CA2101: Specify marshalling for P/Invoke string arguments
Property | Value |
---|---|
Rule ID | CA2101 |
Title | Specify marshalling for P/Invoke string arguments |
Category | Globalization |
Fix is breaking or non-breaking | Non-breaking |
Enabled by default in .NET 8 | As suggestion |
Cause
A platform invoke member allows for partially trusted callers, has a string parameter, and does not explicitly marshal the string.
Rule description
When you convert from Unicode to ANSI, it is possible that not all Unicode characters can be represented in a specific ANSI code page. Best-fit mapping tries to solve this problem by substituting a character for the character that cannot be represented. The use of this feature can cause a potential security vulnerability because you cannot control the character that is chosen. For example, malicious code could intentionally create a Unicode string that contains characters that are not found in a particular code page, which are converted to file system special characters such as '..' or '/'. Note also that security checks for special characters frequently occur before the string is converted to ANSI.
Best-fit mapping is the default for the unmanaged conversion, WChar to MByte. Unless you explicitly disable best-fit mapping, your code might contain an exploitable security vulnerability because of this issue.
Caution
Code Access Security (CAS) should not be considered a security boundary.
How to fix violations
To fix a violation of this rule, explicitly marshal string data types.
When to suppress warnings
Do not suppress a warning from this rule.
Example
The following example shows a method that violates this rule, and then shows how to fix the violation.
class NativeMethods
{
// Violates rule: SpecifyMarshalingForPInvokeStringArguments.
[DllImport("advapi32.dll", CharSet = CharSet.Auto)]
internal static extern int RegCreateKey(IntPtr key, String subKey, out IntPtr result);
// Satisfies rule: SpecifyMarshalingForPInvokeStringArguments.
[DllImport("advapi32.dll", CharSet = CharSet.Unicode)]
internal static extern int RegCreateKey2(IntPtr key, String subKey, out IntPtr result);
}
Friend Class NativeMethods
' Violates rule: SpecifyMarshalingForPInvokeStringArguments.
<DllImport("advapi32.dll", CharSet:=CharSet.Auto)>
Friend Shared Function RegCreateKey(ByVal key As IntPtr, ByVal subKey As String, <Out> ByRef result As IntPtr) As Integer
End Function
' Satisfies rule: SpecifyMarshalingForPInvokeStringArguments.
<DllImport("advapi32.dll", CharSet:=CharSet.Unicode)>
Friend Shared Function RegCreateKey2(ByVal key As IntPtr, ByVal subKey As String, <Out> ByRef result As IntPtr) As Integer
End Function
End Class