The worst thing about UEFI HTTP boot is the utter lack of information to debug anything that's gone wrong. Whether that's the DHCP filename option is some wrong format for whatever stupid mode the UEFI is in, or there's some dhcp relay issue. It literally tells you almost nothing besides "can't get NBP file size".
The error messages seem to be written by people on a happy path who don't know how utterly broken almost everything about networking and DHCP even is.
And this is all IPv4! The IPv6 stuff is even more cryptic with different DHCP options and dealing with RAs and managed-flag, other-flag, etc.
It's infuriating. And I work on a team that writes code to generate all these things for automating bare metal for a living.
BTW Apple has been doing HTTP boot for like two decades at this point. How do you think Internet Recovery works? It leverages a dusty old Apple netbooting spec.
Unfortunately, Apple seems to be alone in having a good implementation. Using the old PXE, you expect to see some dos-like screens and slow loading but with HTTP the experience is not much better. Any decently sized bootloader is downloaded at a snails-pace and the user is presented with a very technical screen. Fine for rescue-boot like purposes but not fine when your daily driver is expected to be booted from network. I had especially expected better from Dell but the experience is... lacking.
> Unfortunately, Apple seems to be alone in having a good implementation.
Well, Apple is in full control over their entire stack, down to the firmware on the embedded parts.
In the non-Apple world, no way, simply due to the sheer insane amount of different ethernet and wireless chipsets, with many of them shipping binary blobs. The mediatek blobs alone expand to 64MB [1], Intel clocks in a further 24 MB [2], and then there's all the other firmware stuff.
Unfortunately, there is nothing in the "physical world" that comes even close to USB-CDC in its versatility.
Having http as an alternative to tftp is a nice win. The range of things that can run an http server is much bigger than tftp
>Additionally, adding the TLS layer brings back the missing integrity and confidentiality guarantees and thus paves the way to move critical boot components out of the trusted network, possibly even to a remote location/Cloud.
Doesn't secure boot already provide this or am I misunderstanding something? I suppose secure boot only provides integrity but not confidentiality although I'm not sure how much confidentiality matters given we're just talking about the kernel here
> > adding the TLS layer brings back the missing integrity
A foolish interpretation of what TLS does and I see this every day. Integrity of the bits and bytes in transit is unimportant here. Validation of the signed software after you have received it is everything. TLS integrity is at best redundant and at worst — the interpretation made here — leaves you vulnerable and with a false sense of security.
Anyone who has gone to the trouble to modify software to inject malware would certainly happily serve it to you over TLS.
In theory the client could validate a specific server with a pinned certificate, although TLS implementations can make this difficult to do in practice. TLS also lets you use client certificates to authenticate the client to the server, which could be a win in some situations (although also a PITA to set up).
NBD (over TLS) would be even better because it loads on demand. You could ship large full-featured OS images and only the parts/features you used would be loaded. One day when I'm retired I plan to add this to OVMF.
> The range of things that can run an http server is much bigger than tftp
Don't go too crazy though, these UEFI HTTP clients are not well behaved. For example, last time I checked, EDK required the URL to end with ".efi", instead of checking Content-Type header.
I have an HTTP netboot flow that worked on older AMI Aptio firmwares, but fails on anything newer to even fetch the bootfile after a successful DHCP cycle, so I heartily agree with your sentiment that these are not necessarily well adjusted clients!
Secure boot is designed to verify software signatures. The UEFI bios might support loading software over https, but it isn't part of secure boot. Secure boot would verify any kernels/etc loaded from https.
That was the point as I read it. Payload signature verification is a good and sometimes desirable alternative to transport encryption when the payload itself isn't secret.
Highly-cacheable resources like game and OS updates are often intentionally delivered over http as signed payloads to facilitate middlebox caching.
> Secure boot is designed to verify software signatures
aka integrity.
HTTPS is a useless gesture here, adding complexity to critical software that needs to be as simple and auditable as possible. Confidentiality is essentially unimportant to anyone but the most autistic of by-the-book nerds. It buys you nothing in a practical sense. Most netbooting happens over closed networks anyway.
I agree that integrity can be done by secure boot, but HTTPS does mean that someone can't intercept your request and serve you valid, signed, older software that has a known security flaw in it.
