58 lines
2.3 KiB
Markdown
58 lines
2.3 KiB
Markdown
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## CspParameters.ParentWindowHandle now expects HWND value
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### Scope
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Minor
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### Version Introduced
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4.7
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### Source Analyzer Status
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Investigating
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### Change Description
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The `CspParameters.ParentWindowHandle` value, introduced in .NET Framework 2.0, allows an application to register a parent window handle value such
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that any UI required to access the key (such as a PIN prompt or consent dialog) opens as a modal child to the specified window.
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Starting with apps that target the .NET Framework 4.7, a Windows Forms application can set the CspParameters.ParentWindowHandle property with code like the following:
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```C#
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cspParameters.ParentWindowHandle = form.Handle;
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```
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In previous versions of the .NET Framework, the value was expected to be an IntPtr representing a location in memory where the
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[HWND](https://msdn.microsoft.com/en-us/library/windows/desktop/aa383751(v=vs.85).aspx#HWND) value resided.
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Setting the property to form.Handle on Windows 7 and earlier versions had no effect, but on Windows 8 and later versions, it results in a <20>CryptographicException: The parameter is incorrect.<2E>
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- [X] Quirked
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- [ ] Build-time break
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### Recommended Action
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Applications targeting .NET 4.7 or higher wishing to register a parent window relationship are encouraged to use the simplified form:
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```C#
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cspParameters.ParentWindowHandle = form.Handle;
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```
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Users who had identified that the correct value to pass was the address of a memory location which held the value `form.Handle` can opt out of the
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behavior change by setting the AppContext switch `Switch.System.Security.Cryptography.DoNotAddrOfCspParentWindowHandle` to `true`.
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1. By programmatically setting compat switches on the AppContext, as explained [here](http://blogs.msdn.com/b/dotnet/archive/2015/04/29/net-announcements-at-build-2015.aspx#dotnet46)
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2. By adding the following line to the `<runtime>` section of the app.config file:
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```xml
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<runtime>
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<AppContextSwitchOverrides value="Switch.System.Security.Cryptography.DoNotAddrOfCspParentWindowHandle=true"/>
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</runtime>
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```
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Conversely, users who wish to opt in to the new behavior on the .NET Framework 4.7 runtime when the application loads under older .NET Framework versions
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can set the AppContext switch to `false`.
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### Affected APIs
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* `P:System.Security.Cryptography.CspParameters.ParentWindowHandle`
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### Category
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Security
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<!-- breaking change id: 178 -->
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