From ae08aff812fbd205a78354a0dcd31f7fe850670d Mon Sep 17 00:00:00 2001
From: Tomas Fabrizio Orsi <tomas.orsi@lambdaclass.com>
Date: Thu, 26 Dec 2024 14:44:33 -0300
Subject: [PATCH] fix(levm): move insufficient max fee per blob gas check in
 `prepare_execution` (#1564)

**Motivation**

Currently we are charging the sender the entire upfront cost, even when
there are not enough funds to pay for the provided amount of blobhashes.
This returns a `TxValidation` error of type `InsufficientAccountFunds`,
when in reality the error we should be raising is
`InsufficientMaxFeePerBlobGas`.


**Description**

This patch moves the insufficient max fee per blob gas check up. Now,
before the user is charged with the entire `upfront cost`, it is checked
if the provided max fee per blob gas will cover the blobhash cost. If
not, we return a `InsufficientMaxFeePerBlobGas` error, before even
trying to charge for the upfront cost.
---
 crates/vm/levm/src/vm.rs | 39 +++++++++++++++++++++------------------
 1 file changed, 21 insertions(+), 18 deletions(-)

diff --git a/crates/vm/levm/src/vm.rs b/crates/vm/levm/src/vm.rs
index 846d98a05..e713080b0 100644
--- a/crates/vm/levm/src/vm.rs
+++ b/crates/vm/levm/src/vm.rs
@@ -711,6 +711,15 @@ impl VM {
 
         let blob_gas_cost = self.get_blob_gas_price()?;
 
+        // (2) INSUFFICIENT_MAX_FEE_PER_BLOB_GAS
+        if let Some(tx_max_fee_per_blob_gas) = self.env.tx_max_fee_per_blob_gas {
+            if tx_max_fee_per_blob_gas < self.get_base_fee_per_blob_gas()? {
+                return Err(VMError::TxValidation(
+                    TxValidationError::InsufficientMaxFeePerBlobGas,
+                ));
+            }
+        }
+
         // The real cost to deduct is calculated as effective_gas_price * gas_limit + value + blob_gas_cost
         let up_front_cost = gaslimit_price_product
             .checked_add(value)
@@ -721,9 +730,12 @@ impl VM {
             .ok_or(VMError::TxValidation(
                 TxValidationError::InsufficientAccountFunds,
             ))?;
-        // There is no error specified for overflow in up_front_cost in ef_tests. Maybe we can go with GasLimitPriceProductOverflow or InsufficientAccountFunds.
+        // There is no error specified for overflow in up_front_cost
+        // in ef_tests. We went for "InsufficientAccountFunds" simply
+        // because if the upfront cost is bigger than U256, then,
+        // technically, the sender will not be able to pay it.
 
-        // (2) INSUFFICIENT_ACCOUNT_FUNDS
+        // (3) INSUFFICIENT_ACCOUNT_FUNDS
         self.decrease_account_balance(sender_address, up_front_cost)
             .map_err(|_| TxValidationError::InsufficientAccountFunds)?;
 
@@ -734,14 +746,14 @@ impl VM {
             self.increase_account_balance(receiver_address, initial_call_frame.msg_value)?;
         }
 
-        // (3) INSUFFICIENT_MAX_FEE_PER_GAS
+        // (4) INSUFFICIENT_MAX_FEE_PER_GAS
         if self.env.tx_max_fee_per_gas.unwrap_or(self.env.gas_price) < self.env.base_fee_per_gas {
             return Err(VMError::TxValidation(
                 TxValidationError::InsufficientMaxFeePerGas,
             ));
         }
 
-        // (4) INITCODE_SIZE_EXCEEDED
+        // (5) INITCODE_SIZE_EXCEEDED
         if self.is_create() {
             // INITCODE_SIZE_EXCEEDED
             if initial_call_frame.calldata.len() > INIT_CODE_MAX_SIZE {
@@ -751,14 +763,14 @@ impl VM {
             }
         }
 
-        // (5) INTRINSIC_GAS_TOO_LOW
+        // (6) INTRINSIC_GAS_TOO_LOW
         self.add_intrinsic_gas(initial_call_frame)?;
 
-        // (6) NONCE_IS_MAX
+        // (7) NONCE_IS_MAX
         self.increment_account_nonce(sender_address)
             .map_err(|_| VMError::TxValidation(TxValidationError::NonceIsMax))?;
 
-        // (7) PRIORITY_GREATER_THAN_MAX_FEE_PER_GAS
+        // (8) PRIORITY_GREATER_THAN_MAX_FEE_PER_GAS
         if let (Some(tx_max_priority_fee), Some(tx_max_fee_per_gas)) = (
             self.env.tx_max_priority_fee_per_gas,
             self.env.tx_max_fee_per_gas,
@@ -770,27 +782,18 @@ impl VM {
             }
         }
 
-        // (8) SENDER_NOT_EOA
+        // (9) SENDER_NOT_EOA
         if sender_account.has_code() {
             return Err(VMError::TxValidation(TxValidationError::SenderNotEOA));
         }
 
-        // (9) GAS_ALLOWANCE_EXCEEDED
+        // (10) GAS_ALLOWANCE_EXCEEDED
         if self.env.gas_limit > self.env.block_gas_limit {
             return Err(VMError::TxValidation(
                 TxValidationError::GasAllowanceExceeded,
             ));
         }
 
-        // (10) INSUFFICIENT_MAX_FEE_PER_BLOB_GAS
-        if let Some(tx_max_fee_per_blob_gas) = self.env.tx_max_fee_per_blob_gas {
-            if tx_max_fee_per_blob_gas < self.get_base_fee_per_blob_gas()? {
-                return Err(VMError::TxValidation(
-                    TxValidationError::InsufficientMaxFeePerBlobGas,
-                ));
-            }
-        }
-
         // Transaction is type 3 if tx_max_fee_per_blob_gas is Some
         if self.env.tx_max_fee_per_blob_gas.is_some() {
             let blob_hashes = &self.env.tx_blob_hashes;