1. Just a matter of a boot entry. However adding the boot entry is not trivial: efibootmgr used to have implementation which have been reverted (it was incomplete, works only with full device path unlike just MAC which the original code added).
I don't know any utilities to do that, ended patching efibootmgr myself.
There's still the tftp->ipxe->http->??? path. TFTP only needs to serve a 300kb file which can then switch to more robust transport like http for the kernel/OS
You could bypass that by shipping iPXE on USB tho
On metal you also commonly have a BMC so generally that lets you attach an ISO or other storage you can boot from to bypass UEFI primitive PXE. This is probably the biggest one--use BMC functionality instead of UEFI PXE
At home, I use JetKVM or GL.iNet Comet network KVM to bootstrap commodity hardware without BMC (by attaching an ISO). Probably could make a cheap commodity device with Raspberry Pi Zero that does that same thing at lower cost although at that point you're back to "just use USB storage"
The error messages seem to be written by people on a happy path who don't know how utterly broken almost everything about networking and DHCP even is.
And this is all IPv4! The IPv6 stuff is even more cryptic with different DHCP options and dealing with RAs and managed-flag, other-flag, etc.
It's infuriating. And I work on a team that writes code to generate all these things for automating bare metal for a living.
Well, Apple is in full control over their entire stack, down to the firmware on the embedded parts.
In the non-Apple world, no way, simply due to the sheer insane amount of different ethernet and wireless chipsets, with many of them shipping binary blobs. The mediatek blobs alone expand to 64MB [1], Intel clocks in a further 24 MB [2], and then there's all the other firmware stuff.
Unfortunately, there is nothing in the "physical world" that comes even close to USB-CDC in its versatility.
[1] https://packages.debian.org/forky/firmware-mediatek
[2] https://packages.debian.org/forky/firmware-intel-misc
>Additionally, adding the TLS layer brings back the missing integrity and confidentiality guarantees and thus paves the way to move critical boot components out of the trusted network, possibly even to a remote location/Cloud.
Doesn't secure boot already provide this or am I misunderstanding something? I suppose secure boot only provides integrity but not confidentiality although I'm not sure how much confidentiality matters given we're just talking about the kernel here
A foolish interpretation of what TLS does and I see this every day. Integrity of the bits and bytes in transit is unimportant here. Validation of the signed software after you have received it is everything. TLS integrity is at best redundant and at worst — the interpretation made here — leaves you vulnerable and with a false sense of security.
Anyone who has gone to the trouble to modify software to inject malware would certainly happily serve it to you over TLS.
Don't go too crazy though, these UEFI HTTP clients are not well behaved. For example, last time I checked, EDK required the URL to end with ".efi", instead of checking Content-Type header.
I have an HTTP netboot flow that worked on older AMI Aptio firmwares, but fails on anything newer to even fetch the bootfile after a successful DHCP cycle, so I heartily agree with your sentiment that these are not necessarily well adjusted clients!
Highly-cacheable resources like game and OS updates are often intentionally delivered over http as signed payloads to facilitate middlebox caching.
aka integrity.
HTTPS is a useless gesture here, adding complexity to critical software that needs to be as simple and auditable as possible. Confidentiality is essentially unimportant to anyone but the most autistic of by-the-book nerds. It buys you nothing in a practical sense. Most netbooting happens over closed networks anyway.
1. Just a matter of a boot entry. However adding the boot entry is not trivial: efibootmgr used to have implementation which have been reverted (it was incomplete, works only with full device path unlike just MAC which the original code added).
I don't know any utilities to do that, ended patching efibootmgr myself.
Learned about it from this talk: https://youtu.be/EtGhHCr3VLE?t=567
2. HTTP Boot is also available as a DHCP option 67 without boot entry:
* https://github.com/tianocore/tianocore.github.io/wiki/HTTP-B...
* https://documentation.suse.com/sles/15-SP6/html/SLES-all/cha...
You could bypass that by shipping iPXE on USB tho
On metal you also commonly have a BMC so generally that lets you attach an ISO or other storage you can boot from to bypass UEFI primitive PXE. This is probably the biggest one--use BMC functionality instead of UEFI PXE
At home, I use JetKVM or GL.iNet Comet network KVM to bootstrap commodity hardware without BMC (by attaching an ISO). Probably could make a cheap commodity device with Raspberry Pi Zero that does that same thing at lower cost although at that point you're back to "just use USB storage"