refactor: public kernel (#8061)

Rearranging code for readability. No new features or bug fixes were
added.
The gate count of public_kernel_app_logic increases a lot because of
`previous_kernel.verify`, which was commented out before.

noir-projects/noir-protocol-circuits/crates/public-kernel-app-logic-simulated/src/main.nr

@@ -2,5 +2,5 @@ use dep::public_kernel_lib::PublicKernelAppLogicCircuitPrivateInputs;
 use dep::types::PublicKernelCircuitPublicInputs;
 
 unconstrained fn main(input: PublicKernelAppLogicCircuitPrivateInputs) -> pub PublicKernelCircuitPublicInputs {
-    input.public_kernel_app_logic()
+    input.execute()
 }

noir-projects/noir-protocol-circuits/crates/public-kernel-app-logic/src/main.nr

@@ -3,5 +3,5 @@ use dep::types::PublicKernelCircuitPublicInputs;
 
 #[recursive]
 fn main(input: PublicKernelAppLogicCircuitPrivateInputs) -> pub PublicKernelCircuitPublicInputs {
-    input.public_kernel_app_logic()
+    input.execute()
 }

noir-projects/noir-protocol-circuits/crates/public-kernel-lib/src/components/mod.nr

@@ -0,0 +1,4 @@
+mod previous_kernel_validator;
+mod public_call_data_validator;
+mod public_kernel_output_composer;
+mod public_tail_output_composer;

noir-projects/noir-protocol-circuits/crates/public-kernel-lib/src/components/previous_kernel_validator.nr

@@ -0,0 +1,55 @@
+use crate::public_kernel_phase::PublicKernelPhase;
+use dep::types::abis::public_kernel_data::PublicKernelData;
+
+struct PreviousKernelValidator {
+    previous_kernel: PublicKernelData,
+}
+
+impl PreviousKernelValidator {
+    pub fn new(previous_kernel: PublicKernelData) -> Self {
+        PreviousKernelValidator { previous_kernel }
+    }
+
+    pub fn validate_proof<let N: u32>(self, _allowed_indices: [u32; N]) {
+        if !dep::std::runtime::is_unconstrained() {
+            // Recursively verify the tube proof or a previous public kernel proof
+            self.previous_kernel.verify();
+            // TODO(#7410) currently stubbed out until tube vk handled
+            // self.previous_kernel.validate_in_vk_tree(allowed_indices);
+        }
+    }
+
+    pub fn validate_phase(self, phase: u8) {
+        let public_inputs = self.previous_kernel.public_inputs;
+
+        let needs_setup = !public_inputs.end_non_revertible.public_call_stack[0].item.contract_address.is_zero();
+        if phase == PublicKernelPhase.SETUP {
+            assert_eq(needs_setup, true, "Cannot run unnecessary setup circuit");
+        }
+
+        let needs_app_logic = !public_inputs.end.public_call_stack[0].item.contract_address.is_zero();
+        if phase == PublicKernelPhase.APP_LOGIC {
+            assert_eq(needs_setup, false, "Cannot run app logic circuit before setup circuit");
+            assert_eq(needs_app_logic, true, "Cannot run unnecessary app logic circuit");
+        }
+
+        let needs_teardown = !public_inputs.public_teardown_call_stack[0].item.contract_address.is_zero();
+        if phase == PublicKernelPhase.TEARDOWN {
+            assert_eq(needs_setup, false, "Cannot run teardown circuit before setup circuit");
+            assert_eq(needs_app_logic, false, "Cannot run teardown circuit before app logic circuit");
+            assert_eq(needs_teardown, true, "Cannot run unnecessary teardown circuit");
+        }
+
+        if phase == PublicKernelPhase.TAIL {
+            assert_eq(
+                needs_setup, false, "Revertible call stack must be empty when executing the tail circuit"
+            );
+            assert_eq(
+                needs_app_logic, false, "Non-revertible call stack must be empty when executing the tail circuit"
+            );
+            assert_eq(
+                needs_teardown, false, "Teardown call stack must be empty when executing the tail circuit"
+            );
+        }
+    }
+}

noir-projects/noir-protocol-circuits/crates/public-kernel-lib/src/components/public_call_data_validator.nr

