modify boot.img to enable debug usb and adb

[fightforge]

Hi,
i'm trying to access my a5 sm-a520fn using adb not working even in recovery mode.
I try to mod a boot.img and flash with odin and now i can see devices when i run adb devices but i get unauthorized so i cannot adb shell.

Is there a way to copy adbkey.pub in boot.img?

thanks