acme: return proper error on malformed account payload

ACMEAccountService currently throws an uncaught exception if decode
the account object payload fails.  This results in the server
responding 500 Internal Server Error.  Respond with status 400 and
a proper problem document instead.

base/acme/src/main/java/org/dogtagpki/acme/server/ACMEAccountService.java

@@ -17,6 +17,8 @@
 import javax.ws.rs.core.Response.ResponseBuilder;
 import javax.ws.rs.core.UriInfo;
 
+import com.fasterxml.jackson.core.JsonProcessingException;
+
 import org.dogtagpki.acme.ACMEAccount;
 import org.dogtagpki.acme.ACMEHeader;
 import org.dogtagpki.acme.ACMENonce;
@@ -74,7 +76,12 @@ public Response updateAccount(@PathParam("id") String accountID, JWS jws) throws
         String payload = new String(jws.getPayloadAsBytes(), "UTF-8");
         logger.info("Payload: " + payload);
 
-        ACMEAccount update = ACMEAccount.fromJSON(payload);
+        ACMEAccount update;
+        try {
+            update = ACMEAccount.fromJSON(payload);
+        } catch (JsonProcessingException e) {
+            throw engine.createMalformedException(e.toString());
+        }
 
         String newStatus = update.getStatus();
         if (newStatus != null) {

base/acme/src/main/java/org/dogtagpki/acme/server/ACMEEngine.java

@@ -728,6 +728,18 @@ public Exception createAccountDoesNotExistException(String accountID) {
         return new WebApplicationException(builder.build());
     }
 
+    public Exception createMalformedException(String desc) {
+        ResponseBuilder builder = Response.status(Response.Status.BAD_REQUEST);
+        builder.type("application/problem+json");
+
+        ACMEError error = new ACMEError();
+        error.setType("urn:ietf:params:acme:error:malformed");
+        error.setDetail("Malformed request: " + desc);
+        builder.entity(error);
+
+        return new WebApplicationException(builder.build());
+    }
+
     public void updateAccount(ACMEAccount account) throws Exception {
         database.updateAccount(account);
     }