8 ms·

Man-In-the-Middle Interfering with Increased Security

97 points by jvehent 11y ago

xcombelle 11y ago
The bug speak about some security scanners and antivirus products. But the thing which triggered was a malware. Oups! I should have said a potentially unwanted program.
jvehent 11y ago
For some background around the discovery and analysis of the issue, see this thread: https://groups.google.com/forum/#!topic/mozilla.dev.platform/ZNKxYgIk_Sg https://groups.google.com/forum/#!topic/mozilla.dev.platform...
JoshTriplett 11y ago
It's worth noting the reason why Mozilla made this change: not because they consider these systems acceptable, but because they can't even get telemetry data on the scope of the problem because the telemetry mechanism naturally also uses HTTPS, and because this issue prevents such users from getting updates to Firefox itself.
- meowface 11y ago
  Would they consider these systems to be necessarily unacceptable? Intercepting TLS at a corporate proxy is perfectly valid and necessary for a decent security program.
  - pfg 11y ago
    Corporate proxies aren't the issue here; Outdated corporate proxies and other "security" software still issuing SHA-1 certs is what's causing this.
    - meowface 11y ago
      Yes, that part is definitely unacceptable.
  - bbayles 11y ago
    I agree that it's perfectly valid, but disagree that it's necessary. Deploying proxies has costs - it obscures the endpoints of communication from sensor software and makes anomaly detection more difficult. Richard Bejtlich's "Practice of Network Security Monitoring" has a chapter dedicated to the costs and benefits of proxy deployments; I recommend the book for a look at one coherent method of network security monitoring.
    - AnthonyMouse 11y ago
      > Deploying proxies has costs - it obscures the endpoints of communication from sensor software and makes anomaly detection more difficult. It also establishes a single machine that sees all the plaintext of everything that should have been TLS encrypted from every machine on your network. It's like attacker catnip.
      - meowface 11y ago
        If an attacker is able to gain root access to your proxy, or inline with a TAP where your proxy is sending intercepted traffic to, you probably have much bigger problems.
        AnthonyMouse 11y ago
        > If an attacker is able to gain root access to your proxy, or inline with a TAP where your proxy is sending intercepted traffic to, you probably have much bigger problems. Bigger problems than an attacker being able to decrypt and modify all of the TLS sessions in your company? If you have bigger problems than that then they've presumably spilled out of the realm of IT problems entirely and you're dealing with some kind of government lawyers or maybe a large uncontrollable fire.
        meowface 11y ago
        Being able to decrypt and modify TLS sessions pales in comparison to being able to access your domain controller, or dump all your databases.
  - stdgy 11y ago
    I don't think they would. The issue isn't that traffic is being intercepted inside the enterprise. It's that the proxy performing the interception is issuing a certificate that uses SHA-1 in it's digital signing algorithm.
  - wyldfire 11y ago
    I am probably in the minority here, but I don't agree. I understand why the security program does it and why they think they need to. I just think that, regardless of who owns this computer and the network it's connected to, if I'm using it, I should be able to use TLS without any interception.
    - kevinastone 11y ago
      I'm shocked to think this is a minority opinion. Please give us certificate pinning because this type of interception is completely hostile to the end user.
      - pfg 11y ago
        Pinning, as implemented by major browsers[1][2], doesn't prevent this. Private trust anchors are exempt from key pinning. This is deemed acceptable because in order for the proxy root to be trusted, it would have to be installed on your system, so whoever owns the proxy already has control over your client. If you think that using MitM proxies should be illegal for employers or other organizations providing clients, that's probably more of a legal discussion. I don't think there's necessarily a right to privacy when it comes to internet use at your workplace, as long as all parties are aware of this. [1]: https://www.chromium.org/Home/chromium-security/security-faq#TOC-How-does-key-pinning-interact-with-local-proxies-and-filters- https://www.chromium.org/Home/chromium-security/security-faq... [2]: https://wiki.mozilla.org/SecurityEngineering/Public_Key_Pinning#How_to_use_pinning https://wiki.mozilla.org/SecurityEngineering/Public_Key_Pinn...
        edwintorok 11y ago
        Could Firefox display an icon or provide a visible warning to users when traffic is being intercepted? The root cert could've been installed by malware, no?
        JoshTriplett 11y ago
        This seems like a good first step: Firefox should display a persistent, unremovable notification bar that makes it clear that the connection appears MITMed. If people complain about that notification, the answer is "remove whatever malware you have, or complain to your network administrator".
- chei0aiV 11y ago
  They just need to merge the Tor Browser into Firefox and add a meek-like http-based pluggable transport, then they can get around these weird MITM boxes. They probably should have foreseen this and used OpenPGP-based updates over plain HTTP though.
