środa, 16 marca 2016

ElasticSearch AWS cloud plugin problem connecting to Riak S3 endpoint without wildcard certs

The other day at work we were trying to use our enterprise installation of Riak S3 (open-source version of AWS S3) to store backups of some ElasticSearch instance. ElasticSearch itself is a mature project so it wasn't a surprise that there's already plugin for storing snapshots using S3 protocol. So we prepared our query and expected it to work out-of-the-box.

curl -XPUT 'http://es.address.here:9200/_snapshot/s3_dev_backup?verify=false' -d '{
        "type": "s3",
        "settings": {
                "access_key": "*****-***-**********",
                "secret_key": "****************************************",
                "bucket": "elastic",
                "endpoint": "s3_cloud_front.address.here"

As usual, in corporate reality, it didn't work. Instead, we got following exception.

Error injecting constructor, com.amazonaws.AmazonClientException: Unable to execute HTTP request: hostname in certificate didn't match: <elastic.s3_cloud_front.address.here> != <s3_cloud_front.address.here> OR <s3_cloud_front.address.here>
  at org.elasticsearch.repositories.s3.S3Repository.<init>(Unknown Source)
  while locating org.elasticsearch.repositories.s3.S3Repository
  while locating org.elasticsearch.repositories.Repository

So apparently endpoint certificate (self signed one, btw) wasn't prepared in such a way that both e.g. endpoint.address and subdomain.endpoint.address would match. In other words it wasn't wildcard certificate bound to the endpoint domain name.

We decided to debug with StackOverflow (it's common technique nowadays, isn't it :D?). After trying numerous solutions like disabling certificate check using java flags or even using so-called java agents to hijack default hostname verifier we ran out of ideas how to elegantly solve the problem. And here comes our ultimate hack - hijacking Apache httpclient library.

The idea behind the hack is simple - re-compile httpclient library with one small modification - put premature return statement at the very top of hostname verification function. The function, where the change should be made is as follows.


One thing to remember is that the return statement must be wrapped with some silly if statement (e.g. if (1 == 1)), so the compiler won't complain about unreachable code below. It's funny that java compiler doesn't eliminate such trivial things, but in this particular scenario it was a feature rather than a bug. If the verifyHostname method wasn't throwing an exception then the modification would be even simpler - just an return statement.

The change is trivial, so I'm not including it here. The last step is to replace httpclient jar in AWS cloud plugin with raped one and we're done. No more complains about SSL hostnames.

Brak komentarzy:

Prześlij komentarz