RUSTSEC-2022-0103

The coreos-installer is a program to fetch a disk image and

stream it to a target disk.

During the installation process the installation image gpg

signatures are verified.

The signature verification can be bypassed for gzip-compressed

images due to a flaw in gzip coreos-installer wrapper.

When the decoder encounters the gzip trailer, it signals EOF

to its output and does not continue reading from its input.

As a result, earlier wrappers don't notice that they've reached

EOF.

In particular, the GPG wrapper does not check the exit code of GPG.

Thus, if an attacker can substitute an attacker-controlled

gzipped disk image, installation will complete successfully

without a valid signature.

This vulnerability impacts only specific, User-Provisioned

Infrastructure (UPI) installation methods where coreos-installer

is used and where gzip-compressed images are configured as

the installation source.

The Installer-Provisioned Infrastructure (IPI) bare-metal

installs do use coreos-installer, but this installation

method uses an install image embedded in the live OS image

(ISO or PXE image), therefore is not affected by this

vulnerability.

This vulnerability is specific to some upstream Fedora

CoreOS installation flows.