@@ -0,0 +1,187 @@
+use crate::public_kernel_phase::PublicKernelPhase;
+use dep::types::{
+    abis::{
+    kernel_circuit_public_inputs::PublicKernelCircuitPublicInputs, public_call_data::PublicCallData,
+    public_call_request::PublicCallRequest
+},
+    constants::MAX_PUBLIC_CALL_STACK_LENGTH_PER_TX, utils::arrays::array_length
+};
+
+struct PublicCallDataValidator {
+    data: PublicCallData,
+    phase: u8,
+}
+
+impl PublicCallDataValidator {
+    pub fn new(data: PublicCallData, phase: u8) -> Self {
+        PublicCallDataValidator { data, phase }
+    }
+
+    pub fn validate(self) {
+        self.validate_common_inputs();
+        self.validate_revert_code();
+        self.validate_call();
+        self.validate_call_requests();
+    }
+
+    pub fn validate_against_previous_kernel(self, previous_kernel: PublicKernelCircuitPublicInputs) {
+        self.validate_global_variables(previous_kernel);
+        self.validate_start_gas(previous_kernel);
+        self.validate_transaction_fee(previous_kernel);
+        self.validate_against_call_request(previous_kernel);
+    }
+
+    fn validate_common_inputs(self) {
+        let call_stack_item = self.data.call_stack_item;
+        assert(!call_stack_item.contract_address.is_zero(), "Contract address cannot be zero");
+        assert(call_stack_item.function_data.selector.to_field() != 0, "Function signature cannot be zero");
+        assert_eq(
+            call_stack_item.function_data.is_private, false, "Cannot execute a private function with the public kernel circuit"
+        );
+        assert_eq(
+            call_stack_item.function_data.selector, call_stack_item.public_inputs.call_context.function_selector, "function selector in call context does not match call stack item"
+        );
+        assert(self.data.bytecode_hash != 0, "Bytecode hash cannot be zero");
+    }
+
+    fn validate_revert_code(self) {
+        if self.phase == PublicKernelPhase.SETUP {
+            assert_eq(self.data.call_stack_item.public_inputs.revert_code, 0, "Public call cannot be reverted");
+        }
+    }
+
+    fn validate_call(self) {
+        let call_stack_item = self.data.call_stack_item;
+        let public_inputs = call_stack_item.public_inputs;
+
+        let call_context = public_inputs.call_context;
+        if call_context.is_delegate_call {
+            assert(
+                !call_stack_item.contract_address.eq(call_context.storage_contract_address), "curent contract address must not match storage contract address for delegate calls"
+            );
+        } else {
+            assert(
+                call_context.storage_contract_address.eq(call_stack_item.contract_address), "call stack storage address does not match expected contract address"
+            );
+        }
+
+        if call_context.is_static_call {
+            // No state changes are allowed for static calls:
+            let note_hashes_length = array_length(public_inputs.note_hashes);
+            assert(note_hashes_length == 0, "note_hashes must be empty for static calls");
+
+            let nullifiers_length = array_length(public_inputs.nullifiers);
+            assert(nullifiers_length == 0, "nullifiers must be empty for static calls");
+
+            let update_requests_length = array_length(public_inputs.contract_storage_update_requests);
+            assert(
+                update_requests_length == 0, "No contract storage update requests are allowed for static calls"
+            );
+
+            let l2_to_l1_msgs_length = array_length(public_inputs.l2_to_l1_msgs);
+            assert(l2_to_l1_msgs_length == 0, "l2_to_l1_msgs must be empty for static calls");
+
+            let new_unencrypted_logs_length = array_length(public_inputs.unencrypted_logs_hashes);
+            assert(new_unencrypted_logs_length == 0, "No unencrypted logs are allowed for static calls");
+        }
+    }
+
+    fn validate_call_requests(self) {
+        let call_requests = self.data.call_stack_item.public_inputs.public_call_requests;
+        let this_context = self.data.call_stack_item.public_inputs.call_context;
+        for i in 0..call_requests.len() {
+            let request = call_requests[i];
+            if !request.item.contract_address.is_zero() {
+                let target_context = request.item.call_context;
+                let target_contract = request.item.contract_address;
+
+                if target_context.is_delegate_call {
+                    assert_eq(
+                        target_context.msg_sender, this_context.msg_sender, "incorrect msg_sender for delegate call request"
+                    );
+                    assert_eq(
+                        target_context.storage_contract_address, this_context.storage_contract_address, "incorrect storage_contract_address for delegate call request"
