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Accepting request 986262 from Virtualization

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Fix for bsc#1201064 VUL-0: CVE-2022-2211: Libguestfs: Buffer overflow in get_keys leads to DOS

OBS-URL: https://build.opensuse.org/request/show/986262
OBS-URL: https://build.opensuse.org/package/show/openSUSE:Factory/libguestfs?expand=0&rev=82
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Dominique Leuenberger 2022-07-02 13:34:26 +00:00 committed by Git OBS Bridge
commit b75efca023
4 changed files with 181 additions and 0 deletions
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CVE-2022-2211-docs-guestfs-security-document.patch Normal file
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@ -0,0 +1,55 @@
Subject: docs/guestfs-security: document CVE-2022-2211
From: Laszlo Ersek lersek@redhat.com Tue Jun 28 13:54:16 2022 +0200
Date: Wed Jun 29 15:29:37 2022 +0200:
Git: 99844660b48ed809e37378262c65d63df6ce4a53
Short log for the common submodule, commit range
f8de5508fe75..35467027f657:
Laszlo Ersek (2):
mlcustomize: factor out pkg install/update/uninstall from guestfs-tools
options: fix buffer overflow in get_keys() [CVE-2022-2211]
Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1809453
Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2100862
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Message-Id: <20220628115418.5376-2-lersek@redhat.com>
Reviewed-by: Richard W.M. Jones <rjones@redhat.com>
--- a/docs/guestfs-security.pod
+++ b/docs/guestfs-security.pod
@@ -406,6 +406,34 @@ The libvirt backend is not affected.
The solution is to update qemu to a version containing the fix (see
L<https://lists.gnu.org/archive/html/qemu-devel/2018-06/msg01012.html>).
+=head2 CVE-2022-2211
+
+L<https://bugzilla.redhat.com/CVE-2022-2211>
+
+The C<get_keys> function in F<libguestfs-common/options/keys.c> collects
+those I<--key> options from the command line into a new array that match
+a particular block device that's being decrypted for inspection. The
+function intends to size the result array such that potentially all
+I<--key> options, plus a terminating C<NULL> element, fit into it. The
+code mistakenly uses the C<MIN> macro instead of C<MAX>, and therefore
+only one element is allocated before the C<NULL> terminator.
+
+Passing precisely two I<--key ID:...> options on the command line for
+the encrypted block device C<ID> causes C<get_keys> to overwrite the
+terminating C<NULL>, leading to an out-of-bounds read in
+C<decrypt_mountables>, file F<libguestfs-common/options/decrypt.c>.
+
+Passing more than two I<--key ID:...> options on the command line for
+the encrypted block device C<ID> causes C<get_keys> itself to perform
+out-of-bounds writes. The most common symptom is a crash with C<SIGSEGV>
+later on.
+
+This issue affects -- broadly speaking -- all libguestfs-based utilities
+that accept I<--key>, namely: C<guestfish>, C<guestmount>, C<virt-cat>,
+C<virt-customize>, C<virt-diff>, C<virt-edit>, C<virt-get-kernel>,
+C<virt-inspector>, C<virt-log>, C<virt-ls>, C<virt-sparsify>,
+C<virt-sysprep>, C<virt-tail>, C<virt-v2v>.
+
=head1 SEE ALSO
L<guestfs(3)>,

