enables multiple users to safely share large parts of the same memory space. This seriously cuts down on time and system resource usage, since other than the content unique to each document, the majority of each Collabora Online instance can be shared.

Given the above warnings about chroot and sparse file systems, this might seem like we are contradicting ourselves, but in this case the reality is that the shared components are only ever framework components, and due to the way COW functions, the new document ‘sharing’ another’s settings has no access to the actual sensitive file data, nor even the ability to modify the shared data from the original file. The key to COW’s speed and efficiency, is that only if/when the framework data is modified (written – as in Copy on Write), is an actual copy created, and new bytes written.

So why bother? Because COW is perhaps analogous to utility supplies, or other public services provided to houses or offices. Not using COW, and re-building the framework data for every document, would be like building new power stations, water treatment works, gas storage facilities, hospitals, schools, train stations, bus stations and road networks for every single house. This is of course not done, and you don’t hear of businesses complaining about the security implications of sharing a water supply with the neighbours.

In the same way, virtual memory allows the majority of memory used to be efficiently shared between containers. The Linux operating system provides strict isolation mechanisms to prevent any write access to another user’s code or document data.

This strikes a well-optimized balance between resource usage and robust security, bringing down the un-shared data cost for each document from perhaps 300Mb to 25Mb. In this way, collaborative working in Collabora Online can remain efficient, all the while safeguarding the privacy and integrity of each user’s data.

Additional security practices

Document editors are substantial applications, and Collabora invests heavily in hardening the LibreOfficeKit core, which forms the foundation of Collabora Online, and comprises over 8 million lines of code. In addition to the security pillars outlined already, further rigorous measures are in place to uncover any issues. These include crash testing, use of COVERITY5, and aggressive fuzzing in partnership with Google’s OSS-FUZZ6.

Crash testing involves subjecting the software to various stress tests and scenarios to uncover vulnerabilities that could lead to crashes or security breaches. COVERITY, a sophisticated code analysis tool, is deployed to scrutinize the code base for potential flaws or vulnerabilities. Complementing these measures is aggressive fuzz testing, where the software is bombarded with a wide range of unexpected inputs to discover and rectify any weak points.

The size of the core code remains the top attack vector, and we work hard to ensure that no code can break out and execute inside the context of the document. This however is why the above protective layers are key to ensuring the highest levels of security for your document editing solution.

Is it just us?

System administrators are rightly cautious when alerted to requests for enhanced permissions, but the reality is that this remains one of the best ways to lock down an application. Google Chrome in Linux for example is also a set-uid program. Other server-side software like Jitsi or Postfix also doesn’t drop all capabilities for similar reasons. Other app containment and sandboxing systems such as Flatpak employ the same strategy of running with elevated privileges to employ specific security measures like Seccomp BPF and utilize sparse file systems. This approach, which ultimately limits the program’s reach and ensures that potential vulnerabilities don’t lead to widespread damage, is a widely recognized and accepted industry practice.


Collabora Online is architected from the ground up to safeguard your documents and data while providing a feature-rich and efficient document editing environment. Operating with enhanced permissions, Collabora Online will ensure you have the best security measures available at your disposal, making sure your digital workspace remains safely locked down.

If you give Collabora Online the permissions it needs to do the job well – you will be much safer.

Keep your data secure with Collabora Online.

Try the Online Demo

Collabora Online – Safe, Powerful, Flexible.


A large number of system calls are exposed to every userland process with many of them going unused for the entire lifetime of the process. As system calls change and mature, bugs are found and eradicated. A certain subset of userland applications benefit by having a reduced set of available system calls. The resulting set reduces the total kernel surface exposed to the application. System call filtering is meant for use with those applications.

CODE & Collabora Online 23.05.4 Released with New Font and QR Code Features

They say time waits for no man, and that’s certainly the case at Collabora. Our latest update to Collabora Online Development Edition has now been released, with a number of exciting new features and improvements, including font previews, QR and barcode generators, as well as a number of bug fixes and performance improvements.

Font Previews

Gone are the days of guessing what a font might look like, with our new font preview drop down, you can immediately view a sample of the font before applying it to the document.

Preview fonts before selecting them

Barcode/QR Code Generator

New to Collabora Online, create and edit barcodes and QR codes with the easy to use QR and Barcode generator dialog. Produce modern documents, with all the functionality you and your users expect and need.

