May 2025 - 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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Is TLS 1.2 supported with stunnel 5.01
by joverton＠vital-soft.com 02 Jun '25

02 Jun '25

I have searched online, but was unable to fine any definitive answer on the minimum version of stunnel required for TLS 1.2. I have a client using stunnel 5.01 with our solution and they want to activate TLS 1.2. Their setup looks like this: 2014.05.15 13:38:22 LOG5[10132]: stunnel 5.01 on x86-pc-msvc-1500 platform 2014.05.15 13:38:22 LOG5[10132]: Compiled/running with OpenSSL 1.0.1g-fips 7 Apr 2014 2014.05.15 13:38:22 LOG5[10132]: Threading:WIN32 Sockets:SELECT,IPv6 SSL:ENGINE,OCSP,FIPS 2014.05.15 13:38:22 LOG5[10132]: Reading configuration from file stunnel.conf 2014.05.15 13:38:22 LOG5[10132]: FIPS mode disabled 2014.05.15 13:38:22 LOG5[10132]: Configuration successful Everything works fine without requiring TLS 1.2, but when that is required, we get the following error: 2025.05.14 07:04:45 LOG7[3796]: SSL state (connect): before/connect initialization 2025.05.14 07:04:45 LOG7[3796]: SSL state (connect): SSLv3 write client hello A 2025.05.14 07:04:45 LOG7[3796]: SSL alert (read): fatal: protocol version 2025.05.14 07:04:45 LOG3[3796]: SSL_connect: 1409442E: error:1409442E:SSL routines:SSL3_READ_BYTES:tlsv1 alert protocol version 2025.05.14 07:04:45 LOG5[3796]: Connection reset: 0 byte(s) sent to SSL, 0 byte(s) sent to socket 2025.05.14 07:04:45 LOG7[3796]: Remote socket (FD=840) closed 2025.05.14 07:04:45 LOG7[3796]: Local socket (FD=832) closed - Do we need to change anything in stunnel.conf? - Do we need to upgrade stunnel? Many Thanks, John

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Re: stunnel 5.75 released
by Christian Ullrich 28 May '25

28 May '25

* Michal Trojnara wrote: > I have released version 5.75 of stunnel. > > ### Version 5.75, 2025.05.26, urgency: MEDIUM Hello, why does the Windows release include "libgcc_s_seh-1.dll"? I cannot find anything that uses it, and a basic configuration works without any attempts to load it. I went to some lengths to find indications it might be loaded dynamically, but found nothing. Thanks, -- Christian

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stunnel 5.75 released
by Michał Trojnara 27 May '25

27 May '25

Dear Users, I have released version 5.75 of stunnel. ### Version 5.75, 2025.05.26, urgency: MEDIUM * Security bugfixes - OpenSSL DLLs updated to version 3.4.1. - OpenSSL FIPS Provider updated to version 3.1.2. * Bugfixes - Fixed infinite loop triggered by OCSP URL parsing errors (thx to Richard Könning for reporting). - Fixed OPENSSL_NO_OCSP build issues (thx to Dmitry Mostovoy for reporting). - Fixed default curve selection in FIPS mode with OpenSSL 3.4+. - Fixed tests with modern Python versions. - Fixed tests with multiple OpenSSL versions installed. * Features - Added provider URI support for "cert" and "key" options. - Added new "CAstore" service-level option (OpenSSL 3.0+). - Added "provider" (OpenSSL 3.0+), "providerParameter" (OpenSSL 3.5+), and "setEnv" global options. - Key file/URI path added to passphrase prompt on Unix. - PKCS#11 provider installed on Windows. Home page: https://www.stunnel.org/ Download: https://www.stunnel.org/downloads.html SHA-256 hashes: 0c1ef0ed85240974dccb94fe74fb92d6383474c7c0d10e8796d1f781a3ba5683 stunnel-5.75.tar.gz 18ec3b83bda9143c79479ecdc1e3ecf515eeb8a8b11e6ea3a6856cd77399317d stunnel-5.75-win64-installer.exe d1a04ec51840d8cbf5fb6d897d2eb999af573b5b66268fdec109cddaff2acfb7 stunnel-5.75-android.zip Best regards, Mike

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Preserving Client IP Address
by atritium＠hushmail.com 22 May '25

