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Question on 5.77 found differences.
by Michael D. Setzer II 18 Feb '26

18 Feb '26

Did the configure and make and then make install, but it didn't work as it had on 5.76 since it was saying stunnel.conf was in wrong place?? Had always had in /etc/stunnel/stunnel.conf with both the fedora version and the 5.76 binary files in ls /usr/local/bin/stunnel* -l 796752 Feb 18 13:20 /usr/local/bin/stunnel 2793 Feb 18 13:20 /usr/local/bin/stunnel3 792448 Feb 18 13:19 /usr/local/bin/stunnel-5.76 For 5.77 had to copy stunnel.conf /usr/local/etc/stunnel/stunnel.conf Had just done ./configure make make install stunnel -version Initializing inetd mode configuration stunnel 5.77 on x86_64-pc-linux-gnu platform Compiled/running with OpenSSL 3.2.6 30 Sep 2025 Threading:PTHREAD Sockets:POLL,IPv6,SYSTEMD TLS:FIPS,OCSP,PSK,SNI Global options: fips = no RNDbytes = 1024 RNDfile = /dev/urandom RNDoverwrite = yes Service-level options: ciphers = FIPS:!DH:!kDHEPSK (with "fips = yes") ciphers = HIGH:!aNULL:!SSLv2:!DH:!kDHEPSK (with "fips = no") ciphersuites = TLS_AES_256_GCM_SHA384:TLS_AES_128_GCM_SHA256:TLS_C HACHA20_POLY1305_SHA256 (with TLSv1.3) curves = P-256:P-521:P-384 (with "fips = yes") curves = X25519:P-256:X448:P-521:P-384 (with "fips = no") debug = daemon.notice logId = sequential options = NO_SSLv2 options = NO_SSLv3 securityLevel = 2 sessionCacheSize = 1000 sessionCacheTimeout = 300 seconds stack = 131072 bytes TIMEOUTbusy = 300 seconds TIMEOUTclose = 60 seconds TIMEOUTconnect = 10 seconds TIMEOUTidle = 43200 seconds TIMEOUTocsp = 5 seconds verify = none Ports shows: # lsof -i | grep stunnel stunnel 171807 nobody 9u IPv4 388014 0t0 TCP localhost:20995 (LISTEN) stunnel 171807 nobody 10u IPv4 388015 0t0 TCP localhost:20465 (LISTEN) stunnel 171807 nobody 11u IPv4 388016 0t0 TCP localhost:20993 (LISTEN) stunnel 171807 nobody 12u IPv4 388017 0t0 TCP localhost:20996 (LISTEN) stunnel 171807 nobody 13u IPv4 388018 0t0 TCP localhost:20466 (LISTEN) stunnel 171807 nobody 14u IPv4 388019 0t0 TCP localhost:10995 (LISTEN) stunnel 171807 nobody 15u IPv4 388020 0t0 TCP localhost:10465 (LISTEN) So, all seems fine, but not clear on why location of stunnel.conf changed. Another thing tried to look at donate option and goes to this page https://business.revolut.com/revolutme/mobicompolska But shows. User not found Use for my personal setup with Pegasus Email to 3 ISPs, but was looking to give something. Thanks. Using Fedora 42 and 43 systems, but now using the stunnel.org setup instead of fedora's repos version. +------------------------------------------------------------+ Michael D. Setzer II - Computer Science Instructor (Retired) mailto:mikes@guam.net mailto:msetzerii@gmail.com mailto:msetzerii@gmx.com Guam - Where America's Day Begins G4L Disk Imaging Project maintainer http://sourceforge.net/projects/g4l/ +------------------------------------------------------------+

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stunnel 5.77 released
by Michał Trojnara 17 Feb '26

17 Feb '26

Dear Users, I have released version 5.77 of stunnel. ### Version 5.77, 2026.02.17, urgency: MEDIUM * Security bugfixes - OpenSSL DLLs updated to version 3.5.5. * Bugfixes - Avoid attempting to fetch OCSP stapling for PSK-only configuration sections. * Features - Merged applicable patches from Fedora and Debian: - Use SOURCE_DATE_EPOCH for reproducible builds. - Skip the OpenSSL version check when AUTOPKGTEST_TMP is set. - Enable PrivateTmp in the stunnel.service template. - Clarify the manual page for the "curves" option. - Log client IP addresses on TLS errors. Home page: https://www.stunnel.org/ Download: https://www.stunnel.org/downloads.html SHA-256 hashes: ec026f4fae4e0d25b940cc7a9451d925e359e7fd59e9edad20baea66ce45f263 stunnel-5.77.tar.gz 59ba0c5330de85ef474164b40cc559b2eb4e2b8d788c48b564e2257efa236384 stunnel-5.77-win64-installer.exe 718431a1d3c889806b61d6f082bbfaaa29529ce422d8115ad2211574dfb89ec1 stunnel-5.77-android.zip Best regards, Mike

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Question on trying to setup stunnel 5.76 on Fedora 42/43 system.
by Michael D. Setzer II 13 Feb '26

13 Feb '26

Run into some issues with trying to upgrade the stunnel to 5.76 version while Fedora repos version is still at 5.75. Found one thing that showed using this configurations options. ./configure \ --sysconfdir=/etc \ --localstatedir=/var \ --enable-systemd \ --with-ssl=/usr But using it, the stunnel 5.76 is still installing in /usr/local/bin? Also, finding the systemctl status stunnel is still showing the /usr/bin/stunnel 5.75 being run? Removed the fedora repo version, and then systemctl no longer shows a service for stunnel, but run it manually at boot, and it works fine. Seems the fedora version has a ENGINE option that the stunnel option doesn't. stunnel -version Initializing inetd mode configuration stunnel 5.76 on x86_64-pc-linux-gnu platform Compiled/running with OpenSSL 3.2.6 30 Sep 2025 Threading:PTHREAD Sockets:POLL,IPv6,SYSTEMD TLS:FIPS,OCSP,PSK,SNI Global options: fips = no RNDbytes = 1024 RNDfile = /dev/urandom RNDoverwrite = yes Service-level options: ciphers = FIPS:!DH:!kDHEPSK (with "fips = yes") ciphers = HIGH:!aNULL:!SSLv2:!DH:!kDHEPSK (with "fips = no") ciphersuites = TLS_AES_256_GCM_SHA384:TLS_AES_128_GCM_SHA256:TLS_C HACHA20_POLY1305_SHA256 (with TLSv1.3) curves = P-256:P-521:P-384 (with "fips = yes") curves = X25519:P-256:X448:P-521:P-384 (with "fips = no") debug = daemon.notice logId = sequential options = NO_SSLv2 options = NO_SSLv3 securityLevel = 2 sessionCacheSize = 1000 sessionCacheTimeout = 300 seconds stack = 131072 bytes TIMEOUTbusy = 300 seconds TIMEOUTclose = 60 seconds TIMEOUTconnect = 10 seconds TIMEOUTidle = 43200 seconds TIMEOUTocsp = 5 seconds verify = none Know that sometmes the fedora repo doesn't update each time, or it takes more time? Is there way to install the latest version and have the systemd setup to work. At present, have the Fedora repo version uninstalled, and run the stunnel in rc.local? Thanks. +------------------------------------------------------------+ Michael D. Setzer II - Computer Science Instructor (Retired) mailto:mikes@guam.net mailto:msetzerii@gmail.com mailto:msetzerii@gmx.com Guam - Where America's Day Begins G4L Disk Imaging Project maintainer http://sourceforge.net/projects/g4l/ +------------------------------------------------------------+

