4 ms·
Summary: the secure boot ROM is validated by a SHA-256 hash, instead of being authenticated by a crypto signature, so one is free to tamper with the bootloader
by mrb 10y ago
Summary: the secure boot ROM is validated by a SHA-256 hash, instead of being authenticated by a crypto signature, so one is free to tamper with the bootloader as long as the hash is recomputed correctly. The strangest thing is that there is support for RSA signatures, but the feature is just unused.
- lima 10y agoFor anyone wondering: the hash is part of the boot ROM that is being authenticated
- aexaey 10y agoNot quite. Weakness is later in the chain. Secure second-stage loader (BL2) loads secure third-stage loader (BL31) from insecure flash storage, then verifies it by calculating SHA-256 hash of it and comparing that to the value stored in the same insecure flash.
- planteen 10y agoThe Xilinx Zynq has one time programmable eFuse registers for this sort of thing
- deleted 10y ago[deleted]
- gcr 10y agoHow easy is it to change the input of SHA256 without changing the output? That strikes me as still very difficult (MD5 is basically worthless for this reason).