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> 'This certificate is issued by the IT department of your organization and let's them see all encrypted traffic' I'm a bit out of the loop on modern security

> 'This certificate is issued by the IT department of your organization and let's them see all encrypted traffic' I'm a bit out of the loop on modern security implementations. In theory though, I thought the purpose of certificates and certificate authorities was to certify that you're actually talking to who you think you're talking to? A browser can still communicate security with any computer out there, regardless of corporate certs, etc. Or do the corporate firewalls block communications that they cannot inspect?

20after4 3y ago
TL;DR: The certificate is associated with a private key which can decrypt the traffic for a session established using the cert. The issue is that, given a bogus certificate from a trusted authority, someone can impersonate any site they want, then proxy the traffic to the real site and spy on your session. Longer explanation: If an organization is able to obtain a certificate that the browser trusts, which matches the domain name you are visiting, then they can easily terminate the TLS at the organization's server, then make a new request to the site, where the encrypted session is between the site and the organization's proxy server. They get an effective man-in-the-middle attack and your browser pretends like everything is secure because there is a trusted certificate matching the domain name you visited. The browser doesn't throw up any red flags because it doesn't differentiate between certificates, only certificate authorities. So if a 3rd party can acquire an arbitrary certificate for some domain, and the 3rd party has the private key associated with that cert, and the same 3rd party can intercept the traffic between you and the domain in question, then they can get your traffic in the clear and there are no obvious signs that they did it. Given the current state of TLS and the way browsers deal with certs, the only way for a user to discover that something is amiss is to investigate the details of the cert. Then they might notice that it was issued by a suspicious certificate authority. Unfortunately, the proposed EU law is attempting to prohibit browser vendors from withholding trust (or otherwise scrutinizing) the state-controlled (or state-influenced) certificate authorities, with the intention of preventing browsers from interfering with government's ability to issue illegitimate/insecure (but you must trust them, or else!) certificates.
vkaku 3y ago
In theory, you know whom you are talking to. In practice though, every company and authoritarian government wants to sniff, be it through https proxies or enterprise-wide certificates.
alfons_foobar 3y ago
Your understanding is correct, but if your IT department puts a wildcard cert on your machine, it can MitM all your traffic (e.g. your company's firewall can say "Hi I am $SITE, here's a certificate to prove it" and your browser will accept it). Traffic between you and the firewall, as well as between the firewall and the actual site is still encrypted.
tonyarkles 3y ago
> A browser can still communicate security with any computer out there, regardless of corporate certs, etc. Or do the corporate firewalls block communications that they cannot inspect? Yes, you’ve got it. Many corporate firewalls require you to install their own root CA certificate and “transparently” intercept and rewrite traffic leaving the network. It looks like you’re negotiating with the external site, but you’re actually doing TLS negotiation with an on-prem proxy that connects to the destination site on your behalf. I say “transparently” in quotes because it definitely, in practice, breaks things here and there.
- Buttons840 3y ago
  I'm sure it's well established practice, and the courts would find it legal, but it seems like fraud. My computer says "I want to connect to my bank, are you my bank?" and the corporate firewall says "yes, I am your bank".
  - tonyarkles 3y ago
    I think the loophole and why it's legal is this: > My computer says It's not your computer. It's the company's computer and they installed the root certificate on it. For any non-provisioned machine you'd get a certificate error because the corporate-issued certificates are signed by the corporate CA that isn't browser-approved by default.
NovemberWhiskey 3y ago
Your IT department owns a certificate authority. They add its self-signed, root certificate to the trust stores of all the machines in your firm using group policies or whatever. They then install something like a Bluecoat browsing proxy, which they configure your browsers to use using group policies or whatever. The Bluecoat terminates the TLS connection by transparently providing certificates for the sites that you're trying to access, which your browser trusts. It then makes the outbound connection to the actual site, if appropriate. It's called TLS interception.
immibis 3y ago
User-friendly recognition means some way to say this is a certificate from John Doe, France. Probably a green box in the URL bar like EV certificates used to be, but maybe blue instead. Someone has to explain the threat model to me better. If I go to google.com and the certificate says the site is owned by John Doe (France) I should be suspicious. Is the problem that the certificate validates something other than the domain name? Any government can already easily get a domain certificate for google.com.

