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BlueCoat and other proxies hang up during TLS 1.3

bugs.chromium.org

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Re: BlueCoat and other proxies hang up during TLS 1.3

#81

Post by pjmlp »

jessaustin wrote: post #8
JoshTriplett wrote: post #2

Note that this happens even when using a BlueCoat proxy in non-MITM mode. BlueCoat tries to "analyze" TLS connections, and rejects anything it doesn't understand. This exact issue occurred with TLS 1.2 back when BlueCoat only understood 1.1/1.0. In this case, it doesn't sound like they're reverting it because of overall breakage, but rather because it breaks the tool that would otherwise be used to control TLS 1.3 tr…

This exact issue occurred with TLS 1.2 back when BlueCoat only understood 1.1/1.0. Good grief! From David Benjamin's final comment: Note these issues are always bugs in the middlebox products. TLS version negotiation is backwards compatible, so a correctly-implemented TLS-terminating proxy should not require changes to work in a TLS-1.3-capable ecosystem. It can simply speak TLS 1.2 at both client proxy and proxy ser…

They have many costumers on the Fortune 500 portfolio that make sure the workers only visit the web sites they should and also IT get to know when they misbehave.

Quite a pain to work in such environments.

Re: BlueCoat and other proxies hang up during TLS 1.3

#82

Post by jlgaddis »

coderobe wrote: post #3
JoshTriplett wrote: post #2

Note that this happens even when using a BlueCoat proxy in non-MITM mode. BlueCoat tries to "analyze" TLS connections, and rejects anything it doesn't understand. This exact issue occurred with TLS 1.2 back when BlueCoat only understood 1.1/1.0. In this case, it doesn't sound like they're reverting it because of overall breakage, but rather because it breaks the tool that would otherwise be used to control TLS 1.3 tr…

Rejecting anything it doesn't understand sounds like a bug to me. If it sees that it's TLS, it should attempt a protocol downgrade. There's absolutely no reason for this to break, as TLS 1.3 exists alongside TLS 1.2 (For now).

On the other hand, allowing stuff that you don't understand gives us things like the CSRF vulnerabilities in MongoDB and such.

In the case of a security appliance -- such as this -- it should, in my opinion, "fail closed".

Re: BlueCoat and other proxies hang up during TLS 1.3

#83

Post by fulafel »

wildmusings wrote: post #74
rossy wrote: post #52

Earlier quoted context omitted.

I think this SSL MITM thing has gone way too far. When an exec asks an engineer if it's possible to monitor all internet communication that goes in and out of the company network, including communication that is encrypted by TLS, the correct answer is no. In fact, this specific thing is what TLS is designed to prevent, and new implementations of the protocol are only going to get better at preventing it. The exec wil…

> In fact, this specific thing is what TLS is designed to prevent, and new implementations of the protocol are only going to get better at preventing it. This isn't true. The TLS protocol is not a philosophy; it does not have an opinion on who you should trust as a root certificate authority. If you trust a particular root, it is wholly within the design of TLS to allow connections that are monitored by whoever contr…

> > In fact, this specific thing is what TLS is designed to prevent, and new implementations of the protocol are only going to get better at preventing it.

> This isn't true. The TLS protocol is not a philosophy; [...]

Well, the TLS specification [1] says as the first sentence of the introduction:

"The primary goal of the TLS protocol is to provide privacy and data integrity between two communicating applications."

I think, if something is "the primary design objective of TLS", it can be said that TLS is designed to do it.

[1] https://tools.ietf.org/html/rfc5246#section-1

Re: BlueCoat and other proxies hang up during TLS 1.3

#84

Post by [deleted] »

zrm wrote: post #72
theluketaylor wrote: post #68

Earlier quoted context omitted.

>It's ineffective against insider exfiltration of data unless you're also doing body cavity searches for USB sticks, and if you're at that point then the sensitive network should not be connected to the internet at all. We opted to disable usb mass storage since cavity searches seemed a little much

> We opted to disable usb mass storage since cavity searches seemed a little much This is missing the point. Someone could plug a SATA drive directly into the motherboard, or otherwise compromise their work computer to disable the restrictions, or take pictures of documents with a camera, or bring their own computer on-site, or bring a line-of-sight wireless network device on-site, or send the data over the internet…

[deleted]

Re: BlueCoat and other proxies hang up during TLS 1.3

#85

Post by semi-extrinsic »

jessaustin wrote: post #8
JoshTriplett wrote: post #2

Note that this happens even when using a BlueCoat proxy in non-MITM mode. BlueCoat tries to "analyze" TLS connections, and rejects anything it doesn't understand. This exact issue occurred with TLS 1.2 back when BlueCoat only understood 1.1/1.0. In this case, it doesn't sound like they're reverting it because of overall breakage, but rather because it breaks the tool that would otherwise be used to control TLS 1.3 tr…

This exact issue occurred with TLS 1.2 back when BlueCoat only understood 1.1/1.0. Good grief! From David Benjamin's final comment: Note these issues are always bugs in the middlebox products. TLS version negotiation is backwards compatible, so a correctly-implemented TLS-terminating proxy should not require changes to work in a TLS-1.3-capable ecosystem. It can simply speak TLS 1.2 at both client proxy and proxy ser…

There was a paper posted on HN a few weeks back by some pretty serious security researchers on the security risks of SSL MITM boxes.

https://jhalderm.com/pub/papers/interception-ndss17.pdf

How do you fix this when you're naught but a humble employee? Well, a friend of mine worked at a fairly large tech company where a salesguy for these boxes had convinced the CTO they had to have them. Every tech-person "on the floor" hated the idea, so before the boxes were installed they conspired on their free time to write some scripts that ran lots of legitimate HTTPS traffic, effectively DDOSing the boxes and bringing the company's internet to a crawl for the day, like Google would take ten seconds to open. Then obviously everyone (including the non-tech people) started calling the IT helpdesk complaining that the internet was broken. MITM box salesguy then had to come up with a revised solution, costing 20x more than his first offer, and that was the end of that.

