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- CVE-2022-2211 - Fix buffer overflow in get_keys()

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CVE-2022-2211-options-fix-buffer-overflow-in-get_keys.patch

OBS-URL: https://build.opensuse.org/package/show/Virtualization/virt-v2v?expand=0&rev=27
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Charles Arnold 2022-06-29 16:21:52 +00:00 committed by Git OBS Bridge
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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");

6
virt-v2v.changes
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@ -1,3 +1,9 @@
-------------------------------------------------------------------
Wed Jun 29 09:51:03 MDT 2022 - carnold@suse.com
- CVE-2022-2211 - Fix buffer overflow in get_keys()
CVE-2022-2211-options-fix-buffer-overflow-in-get_keys.patch
-------------------------------------------------------------------
Thu May 26 11:39:38 MDT 2022 - carnold@suse.com

2
virt-v2v.spec
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@ -30,6 +30,7 @@ Group: System/Management
URL: https://github.com/libguestfs/virt-v2v
Source0: https://download.libguestfs.org/virt-v2v/%{source_directory}/%{name}-%{version}.tar.gz
Source1: https://download.libguestfs.org/virt-v2v/%{source_directory}/%{name}-%{version}.tar.gz.sig
Patch1: CVE-2022-2211-options-fix-buffer-overflow-in-get_keys.patch
BuildRequires: augeas-devel
BuildRequires: file-devel
#BuildRequires: /usr/bin/pod2man
@ -38,6 +39,7 @@ BuildRequires: gettext-devel
BuildRequires: glib2-devel
BuildRequires: libguestfs-devel >= 1.42
BuildRequires: libjansson-devel
BuildRequires: libnbd
BuildRequires: libosinfo-devel
BuildRequires: libvirt-devel
BuildRequires: libxml2-devel