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

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Message-ID: <76c319d5ad1e4ac69ae5d3f71e9d62f7@huawei.com>
Date:   Wed, 22 Jun 2022 07:06:12 +0000
From:   Roberto Sassu <roberto.sassu@...wei.com>
To:     Alexei Starovoitov <alexei.starovoitov@...il.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

> 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.

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)

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