Validate privateFrom before executing private transaction

[MadelineMurray]

As a member of a privacy group, I only want to execute private transactions sent from a member of the privacy group. To ensure a non-member isn't sending a transaction with a privateFrom of an actual member, I need to check the sender (ie, the privateFrom) is who they say they are.

Options to consider:

1. Validate the privateFrom in Orion -> drawback of adding logic to Orion
2. Have Orion pass the public key, that was used to decrypt the private Tx, back with the private transaction so Besu can validate the privateFrom
3. Option we haven't thought of yet

We're going with Option 2.

This change was made in #317 and then reverted in #318 because older versions of Besu did not allow the additional value.

So before re-instating we need to resolve how we're going to handle versioning - do we allow users to update Orion only? Can we expect users of Besu to use a certain version of Orion?

[MadelineMurray]

Are we going to enforce specific versions being used together.

API to get version.

Consider failing on startup if it's not the right version.

[MadelineMurray]

Need to include after last 1.4.x release but before 1.5 RC.

[lucassaldanha]

Here are three scenarios:

Scenario 1: Besu 1.5+ connected to an incompatible Orion version (< 1.6)

• Besu WARN log message: Missing sender key from Orion response. Upgrade Orion to 1.6 to enforce privateFrom check.
• Consequence: Node stops syncing with network
• How to fix: Upgrade Orion to 1.6+ and Besu should be back syncing the network

Scenario 2: Besu 1.5+ (and Orion 1.6+) processing transaction with invalid privateFrom (not matching payload sender key)

• Besu WARN log message: Private transaction privateFrom doesn't match payload sender key
• Consequence: private tx fails (result = 0). PMT is processed successfully)
• How to fix: Don't send payloads with invalid privateFrom :)

Scenario 3: Besu 1.5+ (and Orion 1.6+) processing transaction with invalid RLP (not containing privateFrom)

• Besu WARN log message: Private transaction is missing privateFrom
• Consequence: private tx fails (result = 0). PMT is processed successfully)
• How to fix: Don't send payloads with invalid tx RLP :)

[lucassaldanha]

Both PRs are ready. Now we just need to wait for the right time to merge it!

Orion: #374
Besu: hyperledger/besu#976

[MadelineMurray]

Now is the time for merging!