Codearena findings 12, If liquidity is insufficient, users will need to pay more tokens

Author: af-afk

pkg/seawater/src/error.rs

@@ -241,6 +241,10 @@ pub enum Error {
     // 43 (0x2b)
     #[error("Trying to swap2 between the same pool")]
     SamePool,
+
+    // 44 (0x2c)
+    #[error("Swap sending fee taking overflow")]
+    TransferToSenderSub,
 }
 
 impl From<Error> for Vec<u8> {

pkg/seawater/src/lib.rs

@@ -287,9 +287,18 @@ impl Pools {
         ));
 
         // transfer tokens
-        erc20::take(from, original_amount, permit2)?;
+        erc20::take(from, amount_in, permit2)?;
         erc20::transfer_to_sender(to, amount_out)?;
 
+        if original_amount > amount_in {
+            erc20::transfer_to_sender(
+                to,
+                original_amount
+                    .checked_sub(amount_in)
+                    .ok_or(Error::TransferToSenderSub)?,
+            )?;
+        }
+
         #[cfg(feature = "log-events")]
         evm::log(events::Swap2 {
             user: msg::sender(),