Indeed, I forgot to mention that if you only use the public part in the cert parameter, you need to use the key parameter to provide the private part of the certificate. Here is a sample of a configuration that I use in production [Client] client = yes accept = ….. connect = …... CAfile = keys/client/ca-chain-client.cert.pem # --> Contains the server leaf public part, the intermediate CA public part and the root CA public part cert = keys/client/public.pem # --> public part of the client leaf certificate key = keys/client/private.key # --> private part of the client leaf certificate checkHost = xxxx # --> verify the Common Name provided in the server certificate [Server] CAfile = keys/server/ca-chain-server.cert.pem # --> Contains the client leaf public part, the intermediate CA public part and the root CA public part cert = keys/server/public.pem key = keys/server/private.key client = no accept = ….. connect = ….. As stated before, I also use the verifyPeer and verifyChain parameters in the main stunnel.conf file to enable mutual authentication. Best regards, Florian Stosse Information security engineer Safran Electronics & Defense | Safran Data Systems | Space & Communication Phone: +33 1 69 82 79 43 • Mobile : +33 6 48 11 16 12 Safran Data Systems 5, avenue des Andes - CS 90101 91978 Courtaboeuf Cedex, France www.safran-electronics-defense.com De : Giulio Regazzo [mailto:[email protected]] Envoyé : lundi 16 novembre 2020 10:08 À : STOSSE Florian (SAFRAN ELECTRONICS & DEFENSE) Cc : [email protected] Objet : Re: [stunnel-users] PSK Configuration Hi, using only the public part as cert option in client side results in a load error. Seems that, loading the configuration, stunnel checks the presence of both certificate parts and also that public and private parts are compatible. The other option you are suggesting is something like the following? [Server] cert=wholeCert.pem verifyChain=yes CAFile=publicCert.pem [Client] verifyChain=yes CAFile=publicCert.pem Il giorno lun 16 nov 2020 alle ore 09:49 STOSSE Florian (SAFRAN ELECTRONICS & DEFENSE) <[email protected]> ha scritto: Hello, Have you tried using only the public part of the CA chain in the “cert=” parameter, client-side ? Your second option would look like this: [Server] cert=wholeCert.pem verifyPeer=yes [Client] verifyPeer=yes cert=publicCert.pem CAFile=publicCert.pem Additionally, if you use the whole chain (Root + Intermediate + … + Leaf certs), you can specifiy a CAFile parameter server-side, and enable the verifyChain parameter on both sides. Best regards, Florian Stosse Information security engineer Safran Electronics & Defense | Safran Data Systems | Space & Communication Phone: +33 1 69 82 79 43 • Mobile : +33 6 48 11 16 12 Safran Data Systems 5, avenue des Andes - CS 90101 91978 Courtaboeuf Cedex, France www.safran-electronics-defense.com De : Giulio Regazzo [mailto:[email protected]] Envoyé : lundi 16 novembre 2020 09:29 À : [email protected] Objet : [stunnel-users] PSK Configuration Hi, I'm new to stunnel. And I'm trying to configure a server that accepts TCP sockets connections only from clients that have a pre-shared certificate. Looking at the online documentation I found the verifyPeer option, but it is described to be used on client side. Trying to use it on server side I achieved my goal but only if the client has the whole certificate (private + public). My question is: Can I obtain in some way the same result sharing only the public part of the certificate? Currently I'm using a configuration like this one (skipping the accept and connect options): [Server] cert=wholeCert.pem verifyPeer=yes [Client] cert=wholeCert.pem verifyPeer=yes CAFile=wholeCert.pem and I'm looking for something like: [Server] cert=wholeCert.pem verifyPeer=yes [Client] verifyPeer=yes CAFile=publicCert.pem If I try this second option the server refuses the connection in handshake phase saying that the client didn't provide any certificate. Is there a way to achieve this? Thank you. # " Ce courriel et les documents qui lui sont joints peuvent contenir des informations confidentielles, être soumis aux règlementations relatives au contrôle des exportations ou ayant un caractère privé. S'ils ne vous sont pas destinés, nous vous signalons qu'il est strictement interdit de les divulguer, de les reproduire ou d'en utiliser de quelque manière que ce soit le contenu. 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