linux-kernel - Re: [PATCH v6 07/15] digest_cache: Allow registration of digest list parsers

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Message-ID: <57f07e0048ff15fd1ebfb58054e93abdbf8f029c.camel@huaweicloud.com>
Date: Fri, 29 Nov 2024 09:30:49 +0100
From: Roberto Sassu <roberto.sassu@...weicloud.com>
To: Luis Chamberlain <mcgrof@...nel.org>, mmaurer@...gle.com, 
	samitolvanen@...gle.com, KP Singh <kpsingh@...nel.org>
Cc: zohar@...ux.ibm.com, dmitry.kasatkin@...il.com,
 eric.snowberg@...cle.com,  corbet@....net, petr.pavlu@...e.com,
 da.gomez@...sung.com,  akpm@...ux-foundation.org, paul@...l-moore.com,
 jmorris@...ei.org,  serge@...lyn.com, shuah@...nel.org,
 mcoquelin.stm32@...il.com,  alexandre.torgue@...s.st.com,
 linux-integrity@...r.kernel.org,  linux-doc@...r.kernel.org,
 linux-kernel@...r.kernel.org,  linux-api@...r.kernel.org,
 linux-modules@...r.kernel.org,  linux-security-module@...r.kernel.org,
 linux-kselftest@...r.kernel.org,  wufan@...ux.microsoft.com,
 pbrobinson@...il.com, zbyszek@...waw.pl, hch@....de,  mjg59@...f.ucam.org,
 pmatilai@...hat.com, jannh@...gle.com, dhowells@...hat.com, 
 jikos@...nel.org, mkoutny@...e.com, ppavlu@...e.com, petr.vorel@...il.com, 
 mzerqung@...inter.de, kgold@...ux.ibm.com, Roberto Sassu
 <roberto.sassu@...wei.com>
Subject: Re: [PATCH v6 07/15] digest_cache: Allow registration of digest
 list parsers

On Thu, 2024-11-28 at 12:40 -0800, Luis Chamberlain wrote:
> On Thu, Nov 28, 2024 at 09:23:57AM +0100, Roberto Sassu wrote:
> > On Wed, 2024-11-27 at 11:53 -0800, Luis Chamberlain wrote:
> > > On Wed, Nov 27, 2024 at 10:51:11AM +0100, Roberto Sassu wrote:
> > > > For eBPF programs we are also in a need for a better way to
> > > > measure/appraise them.
> > > 
> > > I am confused now, I was under the impression this "Integrity Digest
> > > Cache" is just a special thing for LSMs, and so I was under the
> > > impression that kernel_read_file() lsm hook already would take care
> > > of eBPF programs.
> > 
> > Yes, the problem is that eBPF programs are transformed in user space
> > before they are sent to the kernel:
> > 
> > https://lwn.net/Articles/977394/
> 
> That issue seems to be orthogonal to your eandeavor though, which just
> supplements LSMS, right?

Yes, correct, the Integrity Digest Cache would be used to search
whatever digest was calculated by LSMs.

Thanks

Roberto

> Anyway, in case this helps:
> 
> The Rust folks faced some slighty related challenges with our CRC
> validations for symbols, our CRC are slapped on with genksyms but this
> relies on the source code and with Rust the compiler may do final
> touches to data. And so DWARF is being used [1].
> 
> Although I am not sure of the state of eBPF DWARF support, there is also
> BTF support [0] and most distros are relying on it to make live introspection 
> easier, and the output is much smaller. So could DWARF or BTF information
> from eBPF programs be used by the verifier in similar way to verify eBPF
> programs?
> 
> Note that to support BTF implicates DWARF and the leap of faith for Rust
> modversions support is that most distros will support DWARF, and so BTF
> can become the norm [2].
> 
> [0] https://www.kernel.org/doc/html/latest/bpf/btf.html
> [1] https://lwn.net/Articles/986892/
> [2] https://lwn.net/Articles/991719/
> 
>   Luis