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ee88832841
Argon2 is the default LUKS Password-Based Key Derivation Function
(PBKDF) for some new guests such as RHEL 8.2 and Fedora. It is
designed to be "memory hard", meaning that by design it requires large
amounts of memory, making it expensive to brute-force. Unfortunately
the default for guests which had more than a few GB of RAM at install
time is to require about 1 GB of RAM to decrypt the block device,
which is considerably larger than the default available in the
libguestfs appliance.
To make it possible to open these encrypted disks we need to make the
appliance larger. This could be done as a one-off, and the current
workaround is simply to set LIBGUESTFS_MEMSIZE=2048 or a similar
amount. However since we don't know in advance whether we could be
dealing with an encrypted disk, partition, etc. or what PBKDF it uses,
the only way to deal with this in all circumstances is to increase the
default memsize. This commit increases it quite a lot (768 -> 1280)
which is unfortunate.
Note as there is some confusion on this point: Since libguestfs does
not attempt to decrypt disks in parallel, you only need ~ 1GB in
total, not per encrypted disk.
For a reproducer, see:
https://bugzilla.redhat.com/show_bug.cgi?id=1837765#c14
(cherry picked from commit 224f373043)