+                    );
+                } else {
+                    assert_eq(
+                        target_context.msg_sender, this_context.storage_contract_address, "incorrect msg_sender for call request"
+                    );
+                    assert_eq(
+                        target_context.storage_contract_address, target_contract, "incorrect storage_contract_address for call request"
+                    );
+                }
+                if !target_context.is_static_call {
+                    assert(this_context.is_static_call == false, "static call cannot make non-static calls");
+                }
+            }
+        }
+    }
+
+    fn validate_against_call_request(self, previous_kernel: PublicKernelCircuitPublicInputs) {
+        let call_stack = if self.phase == PublicKernelPhase.SETUP {
+            previous_kernel.end_non_revertible.public_call_stack
+        } else if self.phase == PublicKernelPhase.APP_LOGIC {
+            previous_kernel.end.public_call_stack
+        } else if self.phase == PublicKernelPhase.TEARDOWN {
+            previous_kernel.public_teardown_call_stack
+        } else {
+            assert(false, "Unknown phase");
+            [PublicCallRequest::empty(); MAX_PUBLIC_CALL_STACK_LENGTH_PER_TX]
+        };
+
+        let call_request = call_stack[array_length(call_stack) - 1];
+        assert(
+            self.data.call_stack_item.get_compressed() == call_request.item, "call stack item does not match item at the top of the call stack"
+        );
+    }
+
+    fn validate_global_variables(self, previous_kernel: PublicKernelCircuitPublicInputs) {
+        let prev_global_variables = previous_kernel.constants.global_variables;
+        if !prev_global_variables.is_empty() { // It's empty when the previous kernel is from private_kernel_tail_to_pubic.
+            let public_call_globals = self.data.call_stack_item.public_inputs.global_variables;
+            assert_eq(
+                public_call_globals, prev_global_variables, "Global variables injected into the public call do not match constants"
+            );
+        }
+    }
+
+    // Validates that the start gas injected into the app circuit matches the remaining gas.
+    fn validate_start_gas(self, previous_kernel: PublicKernelCircuitPublicInputs) {
+        // If this is a nested call (not an execution request), the start gas is correct as long as the
+        // call being processed by this kernel iteration matches the call at the top of the callstack
+        // as per the previous kernel's outputs.
+        // An execution request's start gas is the remaining gas left in the transaction after the previous kernel.
+        // A nested call's start gas is the gas allocated to it by its caller and placed in the callstack.
+        if self.data.call_stack_item.is_execution_request {
+            let public_call_start_gas = self.data.call_stack_item.public_inputs.start_gas_left;
+            if self.phase != PublicKernelPhase.TEARDOWN {
+                let tx_gas_limits = previous_kernel.constants.tx_context.gas_settings.gas_limits;
+                let computed_start_gas = tx_gas_limits.sub(previous_kernel.end.gas_used).sub(previous_kernel.end_non_revertible.gas_used);
+                assert_eq(
+                    public_call_start_gas, computed_start_gas, "Start gas for public phase does not match transaction gas left"
+                );
+            } else {
+                let teardown_gas_limit = previous_kernel.constants.tx_context.gas_settings.teardown_gas_limits;
+                assert_eq(
+                    public_call_start_gas, teardown_gas_limit, "Start gas for teardown phase does not match teardown gas allocation"
+                );
+            }
+        }
+    }
+
+    fn validate_transaction_fee(self, previous_kernel: PublicKernelCircuitPublicInputs) {
+        let transaction_fee = self.data.call_stack_item.public_inputs.transaction_fee;
+        if self.phase != PublicKernelPhase.TEARDOWN {
+            assert_eq(transaction_fee, 0, "Transaction fee must be zero on setup and app phases");
+        } else {
+            // Note that teardown_gas is already included in end.gas_used as it was injected by the private kernel
+            let total_gas_used = previous_kernel.end.gas_used + previous_kernel.end_non_revertible.gas_used;
+            let block_gas_fees = self.data.call_stack_item.public_inputs.global_variables.gas_fees;
+            let inclusion_fee = previous_kernel.constants.tx_context.gas_settings.inclusion_fee;
+            let computed_transaction_fee = total_gas_used.compute_fee(block_gas_fees) + inclusion_fee;
+            assert(
+                transaction_fee == computed_transaction_fee, "Transaction fee on teardown phase does not match expected value"
+            );
+        }
+    }
+}