fix: verify state transition for tap collector thawing signers (TRST-R03)

Signed-off-by: Tomás Migone <[email protected]>

Author: tmigone

packages/horizon/contracts/interfaces/ITAPCollector.sol

@@ -130,6 +130,13 @@ interface ITAPCollector is IPaymentsCollector {
      */
     error TAPCollectorAuthorizationAlreadyRevoked(address payer, address signer);
 
+    /**
+     * Thrown when attempting to thaw a signer that is already thawing
+     * @param signer The address of the signer
+     * @param thawEndTimestamp The timestamp at which the thawing period ends
+     */
+    error TAPCollectorSignerAlreadyThawing(address signer, uint256 thawEndTimestamp);
+
     /**
      * Thrown when the signer is not thawing
      * @param signer The address of the signer

packages/horizon/contracts/payments/collectors/TAPCollector.sol

@@ -82,6 +82,10 @@ contract TAPCollector is EIP712, GraphDirectory, ITAPCollector {
 
         require(authorization.payer == msg.sender, TAPCollectorSignerNotAuthorizedByPayer(msg.sender, signer));
         require(!authorization.revoked, TAPCollectorAuthorizationAlreadyRevoked(msg.sender, signer));
+        require(
+            authorization.thawEndTimestamp == 0,
+            TAPCollectorSignerAlreadyThawing(signer, authorization.thawEndTimestamp)
+        );
 
         authorization.thawEndTimestamp = block.timestamp + REVOKE_SIGNER_THAWING_PERIOD;
         emit SignerThawing(msg.sender, signer, authorization.thawEndTimestamp);
@@ -174,10 +178,7 @@ contract TAPCollector is EIP712, GraphDirectory, ITAPCollector {
 
         // Ensure RAV payer matches the authorized payer
         address payer = authorizedSigners[signer].payer;
-        require(
-            signedRAV.rav.payer == payer,
-            TAPCollectorInvalidRAVPayer(payer, signedRAV.rav.payer)
-        );
+        require(signedRAV.rav.payer == payer, TAPCollectorInvalidRAVPayer(payer, signedRAV.rav.payer));
 
         address dataService = signedRAV.rav.dataService;
         address receiver = signedRAV.rav.serviceProvider;

packages/horizon/test/payments/tap-collector/signer/thawSigner.t.sol

@@ -40,4 +40,17 @@ contract TAPCollectorThawSignerTest is TAPCollectorTest {
         vm.expectRevert(expectedError);
         tapCollector.thawSigner(signer);
     }
+
+    function testTAPCollector_ThawSigner_RevertWhen_AlreadyThawing() public useGateway useSigner {
+        _thawSigner(signer);
+
+        (,uint256 thawEndTimestamp,) = tapCollector.authorizedSigners(signer);
+        bytes memory expectedError = abi.encodeWithSelector(
+            ITAPCollector.TAPCollectorSignerAlreadyThawing.selector,
+            signer,
+            thawEndTimestamp
+        );
+        vm.expectRevert(expectedError);
+        tapCollector.thawSigner(signer);
+    }
 }