Insert QR codes within documents

Additional Fixes

As well as the exciting new functions listed above, a number of bug fixes have also been carried out, including:

  • Fixed: Navigator Sidebar: Headings Do Not Update Nesting Instantly
  • Fixed: Calc: With multiple views, an edited comment is committed when the other user switches sheets
  • Fixed: Calc: Elements in Chart Type dialogue when editing chart positioned incorrectly
  • Fixed: Calc: Wrong column width after save .xlsx file
  • Fixed: Dark Mode – Document and text is dark
  • Fixed: Calc: No info is shown that spreadsheet is read-only
  • Fixed: Android app or browser: cannot open PDF
  • Fixed: Notebookbar: Online help mixed with keyboard shortcuts (economed)

4 Reasons To Take OWASP Regulations Seriously

Developers must never rely on client-side access control checks.1

With this simple statement, OWASP are putting a very big question mark over the head of any document editor that performs access controls in browser. So what is the big deal, and are client-side access controls really that bad? In this quick post, we’ll find out.

Distributing Data

What happens when a government employee views your tax records, the bank assesses your mortgage application, or your lawyers share documents regarding your case with each other? Depending on the application they are using, it turns out the first operation may well be for the server to make copies of the document for every editor or viewer, before sending the copies to each user’s device. In case it isn’t immediately obvious, this distributive flavour of document editing is extremely concerning for a number of reasons.

1. Lack of Server-Side Enforcement

As mentioned above, one of the core principles of OWASP regulations is enforcing security measures at the server-side. However, when full documents files are sent to the browser for editing, the server loses control over the data. This immediately undermines any ability to enforce security policy.

2. Vulnerabilities

If data files are sent with code to execute policy in the browser, then a malicious script, acting as a “browser” can simply download the document data and discard the policy logic. This exposes the data to potential cyber-attacks and data breaches. OWASP regulation 4.1.1 states this very simply as, “Verify that the application enforces access control rules on a trusted service layer, especially if client-side access control is present and could be bypassed”2, since “client-side logic is often easy to bypass”3. Whilst organisations rightly have training about whether secure USB sticks should or shouldn’t be used with company laptops, nobody is talking about the 3rd party access freely given by company servers to anything pretending to be a browser.

3. Duplicates

When dealing with sensitive (or arguably any) data, the last thing we should think about doing is photocopying it. TOP SECRET – EYES ONLY is a phrase we are familiar with from the world of spies and espionage, yet so often overlooked in the online world. We naively assume that this couldn’t be an issue with our document editor, yet with many services this is precisely what happens when we start a viewing session. Regulation 4.1.5 states developers should “Verify that access controls fail securely including when an exception occurs.” It’s impossible to imagine how any developer can possibly verify such a fail-safe system however when the one of the primary functions of a data centre is duplicating files before distribution to any user.

4. Data Sovereignty and Compliance

Many industries are bound by strict compliance requirements and regulations. Whilst the question of where large data centres are based is beginning to be understood and grappled with, many are overlooking the question of data stored in the cache of users’ browser. Call it what you want, but if this is the way your document editor functions, you are operating a series of international data centres. With just a few clicks and the magic password ‘F12’, the browser will show the cached documents straight away.


Governments or organisations that handle financial records, medical information, intellectual property, or indeed any other data, need to carefully assess whether their document editor is operating in a manner consistent with their own regulations and OWASP guidelines. The implications of sending full copies of documents to every browser are many, and extremely questionable. Genuine server-side policy enforcement is the only way to maintain real security. Collabora Online sends a pixel based view of a document to the end user, whilst the full document data remains safely under your control.


Keep your data secure with Collabora Online.

Try the Online Demo

Collabora Online – Safe, Powerful, Flexible.



1 https://cheatsheetseries.owasp.org/cheatsheets/Authorization_Cheat_Sheet.html

2 https://raw.githubusercontent.com/OWASP/ASVS/v4.0.3/4.0/OWASP%20Application%20Security%20Verification%20Standard%204.0.3-en.pdf

V4.1 General Access Control Design
4.1.1 Verify that the application enforces access control rules on a trusted service layer, especially if client-side access control is present and could be bypassed.
4.1.2 Verify that all user and data attributes and policy information used by access controls cannot be manipulated by end users unless specifically authorized.
4.1.3 Verify that the principle of least privilege exists – users should only be able to access functions, data files, URLs, controllers, services, and other resources, for which they possess specific authorization. This implies protection against spoofing and elevation of privilege. (C7)
4.1.5 Verify that access controls fail securely including when an exception occurs.

