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Summary 0021401: OpenVPN deprecated parameters
Revision 2018-09-07 03:48 by NickH
Description From our configs there are two deprecated parameters, comp-lzo and "ns-cert-type server". See https://community.openvpn.net/openvpn/wiki/DeprecatedOptions. [^]

It is not known when comp-lzo will be removed and it can directly be replaced with "compress lzo" in both the client and server configs, but better would be to change the server configs to:
    compress lz4
    push "compress lz4"

and the client config to:
    compress.

This appears to be backwards compatible with existing Windows, linux and Android v2.4 clients.

This has not been tested with older clients but I would expect changing "comp-lzo" to "compress lzo" in the current server config and new client configs to be safe.

The big issue "ns-cert-type" which will disappear in OpenVPN 2.5 (timing unknown). If used in 2.5, it will be remapped to "remote-cert-tls" when it will fail because of the sys-0-pem not containing the required extended key usage of "TLS Web Server Authentication". The solution in the short term is to regenerate the sys-0-pem with the additional EKU. Longer term, "ns-cert-type server" should also be changed to "remote-cert-tls server" in the client configs, but not until the certificate change is made.
Revision 2018-09-07 03:49 by NickH
Description From our configs there are two deprecated parameters, comp-lzo and "ns-cert-type server". See https://community.openvpn.net/openvpn/wiki/DeprecatedOptions. [^]

It is not known when comp-lzo will be removed and it can directly be replaced with "compress lzo" in both the client and server configs, but better would be to change the server configs to:
    compress lz4
    push "compress lz4"

and the client config to:
    compress.

This appears to be backwards compatible with existing Windows, linux and Android v2.4 clients.

This has not been tested with older clients but I would expect changing "comp-lzo" to "compress lzo" in the current server config and new client configs to be safe.

The big issue "ns-cert-type" which will disappear in OpenVPN 2.5 (timing unknown). If used in 2.5, it will be remapped to "remote-cert-tls" when it will fail because of the sys-0-pem not containing the required extended key usage of "TLS Web Server Authentication". The solution in the short term is to regenerate the sys-0-pem with the additional EKU. Longer term, "ns-cert-type server" should also be changed to "remote-cert-tls server" in the client configs, but not until the certificate change is made.

In the client logs the error with "remote-cert-tls server" is:
Fri Sep 07 10:22:51 2018 VERIFY OK: depth=1, C=GB, L=Petersfield, O=ClearOS, OU=14 Upper Heyshott, CN=ca.server.howitts.lan, emailAddress=security@server.howitts.lan, O=Howitt Family, ST=Hampshire
Fri Sep 07 10:22:51 2018 VERIFY KU OK
Fri Sep 07 10:22:51 2018 Certificate does not have extended key usage extension
Fri Sep 07 10:22:51 2018 VERIFY EKU ERROR
Fri Sep 07 10:22:51 2018 OpenSSL: error:1416F086:SSL routines:tls_process_server_certificate:certificate verify failed
Fri Sep 07 10:22:51 2018 TLS_ERROR: BIO read tls_read_plaintext error
Fri Sep 07 10:22:51 2018 TLS Error: TLS object -> incoming plaintext read error
Fri Sep 07 10:22:51 2018 TLS Error: TLS handshake failed
Fri Sep 07 10:22:51 2018 Fatal TLS error (check_tls_errors_co), restarting