Hi,

> For OpenVPN server certificates it is recommended to set nsCertType = server 
> to avoid misuse e.g. MITM attacks.
> 
> In the profile sample file and in the code in 
> /OpenXPKI/Crypto/Backend/OpenSSL/Config.pm it seems not to be possible to set 
> it as server but I am able to set every other value for nsCertType like 
> client, email, sslCA but not server.
> 
> Is there any reason for this?
> 
> References:
> * https://www.openssl.org/docs/apps/x509v3_config.html
> * 
> http://openvpn.net/index.php/open-source/documentation/miscellaneous/77-rsa-key-management.html

I recommend against that, this is a proprietary extension that nowadays should 
be considered obsolete. The referenced documentation is incorrect/outdated, any 
RFC 5246 compliant TLS implementation will not use this extension at all (in 
fact I know this is the case for OpenVPN, as I am using it myself...).

In order to avoid the MITM scenario mentioned in the docs you referenced use 
the setting
--remote-cert-tls client|server
instead.


For a pure OpenVPN server use a profile that has the following properties:

Key Usage:
digitalSignature (for DHE key agreement)
keyEncipherment (for RSA key agreement w/o PFS)

Extended Key Usage:
serverAuth

For a pure VPN client choose:

Key Usage:
digitalSignature (for DHE key agreement)

Extended Key Usage:
clientAuth


For a VPN server that acts in both roles use a profile that has the union of 
those flags set.

Regards,

Martin


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