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Bug#930217: Please provide support for alternative network bootloaders

Package: src:shim
Version: 15+1533136590.3beb971-7
Severity: wishlist

(I'm Cc'ing the syslinux and iPXE maintainers here for their information
and to seek their opinion. I haven't discussed this matter with neither
of them and do not speak for them.)

Currently, the only way to network boot a Debian EFI system with Secure
Boot via shim is to use GRUB, as this is the only combination that's
SB-signed (bootnetx64.efi even hardcodes grubx64.efi). This is what
Debian's own netboot.tar.gz ship with as well

However, GRUB's TCP/IP + DNS + HTTP stack is... to put it politely,
severely lacking. I've managed to crash it[1], find serious TCP[2] or
HTTP[3] implementation bugs, run into very basic limitations (e.g. on
dual-stack hostnames[5]), all within a few hours. For some reason
they've decided to build a TCP/IP stack from scratch (rather than use
EFI's, or something like lwIP), but their code, to this day, has
comments like "/* FIXME: overflow. */". I've tried to build a sane
netboot configuration with GRUB, and work around its bugs, but
ultimately failed -- it's just too buggy for anything but just booting a
kernel + initramfs, and if even that.

1: 52408aa94604466bdd80f48fa8d68378a1ffab31
2: https://savannah.gnu.org/bugs/?56391
3: https://savannah.gnu.org/bugs/?49531
4: https://savannah.gnu.org/bugs/?56390

Despite these having been reported upstream, I don't have high hopes;
their bug tracker is a dumpster fire. Noone is responding to old or new
bugs, no matter their severity. I was looking into SMBIOS support as
well, and it looks someone has written a working patch that other
distributions ship; that person has been submitting it once a year since
2013, and never received a response. I filed this as a bug in their bug
tracker[5] but that has not received a response either.

5: https://savannah.gnu.org/bugs/?56164

All in all, I think there are two compounding issues here: 1) the GRUB
project's overall health 2) network boot not being a priority for them.

However, this being free software, there are alternatives :) The two
most popular network bootloaders are:

1) SYSLINUX (syslinux.efi specifically): this is much more restricted in
terms of features, but good enough for many use cases and more reliable
than GRUB. syslinux.efi uses the EFI stack's TCP/IP implementation
(Tcp4ServiceBindingProtocol) and doesn't roll its own, which at least
makes it more secure than GRUB's (albeit without IPv6 support right
now). The other advantage here is that this is fully compatible with a
PXELINUX config which most people are used to. Debian's own d-i images
ship with such a configuration to this day and this could be an
out-of-the box alternative.

2) iPXE: this is widely used in both PXE and EFI configurations. QEMU is
even using it to netboot by default. It has a flexible configuration
language, lots of features out of the box, and a much, much, much
cleaner codebase than GRUB.  Their documentation is far more superior
too. They even have a page with instructions for how one can submit iPXE
to Microsoft to get it SB-signed[6] and there are reports on the web
that Microsoft has actually signed[7] of their versions.

6: http://ipxe.org/appnote/etoken
7: https://twitter.com/ipxe/status/331176286972157953

The request here is for Debian w/ Shim to support an alternative to GRUB
out of the box, and to sign iPXE and/or syslinux. These are alternatives
that are clearly superior in features, stability -and, dare I say,
security- over GRUB and Debian shouldn't artificially limit our choices
to just one.

An alternative to this proposal would be for Debian to submit e.g. iPXE
separately to Microsoft for signatures and not use this in combination
with shim. I believe this doesn't fit with the overall strategy that
Debian and other distributions have chosen around Secure Boot with shim,
but... I am really not an expert :)

Thanks for the consideration!


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