Merge pull request #585 from keep-network/a-bit-sale

A Bit Sale - Clear dirty bits FundingScript and RedemptionScript use mload to cast the first bytes of a byte array to bytes4. Because mload deals with 32-byte chunks, the resulting bytes4 value may contain dirty lower-order bits.
keep-network · Apr 21, 2020 · 0f585af · 0f585af
2 parents a5804d5 + 8856fac
commit 0f585af
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Showing 2 changed files with 6 additions and 2 deletions.
diff --git a/solidity/contracts/scripts/FundingScript.sol b/solidity/contracts/scripts/FundingScript.sol
@@ -40,7 +40,9 @@ contract FundingScript {
 
         // Verify _extraData is a call to unqualifiedDepositToTbtc.
         bytes4 functionSignature;
-        assembly { functionSignature := mload(add(_extraData, 0x20)) }
+        assembly {
+            functionSignature := and(mload(add(_extraData, 0x20)), not(0xff))
+        }
         require(
             functionSignature == vendingMachine.unqualifiedDepositToTbtc.selector,
             "Bad _extraData signature. Call must be to unqualifiedDepositToTbtc."

diff --git a/solidity/contracts/scripts/RedemptionScript.sol b/solidity/contracts/scripts/RedemptionScript.sol
@@ -41,7 +41,9 @@ contract RedemptionScript {
 
         // Verify _extraData is a call to tbtcToBtc.
         bytes4 functionSignature;
-        assembly { functionSignature := mload(add(_extraData, 0x20)) }
+        assembly {
+            functionSignature := and(mload(add(_extraData, 0x20)), not(0xff))
+        }
         require(
             functionSignature == vendingMachine.tbtcToBtc.selector,
             "Bad _extraData signature. Call must be to tbtcToBtc."