Is there an 'official' ST bootloader code somewhere

[MikeDB]

I need to write a custom bootloader to monitor USART1 and on receiving a certain command overwriting the following image into its Flash and then rebooting. Are there parts of an official ST bootloader codeset in their libraries ? Otherwise can somebody recommend which of the numerous ones on GitHub is a good place to begin. Devices that need this are STM32F103 and STM32H750. I assume with both I will set the device to execute the bootloader download code in RAM whilst overwriting the Flash. I realise I could do this easier with the JTAG port but I've had to use those pins for other functions.

Many thanks

[Clive1 (HNL)]

ST has published IAP and DFU examples within their code bases over the years.