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Rare crashes of stunnel
by Don Lee 07 Feb '26

07 Feb '26

Hi guys, I have been running stunnel in production for my email server users. It’s been great. It’s pretty stable, and does all that I ned to allow my users to connect to my ancient mailserver (EIMS) with modern SSL. In fact, it’s been so stable that until recently I had no backup on stunnel It just ran. Unfortunately, I have had some incidents where stunnel just crashes. When it does, it looks like my email facilities are completely down - not good. I now have a script that monitors stunnel, and when stunnel dies, the script re-starts it. Below is a snippet of my stunnel log at the crash point. Does anyone else have this problem? Are the developers interested in my data? I installed it as a pre-built binary package, and this is the most recent version in the packages collection, so I am reluctant to build my own stunnel. Thank you for a great tool. -dgl- 2026.02.06 15:04:25 LOG5[75312]: Connection closed: 784 byte(s) sent to TLS, 224 byte(s) sent to socket 2026.02.06 15:04:25 LOG5[75311]: Connection closed: 2036 byte(s) sent to TLS, 22 9 byte(s) sent to socket 2026.02.06 15:04:25 LOG5[75313]: Service [imaps] accepted connection from 107.12 3.20.177:6908 2026.02.06 15:04:25 LOG5[75314]: Service [imaps] accepted connection from 107.12 3.20.177:9568 2026.02.06 15:04:25 LOG5[75313]: s_connect: connected 71.39.101.34:143 2026.02.06 15:04:25 LOG5[75313]: Service [imaps] connected remote server from 71 .39.101.39:49527 2026.02.06 15:04:25 LOG5[75314]: s_connect: connected 71.39.101.34:143 2026.02.06 15:04:25 LOG5[75314]: Service [imaps] connected remote server from 71 .39.101.39:49526 2026.02.06 15:04:28 LOG3[per-minute]: OCSP: OCSP_check_validity: /usr/src/crypto /external/bsd/openssl/dist/crypto/ocsp/ocsp_cl.c:378: error:2707307D:OCSP routin es:OCSP_check_validity:status expired 2026.02.06 15:04:28 LOG4[per-minute]: OCSP: Unknown verification status INTERNAL ERROR: Memory allocated in a different thread at ocsp.c, line 412 2026.02.06 15:04:41 LOG5[ui]: stunnel 5.73 on x86_64--netbsd platform 2026.02.06 15:04:41 LOG5[ui]: Compiled/running with OpenSSL 1.1.1t 7 Feb 2023 2026.02.06 15:04:41 LOG5[ui]: Threading:PTHREAD Sockets:POLL,IPv6 TLS:ENGINE,OCS P,PSK,SNI Auth:LIBWRAP 2026.02.06 15:04:41 LOG5[ui]: Reading configuration from file /usr/pkg/etc/stunn el/stunnel.conf 2026.02.06 15:04:41 LOG5[ui]: UTF-8 byte order mark detected 2026.02.06 15:04:41 LOG5[ui]: OCSP: Connecting the AIA responder "http://status. rapidssl.com"

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CoAP protocol support
by James Hanley 30 Jan '26

30 Jan '26

I’m not sure if this is the right forum but adding CoAP/CoAP support analogous to http/https but for both TCP/TLS & UDP/DTLS would be useful for testing. -Jim

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Re: stunnel : SSL_connect: Peer suddenly disconnected
by Jose Alf. 19 Dec '25

