Rust at Scale: An Added Layer of Security for WhatsApp (opens in new tab)

Did they say anywhere what they did? Rebuilding the stdlib as part of your build can shrink it a lot depending on how much of it you use, but that is still nightly only. Maybe they went no_std or created their own?

Just a few more Rust libraries we've shipped in Chromium:

- https://github.com/image-rs/image-png

- https://github.com/webmproject/CrabbyAvif

- https://github.com/RCasatta/qr_code

- https://github.com/unicode-org/icu4x

Just for reference, Wamedia ships on the major Meta apps and on iOS, Android, Desktop, and Web platforms.

What one should do about this? I mean, beside working on lowering that number.

(Asking as a European who quite stubbornly refuses to install it - there are dozens of us. Dozens!)

Edit: please don't participate in making WhatsApp even more inescapable as it is today.

Where I come from (Malawi, Africa), WhatsApp is so widespread that most people prefer it over email - to the extent that people don't really check their e-mails unless it's required for work or they are applying for something. For most people, WhatsApp is the de-facto communication channel.

I help moderate a community of developers and we hit the whatsapp group limit of 1024 members and sometimes have to wait for someone to leave (intentionally or accidentally) before we can add new members. We've tried to move people onto "better" platforms like Discord or Slack but we always end up coming back to WhatsApp which is subsidized via MNOs (mobile network operators) social media data/internet bundles and for the fact that most people are just stuck on whatsapp.

Yeah and we know it is over 3 billion because security researchers from the university of Vienna could read that in one go from one source ip address without encountering any rate limiting:

"phone number, public keys, timestamps, and, if set to public, about text and profile picture. From these data points, the researchers were able to extract additional information, which allowed them to infer a user's operating system, account age, as well as the number of linked companion devices."

See: https://www.univie.ac.at/en/news/press-room/press-releases/d...

In markets where Whatsapp is entrenched, it’s already begun to enshittify.

They have ads and spam already (sorry, no-consent messages from businesses). This isn’t even new. [0]

There’s a clear pattern, say “we’ve rolled out strict policies”[1] and then… nothing changes on the ground, and TechCrunch writes another “they’ve fixed it” article a year later.[2]

Also their Communities feature has pretty crap UX.

Yes WhatsApp’s pervasive. But if pervasive was the end of the story, we’d all be using ICQ and AOL. The last thing any country needs is to hand over more of their lives to Facebook [sic].

[0] https://techcrunch.com/2022/10/10/in-india-businesses-are-in...

[1] https://techcrunch.com/2024/11/20/whatsapp-will-finally-let-...

[2] https://techcrunch.com/2025/10/17/whatsapp-will-curb-the-num...

Sure, but like with most things, maybe like 200 million max of them in NA/EU would actually bring in real money.

Honestly? That claim seems a bit(read A LOT) exaggerated. I haven't had whatsapp in a decade and none of my friends(scattered all over Europe) or family uses it. Viber used to be a big deal and to an extent still is in some areas of Europe. Personally I think I've talked almost everyone into migrating to Signal.

Doesn't this description describe Facebook itself? Should we make apps more like that as well? Because they could not be more polar opposite each other.

It sounds like it's a design goal of this "wamedia" to _not_ maintain bug compatibility with media players.

AI reply?

WhatsApp doesn't use libsignal, and Android is already pretty Rusty and deployed more than WhatsApp around the world (not just smartphone. Tons of "embedded" use cases also run on custom Android)

If you watch "Microsoft is Getting Rusty: A Review of Successes and Challenges" it appears the whole effort is more on the Azure side, and besides some timid adoption like GDI regions, there is a lukewarm adoption of Rust on Windows side, still pretty much a C and C++ feud.

https://www.youtube.com/watch?v=1VgptLwP588

I suspect they just use no_std whenever its applicable

https://github.com/facebook/buck2/commit/4a1ccdd36e0de0b69ee...

https://github.com/facebook/buck2/commit/bee72b29bc9b67b59ba...

Turn out if you have strong control over the compiler and linker instrumentations, there are a lot of ways to optimize binary size

We invested a lot into build system optimizations to bring this number down over time, although we did accept on the order of 200 KiB size overhead initially for the stdlib. We initially launched using a Gradle + CMake + Cargo with static linking of the stdlib and some basic linker optimizations. Transitioning WhatsApp Android to Buck2 has helped tremendously to bring the size down, for instance by improving LTO and getting the latest clang toolchain optimizations. Buck2 also hugely improved build times.

Probably yes. It's ~300KB per binary, and it's a one-time cost.

It can be avoided entirely by disabling the standard library, but that's inconvenient, and usually done only when writing for embedded devices.

Usually the problem isn't the size directly, but duplication of Rust dependencies in mixed C++/Rust codebases.

If you end up with a sandwich of build systems (when you have library dependencies like C++ => Rust => C++ => Rust), each Rust/Cargo build bundles its copy of libstd and crates. Then you need to either ensure that the linker can clean that up, or use something like Bazel instead of Cargo to make it see both Rust and C++ deps as part of a single dependency tree.

Who knows what they did, but there are things which can be done: https://github.com/johnthagen/min-sized-rust

The whole article a bit watery which is why I read it as a PR rather than technical presentation

WhatsApp could exfiltrate messages at the ends. But I assume the trick lies in the word "default". Didn't Skype also default to end-to-end encryption, unless there was a server flag that disabled it for that specific user (I might be fuzzy on the details)

Every encryption is end to end if you're not picky about the ends, or metadata.

Do you trust facebook (excuse me, meta) to not snoop on your messages, and to not share them with the "intelligence" agencies ?

The point of articles like this is to help build credibility for rust adoption. Rust is still not very widely adopted industry wide, and a lot of smaller players only use established technologies that bigger firms have shown works well. Rust is not inevitable, and articles like this are necessary for its future industry adoption.

> The interesting aspects, such as how they protect against supply-chain attacks

There are standard techniques to help manage this that apply across languages, there's no reason to reinvent that wheel.

> My hope’s that AI gets really good at Rust so one doesn’t have to directly interact with the unergonomic syntax.

"Unergonomic syntax" is the battle cry of many people resisting learning a new language. AIs have progressed far enough that they can help you in that learning process, though.

To be fair the increased reliability of Rust code over C++ isn't just because of memory errors (out-of-bounds accesses, use-after-free, type confusion, etc). You also get:

* No undefined behaviour (outside `unsafe`, which is quite easy to avoid). In C++ there are many many sources of UB that aren't really memory errors directly, e.g. signed integer overflow or forgetting to `return` from a function.

* A much stronger type system.

Those two things have a really significant impact on reliability.

Oh come on, that was funny. It also highlights a problem with the way people write rust. If your app panics it has a bug. People throw panics in cases that can absolutely happen, a file isn't there or fails to parse, some set of inputs is mutually inconsistent these are things for error checking. Even if the correct way to handle an error you detect is to stop the app, do that instead of panicking. Panics are for things that should be impossible. Ideally they even get optimized out.

We really need an AI filter here on HN.