  - jvehent 11y ago
    The updates themselves are served over HTTP and signed, but the request that verifies an update is available is done over HTTPS.
- revelation 11y ago
  And their telemetry needs are superior to the actual privacy at stake here? And they are now providing an updated version of Firefox that merely flip-flops on the protection, instead of providing a message "hey, you're being intercepted"? I'm not naive, but I still think it's only to prudent to point out how ridiculous this sounds. In any case, it seems like Mozilla needs a bit of Skype-magic for their update process. Relying on the very thing you are patching with every minor version seems silly regardless.
  - pfg 11y ago
    "Breaking" the browser for a large number of users will only lead to one thing: Users switching to a browser that still supports SHA-1 certs issued after Jan 1st, 2016. No privacy improvement there either. Additionally, there are many valid use-cases for replacing certificates, e.g. corporate proxies. They should just stop using outdated hashing algorithms for those certs. It's not Mozilla's place to decide whether that use-case is valid or not. SHA-1 was never fully disabled; it's just that certificates using SHA-1 issued after that date weren't accepted anymore. Telemetry is important to understand the ramifications of this issue. This change is likely to be reverted once Mozilla understands the implications. Take a look at the discussion on Mozilla's mailing list for more insight into their thinking[1]. [1]: https://groups.google.com/forum/#!topic/mozilla.dev.platform/ZNKxYgIk_Sg https://groups.google.com/forum/#!topic/mozilla.dev.platform...
  - rcthompson 11y ago
    I think the idea is to first revert to a state where people behind this MITM boxes can receive updates to firefox, and then decide how to handle things from there.
Zarel 11y ago
This was a problem for Pokémon Showdown recently. We use HTTPS for logins and some other things, which stopped working a few days ago for users using MitM antiviruses and Firefox. https://twitter.com/TonyFlygon/status/684756701027954689 https://twitter.com/TonyFlygon/status/684756701027954689 (Example user complaint.) There's no way to detect whether or not an HTTPS iframe has failed to load, so my workaround was to fall back to HTTP if the HTTPS iframe didn't load within 2 seconds. We still switch the connection over to HTTPS if the iframe does eventually load. I'm kind of confused by why so many users thought it was a Pokemon Showdown issue, specifically. Doesn't Google default to HTTPS? PS shouldn't be the most significant website they have trouble with.
- leesalminen 11y ago
  Why not use HTTPS everywhere?
  - Zarel 11y ago
    Well, we do support full-HTTPS, it just isn't required. If it were, PS would have been unusable to anyone with Firefox and Avast/BitDefender/etc. It also allows image embeds. Users often share HTTP images in the chatrooms, which browsers using the HTTPS site complain about. For some weird reason, Google Chrome doesn't support data-URIs in HTTPS when using HTML5 drag-and-drop to drag files from a website to the desktop, which requires an annoying workaround. In addition, most people wanting to set up a third-party PS server don't want to go through the hassle of acquiring a certificate. It makes the setup process a lot more complicated than just "clone the repository and run ./pokemon-showdown"
- Buge 11y ago
  That opens you up to any active attacker simply stopping traffic. You're usually safe against passive attacks if the network has no glitches, but completely vulnerable to active attacks. Then again, if you don't use https on the whole site, active attacks could already simply change the url of the iframe to be http and intercept that with sslstrip, and passive attacks could already steal cookies.
0x0 11y ago
I hope this is just bad wording and not a setting that actually disables certificate validation? They can't possibly mean it will accept even invalid SHA1 certificates? > security.pki.sha1_enforcement_level” to 0 (which will accept all SHA-1 certificates)
- alainv 11y ago
  As opposed to a tiered acceptance based on the issuance/expiry date of said certificate. https://support.globalsign.com/customer/portal/articles/1447169-sha-256-rollout https://support.globalsign.com/customer/portal/articles/1447...
- jvehent 11y ago
  Setting security.pki.sha1_enforcement_level to 0 will still only accept SHA-1 certs that are signed by a root CA in the NSS truststore. That setting only disables the SHA-1 deprecation logic.
ChuckMcM 11y ago
It was challenging trying to explain to my parents that firefox was complaining about an anti-virus maker's man-in-the-middle certificate under the heading "Safe browsing protection" which, oddly enough, only really tried to spoof Google, Yahoo!, Bing, and Microsoft domains.
baby 11y ago
What is the fix in the new firefox version? They removed these man-in-the-middle root certs from the store?
deleted 11y ago
[deleted]

97 points by jvehent 11y ago

The bug speak about some security scanners and antivirus products. But the thing which triggered was a malware. Oups! I should have said a potentially unwanted program.

jvehent 11y ago

For some background around the discovery and analysis of the issue, see this thread: https://groups.google.com/forum/#!topic/mozilla.dev.platform/ZNKxYgIk_Sg https://groups.google.com/forum/#!topic/mozilla.dev.platform...

