This PR fixes a security issue where an IAM user based
on his policy is granted more privileges than restricted
by the users IAM policy.
This is due to an issue of prefix based Matcher() function
which was incorrectly matching prefix based on resource
prefixes instead of exact match.
This PR supports iam and bucket policies to have
policy variable replacements in resource and
condition key values.
For example
- ${aws:username}
- ${aws:userid}
This PR introduces two new features
- AWS STS compatible STS API named AssumeRoleWithClientGrants
```
POST /?Action=AssumeRoleWithClientGrants&Token=<jwt>
```
This API endpoint returns temporary access credentials, access
tokens signature types supported by this API
- RSA keys
- ECDSA keys
Fetches the required public key from the JWKS endpoints, provides
them as rsa or ecdsa public keys.
- External policy engine support, in this case OPA policy engine
- Credentials are stored on disks
