[Qt] Payment request expiration bug fix (re-done)

- this is based on #4122 (which can be closed)

Currently a payment request is only checked for expiration upon receipt.
It should be checked again immediately before sending coins to prevent
the user from paying to an expired invoice which would then require a
customer service interaction.

- add static verifyExpired() function to PaymentServer to be able to use
  the same validation code in GUI and unit-testing code
- extend unit tests to use that function and also add an unit test which
  overflows, because payment requests allow expires as uint64, whereas we
  use int64_t for verification of expired payment requests

1 files changed, 2 insertions, 0 deletions

diff --git a/src/qt/paymentserver.h b/src/qt/paymentserver.h
index 9330e9a89c..db5f44ff1d 100644
--- a/src/qt/paymentserver.h
+++ b/src/qt/paymentserver.h
@@ -93,6 +93,8 @@ public:
 
     // Verify that the payment request network matches the client network
     static bool verifyNetwork(const payments::PaymentDetails& requestDetails);
+    // Verify if the payment request is expired
+    static bool verifyExpired(const payments::PaymentDetails& requestDetails);
 
 signals:
     // Fired when a valid payment request is received