- stunnel-users - stunnel.org

Academic doubt about firewall bypass
by Brent Kimberley 09 Jul '19

09 Jul '19

Which scenario did you have in mind? [HTTP CLIENT] -->[STUNNEL CLIENT]--><whatever>-->[STUNNEL SERVER]-->[HTTP Server] OR[HTTP Client] -->[Forward-proxy client]-> [STUNNEL CLIENT]--> <whatever>-->[STUNNEL SERVER]-->[REVERSE-PROXY server]--><whatever>--> [HTTP SERVER ] From: Hugo Marello <hugo.marello(a)gmail.com> To: stunnel-users(a)stunnel.org Hello guys, I'm new to using stunnel but I find it quite a powerful tool. I'm doing a POC on how we can bypass our firewall even with DPI, and chose to use stunnel for an extra layer of cryptography. You don't have to worry about access to any VM mentioned here. Here is my scenario: [CLIENT BROWSER] -->[STUNNEL CLIENT]-->[FIREWALL]-->[STUNNEL SERVER]-->[REVERSE PROXY]-->[FREE INTERNET] So far I succeeded in getting HTTP working using stunnel CONNECT protocol to the firewall and going all the way through. The problem is when I try to access HTTPS, the connection get set to the stunnel server but it keeps waiting for something. Double checked all the logs, firewall can't discern, stunnel server get the connection, reverse proxy also get the socket connection. My hypothesis is that stunnel client gets the CONNECT from the browser and discard it, it uses its own way to connect to the firewall, instead of encrypting the CONNECT all the way through. As it may seems, I need a way to send 2 CONNECT packages. Does anyone know how can I proceed? Follow my configs: client = yes output = /var/log/stunnel4/stunnel.log debug = 7 [bypassclient] accept = 4000 connect = firewall.example:3128 protocolHost = destination.com:443 protocol = connect requireCert = no verifyChain = no verifyPeer = no -------------------------------------------------------------------------------------------------------------------- [bypassserver] accept = 0.0.0.0:443 connect = reverseproxy.com:8888 cert = /etc/ssl/cert.pem key = /etc/ssl/key.pem ----------------------------------------------------------------------------------------------------------------------- Thank you all in advance, already digging throw the source code (quite lost tough), Hugo

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Re: [stunnel-users] stunnel-users Digest, Vol 180, Issue 1
by Hugo Marello 09 Jul '19

09 Jul '19

I was thinking something more simple like the first scenario. [HTTP?CLIENT] -->[STUNNEL CLIENT]--><whatever>-->[STUNNEL SERVER]-->[HTTP Server] But the end would be an HTTPS server, which would require a CONNECT to get things going. So: [HTTP Client] -->[STUNNEL CLIENT]--> <whatever>-->[STUNNEL SERVER]-->[REVERSE-PROXY server]--> [HTTPS SERVER] Em ter, 9 de jul de 2019 às 07:00, <stunnel-users-request(a)stunnel.org> escreveu: > Send stunnel-users mailing list submissions to > stunnel-users(a)stunnel.org > > To subscribe or unsubscribe via the World Wide Web, visit > https://www.stunnel.org/cgi-bin/mailman/listinfo/stunnel-users > or, via email, send a message with subject or body 'help' to > stunnel-users-request(a)stunnel.org > > You can reach the person managing the list at > stunnel-users-owner(a)stunnel.org > > When replying, please edit your Subject line so it is more specific > than "Re: Contents of stunnel-users digest..." > > > Today's Topics: > > 1. Academic doubt about firewall bypass (Brent Kimberley) > 2. How to turn off logging (David Yunker) > 3. Re: How to turn off logging (Thomas Eifert) > > > ---------------------------------------------------------------------- > > Message: 1 > Date: Mon, 8 Jul 2019 16:42:39 +0000 (UTC) > From: Brent Kimberley <brent_kimberley(a)rogers.com> > To: <stunnel-users(a)stunnel.org> > Cc: "hugo.marello(a)gmail.com" <hugo.marello(a)gmail.com> > Subject: [stunnel-users] Academic doubt about firewall bypass > Message-ID: <182803560.2815516.1562604159801(a)mail.yahoo.com> > Content-Type: text/plain; charset="utf-8" > > Which scenario did you have in mind? > [HTTP?CLIENT] -->[STUNNEL CLIENT]--><whatever>-->[STUNNEL SERVER]-->[HTTP > Server]?OR[HTTP Client] -->[Forward-proxy client]->?[STUNNEL CLIENT]--> > <whatever>-->[STUNNEL SERVER]-->[REVERSE-PROXY server]--><whatever>--> > [HTTP SERVER ] > > > > From: Hugo Marello <hugo.marello(a)gmail.com> > To: stunnel-users(a)stunnel.org > > Hello guys, > I'm new to using stunnel but I find it quite a powerful tool. I'm doing a > POC on how we can bypass our firewall even with DPI, and chose to use > stunnel for an extra layer of cryptography. You don't have to worry about > access to any VM mentioned here. Here is my scenario: > > [CLIENT BROWSER] -->[STUNNEL CLIENT]-->[FIREWALL]-->[STUNNEL > SERVER]-->[REVERSE PROXY]-->[FREE INTERNET] > > So far I succeeded in getting HTTP working using stunnel CONNECT protocol > to the firewall and going all the way through. The problem is when I try to > access HTTPS, the connection get set to the stunnel server but it keeps > waiting for something. Double checked all the logs, firewall can't discern, > stunnel server get the connection, reverse proxy also get the socket > connection. My hypothesis is that stunnel client gets the CONNECT from the > browser and discard it, it uses its own way to connect to the firewall, > instead of encrypting the CONNECT all the way through. As it may seems, I > need a way to send 2 CONNECT packages. Does anyone know how can I proceed? > > Follow my configs: > client = yes > output = /var/log/stunnel4/stunnel.log > debug = 7 > > [bypassclient] > accept = 4000 > connect = firewall.example:3128 > protocolHost = destination.com:443 > protocol = connect > requireCert = no > verifyChain = no > verifyPeer = no > > -------------------------------------------------------------------------------------------------------------------- > [bypassserver] > accept = 0.0.0.0:443 > connect = reverseproxy.com:8888 > cert = /etc/ssl/cert.pem > key = /etc/ssl/key.pem > > ----------------------------------------------------------------------------------------------------------------------- > > > Thank you all in advance, already digging throw the source code (quite lost > tough), > Hugo >

