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

[Roberto Sassu <roberto.sassu@huaweicloud.com>]

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