10 ms·

As much as I'm not a fan of JavaScript, the problem is not so much the language but rather the choice of Electron and all that comes with it. Heck, even a web v

by pfg 8y ago

As much as I'm not a fan of JavaScript, the problem is not so much the language but rather the choice of Electron and all that comes with it. Heck, even a web version or Chrome app would've successfully mitigated these attacks. Electron means you're one XSS away from remote code execution, and even worse, it makes it way harder to mitigate XSS through CSP (which Signal did utilize, but script-src 'self' can easily be bypassed in Electron). FWIW, Signal's native mobile apps are written in Java and Objective-C respectively, so there's not really much of a difference compared to Wire (which is a good choice as well). Still, even a hypothetical React Native app written in JavaScript wouldn't be much worse; after all, React Native isn't just a Web View made to look like a native app, but uses actual native components.

mintplant 8y ago
Signal Desktop actually used to be a Chrome app. Then Google announced the deprecation of that feature and they ported it over to Electron.
- ehPReth 8y ago
  Sad day for Chrome OS users. No more Signal updates! :(
ams6110 8y ago
> Electron means you're one XSS away from remote code execution So, electron is the new flash. I'll be avoiding that, then.
- deleted 8y ago
  [deleted]
rndgermandude 8y ago
While I agree that Electon offers a massive amount of footguns, neither Javascript nor Electon was the issue in this case. The issue was using innerHTML (or rather $.html()) with strings concatenated together from user input. Something you should never do. Could as well just call eval() directly on it, or pass the input to gcc, compile it and run the resulting binary. The Signal devs thought $.html() does some kind of escaping: https://github.com/signalapp/Signal-Desktop/commit/9d41b8616296f1b328aa864e0114b99d7f11ca06 https://github.com/signalapp/Signal-Desktop/commit/9d41b8616... (this commit made something that was easy to exploit into something that was even easier to exploit). To be honest, I'd lay more blame on the authors of the DOM spec making innerHTML a setter than on Electron, and jQuery exposing this misfeature even more with $.html(), teaching an army of web developers to do the wrong thing. We've all seen numerous (XSS) vulnerabilities in all kinds of websites, browser extensions, Electron apps, etc resulting from this API, tho in Electron apps it gets particularly devastating as often you'd get code execution not just in a sandboxed website but full code execution under the current user credentials in the system.
- pfg 8y ago
  So to be clear, a lot of the blame definitely belongs in the "all that comes with it" bucket here, which is one of the reasons why you should think twice about developing desktop apps using a platform that forces you to deal with not only the usual desktop app security concerns, but also all the things that make web apps vulnerable. Still, when you ship an app with a relatively strict Content Security Policy as Signal did (including using script-src 'self'), you don't really expect a simple XSS vulnerability to lead to RCE, but it turns out that policy doesn't really do much in an Electron app.
- caf 8y ago
  Surely the collective noun for footguns is a cache :)
- seba_dos1 8y ago
  >The Signal devs thought $.html() does some kind of escaping: Uhm... that's a really rookie mistake to make. Like, one of the very basics of jQuery usage. I'm not exactly sure what to think about it after seeing this commit you linked...
  - twr 8y ago
    I don't know if this is correct, but, I once got the impression that Signal Desktop was under the sole purview of a new hire at OWS. In other words, Moxie doesn't review the commits. I hope I'm wrong, but even if I'm not, I suppose it makes no difference, as he's arguably responsible either way.
    - debacle 8y ago
      Isn't this supposed to be an app for secure communication? Theo would have a conniption.
      - fjsolwmv 8y ago
        Has Theo de Raadt ever endorsed the security of anything except the default install of OpenBSD?
AgentME 8y ago
>Electron means you're one XSS away from remote code execution, and even worse, it makes it way harder to mitigate XSS through CSP (which Signal did utilize, but script-src 'self' can easily be bypassed in Electron). Can you explain that last part? I can't think of how an XSS attack could get around that, and Electron's documentation specifically recommends it: https://github.com/electron/electron/blob/master/docs/tutorial/security.md#6-define-a-content-security-policy https://github.com/electron/electron/blob/master/docs/tutori...
- pfg 8y ago
  There's a bit of an explanation of this in the article describing the other XSS that's recently been found in Signal[1]. Basically, since the Electron app itself runs under the file:// origin, 'self' can be bypassed with varying degrees of difficulty depending on the platform. On Windows, it's trivial because you can use UNC paths to a SMB share containing a malicious JavaScript file (i.e. file://1.2.3.4/payload.js). On other platforms, you'd need to find a way to place the file on a path accessible via file:// first, for example by sending the file via Signal itself and hoping the user accepts the download. There are ways to lock down the CSP further to mitigate this, but no one really expects script-src 'self' to be unsafe, especially when it's what their documentation recommends. [1]: https://ivan.barreraoro.com.ar/signal-desktop-html-tag-injection/advisory/ https://ivan.barreraoro.com.ar/signal-desktop-html-tag-injec...
burtonator 8y ago
One thing I'd like to see is more use of containers and permissions locally. For example, my IntelliJ runs as my user account, but it doesn't need access to all my files. I should be able to select which directories it has access to and it's within a container by default. I mean I can set this stuff up manually, but in the future I'd like to see this as the default. Similar to the way Android apps ask for permissions.
- kilburn 8y ago
  It seems you are calling for Qubes OS [1], which does that but using VMs (which should be more secure than containers). It will take a looong time for "standard" OSes to get there, if they ever do. The required changes in UX are very significant... [1] https://www.qubes-os.org/ https://www.qubes-os.org/
- pjmlp 8y ago
  That is the whole idea of the UWP model on Windows, and the ongoing work to put Win32 apps inside of the same containers. Or the sandbox models on Android, iOS and macOS.
  - danieldk 8y ago
    And Flatpak on Linux. IIRC the Signal Flatpak is sandboxed.
Rjevski 8y ago
I disagree; the issue is Electron. Sure, you can write secure apps in Electron, just like you can do risky stuff in real-life and be fine most of the time. But why take the risk? Had the app been written with a native language and SDK, they wouldn’t need to worry about escaping or anything. I have yet to hear about getting remote code execution for dumping text into an UILabel or similar, while XSS happens almost every day.

