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dbus-marshal-validate: Check brackets in signature nest correctly

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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>
This commit is contained in:
Simon McVittie 2022-09-13 15:10:22 +01:00
parent 1ecbbc3760
commit 9d07424e90
1 changed files with 37 additions and 1 deletions
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38
dbus/dbus-marshal-validate.c
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@ -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));