662996 - OCSP requests leak cookies

Status: RESOLVED FIXED

(Core :: Security: PSM, defect)

Description

[Stefan Arentz | :st3fan | ⏰ EST | he/him]

During testing of some OCSP server side code I saw Firefox do the following OCSP request:

POST / HTTP/1.1
Host: evsecure-ocsp.verisign.com
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.7; rv:2.0.1) Gecko/20100101 Firefox/4.0.1
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Accept-Language: en-us,en;q=0.5
Accept-Encoding: gzip, deflate
Accept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.7
Keep-Alive: 115
Connection: keep-alive
Content-Length: 115
Content-Type: application/ocsp-request
Cookie: v1st=YX32X24T8E9X; __utma=136232671.83772523.1; __utmz=1369032.23772523.1.1.utmcsr=(direct)|utmccn=(direct)|utmcmd=(none)

What worries me is that the Cookie header is included.

I think this is a security problem because because it is identifying me to the owner of the OCSP server.

Not only does the owner of the OCSP server now know what site I am visiting (through the SSL certificate hash in the OCSP request body), it can also identify me.

This can be further exploited by OCSP server owners by somehow getting cookies setup for the domain. For example by embedding ads. (I know this is a stretch but it is certainly possible)

Since these OCSP requests are basic API requests, I think they should be as minimal as possible, which means leaving out any headers that are not required. In my opinion that should also include the User-Agent header.

Comment 1

[:Gavin Sharp [email: [e-mail]]]

Attachment: wild guess

I don't know that this is the right fix, but it seems to be the only place where NSS code creates a necko channel (via trySendAndReceiveFcn, which is certainly used by PKIX OCSP code). Also it's untested :)

Comment 2

[Brian Smith (:briansmith, :bsmith, use NEEDINFO?)]

Stefan, do you know what the STR are? I was not able to reproduce this, even after visiting several URLs on verisign.com and then going to paypal.com.

Gavin, thanks for the patch. I will take a look at it once I am able to reproduce the bug.

Comment 3

[Stefan Arentz | :st3fan | ⏰ EST | he/him]

STR:

Go to http://www.verisign.com
Browse around for example change to another language
Validate that a cookie has been set
Quit Firefox (to force OCSP since I don't think it is fully cached?)
Go to https://twitter.com

Go to http://www.godaddy.com
Login 
Validate that a cookie has been set (should be for godaddy.com)
Quit Firefox (to force OCSP since I don't think it is fully cached?)
Go to https://sa.tk (my domain that has a godaddy cert)

It might be easier to enable ocsp.require but you don't have to.

Comment 4

[Kai Engert (:KaiE:)]

I did this:
- enable strict ocsp
- start debug build with NSPR_LOG_MODULES="cookie:5"
- go to verisign (gets a cookie)
- quit firefox
- start firefox
- go to https://twitter.com
- look at trace output, search for ocsp,
  a cookie was sent for an ocsp request

I agree we should not do this.

I applied the patch, and I repeated the above.
I no longer see a cookie being sent to the ocsp server.

Comment 5

[Kai Engert (:KaiE:)]

Comment on attachment 538159 [details] [diff] [review]
wild guess

sr=kaie

Gavin, thanks for this patch. Do you want to take the bug and drive it in, or should we?

Comment 6

[:Gavin Sharp [email: [e-mail]]]

I can take the bug, though I'm not really familiar with the test situation for this code. Are there any automated OCSP tests that a test for this bug could easily be added to?

Comment 7

[Brian Smith (:briansmith, :bsmith, use NEEDINFO?)]

Comment on attachment 538159 [details] [diff] [review]
wild guess

r+.

Unfortunately, we don't have any automated tests for OCSP in Firefox--partly because we don't have any way of generating OCSP responses. Kai's manual test procedure will have to do for now.

Comment 8

[Boris Zbarsky [:bzbarsky]]

Please do NOT add the checkin-needed keyword in the future for patches without metadata.

I took a guess as to what that should be in this case, but next time I'll just remove the keyword...

Comment 9

[Boris Zbarsky [:bzbarsky]]

http://hg.mozilla.org/integration/mozilla-inbound/rev/70634342ce16

Comment 10

[Kai Engert (:KaiE:)]

Ok, thanks a lot Boris!

Comment 11

[:Gavin Sharp [email: [e-mail]]]

Sorry - I intended to land this myself, I just forgot about it.

Comment 12

[(no longer active)]

http://hg.mozilla.org/mozilla-central/rev/70634342ce16

Comment 14

[:Gavin Sharp [email: [e-mail]]]

This was backed out in bug 703024.

Comment 16

[Stefan Arentz | :st3fan | ⏰ EST | he/him]

Can we apply Gavin's patch again now that the dependencies for this bug have been resolved?

I still think this is a major privacy concern: CAs can effectively use this to track someone.

Comment 17

[:Gavin Sharp [email: [e-mail]]]

Yeah, looks like bug 627616 means that the old patch should work as-is (it won't affect proxy authentication).

Comment 18

[Patrick McManus [:mcmanus]]

I relanded this
 https://hg.mozilla.org/integration/mozilla-inbound/rev/da6a55f4fdae

Comment 19

[Stefan Fleiter (:sfleiter)]

This looks suspicious:

     1.1 --- a/security/manager/ssl/src/nsNSSCallbacks.cpp
     1.2 +++ b/security/manager/ssl/src/nsNSSCallbacks.cpp
     1.3 @@ -72,16 +72,18 @@ nsHTTPDownloadEvent::Run()
     1.4    nsCOMPtr<nsIChannel> chan;
     1.5    ios->NewChannel(mRequestSession->mURL, nullptr, nullptr, getter_AddRefs(chan));
     1.6    NS_ENSURE_STATE(chan);
     1.7  
     1.8    // Disabled because it breaks authentication with a proxy, when such proxy
     1.9    // had been setup, and brings blue UI for EV certs.
    1.10    // chan->SetLoadFlags(nsIRequest::LOAD_ANONYMOUS);
    1.11  
    1.12 +  chan->SetLoadFlags(nsIRequest::LOAD_ANONYMOUS);

The comment seems to be outdated by the fix in bug 627616 and thus should be removed, shouldn't it?

Comment 20

[Patrick McManus [:mcmanus]]

comment removed

 https://hg.mozilla.org/integration/mozilla-inbound/rev/c861b47cd0ff

Comment 21

[Ryan VanderMeulen [:RyanVM]]

https://hg.mozilla.org/mozilla-central/rev/da6a55f4fdae
https://hg.mozilla.org/mozilla-central/rev/c861b47cd0ff