JoshTriplett 11y ago

It's worth noting the reason why Mozilla made this change: not because they consider these systems acceptable, but because they can't even get telemetry data on the scope of the problem because the telemetry mechanism naturally also uses HTTPS, and because this issue prevents such users from getting updates to Firefox itself.

meowface 11y ago
Would they consider these systems to be necessarily unacceptable? Intercepting TLS at a corporate proxy is perfectly valid and necessary for a decent security program.
- pfg 11y ago
  Corporate proxies aren't the issue here; Outdated corporate proxies and other "security" software still issuing SHA-1 certs is what's causing this.
  - meowface 11y ago
    Yes, that part is definitely unacceptable.
- bbayles 11y ago
  I agree that it's perfectly valid, but disagree that it's necessary. Deploying proxies has costs - it obscures the endpoints of communication from sensor software and makes anomaly detection more difficult. Richard Bejtlich's "Practice of Network Security Monitoring" has a chapter dedicated to the costs and benefits of proxy deployments; I recommend the book for a look at one coherent method of network security monitoring.
  - AnthonyMouse 11y ago
    > Deploying proxies has costs - it obscures the endpoints of communication from sensor software and makes anomaly detection more difficult. It also establishes a single machine that sees all the plaintext of everything that should have been TLS encrypted from every machine on your network. It's like attacker catnip.
    - meowface 11y ago
      If an attacker is able to gain root access to your proxy, or inline with a TAP where your proxy is sending intercepted traffic to, you probably have much bigger problems.
      - AnthonyMouse 11y ago
        > If an attacker is able to gain root access to your proxy, or inline with a TAP where your proxy is sending intercepted traffic to, you probably have much bigger problems. Bigger problems than an attacker being able to decrypt and modify all of the TLS sessions in your company? If you have bigger problems than that then they've presumably spilled out of the realm of IT problems entirely and you're dealing with some kind of government lawyers or maybe a large uncontrollable fire.
        meowface 11y ago
        Being able to decrypt and modify TLS sessions pales in comparison to being able to access your domain controller, or dump all your databases.
- stdgy 11y ago
  I don't think they would. The issue isn't that traffic is being intercepted inside the enterprise. It's that the proxy performing the interception is issuing a certificate that uses SHA-1 in it's digital signing algorithm.
- wyldfire 11y ago
  I am probably in the minority here, but I don't agree. I understand why the security program does it and why they think they need to. I just think that, regardless of who owns this computer and the network it's connected to, if I'm using it, I should be able to use TLS without any interception.
  - kevinastone 11y ago
    I'm shocked to think this is a minority opinion. Please give us certificate pinning because this type of interception is completely hostile to the end user.
    - pfg 11y ago
      Pinning, as implemented by major browsers[1][2], doesn't prevent this. Private trust anchors are exempt from key pinning. This is deemed acceptable because in order for the proxy root to be trusted, it would have to be installed on your system, so whoever owns the proxy already has control over your client. If you think that using MitM proxies should be illegal for employers or other organizations providing clients, that's probably more of a legal discussion. I don't think there's necessarily a right to privacy when it comes to internet use at your workplace, as long as all parties are aware of this. [1]: https://www.chromium.org/Home/chromium-security/security-faq#TOC-How-does-key-pinning-interact-with-local-proxies-and-filters- https://www.chromium.org/Home/chromium-security/security-faq... [2]: https://wiki.mozilla.org/SecurityEngineering/Public_Key_Pinning#How_to_use_pinning https://wiki.mozilla.org/SecurityEngineering/Public_Key_Pinn...
      - edwintorok 11y ago
        Could Firefox display an icon or provide a visible warning to users when traffic is being intercepted? The root cert could've been installed by malware, no?
        JoshTriplett 11y ago
        This seems like a good first step: Firefox should display a persistent, unremovable notification bar that makes it clear that the connection appears MITMed. If people complain about that notification, the answer is "remove whatever malware you have, or complain to your network administrator".
chei0aiV 11y ago
They just need to merge the Tor Browser into Firefox and add a meek-like http-based pluggable transport, then they can get around these weird MITM boxes. They probably should have foreseen this and used OpenPGP-based updates over plain HTTP though.
- jvehent 11y ago
  The updates themselves are served over HTTP and signed, but the request that verifies an update is available is done over HTTPS.
revelation 11y ago
And their telemetry needs are superior to the actual privacy at stake here? And they are now providing an updated version of Firefox that merely flip-flops on the protection, instead of providing a message "hey, you're being intercepted"? I'm not naive, but I still think it's only to prudent to point out how ridiculous this sounds. In any case, it seems like Mozilla needs a bit of Skype-magic for their update process. Relying on the very thing you are patching with every minor version seems silly regardless.
- pfg 11y ago
  "Breaking" the browser for a large number of users will only lead to one thing: Users switching to a browser that still supports SHA-1 certs issued after Jan 1st, 2016. No privacy improvement there either. Additionally, there are many valid use-cases for replacing certificates, e.g. corporate proxies. They should just stop using outdated hashing algorithms for those certs. It's not Mozilla's place to decide whether that use-case is valid or not. SHA-1 was never fully disabled; it's just that certificates using SHA-1 issued after that date weren't accepted anymore. Telemetry is important to understand the ramifications of this issue. This change is likely to be reverted once Mozilla understands the implications. Take a look at the discussion on Mozilla's mailing list for more insight into their thinking[1]. [1]: https://groups.google.com/forum/#!topic/mozilla.dev.platform/ZNKxYgIk_Sg https://groups.google.com/forum/#!topic/mozilla.dev.platform...
- rcthompson 11y ago
  I think the idea is to first revert to a state where people behind this MITM boxes can receive updates to firefox, and then decide how to handle things from there.

