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Bug #22804: Reject out of bounds XGetImage requests 

The XGetImage man page states:

    If the drawable is a window, the window must be viewable, and it must be the
    case that if there were no inferiors or overlapping windows, the specified
    rectangle of the window would be fully visible on the screen and wholly
    contained within the outside edges of the window, or a BadMatch error
    results.  Note that the borders of the window can be included and read with
    this request.

However, the server was only checking the requested region against the screen
bounds, allowing XGetImage requests to read pixels outside the bounds of a
window's ancestors.  Normally, this would just read other pixels from the
screen, but if one of the ancestor windows is redirected, the window's backing
pixmap may be smaller than the window itself.

This change checks the region against the window's bounding drawable, which is
either the screen pixmap, a redirected window's backing pixmap, or the root
window for servers that don't support GetWindowPixmap.

Signed-off-by: Aaron Plattner <aplattner@nvidia.com>
Reviewed-by: Keith Packard <keithp@keithp.com>
This commit is contained in:
Aaron Plattner 2009-07-22 10:55:46 -07:00
parent ecd618957e
commit 587c3a2d19
1 changed files with 49 additions and 23 deletions
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72
dix/dispatch.c
View File

@ -2062,9 +2062,11 @@ DoGetImage(ClientPtr client, int format, Drawable drawable,
int x, int y, int width, int height, int x, int y, int width, int height,
Mask planemask, xGetImageReply **im_return) Mask planemask, xGetImageReply **im_return)
{ {
DrawablePtr pDraw; DrawablePtr pDraw, pBoundingDraw;
int nlines, linesPerBuf, rc; int nlines, linesPerBuf, rc;
int linesDone; int linesDone;
/* coordinates relative to the bounding drawable */
int relx, rely;
long widthBytesLine, length; long widthBytesLine, length;
Mask plane = 0; Mask plane = 0;
char *pBuf; char *pBuf;
@ -2081,35 +2083,59 @@ DoGetImage(ClientPtr client, int format, Drawable drawable,
return rc; return rc;
memset(&xgi, 0, sizeof(xGetImageReply)); memset(&xgi, 0, sizeof(xGetImageReply));
relx = x;
rely = y;
if(pDraw->type == DRAWABLE_WINDOW) if(pDraw->type == DRAWABLE_WINDOW)
{ {
if( /* check for being viewable */ WindowPtr pWin = (WindowPtr)pDraw;
!((WindowPtr) pDraw)->realized ||
/* check for being on screen */ /* "If the drawable is a window, the window must be viewable ... or a
pDraw->x + x < 0 || * BadMatch error results" */
pDraw->x + x + width > pDraw->pScreen->width || if (!pWin->viewable)
pDraw->y + y < 0 || return BadMatch;
pDraw->y + y + height > pDraw->pScreen->height ||
/* check for being inside of border */ relx += pDraw->x;
x < - wBorderWidth((WindowPtr)pDraw) || rely += pDraw->y;
x + width > wBorderWidth((WindowPtr)pDraw) + (int)pDraw->width ||
y < -wBorderWidth((WindowPtr)pDraw) || if (pDraw->pScreen->GetWindowPixmap) {
y + height > wBorderWidth ((WindowPtr)pDraw) + (int)pDraw->height PixmapPtr pPix = (*pDraw->pScreen->GetWindowPixmap) (pWin);
)
return(BadMatch); pBoundingDraw = &pPix->drawable;
xgi.visual = wVisual (((WindowPtr) pDraw)); #ifdef COMPOSITE
relx -= pPix->screen_x;
rely -= pPix->screen_y;
#endif
}
else
{
pBoundingDraw = (DrawablePtr)WindowTable[pDraw->pScreen->myNum];
}
xgi.visual = wVisual (pWin);
} }
else else
{ {
if(x < 0 || pBoundingDraw = pDraw;
x+width > (int)pDraw->width ||
y < 0 ||
y+height > (int)pDraw->height
)
return(BadMatch);
xgi.visual = None; xgi.visual = None;
} }
/* "If the drawable is a pixmap, the given rectangle must be wholly
* contained within the pixmap, or a BadMatch error results. If the
* drawable is a window [...] it must be the case that if there were no
* inferiors or overlapping windows, the specified rectangle of the window
* would be fully visible on the screen and wholly contained within the
* outside edges of the window, or a BadMatch error results."
*
* We relax the window case slightly to mean that the rectangle must exist
* within the bounds of the window's backing pixmap. In particular, this
* means that a GetImage request may succeed or fail with BadMatch depending
* on whether any of its ancestor windows are redirected. */
if(relx < 0 || relx + width > (int)pBoundingDraw->width ||
rely < 0 || rely + height > (int)pBoundingDraw->height)
return BadMatch;
xgi.type = X_Reply; xgi.type = X_Reply;
xgi.sequenceNumber = client->sequence; xgi.sequenceNumber = client->sequence;
xgi.depth = pDraw->depth; xgi.depth = pDraw->depth;