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shell32/autocomplete: Fix a vulnerability by avoiding the use of snprintf. 

The quickComplete format can have more than one % argument, or stuff like
%*.* or %1234s, which can be exploited since the format string can be read
from the registry, so handle it manually instead of using sprintf.

Signed-off-by: Gabriel Ivăncescu <gabrielopcode@gmail.com>
Signed-off-by: Huw Davies <huw@codeweavers.com>
Signed-off-by: Alexandre Julliard <julliard@winehq.org>
This commit is contained in:
Gabriel Ivăncescu 2018-09-10 22:09:31 +03:00 committed by Alexandre Julliard
parent be3a3ad825
commit 74c0c0574e
1 changed files with 36 additions and 6 deletions
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42
dlls/shell32/autocomplete.c
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@ -93,6 +93,32 @@ static inline IAutoCompleteImpl *impl_from_IAutoCompleteDropDown(IAutoCompleteDr
return CONTAINING_RECORD(iface, IAutoCompleteImpl, IAutoCompleteDropDown_iface);
}
static size_t format_quick_complete(WCHAR *dst, const WCHAR *qc, const WCHAR *str, size_t str_len)
{
/* Replace the first %s directly without using snprintf, to avoid
exploits since the format string can be retrieved from the registry */
WCHAR *base = dst;
UINT args = 0;
while (*qc != '\0')
{
if (qc[0] == '%')
{
if (args < 1 && qc[1] == 's')
{
memcpy(dst, str, str_len * sizeof(WCHAR));
dst += str_len;
qc += 2;
args++;
continue;
}
qc += (qc[1] == '%');
}
*dst++ = *qc++;
}
*dst = '\0';
return dst - base;
}
static void destroy_autocomplete_object(IAutoCompleteImpl *ac)
{
ac->hwndEdit = NULL;
@ -109,7 +135,6 @@ static LRESULT APIENTRY ACEditSubclassProc(HWND hwnd, UINT uMsg, WPARAM wParam,
IAutoCompleteImpl *This = GetPropW(hwnd, autocomplete_propertyW);
HRESULT hr;
WCHAR hwndText[255];
WCHAR *hwndQCText;
RECT r;
BOOL control, filled, displayall = FALSE;
int cpt, height, sel;
@ -138,11 +163,16 @@ static LRESULT APIENTRY ACEditSubclassProc(HWND hwnd, UINT uMsg, WPARAM wParam,
/* If quickComplete is set and control is pressed, replace the string */
control = GetKeyState(VK_CONTROL) & 0x8000;
if (control && This->quickComplete) {
hwndQCText = heap_alloc((lstrlenW(This->quickComplete)+lstrlenW(hwndText))*sizeof(WCHAR));
sel = sprintfW(hwndQCText, This->quickComplete, hwndText);
SendMessageW(hwnd, WM_SETTEXT, 0, (LPARAM)hwndQCText);
SendMessageW(hwnd, EM_SETSEL, 0, sel);
heap_free(hwndQCText);
WCHAR *buf;
size_t len = strlenW(hwndText);
size_t sz = strlenW(This->quickComplete) + 1 + len;
if ((buf = heap_alloc(sz * sizeof(WCHAR))))
{
len = format_quick_complete(buf, This->quickComplete, hwndText, len);
SendMessageW(hwnd, WM_SETTEXT, 0, (LPARAM)buf);
SendMessageW(hwnd, EM_SETSEL, 0, len);
heap_free(buf);
}
}
ShowWindow(This->hwndListBox, SW_HIDE);