by pfg 8y ago

mintplant 8y ago

Signal Desktop actually used to be a Chrome app. Then Google announced the deprecation of that feature and they ported it over to Electron.

ehPReth 8y ago
Sad day for Chrome OS users. No more Signal updates! :(

ams6110 8y ago

> Electron means you're one XSS away from remote code execution So, electron is the new flash. I'll be avoiding that, then.

deleted 8y ago
[deleted]

rndgermandude 8y ago

While I agree that Electon offers a massive amount of footguns, neither Javascript nor Electon was the issue in this case. The issue was using innerHTML (or rather $.html()) with strings concatenated together from user input. Something you should never do. Could as well just call eval() directly on it, or pass the input to gcc, compile it and run the resulting binary. The Signal devs thought $.html() does some kind of escaping: https://github.com/signalapp/Signal-Desktop/commit/9d41b8616296f1b328aa864e0114b99d7f11ca06 https://github.com/signalapp/Signal-Desktop/commit/9d41b8616... (this commit made something that was easy to exploit into something that was even easier to exploit). To be honest, I'd lay more blame on the authors of the DOM spec making innerHTML a setter than on Electron, and jQuery exposing this misfeature even more with $.html(), teaching an army of web developers to do the wrong thing. We've all seen numerous (XSS) vulnerabilities in all kinds of websites, browser extensions, Electron apps, etc resulting from this API, tho in Electron apps it gets particularly devastating as often you'd get code execution not just in a sandboxed website but full code execution under the current user credentials in the system.

