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From ee88832841e82a407c9df44a82b87270ec0d492b Mon Sep 17 00:00:00 2001
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From: "Richard W.M. Jones" <rjones@redhat.com>
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Date: Tue, 30 Jun 2020 17:34:47 +0100
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Subject: [PATCH] lib: Increase default memsize to 1280 (RHBZ#1837765).
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Argon2 is the default LUKS Password-Based Key Derivation Function
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(PBKDF) for some new guests such as RHEL 8.2 and Fedora. It is
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designed to be "memory hard", meaning that by design it requires large
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amounts of memory, making it expensive to brute-force. Unfortunately
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the default for guests which had more than a few GB of RAM at install
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time is to require about 1 GB of RAM to decrypt the block device,
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which is considerably larger than the default available in the
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libguestfs appliance.
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To make it possible to open these encrypted disks we need to make the
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appliance larger. This could be done as a one-off, and the current
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workaround is simply to set LIBGUESTFS_MEMSIZE=2048 or a similar
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amount. However since we don't know in advance whether we could be
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dealing with an encrypted disk, partition, etc. or what PBKDF it uses,
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the only way to deal with this in all circumstances is to increase the
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default memsize. This commit increases it quite a lot (768 -> 1280)
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which is unfortunate.
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Note as there is some confusion on this point: Since libguestfs does
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not attempt to decrypt disks in parallel, you only need ~ 1GB in
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total, not per encrypted disk.
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For a reproducer, see:
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https://bugzilla.redhat.com/show_bug.cgi?id=1837765#c14
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(cherry picked from commit 224f373043302845122bf701ffc6e3416e0168fa)
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---
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lib/guestfs-internal.h | 6 +++---
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1 file changed, 3 insertions(+), 3 deletions(-)
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diff --git a/lib/guestfs-internal.h b/lib/guestfs-internal.h
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index 75b8a5c8e..30553d7c0 100644
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--- a/lib/guestfs-internal.h
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+++ b/lib/guestfs-internal.h
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@@ -94,7 +94,7 @@
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* creating device nodes.
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*/
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#ifdef __powerpc__
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-# define DEFAULT_MEMSIZE 1024
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+# define DEFAULT_MEMSIZE 1280
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#endif
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/* Kernel 3.19 is unable to uncompress the initramfs on aarch64 unless
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@@ -103,12 +103,12 @@
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* common on aarch64, treat this like the ppc case above.
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*/
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#ifdef __aarch64__
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-# define DEFAULT_MEMSIZE 1024
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+# define DEFAULT_MEMSIZE 1280
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#endif
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/* The default and minimum memory size for most users. */
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#ifndef DEFAULT_MEMSIZE
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-# define DEFAULT_MEMSIZE 768
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+# define DEFAULT_MEMSIZE 1280
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#endif
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#ifndef MIN_MEMSIZE
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# define MIN_MEMSIZE 256
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--
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2.18.4
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