10 ms·

Google disables “domain fronting” capability used to evade censors

80 points by okket 9y ago

StavrosK 9y ago
Would someone be able to block packets more easily or less easily if TLS didn't have the domain name in the packet in plaintext? Presumably someone couldn't tell where the packet was going, but that might mean you have to send it to the right server in the first place.
- dvno42 9y ago
  If you could remove the common name/url from the clear text portion of the packet, that would make filtering the web site more difficult. Some enterprise firewalls/filters look at the CN to match against a ratings database in lieu of DPI-SSL/MITM. Ex: https://itzecurity.blogspot.com/2014/05/configuring-fortios-v50-webfiltering.html https://itzecurity.blogspot.com/2014/05/configuring-fortios-...
  - yardstick 9y ago
    I suspect if encrypted SNI became popular, you would find them censored via one means or another. I imagine state operators have the resources to scan all domains, connect to them to identify their content and just blacklist their IPs (along with any innocent domains hosted on the same IP). I could also see state operators mandating the plaintext SNI (by dropping non-SNI TLS), and operating a transparent TLS proxy based on that SNI with their own DNS lookup (so you would have to provide a legit, resolvable hostname in the plaintext SNI).
- icebraining 9y ago
  SNI is used to allow the frontend gateway to select the correct certificate; it should be harder to block if the frontend gateway instead had a single certificate with all the domains it proxied (obviating the need for SNI). Of course, that means the gateway must terminate the TLS connection for every site (and therefore be able to read its contents), whereas with SNI it could redirect the TLS connection itself to the appropriate server, while being unable to spy on it. In practice what happened before SNI is that every SSL/TLS site used a dedicated IP, which makes it quite easy to block.
  - StavrosK 9y ago
    I meant something more like encrypted SNI in TLS 1.3[1], but that has covering as an explicit design goal, so I guess that answers my question. Still, it's a matter of politics, and not of technology. Google here chooses to stop covering for Telegram/Signal, even if the technology allows it. [1]: https://www.ietf.org/proceedings/94/slides/slides-94-tls-8.pdf https://www.ietf.org/proceedings/94/slides/slides-94-tls-8.p...
breakingcups 9y ago
What fortunate timing.
- kome 9y ago
  What fortunate timing indeed. That's just a kind reminder about what the interests of Google and Amazon are. Not those of their consumers for sure. Also, especially Google have all the interest to let the Russians destroy Telegram. At this point I would be very suspicious of all other messengers that still work in Russia. Edit: also Amnesty International is on it: https://twitter.com/amnesty/status/986955700550144002 https://twitter.com/amnesty/status/986955700550144002
  - baybal2 9y ago
    >At this point I would be very suspicious of all other messengers that still work in Russia. That's a conjecture is rational, but I think you already have to be very suspicious of anything that worked there for last 5 years, Telegram inclusively. It is unbelievable for me that they maintained legal presence in the country up until now, while all others were indiscriminately blocked years ago, and incompliant software authors were raided by 3 letter agencies and raped with assault rifles.
    - kome 9y ago
      Others were "indiscriminately blocked years ago"? Do you have a source for that? As far I know - but I might be wrong - Google, Facebook, Instagram or Whatsapp have never been blocked in Russia.
      - baybal2 9y ago
        BBM public server was certainly blocked as early as 5 years ago. Blackphone servers at around 4 or 3 years ago as well, just few months after its market release (while signal is still available though) All modded GSM phones were under blanket ban for even longer. Modded GSM phone vendors are routinely raided. Then Line, KaoKao and gazillion of others. There is no doubt that they were very deliberate in targeting anything with hard crypto. FB, and Google are routinely complying with Russians, so no wonder about them still being there.
tribby 9y ago
awful news, but not the end just yet - hopefully amazon and azure stay viable for meek.
etaioinshrdlu 9y ago
This seems like something you could do yourself on a VM instance, no?
- rocqua 9y ago
  It helps a lot more to masquerade as google.com than it does to masquarade as etaioinshrdlu.com. The censors would need to think more about blocking something as big a google than a single use-domain.
  - etaioinshrdlu 9y ago
    That explains it.
est 9y ago
Another reason why Google/Amazon is too centralized to be a single point of failure. We need more decentralized Internet. Not more clever hacks.
- Lionsion 9y ago
  > Another reason why Google/Amazon is too centralized to be a single point of failure. > We need more decentralized Internet. Not more clever hacks. IIRC, didn't domain fronting only work because Google/Amazon were thought to be too big to block? IMHO, what we need is a stronger consensus that Western companies shouldn't let themselves be bullied by censorious regimes dangling the promise of profits or access. They shouldn't be allowed to defend such decisions as profit-seeking amorality.
- Shorel 9y ago
  In this particular case, the problem is not Google or Amazon. They are technology providers and isolating each of their customers is actually a good thing. The problem is the Internet censoring by governments.
vatueil 9y ago
Previous discussion: https://news.ycombinator.com/item?id=16868564 https://news.ycombinator.com/item?id=16868564 As was brought up in the previous thread, though only briefly mentioned in the linked article, domain fronting is used by malware as well. It was allegedly exploited by Russian state-sponsored hacking group APT29.[0][1] It's unfortunate that it can't be used to help avoid censorship either now, but it was never an intended feature. As the article quotes, other CDNs such as Cloudfront also do not support domain fronting. [0]: https://www.fireeye.com/blog/threat-research/2017/03/apt29_domain_frontin.html https://www.fireeye.com/blog/threat-research/2017/03/apt29_d... [1]: https://www.cyberark.com/threat-research-blog/red-team-insights-https-domain-fronting-google-hosts-using-cobalt-strike/ https://www.cyberark.com/threat-research-blog/red-team-insig...
chisleu 9y ago
You can still use ELB's to hide behind amazon.com, right?

