[PATCH] rsa: fix alignment issue when getting public exponent

[Tom Rini]

On Sun, May 03, 2020 at 01:26:34PM +0200, Heiko Stuebner wrote:

> From: Heiko Stuebner <heiko.stuebner at theobroma-systems.com>
> 
> To fill the exponent field of the rsa_public_key struct, rsa_mod_exp_sw
> did a cast to uint64_t of the key_prop->public_exponent field.
> But that alignment is not guaranteed in all cases.
> 
> This came to light when in my spl-fit-signature the key-name exceeded
> a certain length and with it the verification then started failing.
> (naming it "integrity" worked fine, "integrity-uboot" failed)
> 
> key_prop.public_exponent itself is actually a void-pointer, fdt_getprop()
> also just returns such a void-pointer and inside the devicetree the 64bit
> exponent is represented as 2 32bit numbers, so assuming a 64bit alignment
> can lead to false reads.
> 
> So just use the already existing rsa_convert_big_endian() to do the actual
> conversion from the dt's big-endian to the needed uint64 value.
> 
> Fixes: fc2f4246b4b3 ("rsa: Split the rsa-verify to separate the modular exponentiation")
> Signed-off-by: Heiko Stuebner <heiko.stuebner at theobroma-systems.com>
> Reviewed-by: Philipp Tomsich <philipp.tomsich at theobroma-systems.com>
> Reviewed-by: Simon Glass <sjg at chromium.org>

Applied to u-boot/master, thanks!

-- 
Tom
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