Pool App call budget in group transactions (#2711)

* Add pooling for grouped app calls and add unit tests

* Fix doc errors

* Pool app call budget in ep

* Check if pooledBudget is not nil in budget call

* Fix app call integration test output and minor syntax changes

* Minor change in comment

* Modify some tests to get better coverage

* Refactor tests

* Clean up

* Remove a hardcoded constant

* Add pointer equivalence test

Author: algochoi

config/consensus.go

@@ -108,6 +108,11 @@ type ConsensusParams struct {
 	// each Txn has a MinFee.
 	EnableFeePooling bool
 
+	// EnableAppCostPooling specifies that the sum of fees for application calls
+	// in a group is checked against the sum of the budget for application calls,
+	// rather than check each individual app call is within the budget.
+	EnableAppCostPooling bool
+
 	// RewardUnit specifies the number of MicroAlgos corresponding to one reward
 	// unit.
 	//
@@ -1005,6 +1010,9 @@ func initConsensusProtocols() {
 	// Enable TEAL 5 / AVM 1.0
 	vFuture.LogicSigVersion = 5
 
+	// Enable App calls to pool budget in grouped transactions
+	vFuture.EnableAppCostPooling = true
+
 	Consensus[protocol.ConsensusFuture] = vFuture
 }
 

data/transactions/logic/TEAL_opcodes.md

@@ -47,7 +47,6 @@ Ops have a 'cost' of 1 unless otherwise specified.
 - Pushes: uint64
 - for (data A, signature B, pubkey C) verify the signature of ("ProgData" || program_hash || data) against the pubkey => {0 or 1}
 - **Cost**: 1900
-- Mode: Signature
 
 The 32 byte public key is the last element on the stack, preceded by the 64 byte signature at the second-to-last element on the stack, preceded by the data which was signed at the third-to-last element on the stack.
 

data/transactions/logic/eval.go

@@ -224,6 +224,9 @@ type EvalParams struct {
 
 	// determines eval mode: runModeSignature or runModeApplication
 	runModeFlags runMode
+
+	// Total pool of app call budget in a group transaction
+	PooledApplicationBudget *uint64
 }
 
 type opEvalFunc func(cx *evalContext)
@@ -263,6 +266,9 @@ func (ep EvalParams) budget() int {
 	if ep.runModeFlags == runModeSignature {
 		return int(ep.Proto.LogicSigMaxCost)
 	}
+	if ep.Proto.EnableAppCostPooling && ep.PooledApplicationBudget != nil {
+		return int(*ep.PooledApplicationBudget)
+	}
 	return ep.Proto.MaxAppProgramCost
 }
 
@@ -365,6 +371,10 @@ func EvalStateful(program []byte, params EvalParams) (pass bool, err error) {
 	cx.EvalParams = params
 	cx.runModeFlags = runModeApplication
 	pass, err = eval(program, &cx)
+	if cx.EvalParams.Proto.EnableAppCostPooling && cx.EvalParams.PooledApplicationBudget != nil {
+		// if eval passes, then budget is always greater than cost, so should not have underflow
+		*cx.EvalParams.PooledApplicationBudget = basics.SubSaturate(*cx.EvalParams.PooledApplicationBudget, uint64(cx.cost))
+	}
 
 	// set side effects
 	cx.PastSideEffects[cx.GroupIndex].setScratchSpace(cx.scratch)
@@ -640,7 +650,8 @@ func (cx *evalContext) step() {
 	}
 	cx.cost += deets.Cost
 	if cx.cost > cx.budget() {
-		cx.err = fmt.Errorf("pc=%3d dynamic cost budget of %d exceeded, executing %s", cx.pc, cx.budget(), spec.Name)
+		cx.err = fmt.Errorf("pc=%3d dynamic cost budget exceeded, executing %s: remaining budget is %d but program cost was %d",
+			cx.pc, spec.Name, cx.budget(), cx.cost)
 		return
 	}
 

