On Thu, 25 Feb 2021 at 12:06, Ard Biesheuvel <[email protected]> wrote: > > On Thu, 25 Feb 2021 at 11:35, Salvatore Bonaccorso <[email protected]> wrote: > > > > Hi Ard, > > > > On Mon, Feb 01, 2021 at 10:21:27PM +0100, Salvatore Bonaccorso wrote: > > > Hi Ard, > > > > > > On Sat, Jan 30, 2021 at 04:41:16PM +0100, Ard Biesheuvel wrote: > > > > L.S., > > > > > > > > This is a request to consider disabling obsolete crypto in 5.10 and > > > > later Debian builds of the Linux kernel on any architecture. > > > > > > > > We are all familiar with the rigid rules when it comes to not breaking > > > > userspace by making changes to the kernel, but this rule only takes > > > > effect when anybody notices, and so I am proposing disabling some code > > > > downstream before removing it entirely. > > > > > > > > 5.10 introduces a new Kconfig symbol > > > > > > > > CONFIG_CRYPTO_USER_API_ENABLE_OBSOLETE > > > > > > > > which is enabled by default, but depends on support for the AF_ALG > > > > socket API being enabled. In turn, block ciphers that are obsolete and > > > > unlikely to be used anywhere have been made to depend on this new > > > > symbol. > > > > > > > > This means that these obsolete block ciphers will disappear entirely > > > > when the AF_ALG socket API is omitted, but we can get rid of these > > > > block ciphers explicitly too, by not setting the new symbol. I.e., > > > > adding > > > > > > > > # CONFIG_CRYPTO_USER_API_ENABLE_OBSOLETE is not set > > > > > > > > to the kernel configs. Note that Fedora have already done so in release > > > > 33 [0] > > > > > > > > The block ciphers in question are RC4, Khazad, SEED, and > > > > TEA/XTEA/XETA, none of which are used by the kernel itself, or known > > > > to be used via the socket API (although a change was applied to > > > > iwd/libell recently to get rid of an occurrence of RC4 - this change > > > > has already been pulled into bullseye afaik) > > > > > > > > Note that this is not a statement on whether these algorithms are > > > > secure or not -there is simply no point in carrying and shipping code > > > > that nobody uses or audits, but which can be autoloaded and exercised > > > > via an unprivileged interface. > > > > > > FTR (posteriori), we tried that in > > > https://salsa.debian.org/kernel-team/linux/-/commit/633e1992f7d915c22b2a2adea87981e7503bb737 > > > (and is in the 5.10.12-1 upload to unstable). > > > > There were two reports which might be in the end related to that > > change: > > > > https://bugs.debian.org/979764 > > https://bugs.debian.org/983508 > > > > We have long that nfs-utils need to be updated, but the version was so > > outdated, that progress on updating to a newer version stalled, and > > could not be done in time for bulleye. Once bullseye is released I > > guess this really needs to be prioritzed in some way. > > > > Ard, have you any insight in the above, so, should we revert the above > > change for bullseye again? > > > > Hello Salvatore, > > I think the issue is the patch below. Having something that requires > RC4 and MD5 for security is an absolute joke in 2021, so I won't > recommend you reverting it. Instead, you should really fix nfs-utils > with priority. >
Any updates on this?
