Squid + https

[techtester-m]

@DaddyGo @Gertjan A MITM can intercept PKs easily, but he would need his CA to be installed on the client's side.
But what prevents a MITM to simply forward you the certificate it received from the original destination?

Such an attempt would fail because the client's browser would see the mismatch between the cert and the source address/domain of the MITM, right? Feels like such a basic question but still...

I just wanna make sure I fully understand it.

From what I've read the combination between RSA encryption/PKs & Certificate authentication is as secure as it gets so long the end user hasn't installed any CA other than what is already trusted by the browser.

[DaddyGo]

@techtester-m

nowadays, due to the development of physical hardware, this caching is not really interesting, on small-scale systems

a proxy can help for clusters with hundreds of users if you always have to load the same content

and behind a proxy, a lot of things can be well hidden

but as mentioned https and all its advantages, it becomes a disadvantage here
everyone is try hiding something

[techtester-m]

@DaddyGo said in Squid + https:

and behind a proxy, a lot of things can be well hidden

A VPN server would do the job without MITM stuff :)

[DaddyGo]

@techtester-m

In the past, I worked as a sysadmin for a company, with 2 800-2 900 direct workstations

well then and there the proxy was good, it kept the stupidity of the employees in check

the VPN also obscures everything, just a little differently than, for example, the intranet proxy on a campus network

[techtester-m]

@DaddyGo Is there a good way to prevent http access and force https without installing browser add-ons?

via pfSense, Pi-hole etc. maybe?

Also, things like squid are great when you wanna know the content of whatever your employees do centralized in one place, but I guess there's many software solutions to do that on each device owned by the company.

[DaddyGo]

@techtester-m said in Squid + https:

Is there a good way to prevent http access and force https without installing browser add-ons?
via pfSense, Pi-hole etc. maybe?

slowly wear out the "http" ...
disable port 80, though that would still be crazy, hahaha

I think the pi-hole is forgettable, here is the great Unbound + pfBlockerNG pair

@techtester-m "Also, things like squid are great when you wanna know the content of whatever your employees do centralized in one place, but I guess there's many software solutions to do that on each device owned by the company."

don't think, that...
big companies are the driest jobs, even though I worked as an outside worker...hmmmm

they invest in an IT structure and after that they think it will work forever

I have a friend who works for a very large company (their names are not public, because you would faint if you knew) and still runs Win7 on VM (hypv) enviroment with Citrix
as management regrets the money, for out of date Win7 replacements

[techtester-m]

@DaddyGo said in Squid + https:

disable port 80, though that would still be crazy

That's too much haha. I want to do what "https everywhere" does but on the pfsense or other end equipment and without breaking internal pc/os stuff. On a DNS level basically but on the other hand how do you determine what comes from browsing and what not...

@DaddyGo said in Squid + https:

I think the pi-hole is forgettable, here is the great Unbound + pfBlockerNG pair

DNS is probably one of the only services I wouldn't mind to "outsource" from the firewall. Especially when Pi-hole is much more organized, visual and has a bunch of people who all they do everyday 24/7 is trying improve it.
An entire project dedicated solely to DNS.
pfBlockerNG is at the end of the day a package. I'd still use it as an IP blocker though :)

@DaddyGo said in Squid + https:

their names are not public, because you would faint if you knew

Crazy! With all the money these companies have they still try to save as much as possible and be cheap, even when it's in their best interest to invest it hahaha unbelievable.

[DaddyGo]

@techtester-m

Hmmm HTTP...

with http you you can't start anything this is a webserver question, for example on a web server in the .htaccess file all http must be redirected to https
plus Let'sE certificate and that's about

only web masters are lazy, cca. 10 minutes job it

you don't think so,.. the Pi-hole is just popular and beautiful nothing more
(I apologize to all the Pi-hole fans) - perfect for raspberry pi

Unbound + DoT + DNSSEC + CF DNS servers and pfBlockerNG -devel, it is a professional solution

+++edit:
people tend to overcomplicate everything even though it is simple and everything is included in pfSense (more or less)

[techtester-m]

@DaddyGo said in Squid + https:

Unbound + DoT + DNSSEC + CF DNS servers and pfBlockerNG

That's exactly what I use! But...except for the fact that it's AIO solution + IP blocking what would be another advantage of pfBlocker over Pi-Hole (DNS wise)? Also, I've seen more lists and just info in general about Pi-Hole and as I said it seems much more organized, visual etc.

One last question if you may.
What happens when/if a MITM has its PK signed by a trusted CA? Would it still break because the browser will check from which domain/address the data came from resulting in a mismatch between what the client requested and the source?

