linux-kernel - Re: [PATCH bpf-next 0/3] bpf: add signature

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Date:   Fri, 3 Dec 2021 18:02:43 -0800
From:   Alexei Starovoitov <alexei.starovoitov@...il.com>
To:     Matteo Croce <mcroce@...ux.microsoft.com>
Cc:     Luca Boccassi <bluca@...ian.org>, bpf <bpf@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>,
        Jakub Kicinski <kuba@...nel.org>,
        Jesper Dangaard Brouer <hawk@...nel.org>,
        keyrings@...r.kernel.org,
        Linux Crypto Mailing List <linux-crypto@...r.kernel.org>,
        Lorenzo Bianconi <lorenzo@...nel.org>
Subject: Re: [PATCH bpf-next 0/3] bpf: add signature

On Fri, Dec 3, 2021 at 4:42 PM Matteo Croce <mcroce@...ux.microsoft.com> wrote:
>
> On Fri, Dec 3, 2021 at 11:20 PM Alexei Starovoitov
> <alexei.starovoitov@...il.com> wrote:
> >
> > On Fri, Dec 3, 2021 at 2:06 PM Luca Boccassi <bluca@...ian.org> wrote:
> > >
> > > On Fri, 2021-12-03 at 11:37 -0800, Alexei Starovoitov wrote:
> > > > On Fri, Dec 3, 2021 at 11:36 AM Matteo Croce
> > > > <mcroce@...ux.microsoft.com> wrote:
> > > > >
> > > > > On Fri, Dec 3, 2021 at 8:22 PM Alexei Starovoitov
> > > > > <alexei.starovoitov@...il.com> wrote:
> > > > > >
> > > > > > On Fri, Dec 3, 2021 at 11:18 AM Matteo Croce
> > > > > > <mcroce@...ux.microsoft.com> wrote:
> > > > > > >
> > > > > > > From: Matteo Croce <mcroce@...rosoft.com>
> > > > > > >
> > > > > > > This series add signature verification for BPF files.
> > > > > > > The first patch implements the signature validation in the
> > > > > > > kernel,
> > > > > > > the second patch optionally makes the signature mandatory,
> > > > > > > the third adds signature generation to bpftool.
> > > > > >
> > > > > > Matteo,
> > > > > >
> > > > > > I think I already mentioned that it's no-go as-is.
> > > > > > We've agreed to go with John's suggestion.
> > > > >
> > > > > Hi,
> > > > >
> > > > > my previous attempt was loading a whole ELF file and parsing it in
> > > > > kernel.
> > > > > In this series I just validate the instructions against a
> > > > > signature,
> > > > > as with kernel CO-RE libbpf doesn't need to mangle it.
> > > > >
> > > > > Which suggestion? I think I missed this one..
> > > >
> > > > This talk and discussion:
> > > > https://linuxplumbersconf.org/event/11/contributions/947/
> > >
> > > Thanks for the link - but for those of us who don't have ~5 hours to
> > > watch a video recording, would you mind sharing a one line summary,
> > > please? Is there an alternative patch series implementing BPF signing
> > > that you can link us so that we can look at it? Just a link or
> > > googlable reference would be more than enough.
> >
> > It's not 5 hours and you have to read slides and watch
> > John's presentation to follow the conversation.
>
> So, If I have understood correctly, the proposal is to validate the
> tools which loads the BPF (e.g. perf, ip) with fs-verity, and only
> allow BPF loading from those validated binaries?
> That's nice, but I think that this could be complementary to the
> instructions signature.
> Imagine a validated binary being exploited somehow at runtime, that
> could be vector of malicious BPF program load.
> Can't we have both available, and use one or other, or even both
> together depending on the use case?

I'll let John comment.