eip1559 gadget: constrain gas_fee_cap >= base_fee (#1120)

* add gas_fee_cap_lt_base_fee

* fix fmt

* increase STEP_WIDTH &N_BYTE_LOOKUPS as more byte cells required

* revise comment

* increase STEP_WIDTH: scroll feature needs more cells

* add new constraint to doc

docs/EIP2930_1559.md

@@ -45,10 +45,12 @@ this doc describles how to support EIP2930 & 1559 in copy circuit and evm circui
       - `gas_tip_cap`: MaxPriorityFeePerGas in 1559.
       - `mul_gas_fee_cap_by_gas`: Calculates total gas amount.
       - `balance_check`: Calculates minimal caller's balance required = `mul_gas_fee_cap_by_gas` + `tx.value` + `tx_l1_fee`.
-      - is_insufficient_balance: check balance is sufficient compared to 
+      - `is_insufficient_balance`: check balance is sufficient compared to 
       minimal balance required.
-      - gas_fee_cap_lt_gas_tip_cap: make sure gas_fee_cap not less than gas_tip_gap.
+      - `gas_fee_cap_lt_gas_tip_cap`: make sure gas_fee_cap not less than gas_tip_gap.
+      - `base_fee`: base fee from block context.
+      - `gas_fee_cap_lt_base_fee`: make sure gas_fee_cap not less than base fee.
     - constraints:
       - tx table lookups for [MaxFeePerGas, MaxPriorityFeePerGas]
-      - sender balance must be sufficient, means gas_fee_cap >= gas_tip_cap
+      - sender balance must be sufficient, as well as gas_fee_cap >= gas_tip_cap, gas_fee_cap >= base_fee.
    - `begin_tx` : take use of `TxAccessListGadget` and `TxEip1559Gadget` to implement corresponding constraints. 

zkevm-circuits/src/evm_circuit/execution/begin_tx.rs

@@ -1223,7 +1223,13 @@ impl<F: Field> ExecutionGadget<F> for BeginTxGadget<F> {
         )?;
 
         self.tx_access_list.assign(region, offset, tx)?;
-
+        // get base_fee from block context
+        let base_fee = block
+            .context
+            .ctxs
+            .get(&tx.block_number)
+            .expect("cound not find block with number = {tx.block_number}")
+            .base_fee;
         self.tx_eip1559.assign(
             region,
             offset,
@@ -1233,6 +1239,7 @@ impl<F: Field> ExecutionGadget<F> for BeginTxGadget<F> {
                 .sender_balance_sub_fee_pair
                 .unwrap()
                 .1,
+            base_fee,
         )
     }
 }

zkevm-circuits/src/evm_circuit/param.rs

@@ -7,7 +7,7 @@ use halo2_proofs::{
 use std::{collections::HashMap, sync::LazyLock};
 
 // Step dimension
-pub(crate) const STEP_WIDTH: usize = 141;
+pub(crate) const STEP_WIDTH: usize = 144;
 /// Step height
 pub const MAX_STEP_HEIGHT: usize = 21;
 /// The height of the state of a step, used by gates that connect two
@@ -27,7 +27,7 @@ pub(crate) const N_COPY_COLUMNS: usize = 2;
 // Number of copy columns for phase2
 pub(crate) const N_PHASE2_COPY_COLUMNS: usize = 1;
 
-pub(crate) const N_BYTE_LOOKUPS: usize = 36;
+pub(crate) const N_BYTE_LOOKUPS: usize = 39;
 
 /// Amount of lookup columns in the EVM circuit dedicated to lookups.
 pub(crate) const EVM_LOOKUP_COLS: usize = FIXED_TABLE_LOOKUPS

