registry: Add ProveFreshness consensus layer transaction

[peternose]

Add ProveFreshness consensus layer transaction

This is needed for Client node TEE freshness verification and should be implemented in the following manner.

We can add a (carefully parameter-gated) new transaction (e.g. registry.ProveFreshness) that accepts a fixed-size binary blob of 32 bytes and always succeeds without doing any processing or state changes. It should cost a reasonable amount of gas.

The enablement parameter should be part of the existing tee_features consensus parameter group and be a boolean called freshness_proofs. If it is set to true the new transaction is processed otherwise it is handled as a non-existing transaction (e.g. exactly as currently to avoid breaking consensus before the activation proposal passes).

The existing consensus-tee-pcs migration should be updated to enable the freshness_proofs feature and configure the default gas cost.

Test

Tested locally (sub-command gen_prove_freshness will be added latter to the CLI repository).

oasis-node registry node gen_prove_freshness \
  --transaction.fee.gas 1000 \
  --transaction.fee.amount 0 \
  --transaction.file=tx.txt \
  --genesis.file ../genesis.json \
  --debug.dont_blame_oasis \
  --debug.allow_test_keys \
  --log.level=DEBUG \
  --assume_yes

oasis-node consensus submit_tx --transaction.file tx.txt

If proofs are not enabled, I get the following error.

level=error ts=2022-08-31T06:55:44.773530442Z caller=grpc.go:242 module=grpc/client msg="request failed" method=/oasis-core.Consensus/SubmitTx req_seq=1 rsp=null err="registry: invalid argument"
level=error ts=2022-08-31T06:55:44.773585673Z caller=consensus.go:129 module=cmd/consensus msg="failed to submit transaction" err="registry: invalid argument"

[codecov]

Codecov Report

Merging #4916 (7a87fdb) into master (5a149fc) will increase coverage by 0.09%.
The diff coverage is 71.92%.

@@            Coverage Diff             @@
##           master    #4916      +/-   ##
==========================================
+ Coverage   66.60%   66.69%   +0.09%     
==========================================
  Files         464      464              
  Lines       50981    51028      +47     
==========================================
+ Hits        33955    34033      +78     
+ Misses      12834    12818      -16     
+ Partials     4192     4177      -15     

Impacted Files	Coverage Δ
go/common/node/tee.go	100.00% <ø> (ø)
go/consensus/tendermint/apps/registry/registry.go	61.36% <30.00%> (-2.58%)	⬇️
...consensus/tendermint/apps/registry/transactions.go	54.50% <41.66%> (-0.33%)	⬇️
go/oasis-node/cmd/genesis/genesis.go	53.76% <75.00%> (-0.04%)	⬇️
go/consensus/tendermint/tests/genesis/genesis.go	92.90% <100.00%> (+0.31%)	⬆️
go/genesis/api/api.go	73.91% <100.00%> (ø)
go/registry/api/api.go	57.46% <100.00%> (+0.12%)	⬆️
go/registry/tests/tester.go	92.56% <100.00%> (+0.07%)	⬆️
go/upgrade/migrations/consensus_tee_pcs.go	75.00% <100.00%> (+2.27%)	⬆️
go/worker/keymanager/worker.go	65.31% <100.00%> (+0.21%)	⬆️
... and 37 more

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[kostko]

Mostly looks good, I would just avoid adding the CLI subcommands to oasis-node.