19 Dec '25

Hi Souheila, Are you sure that you are running an NFS server in your azure machine that natively supports TLS? If you are not, you must put an stunnel wrapper in front of it. It looks to me that the NFS service exposed at 52.239.241.136:2049 does not support TLS. 2025.12.19 07:53:48 LOG7[0]: Service [52.239.241.136] started 2025.12.19 07:53:48 LOG7[0]: Setting local socket options (FD=584) 2025.12.19 07:53:48 LOG7[0]: Option TCP_NODELAY set on local socket 2025.12.19 07:53:48 LOG5[0]: Service [52.239.241.136] accepted connection from 127.0.0.1:58887 2025.12.19 07:53:48 LOG6[0]: s_connect: connecting 52.239.241.136:2049 2025.12.19 07:53:48 LOG7[0]: s_connect: s_poll_wait 52.239.241.136:2049: waiting 10 seconds 2025.12.19 07:53:48 LOG7[0]: FD=1040 ifds=rwx ofds=--- 2025.12.19 07:53:49 LOG5[0]: s_connect: connected 52.239.241.136:2049 2025.12.19 07:53:49 LOG5[0]: Service [52.239.241.136] connected remote server from 192.168.1.26:58888 2025.12.19 07:53:49 LOG7[0]: Setting remote socket options (FD=1040) 2025.12.19 07:53:49 LOG7[0]: Option TCP_NODELAY set on remote socket 2025.12.19 07:53:49 LOG7[0]: Remote descriptor (FD=1040) initialized 2025.12.19 07:53:49 LOG6[0]: SNI: sending servername: 52.239.241.136 2025.12.19 07:53:49 LOG7[0]: No previous session to resume 2025.12.19 07:53:49 LOG6[0]: Peer certificate not required 2025.12.19 07:53:49 LOG7[0]: TLS state (connect): before SSL initialization 2025.12.19 07:53:49 LOG7[0]: TLS state (connect): SSLv3/TLS write client hello 2025.12.19 07:53:49 LOG7[0]: TLS alert (write): fatal: decode error 2025.12.19 07:53:49 LOG3[0]: SSL_connect: ssl/record/rec_layer_s3.c:696: error:0A000126:SSL routines::unexpected eof while reading 2025.12.19 07:53:49 LOG5[0]: Connection closed/reset: 0 byte(s) sent to TLS, 0 byte(s) sent to socket 2025.12.19 07:53:49 LOG7[0]: Remote descriptor (FD=1040) closed 2025.12.19 07:53:49 LOG7[0]: local_rfd/local_wfd reset (FD=584) 2025.12.19 07:53:49 LOG7[0]: Local descriptor (FD=584) closed 2025.12.19 07:53:49 LOG7[0]: Service [52.239.241.136] finished (0 left) Regards,Jose A. Diaz On 18/12/2025, at 11:25 PM, Souheila Hechaichi via stunnel-users <stunnel-users(a)stunnel.org> wrote: Hey, I hope your help.The problem of 403754EAC87F0000:error:0A000126:SSL routines::unexpected eof while reading:../ssl/record/rec_layer_s3.c:696: is a bug in openssl version 3.x.xWhith my configuration OpenSSL 1.1.1f, the connection succeded but Its systematically closes <image.png> And with tcpdump I observe a connection reset<image.png>Best regards;From: Michał Trojnara via stunnel-users <stunnel-users(a)stunnel.org> Sent: Thursday, December 18, 2025 8:24 PM To: stunnel-users(a)stunnel.org <stunnel-users(a)stunnel.org> Subject: [stunnel-users] Re: stunnel : SSL_connect: Peer suddenly disconnected Hi Souheila, It does not look like your remote machine accepts TLS: $ openssl s_client -connect 52.239.241.136:2049 Connecting to 52.239.241.136 CONNECTED(00000003) 403754EAC87F0000:error:0A000126:SSL routines::unexpected eof while reading:../ssl/record/rec_layer_s3.c:696: Why exactly do you think that stunnel could be used to mount NFS file shares? Stunnel can be a TLS client, but not an NFS client. Those aredifferent protocols. Best regards, Mike On 12/18/25 6:15 PM, Souheila Hechaichi via stunnel-users wrote: I am using stunnel to mount an azure nfs file share. The stunnel process log the following messageDec 18 17:55:20 vmubuntu18 stunnel: LOG3[23840]: SSL_connect: Peer suddenly disconnected The stunnel configure file isverifyChain = nodebug = debugoutput = /etc/stunnel/microsoft/aznfs/nfsv4_fileShare/logs/stunnel_52.239.241.136.logpid = /etc/stunnel/microsoft/aznfs/nfsv4_fileShare/logs/stunnel_52.239.241.136.pidTIMEOUTidle = 61 [52.239.241.136]client = yesaccept = 127.0.0.1:20049connect = 52.239.241.136:2049 A trace with tcpdump display the following logs<image.png> We observe a reset connection between azure server and my machine. Best regardsSouheila _______________________________________________ stunnel-users mailing list -- stunnel-users(a)stunnel.org To unsubscribe send an email to stunnel-users-leave(a)stunnel.org _______________________________________________ stunnel-users mailing list -- stunnel-users(a)stunnel.org To unsubscribe send an email to stunnel-users-leave(a)stunnel.org

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stunnel : SSL_connect: Peer suddenly disconnected
by Souheila Hechaichi 18 Dec '25

18 Dec '25

I am using stunnel to mount an azure nfs file share. The stunnel process log the following message Dec 18 17:55:20 vmubuntu18 stunnel: LOG3[23840]: SSL_connect: Peer suddenly disconnected The stunnel configure file is verifyChain = no debug = debug output = /etc/stunnel/microsoft/aznfs/nfsv4_fileShare/logs/stunnel_52.239.241.136.log pid = /etc/stunnel/microsoft/aznfs/nfsv4_fileShare/logs/stunnel_52.239.241.136.pid TIMEOUTidle = 61 [52.239.241.136] client = yes accept = 127.0.0.1:20049 connect = 52.239.241.136:2049 A trace with tcpdump display the following logs [cid:defde221-2fed-4b36-9480-0181f6f7d5a9] We observe a reset connection between azure server and my machine. Best regards Souheila

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OCSPflag not processed in ocsp_stapling() ?
by King's Way 01 Dec '25

01 Dec '25

Hi there, I was trying to make stunnel ignore OCSP verification error for local certificates when doing OCSP Stapling. But it seems the flag "OCSPflag = NOVERIFY" is not properly passed to openssl. I have tried to patch it in function ocsp_stapling(), and it worked. But I wonder whether it is a bug or intentionally designed this way? With kind regards！ ------------------------------------------------------------ King's Way <io[AT]stdio.io<http://stdio.io>>

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Getting Started - Unique Situation
by Kevin Morris 21 Nov '25

21 Nov '25

Hi All! About me: I've never heard of stunnel before but it sounds great. I'm not a networking/internet expert. Here is my situation: Platform: Microsoft Windows Server 2016. Two Network Interface Cards. Port 443 on both currently have HTTPS/TCP traffic on them, from two different Web Apps, each with their own domain. Everything is working properly, traffic is very low, only a few (about 20) hits per minute (each port) at max load. Both Web Apps are built using Lazarus, Free Pascal, Brook Framework. The Brook Framework has the built-in ability to handle SSL/TLS encryption. Certs are supplied by Let's Encrypt, and new certs are obtained by a bot. I now have a third and soon a forth Web App built using the same technology, but my only two 443 ports are occupied. Here is my requirement: I need something that will act as a "port splitter". Maybe this is also known as a reverse proxy. Example: Incoming URLs on port 443: https://mywebapp.companyname.com/bob/useraccount?act=login&exp=pg https://mywebapp.companyname.com/betty/useraccount?act=login&exp=pg The port splitter needs to recognize the part in teal green (maybe called an "entry point"?), and pass that unchanged traffic through to (and from) a port that the associated Web App is listening on. WebApp "bob" is listening on local port 449 (not exposed to the internet, only conversing with stunnel) WebApp "betty" is listening on local port 451 (not exposed to the internet, only conversing with stunnel) Both Web Apps will send/receive their own HTTPS traffic, handle their own decryption/encryption, and send it back through their respective listening ports, through the port splitter, back the the requesting user. No load balancing is required. No decryption/encryption/certs is/are required. This needs to happen downstream from our router, without making any changes to OS rules or router settings. I'd like to just shut down the current Web App listening on port 443, reconfig it to a new local port As I looked through the FAQ and manual, I could not determine if stunnel could do this. So my questions are: A) Can stunnel do this? B) If so, is there a "How To" I missed in the manual I can read to do this? C) If ((A = Yes) and B = No)), can you tell me in a couple sentences where to look in the config file to do some reading and get this set up? If we can get this working, there are other Lazarus/Brook developers who could benefit from using stunnel. If stunnel is not the answer, is there another "port splitter" piece of software that you know of that can? (other than IIS with ARR and WAP, I don't want to use those, I'm slowly trying to de-Microsoft my infrastructure.) Thanks in advance!

