#StackBounty: #windows #tcp #connection #stunnel Unable to create seemingly simple stunnel configuration

Bounty: 100

I have a computer at work that is behind a firewall with an internal ip address of 192.168.12.13… the firewall maps ports 40000 – 40019 to matching ports on this local machine. (e.g. 40000 – 40000, 40001 – 40001, etc…) And, let’s define the external ip as 12.34.56.78.

I want to setup my home computer to connect to this work computer.

Work computer stunnel.config:

[brianserver]
client = no
accept = 127.0.0.1:40020
connect = 192.168.12.13:40000
PSKsecrets = psk1.txt

Home computer stunnel.config:

[brianclient]
client = yes
accept = 127.0.0.1:40020
connect = 12.34.56.78:40000
PSKsecrets = psk1.txt

I am using a product called “Hercules SETUP utility” to listen on the work machine:

enter image description here

And, I am using “Hercules SETUP utility” to initiate a connection from the home machine:

enter image description here

As you can see I am getting a connection refused message.

Home computer stunnel.log: (these messages occurred during connection attempt)

2019.04.10 23:36:09 LOG7[main]: Found 1 ready file descriptor(s)
2019.04.10 23:36:09 LOG7[main]: FD=616 ifds=r-x ofds = ---
2019.04.10 23:36:09 LOG7[main]: FD=624 ifds=r-x ofds = ---
2019.04.10 23:36:09 LOG7[main]: Service[brianclient] accepted(FD= 768) from 127.0.0.1:56795
2019.04.10 23:36:09 LOG7[main]: Creating a new thread
2019.04.10 23:36:09 LOG7[main]: New thread created
2019.04.10 23:36:09 LOG7[2]: Service[brianclient] started
2019.04.10 23:36:09 LOG7[2]: Setting local socket options(FD= 768)
2019.04.10 23:36:09 LOG7[2]: Option TCP_NODELAY set on local socket
2019.04.10 23:36:09 LOG5[2]: Service[brianclient] accepted connection from 127.0.0.1:56795
2019.04.10 23:36:09 LOG6[2]: s_connect: connecting 12.34.56.78:40000
2019.04.10 23:36:09 LOG7[2]: s_connect: s_poll_wait 12.34.56.78:40000: waiting 10 seconds
2019.04.10 23:36:10 LOG3[2]: s_connect: connect 12.34.56.78:40000: Connection refused(WSAECONNREFUSED) (10061)
2019.04.10 23:36:10 LOG3[2]: No more addresses to connect
2019.04.10 23:36:10 LOG5[2]: Connection reset: 0 byte (s) sent to TLS, 0 byte (s) sent to socket
2019.04.10 23:36:10 LOG7[2]: Local descriptor(FD= 768) closed
2019.04.10 23:36:10 LOG7[2]: Service[brianclient] finished(0 left)

Work computer stunnel.log: (ran at startup… no messages on connection attempt)

2019.04.10 21:24:55 LOG7[main]: Running on Windows 6.2
2019.04.10 21:24:55 LOG7[main]: No limit detected for the number of clients
2019.04.10 21:24:55 LOG5[main]: stunnel 5.51 on x64-pc-mingw32-gnu platform
2019.04.10 21:24:55 LOG5[main]: Compiled/running with OpenSSL 1.1.1b  26 Feb 2019
2019.04.10 21:24:55 LOG5[main]: Threading:WIN32 Sockets:SELECT,IPv6 TLS:ENGINE,OCSP,PSK,SNI
2019.04.10 21:24:55 LOG7[main]: errno: (* _errno())
2019.04.10 21:24:55 LOG7[service]: GUI message loop initialized
2019.04.10 21:24:55 LOG7[main]: Running on Windows 6.2
2019.04.10 21:24:55 LOG5[main]: Reading configuration from file stunnel.conf
2019.04.10 21:24:55 LOG5[main]: UTF-8 byte order mark detected
2019.04.10 21:24:55 LOG7[main]: Compression disabled
2019.04.10 21:24:55 LOG7[main]: No PRNG seeding was required
2019.04.10 21:24:55 LOG6[main]: Initializing service[brianserver]
2019.04.10 21:24:55 LOG6[main]: PSK identities: 1 retrieved
2019.04.10 21:24:55 LOG7[main]: Ciphers: HIGH:!aNULL:!SSLv2:!DH:!kDHEPSK
2019.04.10 21:24:55 LOG7[main]: TLSv1.3 ciphersuites: TLS_CHACHA20_POLY1305_SHA256:TLS_AES_256_GCM_SHA384:TLS_AES_128_GCM_SHA256
2019.04.10 21:24:55 LOG7[main]: TLS options: 0x02100004 (+0x00000000, -0x00000000)
2019.04.10 21:24:55 LOG7[main]: No certificate or private key specified
2019.04.10 21:24:55 LOG6[main]: DH initialization not needed
2019.04.10 21:24:55 LOG7[main]: ECDH initialization
2019.04.10 21:24:55 LOG7[main]: ECDH initialized with curves X25519:P-256:X448:P-521:P-384
2019.04.10 21:24:55 LOG5[main]: Configuration successful
2019.04.10 21:24:55 LOG7[main]: Binding service[brianserver]
2019.04.10 21:24:55 LOG7[main]: Listening file descriptor created(FD= 716)
2019.04.10 21:24:55 LOG7[main]: Setting accept socket options(FD= 716)
2019.04.10 21:24:55 LOG7[main]: Option SO_EXCLUSIVEADDRUSE set on accept socket
2019.04.10 21:24:55 LOG6[main]: Service[brianserver] (FD=716) bound to 127.0.0.1:40020
2019.04.10 21:24:55 LOG7[cron]: Cron thread initialized
2019.04.10 21:25:55 LOG6[cron]: Executing cron jobs
2019.04.10 21:25:55 LOG6[cron]: Cron jobs completed in 0 seconds
2019.04.10 21:25:55 LOG7[cron]: Waiting 86400 seconds

Also, psk1.txt has matching content:

brianskey:a3...6r

Also, on work computer:

C:Program Files (x86)stunnelbin>netstat -ano|findstr 40020
   TCP    0.0.0.0:40020          0.0.0.0:0              LISTENING       71888
   TCP    127.0.0.1:40020        0.0.0.0:0              LISTENING       34728

Note: the line with “0.0.0.0:40020” shows up after I start the Hercules listener.


Get this bounty!!!

Leave a Reply

This site uses Akismet to reduce spam. Learn how your comment data is processed.