DynamoDB local http://localhost:8000/shell
Solution 1:
This appears to be a bug in new versions DynamoDB Local, but I couldn't find any documentation about it being deliberate, so please try reporting it to Amazon...
I just checked version 1.13.5 from 2020-10-13, and the "/shell" works as expected and documented. But on version 1.18.0 from 2022-1-10, it doesn't - and reports the same error you listed:
HTTP/1.1 400 Bad Request
Date: Thu, 13 Jan 2022 08:06:18 GMT
Content-Type: application/x-amz-json-1.0
x-amzn-RequestId: 4f040110-4464-48dc-99c1-9b843c25db5f
Content-Length: 173
Server: Jetty(9.4.18.v20190429)
{"__type":"com.amazonaws.dynamodb.v20120810#MissingAuthenticationToken","Message":"Request must contain either a valid (registered) AWS access key ID or X.509 certificate."}
The release notes in DynamoDB Local doesn't mention anything about the shell being deliberately disabled.
You are not the first person to notice this problem - see also this question from two weeks ago: Dynamodb local web shell does not load