test: fit: verify dm-verity roothash is covered by the config signature

2026-08-10T18:32:41Z

A dm-verity protected filesystem image is not hashed by U-Boot; its integrity is delegated to the kernel, which trusts the roothash taken from the FIT dm-verity subnode. For that chain of trust to hold, the roothash (and salt) must be part of the region covered by the configuration signature, otherwise an attacker can replace both the filesystem and the roothash while keeping the signature valid. Add two independent checks of this property: - test/py/tests/test_fit_verity_sign.py signs a configuration that references a filesystem image carrying a dm-verity subnode, then confirms that tampering the roothash or the salt is rejected by fit_check_sign. A control that tampers a byte known to be signed proves the check can fail. A matching page is added under doc/develop/pytest/ so the module documentation is rendered with the rest of the generated docs. - test/boot/fit_verity.c gains a runtime unit test that builds the exact node list the configuration signature is computed over, turns it into hashed regions and checks both that the roothash bytes fall inside a signed region and that tampering them changes the hash. It needs no private key, so it also runs on real devices and uses the same hash path a device would. To let the unit test build the signed-region node list, rename the config node-list helper to fit_config_get_signed_nodes(), make it non-static and declare it in image.h. Signed-off-by: Daniel Golle Reviewed-by: Simon Glass

u-boot.git/doc/develop/pytest/test_fit_verity_sign.rst, branch main

test: fit: verify dm-verity roothash is covered by the config signature