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+=item B<requireCert> = yes | no ignored when client = yes
by u34＠net9.cf 13 Nov '25

13 Nov '25

In my opinion, the following emphasis worth including: --- stunnel.pod.in.orig 2025-10-07 19:50:30.097392645 +0000 +++ stunnel.pod.in.new 2025-10-07 20:25:54.448391940 +0000 @@ -1065,6 +1065,8 @@ =item B<requireCert> = yes | no +Ignored when client = yes. + require a client certificate for I<verifyChain> or I<verifyPeer> With I<requireCert> set to I<no>, the B<stunnel> server accepts client

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stunnel 5.76 core dumped
by Bogdan Siara 02 Nov '25

02 Nov '25

Hi, I try to run stunnel with certs from hardware token and I get error: root@c6b200207f1a:/stunnel-5.76# stunnel free(): invalid pointer Aborted (core dumped) This is my configuration: engine = pkcs11 engineCtrl = MODULE_PATH:/usr/lib/libeToken.so engineCtrl = PIN:pin output = /var/log/stunnel.log debug=debug [in-hdt] client=no accept = 172.18.1.2:443 connect=127.0.0.1:8080 cert = /etc/stunnel/certs/hdt.pem key = /etc/stunnel/certs/hdt.key sessionResume = no options = NO_TICKET retry=yes TIMEOUTclose = 0 debug=debug [in-vpc] client=no accept = 172.18.2.2:443 connect=127.0.0.1:8081 cert = /etc/stunnel/certs/vpc.pem key = /etc/stunnel/certs/vpc.key sessionResume = no options = NO_TICKET retry=yes TIMEOUTclose = 0 debug=debug [in-iam] client=no accept = 172.18.3.2:443 connect=127.0.0.1:8082 cert = /etc/stunnel/certs/iam.pem key = /etc/stunnel/certs/iam.key sessionResume = no options = NO_TICKET retry=yes TIMEOUTclose = 0 debug=debug [out-hdt] client=yes accept=8080 connect=ip1:443 engineId=pkcs11 sni = hdt cert=pkcs11:model=ID%20Prime%20MD;manufacturer=Gemalto;serial=...;token=eToken;id=...;object=...;type=cert key=pkcs11:model=ID%20Prime%20MD;manufacturer=Gemalto;serial=...;token=eToken;id=...;object=...;type=private;pin-value=pin sessionResume = no options = NO_TICKET retry=yes TIMEOUTclose = 0 debug=debug [out-vpc] client=yes accept=8081 connect=ip2:443 engineId=pkcs11 sni = vpc cert=pkcs11:model=ID%20Prime%20MD;manufacturer=Gemalto;serial=...;token=eToken;id=...;object=...;type=cert key=pkcs11:model=ID%20Prime%20MD;manufacturer=Gemalto;serial=...;token=eToken;id=...;object=...;type=private;pin-value=pin sessionResume = no options = NO_TICKET retry=yes TIMEOUTclose = 0 debug=debug [out-iam] client=yes accept=8082 connect=ip3:443 engineId=pkcs11 sni = iam cert=pkcs11:model=ID%20Prime%20MD;manufacturer=Gemalto;serial=...;token=eToken;id=...;object=...;type=cert key=pkcs11:model=ID%20Prime%20MD;manufacturer=Gemalto;serial=...;token=eToken;id=...;object=...;type=private;pin-value=pin sessionResume = no options = NO_TICKET retry=yes TIMEOUTclose = 0 debug=debug When I try run in gdb: root@c6b200207f1a:/stunnel-5.76# gdb stunnel GNU gdb (Ubuntu 12.1-0ubuntu1~22.04.2) 12.1 Copyright (C) 2022 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html > This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. Type "show copying" and "show warranty" for details. This GDB was configured as "x86_64-linux-gnu". Type "show configuration" for configuration details. For bug reporting instructions, please see: <https://www.gnu.org/software/gdb/bugs/>. Find the GDB manual and other documentation resources online at: <http://www.gnu.org/software/gdb/documentation/>. For help, type "help". Type "apropos word" to search for commands related to "word"... Reading symbols from stunnel... (gdb) r Starting program: /usr/local/bin/stunnel [Thread debugging using libthread_db enabled] Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1". [New Thread 0x7ffff789f640 (LWP 4875)] [Thread 0x7ffff789f640 (LWP 4875) exited] [New Thread 0x7ffff789f640 (LWP 4876)] [New Thread 0x7ffff6c78640 (LWP 4878)] free(): invalid pointer Thread 1 "stunnel" received signal SIGABRT, Aborted. __pthread_kill_implementation (no_tid=0, signo=6, threadid=140737346406208) at ./nptl/pthread_kill.c:44 44 ./nptl/pthread_kill.c: No such file or directory. (gdb) stunnel is running in docker container ubuntu:22.04 Can someone tell where is the problem? Regards BS

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Was LOG3[per-minute]: OCSP: SSL_get_certificate for a shared secret, PSK, configuration fixed with 5.76?
by u34＠net9.cf 01 Nov '25

01 Nov '25

Hello, At [stunnel 5.76 released](https://www.stunnel.org/mailman3/hyperkitty/list/stunnel-users@st… - Missing OCSP stapling is no longer logged as an error. was mentioned in Bugfixes. My understanding is [LOG3[per-minute]: OCSP: SSL_get_certificate](https://www.stunnel.org/mailman3/hyperkitty/list/stunn… is fixed. But it isn't.

