[squid-users] Transparent proxy for WiFi users

Amos Jeffries squid3 at treenet.co.nz
Wed Jan 3 12:16:27 UTC 2018

On 03/01/18 10:15, Yuri wrote:
> 03.01.2018 02:13, Amos Jeffries пишет:
>> On 03/01/18 02:48, Roberto Carna wrote:
>>> Dear, I've setup a Squid transparent proxy + Squidgard on pfSEnse 2.4
>>> in order to filter HTTP and HTTPS web content for different types of
>>> WiFi clients on my company:
>>> - Android (different versions)
>>> - Notebooks Windows 7/10
>>> - Iphone
>>> - Etc.
>>> In some cases, depending on the device Operating System, some apps
>>> experiment problems, for example Facebook and some others.
>> The main cause of these problems is that when the same vendor is
>> authoring both the server software and the client "app" (or client
>> device OS). They can (and often do) hard-code TLS certificate checks
>> into their client code to detect and immediately fail in the presence
>> of MITM in the encryption.
>> Following that, SSL-Bump is still very much an ongoing project.
>> Selecting even a slightly older Squid version can lead to TLS features
>> not being supported. So when problems occur the best option is still
>> to upgrade to the very latest release before debugging further - today
>> that would be squid-4.0.22 beta.
>>> Which is the best solution in order to setup a TRANSPARENT proxy
>>> service in a heterogeneous scenario with diferenbt types of devices,
>>> and running in the best mode with the minimum number of problems???
>> The _only_ solution is not to decrypt such traffic (the splice
>> action). How you determine which traffic is having such special trust
>> given to it is up to you. The TLS SNI is provided by the peek action
>> at SSL-Bump step 1.
> Well, you can do it when you want. For example, take a look (for example):
> https://stackoverflow.com/questions/4461360/how-to-install-trusted-ca-certificate-on-android-device
> or on this:
> http://wiki.cacert.org/FAQ/ImportRootCert
> Or, in your case,  you can differentiate users by, for example, by
> network and pass wifi users to splice rule. Much approaches exists.

NP: none of which work when the application is checking the fingerprint 
of the CA certificate against a hard-coded value defined by the vendor. 
These are simply ways to make the SSL-Bumping process work without 
"untrusted CA" warnings *if* bumping is already possible.

>>> Or do I have to move to a scenario with a defined proxy in another
>>> server, and automatically established in clients with DHCP ???
>> Explicit proxy is definitely better for HTTP than interception proxy.
>> That is true regardless of what else is going on. So worth doing *if*
>> you can.
> Oh, really? You have forgotten about beatiful 252 option in DHCP, about
> WCCP interception, and such other good things. In other world,

No, I am not.

DHCP, WPAD/PAC, and such are just ways to auto-configure explicit proxy 
*not* interception proxy.

WCCP is just a way to tunnel packets to the proxy machine. Explicit 
proxy does not require that additional tunnel complexity.
  If you combine WCCP with interception it becomes "interception proxy", 
not "explicit proxy".


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