On Wed, Mar 04, 2026 at 08:31:46AM +0100, Sascha Hauer wrote: > 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.
It's not the first time we've had a break in backwards compatibility but previously we had at least printed something about it specifically. -- Tom
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