From 8f382ee405ec68850866298ba0574f12e261a6fa Mon Sep 17 00:00:00 2001 From: Simon McVittie 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 (cherry picked from commit 9d07424e9011e3bbe535e83043d335f3093d2916) (cherry picked from commit 3e53a785dee8d1432156188a2c4260e4cbc78c4d) --- 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)); -- GitLab