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Re: [stunnel-users] Error during linking Stunnel 5.55
by Eric Eberhard 09 Jul '19

09 Jul '19

The whole 32 bit vs 64 bit thing is a pain. On Windows and Linux you have to load all kinds of unobvious things. On AIX it just works. Code from 1988 (when I lost source code for half a dozen programs) still works on current machines. Why the others make it SO HARD is beyond me. In AIX old code works. One flag – saying you want 64 bit – is all you need to add to the Makefile. Otherwise is just works as always. It took me MONTHS to figure out how to make Linuc work – had to yum 32 bit, 64 bit, a compat set, etc. Nightmare. Wish people would consider keeping things compatible like IBM does. Ditto on new features. Any new feature you merely need to add a flag, and all is good. Otherwise the old ones keep working. An example is POSIX. With IBM/AIX you could do things the old way, or set a flag for POSIX. Yes, we have had the same source (with updates, I did do the POSIX updates) since 1988. Never a problem. Partly, I think, because they don’t deprecate ANYTHING. Use the old routines if you like. Or not if you chose. Your problem is not having ALL of the required libraries! That is it. Finding what you need is the challenge. Eric From: stunnel-users [mailto:stunnel-users-bounces@stunnel.org] On Behalf Of Heinsbroek, Peter Sent: Tuesday, July 09, 2019 6:20 AM To: stunnel-users(a)stunnel.org Subject: [stunnel-users] Error during linking Stunnel 5.55 I tried to build stunnel from the sources. The compiling goes well ,but the linking gives an error When comping 32bit I get : sthreads.obj : error LNK2019: unresolved external symbol _CRYPTO_set_id_callback referenced in function _sthreads_init ..\bin\win32\stunnel.exe : fatal error LNK1120: 1 unresolved externals NMAKE : fatal error U1077: '"C:\Program Files (x86)\Microsoft Visual Studio\2017\Professional\VC\Tools\MSVC\14.16.27023\bin\HostX86\x86\link.EXE"' : return code '0x460' Stop. Anyone knows how to solve. Met vriendelijke groet, Peter Heinsbroek ICT Specialist – IDM TTS BTN/NL-TEC-Generic-Infra-S2 T: +31 (0) 88 265 9869 M: +31 (0) 6 53753244 Burg. Rijnderslaan 30 – Nederland <https://atos.net/> atos.net <https://www.linkedin.com/in/peter-heinsbroek-10467b52/> This e-mail and the documents attached are confidential and intended solely for the addressee; it may also be privileged. If you receive this e-mail in error, please notify the sender immediately and destroy it. As its integrity cannot be secured on the Internet, Atos’ liability cannot be triggered for the message content. Although the sender endeavours to maintain a computer virus-free network, the sender does not warrant that this transmission is virus-free and will not be liable for any damages resulting from any virus transmitted. On all offers and agreements under which Atos Nederland B.V. supplies goods and/or services of whatever nature, the Terms of Delivery from Atos Nederland B.V. exclusively apply. The Terms of Delivery shall be promptly submitted to you on your request.

