RFR: 8274929: Crash while reading specific clipboard content

[Kevin Rushforth]

On Tue, 9 Nov 2021 23:46:18 GMT, Michael Strauß <mstrauss at openjdk.org> wrote:

>> This bug is caused by not sanity checking the data returned by a call to the Windows Clipboard `IDataObject::GetData` method. When requesting a file descriptor with a format of either `CFSTR_FILEDESCRIPTORA` or `CFSTR_FILEDESCRIPTORW`, which returns a list of file names, the first word of the returned data buffer is supposed to be the number of items that follow. Applications can put data on the clipboard in such a way that it will respond to a request to return the list of files from the clipboard with data that isn't formatted correctly, so we can't assume that the first word is a valid count.
>> 
>> The fix is to check the returned buffer size against the item count. I added a regression test that fails before and passes after the fix.
>
> modules/javafx.graphics/src/main/native-glass/win/GlassClipboard.cpp line 1307:
> 
>> 1305:                         jsize bufferSize = me.size() - sizeof(UINT);
>> 1306:                         if ((pdata->cItems > 0) &&
>> 1307:                             (bufferSize / pdata->cItems >= itemSize))
> 
> Instead of discarding all the data, have you considered reading `min(pdata->cItems, bufferSize / itemSize)` items?

I thought about it, but since failing this test means that `cItems` is invalid, there is no reason to believe that the data that follows it is any less invalid.

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PR: https://git.openjdk.java.net/jfx/pull/662