22 May '25

Has anyone followed the stunnel man page instructions and been able to successfully pass/preserve the connecting client's original IP address? Checking history on this issue back to 2010, it looks people with problems, no reports of success. Though it seems so fundamental, you would hope it was smooth as the man page indicates For example, I set up an iptables 'mangle' table for DIVERT routing, ip rule, ip route, etc, for the server as given in the stunnel man page for a Red Hat 8 system. When the stunnel server is then also configured with "transparent = source" and restarted, the remote-initiated connection -hangs- without connecting for a few seconds before closing. Take out "transparent = source" from the server config, and the connection works successfully (though the client IP address is not available to applications). Logs are the same up until the point (shown below), which shows the "hanging/failed" case timing out after reporting "Cannot assign an AF=2 address an AF=10 socket". Don't know what the "Cannot assign AF ..." refers to, or how to address it, but the process goes downhill and hangs after that. 7111 is the open port stunnel is monitoring. 2025.05.21 10:07:16 LOG7[0]: Cannot assign an AF=2 address an AF=10 socket 2025.05.21 10:07:16 LOG6[0]: IP_TRANSPARENT socket option set 2025.05.21 10:07:16 LOG6[0]: bind succeeded on the original port 2025.05.21 10:07:16 LOG6[0]: s_connect: connecting 127.0.0.1:7111 2025.05.21 10:07:16 LOG7[0]: s_connect: s_poll_wait 127.0.0.1:7111: waiting 10 seconds 2025.05.21 10:07:16 LOG7[0]: FD=6 events=0x2001 revents=0x0 2025.05.21 10:07:16 LOG7[0]: FD=11 events=0x2005 revents=0x1 2025.05.21 10:07:26 LOG3[0]: s_connect: s_poll_wait 127.0.0.1:7111: TIMEOUTconnect exceeded 2025.05.21 10:07:26 LOG3[0]: No more addresses to connect 2025.05.21 10:07:26 LOG5[0]: Connection reset: 0 byte(s) sent to TLS, 0 byte(s) sent to socket 2025.05.21 10:07:26 LOG7[0]: local_rfd/local_wfd reset (FD=3) 2025.05.21 10:07:26 LOG7[0]: Local descriptor (FD=3) closed 2025.05.21 10:07:26 LOG7[0]: Service [TLS SERVER] finished (0 left) The log for the successful case when "transparent = source is NOT specified in server config) instead says: 2025.05.21 09:59:58 LOG6[0]: s_connect: connecting ::1:7111 2025.05.21 09:59:58 LOG7[0]: s_connect: s_poll_wait ::1:7111: waiting 10 seconds 2025.05.21 09:59:58 LOG7[0]: FD=6 events=0x2001 revents=0x0 2025.05.21 09:59:58 LOG7[0]: FD=11 events=0x2005 revents=0x1 2025.05.21 09:59:58 LOG5[0]: s_connect: connected ::1:7111 2025.05.21 09:59:58 LOG6[0]: persistence: ::1:7111 cached 2025.05.21 09:59:58 LOG5[0]: Service [TLS SERVER] connected remote server from ::1:49806 2025.05.21 09:59:58 LOG7[0]: Setting remote socket options (FD=11) Any insight on what "Cannot assign an AF=2 address an AF=10 socket" is and how to fix it to preserve client IP address? stunnel is running as root, setuid is not used. I might not correctly understand the man page comment "This option is currently available in: Remote mode (connect option) on Linux >=2.6.28", but think it means a normal external connection request. Hopefully not a special configuration on the client side.

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SSL_CTX_load_verify_locations: Peer suddenly disconnected
by lynn9a＠yahoo.com 13 May '25

13 May '25

Hi, All When we try to start stunnel(stunnel 5.67, wolfSSL5.6.4 on linux), there is an error randomly happened like following, anybody knows why this happen and how to fix this? Thanks May 9 09:09:01 [ ] Initializing inetd mode configuration May 9 09:09:01 [ ] Clients allowed=500 May 9 09:09:01 [.] stunnel 5.67 on arm-oe-linux-gnueabi platform May 9 09:09:01 [.] Compiled/running with wolfSSL 5.6.4 May 9 09:09:01 [.] Threading:PTHREAD Sockets:POLL,IPv6,SYSTEMD TLS:OCSP,PSK,SNI May 9 09:09:01 [ ] errno: (*__errno_location ()) May 9 09:09:01 [ ] Initializing inetd mode configuration May 9 09:09:01 [.] Reading configuration from file /opt/config/stunnel.conf May 9 09:09:01 [.] UTF-8 byte order mark not detected May 9 09:09:01 [ ] No PRNG seeding was required May 9 09:09:01 [ ] Initializing service [xxxHost] May 9 09:09:01 [ ] stunnel default security level set: 2 May 9 09:09:01 [ ] Ciphers: TLS_AES_256_GCM_SHA384 May 9 09:09:01 [ ] TLSv1.3 ciphersuites: TLS_AES_256_GCM_SHA384:TLS_AES_128_GCM_SHA256:TLS_CHACHA20_POLY1305_SHA256 May 9 09:09:01 [ ] TLS options: 0x4D474C4C003000 (+0x0, -0x0) May 9 09:09:01 [ ] Session resumption enabled May 9 09:09:01 [ ] Loading certificate from file: ./config/client.pem May 9 09:09:01 [ ] Certificate loaded from file: ./config/client.pem May 9 09:09:01 [ ] Loading private key from file: ./config/client.key May 9 09:09:01 [:] Insecure file permissions on ./config/client.key May 9 09:09:01 [ ] Private key loaded from file: ./config/client.key May 9 09:09:01 [ ] Private key check succeeded May 9 09:09:01 [!] SSL_CTX_load_verify_locations: Peer suddenly disconnected May 9 09:09:01 [!] Service [xxxHost]: Failed to initialize TLS context May 9 09:09:01 [!] Configuration failed May 9 09:09:01 [ ] Deallocating temporary section defaults May 9 09:09:01 [ ] Deallocating section [xxxHost]

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