Re: [squid-users] HTTPS forward proxy?

Tue, 21 Jan 2014 13:29:38 -0800 

On 2014-01-22 09:25, David Deller wrote:

Hello,

I’m trying to set up Squid as an HTTPS forward proxy, but I’m having
trouble getting it to work.

Here's some background about my problem:

* I have a web service running on Heroku, with a dynamic IP address.
Static IPs on Heroku are not an option.
* I need to connect to an external web service which is behind a
firewall. The people who operate the external web service will only
open their firewall to a specific static IP.

My attempted solution is to use Squid on a separate server with a
static IP to forward-proxy requests from Heroku to the external
service. That way, the external service always sees the proxy server's
static IP, instead of the Heroku service's dynamic IP.

Since my proxy server can't rely on an IP address for authentication
You mean authorization, not authentication. A number (IP address) cannot own credentials, only an entity can have credentials and credentials are required for authentication. 


(that's the problem to begin with!), it must rely on a username and
password. Further, the username and password cannot be transmitted in
clear text,


Meaning: avoid Basic authentication type.


because if an attacker were to intercept that clear text,
then they could connect to my proxy pretending to be me, make outbound
requests using my proxy's static IP, and thus evade the external web
service's firewall.
Squid is not limited to the Basic authentication protocol. I see you are already using Digest authentication, which already does what you want even in unencrypted HTTP. 



Therefore, the Squid proxy must only accept connections over HTTPS,
not HTTP. (The connection to the external web service might be HTTP or
HTTPS.)
No. Given you already use Digest auth the SSL layer is not necessary to prevent that attack type. It is just an extra layer to obscure the content being transferred. I think it is a good idea to use it of possible, but am aware there are some big troubles (namely that modern browsers still do not support connecting to a proxy over SSL/TLS). 




I'm running Squid 3.1.10 on CentOS 6.5.x,
Please try an upgrade. You can find details about newer versions for CentOS at http://wiki.squid-cache.org/KnowledgeBase/CentOS 
<snip>
Using this setup, HTTP proxying works fine, but HTTPS proxying does not. 

Here's an HTTP proxy request from a local box:

    $ curl --proxy http://my-proxy-server.example:3128 \
      --proxy-anyauth --proxy-user redacted:redacted -w '\n' \
      http://urlecho.appspot.com/echo?body=OK
    OK


<snip>


Here's another request, this time with HTTPS:

    $ curl --proxy https://my-proxy-server.example:3129 \
      --proxy-anyauth --proxy-user redacted:redacted -w '\n' \
      http://urlecho.appspot.com/echo?body=OK

    curl: (56) Recv failure: Connection reset by peer

Nothing in `access.log` after this one, but in `cache.log`:

    2014/01/20 20:46:15| clientNegotiateSSL: Error negotiating SSL
connection on FD 10: error:1407609C:SSL
routines:SSL23_GET_CLIENT_HELLO:http request (1/-1)
See the serverfault response. curl is connecting to the proxy using plain-text instead of SSL. 


Here's the above again, more verbosely:

    $ curl -v --proxy https://my-proxy-server.example:3129 \
      --proxy-anyauth --proxy-user redacted:redacted -w '\n' \
      http://urlecho.appspot.com/echo?body=OK
    * Adding handle: conn: 0x7f9a30804000
    * Adding handle: send: 0
    * Adding handle: recv: 0
    * Curl_addHandleToPipeline: length: 1
    * - Conn 0 (0x7f9a30804000) send_pipe: 1, recv_pipe: 0
* About to connect() to proxy my-proxy-server.example port 3129 (#0) 
    *   Trying proxy.server.IP.redacted...
    * Connected to my-proxy-server.example (proxy.server.IP.redacted)
port 3129 (#0)


Note the absence of any mention about SSL/TLS here.


    > GET http://urlecho.appspot.com/echo?body=OK HTTP/1.1
    > User-Agent: curl/7.30.0
    > Host: urlecho.appspot.com
    > Accept: */*
    > Proxy-Connection: Keep-Alive
    >
    * Recv failure: Connection reset by peer
    * Closing connection 0

    curl: (56) Recv failure: Connection reset by peer

Looks like an SSL error.
It is. Try using --ssl option for curl. You will also need --proxy-digest to get the Digest auth against the proxy working for curl. 


However, I'm reusing a subdomain-wildcard SSL
certificate, shown in the above config as `cert.pem` and `key.pem`,
that I've successfully deployed on other web servers. Moreover,
accessing the proxy server directly with curl works, or at least
establishes a connection past the SSL stage:

    $ curl https://my-proxy-server.example:3129
    <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01//EN"
"http://www.w3.org/TR/html4/strict.dtd";>

    [--SNIP--]
This tells us that the test machine can access the web serve. Please run the same test directly on the squid machine. That will tell whether or not connectivity for Squid is working properly. 




Any ideas what I'm doing wrong? Is what I'm attempting even possible?
It is possible and being done already by some. Although to get the broken browsers to work properly a VPN/stunnel from the client machine to proxy port is often needed. 

Amos

Reply via email to