Re: [PATCH] Revert "firmware: dmi_scan: Use lowercase letters for UUID"

From: Peter Korsgaard
Date: Thu Dec 06 2018 - 04:22:24 EST


>>>>> "Jean" == Jean Delvare <jdelvare@xxxxxxxx> writes:

> On Wed, 2018-12-05 at 22:13 +0100, Peter Korsgaard wrote:
>> This reverts commit 712ff25450bd01366301eef81c33e865d901e7b7.
>>
>> The output of dmi_save_uuid() is exposed to user space as
>> /sys/devices/virtual/dmi/id/*_uuid, so this breaks backwards compatibility,
>> E.G. I have systems that include the content of dmi/id/product_uuid as part
>> of the keyphrase for cryptsetup luksOpen.
>>
>> As the change was purely cosmetical, revert it to fix such breakage.

> The change is not "cosmetical". The change was done to comply with RFC
> 4122:

> https://tools.ietf.org/html/rfc4122

> The hexadecimal values "a" through "f" are output as
> lower case characters and are case insensitive on input.

I get that - but it changes the content of sysfs entries, breaking real
systems - E.G. a user space ABI regression.

It is a cosmetic code change in the sense that no known software was
broken with the upper case characters.


> If "cryptsetup luksOpen" does not lowercase digits before computing its
> key passphrase, then it's not RFC 4122-compliant and should be fixed.

cryptsetup naturally doesn't know anything about RFC 4122. It just reads
a disk encryption keyphrase which happen to include the content of
id/product_uuid because of my scripts.

> Nak. This is too late. Changing it again would just add confusion.

Please reconsider. 4.17 is from June, and 4.19 has only recently become
LTS.

--
Bye, Peter Korsgaard