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Should remote host IPs recorded at lower debug levels too?
by u34＠net9.cf 21 Oct '25

21 Oct '25

Does recording the IPs of the remote host depends on other configuration directives, other then the debug directive? Is it correct that at LOG5, IPs of the remote host are recorded at the log file? Is it correct that at LOG3, no IPs are recorded even when other information for a particular connection is considered worth recording? Aren't IPs considered important information worth recording when error conditions are recorded?

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stunnel 5.76 released
by Michał Trojnara 18 Oct '25

18 Oct '25

Dear Users, I have released version 5.76 of stunnel. ### Version 5.76, 2025.10.18, urgency: MEDIUM * Security bugfixes - OpenSSL DLLs updated to version 3.5.4. - Service-level multivalued options now override (rather than append to) global defaults, preventing unintended configurations. * Bugfixes - Fixed enabling/disabling of the default fips=yes property. - Missing OCSP stapling is no longer logged as an error. - Fixed a crash when a PIN was required due to the PKCS#11 CKA_ALWAYS_AUTHENTICATE attribute. * Features - Quantum-resistant hybrid key agreement X25519+ML-KEM-768 (X25519MLKEM768) used by default with OpenSSL 3.5+ and TLS 1.3. - Multiple cert sources are supported, allowing a certificate to be fetched from a provider while loading the chain from a file. - Android build switched to a 16 KB page size. Home page: https://www.stunnel.org/ Download: https://www.stunnel.org/downloads.html SHA-256 hashes: cda37eb4d0fb1e129718ed27ad77b5735e899394ce040bb2be28bbb937fd79e1 stunnel-5.76.tar.gz d93c7c01366d38ebd27689d606e45197ba8e2e2a32d1a186a81d2b01186bfb56 stunnel-5.76-win64-installer.exe f081281c92f6dc245e23d57930f3963d0155a9fc4a707b7414c941e8e60a1957 stunnel-5.76-android.zip Best regards, Mike

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LOG3[per-minute]: OCSP: SSL_get_certificate
by u34＠net9.cf 15 Oct '25

15 Oct '25

With stunnel version 5.74 and debug = 3 foreground = yes setgid = abcde setuid = abcde output = /path/to/log/file [service] PSKsecrets = /path/to/secretfile accept = ip1:port1 connect = ip2:port1 debug = 3 setgid = abcde setuid = abcde This configuration looks to me similar to the [shell] option from the configuration examples. There is a 1 per minute LOG3[per-minute]: OCSP: SSL_get_certificate line at the log file. Does it a bug? This wasn't discussed 3 weeks ago at [How to get rid of "No OCSP stapling response received" warning?](https://www.stunnel.org/mailman3/hyperkitty/list/stunnel-users@st…, was it?

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Client mode certificate pinning
by Ian Pilcher 11 Oct '25

11 Oct '25

Is $SUBJECT possible? I use stunnel to connect to my old "smart" switches that don't support modern TLS protocols, ciphers, etc. Recently, their existing certificates all expired, and I tried to install new certificates on all of them, only to discover that they won't accept my new CA certificate, because it was signed with a 3072-bit key. I could go through the trouble of generating a separate CA certificate with a 2048-bit key, sign new certificates with that key, etc., etc., but it starts to seem a bit silly at that point. Far better to simply generate a self-signed certificate for each switch and configure stunnel to only accept that particular certificate (i.e. "pin" it). Is this possible with stunnel? If so, how would I go about configuring it to do this? (Search engines are telling me to use "verify = 4", but stunnel(8) says that option is obsolete.) TIA! -- ======================================================================== If your user interface is intuitive in retrospect ... it isn't intuitive ========================================================================

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How to get rid of "No OCSP stapling response received" warning?
by Ian Pilcher 25 Sep '25

25 Sep '25

I use stunnel to connect to my old "smart" switches from modern browsers. Here is a subset of the configuration for one of the switches. [switch1-frontend] sni = frontend:switch1.penurio.us CAfile = /etc/ipa/ca.crt cert = /etc/pki/tls/certs/stunnel/switch1.crt key = /tmp/keys/switch1.key connect = 127.255.255.254:8081 [switch1-backend] client = yes accept = 127.255.255.254:8081 connect = 172.31.4.1:443 verifyChain = yes checkHost = switch1.penurio.us CAfile = /etc/ipa/ca.crt sslVersion = TLSv1 ciphers = DHE-RSA-AES256-SHA options = ALLOW_UNSAFE_LEGACY_RENEGOTIATION securityLevel = 0 OCSPrequire = no OCSPaia = no Everything works, execept that every connection produces a bright red warning in my log: OCSP: No OCSP stapling response received I've read up on OCSP stapling, that this seems to mean that the switch isn't including an OCSP response in its TLS handshake. (Hardly surprising, given its age.) How can I tell stunnel to not request/expect an OCSP response from the switch (or at least to not log the missing OCSP response as a warning)? -- ======================================================================== If your user interface is intuitive in retrospect ... it isn't intuitive ========================================================================

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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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Stunnel, Gmail and Outlook Express
by landjonline＠hotmail.com 01 Sep '25

01 Sep '25

I have Outlook Express and my email addresses are Gmail. Is there a way to get Gmail to work with Outlook Express using Stunnel? Thanks

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Using CAStore on Android (stunnel.conf)
by smf.forum1＠ntlworld.com 31 Jul '25