Zarel 11y ago

This was a problem for Pokémon Showdown recently. We use HTTPS for logins and some other things, which stopped working a few days ago for users using MitM antiviruses and Firefox. https://twitter.com/TonyFlygon/status/684756701027954689 https://twitter.com/TonyFlygon/status/684756701027954689 (Example user complaint.) There's no way to detect whether or not an HTTPS iframe has failed to load, so my workaround was to fall back to HTTP if the HTTPS iframe didn't load within 2 seconds. We still switch the connection over to HTTPS if the iframe does eventually load. I'm kind of confused by why so many users thought it was a Pokemon Showdown issue, specifically. Doesn't Google default to HTTPS? PS shouldn't be the most significant website they have trouble with.

leesalminen 11y ago
Why not use HTTPS everywhere?
- Zarel 11y ago
  Well, we do support full-HTTPS, it just isn't required. If it were, PS would have been unusable to anyone with Firefox and Avast/BitDefender/etc. It also allows image embeds. Users often share HTTP images in the chatrooms, which browsers using the HTTPS site complain about. For some weird reason, Google Chrome doesn't support data-URIs in HTTPS when using HTML5 drag-and-drop to drag files from a website to the desktop, which requires an annoying workaround. In addition, most people wanting to set up a third-party PS server don't want to go through the hassle of acquiring a certificate. It makes the setup process a lot more complicated than just "clone the repository and run ./pokemon-showdown"
Buge 11y ago
That opens you up to any active attacker simply stopping traffic. You're usually safe against passive attacks if the network has no glitches, but completely vulnerable to active attacks. Then again, if you don't use https on the whole site, active attacks could already simply change the url of the iframe to be http and intercept that with sslstrip, and passive attacks could already steal cookies.

0x0 11y ago

I hope this is just bad wording and not a setting that actually disables certificate validation? They can't possibly mean it will accept even invalid SHA1 certificates? > security.pki.sha1_enforcement_level” to 0 (which will accept all SHA-1 certificates)

alainv 11y ago
As opposed to a tiered acceptance based on the issuance/expiry date of said certificate. https://support.globalsign.com/customer/portal/articles/1447169-sha-256-rollout https://support.globalsign.com/customer/portal/articles/1447...
jvehent 11y ago
Setting security.pki.sha1_enforcement_level to 0 will still only accept SHA-1 certs that are signed by a root CA in the NSS truststore. That setting only disables the SHA-1 deprecation logic.

ChuckMcM 11y ago

It was challenging trying to explain to my parents that firefox was complaining about an anti-virus maker's man-in-the-middle certificate under the heading "Safe browsing protection" which, oddly enough, only really tried to spoof Google, Yahoo!, Bing, and Microsoft domains.

baby 11y ago

What is the fix in the new firefox version? They removed these man-in-the-middle root certs from the store?

deleted 11y ago

[deleted]