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Needing TLS handshake to fail

Phillip Odam
September 04, 2019 08:36AM
Hi,

I tried asking the following on the general mailing list but I'm
guessing this is tending more towards development.

I have a project that involves mutual / two way TLS and one of the
requirements is that the TLS handshake must fail ie. be terminated
before completion if the handshake is in anyway unsuccessful, eg. no
client certificate provided or client certificate not trusted.

After having no success getting nginx (v1.16.1) & openssl (v1.0.2k-fips)
to fail the handshake I ended up looking at the nginx source code, in
particular src/event/ngx_event_openssl.c, and from what I read here
https://www.openssl.org/docs/man1.0.2/man3/SSL_CTX_set_verify.html I
think a small but necessary code change is required.

Some possible approaches when choosing to remain using nginx as the
server end of the mutual TLS connection

* in *static int ngx_ssl_verify_callback(int ok, X509_STORE_CTX
*x509_store)* make it configurable whether *1* is always returned or
the value of *ok*
* in *ngx_int_t ngx_ssl_client_certificate(ngx_conf_t *cf, ngx_ssl_t
*ssl, ngx_str_t *cert, ngx_int_t depth)* make it configurable
whether *SSL_CTX_set_verify(ssl->ctx, SSL_VERIFY_PEER,
ngx_ssl_verify_callback);* is called or
*SSL_CTX_set_verify(ssl->ctx, SSL_VERIFY_PEER, NULL);*

Is a code change required or is there a way for the handshake failure to
be 'enabled' as opposed to ending up with a successfully established TLS
connection. Admittedly within nginx there's all the detail that the TLS
connection doesn't conform to the configured requirements of the TLS
connection but this doesn't satisfy the requirements for the project.

I won't bother going in to the details of the project but will just say
it's a third party certification body that requires the TLS handshake to
be terminated before completion if the handshake is in anyway
unsuccessful. We're currently looking at alternate software but would
really love to be able to pull this back in to nginx when/if the day
comes that nginx supports this.

Assuming development is required, is this something already on the
backlog? My only comment for enabling the TLS handshake failure is it'd
be really nice if it were configurable at the level of the virtual host.

Regards,

Phillip
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Subject Author Views Posted

Needing TLS handshake to fail

Phillip Odam 77 September 04, 2019 08:36AM

Re: Needing TLS handshake to fail

Maxim Dounin 25 September 04, 2019 08:50AM

Re: Needing TLS handshake to fail

Phillip Odam 23 September 04, 2019 09:26AM

Re: Needing TLS handshake to fail

Maxim Dounin 39 September 04, 2019 10:38AM



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