31 Jul '25

I have build stunnel with a few changes to run in a QThread (Qt 6.9.1) for Android. My Qt App starts stunnel at the start of execution and stops it when my Qt application exits. This all works fine (I need to review and clean up my stunnel changes before I use my solution for real) but I cannot get certification to work, here are two test runs one with verify set to 0 (works) and verify set to 2 (fails). What needs to change in my stunnel.conf file ? Thanks. (obfuscated details) stunnel.conf foreground = yes debug = 6 [mariadb] CAstore = /data/misc/user/0/cacerts-added CApath = /data/misc/user/0/cacerts-added client = yes accept = 127.0.0.1:3307 connect = remote_server:3307 verify = 0 Works: I/stunnel : LOG6[ui]: Initializing inetd mode configuration I/stunnel : LOG5[ui]: stunnel 5.75 on android-mobile-device platform I/stunnel : LOG5[ui]: Compiled/running with OpenSSL 3.1.1 30 May 2023 I/stunnel : LOG5[ui]: Threading:PTHREAD Sockets:SELECT,IPv4 TLS:ENGINE,OCSP,PSK,SNI I/stunnel : LOG6[ui]: Initializing inetd mode configuration I/stunnel : LOG5[ui]: Reading configuration from buffer 0x7280e409b640 I/stunnel : LOG5[ui]: UTF-8 byte order mark not detected I/stunnel : LOG6[ui]: Compression disabled I/stunnel : LOG6[ui]: Initializing service [mariadb] I/stunnel : LOG6[ui]: stunnel default security level set: 2 I/stunnel : LOG6[ui]: Session resumption enabled I/stunnel : LOG6[ui]: Configured trusted server CA: C=AU, ST=Florida, L=York, O=Home, OU=Whiskey, CN=Michael, emailAddress=eric.admin(a)intheether.com W/stunnel : LOG4[ui]: Service [mariadb] needs authentication to prevent MITM attacks I/stunnel : LOG6[ui]: DH initialization skipped: client section I/stunnel : LOG5[ui]: Configuration successful I/stunnel : LOG6[ui]: Service [mariadb] (FD=117) bound to 127.0.0.1:3307 I/stunnel : LOG6[ui]: Accepting new connections I/stunnel : LOG6[per-day]: Executing per-day jobs I/stunnel : LOG6[per-day]: Per-day jobs completed in 0 seconds I/stunnel : LOG5[0]: Service [mariadb] accepted connection from 127.0.0.1:36802 I/stunnel : LOG6[0]: s_connect: connecting 192.168.0.1:3307 I/stunnel : LOG5[0]: s_connect: connected 192.168.0.1:3307 I/stunnel : LOG5[0]: Service [mariadb] connected remote server from 10.0.2.16:58660 I/stunnel : LOG6[0]: SNI: sending servername: remote_server I/stunnel : LOG6[0]: Peer certificate not required I/stunnel : LOG6[0]: Received trusted client CA: C=AU, ST=Florida, L=York, O=Home, OU=Whiskey, CN=Michael, emailAddress=eric.admin(a)intheether.com I/stunnel : LOG6[0]: CERT: Certificate verification disabled I/stunnel : LOG6[0]: CERT: Certificate verification disabled I/stunnel : LOG6[0]: OCSP: Certificate chain verification disabled I/stunnel : LOG6[0]: TLS connected: new session negotiated I/stunnel : LOG6[0]: TLSv1.3 ciphersuite: TLS_AES_256_GCM_SHA384 (256-bit encryption) I/stunnel : LOG6[0]: Peer temporary key: X25519, 253 bits I/stunnel : LOG6[0]: Session id: 90DD6325CCBC47C3F8F560C36F76755B4959E6A8421DD97B751E37FDD1DCCAC7 I/stunnel : LOG6[0]: Session id: 24345E21753FE3B254CA089FB7621C1481B523E72EB9571DDF7A366B5E89E834 stunnel.conf foreground = yes debug = 6 [mariadb] CAstore = /data/misc/user/0/cacerts-added CApath = /data/misc/user/0/cacerts-added client = yes accept = 127.0.0.1:3307 connect = remote_server:3307 verify = 2 Fails: I/stunnel : LOG6[ui]: Initializing inetd mode configuration I/stunnel : LOG5[ui]: stunnel 5.75 on android-mobile-device platform I/stunnel : LOG5[ui]: Compiled/running with OpenSSL 3.1.1 30 May 2023 I/stunnel : LOG5[ui]: Threading:PTHREAD Sockets:SELECT,IPv4 TLS:ENGINE,OCSP,PSK,SNI I/stunnel : LOG6[ui]: Initializing inetd mode configuration I/stunnel : LOG5[ui]: Reading configuration from buffer 0x7280e409b0a0 I/stunnel : LOG5[ui]: UTF-8 byte order mark not detected I/stunnel : LOG6[ui]: Compression disabled I/stunnel : LOG6[ui]: Initializing service [mariadb] I/stunnel : LOG6[ui]: stunnel default security level set: 2 I/stunnel : LOG6[ui]: Session resumption enabled I/stunnel : LOG6[ui]: Configured trusted server CA: C=AU, ST=Florida, L=York, O=Home, OU=Whiskey, CN=Michael, emailAddress=eric.admin(a)intheether.com W/stunnel : LOG4[ui]: Service [mariadb] uses "verifyChain" without subject checks W/stunnel : LOG4[ui]: Use "checkHost" or "checkIP" to restrict trusted certificates I/stunnel : LOG6[ui]: DH initialization skipped: client section I/stunnel : LOG5[ui]: Configuration successful I/stunnel : LOG6[ui]: Service [mariadb] (FD=114) bound to 127.0.0.1:3307 I/stunnel : LOG6[ui]: Accepting new connections I/stunnel : LOG6[per-day]: Executing per-day jobs I/stunnel : LOG6[per-day]: Per-day jobs completed in 0 seconds I/stunnel : LOG5[0]: Service [mariadb] accepted connection from 127.0.0.1:39238 I/stunnel : LOG6[0]: s_connect: connecting 192.168.0.1:3307 I/stunnel : LOG5[0]: s_connect: connected 192.168.0.1:3307 I/stunnel : LOG5[0]: Service [mariadb] connected remote server from 10.0.2.16:59154 I/stunnel : LOG6[0]: SNI: sending servername: remote_server I/stunnel : LOG6[0]: Peer certificate required I/stunnel : LOG6[0]: Received trusted client CA: C=AU, ST=Florida, L=York, O=Home, OU=Whiskey, CN=Michael, emailAddress=eric.admin(a)intheether.com W/stunnel : LOG4[0]: CERT: Pre-verification error: certificate not found in local repository: self-signed certificate W/stunnel : LOG4[0]: Rejected by CERT at depth=0: C=PL, ST=Mazovia Province, L=Warsaw, O=Stunnel Developers, OU=Provisional CA, CN=localhost E/stunnel : LOG3[0]: SSL_connect: tls_post_process_server_certificate@ssl/statem/statem_clnt.c:1890: error:0A000086:SSL routines::certificate verify failed I/stunnel : LOG5[0]: Connection closed/reset: 0 byte(s) sent to TLS, 0 byte(s) sent to socket I/stunnel : LOG6[ui]: Child process 17669 finished with code 0

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Android Stunnel 64bit version
by emxacademy＠gmail.com 18 Jul '25

18 Jul '25

Hello everyone, I've been searching online but still haven’t found a clear or working method to build a 64-bit version of the Android stunnel executable. Since most Android devices now run on 64-bit architecture, the 32-bit version available on the official website no longer works on many phones. If anyone has experience with this or can guide me through the proper way to compile a 64-bit version, I’d really appreciate your help. Thanks in advance!