20after4 3y ago

TL;DR: The certificate is associated with a private key which can decrypt the traffic for a session established using the cert. The issue is that, given a bogus certificate from a trusted authority, someone can impersonate any site they want, then proxy the traffic to the real site and spy on your session. Longer explanation: If an organization is able to obtain a certificate that the browser trusts, which matches the domain name you are visiting, then they can easily terminate the TLS at the organization's server, then make a new request to the site, where the encrypted session is between the site and the organization's proxy server. They get an effective man-in-the-middle attack and your browser pretends like everything is secure because there is a trusted certificate matching the domain name you visited. The browser doesn't throw up any red flags because it doesn't differentiate between certificates, only certificate authorities. So if a 3rd party can acquire an arbitrary certificate for some domain, and the 3rd party has the private key associated with that cert, and the same 3rd party can intercept the traffic between you and the domain in question, then they can get your traffic in the clear and there are no obvious signs that they did it. Given the current state of TLS and the way browsers deal with certs, the only way for a user to discover that something is amiss is to investigate the details of the cert. Then they might notice that it was issued by a suspicious certificate authority. Unfortunately, the proposed EU law is attempting to prohibit browser vendors from withholding trust (or otherwise scrutinizing) the state-controlled (or state-influenced) certificate authorities, with the intention of preventing browsers from interfering with government's ability to issue illegitimate/insecure (but you must trust them, or else!) certificates.

vkaku 3y ago

In theory, you know whom you are talking to. In practice though, every company and authoritarian government wants to sniff, be it through https proxies or enterprise-wide certificates.

alfons_foobar 3y ago

Your understanding is correct, but if your IT department puts a wildcard cert on your machine, it can MitM all your traffic (e.g. your company's firewall can say "Hi I am $SITE, here's a certificate to prove it" and your browser will accept it). Traffic between you and the firewall, as well as between the firewall and the actual site is still encrypted.

tonyarkles 3y ago

> A browser can still communicate security with any computer out there, regardless of corporate certs, etc. Or do the corporate firewalls block communications that they cannot inspect? Yes, you’ve got it. Many corporate firewalls require you to install their own root CA certificate and “transparently” intercept and rewrite traffic leaving the network. It looks like you’re negotiating with the external site, but you’re actually doing TLS negotiation with an on-prem proxy that connects to the destination site on your behalf. I say “transparently” in quotes because it definitely, in practice, breaks things here and there.

Buttons840 3y ago
I'm sure it's well established practice, and the courts would find it legal, but it seems like fraud. My computer says "I want to connect to my bank, are you my bank?" and the corporate firewall says "yes, I am your bank".
- tonyarkles 3y ago
  I think the loophole and why it's legal is this: > My computer says It's not your computer. It's the company's computer and they installed the root certificate on it. For any non-provisioned machine you'd get a certificate error because the corporate-issued certificates are signed by the corporate CA that isn't browser-approved by default.

NovemberWhiskey 3y ago

Your IT department owns a certificate authority. They add its self-signed, root certificate to the trust stores of all the machines in your firm using group policies or whatever. They then install something like a Bluecoat browsing proxy, which they configure your browsers to use using group policies or whatever. The Bluecoat terminates the TLS connection by transparently providing certificates for the sites that you're trying to access, which your browser trusts. It then makes the outbound connection to the actual site, if appropriate. It's called TLS interception.

immibis 3y ago

User-friendly recognition means some way to say this is a certificate from John Doe, France. Probably a green box in the URL bar like EV certificates used to be, but maybe blue instead. Someone has to explain the threat model to me better. If I go to google.com and the certificate says the site is owned by John Doe (France) I should be suspicious. Is the problem that the certificate validates something other than the domain name? Any government can already easily get a domain certificate for google.com.