fix modexp input (#1099)

Author: noel2004

bus-mapping/src/precompile.rs

@@ -287,8 +287,11 @@ impl ModExpAuxData {
     /// Create a new instance of modexp auxiliary data.
     pub fn new(input: &[u8], output: &[u8], return_bytes: &[u8]) -> Self {
         let mut resized_input = input.to_vec();
+        if resized_input.len() < 96 {
+            resized_input.resize(96, 0);
+        }
 
-        let (input_valid, [base_len, exp_len, modulus_len]) = Self::check_input(input);
+        let (input_valid, [base_len, exp_len, modulus_len]) = Self::check_input(&resized_input);
 
         let base_mem_len = if input_valid { base_len.as_usize() } else { 0 };
         let exp_mem_len = if input_valid { exp_len.as_usize() } else { 0 };

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

@@ -1622,6 +1622,27 @@ mod test {
         CircuitTestBuilder::new_from_test_ctx(ctx).run();
     }
 
+    /// from failed testtool case
+    #[test]
+    fn begin_tx_precompile_fail_modexp() {
+        let ctx = TestContext::<1, 1>::new(
+            None,
+            |accs| {
+                accs[0].address(MOCK_ACCOUNTS[0]).balance(eth(20));
+            },
+            |mut txs, accs| {
+                txs[0]
+                    .from(accs[0].address)
+                    .to(address!("0x0000000000000000000000000000000000000005"))
+                    .input(Bytes::from_str("0x00000000008000000000000000000000000000000000000000000000000000000000000400000000000000000000000a").unwrap());
+            },
+            |block, _tx| block.number(0xcafeu64),
+        )
+        .unwrap();
+
+        CircuitTestBuilder::new_from_test_ctx(ctx).run();
+    }
+
     /// testool case EmptyTransaction3_d0_g0_v0
     #[test]
     fn begin_tx_create_empty_tx() {

zkevm-circuits/src/evm_circuit/execution/precompiles/modexp.rs

@@ -825,7 +825,7 @@ impl<F: Field> ExecutionGadget<F> for ModExpGadget<F> {
             cb.curr.state.gas_left.expr(),
         );
 
-        let required_input_len = 192.expr();
+        let required_input_len = MODEXP_INPUT_LIMIT.expr();
         let pad_right = LtGadget::construct(cb, call_data_length.expr(), required_input_len.expr());
         let padding = cb.condition(pad_right.expr(), |cb| {
             PaddingGadget::construct(
@@ -1535,6 +1535,26 @@ mod test {
                 gas: 1000.into(),
                 ..Default::default()
             },
+            PrecompileCallArgs {
+                name: "from test tool: zero padding and invalid size",
+                setup_code: bytecode! {
+                    // Base size
+                    PUSH32(word!("0x0000000000800000000000000000000000000000000000000000000000000000"))
+                    PUSH1(0x00)
+                    MSTORE
+                    // Esize
+                    PUSH32(word!("0x000000400000000000000000000000a000000000000000000000000000000000"))
+                    PUSH1(0x20)
+                    MSTORE
+                },
+                call_data_offset: 0x0.into(),
+                call_data_length: 0x30.into(),
+                ret_offset: 0xe0.into(),
+                ret_size: 0x20.into(),
+                address: PrecompileCalls::Modexp.address().to_word(),
+                gas: 100000.into(),
+                ..Default::default()
+            },
         ]
     });