No problem. I am just trying to find something that helps to narrow down the 
problem. What I want to achieve is, that a client can use HTTP in the LAN, so 
that Squid can cache distribution packages without making use of SSL 
intercepting when repos are only accessible via HTTPS. In that case the secure 
connection must start at the proxy and end on the target server with or without 
any upstream proxies in betweem. When the proxy has received the payload, it 
can cache it and send it back to the client via plain HTTP. When a new request 
for this package arrives, the server can just return the resource from the 
cache.

We have the following setup:

client -> downstream proxy -> upstream proxy -> https://download.docker.com

Now let us assume the client wants to retrieve the following resource 
http://download.docker.com/linux/ubuntu/dists/jammy/InRelease from the upstream 
proxy.

The client initiates a HTTP GET request and sends it to the downstream proxy. 
Now, the URL gets rewritten. It indicates to use a HTTPS connection instead in 
order to talk to the target server, in our case the result is 
https://download.docker.com/linux/ubuntu/dists/jammy/InRelease. Now comes the 
critical point: From my understanding – it may be wrong of course - the 
downstream server now has to send a CONNECT request to the upstream server to 
advise him to establish a secure connection to the target server. After 
creation, the downstream proxy can retrieve the resource and send it back to 
the client via plain HTTP.

I suppose, that the GnuTLS occurs because of a missing SSL handshake between 
downstream proxy and download.docker.com.

Do I get something wrong?

Regards,
Christoph


>-----Ursprüngliche Nachricht-----
>Von: Alex Rousskov <rouss...@measurement-factory.com>
>Gesendet: Mittwoch, 10. Juli 2024 22:15
>An: squid-users@lists.squid-cache.org
>Cc: Fiehe, Christoph <c.fi...@eurodata.de>
>Betreff: AW: [squid-users] Rewriting HTTP to HTTPS for generic package proxy
>
>On 2024-07-10 15:31, Fiehe, Christoph wrote:
>> The problem is that the proxy just forwards the client GET request to the 
>> upstream proxy
>
>Why does sending a GET request to the upstream proxy represent a problem
>in your use case? I cannot find anything in your prior messages on this
>thread that would preclude sending a GET request to the upstream proxy.
>
>
>> but in that case a CONNECT is required.
>
>Why?
>
>Please do not interpret my response as implying that this "must send
>CONNECT" requirement is wrong (or correct). At this point, I am just
>trying to understand what problem(s) you are trying to solve beyond the
>one you have originally described.
>
>
>Thank you,
>
>Alex.

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