U-Boot FIT Signature Verification

[Heinrich Schuchardt]

On 16.09.20 10:13, AKASHI Takahiro wrote:
> On Wed, Sep 16, 2020 at 01:19:03AM +0200, Heinrich Schuchardt wrote:
>> On 9/11/20 7:26 PM, Andrii Voloshyn wrote:
>>> Hi there,
>>>
>>>     Does U-boot take into account certificate expiration date when verifying signed images in FIT? In other words, is date stored along with the public key in DTB file?
>>>
>>> Cheers,
>>> Andy
>>>
>>
>> Hello Philippe,
>>
>> looking at padding_pkcs_15_verify() in lib/rsa/rsa-verify.c I cannot
>> find a comparison of the date on which an image was signed with the
>> expiry date of the certificate. Shouldn't there be a check? Or did I
>> simply look into the wrong function?
>
> I think Simon is the right person to answer this question, but
>
> as far as I know, we don't have any device tree property for the expiration
> date of a public key. See doc/uImage.FIT/signature.txt.

Yes, the problem starts with mkimage not writing the dates available in
the X509 certificate into the device tree.

The dates are accessible via the X509_get0_notBefore() and
X509_get0_notAfter() functions of the OpenSSL library.


Takahiro, could you, please, also look at the UEFI secure boot
implementation in U-Boot. EDK2 validates the dates via the embedded
OpenSSL library in
CryptoPkg/Library/OpensslLib/openssl/crypto/x509/x509_vfy.c, function
verify_chain(). We should not do less.

Best regards

Heinrich