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Patch Critical Cryptographic Vulnerability in Microsoft Windows [pdf]

media.defense.gov

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Re: Patch Critical Cryptographic Vulnerability in Microsoft Windows [pdf]

#61

Post by munchbunny »

Uptrenda wrote: post #22

None of these links describe how the exploit works. I found this: https://media.defense.gov/2020/Jan/14/2002234275/-1/-1/0/CSA... So based on my limited understanding: 1. The certificates have a place for defining curve parameters. 2. The attacker specifies their own parameters so that they match the start of a standard curve but choose the rest of the parameters themselves. With the right ECC math they are able to g…

I wonder what happens at the Microsoft Security Response Center when a big vuln hits like this? Does it tie up all their resources just working on the one vuln?

Generally no, if only because of Microsoft’s sheer size.

For something like this issue, while its potential impact is big, I would guess that it only tied up the team(s) that work on CryptoAPI.

Re: Patch Critical Cryptographic Vulnerability in Microsoft Windows [pdf]

#62

Post by munchbunny »

cesarb wrote: post #51
richardwhiuk wrote: post #40

Earlier quoted context omitted.

"enable remote code execution." suggests it's worse than that - like the curve parameters might allow a buffer overflow, or something of that nature. Maybe they just mean because it can sign Authenticode signatures

I haven't seen it mentioned anywhere yet, but I have to wonder... Does this vulnerability allow MITM of Windows Update itself? I would expect all connections to the Windows Update servers to be protected with TLS, and as a second layer the updates themselves to be signed, but if this vulnerability allows bypassing both signatures, this could be really bad.

Only if Microsoft is using ECC for its Windows Update certificates. I would guess not given how many past OS versions Windows Update has to support.

Re: Patch Critical Cryptographic Vulnerability in Microsoft Windows [pdf]

#63

Post by macinjosh »

age_bronze wrote: post #12

Nothing screams "we have microsoft keys!" harder than the fact that the only vulnerabilities reported by the NSA is a cryptographic validation bug. If I had to guess exactly what kind of vulnerabilities they do not need, this is exactly those kind. Who needs crypto validation bug when you already own microsoft's keys?!

I think you're spot on. Everything agencies at this level do is calculated and weighed carefully. They definitely would not seek to patch a useful vuln. It is a PR stunt.

Re: Patch Critical Cryptographic Vulnerability in Microsoft Windows [pdf]

#64

Post by mzs »

kornholi wrote: post #3

From Krebs tweets: The NSA's Neuberger said this wasn't the first vulnerability the agency has reported to Microsoft, but it was the first one for which they accepted credit/attribution when MS asked. Sources say this disclosure from NSA is planned to be the first of many as part of a new initiative at NSA dubbed "Turn a New Leaf," aimed at making more of the agency's vulnerability research available to major softwar…

The tweet* from the call with reporters - a cynical person might think instead that NSA thought that with the similarity to the LE and FF flaws it was not much longer before a hostile actor would find this crypt.dll flaw so it was time to notify MS.

* https://twitter.com/briankrebs/status/1217125030452256768

Re: Patch Critical Cryptographic Vulnerability in Microsoft Windows [pdf]

#65

Post by munchbunny »

heartbreak wrote: post #53
ynik wrote: post #52

Earlier quoted context omitted.

The attack allows faking https certs as well as code signing certs; so it seems plausible that a MitM attacker could trick Windows Update (or other auto-updaters) into executing malicious code.

That this exploit can be used to spoof the Windows Update system is a big yikes. You can’t necessarily trust today’s update itself.

That depends on whether Windows Update is using ECC certificates. A quick scan of my Windows 10 trusted root certificate store shows almost exclusively RSA based certificates, so I’d guess 80% odds that Windows Update itself isn’t affected.

Re: Patch Critical Cryptographic Vulnerability in Microsoft Windows [pdf]

#66

Post by est31 »

rst wrote: post #47
richardwhiuk wrote: post #40

Earlier quoted context omitted.

"enable remote code execution." suggests it's worse than that - like the curve parameters might allow a buffer overflow, or something of that nature. Maybe they just mean because it can sign Authenticode signatures

The pseudonymous but well-connected 'swiftonsecurity' twitter account reports on background that 'RCE' chatter about this particular vulnerability does indeed relate to compromised software update channels. (Not just AuthentiCode, but also MITM on, say, connections to the npm package server.) See https://twitter.com/SwiftOnSecurity/status/12171594348808478... That said, this same patch set also has a separate pre-aut…

> connections to the npm package server

Doesn't npm use node.js for this, which uses openssl?

> https://nodejs.org/api/tls.html#tls_tls_ssl

Third party tools connecting to the npm server that use Window's TLS library would absolutely be affected though.

Re: Patch Critical Cryptographic Vulnerability in Microsoft Windows [pdf]

#67

Post by withinrafael »

floatingatoll wrote: post #35
m0xte wrote: post #26

Anyone got any news on Windows 7 seeing as it's still 25% market share approx according to statcounter?

Does Windows 7 crypt32.dll support ECC?

Yes. https://docs.microsoft.com/en-us/windows/win32/secauthn/tls-...

Re: Patch Critical Cryptographic Vulnerability in Microsoft Windows [pdf]

#68

Post by es56yhse6 »

Interesting comment on reddit:

> Within the federal space, we've been making unprecedented plans for patching systems as soon as this patch is released today. In my agency we're going to be aggressively quarantining and blocking unpatched systems beginning tomorrow. This patch has been the subject of many classified briefings within government agencies and military.

https://old.reddit.com/r/sysadmin/comments/eoll74/all_hands_...

Re: Patch Critical Cryptographic Vulnerability in Microsoft Windows [pdf]

#69

Post by william_T »

macinjosh wrote: post #63
age_bronze wrote: post #12

Nothing screams "we have microsoft keys!" harder than the fact that the only vulnerabilities reported by the NSA is a cryptographic validation bug. If I had to guess exactly what kind of vulnerabilities they do not need, this is exactly those kind. Who needs crypto validation bug when you already own microsoft's keys?!

I think you're spot on. Everything agencies at this level do is calculated and weighed carefully. They definitely would not seek to patch a useful vuln. It is a PR stunt.

The NSA's job is to gather information. They have >400mil people to protect, and 6bn people to attack. They are in the business of using exploits, not closing them.

Re: Patch Critical Cryptographic Vulnerability in Microsoft Windows [pdf]

#70

Post by mzs »

tptacek wrote: post #48

From a conversation with Thomas Pornin, a plausible explanation given the details provided in the DoD advisory: Given an ECDSA signature and control over the curve domain parameters, it's straightforward to create a second private key that matches the original public key, without knowledge of the original signing private key. Here's how: To start with, you need to understand a little bit about how curve cryptography…

The important part might be just how hard it is to come-up with G'.
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