private static SecureLocalAllocHandle Protect(byte *pbPlaintext, uint cbPlaintext)
{
// If we're not running on a platform that supports CryptProtectMemory,
// shove the plaintext directly into a LocalAlloc handle. Ideally we'd
// mark this memory page as non-pageable, but this is fraught with peril.
if (!OSVersionUtil.IsWindows())
{
SecureLocalAllocHandle handle = SecureLocalAllocHandle.Allocate((IntPtr) checked ((int)cbPlaintext));
UnsafeBufferUtil.BlockCopy(from: pbPlaintext, to: handle, byteCount: cbPlaintext);
return(handle);
}
// We need to make sure we're a multiple of CRYPTPROTECTMEMORY_BLOCK_SIZE.
uint numTotalBytesToAllocate = cbPlaintext;
uint numBytesPaddingRequired = CRYPTPROTECTMEMORY_BLOCK_SIZE - (numTotalBytesToAllocate % CRYPTPROTECTMEMORY_BLOCK_SIZE);
if (numBytesPaddingRequired == CRYPTPROTECTMEMORY_BLOCK_SIZE)
{
numBytesPaddingRequired = 0; // we're already a proper multiple of the block size
}
checked { numTotalBytesToAllocate += numBytesPaddingRequired; }
CryptoUtil.Assert(numTotalBytesToAllocate % CRYPTPROTECTMEMORY_BLOCK_SIZE == 0, "numTotalBytesToAllocate % CRYPTPROTECTMEMORY_BLOCK_SIZE == 0");
// Allocate and copy plaintext data; padding is uninitialized / undefined.
SecureLocalAllocHandle encryptedMemoryHandle = SecureLocalAllocHandle.Allocate((IntPtr)numTotalBytesToAllocate);
UnsafeBufferUtil.BlockCopy(from: pbPlaintext, to: encryptedMemoryHandle, byteCount: cbPlaintext);
// Finally, CryptProtectMemory the whole mess.
if (numTotalBytesToAllocate != 0)
{
MemoryProtection.CryptProtectMemory(encryptedMemoryHandle, byteCount: numTotalBytesToAllocate);
}
return(encryptedMemoryHandle);
}
public void Duplicate_Copies_Data()
{
// Arrange
const string expected = "xyz";
int cbExpected = expected.Length * sizeof(char);
var controlHandle = SecureLocalAllocHandle.Allocate((IntPtr)cbExpected);
for (int i = 0; i < expected.Length; i++)
{
((char *)controlHandle.DangerousGetHandle())[i] = expected[i];
}
// Act
var duplicateHandle = controlHandle.Duplicate();
// Assert
Assert.Equal(expected, new string((char *)duplicateHandle.DangerousGetHandle(), 0, expected.Length)); // contents the same data
Assert.NotEqual(controlHandle.DangerousGetHandle(), duplicateHandle.DangerousGetHandle()); // shouldn't just point to the same memory location
}
private static LocalAllocHandle LocalAlloc(int cb)
{
return(SecureLocalAllocHandle.Allocate((IntPtr)cb));
}