linux-kernel - Re: [PATCH 1/3] bpf: Add BPF_F_VERIFY_ELEM to require signature verification on map values

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Date:   Sat, 4 Jun 2022 11:32:15 +0200
From:   Alexei Starovoitov <alexei.starovoitov@...il.com>
To:     Roberto Sassu <roberto.sassu@...wei.com>
Cc:     KP Singh <kpsingh@...nel.org>, "ast@...nel.org" <ast@...nel.org>,
        "daniel@...earbox.net" <daniel@...earbox.net>,
        "andrii@...nel.org" <andrii@...nel.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 1/3] bpf: Add BPF_F_VERIFY_ELEM to require signature
 verification on map values

On Fri, Jun 3, 2022 at 5:44 PM Roberto Sassu <roberto.sassu@...wei.com> wrote:
> >
> > Your bpf_map_verify_value_sig hard codes the type of signature
> > (bpf_map_verify_value_sig as verify_pkcs7_signature)
> > its implementation. This is not extensible.
>
> It is hardcoded now, but it wouldn't if there are more verification
> functions. For example, if 'id_type' of module_signature is set
> to PKEY_ID_PGP, bpf_map_verify_value_sig() would call
> verify_pgp_signature() (assuming that support for PGP keys and
> signatures is added to the kernel).

I agree with KP. All hard coded things are hurting extensibility.
we just need a helper that calls verify_pkcs7_signature
where prog will specify len, keyring, etc.