If you already are suffering under MITM boxes, a similar strategy with a slow ramp-up in traffic might work.

Re: BlueCoat and other proxies hang up during TLS 1.3

#86

Post by jlgaddis »

zrm wrote: post #72
theluketaylor wrote: post #68

Earlier quoted context omitted.

>It's ineffective against insider exfiltration of data unless you're also doing body cavity searches for USB sticks, and if you're at that point then the sensitive network should not be connected to the internet at all. We opted to disable usb mass storage since cavity searches seemed a little much

> We opted to disable usb mass storage since cavity searches seemed a little much This is missing the point. Someone could plug a SATA drive directly into the motherboard, or otherwise compromise their work computer to disable the restrictions, or take pictures of documents with a camera, or bring their own computer on-site, or bring a line-of-sight wireless network device on-site, or send the data over the internet…

And the A-Team could land on the roof with a helicopter in the middle of the night, take control of the building, breach the data center, and physically steal and leave with all the servers.

Yes, if one is determined enough, they will find a way to steal data.

> It isn't worth the security cost.

That's up for the company to decide... and apparently they have decided that it is worth the cost, regardless of what zrm, random person on the Internet, thinks.

Re: BlueCoat and other proxies hang up during TLS 1.3

#87

Post by deathanatos »

jlgaddis wrote: post #82
coderobe wrote: post #3

Earlier quoted context omitted.

Rejecting anything it doesn't understand sounds like a bug to me. If it sees that it's TLS, it should attempt a protocol downgrade. There's absolutely no reason for this to break, as TLS 1.3 exists alongside TLS 1.2 (For now).

On the other hand, allowing stuff that you don't understand gives us things like the CSRF vulnerabilities in MongoDB and such. In the case of a security appliance -- such as this -- it should, in my opinion, "fail closed".

Sorry, no. TLS is explicitly designed to allow smooth upgrading like this. This proxy is supposed to (in response to a client hello w/ TLSv1.3) respond with TLSv1.2 if that's what it supports. This is still a rigorous parsing of the input being given: nothing is "not understood": version negotiation is an inherent part of the protocol and is supposed to allow for painless upgrades to more secure protocols.

The RFC (which if you're implementing TLS, you should have open at all times) explicitly calls out exactly this behavior:

> Note: some server implementations are known to implement version negotiation incorrectly. For example, there are buggy TLS 1.0 servers that simply close the connection when the client offers a version newer than TLS 1.0.

The quality of this vendor's implementation is extremely suspect.

Re: BlueCoat and other proxies hang up during TLS 1.3

#88

Post by jlgaddis »

zrm wrote: post #54
wildmusings wrote: post #22

Earlier quoted context omitted.

Without an SSL MITM, Intrusion Detection Systems (IDS's) are much less effective. If you're using your company's network, then they have every right to monitor all of the activity on it. They're trying to protect trade secrets, future plans, customer data, employee records, etc. from attackers who would use that information to do harm to the company, its customers, and its employees. If you don't want your employer t…

> If you're using your company's network, then they have every right to monitor all of the activity on it. It isn't a question of whether they're allowed to do it, it's a question of whether they should do it. It's ineffective against insider exfiltration of data unless you're also doing body cavity searches for USB sticks, and if you're at that point then the sensitive network should not be connected to the internet…

> It's ineffective against insider exfiltration of data unless you're also doing body cavity searches for USB sticks ...

I dunno. I know plenty of people who might want to work on an Excel spreadsheet at home over the weekend and so might e-mail it to their personal e-mail account. They would almost certainly reconsider, however, if it required copying that spreadsheet to a flash drive that they then had to hide in their ass, though.

In that case, it sounds like the device is effective after all.

Re: BlueCoat and other proxies hang up during TLS 1.3

#89

Post by DanielDent »

quotemstr wrote: post #4
JoshTriplett wrote: post #2

Note that this happens even when using a BlueCoat proxy in non-MITM mode. BlueCoat tries to "analyze" TLS connections, and rejects anything it doesn't understand. This exact issue occurred with TLS 1.2 back when BlueCoat only understood 1.1/1.0. In this case, it doesn't sound like they're reverting it because of overall breakage, but rather because it breaks the tool that would otherwise be used to control TLS 1.3 tr…

Ridiculously conservative middleboxes are why we can't have nice things and why we need to encrypt all new protocols, security properties aside.

This is precisely the conclusion Google reached and has used as they work on QUIC.

Even protocol state (equivalents of TCP FIN/SYN/etc) is encrypted, to ensure that middleboxes don't get ideas about what the protocol is 'supposed' to do - ideas which make it hard to change the protocol in the future.

Re: BlueCoat and other proxies hang up during TLS 1.3

#90

Post by db48x »

wildmusings wrote: post #22
db48x wrote: post #10

The long-term solution is simply not to work anywhere that insists on running a MITM attack on all of your communications.

Without an SSL MITM, Intrusion Detection Systems (IDS's) are much less effective. If you're using your company's network, then they have every right to monitor all of the activity on it. They're trying to protect trade secrets, future plans, customer data, employee records, etc. from attackers who would use that information to do harm to the company, its customers, and its employees. If you don't want your employer t…

I agree that this is how they see it, but it's a losing battle. There's no filter for people's minds, or for what they write down. The owner of a company cannot approach this problem from the perspective of technical bandaids; they absolutely must trust the right people, and only the right people.
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