[squid-users] squid mitm

[Amos Jeffries]

On 19/11/20 4:48 am, Niels Hofmans wrote:
> Hi guys,
> 
> I am trying to setup squid with TLS intercaption on Docker in an alpine 
> linux image.
> 
> My configuration is as follows:
> 
> access_log /dev/stdout
> 

Not a great idea. stdout is process specific ... and Squid is a 
collection of multiple processes that can change over time.

You can use TCP logging if you need to stream the data out of the 
container. see <https://wiki.squid-cache.org/Features/LogModules> for 
details.


> https_port 0.0.0.0:3128 \
>    intercept \
>    ssl-bump \
>    cert=/ca.pem \
>    generate-host-certificates=on \
>    dynamic_cert_mem_cache_size=500MB
> 
> sslcrtd_program /usr/lib/squid/security_file_certgen -s /cache/ssl.db -M 100MB
> sslcrtd_children 5
> 
> ssl_bump server-first all
> sslproxy_cert_error allow all
> 

These indicate that you are using a Squid-3.4 or older. Please upgrade 
to at least Squid-4. Ideally Squid-5 (beta) or even Squid-6 (alpha) for 
best TLS behaviour.


> 
> And the Dockerfile:
> 
> FROM alpine
> 
> RUN apk add -U --no-cache squid
> COPY cmd/config/ca.pem cmd/config/squid.conf /
> RUN mkdir -p /cache \
> && /usr/lib/squid/security_file_certgen -c -s /cache/ssl.db -M 100MB
> 
> EXPOSE 3128
> ENTRYPOINT ["/usr/sbin/squid”, “-f”, "/squid.conf”]
> 
> 
> However, this always exits with following error:
> 
> proxy_1       | [00] 2020/11/18 15:38:27| WARNING: BCP 177 violation. 
> Detected non-functional IPv6 loopback.
> proxy_1       | [00] 2020/11/18 15:38:27| FATAL: No valid signing 
> certificate configured for HTTPS_port 0.0.0.0:3128
> proxy_1       | [00] 2020/11/18 15:38:27| Squid Cache (Version 4.13): 
> Terminated abnormally.
> proxy_1       | [00] CPU Usage: 0.036 seconds = 0.021 user + 0.014 sys
> proxy_1       | [00] Maximum Resident Size: 42256 KB
> proxy_1       | [00] Page faults with physical i/o: 0
> 
> 
> And cmd/config <http://config.ca>/ca.pem was created with the command 
> from the wiki on macOS: openssl req -new -newkey rsa:1024 -days 365 
> -nodes -x509 -keyout ca.pem -out ca.pem
> Any ideas? Thanks!
> 

That command generates a regular server certificate. SSL-Bump needs a CA 
certificate.

Here are the correct command(s) for generating a root CA certificate for 
Squid and DER file for client install:
 
<https://wiki.squid-cache.org/ConfigExamples/Intercept/SslBumpExplicit#Usage>

Note: most of the rest of that page can be used as instructions for your 
setup. The only notable difference is the http(s)_port line settings, 
your current one is correct for an MITM proxy.


Amos