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Setup:

Raspberry Pi 3 with wlan0 interface acting as an Access Point (192.168.2.0/24) and eth0 (192.168.1.0/24) for default gateway to Internet. Pi has iptables Prerouting rules configured to forward web (port 80, 443) traffic to Burp Proxy running on my PC (on the eth0 subnet). I connect my Android phone (on version 9) to the Access Point (AP) and all web traffic is redirected to the Proxy. Certificates: I downloaded the Burp certificate and installed it in my Android phone (after changing the extension).

I can access HTTP traffic just fine. I am having certificate errors for HTTPS traffic. My browsers (Brave, Chrome, Firefox) are showing a Cert error NET::ERR_CERT_COMMON_NAME_INVALID. On investigating I found that the SAN (Subject Alt Name) should be set in self signed certificates to make browsers trust it. I saw various answers on Stackoverflow explaining how to generate such a certificate using OpenSSL. I generated one and imported it into Burp as well as my Android.

However, for HTTPS traffic I get the same error.

I tried using the Facebook app. Even the app is not able to load any data. On doing a packet capture I found that while the TLS negotiation is taking place, it gets a cert error which says (Alert: Fatal - Unknown CA).

wireshark error

What am I missing?

I am more interested in getting the facebook app trust this certificate and inspect the traffic on Burp. Please advise.

Maximilian Hils
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Pratik Lotia
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    So you want to fool the facebook app to trust your certificate so that you may do an MITM.. Many applications employ standard security practices where by they pin certificates or trust specific root CA's only in which case your self signed certificate will not work. – Soumen Mukherjee Sep 30 '19 at 05:31
  • @SoumenMukherjee Well, most professional environments have a firewall which decrypts, inspects & re-encrypts all traffic. Clearly the web version trusts such certificates - wonder if phone apps don't. I know a lot of company-provided phones do MITM as well. – Pratik Lotia Oct 07 '19 at 14:51

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