February 2021 - stunnel-users

stunnel FIPS mode 140-2/ Other Modes
by mehmet ozisik 19 Sep '25

19 Sep '25

Hi All, I would like to ask a question about stunnel fips mode. There are lots of question and answers on the internet related with this, but I could not find any answer related with mine. I am compiling with openssl (auto detecting fips) . Here is a part of confgiure output : checking for FIPS_mode_set... yes configure: FIPS mode detected So I am thinking that fips also is being included. Then I try to run stunnel on target platform (in stunnel.conf fips=yes) and it gives below error : Compiled/running with OpenSSL 0.9.8w-fips 23 Apr 2012 Threading:PTHREAD Sockets:POLL,IPv6 SSL:ENGINE,OCSP,FIPS Reading configuration from file stunnel.conf FIPS_mode_set: 2D06906E: error:2D06906E:FIPS routines:FIPS_CHECK_INCORE_FINGERPRINT:fingerprint does not match there are lots of information about this errror on internet. Then when I configure stunnel.conf with fips=no, stunnel is running successfully. I know that fips=yes means that enables FIPS 140-2 mode and I guess my fips canister does not supoort fips 140-2 mode (I do not know which fips mode it has supported). Now my question is coming : When I set fips=no, stunnel also starts with other available fips modes which the canister included? Or it skips running fips mode completely? Plase inform me if anyone has any idea? Regards

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Requests to cloud server that requires host header
by Lorne Kates 13 Nov '24

13 Nov '24

(related to Akamai message from before-- but I have better troubleshooting information). I'm tying to route traffic through stunnel to a "cloud" based-endpoint. That endpoint has a static server name-- test.authorize.net. (This is the dev sandbox for auth.net) But if you do an nslookup on test.authorize.net, you'll get back a different servername and IP, because it's so wonderfully "cloud". Stunnel apparently tries to connect to the nslookup value. The server rejects the request because it can't route it back to test.authorize.net. I've tried adding "delay = yes" and "sni = test.authorize.net", but neither work. To see this in action, a simple setup with any accept, then connect to test.authorize.net:443 in client = yes mode. This is what a valid response looks like (13 -- give me the darn merchant ID in a POST): https://test.authorize.net/gateway/transact.dll This is what you'll get if you try to use stunnel (400 invalid url) : https://23.195.204.150/gateway/transact.dll So how can I get stunnel to send the proper Request Header (host: test.authorize.net) make sure it's using http/1.1, etc?

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Re: [stunnel-users] CPU 100%
by Eric Eberhard 06 Nov '24

06 Nov '24

Long ago I had a server with a bad network card. Every once in a while it would spew uncontrollable bytes onto the network. If you open a stunnel connection and it does that this could very well be the problem. If it cheap, try changing the network card. If not, you should be able to look in your firewall/router and it will tell you who is sending what bytes to whomever. See if that machine is indeed streaming the bytes in massive quantities. If not, I would suspect your stunnel is getting stuck in it's own loop. There are a million reasons this can happen (well a few less than a million) - such as maybe a bad library in the FreeBSD or a bad choice in the Makefile - such as doing threads or something in a way your O/S does not like (I use threads=fork or whatever it is, instead of actual threading). You might tinker with some of the options that make the stunnel build and try different ones. Especially if stunnel was compiled on a different version of the O/S - could be differences in bytes in things and who knows what. That is all I can suggest beyond setting the debug level to 7 (I think is highest) and then watching the log file. Eric From: stunnel-users [mailto:stunnel-users-bounces@stunnel.org] On Behalf Of Murrey, Brian J. Sent: Wednesday, October 17, 2018 10:57 AM To: stunnel-users(a)stunnel.org Subject: [stunnel-users] CPU 100% We are running stunnel 5.49 on FreeBSD 11.2 and we're running into a problem once in a while. CPU pegs at 100% when we get an stunnel connection from one of our external devices. This affects 100% of all cores and we can't even log in to console. To mitigate this temporarily, we have a script running in the background to watch when stunnel begins to spike and restarts the daemon. It doesn't happen 100% of the time, and so far I have been unable to distinguish what makes the connection do this to the CPU. Have any of you run in to this issue? Sincerely, Brian Murrey System Engineer II, IT Infrastructure _____ NOTICE: This message may contain privileged and confidential information and/or protected health information intended solely for the use of the named recipient and may be privileged or otherwise protected by law. If you are not the intended recipient of this message, you should immediately notify the sender and delete this message. Do not disseminate, reproduce, or review this message or attachments if you are not the intended recipient. The sender or others may have legal rights restricting the dissemination of the information contained in this message and, as a result, remedies against you in the event of the improper dissemination of confidential information, trade secrets, personal information or privileged communications. This message is the work of the sender and does not necessarily reflect the position, views, or policies of TriMedx LLC or its affiliates. WARNING: The integrity and security of this message cannot be guaranteed and may contain or transmit a virus or other illicit code. Neither TriMedx LLC or its affiliates accept liability for any damage attributable to viruses or illicit code transmitted through this message or an attachment.

