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Zoom RCE from Pwn2Own 2021

sector7.computest.nl

11–20 of 126 posts

Re: Zoom RCE from Pwn2Own 2021

#11
post #2

No one should be installing native apps for this now that we have WebRTC.

To be frank, if Zoom was a web only app (or maybe web plus web-in-a-electron like eg Slack and WhatsApp) there'd be a vocal HN crowd complaining that there was no proper native app.

Re: Zoom RCE from Pwn2Own 2021

#13
post #9
post #2

No one should be installing native apps for this now that we have WebRTC.

Unfortunately, Zoom deliberately cripples their web app to the point of being unusable. If your employer uses Zoom, there's no way to avoid the native app.

lol we use Zoom for most of our meetings and I always used the web app, without any issues.

Re: Zoom RCE from Pwn2Own 2021

#14
post #4

Earlier quoted context omitted.

WebRTC has had plenty of implementation issues. https://googleprojectzero.blogspot.com/2020/08/exploiting-an...

There's a difference between Android native bugs and forgoing protection provided by browser on desktop instead of relying on Native apps.

The browser is also a native app. https://googleprojectzero.blogspot.com/2018/12/adventures-in...

Re: Zoom RCE from Pwn2Own 2021

#15
FTA: "Using a combination of proxies, modified DNS records, sslsplit and a new CA certificate installed in Windows, we were able to inspect all traffic, including HTTP and XMPP, in our test environment."

I have setup wireshark for troubleshooting. That's about it. What's the role of proxies, modified DNS records etc. in this setup? How can I duplicate this?

Thanks.

Re: Zoom RCE from Pwn2Own 2021

#16

FTA: "Using a combination of proxies, modified DNS records, sslsplit and a new CA certificate installed in Windows, we were able to inspect all traffic, including HTTP and XMPP, in our test environment." I have setup wireshark for troubleshooting. That's about it. What's the role of proxies, modified DNS records etc. in this setup? How can I duplicate this? Thanks.

The HTTP and XMPP traffic is encrypted using TLS. The proxies were used to decrypt, log and re-encrypt this traffic in real-time.

Re: Zoom RCE from Pwn2Own 2021

#17

FTA: "Using a combination of proxies, modified DNS records, sslsplit and a new CA certificate installed in Windows, we were able to inspect all traffic, including HTTP and XMPP, in our test environment." I have setup wireshark for troubleshooting. That's about it. What's the role of proxies, modified DNS records etc. in this setup? How can I duplicate this? Thanks.

[deleted]

Re: Zoom RCE from Pwn2Own 2021

#18
post #16

FTA: "Using a combination of proxies, modified DNS records, sslsplit and a new CA certificate installed in Windows, we were able to inspect all traffic, including HTTP and XMPP, in our test environment." I have setup wireshark for troubleshooting. That's about it. What's the role of proxies, modified DNS records etc. in this setup? How can I duplicate this? Thanks.

The HTTP and XMPP traffic is encrypted using TLS. The proxies were used to decrypt, log and re-encrypt this traffic in real-time.

And the new certificate and DNS records are to make the proxy look legit to the Zoom client, which would otherwise not accept TLS connections. Especially if there are DNS records which specify which CA is used for the certificate.

Re: Zoom RCE from Pwn2Own 2021

#19
post #12
post #2

No one should be installing native apps for this now that we have WebRTC.

So browser sandboxing? Is that fundamentally different from native sandboxes like snap, flatpak, et al?

Browser sandboxing is more battle tested, and probably a lot more researched, and with more fuzzing performed on it.

I know that at least X11 is not sandboxed with snap/flatpak/etc., and there is no sandbox for macOS/Windows Zoom client, so using web client is infinitely more isolated.

Re: Zoom RCE from Pwn2Own 2021

#20
post #2

No one should be installing native apps for this now that we have WebRTC.

To be frank, if Zoom was a web only app (or maybe web plus web-in-a-electron like eg Slack and WhatsApp) there'd be a vocal HN crowd complaining that there was no proper native app.

Last I checked you didn’t have to install anything. I’m not sure about more advanced usage like screen sharing or how many timing options their are, but for generic “see me, see you” it works fine in the browser.
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