
Amlogic S905 SoC: Bypassing the not so Secure Boot to dump the boot ROM - zdw
http://www.fredericb.info/2016/10/amlogic-s905-soc-bypassing-not-so.html
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mrb
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.

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aexaey
Not 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_.

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planteen
The Xilinx Zynq has one time programmable eFuse registers for this sort of
thing

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bravo22
Very good read!

But, in fairness this isn't a failure of the S905 SOC. It is a bug in the
second stage bootloader that fails to authenticate the next image.

The SoC BootROM validates the RSA signature of the second stage bootloader.

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subway
Huh. I wonder what the implications are for Play Store's DRM.

Specifically it seems like this board could be used to strip DRM from media.