3 https://cheatsheetseries.owasp.org/cheatsheets/Authorization_Cheat_Sheet.html

Why Better Accessibility Is Better For Everyone

Accessibility isn’t just a matter of compliance, it’s a commitment to fairness. When content is accessible, it becomes a bridge that connects people, regardless of their circumstances. For instance, individuals with visual impairments can have text read aloud to them through screen readers, while keyboard shortcuts enable those with mobility limitations to navigate without a mouse. Furthermore, it is our firm belief that improvements in document accessibility can be win for everyone, impaired or not.

As such, at Collabora Online we are committed to bringing the best digital experience we can to all our users, and with our latest release are one step closer to making inclusivity a reality for every individual, regardless of their abilities or challenges.

Screen Readers

One of the key features of document accessibility is that documents are readable by screen readers. Screen readers are software programs that read text aloud for people who are visually impaired. To make a document accessible to screen readers, it must be structured in a way that is readable by the software. This includes using headings, lists, and tables to organize the content in a logical and easy-to-understand way.

In order to further improve document readability, we have added an accessibility checker which will highlight areas that require improvement, both adding to a document’s structure and logical flow, as well as flagging specific issues for screen readers.

Additionally, we’ve introduced a new feature that allows screen readers to access menus and dialogs. This change will make it easier for those with visual impairments to navigate and interact with their documents through text-to-speech or braille displays. With our new initial screen reader support, we’re working to ensure that no one is left behind in a digital world.

Keyboard Shortcuts

Another important feature of document accessibility is that documents can be used with only a keyboard. Some users may not be able to use a mouse, so providing keyboard shortcuts and making sure that all controls and links can be accessed with keyboard commands is essential to ensure access for all.

The latest 23.05 release also brings an improvement to our previously existing keyboard shortcut interface, enhancing the user experience for all Collabora Online users.

Dark Mode

The introduction of Collabora Online’s Dark Mode UI isn’t just a stylistic choice, it’s another step towards enhancing visual accessibility and user comfort. Dark Mode has been carefully designed to alleviate eye strain and mitigate other visual accessibility issues that users may face. By reducing the overall brightness and minimising glare, Dark Mode creates a more soothing and comfortable environment for extended periods of document creation and collaboration. We plan to work on low contrast themes next.

Benefits for Everyone

Improving online accessibility is beneficial for everyone by providing a better, more logical and usable user experience. Documents with a clear structure that are easier for screen readers to understand, will also be more easily read by those who do not require screen readers. In the same way, clearer user interfaces, with intuitive shortcuts, will help everyone who is writing, editing, or reading a document. With this attitude in mind, we are very pleased with the latest improvements to Collabora Online, and are confident that as we seek to make Collabora Online more accessible to those with the biggest challenges, we are at the same time improving the experience of all.

Stay tuned over our next releases to see the continuous improvements in accessibility for all.

How Collabora Online Makes GDPR Compliance Easy

Is your online office suite state of the art?

What is the General Data Protection Regulation, or GDPR for short?

The General Data Protection Regulation (GDPR) is the toughest privacy and security law in the world. Though it was drafted and passed by the European Union (EU), it imposes obligations onto organizations anywhere, so long as they target or collect data related to people in the EU. The regulation was put into effect on May 25, 2018. The GDPR will levy harsh fines against those who violate its privacy and security standards, with penalties reaching into the tens of millions of euros.

Well that sounds scary, but what does GDPR really mean for businesses and how they collect and store data? In this quick guide, we will explain what you need to know about GDPR with a focus on how it relates to services such as Office365, Google Docs and Collabora Online.

Under GDPR, if a data ‘controller’ (an organisation that collects any personal data) wants to share personal data with a third-party ‘processor’ (an organization that processes this data, for example Microsoft or Google), they must ensure that the third-party processor provides sufficient guarantees that they will implement appropriate technical and organizational measures to protect the personal data. Even without sharing with third parties, the controller must also show that when “taking into account state of the art” technology, they are incorporating data protection “by design and by default”.

And if all this seems very abstract, it might be worth considering according to German legal firm CMS, there have been over 1,600 fines issued in the last five years, with the average fine a little over €2,400,000. These range from headline grabbing figures for Meta and Amazon, to hundreds and thousands of euros for small and medium businesses, hospitals, government administrations and other companies dotted around the world with European users. After removing the 45 individual fines over 1 million euros for this period, we calculate the average fine comes out at more than €300,000. Got your attention yet?

