Special characters allowed for aliases which are not allowed in index names

[robin13]

Elasticsearch version: 5.0.0-alpha5

Plugins installed: [] x-pack

JVM version:1.8.0_101

OS version: Ubuntu 14.04

Description of the problem including expected versus actual behavior:

Steps to reproduce:

It is possible to use special characters, e.g. * in aliases which are not allowed in Index names. I think this is a bug as it can lead to very confusing states - below is an example:

PUT /foo
PUT /bar

# This will fail with invalid_index_name_exception
PUT /foo*

PUT /foo/bar/1
{
  "message": "Indexed into /foo/bar/1"
}

PUT /bar/bar/1
{
  "message":"Idexed into /bar/bar/1"
}

# This will fail� with invalid_index_name_exception
PUT /bar*/bar/2
{
  "message":"Indexed into /bar*/bar/2"
}

POST /_aliases
{
  "actions":[
    {"add": { "index": "foo", "alias":"bar*" } }
    ]
}

# Now this will be successful - confusing!
PUT /bar*/bar/2
{
  "message":"Indexed into /bar*/bar/2"
}

# A search on indexes /bar* responds with results both from the index `bar` and from `foo` as a result of the alias.
GET /bar*/_search
{
  "took": 3,
  "timed_out": false,
  "_shards": {
    "total": 10,
    "successful": 10,
    "failed": 0
  },
  "hits": {
    "total": 3,
    "max_score": 1,
    "hits": [
      {
        "_index": "foo",
        "_type": "bar",
        "_id": "2",
        "_score": 1,
        "_source": {
          "message": "Indexed into /bar*/bar/2"
        }
      },
      {
        "_index": "bar",
        "_type": "bar",
        "_id": "1",
        "_score": 1,
        "_source": {
          "message": "Idexed into /bar/bar/1"
        }
      },
      {
        "_index": "foo",
        "_type": "bar",
        "_id": "1",
        "_score": 1,
        "_source": {
          "message": "Indexed into /foo/bar/1"
        }
      }
    ]
  }
}