Connect to elasticsearch in AWS using key credentials
This is quite a long rabbit hole. Thanks to Adam for the comment that sent me in the correct direction. The link https://docs.aws.amazon.com/apigateway/api-reference/signing-requests/ really helps you understand what you need to do.
I've since found a script that follows the signing requests method outlined above. It runs in bash and whilst it is not written for use with elasticsearch requests it can be used for them.
https://github.com/riboseinc/aws-authenticating-secgroup-scripts many thanks to https://www.ribose.com for putting this on github.
If your host contains ':443' remove it and try again.This worked for me.
"My initial problem: If I access it with Postman using the same url, I get the same error, but removing the ‘:443/’, it works fine, so it’s nothing wrong with the key and secret I’m using."