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BREACH Compression Attack Steals SSL Secrets
msm1267 writes "A serious attack against ciphertext secrets buried inside HTTPS responses has prompted an advisory from Homeland Security. The BREACH attack is an offshoot of CRIME, which was thought dead and buried after it was disclosed in September. Released at last week's Black Hat USA 2013, BREACH enables an attacker to read encrypted messages over the Web by injecting plaintext into an HTTPS request and measuring compression changes. Researchers Angelo Prado, Neal Harris and Yoel Gluck demonstrated the attack against Outlook Web Access (OWA) at Black Hat. Once the Web application was opened and the Breach attack was launched, within 30 seconds the attackers had extracted the secret. 'We are currently unaware of a practical solution to this problem,' said the CERT advisory, released one day after the Black Hat presentation."
Those guys are giving away all your exploits.
Sig Battery depleted. Reverting to safe mode.
Lets see, gotta have man in the middle AND requires the attacker and victim to be on the same network.
Piece of cake!
A bullet may have your name on it, but artillery is addressed to " Whom It May concern"
Perhaps Verisign can offer some form of overpriced "insurance" to make customers feel safer on the Internets. I'm sure it'll be thrown in for "free" with a "SecureSite Ultimate" package, for a mere $1500! GoDaddy will no doubt follow suit.
So if sounds like this could be practical on a WiFi network??
This is quite an ingenious attack, but I am very surprised it has taken people so long to find it, as it is very straightforward and easy to understand conceptually. Makes you wonder "how did I not think of that".
Although it may seem like the requirements of a successful attack are difficult to achieve, this may not be the case.
It is usually very easy to inject some plain-text in the source code of webpages.
On facebook:
https://www.facebook.com/photo.php/INJECT_WHATEVER_YOU_WANT_HERE/
If you view the source of that URL you can see the text "INJECT_WHATEVER_YOU_WANT_HERE" appears 3 times in the source code.
By appending the query string, on youtube:
https://www.youtube.com/watch?v=hLkugwOYbFw&INJECT_WHATEVER_YOU_WANT_HERE
And on google:
https://www.google.com/?INJECT_WHATEVER_YOU_WANT_HERE
That means that an attacker can extract secret information from a lot of the HTTPS pages that you're visiting.
When I first read about this attack, the first fix that came into my mind was to just append /* [random text of random size] */ to all text/html responses.
But this may cause troubles: if the random padding is too large, the purpose of compression
is defeated. If it is too small, workarounds may be found.
Maybe it is time to start thinking of algorithms that perform compression and encryption together, not separately?
They just make you visit a malicious website, at which point they can force you to make as many HTTPS requests as they want. They use img src IIRC.
Some information simply does not change from one request to the other. In case of facebook, my name appears on the top blue bar on every page. An attacker can therefore extract my name using this technique.
FTA: "mitigations include disabling HTTP compression"
What's the point of HTTP compression anyway? Text is a small part of the bandwidth, and most other stuff (pictures, etc.) are already kept/stored/transferred in highly compressed formats like JPEG. Trying to compress files like that does little or no good. What am I missing here?
It should be security 101 that you never send your secrets, just send proof that you know the secret.
Nevermind. RTFA for explanation.
See? Text compression in action!
"A government is a body of people usually -- notably -- ungoverned." -Shepherd Book
Amused by notion one would expect a different outcome with HTTP layer vs TLS layer compression. In every way that matters it is exactly same issue only this time attack analysis is limited to response body.
Also have some trouble with assertion "it is very common to use gzip at the HTTP level." For static assets sure however I expect numbers for dynamic content to be a much different story.
There are already SSO products out there that constantly change the value of the session cookie.
How about we don't send the same secret every freaking time? Maybe sign the message with the secret, or just trust that the darn TLS session is doing its job?
If any content (not just secrets) in the response can be altered as a result of the request the compression algorithm can be leveraged to leak information about the response.
My personal view is that SSL provides adequate protection against casual passive observer. It would be very useful if we had means of communicating securely on the Internet, but we do not.
Go ahead and blame the technology for gross misuse and predictable outcome of errecting global trust anchors. SSL is plenty secure when used properly.
The DEFLATE and gzip formats allows multiple blocks of compressed data as well as blocks containing literals with no compression. Plus, just because the default implementation always looks for duplicate strings, doesn't mean you always have to do so. While it would add a heck of a lot of complexity, it should be possible for a web server to ignore duplicates that occur in sensitive strings, and output them in literal blocks so that they don't effect the frequency data of the rest of the stream. All without requiring any changes to browser implementations. This is far from simple, but could probably be done in a generic way for well known http headers.
09F91102 no, 455FE104 nope, F190A1E8 uh-uh, 7A5F8A09 that's not it, C87294CE no. Ah! 452F6E403CDF10714E41DFAA257D313F.
My understanding is that the attacker can't alter the secret, but they control the URL of the request, and try to alter so that as the URL more closely matches the secret, the overall request and response compresses to a smaller size. So there is nothing really of value until the attacker gets the secret, since the attacker is the one creating the request (i.e. the URL).
The CERT advisory is wrong.
“There’s a small, but definite chance that RSA and non-ECC Diffie-Hellman will not be usable for security purposes within two to five years”
The sooner the world switches to ECC the better.
Anyone else getting the feeling we're approaching security the wrong way? There will never be an end to these kind of exploits. Worse yet, they force us to reduce performance in order to gain security.
A properly designed VPN provides secure communications.
Cheap storage VM.