1704843 - (CVE-2021-29974) HSTS includeSubDomains not properly enforced

Status: VERIFIED FIXED

(Core :: Security: PSM, defect)

Description

[Peter Gerber (:pege)]

User Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Firefox/78.0

Steps to reproduce:

1. Go to https://tocco.ch/status-tocco

As part of the response, Firefox is informed about a HSTS policy that includes subdomains:

Strict-Transport-Security: max-age=43200;includeSubDomains

2. Visit http://abc.tocco.ch/status-tocco

As result of the HSTS policy received early, the request is made using https but a "Accept the Risk and Continue" is still shown.

Also, clicking on SSL_ERROR_BAD_CERT_DOMAIN reveals that Firefox doesn't think there is a HSTS policy in effect:

https://abc.tocco.ch/status-tocco

Unable to communicate securely with peer: requested domain name does not match the server’s certificate.

HTTP Strict Transport Security: false
HTTP Public Key Pinning: false

Actual results:

"Accept the Risk and Continue" button is shown.

Expected results:

As intended by the Strict-Transport-Security header, there should be no way to add an exception. I also checked Firefox 78 ESR and there the behavior was still correct.

Comment 1

[Andrew McCreight [:mccr8]]

I'm not entirely sure which component this should go in, but hopefully this is closer to the right one.

Comment 2

[Dana Keeler (she/her) (use needinfo) [:keeler]]

:baku, I don't think network partitioning is behaving correctly with respect to HSTS. Can you have a look?

Comment 3

[Daniel Veditz [:dveditz]]

It looks like we're partially performing HSTS -- I do get from http: -> https, it's just carrying over the "no exceptions allowed" part.

Comment 4

[Peter Gerber (:pege)]

I had a look at how Firefox for Android (87 and nightly) handles this. Turns out there an "Accept the Risk and Continue" button is shown even for domains on the HSTS Preload list. For instance, you can go to http://may.arbitrary.ch, which doesn't have a valid certificate for that name, and you'll get upgraded to https but you'll still see that Continue button.

Comment 6

[Tim Huang[:timhuang]]

I've tested this with Network Partitioning disabled, and the issue is still there.

And subdomains will use the same partitionKey because we are using eTLD+1 as the key. So, theoretically, the HSTS cache is not partitioned between tocco.ch and abc.tocco.ch.

Comment 7

[Peter Gerber (:pege)]

:timhuang, are you sure about this not being caused by network partitioning? When I flip the privacy.partition.network_state preference to false, the issue disappears for me and I'm told again I can't visit the page because of the HSTS policy. After flipping the switch, you have to make sure you visit https://tocco.ch again first to pick up the HSTS information and then head to https://abc.tocco.ch.

Comment 8

[Tim Huang[:timhuang]]

Ah, I see, there will still be an error page but cannot do "Accept the Risk and Continue" there. Sorry that I didn't understand the issue correctly. I will dig into this. Thanks.

Comment 9

[Tim Huang[:timhuang]]

The root cause is that we use the OAs without the partitionKey to check the HSTS state when loading the cert error page. So, the error page will have a wrong state about HSTS. However, it doesn't affect HSTS in the network layer, just only the error page.

Comment 10

[Tim Huang[:timhuang]]

Attachment: Bug 1704843 - Part 1: Use the OAs with the partitionKey to get HSTS state in nsDocShell. r?ckerschb

Comment 11

[Tim Huang[:timhuang]]

Attachment: Bug 1704843 - Part 2: Add a test to verify HSTS parameter includeSubDomains works correctly when network partitioning is enabled. r?ckerschb

Depends on D114614

Comment 12

[Sebastian Hengst [:aryx] (needinfo me if it's about an intermittent or backout)]

Part 1: Use the OAs with the partitionKey to get HSTS state in nsDocShell. r=ckerschb
https://hg.mozilla.org/integration/autoland/rev/776d2e2ecd043cdc269753bc75ae06bd6a938e14
Part 2: Add a test to verify HSTS parameter includeSubDomains works correctly when network partitioning is enabled. r=ckerschb
https://hg.mozilla.org/integration/autoland/rev/45c659bd4922fa3b4a7b602c6214f16092a31284

https://hg.mozilla.org/mozilla-central/rev/776d2e2ecd04
https://hg.mozilla.org/mozilla-central/rev/45c659bd4922

Comment 13

[Rares Doghi, Desktop QA]

This issue is Verified as fixed in our latest Nightly build 90.0a1 (2021-05-24) On Windows, Mac and Ubuntu.

Comment 14

[Tom Ritter [:tjr]]

Attachment: advisory.txt