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Re: [stunnel-users] How to turn off logging
by Eric Eberhard 09 Jul '19

09 Jul '19

Yes - just difficult :) We have our own logging in our application and we don't want stunnel's logging (or on screen error messages) to occur. We want them to go to our log files. So simply go to log.c and change the log_error() routines. I keep notes of any changes I make so that when I get new version I can repeat them. Eric From: stunnel-users [mailto:stunnel-users-bounces@stunnel.org] On Behalf Of David Yunker Sent: Monday, July 08, 2019 2:47 PM To: stunnel-users(a)stunnel.org Subject: [stunnel-users] How to turn off logging To whom it may concern, I would like to know if there is a way to disable logging or set a size limit or to have it overwrite the log file each time a new log is started? I am using the Windows version of Stunnel. Thank you for your help.

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Error during linking Stunnel 5.55
by Heinsbroek, Peter 09 Jul '19

09 Jul '19

I tried to build stunnel from the sources. The compiling goes well ,but the linking gives an error When comping 32bit I get : sthreads.obj : error LNK2019: unresolved external symbol _CRYPTO_set_id_callback referenced in function _sthreads_init ..\bin\win32\stunnel.exe : fatal error LNK1120: 1 unresolved externals NMAKE : fatal error U1077: '"C:\Program Files (x86)\Microsoft Visual Studio\2017\Professional\VC\Tools\MSVC\14.16.27023\bin\HostX86\x86\link.EXE"' : return code '0x460' Stop. Anyone knows how to solve. Met vriendelijke groet, [Atos logo] Peter Heinsbroek ICT Specialist – IDM TTS BTN/NL-TEC-Generic-Infra-S2 T: +31 (0) 88 265 9869 M: +31 (0) 6 53753244 Burg. Rijnderslaan 30 – Nederland atos.net<https://atos.net/> [LinkedIn icon]<https://www.linkedin.com/in/peter-heinsbroek-10467b52/> This e-mail and the documents attached are confidential and intended solely for the addressee; it may also be privileged. If you receive this e-mail in error, please notify the sender immediately and destroy it. As its integrity cannot be secured on the Internet, Atos’ liability cannot be triggered for the message content. Although the sender endeavours to maintain a computer virus-free network, the sender does not warrant that this transmission is virus-free and will not be liable for any damages resulting from any virus transmitted. On all offers and agreements under which Atos Nederland B.V. supplies goods and/or services of whatever nature, the Terms of Delivery from Atos Nederland B.V. exclusively apply. The Terms of Delivery shall be promptly submitted to you on your request.

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How to turn off logging
by David Yunker 08 Jul '19

08 Jul '19

To whom it may concern, I would like to know if there is a way to disable logging or set a size limit or to have it overwrite the log file each time a new log is started? I am using the Windows version of Stunnel. Thank you for your help.

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Academic doubt about firewall bypass
by Hugo Marello 28 Jun '19

28 Jun '19

Hello guys, I'm new to using stunnel but I find it quite a powerful tool. I'm doing a POC on how we can bypass our firewall even with DPI, and chose to use stunnel for an extra layer of cryptography. You don't have to worry about access to any VM mentioned here. Here is my scenario: [CLIENT BROWSER] -->[STUNNEL CLIENT]-->[FIREWALL]-->[STUNNEL SERVER]-->[REVERSE PROXY]-->[FREE INTERNET] So far I succeeded in getting HTTP working using stunnel CONNECT protocol to the firewall and going all the way through. The problem is when I try to access HTTPS, the connection get set to the stunnel server but it keeps waiting for something. Double checked all the logs, firewall can't discern, stunnel server get the connection, reverse proxy also get the socket connection. My hypothesis is that stunnel client gets the CONNECT from the browser and discard it, it uses its own way to connect to the firewall, instead of encrypting the CONNECT all the way through. As it may seems, I need a way to send 2 CONNECT packages. Does anyone know how can I proceed? Follow my configs: client = yes output = /var/log/stunnel4/stunnel.log debug = 7 [bypassclient] accept = 4000 connect = firewall.example:3128 protocolHost = destination.com:443 protocol = connect requireCert = no verifyChain = no verifyPeer = no -------------------------------------------------------------------------------------------------------------------- [bypassserver] accept = 0.0.0.0:443 connect = reverseproxy.com:8888 cert = /etc/ssl/cert.pem key = /etc/ssl/key.pem ----------------------------------------------------------------------------------------------------------------------- Thank you all in advance, already digging throw the source code (quite lost tough), Hugo

