Fix OIDC flags

pkg/kubeapiserver/options/authentication.go

@@ -203,7 +203,11 @@ func (o *BuiltInAuthenticationOptions) WithClientCert() *BuiltInAuthenticationOp
 
 // WithOIDC set default value for OIDC authentication
 func (o *BuiltInAuthenticationOptions) WithOIDC() *BuiltInAuthenticationOptions {
-	o.OIDC = &OIDCAuthenticationOptions{areFlagsConfigured: func() bool { return false }}
+	o.OIDC = &OIDCAuthenticationOptions{
+		areFlagsConfigured: func() bool { return false },
+		UsernameClaim:      "sub",
+		SigningAlgs:        []string{"RS256"},
+	}
 	return o
 }
 
@@ -353,33 +357,33 @@ func (o *BuiltInAuthenticationOptions) AddFlags(fs *pflag.FlagSet) {
 			"The URL of the OpenID issuer, only HTTPS scheme will be accepted. "+
 			"If set, it will be used to verify the OIDC JSON Web Token (JWT).")
 
-		fs.StringVar(&o.OIDC.ClientID, oidcClientIDFlag, o.OIDC.ClientID,
+		fs.StringVar(&o.OIDC.ClientID, oidcClientIDFlag, o.OIDC.ClientID, ""+
 			"The client ID for the OpenID Connect client, must be set if oidc-issuer-url is set.")
 
 		fs.StringVar(&o.OIDC.CAFile, oidcCAFileFlag, o.OIDC.CAFile, ""+
 			"If set, the OpenID server's certificate will be verified by one of the authorities "+
 			"in the oidc-ca-file, otherwise the host's root CA set will be used.")
 
-		fs.StringVar(&o.OIDC.UsernameClaim, oidcUsernameClaimFlag, "sub", ""+
+		fs.StringVar(&o.OIDC.UsernameClaim, oidcUsernameClaimFlag, o.OIDC.UsernameClaim, ""+
 			"The OpenID claim to use as the user name. Note that claims other than the default ('sub') "+
 			"is not guaranteed to be unique and immutable. This flag is experimental, please see "+
 			"the authentication documentation for further details.")
 
-		fs.StringVar(&o.OIDC.UsernamePrefix, oidcUsernamePrefixFlag, "", ""+
+		fs.StringVar(&o.OIDC.UsernamePrefix, oidcUsernamePrefixFlag, o.OIDC.UsernamePrefix, ""+
 			"If provided, all usernames will be prefixed with this value. If not provided, "+
 			"username claims other than 'email' are prefixed by the issuer URL to avoid "+
 			"clashes. To skip any prefixing, provide the value '-'.")
 
-		fs.StringVar(&o.OIDC.GroupsClaim, oidcGroupsClaimFlag, "", ""+
+		fs.StringVar(&o.OIDC.GroupsClaim, oidcGroupsClaimFlag, o.OIDC.GroupsClaim, ""+
 			"If provided, the name of a custom OpenID Connect claim for specifying user groups. "+
 			"The claim value is expected to be a string or array of strings. This flag is experimental, "+
 			"please see the authentication documentation for further details.")
 
-		fs.StringVar(&o.OIDC.GroupsPrefix, oidcGroupsPrefixFlag, "", ""+
+		fs.StringVar(&o.OIDC.GroupsPrefix, oidcGroupsPrefixFlag, o.OIDC.GroupsPrefix, ""+
 			"If provided, all groups will be prefixed with this value to prevent conflicts with "+
 			"other authentication strategies.")
 
-		fs.StringSliceVar(&o.OIDC.SigningAlgs, oidcSigningAlgsFlag, []string{"RS256"}, ""+
+		fs.StringSliceVar(&o.OIDC.SigningAlgs, oidcSigningAlgsFlag, o.OIDC.SigningAlgs, ""+
 			"Comma-separated list of allowed JOSE asymmetric signing algorithms. JWTs with a "+
 			"supported 'alg' header values are: RS256, RS384, RS512, ES256, ES384, ES512, PS256, PS384, PS512. "+
 			"Values are defined by RFC 7518 https://tools.ietf.org/html/rfc7518#section-3.1.")