From 39470aa58742ab60fd12625beb807e4e21f0a0d3 Mon Sep 17 00:00:00 2001
From: Tomas Fabrizio Orsi <tomas.orsi@lambdaclass.com>
Date: Fri, 14 Feb 2025 17:24:10 -0300
Subject: [PATCH] fix(levm): add spurious dragon checks (#1957)

**Motivation**

The EXP instruction's cost changed in Spurious dragon

**Description**

Add a check for its cost.
---
 crates/vm/levm/src/execution_handlers.rs      | 27 ++++++++++---------
 crates/vm/levm/src/gas_cost.rs                | 12 +++++++--
 .../vm/levm/src/opcode_handlers/arithmetic.rs |  2 +-
 3 files changed, 26 insertions(+), 15 deletions(-)

diff --git a/crates/vm/levm/src/execution_handlers.rs b/crates/vm/levm/src/execution_handlers.rs
index d899d2f6d1..8cdc13e5a9 100644
--- a/crates/vm/levm/src/execution_handlers.rs
+++ b/crates/vm/levm/src/execution_handlers.rs
@@ -9,6 +9,8 @@ use crate::{
     vm::{StateBackup, VM},
 };
 
+use ethrex_common::types::Fork;
+
 use bytes::Bytes;
 
 impl VM {
@@ -189,18 +191,19 @@ impl VM {
             // If the first byte of code is 0xef
             // If the code_length > MAX_CODE_SIZE
             // If current_consumed_gas + code_deposit_cost > gas_limit
-            let validate_create = if code_length > MAX_CODE_SIZE {
-                Err(VMError::ContractOutputTooBig)
-            } else if contract_code.first().unwrap_or(&0) == &INVALID_CONTRACT_PREFIX {
-                Err(VMError::InvalidContractPrefix)
-            } else if current_call_frame
-                .increase_consumed_gas(code_deposit_cost)
-                .is_err()
-            {
-                Err(VMError::OutOfGas(OutOfGasError::MaxGasLimitExceeded))
-            } else {
-                Ok(current_call_frame.to)
-            };
+            let validate_create =
+                if code_length > MAX_CODE_SIZE && self.env.config.fork >= Fork::SpuriousDragon {
+                    Err(VMError::ContractOutputTooBig)
+                } else if contract_code.first().unwrap_or(&0) == &INVALID_CONTRACT_PREFIX {
+                    Err(VMError::InvalidContractPrefix)
+                } else if current_call_frame
+                    .increase_consumed_gas(code_deposit_cost)
+                    .is_err()
+                {
+                    Err(VMError::OutOfGas(OutOfGasError::MaxGasLimitExceeded))
+                } else {
+                    Ok(current_call_frame.to)
+                };
 
             match validate_create {
                 Ok(new_address) => {
diff --git a/crates/vm/levm/src/gas_cost.rs b/crates/vm/levm/src/gas_cost.rs
index f25a06f0f0..796fd2f459 100644
--- a/crates/vm/levm/src/gas_cost.rs
+++ b/crates/vm/levm/src/gas_cost.rs
@@ -21,6 +21,7 @@ pub const SMOD: u64 = 5;
 pub const ADDMOD: u64 = 8;
 pub const MULMOD: u64 = 8;
 pub const EXP_STATIC: u64 = 10;
+pub const EXP_DYNAMIC_BASE_PRE_SPURIOUS_DRAGON: u64 = 10;
 pub const EXP_DYNAMIC_BASE: u64 = 50;
 pub const SIGNEXTEND: u64 = 5;
 pub const LT: u64 = 3;
@@ -260,7 +261,7 @@ pub const BLS12_381_G2_K_DISCOUNT: [u64; 128] = [
 ];
 pub const G2_MUL_COST: u64 = 22500;
 
-pub fn exp(exponent: U256) -> Result<u64, VMError> {
+pub fn exp(exponent: U256, fork: Fork) -> Result<u64, VMError> {
     let exponent_byte_size = (exponent
         .bits()
         .checked_add(7)
@@ -271,7 +272,14 @@ pub fn exp(exponent: U256) -> Result<u64, VMError> {
         .try_into()
         .map_err(|_| VMError::VeryLargeNumber)?;
 
-    let exponent_byte_size_cost = EXP_DYNAMIC_BASE
+    // https://eips.ethereum.org/EIPS/eip-160
+    let dynamic_base = if fork < Fork::SpuriousDragon {
+        EXP_DYNAMIC_BASE_PRE_SPURIOUS_DRAGON
+    } else {
+        EXP_DYNAMIC_BASE
+    };
+
+    let exponent_byte_size_cost = dynamic_base
         .checked_mul(exponent_byte_size)
         .ok_or(VMError::OutOfGas(OutOfGasError::GasCostOverflow))?;
 
diff --git a/crates/vm/levm/src/opcode_handlers/arithmetic.rs b/crates/vm/levm/src/opcode_handlers/arithmetic.rs
index d437c2081c..496df89264 100644
--- a/crates/vm/levm/src/opcode_handlers/arithmetic.rs
+++ b/crates/vm/levm/src/opcode_handlers/arithmetic.rs
@@ -221,7 +221,7 @@ impl VM {
         let base = current_call_frame.stack.pop()?;
         let exponent = current_call_frame.stack.pop()?;
 
-        let gas_cost = gas_cost::exp(exponent)?;
+        let gas_cost = gas_cost::exp(exponent, self.env.config.fork)?;
 
         current_call_frame.increase_consumed_gas(gas_cost)?;