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SOLVED, I cannot get Outlook Express email to work after Cox changes
by Brent Kimberley 28 Jun '19

28 Jun '19

Thank you Brent, >> I found if I have Avast running with mail shield enabled I get this error in the Stunnel log window: >> SSL_connect: 140770FC: error:140770FC:SSL routines:SSL23_GET_SERVER_HELLO:unknown protocol >> Connection reset: 0 byte(s) sent to TLS, 0 byte(s) sent to socket. >> >> This results in no emails being abled to be sent by SMPT. >> >> If I disable Avast's mail shield the mail is sent with no errors. >> Is there a work around for to be able to use Stunnel without disabling Avast's mail shield? >> POP3 Connection >> CERT: Pre-verification error: self signed certificate in certificate chain >> Rejected by CERT at depth=1: OU=generated by Avast Antivirus for SSL/TLS scanning, O=Avast Web/Mail Shield, CN=Avast Web/Mail Shield Root >> SSL_connect: 14090086: error:14090086:SSL routines:ssl3_get_server_certificate:certificate verify failed If you need avast, sign your stunnel leaf with a well known root CA, and exchange certificates accordingly. cox_mail : avast_dpi : stunnel_TLS_proxy : client https://support.postbox-inc.com/hc/en-us/articles/204602300-Invalid-Securit…

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stunnel-users Digest, Vol 179, Issue 11
by David Yunker 28 Jun '19

28 Jun '19

Brent, Here is more log information that occurs when using Avast Mail shield. CERT: Pre-verification error: self signed certificate in certificate chain Rejected by CERT at depth=1: OU=generated by Avast Antivirus for SSL/TLS scanning, O=Avast Web/Mail Shield, CN=Avast Web/Mail Shield Root SSL_connect: 14090086: error:14090086:SSL routines:ssl3_get_server_certificate:certificate verify failed This occurs in the POP3 connection. Hope this helps.

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Re: [stunnel-users] stunnel-users Digest, Vol 179, Issue 11
by Brent Kimberley 28 Jun '19

28 Jun '19

>>Does anybody know how to prevent this from happening? Try adding the following: #verify the peer certificate chain starting from the root CA #pre-requisite #1: checkHost (OR checkIP) #pre-requisite #2: CAfile (OR CApath) verifyChain = yes checkHost = pop.cox.com #verify the peer certificate chain starting from the root CA #pre-requisite #1: checkHost (ORcheckIP) #pre-requisite #2: CAfile (OR CApath) verifyChain = yes checkHost = smtp.cox.net ref: https://www.stunnel.org/config_windows.html https://www.stunnel.org/static/stunnel.html From: David Yunker <davidyunker(a)hotmail.com> Subject: [stunnel-users] SOLVED, I cannot get Outlook Express email to work after Cox changes To anybody interested, Here is how to configure Stunnel for Outlook Express v6 in Windows XP to work: Modify Stunnel configuration to this: [cox-pop3] client = yes accept = 127.0.0.1:110 connect = pop.cox.net:995 CAfile = ca-certs.perm OCSPaia = yes [cox-smtp] client = yes accept = 127.0.0.1:25 connect = smtp.cox.net:587 CAfile = ca-certs.perm OCSPaia = yes Now configure Outlook Express as follows: Set incoming mail(POP3) to 127.0.0.1 Set outgoing mail(SMTP) to 127.0.0.1 Have "Logon using secure password authentication" unchecked. Have "My server requires authentication" unchecked For POP3 set incoming mail (POP3) to port 110. For SMTP set outgoing mail (SMTP) to port 25. Have "This server requires a secure connection(SSL)" for POP3 unchecked. Have "This server requires a secure connection(SSL)" for SMTP unchecked. Everything works except I have the following error message in the Stunnel log: "Service [service name] needs authentication to prevent MITM attacks" Does anybody know how to prevent this from happening? I tried having the "My server requires authentication" checked but I still have the message when Stunnel starts. Thank you for any help.

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