On 3/8/22 16:38, Aaron Dewell wrote:
Hi Alex, thanks for your reply! I did get access to the parent proxy
and my assumption was wrong, it's doing minimal bumping.
TLS inspection at the parent proxy does not affect what I was trying to
double check. What matters is whether it is a forward HTTP proxy (e.g.,
a Squid instance listening on an http_port configured without intercept,
tproxy, or accel flags). It sounds like that is what it is. That's OK!
I do not remember whether your Squid version (v4.13) supports SslBump
with parent forward proxies, but I believe modern Squids do, and we can
assume that your Squid version does as well. The debugging should show
whether that is indeed the case.
The parent is doing peek and splice to an exact list of internal
destinations. Specifically, peek step1 all, peek step2 allowed_sites,
splice allowed_sites, terminate all. That shouldn't (to my imperfect
knowledge) interfere with what I'm doing though.
Yes, assuming the parent does not terminate your Squid connections, of
course (i.e. assuming connections from your Squid always match
allowed_sites after step1 at the parent proxy).
That's a good idea to do splice only and see if that's successful.
Trying to do too much at once! I'll see what that does, then try debug
again. The debug output wasn't very helpful before, but stepwise may be
more useful.
Just to clarify: The debugging output was not meant for you to
interpret. A Squid developer should do that. It may contain sensitive
details; it is best to not use anything but test traffic and test
certificate keys when sharing ALL,9 output.
Alex.
On Mar 8 2022, at 1:43 pm, Alex Rousskov wrote:
On 3/8/22 14:16, Aaron Dewell wrote:
> I'm trying to use these two features at the same time. The use
case is
> pretty simple. I want to capture all traffic from a single source (a
> device of mine) to another squid proxy server and decrypt/log
it. I'm
> using the Ubuntu 20 package of squid-ssl version 4.13.
>
> Device -> ssl_bump proxy -> upstream proxy -> website
>
> It was all successfully working without ssl_bump, so the cache_peer
> configuration works. One side note: the parent proxy is running
on 443
> without SSL (I believe - I don't run it but I've asked those that
do for
> confirmation, but I do know it's a pretty standard destination proxy
> configuration).
>
> The website itself is not directly accessible thus the upstream
proxy is
> required.
>
> Adding the ssl_bump configuration caused it to not work, with errors
> about SSL versions and "Error negotiating SSL connection on FD
xx". My
> best guess is that it is attempting to establish an SSL connection to
> the upstream and failing.
>
> acl step1 at_step SslBump1
> ssl_bump peek step1
> ssl_bump bump all
> http_port 3128 ssl-bump cert=/var/lib/squid/ssl_cert/myCA.pem
> generate-host-certificates=on dynamic_cert_mem_cache_size=4MB
> tls_outgoing_options options=NO_SSLv3
> flags=DON'T_VERIFY_PEER,DONT_VERIFY_DOMAIN
> cert=/var/lib/squid/ssl_cert/device.pem
> key=/var/lib/squid/ssl_cert/client.key
>
> (client.key and client.pem are from the device and are needed due
to the
> authentication of the session at the destination server. Also, I
> haven't looked at the packet logging yet. I assume that will be
an easy
> addition once the setup works generally.)
>
> However, my understanding is that the cache_peer configuration should
> NOT do TLS by default unless that was specified in the options, and I
> see no way to explicitly disable it.
>
> So first question: is that assumption accurate? No TLS to the parent
> unless explicitly configured?
Yes, that is correct: cache_peers are plain HTTP forward proxies unless
explicitly configured otherwise. Their listening port value does carry
any special meaning as far as Squid code is concerned.
However, it is very unusual to run a plain HTTP forward proxy on port
443. That port may imply that your parent proxy is an HTTPS reverse
proxy. If it is, you need to use originserver flag when configuring the
corresponding cache_peer line. You can check by sending plain CONNECT
requests to that upstream proxy using wget, curl, or some such. A
reverse HTTPS proxy would reject such requests.
> if the ssl_bump configuration is causing it to attempt an upstream
> TLS connection ...
Bugs notwithstanding, it should not.
> Anything here that I'm doing obviously wrong?
I see no red flags relevant to your specific question.
Does replacing "bump all" with "splice all" fix the problem? I realize
that you do want to bump/see the device traffic, but I wonder whether
the errors are not between Squid and the upstream proxy but Squid and
the web site. Splicing would remove those errors while still keeping
some SslBump code active.
Sharing a (pointer to compressed) libpcap packet capture and/or a
(pointer to compressed) ALL,9 cache.log while reproducing the problem
with a single transaction may help:
https://wiki.squid-cache.org/SquidFaq/BugReporting#Debugging_a_single_transaction
Alex.
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