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Error message when trying to set Stunnel as a start up app
by Edward Smithson 18 Jul '25

18 Jul '25

Hello Stunnel mailing list, We are trying to set Stunnel (5.75) to automatically open as a start up app on Windows 11. When the PC powers up, it gives this error message: stunnel.exe - System Error The code execution cannot proceed because libcrypto-3-x64.dll was not found. Reinstalling the program may fix this problem. We have tried reinstalling, but to no avail. NB, Stunnel works fine if opened manually. This was not an issue with Windows 10. Has anyone else had this problem (and solved it)? Many thanks, Ed Smithson Ed Smithson Reader Services Librarian Nuffield College, Oxford, OX1 1NF +44(0) 1865 278551 [cid:image001.jpg@01DBF637.F9083360]<https://bsky.app/profile/nuffieldlibrary.bsky.social>[cid:image002.png@01DBF637.F9083360]<https://www.facebook.com/NuffieldCollegeLibrary>[cid:image003.png@01DBF637.F9083360]<https://www.instagram.com/nuffieldlibrary/> [cid:image004.png@01DBF637.F9083360]<https://www.nuffield.ox.ac.uk/>

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stunnel with aurora postgreSQL
by Grube, Rolf | Oberender AG 25 Jun '25

25 Jun '25

Hi everybody, Does anybody has already established a connection to AWS aurora postgreSQL with stunnel? I cant establish a connection and it may be an issue with channel binding. My config looks like this: ; Sample stunnel configuration file for Win64 by Michal Trojnara 1998-2025 ; Some options used here may be inadequate for your particular configuration ; This sample file does *not* represent stunnel.conf defaults ; Please consult the manual for detailed description of available options ; ************************************************************************** ; * Global options * ; ************************************************************************** ; Debugging stuff (may be useful for troubleshooting) debug = 7 output = stunnel.log ; Enable FIPS 140-2 mode if needed for compliance fips = yes ; The CNG engine allows to integrate stunnel with the Windows Cryptography API: ; Next Generation (CNG) for authentication with private keys stored in the ; Windows certificate store. It serves as a drop-in replacement for the legacy ; OpenSSL Cryptography API (CAPI) engine. ; https://www.stunnel.org/cng-engine.html ; Each section using this feature also needs the "engineId = cng" option engine = cng ; The pkcs11 engine allows for authentication with cryptographic ; keys isolated in a hardware or software token ; MODULE_PATH specifies the path to the pkcs11 module shared library, ; such as softhsm2-x64.dll or opensc-pkcs11.dll ; IMPORTANT: A 64-bit stunnel requires 64-bit PKCS#11 modules ; Each section using this feature also needs the "engineId = pkcs11" option ;engine = pkcs11 ;engineCtrl = MODULE_PATH:softhsm2-x64.dll ;engineCtrl = PIN:1234 ; ************************************************************************** ; * Service defaults may also be specified in individual service sections * ; ************************************************************************** ; Enable support for the insecure SSLv3 protocol ;options = -NO_SSLv3 ; These options provide additional security at some performance degradation ;options = SINGLE_ECDH_USE ;options = SINGLE_DH_USE ; ************************************************************************** ; * Include all configuration file fragments from the specified folder * ; ************************************************************************** ;include = conf.d ; ************************************************************************** ; * Service definitions (at least one service has to be defined) * ; ************************************************************************** [postgreSQL_TLS] client = yes ;engineId = cng accept = 5433 connect = xxx.rds.amazonaws.com:5432 protocol = pgsql CAfile = C:\cert\xxx-bundle.pem verifyChain = yes checkHost = xxx.rds.amazonaws.com Thanks for any recommendations. Best regards Rolf Grube, MBA Senior Manager <https://www.credly.com/badges/443267d6-0d25-4fc3-9eee-f9654f6f3ee1/public_u rl> Oberender AG Elsenheimerstraße 59 | 80687 München t: +49 89 8207516-0 | m: +49 173 2035 133 <mailto:rolf.grube@oberender.com> rolf.grube(a)oberender.com <http://www.oberender.com/> www.oberender.com Vorsitzender des Aufsichtsrats: Dipl.-Volkswirtin Irmtraut Gürkan Vorstand: Jan Hacker (Vorsitzender), Jochen Baierlein Handelsregister: Amtsgericht Bayreuth, HRB 4267 Sitz der Gesellschaft: Bayreuth Diese E-Mail enthält vertrauliche und/oder rechtlich geschützte Informationen. Wenn Sie nicht der richtige Adressat sind oder diese E-Mail irrtümlich erhalten haben, informieren Sie bitte sofort den Absender und vernichten Sie diese Mail. Das unerlaubte Kopieren, sowie die unbefugte Weitergabe dieser Mail sind nicht gestattet.

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Duplicate Received trusted client CA messages
by Sean Burford 18 Jun '25

