The Case of the Modified Binaries

http://www.leviathansecurity.com/blog/the-case-of-the-modified-binaries/

by pcwalton • 12 years ago

193 72 12 years ago

tantalor• 12 years ago

this is the only node that I found patching binaries

This suggests the exit relay itself is doing the patching. Isn't it more likely that some MITM between the exit relay and origin server is responsible?

icebraining2• 12 years ago

I don't see why would it be more likely. The exit node explanation is simpler.

phw• 12 years ago

That's entirely possible and wouldn't be the first time that an exit relay's upstream or data center is responsible for MitM attacks.

matt_morgan• 12 years ago

As he states, the way he found that node wasn't comprehensive. We shouldn't take that statement to mean there are no other exit nodes patching binaries. He just stopped after he proved it wasn't only a theoretical exploit.

spindritf• 12 years ago

Companies and developers need to make the conscious decision to host binaries via SSL/TLS

Yes. And source code, too. If you can't provide ssl for downloads, you should be using a third party service like GitHub who can.

eps• 12 years ago

If an adversary is currently patching binaries as you download them, these ‘Fixit’ executables will also be patched. Since the user, not the automatic update process, is initiating these downloads, these files are not automatically verified before execution as with Windows Update.

Except that this FixIt binary will have no signature and Windows will light up like a Xmas tree. So it really comes down to whether you pay attention to these warnings or you don't. And if you don't, despite all of the Microsoft's effort of past 10 years, then you get what you deserved.

darklajid• 12 years ago

If you're already able to MITM the user, what about

- patching (more .. corrupting) binaries, hoping to break Windows Update

- intercepting and replacing the top 5 'Make Windows Update work again' downloads with a (signed if you want) application of your own?

Bonus points for injecting 'Already got this host' into requests from now on, so that Windows update magically starts working again..

Animats3• 12 years ago

Even SSL may not help. Cloudfront is now offering what they call "Flexible SSL". This means Cloudfront gets an SSL cert which allows them to impersonate the site, they offer an SSL connection to the user's browser, Cloudfront acts as an man-in-the-middle and makes a connection to the destination site. An unencrypted connection in many cases.

This is SSL as security theater.

andrewksl• 12 years ago

Why wouldn't SSL help? Unless the offending exit node has the requested site's cert, there's almost no way they can carry out a MITM attack on an SSL request undetected. That's kind of the whole point of certs.

Or is this an indictment of Cloudfront offering to be your SSL termination point?

Animats3• 12 years ago

This is an indictment of Cloudfront offering to be your SSL termination point, and using multiple-domain certs to do it. Here's the Black Hat paper on how to exploit that.

https://bh.ht.vc/vhost_confusion.pdf

icebraining2• 12 years ago

* Cloudflare

It's obviously not nearly as secure as end-to-end SSL, but it's probably still useful. The connection between the client's machine and the Cloudflare's server is more likely to be under attack (unencrypted Wifi, hacked personal routers, rogue exit TOR nodes, etc) than the connection between datacenters.

justcommenting5• 12 years ago

not always. as we've learned from the NSA disclosures, there are many layers of indirection.

scott_karana2• 12 years ago

How is this different than trusting the website's own load balancer, which might terminate the SSL connection and relay unencrypted traffic to the servers?

Tepix• 12 years ago

The unencrypted connection between the load balancer and the backend server would be taking place behind a firewall.

billpg• 12 years ago

It's not enough to check the hash of a downloaded executable if the hash you're checking against came from the same source as the suspect file.

I find it so infuriating when I see a download page with hashes and the download links next to each other, as if that's any help at all.

icelancer• 12 years ago

No, but it's another step in the process for sure. It's not useless.

kaoD2• 12 years ago

It's not useless.

How not?

4ad3• 12 years ago

The hash is not for cryptographic purposes, it's to detect corrupt downloads. Ideally you should provide both the hash and you should pgp sign your releases.

colanderman5• 12 years ago

That is bizarre. Like "I thought XMODEM went out of style in 1992" bizarre. Shouldn't checksumming the payload be performed at the application layer?

(A quick Google shows that indeed it can be: the Content-MD5 header <http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html>. Wonder how widely supported it is by HTTP software used by people who like to check hashes of things they download.)

sysk• 12 years ago

Do corrupt downloads really happen these days and what causes the downloads to become corrupt? I can't remember having a single corrupt HTTP download in the past 10 years.

yourad_io2• 12 years ago

Still better than seeing this as "installation instructions":

    curl http://not-ssl.somesite.ru/ba.sh | bash

Often without an https:// option available at all.

emillon2• 12 years ago

I've made a list here:

http://curlpipesh.tumblr.com/

peterwwillis• 12 years ago

The only people who provide either a checksum or a PGP signature for downloads are geeks. Those geeks usually distribute their files via mirrors, who all download from either the main source or other sources. Any of those downloads could have been corrupted mid-download (for a variety of real world reasons), so the checksum verifies the file integrity. The PGP key is there for the 1% of people who want to verify the file came from the author; it's up to you to figure out how to get the author's PGP key in a secure fashion (typically HTTPS from their website, or via e-mail).

song• 12 years ago

Companies and developers need to make the conscious decision to host binaries via SSL/TLS

Of course the problem with that is that countries with censorship like china seriously throttle or outright block any SSL connection that are made outside of the country. And sometimes they even use something like SSL strip to do a MITM attack with a self signed certificate.

