From 7a6f503161f91b0d5b952f410ff5d1ce92b6a682 Mon Sep 17 00:00:00 2001
From: Richard Knoll <richard@rknoll.at>
Date: Sat, 28 Aug 2021 14:28:06 +0100
Subject: [PATCH] Fix PAC/Stanley checksum calculation

The parity bit needs to be discarded when calculating the final
checksum byte value of PAC/Stanley card IDs. Verified by scanning
a tag which is now correctly identified.
---
 client/src/cmdlfpac.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/client/src/cmdlfpac.c b/client/src/cmdlfpac.c
index b751b2af3..f1891cfc1 100644
--- a/client/src/cmdlfpac.c
+++ b/client/src/cmdlfpac.c
@@ -54,7 +54,7 @@ static int pac_buf_to_cardid(uint8_t *src, const size_t src_size, uint8_t *dst,
             PrintAndLogEx(DEBUG, "DEBUG: Error - PAC: Parity check failed");
             return PM3_ESOFT;
         }
-        if (idx < dataLength - 1) checksum ^= byte;
+        if (idx < dataLength - 1) checksum ^= dst[idx];
     }
     if (dst[dataLength - 1] != checksum) {
         PrintAndLogEx(DEBUG, "DEBUG: Error - PAC: Bad checksum - expected: %02X, actual: %02X", dst[dataLength - 1], checksum);