U-Boot FIT Signature Verification

[Joakim Tjernlund]

On Wed, 2020-09-16 at 13:55 +0200, Heinrich Schuchardt wrote:
> On 16.09.20 13:40, Joakim Tjernlund wrote:
> > On Wed, 2020-09-16 at 13:14 +0200, Heinrich Schuchardt wrote:
> > > CAUTION: This email originated from outside of the organization. Do not click links or open attachments unless you recognize the sender and know the content is safe.
> > > 
> > > 
> > > 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.
> > 
> > Does that mean that verified boot stops/fails when the date expires ?
> > How do you guarantee that the device has the correct time ?
> > 
> >    Jocke
> > 
> 
> We talking of the validity time range of the public key and the date of
> signature of the intermediate certificates and the loaded image. No RTC

OK, but still: will an invalid time range then stop booting ?