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CVE-2022-2211-options-fix-buffer-overflow-in-get_keys.patch Normal file
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Subject: options: fix buffer overflow in get_keys() [CVE-2022-2211]
From: Laszlo Ersek lersek@redhat.com Tue Jun 28 13:49:04 2022 +0200
Date: Wed Jun 29 15:17:17 2022 +0200:
Git: 35467027f657de76aca34b48a6f23e9608b23a57
When calculating the greatest possible number of matching keys in
get_keys(), the current expression
MIN (1, ks->nr_keys)
is wrong -- it will return at most 1.
If all "nr_keys" keys match however, then we require "nr_keys" non-NULL
entries in the result array; in other words, we need
MAX (1, ks->nr_keys)
(The comment just above the expression is correct; the code is wrong.)
This buffer overflow is easiest to trigger in those guestfs tools that
parse the "--key" option in C; that is, with "OPTION_key". For example,
the command
$ virt-cat $(seq -f '--key /dev/sda2:key:%g' 200) -d DOMAIN /no-such-file
which passes 200 (different) passphrases for the LUKS-encrypted block
device "/dev/sda2", crashes with a SIGSEGV.
A slightly better reproducer from Rich Jones is the following, since it
doesn't require an encrypted guest disk image:
$ echo TEST | guestfish --keys-from-stdin -N part luks-format /dev/sda1 0
$ virt-cat $(seq -f '--key /dev/sda1:key:%g' 200) -a test1.img /no-such-file
Segmentation fault (core dumped)
$ rm test1.img
(
The buffer overflow is possible to trigger in OCaml-language tools as
well; that is, those that call "create_standard_options" with
~key_opts:true.
Triggering the problem that way is less trivial. The reason is that when
the OCaml tools parse the "--key" options, they de-duplicate the options
first, based on the device identifier.
Thus, in theory, this de-duplication masks the issue, as (one would
think) only one "--key" option could belong to a single device, and
therefore the buffer overflow would not be triggered in practice.
This is not the case however: the de-duplication does not collapse keys
that are provided for the same device, but use different identifier
types (such as pathname of device node versus LUKS UUID) -- in that
situation, two entries in the keystore will match the device, and the
terminating NULL entry will not be present once get_keys() returns. In
this scenario, we don't have an out-of-bounds write, but an
out-of-bounds read, in decrypt_mountables() [options/decrypt.c].
There is *yet another* bug in get_keys() though that undoes the above
"masking". The "uuid" parameter of get_keys() may be NULL (for example
when the device to decrypt uses BitLocker and not LUKS). When this
happens, get_keys() adds all keys in the keystore to the result array.
Therefore, the out-of-bounds write is easy to trigger with
OCaml-language tools as well, as long as we attempt to decrypt a
BitLocker (not LUKS) device, and we pass the "--key" options with
different device identifiers.
Subsequent patches in this series fix all of the above; this patch fixes
the security bug.
)
Rather than replacing MIN with MAX, open-code the comparison, as we first
set "len" to 1 anyway.
While at it, rework the NULL-termination such that the (len+1) addition
not go unchecked.
Fixes: c10c8baedb88e7c2988a01b70fc5f81fa8e4885c
Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1809453
Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2100862
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Message-Id: <20220628114915.5030-2-lersek@redhat.com>
Reviewed-by: Richard W.M. Jones <rjones@redhat.com>
--- a/common/options/keys.c
+++ b/common/options/keys.c
@@ -128,17 +128,23 @@ read_first_line_from_file (const char *f
char **
get_keys (struct key_store *ks, const char *device, const char *uuid)
{
- size_t i, j, len;
+ size_t i, j, nmemb;
char **r;
char *s;
/* We know the returned list must have at least one element and not
* more than ks->nr_keys.
*/
- len = 1;
- if (ks)
- len = MIN (1, ks->nr_keys);
- r = calloc (len+1, sizeof (char *));
+ nmemb = 1;
+ if (ks && ks->nr_keys > nmemb)
+ nmemb = ks->nr_keys;
+
+ /* make room for the terminating NULL */
+ if (nmemb == (size_t)-1)
+ error (EXIT_FAILURE, 0, _("size_t overflow"));
+ nmemb++;
+
+ r = calloc (nmemb, sizeof (char *));
if (r == NULL)
error (EXIT_FAILURE, errno, "calloc");

8
libguestfs.changes
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@ -1,3 +1,11 @@
-------------------------------------------------------------------
Wed Jun 29 09:51:03 MDT 2022 - carnold@suse.com
- bsc#1201064 - Libguestfs: Buffer overflow in get_keys leads
to DOS - CVE-2022-2211
CVE-2022-2211-options-fix-buffer-overflow-in-get_keys.patch
CVE-2022-2211-docs-guestfs-security-document.patch
-------------------------------------------------------------------
Fri Jun 3 15:28:15 MDT 2022 - carnold@suse.com

2
libguestfs.spec
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@ -32,6 +32,8 @@ Source100: mount-rootfs-and-chroot.sh
Source101: README
# Patches
Patch1: CVE-2022-2211-options-fix-buffer-overflow-in-get_keys.patch
Patch2: CVE-2022-2211-docs-guestfs-security-document.patch
BuildRequires: bison
BuildRequires: file-devel