Average users there are also used to seeing self signed certificates locally and so never even think twice before discarding a message alerting them that a SSL certificate is not valid.

notastartup3• 12 years ago

I wonder how do security professionals acquire their knowledge. Even more curiously, how do these malware writers do this?

Programming can be easily learned by reading and practicing but IT security, one doesn't know where to begin, what the journey is like.

yetihehe• 12 years ago

You start here: http://thelegendofrandom.com/blog/archives/223 or here http://www.reteam.org/ID-RIP/database/essays/es29.htm and spend hundreds of hours on reading and using debuggers.

notastartup3• 12 years ago

omg that is so cool!!! so this is how 'serial crackers' work.

newaccountfool• 12 years ago

Creating malware is simple, creating good malware that stays undetected is hard, very hard.

gear54rus• 12 years ago

Same here. It always eluded me. Security seems like a field where there is still no definite way to get good at.

Being a good security researched requires (among many other things) ability to understand how things work. How ANY things work down to the LOWEST level. Idk about others but I always considered 'security guys' to be the elite of elites in IT world.

notastartup3• 12 years ago

yeah i knew it boils down to some really low level knowledge but seems like a lot of black magic to me regardless on how people end up being able to publish papers or discover vulnerabilities...is it just educated trial and error ? poking at things that you think, hmmm maybe there's a hole here somewhere and then viola, you come across a CVE?

boklm• 12 years ago

This exit node is now flagged as BadExit: https://atlas.torproject.org/#details/8361A794DFA231D863E109...

angry_octet5• 12 years ago

Tried to download Mozilla Thunderbird lately? Have any luck finding a SHA checksum for it? Its hidden at: http://download.cdn.mozilla.net/pub/mozilla.org/thunderbird/...

You can't get it over SSL. Not to worry, the binary will be signed by Mozilla right? Yeah, GPG only. Not x.509 signed.

But hey, the online install page supplies it over SSL right? Well, sometimes. But it turns out they don't enforce SSL use. Cue SSLstrip.

PS On MacOS X 10.9 Apple by default prevents running unsigned binaries. Not to worry, Mozilla tells you how to bypass the check, not even hinting it has a very valid purpose. https://support.mozilla.org/en-US/kb/firefox-cant-be-opened-...

lpsz• 12 years ago

Up until recently even OpenSSL's own download page was not HTTPS.

rockdoe3• 12 years ago

Just like Mozilla's page, that makes perfect sense as long as the authenticity can be verified via other means, such as PGP signatures.

What use is having HTTPS to protect the very thing that you need to implement it. It's a basic chicken and egg problem, replayed every time OpenSSL gets compromised, and successfully circumvented by securing it with something else.

Think about it: there's an SSL break and you need to update OpenSSL. What good does it do you to have it available over SSL?

rockdoe3• 12 years ago

Uh, in case you didn't notice, those SHA checksums are also PGP signed.

I Googled Mozilla Thunderbird and the first hit was the download page, using HTTPS. You're right SSL isn't enforced, but that's a chicken and egg problem for Firefox downloads I guess, now that TLS 1.2 is enforced and the user may be stuck with a browser not supporting that.

angry_octet5• 12 years ago

In case you didn't read, yes I said they were GPG signed. But they don't make that info available (or linked) on the main download page, you have to google to find it.

SSL 3 is still fine for protecting integrity, just not confidentiality, so it is okay for downloads.

angry_octet5• 12 years ago

Found an SSL source: https://ftp.mozilla.org/pub/mozilla.org/thunderbird/releases...

https://gpg.mozilla.org/pks/lookup?search=releases%40mozilla...

seanp2k2• 12 years ago

Really hate the Microsoft standard here of "unknown error" everywhere. Is it really that hard to give a name to those, MS? "File signature verification issue" would be a million times more helpful. This has always bothered me deeply with MS software; that it's almost impossible to tell what's happening from logs / error messages.

psykovsky• 12 years ago

How would they get people to pay for support if the errors were explained in a clear language?

peteri• 12 years ago

One quick google (but you do need the 0x) and you get to this documentation:

BG_E_VALIDATION_FAILED (0x80200053) The application requested data from a website, but the response was not valid. For details, use Event Viewer to view the Application Logs\Microsoft\Windows\Bits-client\Operational log

Which seems pretty clear to me (although plausibly not to an end user).

The Case of the Modified Binaries

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