So what is “state of the art”, and “data protection by design and by default”. At Collabora, we believe the highest level of protection means having the strongest access control requirements, and for this, no-one else does or can do better.

Where is your data?

As technology and the internet has developed, file sharing and collaborative working have become vital for anyone trying to run an efficient business, or even just set a monthly budget or write a letter. We send files in email attachments, in messaging apps, through different file sharing websites, or on a USB stick. We know that there are bad actors ‘out there’, but as long as nothing happens to us, we try not to think about it too much.


The internet is a scary place if you’re on your own

But clearly this is not “state of the art”. The internet is a scary place, and if your data is out in the open like this, anyone could access it.

End to end encryption

Most businesses and applications however recognise the issue here, and the current received wisdom is that ‘end-to-end encryption’ will save the day. To offer you a quick refresher – the general idea with end-to-end encryption is that in order to prevent someone reading a letter who shouldn’t have access, the sender puts a padlock on their letter before putting it in the post, which is then unlocked upon arrival by the recipient. Postman Pat and the rest of the delivery company have no idea what was in the letter, everybody is happy. Sounds good right?

Yet there is an obvious issue staring us in the face with this methodology – it is only end-to-end. A well-intentioned attempt to keep corrupt postmen or system administrators away from your letters or stored data perhaps, but in terms of keeping your data safe in the wider scheme of things, utterly useless! As anyone who’s ever misplaced a letter, had someone read over their shoulder, or indeed had their house broken into can attest to. Where either end might be, who or what is going on there is literally anyone’s guess. End to end encryption also means – you can kiss goodbye to any guarantees of having a malware free server, you certainly can’t scan for viruses anymore or respond fully to a lawful freedom of information request. Nevermind the security implications of what happens when you or one of your staff leaves an ‘end’ with confidential data on it in a bar or taxi or train by mistake. The British government alone reported a total of “96 laptops, tablets, smartphones and other devices lost by or stolen from parliamentary staffers between January 2019 and December 2020, with one device disappearing within Downing Street itself”.

End-to-end encryption, then what?

As far as mitigating this issue goes, companies are left up the creek and without a paddle by this approach. Company laptops are issued that must themselves be encrypted to hopefully secure that end if it is ever lost, and personal laptops are banned, or further lengthy BYOD policies enacted with spurious levels of enforcement.

In the same way that welding your front door shut but leaving the window open is hardly safe, it’d be difficult to honestly argue that this is “data protection by design and by default”. In fact this lack of clarity over what happens at the server ‘end’ is precisely why the German and French governments are taking action to ban some public services from using Office 365 or Google Workspace.

Look, but don’t touch!

So must we accept our valuable data can never be truly safe? We don’t think so! The British Crown Jewels are estimated to be worth upwards of £3 billion. They have lived in the Tower of London since 1661, guarded by the British Army, rarely leaving the premises, yet they have been open to public viewing for most of this time. Within the castle grounds they are viewed by 2-3 million visitors every year, and the only attempted theft ended in failure in 1671. Perhaps our modern collaborative working arrangements could learn something from this open, but secure setup. Is there a way to enable users to view documents, without them leaving the safety of the castle? To look, but not touch?

Well, it turns out there is! While it may well be impractical to start your own international parcel delivery company, it turns out there’s very little stopping a company, individual or organisation from hosting their data within their own premises (be it office or castle!), or with a trusted Collabora partner, essentially running the data-delivery company yourself, and crucially with Collabora Online, sending only images of the viewed parts of the document (not the complete file) to the end users, giving as much or as little editing access as they see fit. Operating more like a hyper-efficient remote desktop than a browser-based editor, user activity is processed by the server in real time, meaning the actual file data never leaves the safety of the server, so no amount of malicious malware, technical tomfoolery or pernicious postmen can extract it from a browser or device. Lost your company laptop? Who cares?! There is no company data on it anyway, and before any bad actors even start looking up your mother’s maiden name, your childhood best friend and what street you grew up on, with a click of a mouse, you can make sure your castle server never communicates with it ever again. Remote wipe if you feel like it, but there’s really nothing on the device!

Collaborative data protection by design and by default

You should use the state of the art solution

If that’s not data protection by design and by default, using state of the art technology, then we don’t know what is. It also remains very unclear how any other software provider intends to honestly address the pressing issue of data security or GDPR compliance, as evidenced by weekly reports of leaks and fines. Don’t sweep the problem under someone else’s rug, be state of the art with Collabora Online and take control of your data.