Re: VPN suggestions centos 6, 7

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On Mon, 18 Apr 2016, david wrote:

FOLLOWUP & REPORT

I had lots of suggestions, and the most persuasive was to try OpenVPN. I already had a CA working, so issuing certificates was easy. The HOW-TO guides were less helpful than I could hope, but comparing several of them, applying common sense, and trying things out, I arrived at a dead-end. Here's essentially what happened:

- None of the HOW-TOs were very clear about the need to add some attributes to a certificate, keyUsage and extendedKeyUsage. They had different values for server and client. OpenSSL documentation was a big vague on how to add them, but I think I did - the print out of the entity certificates showed the values. The attempt to connect failed. The client log is below. I think it's complaining that the CA certificate doesn't have the ke Usage extension, which makes no sense to me. Such an extension should be in the end-entity certificate, not the CA's, unless I'm wrong. I checked the server and really think that the certificates are in the right place.

Here's how I managed that in my openssl.cnf file. Lots of bits ellided for clarity's sake:

### start ###
[ ca ]
default_ca = CA_default

[ CA_default ]
x509_extensions = server_cert

[ server_cert ]
basicConstraints=CA:FALSE
keyUsage = nonRepudiation, dataEncipherment, digitalSignature, keyEncipherment
extendedKeyUsage = serverAuth, clientAuth
nsCertType = server, client
### end ###

I think the nsCertType directive may be unnecessary these days, but I keep it around because it doesn't hurt anything.

The important bit is the extendedKeyUsage line; I'm pretty sure that an OpenVPN server needs the serverAuth extension. For instance, here is the X509 extensions configuration for a server used by EasyRSA:

  basicConstraints = CA:FALSE
  subjectKeyIdentifier = hash
  authorityKeyIdentifier = keyid,issuer:always
  extendedKeyUsage = serverAuth,clientAuth
  keyUsage = digitalSignature,keyEncipherment

You can ask openssl to tell you the purpose of a certificate:

[bash]$ openssl x509 -noout -purpose -in cert.pem  | grep SSL
SSL client : Yes
SSL client CA : No
SSL server : Yes
SSL server CA : No
Netscape SSL server : Yes
Netscape SSL server CA : No

Anyway, those are the extensions that should do away with these errors:

Mon Apr 18 05:34:50 2016 VERIFY OK: depth=1, C=US, ST=California, L=San Francisco, OU=Certificate Authority, O=XXXX, CN=X.X.X
Mon Apr 18 05:34:50 2016 Certificate does not have key usage extension

--
Paul Heinlein <> heinlein@xxxxxxxxxx <> http://www.madboa.com/
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