hivex/0001-lib-node.c-Limit-recursion-in-ri-records-CVE-2021-36.patch

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3.3 KiB
Diff

From 771728218dac2fbf6997a7e53225e75a4c6b7255 Mon Sep 17 00:00:00 2001
From: "Richard W.M. Jones" <rjones@redhat.com>
Date: Thu, 8 Jul 2021 19:00:45 +0100
Subject: [PATCH] lib/node.c: Limit recursion in ri-records (CVE-2021-3622)
Windows Registry hive "ri"-records are arbitrarily nested B-tree-like
structures:
+-------------+
| ri |
|-------------|
| nr_offsets |
| offset[0] ------> points to another lf/lh/li/ri block
| offset[1] ------>
| offset[2] ------>
+-------------+
It is possible to construct a hive with a very deeply nested tree of
ri-records, causing the internal _get_children function to recurse to
any depth which can cause programs linked to hivex to crash with a
stack overflow.
Since it is not thought that deeply nested ri-records occur in real
hives, limit recursion depth. If you hit this limit you will see the
following error and the operation will return an error instead of
crashing:
\> ls
hivex: _get_children: returning EINVAL because: ri-record nested to depth >= 32
ls: Invalid argument
Thanks to Jeremy Galindo for finding and reporting this bug.
Reported-by: Jeremy Galindo, Sr Security Engineer, Datto.com
Signed-off-by: Richard W.M. Jones <rjones@redhat.com>
Fixes: CVE-2021-3622
Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=1975489
(cherry picked from commit 781a12c4a49dd81365c9c567c5aa5e19e894ba0e)
---
lib/node.c | 18 ++++++++++++++----
1 file changed, 14 insertions(+), 4 deletions(-)
diff --git a/lib/node.c b/lib/node.c
index 7b002a46..eb7fe93c 100644
--- a/lib/node.c
+++ b/lib/node.c
@@ -203,7 +203,7 @@ hivex_node_classname (hive_h *h, hive_node_h node)
static int _get_children (hive_h *h, hive_node_h blkoff,
offset_list *children, offset_list *blocks,
- int flags);
+ int flags, unsigned depth);
static int check_child_is_nk_block (hive_h *h, hive_node_h child, int flags);
/* Iterate over children (ie. subkeys of a node), returning child
@@ -335,7 +335,7 @@ _hivex_get_children (hive_h *h, hive_node_h node,
goto error;
}
- if (_get_children (h, subkey_lf, &children, &blocks, flags) == -1)
+ if (_get_children (h, subkey_lf, &children, &blocks, flags, 0) == -1)
goto error;
/* Check the number of children we ended up reading matches
@@ -383,7 +383,7 @@ _hivex_get_children (hive_h *h, hive_node_h node,
static int
_get_children (hive_h *h, hive_node_h blkoff,
offset_list *children, offset_list *blocks,
- int flags)
+ int flags, unsigned depth)
{
/* Add this intermediate block. */
if (_hivex_add_to_offset_list (blocks, blkoff) == -1)
@@ -486,7 +486,17 @@ _get_children (hive_h *h, hive_node_h blkoff,
}
}
- if (_get_children (h, offset, children, blocks, flags) == -1)
+ /* Although in theory hive ri records might be nested to any
+ * depth, in practice this is unlikely. Recursing here caused
+ * CVE-2021-3622. Thus limit the depth we will recurse to
+ * something small.
+ */
+ if (depth >= 32) {
+ SET_ERRNO (EINVAL, "ri-record nested to depth >= %u", depth);
+ return -1;
+ }
+
+ if (_get_children (h, offset, children, blocks, flags, depth+1) == -1)
return -1;
}
}
--
2.32.0