pfg 8y ago
So to be clear, a lot of the blame definitely belongs in the "all that comes with it" bucket here, which is one of the reasons why you should think twice about developing desktop apps using a platform that forces you to deal with not only the usual desktop app security concerns, but also all the things that make web apps vulnerable. Still, when you ship an app with a relatively strict Content Security Policy as Signal did (including using script-src 'self'), you don't really expect a simple XSS vulnerability to lead to RCE, but it turns out that policy doesn't really do much in an Electron app.
caf 8y ago
Surely the collective noun for footguns is a cache :)
seba_dos1 8y ago
>The Signal devs thought $.html() does some kind of escaping: Uhm... that's a really rookie mistake to make. Like, one of the very basics of jQuery usage. I'm not exactly sure what to think about it after seeing this commit you linked...
- twr 8y ago
  I don't know if this is correct, but, I once got the impression that Signal Desktop was under the sole purview of a new hire at OWS. In other words, Moxie doesn't review the commits. I hope I'm wrong, but even if I'm not, I suppose it makes no difference, as he's arguably responsible either way.
  - debacle 8y ago
    Isn't this supposed to be an app for secure communication? Theo would have a conniption.
    - fjsolwmv 8y ago
      Has Theo de Raadt ever endorsed the security of anything except the default install of OpenBSD?

AgentME 8y ago

>Electron means you're one XSS away from remote code execution, and even worse, it makes it way harder to mitigate XSS through CSP (which Signal did utilize, but script-src 'self' can easily be bypassed in Electron). Can you explain that last part? I can't think of how an XSS attack could get around that, and Electron's documentation specifically recommends it: https://github.com/electron/electron/blob/master/docs/tutorial/security.md#6-define-a-content-security-policy https://github.com/electron/electron/blob/master/docs/tutori...

pfg 8y ago
There's a bit of an explanation of this in the article describing the other XSS that's recently been found in Signal[1]. Basically, since the Electron app itself runs under the file:// origin, 'self' can be bypassed with varying degrees of difficulty depending on the platform. On Windows, it's trivial because you can use UNC paths to a SMB share containing a malicious JavaScript file (i.e. file://1.2.3.4/payload.js). On other platforms, you'd need to find a way to place the file on a path accessible via file:// first, for example by sending the file via Signal itself and hoping the user accepts the download. There are ways to lock down the CSP further to mitigate this, but no one really expects script-src 'self' to be unsafe, especially when it's what their documentation recommends. [1]: https://ivan.barreraoro.com.ar/signal-desktop-html-tag-injection/advisory/ https://ivan.barreraoro.com.ar/signal-desktop-html-tag-injec...

burtonator 8y ago

One thing I'd like to see is more use of containers and permissions locally. For example, my IntelliJ runs as my user account, but it doesn't need access to all my files. I should be able to select which directories it has access to and it's within a container by default. I mean I can set this stuff up manually, but in the future I'd like to see this as the default. Similar to the way Android apps ask for permissions.

kilburn 8y ago
It seems you are calling for Qubes OS [1], which does that but using VMs (which should be more secure than containers). It will take a looong time for "standard" OSes to get there, if they ever do. The required changes in UX are very significant... [1] https://www.qubes-os.org/ https://www.qubes-os.org/
pjmlp 8y ago
That is the whole idea of the UWP model on Windows, and the ongoing work to put Win32 apps inside of the same containers. Or the sandbox models on Android, iOS and macOS.
- danieldk 8y ago
  And Flatpak on Linux. IIRC the Signal Flatpak is sandboxed.

Rjevski 8y ago

I disagree; the issue is Electron. Sure, you can write secure apps in Electron, just like you can do risky stuff in real-life and be fine most of the time. But why take the risk? Had the app been written with a native language and SDK, they wouldn’t need to worry about escaping or anything. I have yet to hear about getting remote code execution for dumping text into an UILabel or similar, while XSS happens almost every day.