[stunnel-users] public domain [PATCH] to stunnel v456 to clear SSL_OP_LEGACY_SERVER_CONNECT

Simner, John john.simner at unify.com
Wed Jun 25 15:34:31 CEST 2014

Dear Michal, Dear All,
Please find attached a patch to stunnel 4.56 to clear SSL_OP_LEGACY_SERVER_CONNECT.

There was a security requirement to ensure that the stunnel client could not connect to unpatched servers.

I am aware from OpenSSL (https://www.openssl.org/docs/ssl/SSL_CTX_set_options.html ) that this parameter is currently set by default and has to be manually cleared by calling SSL_CTX_clear_options() or SSL_clear_options()if an OpenSSL client applications wants to ensure they can not connect to unpatched servers (and thus avoid any security issues).

The attached patch achieves this.

OpenSSL also state "As more servers become patched the option SSL_OP_LEGACY_SERVER_CONNECT will not be set by default in a future version of OpenSSL" so this patch is only required until OpenSSL change the default value.


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John Simner BSc(Hons) MSc CEng. MIET
Software Engineer, Devices Development

Unify Enterprise Communications Ltd.

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