Permissions to access ElasticSearch from Lambda?

For external (outside AWS) access to your Elasticsearch cluster, you want to create the cluster with an IP-based access policy. Something like the below:

{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Sid": "",
      "Effect": "Allow",
      "Principal": {
        "AWS": "*"
      },
      "Action": "es:*",
      "Condition": {
        "IpAddress": {
          "aws:SourceIp": [
            "<<IP/CIDR>>"
          ]
        }
      },
      "Resource": "arn:aws:es:<<REGION>>:<<ACCOUNTID>>:domain/<<DOMAIN_NAME>>/*"
    }
  ]
}

For your Lambda function, create the role that the Lambda function will assume with the below policy snippet.

{
  "Sid": "",
  "Effect": "Allow",
  "Action": [
    "es:DescribeElasticsearchDomain",
    "es:DescribeElasticsearchDomains",
    "es:DescribeElasticsearchDomainConfig",
    "es:ESHttpPost",
    "es:ESHttpPut"
  ],
  "Resource": [
    "arn:aws:es:<<REGION>>:<<ACCOUNTID>>:domain/<<DOMAIN_NAME>>",
    "arn:aws:es:<<REGION>>:<<ACCOUNTID>>:domain/<<DOMAIN_NAME>>/*"
  ]
},
{
  "Sid": "",
  "Effect": "Allow",
  "Action": [
    "es:ESHttpGet"
  ],
  "Resource": [
    "arn:aws:es:<<REGION>>:<<ACCOUNTID>>:domain/<<DOMAIN_NAME>>/_all/_settings",
    "arn:aws:es:<<REGION>>:<<ACCOUNTID>>:domain/<<DOMAIN_NAME>>/_cluster/stats",
    "arn:aws:es:<<REGION>>:<<ACCOUNTID>>:domain/<<DOMAIN_NAME>>/<<INDEX>>*/_mapping/<<TYPE>>",
    "arn:aws:es:<<REGION>>:<<ACCOUNTID>>:domain/<<DOMAIN_NAME>>/_nodes",
    "arn:aws:es:<<REGION>>:<<ACCOUNTID>>:domain/<<DOMAIN_NAME>>/_nodes/stats",
    "arn:aws:es:<<REGION>>:<<ACCOUNTID>>:domain/<<DOMAIN_NAME>>/_nodes/*/stats",
    "arn:aws:es:<<REGION>>:<<ACCOUNTID>>:domain/<<DOMAIN_NAME>>/_stats",
    "arn:aws:es:<<REGION>>:<<ACCOUNTID>>:domain/<<DOMAIN_NAME>>/<<INDEX>>*/_stats"
  ]
}

I think you could more easily condense the above two policy statements into the following:

{
  "Sid": "",
  "Effect": "Allow",
  "Action": [
    "es:DescribeElasticsearchDomain",
    "es:DescribeElasticsearchDomains",
    "es:DescribeElasticsearchDomainConfig",
    "es:ESHttpPost",
    "es:ESHttpGet",
    "es:ESHttpPut"
  ],
  "Resource": [
    "arn:aws:es:<<REGION>>:<<ACCOUNTID>>:domain/<<DOMAIN_NAME>>",
    "arn:aws:es:<<REGION>>:<<ACCOUNTID>>:domain/<<DOMAIN_NAME>>/*"
  ]
}

I managed to piece the above together from the following sources:

https://aws.amazon.com/blogs/security/how-to-control-access-to-your-amazon-elasticsearch-service-domain/

How to access Kibana from Amazon elasticsearch service?

https://forums.aws.amazon.com/thread.jspa?threadID=217149

The only way I know of to do this is to use a resource-based policy or an IAM-based policy on your ES domain. This would restrict access to a particular IAM user or role. However, to make this work you also need to sign your requests to ES using SigV4.

There are libraries that will do this signing for you, for example this one extends the popular Python requests library to sign ElasticSearch requests via SigV4. I believe similar libraries exist for other languages.

Now it's possible from your code with elasticsearch.js. Before you try it, you must install http-aws-es module.

const AWS = require('aws-sdk');
const httpAwsEs = require('http-aws-es');
const elasticsearch = require('elasticsearch');

const client = new elasticsearch.Client({
    host: 'YOUR_ES_HOST',
    connectionClass: httpAwsEs,
    amazonES: {
        region: 'YOUR_ES_REGION',
        credentials: new AWS.EnvironmentCredentials('AWS')
    }
});

// client.search({...})

Of course, before using it, configure access to elasticsearch domain: