Update go-jose to 2.3.0.

This is a dependency for smallstep/cli#105, it will be solved once
square/go-jose#224 gets merged

Gopkg.lock

@@ -460,7 +460,7 @@
   version = "v0.9.1"
 
 [[projects]]
-  digest = "1:7fbe10f3790dc4e6296c7c844c5a9b35513e5521c29c47e10ba99cd2956a2719"
+  digest = "1:005cbf8b937fcb1694b9dbb845b0aef618627be7faf7bb330eb2490e3f506ef8"
   name = "gopkg.in/square/go-jose.v2"
   packages = [
     ".",
@@ -469,8 +469,8 @@
     "jwt",
   ]
   pruneopts = "UT"
-  revision = "ef984e69dd356202fd4e4910d4d9c24468bdf0b8"
-  version = "v2.1.9"
+  revision = "628223f44a71f715d2881ea69afc795a1e9c01be"
+  version = "v2.3.0"
 
 [[projects]]
   digest = "1:342378ac4dcb378a5448dd723f0784ae519383532f5e70ade24132c4c8693202"

authority/authorize.go

@@ -47,7 +47,7 @@ func (a *Authority) Authorize(ott string) ([]provisioner.SignOption, error) {
 	// Do not accept tokens issued before the start of the ca.
 	// This check is meant as a stopgap solution to the current lack of a persistence layer.
 	if a.config.AuthorityConfig != nil && !a.config.AuthorityConfig.DisableIssuedAtCheck {
-		if claims.IssuedAt > 0 && claims.IssuedAt.Time().Before(a.startTime) {
+		if claims.IssuedAt != nil && claims.IssuedAt.Time().Before(a.startTime) {
 			return nil, &apiError{errors.New("authorize: token issued before the bootstrap of certificate authority"),
 				http.StatusUnauthorized, errContext}
 		}