Hi Tom, On Mon, Mar 02, 2026 at 04:09:37PM -0600, Tom Rini wrote: > There is a flaw in how U-Boot verifies and generates signatures for FIT > images. To prevent mix and match style attacks, it is recommended to > use signed configurations. How this is supposed to work is documented in > doc/usage/fit/signature.rst. > > Crucially, the `hashed-nodes` property of the `signature` node contains > which nodes of the FIT device tree were hashed as part of the signature > and should be verified. However, this property itself is not part of the > hash and can therefore be modified by an attacker. Furthermore, the > signature only contains the name of each node and not the path in the > device tree to the node. > > This patch reworks the code to address this specific oversight.
As this breaks compatibility between old U-Boot and new FIT images and the other way round it would be good to introduce a version field to FIT images. With that at least newer U-Boot versions could print a more meaningful error message than just "image verification failed" which gives no clue what had actually happened. Sascha -- Pengutronix e.K. | | Steuerwalder Str. 21 | http://www.pengutronix.de/ | 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 |
