This PR adds pass-through, single encryption at gateway and double
encryption support (gateway encryption with pass through of SSE
headers to backend).
If KMS is set up (either with Vault as KMS or using
MINIO_SSE_MASTER_KEY),gateway will automatically perform
single encryption. If MINIO_GATEWAY_SSE is set up in addition to
Vault KMS, double encryption is performed.When neither KMS nor
MINIO_GATEWAY_SSE is set, do a pass through to backend.
When double encryption is specified, MINIO_GATEWAY_SSE can be set to
"C" for SSE-C encryption at gateway and backend, "S3" for SSE-S3
encryption at gateway/backend or both to support more than one option.
Fixes#6323, #6696
* Refactor HTTP server to address bugs
* Remove unnecessary goroutine to start multiple TCP listeners.
* HTTP server waits for shutdown to maximum of Server.ShutdownTimeout
than per serverShutdownPoll.
* Handles new connection errors properly.
* Handles read and write timeout properly.
* Handles error on start of HTTP server properly by exiting minio
process.
Fixes#4494#4476 & fixed review comments
poornas