On Thu, Mar 11, 2021 at 12:53:49PM +0800, Tianjia Zhang wrote: > > > On 3/11/21 11:42 AM, Jarkko Sakkinen wrote: > > On Thu, Mar 11, 2021 at 10:47:50AM +0800, Jia Zhang wrote: > > > > > > > > > On 2021/3/11 上午5:39, Jarkko Sakkinen wrote: > > > > On Wed, Mar 10, 2021 at 08:44:44PM +0800, Jia Zhang wrote: > > > > > > > > > > > > > > > On 2021/3/2 下午9:47, Jarkko Sakkinen wrote: > > > > > > On Mon, Mar 01, 2021 at 09:54:37PM -0800, Andy Lutomirski wrote: > > > > > > > On Mon, Mar 1, 2021 at 9:06 PM Tianjia Zhang > > > > > > > <tianjia.zhang@xxxxxxxxxxxxxxxxx> wrote: > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > On 3/1/21 5:54 PM, Jarkko Sakkinen wrote: > > > > > > > > > On Mon, Mar 01, 2021 at 01:18:36PM +0800, Tianjia Zhang wrote: > > > > > > > > > > q2 is not always 384-byte length. Sometimes it only has 383-byte. > > > > > > > > > > > > > > > > > > What does determine this? > > > > > > > > > > > > > > > > > > > In this case, the valid portion of q2 is reordered reversely for > > > > > > > > > > little endian order, and the remaining portion is filled with zero. > > > > > > > > > > > > > > > > > > I'm presuming that you want to say "In this case, q2 needs to be reversed because...". > > > > > > > > > > > > > > > > > > I'm lacking these details: > > > > > > > > > > > > > > > > > > 1. Why the length of Q2 can vary? > > > > > > > > > 2. Why reversing the bytes is the correct measure to counter-measure > > > > > > > > > this variation? > > > > > > > > > > > > > > > > > > /Jarkko > > > > > > > > > > > > > > > > > > > > > > > > > When use openssl to generate a key instead of using the built-in > > > > > > > > sign_key.pem, there is a probability that will encounter this problem. > > > > > > > > > > > > > > > > Here is a problematic key I encountered. The calculated q1 and q2 of > > > > > > > > this key are both 383 bytes, If the length is not processed, the > > > > > > > > hardware signature will fail. > > > > > > > > > > > > > > Presumably the issue is that some keys have parameters that have > > > > > > > enough leading 0 bits to be effectively shorter. The openssl API > > > > > > > (and, sadly, a bunch of the ASN.1 stuff) treats these parameters as > > > > > > > variable-size integers. > > > > > > > > > > > > But the test uses a static key. It used to generate a key on fly but > > > > > > > > > > IMO even though the test code, it comes from the linux kernel, meaning > > > > > that its quality has a certain guarantee and it is a good reference, so > > > > > the test code still needs to ensure its correctness. > > > > > > > > Hmm... what is working incorrectly then? > > > > > > In current implementation, it is working well, after all the static key > > > can derive the full 384-byte length of q1 and q2. As mentioned above, if > > > someone refers to the design of signing tool from selftest code, it is > > > quite possible that the actual implementation will use dynamical or > > > external signing key deriving shorter q1 and/or q2 in length. > > > > A self-test needs is not meant to be generic to be directly used in 3rd > > party code. With the current key there is not issue => there is no issue. > > > > For keys generated on fly, self-test does not work properly, this experience > is really worse. It does not generate keys on fly. There's a static key. /Jarkko