80 points by okket 9y ago

Would someone be able to block packets more easily or less easily if TLS didn't have the domain name in the packet in plaintext? Presumably someone couldn't tell where the packet was going, but that might mean you have to send it to the right server in the first place.

dvno42 9y ago
If you could remove the common name/url from the clear text portion of the packet, that would make filtering the web site more difficult. Some enterprise firewalls/filters look at the CN to match against a ratings database in lieu of DPI-SSL/MITM. Ex: https://itzecurity.blogspot.com/2014/05/configuring-fortios-v50-webfiltering.html https://itzecurity.blogspot.com/2014/05/configuring-fortios-...
- yardstick 9y ago
  I suspect if encrypted SNI became popular, you would find them censored via one means or another. I imagine state operators have the resources to scan all domains, connect to them to identify their content and just blacklist their IPs (along with any innocent domains hosted on the same IP). I could also see state operators mandating the plaintext SNI (by dropping non-SNI TLS), and operating a transparent TLS proxy based on that SNI with their own DNS lookup (so you would have to provide a legit, resolvable hostname in the plaintext SNI).
icebraining 9y ago
SNI is used to allow the frontend gateway to select the correct certificate; it should be harder to block if the frontend gateway instead had a single certificate with all the domains it proxied (obviating the need for SNI). Of course, that means the gateway must terminate the TLS connection for every site (and therefore be able to read its contents), whereas with SNI it could redirect the TLS connection itself to the appropriate server, while being unable to spy on it. In practice what happened before SNI is that every SSL/TLS site used a dedicated IP, which makes it quite easy to block.
- StavrosK 9y ago
  I meant something more like encrypted SNI in TLS 1.3[1], but that has covering as an explicit design goal, so I guess that answers my question. Still, it's a matter of politics, and not of technology. Google here chooses to stop covering for Telegram/Signal, even if the technology allows it. [1]: https://www.ietf.org/proceedings/94/slides/slides-94-tls-8.pdf https://www.ietf.org/proceedings/94/slides/slides-94-tls-8.p...

breakingcups 9y ago

What fortunate timing.

kome 9y ago
What fortunate timing indeed. That's just a kind reminder about what the interests of Google and Amazon are. Not those of their consumers for sure. Also, especially Google have all the interest to let the Russians destroy Telegram. At this point I would be very suspicious of all other messengers that still work in Russia. Edit: also Amnesty International is on it: https://twitter.com/amnesty/status/986955700550144002 https://twitter.com/amnesty/status/986955700550144002
- baybal2 9y ago
  >At this point I would be very suspicious of all other messengers that still work in Russia. That's a conjecture is rational, but I think you already have to be very suspicious of anything that worked there for last 5 years, Telegram inclusively. It is unbelievable for me that they maintained legal presence in the country up until now, while all others were indiscriminately blocked years ago, and incompliant software authors were raided by 3 letter agencies and raped with assault rifles.
  - kome 9y ago
    Others were "indiscriminately blocked years ago"? Do you have a source for that? As far I know - but I might be wrong - Google, Facebook, Instagram or Whatsapp have never been blocked in Russia.
    - baybal2 9y ago
      BBM public server was certainly blocked as early as 5 years ago. Blackphone servers at around 4 or 3 years ago as well, just few months after its market release (while signal is still available though) All modded GSM phones were under blanket ban for even longer. Modded GSM phone vendors are routinely raided. Then Line, KaoKao and gazillion of others. There is no doubt that they were very deliberate in targeting anything with hard crypto. FB, and Google are routinely complying with Russians, so no wonder about them still being there.

tribby 9y ago

awful news, but not the end just yet - hopefully amazon and azure stay viable for meek.

etaioinshrdlu 9y ago

This seems like something you could do yourself on a VM instance, no?

rocqua 9y ago
It helps a lot more to masquerade as google.com than it does to masquarade as etaioinshrdlu.com. The censors would need to think more about blocking something as big a google than a single use-domain.
- etaioinshrdlu 9y ago
  That explains it.

est 9y ago

Another reason why Google/Amazon is too centralized to be a single point of failure. We need more decentralized Internet. Not more clever hacks.

Lionsion 9y ago
> Another reason why Google/Amazon is too centralized to be a single point of failure. > We need more decentralized Internet. Not more clever hacks. IIRC, didn't domain fronting only work because Google/Amazon were thought to be too big to block? IMHO, what we need is a stronger consensus that Western companies shouldn't let themselves be bullied by censorious regimes dangling the promise of profits or access. They shouldn't be allowed to defend such decisions as profit-seeking amorality.
Shorel 9y ago
In this particular case, the problem is not Google or Amazon. They are technology providers and isolating each of their customers is actually a good thing. The problem is the Internet censoring by governments.

vatueil 9y ago

Previous discussion: https://news.ycombinator.com/item?id=16868564 https://news.ycombinator.com/item?id=16868564 As was brought up in the previous thread, though only briefly mentioned in the linked article, domain fronting is used by malware as well. It was allegedly exploited by Russian state-sponsored hacking group APT29.[0][1] It's unfortunate that it can't be used to help avoid censorship either now, but it was never an intended feature. As the article quotes, other CDNs such as Cloudfront also do not support domain fronting. [0]: https://www.fireeye.com/blog/threat-research/2017/03/apt29_domain_frontin.html https://www.fireeye.com/blog/threat-research/2017/03/apt29_d... [1]: https://www.cyberark.com/threat-research-blog/red-team-insights-https-domain-fronting-google-hosts-using-cobalt-strike/ https://www.cyberark.com/threat-research-blog/red-team-insig...

chisleu 9y ago

You can still use ELB's to hide behind amazon.com, right?