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Fix SetConsoleWindowInfo being able to crash ConPTY #13212

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2 commits merged into from
Jun 1, 2022
Merged

Fix SetConsoleWindowInfo being able to crash ConPTY #13212

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02ab51d
Fix SetConsoleWindowInfo being able to crash ConPTY
lhecker May 31, 2022
84ccf12
Fix confusion between inclusive/exclusive SMALL_RECT
lhecker Jun 1, 2022
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31 changes: 10 additions & 21 deletions src/host/screenInfo.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -2268,30 +2268,19 @@ void SCREEN_INFORMATION::SetViewport(const Viewport& newViewport,
}

// do adjustments on a copy that's easily manipulated.
auto srCorrected = newViewport.ToExclusive();
const til::rect viewportRect{ newViewport.ToInclusive() };
const til::size coordScreenBufferSize{ GetBufferSize().Dimensions() };

if (srCorrected.Left < 0)
{
srCorrected.Right -= srCorrected.Left;
srCorrected.Left = 0;
}
if (srCorrected.Top < 0)
{
srCorrected.Bottom -= srCorrected.Top;
srCorrected.Top = 0;
}
// MSFT-33471786, GH#13193:
// newViewport may reside anywhere outside of the valid coordScreenBufferSize.
// For instance it might be scrolled down more than our text buffer allows to be scrolled.
const auto cx = gsl::narrow_cast<SHORT>(std::clamp(viewportRect.width(), 1, coordScreenBufferSize.width));
const auto cy = gsl::narrow_cast<SHORT>(std::clamp(viewportRect.height(), 1, coordScreenBufferSize.height));
Comment on lines +2277 to +2278
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Suggested change
const auto cx = gsl::narrow_cast<SHORT>(std::clamp(viewportRect.width(), 1, coordScreenBufferSize.width));
const auto cy = gsl::narrow_cast<SHORT>(std::clamp(viewportRect.height(), 1, coordScreenBufferSize.height));
const auto cx = gsl::narrow_cast<SHORT>(std::clamp(viewportRect.width(), 0, coordScreenBufferSize.width));
const auto cy = gsl::narrow_cast<SHORT>(std::clamp(viewportRect.height(), 0, coordScreenBufferSize.height));

curious, why not allow a width/height of 0?

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@lhecker lhecker Jun 1, 2022 •
edited
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The minimum size the TextBuffer allows is (1,1), so I thought it'd be reasonable if we did the same here.

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A text buffer with a zero dimension would not be a particularly useful text buffer :)

const auto x = gsl::narrow_cast<SHORT>(std::clamp(viewportRect.left, 0, coordScreenBufferSize.width - cx));
const auto y = gsl::narrow_cast<SHORT>(std::clamp(viewportRect.top, 0, coordScreenBufferSize.height - cy));
Comment on lines +2277 to +2280
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@lhecker lhecker May 31, 2022 •
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This function needs to correct the newViewport argument to be within the valid bounds, while retaining the given size as much as possible. If you pass a newViewport with the top/bottom coordinates -130 and -100, it should still result in a viewport that's 30 high, but with a top/bottom of 0 and 30.

I feel like this change increases the robustness of the code by splitting the viewport into its size (cx/cy) and origin (x/y). That way we can first ensure that the size doesn't exceed our limits (just like the old code seemingly intended) and then adjust the origin to be within the smaller rectangle of valid coordinates.

The gsl::narrow_cast<SHORT>s will be removed once my 32-bit coord PR has been merged, but it shouldn't pose a problem here either, as GetBufferSize().Dimensions() is a COORD which can't exceed a SHORT.


const auto coordScreenBufferSize = GetBufferSize().Dimensions();
if (srCorrected.Right > coordScreenBufferSize.X)
{
srCorrected.Right = coordScreenBufferSize.X;
}
if (srCorrected.Bottom > coordScreenBufferSize.Y)
{
srCorrected.Bottom = coordScreenBufferSize.Y;
}
_viewport = Viewport::FromExclusive({ x, y, x + cx, y + cy });

_viewport = Viewport::FromExclusive(srCorrected);
if (updateBottom)
{
UpdateBottom();
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