linux-kernel - Re: [PATCH v5 5/5] selftests/bpf: Add test for bpf_verify_pkcs7

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Date:   Wed, 22 Jun 2022 11:16:33 -0700
From:   Alexei Starovoitov <alexei.starovoitov@...il.com>
To:     Roberto Sassu <roberto.sassu@...wei.com>
Cc:     "ast@...nel.org" <ast@...nel.org>,
        "daniel@...earbox.net" <daniel@...earbox.net>,
        "andrii@...nel.org" <andrii@...nel.org>,
        "kpsingh@...nel.org" <kpsingh@...nel.org>,
        "john.fastabend@...il.com" <john.fastabend@...il.com>,
        "songliubraving@...com" <songliubraving@...com>,
        "kafai@...com" <kafai@...com>, "yhs@...com" <yhs@...com>,
        "dhowells@...hat.com" <dhowells@...hat.com>,
        "keyrings@...r.kernel.org" <keyrings@...r.kernel.org>,
        "bpf@...r.kernel.org" <bpf@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kselftest@...r.kernel.org" <linux-kselftest@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v5 5/5] selftests/bpf: Add test for bpf_verify_pkcs7_signature()
 helper

On Wed, Jun 22, 2022 at 12:06 AM Roberto Sassu <roberto.sassu@...wei.com> wrote:
>
> > From: Alexei Starovoitov [mailto:alexei.starovoitov@...il.com]
> > Sent: Wednesday, June 22, 2022 12:32 AM
> > On Tue, Jun 21, 2022 at 06:37:57PM +0200, Roberto Sassu wrote:
> > > +   if (child_pid == 0) {
> > > +           snprintf(path, sizeof(path), "%s/signing_key.pem", tmp_dir);
> > > +
> > > +           return execlp("./sign-file", "./sign-file", "-d", "sha256",
> > > +                         path, path, data_template, NULL);
> >
> > Did you miss my earlier reply requesting not to do this module_signature append
> > and use signature directly?
>
> I didn't miss. sign-file is producing the raw PKCS#7 signature here (-d).
>
> I'm doing something slightly different, to test the keyring ID part.
> I'm retrieving an existing kernel module (actually this does not work
> in the CI), parsing it to extract the raw signature, and passing it to the
> eBPF program for verification.

We don't have signed modules in CI.
When you make changes like this you have to explain that in the commit log.

> Since the kernel module is signed with a key in the built-in keyring,
> passing 1 or 0 as ID should work.
>
> Roberto
>
> (sorry, I have to keep the email signature by German law)

I don't believe that's the case since plenty of people
work from Germany and regularly contribute patches without
such banners.

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