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older browsers, stunnel and privoxy
by kovacs janos 04 Mar '24

04 Mar '24

sorry to bother, im trying to make older browsers be able to display TLS 1.1 and TLS 1.2 sites. i heard stunnel cant be configured to always forward to the current site address dynamically, thats why i would use privoxy. the browser is configured to send to: 127.0.0.1 443 stunnel config has this at the end: [Tunnel_in] client = yes accept = 127.0.0.1:443 connect = 127.0.0.1:8118 verifyChain = yes CAfile = ca-certs.pem checkHost = localhost 127.0.0.1:8118 is the privoxy address. this is what stunnel writes: LOG5[main]: Configuration successful LOG5[0]: Service [Tunnel_in] accepted connection from 127.0.0.1:3261 LOG5[0]: s_connect: connected 127.0.0.1:8118 LOG5[0]: Service [Tunnel_in] connected remote server from 127.0.0.1:3262 and the browser infinitely loads, and never loads anything or leaves the page. if i remove the last 3 lines, its the same just with this line added: LOG4[main]: Service [Tunnel_in] needs authentication to prevent MITM attacks but it doesnt give an error or anything. with a configuration like: [Tunnel_out] client = no accept = 127.0.0.1:443 connect = 127.0.0.1:8118 cert = stunnel.pem this is what it gives: LOG5[3]: Service [Tunnel_out] accepted connection from 127.0.0.1:3294 LOG3[3]: SSL_accept: 1407609B: error:1407609B:SSL routines:SSL23_GET_CLIENT_HELLO:https proxy request LOG5[3]: Connection reset: 0 byte(s) sent to TLS, 0 byte(s) sent to socket and browser gives a server not found error immediately. im not even sure if i should use client or server configuration in a case like this, but none of them works anyway. all i would need is for my browser to get the pages decrypted, or at least in less than TLS1.1. like how on newipnow.com i can access sites with any encryption, since they are sent to the browser without encryption. the browser just gives an "unencrypted tunnel" warning, which is how i found stunnel, and which is exactly what i need, just locally.

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TPM based mutual tls authentication
by Nyiri, Gabor (Nokia - HU/Budapest) 07 Nov '23

07 Nov '23

Hi, Can you help me how to configure stunnel client to use TPM for mutual TLS authentication? I want to connect with mTLS to a remote server then make this connection available for localhost without mTLS. Thanks for your help in advance! Here is my configuration so far without TPM: debug = debug output = /tmp/stunnel.log foreground = yes [mtls_client] client = yes accept = 127.0.0.1:12019 sni = server-with-mtls.example.com checkHost = server-with-mtls.example.com connect = 1.2.3.4:443 verifyChain = yes CApath = /etc/ssl/certs/ cert = client.crt key = client.key Thanks & br, Gábor Nyíri,

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New User
by David Rose (dsr) 24 Feb '21

24 Feb '21

Hi I have a Windows app that sends email via SMTP without any authentication (port can be set). I want to use it with Office365 SMTP service which requires TLS. Will stunnel allow me to do this without affecting any other application sending email ? If it does, what terms should I be looking for in the help info ? Many thanks Regards David --

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Windows Server 2012 R2 - localhost:25 stops listening
by Frank Warnke 23 Feb '21

23 Feb '21

Hi, I have noticed that when I install stunnel (stunnel-5.57-win64-installer.exe or today stunnel-5.58-win64-installer.exe) that running "netstat -ano" comes back with; TCP 127.0.0.1:25 0.0.0.0:0 LISTENING 2700 and the application we are using can send email via Gmail SMTP using the default stunnel.config. When I log out the user and go back in, the application can no longer send email via Gmail SMTP and "netstat -ano" no longer sees anything listening on port 25. I have verified that the stunnel service is running and have even stopped and started the stunnel service, but I am not able to get port 25 to be listened to unless I uninstall and install stunnel over again. It seems like something is setup or started during the stunnel install process that stops or gets killed after a user log outs. Any suggestions would be appreciated. Thanks, Frank

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Unable to connect to server using Stunnel with TLS1.2
by jing_pan＠kindermorgan.com 02 Feb '21

02 Feb '21

We failed to using stunnel to connect to remote server which only accept TLS1.2. So we configured the stunnel on our side with below stunnel.conf. We have another program listening to localhost:3500 and process the response from server. I would appreciate any suggestion. 1. Stunnel version: 2021.02.02 10:35:27 LOG5[main]: stunnel 5.58 on x64-pc-mingw32-gnu platform 2021.02.02 10:35:27 LOG5[main]: Compiled/running with OpenSSL 1.1.1h 22 Sep 2020 2021.02.02 10:35:27 LOG5[main]: Threading:WIN32 Sockets:SELECT,IPv6 TLS:ENGINE,OCSP,PSK,SNI 2021.02.02 10:35:27 LOG5[main]: Reading configuration from file stunnel.conf 2021.02.02 10:35:27 LOG5[main]: UTF-8 byte order mark not detected 2021.02.02 10:35:27 LOG4[main]: Service [FIXSERVER] needs authentication to prevent MITM attacks 2021.02.02 10:35:27 LOG5[main]: Configuration successful 2. stunnel.conf [FIXSERVER] cert = stunnel.pem client = yes fips = no accept = 127.0.0.1:3000 connect = 63.247.***.***:443 sslVersion = TLSv1.2 3. error returned: An existing connection was forcibly closed by the remote host 4. openssl s_client -connect 63.247.***.***:443 --- No client certificate CA names sent Peer signing digest: SHA256 Peer signature type: RSA Server Temp Key: ECDH, P-256, 256 bits --- SSL handshake has read 2814 bytes and written 419 bytes Verification error: self signed certificate in certificate chain --- New, TLSv1.2, Cipher is ECDHE-RSA-AES256-GCM-SHA384 Server public key is 2048 bit Secure Renegotiation IS supported Compression: NONE

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