data/transactions/logic/evalStateful_test.go

@@ -697,15 +697,33 @@ log
 		})
 	}
 
-	// check ed25519verify and arg are not allowed in statefull mode
-	disallowed := []string{
+	// check that ed25519verify and arg is not allowed in stateful mode between v2-v4
+	disallowedV4 := []string{
 		"byte 0x01\nbyte 0x01\nbyte 0x01\ned25519verify",
 		"arg 0",
 		"arg_0",
 		"arg_1",
 		"arg_2",
 		"arg_3",
 	}
+	for _, source := range disallowedV4 {
+		ops := testProg(t, source, 4)
+		ep := defaultEvalParams(nil, nil)
+		err := CheckStateful(ops.Program, ep)
+		require.Error(t, err)
+		_, err = EvalStateful(ops.Program, ep)
+		require.Error(t, err)
+		require.Contains(t, err.Error(), "not allowed in current mode")
+	}
+
+	// check that arg is not allowed in stateful mode beyond v5
+	disallowed := []string{
+		"arg 0",
+		"arg_0",
+		"arg_1",
+		"arg_2",
+		"arg_3",
+	}
 	for _, source := range disallowed {
 		ops := testProg(t, source, AssemblerMaxVersion)
 		ep := defaultEvalParams(nil, nil)
@@ -2929,3 +2947,29 @@ bnz loop
 	require.Empty(t, delta.LocalDeltas)
 	require.Len(t, delta.Logs, 29)
 }
+
+func TestPooledAppCallsVerifyOp(t *testing.T) {
+	partitiontest.PartitionTest(t)
+	t.Parallel()
+
+	source := `#pragma version 5
+	global CurrentApplicationID
+	pop
+	byte 0x01
+	byte "ZC9KNzlnWTlKZ1pwSkNzQXVzYjNBcG1xTU9YbkRNWUtIQXNKYVk2RzRBdExPakQx"
+	addr DROUIZXGT3WFJR3QYVZWTR5OJJXJCMOLS7G4FUGZDSJM5PNOVOREH6HIZE
+	ed25519verify
+	pop
+	int 1`
+
+	ep, _ := makeSampleEnv()
+	ep.Proto.EnableAppCostPooling = true
+	ep.PooledApplicationBudget = new(uint64)
+	// Simulate test with 2 grouped txn
+	*ep.PooledApplicationBudget = uint64(ep.Proto.MaxAppProgramCost * 2)
+	testApp(t, source, ep, "pc=107 dynamic cost budget exceeded, executing ed25519verify: remaining budget is 1400 but program cost was 1905")
+
+	// Simulate test with 3 grouped txn
+	*ep.PooledApplicationBudget = uint64(ep.Proto.MaxAppProgramCost * 3)
+	testApp(t, source, ep)
+}

data/transactions/logic/opcodes.go

@@ -142,6 +142,7 @@ var OpSpecs = []OpSpec{
 	{0x03, "sha512_256", opSHA512_256, asmDefault, disDefault, oneBytes, oneBytes, 2, modeAny, costly(45)},
 
 	{0x04, "ed25519verify", opEd25519verify, asmDefault, disDefault, threeBytes, oneInt, 1, runModeSignature, costly(1900)},
+	{0x04, "ed25519verify", opEd25519verify, asmDefault, disDefault, threeBytes, oneInt, 5, modeAny, costly(1900)},
 	{0x08, "+", opPlus, asmDefault, disDefault, twoInts, oneInt, 1, modeAny, opDefault},
 	{0x09, "-", opMinus, asmDefault, disDefault, twoInts, oneInt, 1, modeAny, opDefault},
 	{0x0a, "/", opDiv, asmDefault, disDefault, twoInts, oneInt, 1, modeAny, opDefault},

ledger/apply/application_test.go

@@ -242,6 +242,7 @@ func (b *testBalancesPass) Put(addr basics.Address, ad basics.AccountData) error
 func (b *testBalancesPass) ConsensusParams() config.ConsensusParams {
 	return b.proto
 }
+
 func (b *testBalancesPass) Allocate(addr basics.Address, aidx basics.AppIndex, global bool, space basics.StateSchema) error {
 	b.allocatedAppIdx = aidx
 	return nil

ledger/eval.go

@@ -672,12 +672,18 @@ func (eval *BlockEvaluator) prepareEvalParams(txgroup []transactions.SignedTxnWi
 	var groupNoAD []transactions.SignedTxn
 	var pastSideEffects []logic.EvalSideEffects
 	var minTealVersion uint64
+	pooledApplicationBudget := uint64(0)
 	res = make([]*logic.EvalParams, len(txgroup))
 	for i, txn := range txgroup {
 		// Ignore any non-ApplicationCall transactions
 		if txn.SignedTxn.Txn.Type != protocol.ApplicationCallTx {
 			continue
 		}
+		if eval.proto.EnableAppCostPooling {
+			pooledApplicationBudget += uint64(eval.proto.MaxAppProgramCost)
+		} else {
+			pooledApplicationBudget = uint64(eval.proto.MaxAppProgramCost)
+		}
 
 		// Initialize side effects and group without ApplyData lazily
 		if groupNoAD == nil {
@@ -690,12 +696,13 @@ func (eval *BlockEvaluator) prepareEvalParams(txgroup []transactions.SignedTxnWi
 		}
 
 		res[i] = &logic.EvalParams{
-			Txn:             &groupNoAD[i],
-			Proto:           &eval.proto,
-			TxnGroup:        groupNoAD,
-			GroupIndex:      i,
-			PastSideEffects: pastSideEffects,
-			MinTealVersion:  &minTealVersion,
+			Txn:                     &groupNoAD[i],
+			Proto:                   &eval.proto,
+			TxnGroup:                groupNoAD,
+			GroupIndex:              i,
+			PastSideEffects:         pastSideEffects,
+			MinTealVersion:          &minTealVersion,
+			PooledApplicationBudget: &pooledApplicationBudget,
 		}
 	}
 	return