[DaddyGo]

@techtester-m

pfBlockerNG does exactly the same thing as Pi-hole, only better
mainly because it does with a professional DNS resolver, which is Unbound
don't be fooled by the look...(GUI, etc) - Pi-hole

professional stuff usually doesn't even have a GUI, just a CLI
just look at Brocade, Juniper, etc. switches or Cisco enterprise devices
pfBlockerNG has a clean design and what is good can be set even by those who don't understand it so much

the browser only sees the Squid internal certificate behind the proxy
he does not even know the existence of the original certificate

[techtester-m]

@DaddyGo said in Squid + https:

professional stuff usually doesn't even have a GUI, just a CLI

I know, but it's not only the GUI part here. It's an entire dedicated solution for one single task - "DNSing", but I'll search for some good lists for pfBlockerNG and see.

@DaddyGo said in Squid + https:

mainly because it does with a professional DNS resolver

I forward the requests anyway, because the 13 DNS root servers don't support DoT (yet).
With Pi-Hole it would be DoH because they don't support DoT yet for some reason.

[techtester-m]

@DaddyGo @Gertjan Do any of you know how does a certificate validation works exactly, in technical details?
I just posted it on security.stackexchange but decided to try and ask you guys as well :)

I've read this post - https://security.stackexchange.com/questions/135401/certificate-validation,
where it says this : "...an attacker can still take the whole signed content and present it to you but won't be able to change any details or the signature won't match."

My questions are these:
(1) How does the browser validates the details of a certificate and see its content like: domain name etc.? Knowing that the cert is encrypted.
(2) If a MITM wanna change anything he would need to decrypt the cert, which is impossible, or simply change what he wants but then fail at the browser because, as mentioned above, the signature won't match?

Thank you,

[DaddyGo]

@techtester-m said in Squid + https:

but I'll search for some good lists for pfBlockerNG and see.

in the "devel" version have a lot of built-in lists, but I also have a lot of collected lists

don't be fooled by the word = DEVEL - this current / actual version

[Gertjan]

@techtester-m said in Squid + https:

Do any of you know how does a certificate validation works exactly, in technical details?

Yep.
Have a look at least 10 videos from this list https://www.youtube.com/results?search_query=https+certificate+how+it+works

Added to that :
In a perfect world, DNS is non spoofable (because you use the Resolver and DNSSEC ;) ), your app will know for sure what the real IP of a site is.

The important things :
In a certificate, you find the dates of validity,
The CA, used to certify that the certicate is valid. An OS, web browser, app, whatever, sues a build in list with known trusted CA's - and take note : you can add your own CA .... you can become a CA for your own network.
In a certificate is embedded the domain name or even a root domain name :

[techtester-m]

@Gertjan @DaddyGo I already knew about the certificate itself and I myself have signed or got signed by a trusted one etc. All I wanted to know is the security mechanism(s) that prevent MITM. Yesterday I did more reading on the subject and on digital signatures as well and understood everything I wanted to understand and know. It took a few hours over 1-2 days but Hopefully it'll be stored in my head forever haha

As I understand it - Unless a MITM got the end user to trust his CA, the attack will fail.

It would fail because:

(A) MITM would try and send his own PK and the browser will give warning.
(B) MITM must send his own PubK in order to encrypt/decrypt the content with his Private Key which is the key to everything here basically.
(C) If MITM changes anything in the message that comes with the certificate, like the domain name etc. the signature verifying algorithm would fail and the browser will give warning.
(D) No CA would sign fraudulent certificate unless they wanna go bankrupt and get sued.
(E) Even if a MITM sends the end user the exact same certificate he himself got from let's say Google then the browser might think for the first time that it's talking to Google but the next communication would fail because it would be encrypted with Google's PubK and could be decrypted only with Google's Private-Key so the MITM won't be able to read anything, there will be a connection time out and the attack would fail.
(F) I'm sure there are few more reasons...

Thank you guys for all your help, input and knowledge. A pleasure as always :)

[viberua]

Hello,
Can you help me find solution?
I've added CA of our domain controller in System > Cert Manager

But in squid SSL MITM i can't select this CA and enable SSL filtering. Only "None" can select.

How i can set up domain CA for enabling SSL filtering ?
Or pfsense can only accept self made cert from internal CA?
Thanks in advance.

[techtester-m]

@viberua I'm no expert at all on the matter but it tells you to create your own on pfSense, because it needs to be able to create certs on demand and locally...I think, but again..no expert.

[Gertjan]

Never used squid before, but I guess a CA should be created first.
Here :

Then, based on the CA, you create your certs :

These certs can be used in OpenVPN, FreeRadius, the pfSense GUI, etc.
CA's can't be use directly, except for signing (your own) certs.

[DaddyGo]

@Gertjan said in Squid + https:

Never used squid before, but I guess a CA should be created first.
Here :

exactly,
use the pfSense certificate builder and then it will appear in Squid settings

then you can also export it for installation on external devices

like:

[viberua]

@DaddyGo so if i don't want create new CA because i already have one, then i can't use this external CA cert in MITM?