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Old 5th August 2015
e1-531g e1-531g is offline
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Join Date: Mar 2014
Posts: 597
Default TLS intercepting proxy [MitM]

I wonder is this possible:
I use Firefox to visit website https://domain
Firefox -> relayd 1-> privoxy -> relayd 2- -> Internet
1. relayd 1 decrypts https traffic then forwards this to privoxy
2. privoxy makes its job on http/html
3. privoxy forwards traffic to relayd 2
4. relayd 2 encrypts traffic

Privoxy is listening on 8118 tcp port
Relayd1 is listening on 445 tcp port

I want to note that domain is changing, sometimes it is google.com, sometimes mail.yahoo.com etc, and all configurations can not be preconfigured (so relayd 2 must forward traffic to destination on the basis of destination IP in IP packet or Host header in http protocol).

I have done configuration up to forwarding traffic to privoxy with rdr-to in pf. Privoxy receives IP packets with changed IP dst, but probably can send it further because of Host in http data. It can even send decrypted traffic to 80 port and I actually used that to talk to google.com:
firefox visits https://google.com -> relayd 1 -> privoxy -> (dst port changed, traffic decrypted) http://google.com:80

If there is another tool that can do it for me instead of relayd, please inform me.

My config:
match out on bge0 inet proto tcp to port 443 rdr-to lo0 port 445
match in  on lo0  inet proto tcp to port 445 nat-to lo0
relay sslaccelerator {
        listen on port 445 tls
        forward to port 8118
I wanted to make it further, but if relayd 2 receives packed redirected in pf, relayd 2 is trying to send packet to: unknownIP port 0. I have tried using diver-to, but I can not use divert-to in pass out rules.
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Old 29th November 2015
e1-531g e1-531g is offline
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Join Date: Mar 2014
Posts: 597

I have posted to misc mailing list Subject about this on 2015-11-23 called "TLS intercepting proxy [MitM]" and also asked a question on 2015-11-24 in Subject called "Re: pf change destination port for outgoing traffic". People were kind, they shared they knowledge and now I am able to do this MitM attack on myself to enhance my privacy. I don't have time now, to make sure everything is secure, so I don't use this config yet. I am going to do this in one month. Probably connect 2 PC in series/serial way to router using Ethernet over twisted-pair cable to sniff and try to find hypothetical leaks, bad ciphers etc.
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intercepting proxy, openbsd, ssl, tls

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