Report:

Problem Statement:-

A sample scenario where the tests fire some RPC calls to the two RPC servers ValidationServer and CommitServer. The ValidationServer is responsible for validating the incoming requests. CommitServer simulates the commit of the message.

The task is to ensure that the CommitServer implemented in commit/server/server.go reject any incoming messages that are directly sent to it without validation.

In other words, the commitServer should only respond with CommitResponse_SUCCESS (see protos/master/master.pb.go) if the message received was successfully validated by the validation server.

So a message must be first sent to a validation server, and then to the commit server. Otherwise it must be rejected by the CommitServer.

Things that are not allowed:

1. CommitServer and ValidationServer are not allowed to communicate in any way directly.

2. You are not allowed to modify test/ and protos/ directory.

Solution Approach:

The situation can be handled by taking into account the concept of Public and Private Key-Pair.

As the message needs to be validated first before being requested to be committed. So the commit server should somehow needs to know or verify that if a message is directly coming to it without validation or after proper validation.

So to handle the situation, the validation server can sign the message with its private key, which it receives for validation and the the signature along with msg & msgId can be returned in Validation Response.

After wards, when commit server will receive the request after validation of message, then the request itself has the signature and the original message and commit server can verify it using the public key of the validation server, if the message is actually coming from the validation server. If the verification fails, like in the case of the non-validated message, then the Return Value is FAILURE.

N.B:-

1. Folders 'pkiCommit' and 'pkiValidator' contains the code for key-pair genration and also the already generated key pairs. Ignore the pkiCommit folder because as per my approach, only key pair of validation server is required.
2. The keys are being loaded in 'server.go' of both Validation & Commit Server using an absolute path. So, don't forget to change the paths of the keys of validation server