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From 9d07424e9011e3bbe535e83043d335f3093d2916 Mon Sep 17 00:00:00 2001
From: Simon McVittie <smcv@collabora.com>
Date: Tue, 13 Sep 2022 15:10:22 +0100
Subject: [PATCH] dbus-marshal-validate: Check brackets in signature nest
correctly
In debug builds with assertions enabled, a signature with incorrectly
nested `()` and `{}`, for example `a{i(u}` or `(a{ii)}`, could result
in an assertion failure.
In production builds without assertions enabled, a signature with
incorrectly nested `()` and `{}` could potentially result in a crash
or incorrect message parsing, although we do not have a concrete example
of either of these failure modes.
Thanks: Evgeny Vereshchagin
Resolves: https://gitlab.freedesktop.org/dbus/dbus/-/issues/418
Resolves: CVE-2022-42010
Signed-off-by: Simon McVittie <smcv@collabora.com>
---
dbus/dbus-marshal-validate.c | 38 +++++++++++++++++++++++++++++++++++-
1 file changed, 37 insertions(+), 1 deletion(-)
diff --git a/dbus/dbus-marshal-validate.c b/dbus/dbus-marshal-validate.c
index 4d492f3f3..ae68414dd 100644
--- a/dbus/dbus-marshal-validate.c
+++ b/dbus/dbus-marshal-validate.c
@@ -62,6 +62,8 @@ _dbus_validate_signature_with_reason (const DBusString *type_str,
int element_count;
DBusList *element_count_stack;
+ char opened_brackets[DBUS_MAXIMUM_TYPE_RECURSION_DEPTH * 2 + 1] = { '\0' };
+ char last_bracket;
result = DBUS_VALID;
element_count_stack = NULL;
@@ -93,6 +95,10 @@ _dbus_validate_signature_with_reason (const DBusString *type_str,
while (p != end)
{
+ _dbus_assert (struct_depth + dict_entry_depth >= 0);
+ _dbus_assert (struct_depth + dict_entry_depth < _DBUS_N_ELEMENTS (opened_brackets));
+ _dbus_assert (opened_brackets[struct_depth + dict_entry_depth] == '\0');
+
switch (*p)
{
case DBUS_TYPE_BYTE:
@@ -136,6 +142,10 @@ _dbus_validate_signature_with_reason (const DBusString *type_str,
goto out;
}
+ _dbus_assert (struct_depth + dict_entry_depth >= 1);
+ _dbus_assert (struct_depth + dict_entry_depth < _DBUS_N_ELEMENTS (opened_brackets));
+ _dbus_assert (opened_brackets[struct_depth + dict_entry_depth - 1] == '\0');
+ opened_brackets[struct_depth + dict_entry_depth - 1] = DBUS_STRUCT_BEGIN_CHAR;
break;
case DBUS_STRUCT_END_CHAR:
@@ -151,9 +161,20 @@ _dbus_validate_signature_with_reason (const DBusString *type_str,
goto out;
}
+ _dbus_assert (struct_depth + dict_entry_depth >= 1);
+ _dbus_assert (struct_depth + dict_entry_depth < _DBUS_N_ELEMENTS (opened_brackets));
+ last_bracket = opened_brackets[struct_depth + dict_entry_depth - 1];
+
+ if (last_bracket != DBUS_STRUCT_BEGIN_CHAR)
+ {
+ result = DBUS_INVALID_STRUCT_ENDED_BUT_NOT_STARTED;
+ goto out;
+ }
+
_dbus_list_pop_last (&element_count_stack);
struct_depth -= 1;
+ opened_brackets[struct_depth + dict_entry_depth] = '\0';
break;
case DBUS_DICT_ENTRY_BEGIN_CHAR:
@@ -178,6 +199,10 @@ _dbus_validate_signature_with_reason (const DBusString *type_str,
goto out;
}
+ _dbus_assert (struct_depth + dict_entry_depth >= 1);
+ _dbus_assert (struct_depth + dict_entry_depth < _DBUS_N_ELEMENTS (opened_brackets));
+ _dbus_assert (opened_brackets[struct_depth + dict_entry_depth - 1] == '\0');
+ opened_brackets[struct_depth + dict_entry_depth - 1] = DBUS_DICT_ENTRY_BEGIN_CHAR;
break;
case DBUS_DICT_ENTRY_END_CHAR:
@@ -186,8 +211,19 @@ _dbus_validate_signature_with_reason (const DBusString *type_str,
result = DBUS_INVALID_DICT_ENTRY_ENDED_BUT_NOT_STARTED;
goto out;
}
-
+
+ _dbus_assert (struct_depth + dict_entry_depth >= 1);
+ _dbus_assert (struct_depth + dict_entry_depth < _DBUS_N_ELEMENTS (opened_brackets));
+ last_bracket = opened_brackets[struct_depth + dict_entry_depth - 1];
+
+ if (last_bracket != DBUS_DICT_ENTRY_BEGIN_CHAR)
+ {
+ result = DBUS_INVALID_DICT_ENTRY_ENDED_BUT_NOT_STARTED;
+ goto out;
+ }
+
dict_entry_depth -= 1;
+ opened_brackets[struct_depth + dict_entry_depth] = '\0';
element_count =
_DBUS_POINTER_TO_INT (_dbus_list_pop_last (&element_count_stack));
--
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