Is there a way to check if a certificate is client cert or server cert? - certificate

Question

I received a new keystore .jks file for ssl connection to replace an old, but working, .jks keystore file, but I got "unexpected handshake message: serve_hello" error. I was told to make sure the keystore contains a client cert, so I used keytool to export its cert to a pem file, then use openssl to check the purpose. The result shows
Certificate purposes:
SSL client : No
SSL client CA : No
SSL server : Yes
SSL server CA : No
...
However when I applied the same process to check the old but working jks file I got the same result. Wonder if this is the right way to verify the certificate? And how to troubleshooting this handshake error with the new jks file?
Thanks!

Answer 1

The extended key usage extension contains OIDs which define the purpose:
id-kp-serverAuth OBJECT IDENTIFIER ::= { id-kp 1 }
-- TLS WWW server authentication
-- Key usage bits that may be consistent: digitalSignature,
-- keyEncipherment or keyAgreement
id-kp-clientAuth OBJECT IDENTIFIER ::= { id-kp 2 }
-- TLS WWW client authentication
-- Key usage bits that may be consistent: digitalSignature
-- and/or keyAgreement
https://datatracker.ietf.org/doc/html/rfc5280 Page 44
See: https://oidref.com/1.3.6.1.5.5.7.3.1 and https://oidref.com/1.3.6.1.5.5.7.3.2
When opening a certificate on Windows you can see the extension here: