ignore offset, replace whole value of attr in auth callback

Author: paul-szczepanek-arm

connectivity/FEATURE_BLE/include/ble/gatt/GattCharacteristic.h

@@ -1692,6 +1692,10 @@ class GattCharacteristic {
      * @note The params->len parameter initially contains the maximum length of
      * data that can be returned. Set it to the length of your data but it must
      * not be larger than the original value.
+     *
+     * @note You must also take into account the offset provided in params->offset.
+     * The params->len you provide must be larger then the offset as the read operation
+     * will attempt to read at that offset.
      */
     GattAuthCallbackReply_t authorizeRead(GattReadAuthCallbackParams *params)
     {

connectivity/FEATURE_BLE/source/cordio/source/GattServerImpl.cpp

@@ -1148,8 +1148,9 @@ uint8_t GattServer::atts_read_cb(
 
         /* if new data provided copy into the attribute value buffer */
         if (read_auth_params.data) {
-            if (read_auth_params.offset + read_auth_params.len > pAttr->maxLen) {
-                tr_error("Read authorisation callback set length larger than maximum attribute length. Cannot copy data");
+            if (read_auth_params.len > pAttr->maxLen || offset >= read_auth_params.len) {
+                tr_error("Read authorisation callback set length larger than maximum attribute length "
+                         "or current offset is beyond new length. Cannot copy data");
 
                 GattReadCallbackParams read_params = {
                     connId,
@@ -1164,7 +1165,7 @@ uint8_t GattServer::atts_read_cb(
                 return ATT_ERR_UNLIKELY;
             }
 
-            memcpy(pAttr->pValue + read_auth_params.offset, read_auth_params.data, read_auth_params.len);
+            memcpy(pAttr->pValue, read_auth_params.data, read_auth_params.len);
             *pAttr->pLen = read_auth_params.len;
         }
     }