zkevm-circuits/src/evm_circuit/util/common_gadget/tx_eip1559.rs

@@ -14,7 +14,7 @@ use crate::{
         },
         witness::Transaction,
     },
-    table::TxFieldTag,
+    table::{BlockContextFieldTag, TxFieldTag},
 };
 use eth_types::{geth_types::TxType, Field, ToLittleEndian, U256};
 use halo2_proofs::plonk::{Error, Expression};
@@ -30,11 +30,16 @@ pub(crate) struct TxEip1559Gadget<F> {
     mul_gas_fee_cap_by_gas: MulWordByU64Gadget<F>,
     balance_check: AddWordsGadget<F, 3, true>,
     // Error condition
-    // <https://github.com/ethereum/go-ethereum/blob/master/core/state_transition.go#L255>
+    // <https://github.com/ethereum/go-ethereum/blob/master/core/state_transition.go#L241>
     is_insufficient_balance: LtWordGadget<F>,
     // Error condition
     // <https://github.com/ethereum/go-ethereum/blob/master/core/state_transition.go#L310>
     gas_fee_cap_lt_gas_tip_cap: LtWordGadget<F>,
+    // base fee from block context
+    base_fee: Word<F>,
+    // Error condition
+    // <https://github.com/ethereum/go-ethereum/blob/master/core/state_transition.go#L316>
+    gas_fee_cap_lt_base_fee: LtWordGadget<F>,
 }
 
 impl<F: Field> TxEip1559Gadget<F> {
@@ -58,6 +63,8 @@ impl<F: Field> TxEip1559Gadget<F> {
             balance_check,
             is_insufficient_balance,
             gas_fee_cap_lt_gas_tip_cap,
+            base_fee,
+            gas_fee_cap_lt_base_fee,
         ) = cb.condition(is_eip1559_tx.expr(), |cb| {
             let mul_gas_fee_cap_by_gas =
                 MulWordByU64Gadget::construct(cb, gas_fee_cap.clone(), tx_gas);
@@ -76,12 +83,19 @@ impl<F: Field> TxEip1559Gadget<F> {
             let is_insufficient_balance = LtWordGadget::construct(cb, sender_balance, &min_balance);
             let gas_fee_cap_lt_gas_tip_cap =
                 LtWordGadget::construct(cb, &gas_fee_cap, &gas_tip_cap);
+            // lookup base fee from block.
+            let base_fee = cb.query_word_rlc();
+            cb.block_lookup(BlockContextFieldTag::BaseFee.expr(), cb.curr.state.block_number.expr(), base_fee.expr());
+            // constrain GasFeeCap not less than BaseFee
+            let gas_fee_cap_lt_base_fee =
+                LtWordGadget::construct(cb, &gas_fee_cap, &base_fee);
 
             cb.require_zero(
-                "Sender balance must be sufficient, and gas_fee_cap >= gas_tip_cap",
+                "Sender balance must be sufficient, and gas_fee_cap >= gas_tip_cap, and gas_fee_cap >= base_fee",
                 sum::expr([
                     is_insufficient_balance.expr(),
                     gas_fee_cap_lt_gas_tip_cap.expr(),
+                    gas_fee_cap_lt_base_fee.expr(),
                 ]),
             );
 
@@ -90,6 +104,8 @@ impl<F: Field> TxEip1559Gadget<F> {
                 balance_check,
                 is_insufficient_balance,
                 gas_fee_cap_lt_gas_tip_cap,
+                base_fee,
+                gas_fee_cap_lt_base_fee,
             )
         });
 
@@ -101,6 +117,8 @@ impl<F: Field> TxEip1559Gadget<F> {
             balance_check,
             is_insufficient_balance,
             gas_fee_cap_lt_gas_tip_cap,
+            base_fee,
+            gas_fee_cap_lt_base_fee,
         }
     }
 
@@ -111,6 +129,7 @@ impl<F: Field> TxEip1559Gadget<F> {
         tx: &Transaction,
         tx_l1_fee: U256,
         sender_balance_prev: U256,
+        base_fee: U256,
     ) -> Result<(), Error> {
         self.is_eip1559_tx.assign(
             region,
@@ -142,12 +161,16 @@ impl<F: Field> TxEip1559Gadget<F> {
         )?;
         self.is_insufficient_balance
             .assign(region, offset, sender_balance_prev, min_balance)?;
+        self.base_fee
+            .assign(region, offset, Some(base_fee.to_le_bytes()))?;
         self.gas_fee_cap_lt_gas_tip_cap.assign(
             region,
             offset,
             tx.max_fee_per_gas,
             tx.max_priority_fee_per_gas,
-        )
+        )?;
+        self.gas_fee_cap_lt_base_fee
+            .assign(region, offset, tx.max_fee_per_gas, base_fee)
     }
 }