18 Jun '25

Hi, While configuring stunnel to connect as a client to a TLS server that requires client certificate auth (known as mutual TLS auth), I noticed that each new connection generates lots (up to hundreds) of duplicate logs like: 2025.06.18 10:23:58 LOG6[0]: Received trusted client CA: CN=Example CA 2025.06.18 10:23:58 LOG6[0]: Received trusted client CA: CN=Example CA I expect one log per trusted client CA provided by the server. Openssl s_client -msg shows that the server only sends a small CertificateRequest. Stunnel logs show that only one connection is made. This only happens if the server offers exactly one trusted client CA. If multiple client CA options are offered by the server then a single log entry is recorded for each. What appears to be happening is that OpenSSL’s state machine generates lots of info callbacks (the number depends on latency). This appears to be harmless except for the excessive logging. I’m running stunnel 5.75 against OpenSSL 3.5.0 (compiled with enable-weak-ssl-ciphers, enable-ssl3 and enable-ssl3-method): $ stunnel [ ] Initializing inetd mode configuration [ ] Clients allowed=125 [.] stunnel 5.75 on sparc-sun-solaris2.10 platform [.] Compiled/running with OpenSSL 3.5.0 8 Apr 2025 [.] Threading:PTHREAD Sockets:POLL,IPv6 TLS:ENGINE,OCSP,PSK,SNI [ ] errno: (*(___errno())) … $ openssl version OpenSSL 3.5.0 8 Apr 2025 (Library: OpenSSL 3.5.0 8 Apr 2025) This is probably NOT caused by an OpenSSL 3.5.0 behaviour change, I also see duplicate messages from the public stunnel build running on Windows: [ ] Initializing inetd mode configuration [ ] Running on Windows 6.2 [ ] No limit detected for the number of clients [.] stunnel 5.74 on x64-pc-mingw32-gnu platform [.] Compiled/running with OpenSSL 3.3.2 3 Sep 2024 [.] Threading:WIN32 Sockets:SELECT,IPv6 TLS:ENGINE,FIPS,OCSP,PSK,SNI [ ] errno: (*_errno()) To diagnose this further, I modified stunnel src/ctx.c info_callback() to log the TLS state in callbacks: //#if 0 // s_log(LOG_DEBUG, "state = %x", state); state_string=SSL_state_string_long(ssl); s_log(LOG_DEBUG, "TLS state (where %08X state %08X): %s", where, state, state_string); //#endif This shows that there are many callbacks from where SSL_CB_ACCEPT_EXIT and one final callback from SSL_CB_ACCEPT_LOOP: 2025.06.18 10:23:58 LOG6[0]: Received trusted client CA: CN=Example CA 2025.06.18 10:23:58 LOG7[0]: TLS state (where 00001002 state 00000008): SSLv3/TLS read server certificate request 2025.06.18 10:23:58 LOG6[0]: Received trusted client CA: CN=Example CA 2025.06.18 10:23:58 LOG7[0]: TLS state (where 00001002 state 00000008): SSLv3/TLS read server certificate request 2025.06.18 10:23:58 LOG6[0]: Received trusted client CA: CN=Example CA 2025.06.18 10:23:58 LOG7[0]: TLS state (where 00001002 state 00000008): SSLv3/TLS read server certificate request 2025.06.18 10:23:58 LOG6[0]: Received trusted client CA: CN=Example CA 2025.06.18 10:23:58 LOG7[0]: TLS state (where 00001001 state 00000008): SSLv3/TLS read server certificate request 2025.06.18 10:23:58 LOG6[0]: Received trusted client CA: CN=Example CA 2025.06.18 10:23:58 LOG7[0]: TLS state (connect): SSLv3/TLS read server certificate request Modifying info_callback to look for SSL_CB_LOOP in where suppresses the excess messages: /* log the client certificate request (if received) */ #ifndef SSL3_ST_CR_CERT_REQ_A if(state==TLS_ST_CR_CERT_REQ && *where & SSL_CB_LOOP*) #else if(state==SSL3_ST_CR_CERT_REQ_A && *where & SSL_CB_LOOP*) #endif print_CA_list("Received trusted client CA", SSL_get_client_CA_list(ssl)); Here’s my config: debug=info [outbound-http-to-https-mtls] accept = 127.0.0.1:8447 connect = 127.0.0.1:8445 client = yes ; verify 2 - verify peer certificate chain verify = 2 sni = www.example.com checkHost = www.example.com verifyChain = yes CAfile = /export/home/user/stunnel/trusted-ca-certs.pem ; Authenticate ourselves to peer using a client certificate. cert = /export/home/user/stunnel/user.ecdsa-p256.pem key = /export/home/user/stunnel/user.ecdsa-p256.key -- Thanks, Sean Burford

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[PATCH 0/3] Improve stunnel performance by ~17%
by Edwin Torok 12 Jun '25

12 Jun '25

Hello, Flamegraph profiling on stunnel has shown that most time is NOT spent in encryption/decryption, but in sending/receiving data. Experimental setup: ``` CPU: 2x 18-core Intel Xeon Gold 6354 NIC: Intel E810-XXV, 100 Gbit/s Kernel: 6.14.8-300.fc42.x86_64 x86_64 Mem: 251.32 GiB OS: Fedora Linux 42 openssl version: OpenSSL 3.2.4 11 Feb 2025 (Library: OpenSSL 3.2.4 11 Feb 2025) stunnel: 5.75 from git ``` Network, encryption and memory copy speeds converted into Gbit/s on the above HW: ``` iperf3: 40Gbit/s openssl speed -evp aes-256-gcm: 72Gbit/s perf bench memcpy: 100Gbit/s ``` Under ideal conditions we should be able to achieve at most ~20.5Gbit/s, however I only measured ~7.6Gbit/s. The scripts that I used to perform measurements are included in the attached patch 3. See also related discussion on curl: https://github.com/curl/curl/pull/17548 Enabling readahead, avoiding excessive alloc/free of buffers, increasing buffer sizes, and improving buffer handling can all improve performance. For now I'm sending just the first small patches as proofs of concept, each of them one-liners. I hope you can include these in some form in the next release. Eventually these should probably be exposed as configuration flags in stunnel.conf, I can help implementing that, or I can leave implementing that to you if you prefer. In fact readahead was enabled in previous versions of stunnel, and then disabled again, so I assume you ran into some bugs with it on certain protocols? Increasing the buffer size is not a clear win (as with curl), due to the excessive use of memmove/memset, and that SSL_read/SSL_write only still processes 1 TLS record at a time. I have some further changes that can improve that, but the patches are larger and I haven't finished testing them for correctness yet. Please let me know if you'd want these as patches, or if you'd rather implement them yourself. Edwin Török (3): openssl: enable readahead openssl: disable SSL_MODE_RELEASE_BUFFERS Benchmark scripts src/ctx.c | 5 +- tests/benchmark/benchmark.sh | 120 +++++++++++++++++++++++ tests/benchmark/launch.sh | 185 +++++++++++++++++++++++++++++++++++ 3 files changed, 309 insertions(+), 1 deletion(-) create mode 100644 tests/benchmark/benchmark.sh create mode 100755 tests/benchmark/launch.sh -- 2.43.5

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