Check contract is being called from first input.

sCrypt-Inc · Nov 17, 2023 · 6d96610 · 6d96610
1 parent 66a530e
commit 6d96610
Showing 1 changed file with 8 additions and 0 deletions.
diff --git a/src/contracts/bsv20SellLimitOrder.ts b/src/contracts/bsv20SellLimitOrder.ts
@@ -12,6 +12,8 @@ import {
     assert,
     len,
     toByteString,
+    slice,
+    int2ByteString,
 } from 'scrypt-ts'
 
 /**
@@ -54,6 +56,12 @@ export class BSV20SellLimitOrder extends BSV20V2 {
 
     @method()
     public buy(amount: bigint, buyerAddr: Addr) {
+        // Ensure the contract is being called via the first input of the call tx.
+        const outpoint: ByteString =
+            this.ctx.utxo.outpoint.txid +
+            int2ByteString(this.ctx.utxo.outpoint.outputIndex, 4n)
+        assert(outpoint == slice(this.prevouts, 0n, 36n))
+
         // Check token amount doesn't exceed total.
         assert(
             this.tokenAmtSold + amount < this.tokenAmt,