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AesGcm.OpenSsl.cs
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/
AesGcm.OpenSsl.cs
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// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
using System.Diagnostics;
using System.Diagnostics.CodeAnalysis;
using Microsoft.Win32.SafeHandles;
namespace System.Security.Cryptography
{
public sealed partial class AesGcm
{
private SafeEvpCipherCtxHandle _ctxHandle;
public static bool IsSupported { get; } = Interop.OpenSslNoInit.OpenSslIsAvailable;
public static KeySizes TagByteSizes { get; } = new KeySizes(12, 16, 1);
[MemberNotNull(nameof(_ctxHandle))]
private void ImportKey(ReadOnlySpan<byte> key)
{
_ctxHandle = Interop.Crypto.EvpCipherCreatePartial(GetCipher(key.Length * 8));
Interop.Crypto.CheckValidOpenSslHandle(_ctxHandle);
Interop.Crypto.EvpCipherSetKeyAndIV(
_ctxHandle,
key,
Span<byte>.Empty,
Interop.Crypto.EvpCipherDirection.NoChange);
Interop.Crypto.EvpCipherSetGcmNonceLength(_ctxHandle, NonceSize);
}
private void EncryptCore(
ReadOnlySpan<byte> nonce,
ReadOnlySpan<byte> plaintext,
Span<byte> ciphertext,
Span<byte> tag,
ReadOnlySpan<byte> associatedData = default)
{
Interop.Crypto.EvpCipherSetKeyAndIV(
_ctxHandle,
Span<byte>.Empty,
nonce,
Interop.Crypto.EvpCipherDirection.Encrypt);
if (associatedData.Length != 0)
{
if (!Interop.Crypto.EvpCipherUpdate(_ctxHandle, Span<byte>.Empty, out _, associatedData))
{
throw Interop.Crypto.CreateOpenSslCryptographicException();
}
}
if (!Interop.Crypto.EvpCipherUpdate(_ctxHandle, ciphertext, out int ciphertextBytesWritten, plaintext))
{
throw Interop.Crypto.CreateOpenSslCryptographicException();
}
if (!Interop.Crypto.EvpCipherFinalEx(
_ctxHandle,
ciphertext.Slice(ciphertextBytesWritten),
out int bytesWritten))
{
throw Interop.Crypto.CreateOpenSslCryptographicException();
}
ciphertextBytesWritten += bytesWritten;
if (ciphertextBytesWritten != ciphertext.Length)
{
Debug.Fail($"GCM encrypt wrote {ciphertextBytesWritten} of {ciphertext.Length} bytes.");
throw new CryptographicException();
}
Interop.Crypto.EvpCipherGetGcmTag(_ctxHandle, tag);
}
private void DecryptCore(
ReadOnlySpan<byte> nonce,
ReadOnlySpan<byte> ciphertext,
ReadOnlySpan<byte> tag,
Span<byte> plaintext,
ReadOnlySpan<byte> associatedData)
{
Interop.Crypto.EvpCipherSetKeyAndIV(
_ctxHandle,
ReadOnlySpan<byte>.Empty,
nonce,
Interop.Crypto.EvpCipherDirection.Decrypt);
if (associatedData.Length != 0)
{
if (!Interop.Crypto.EvpCipherUpdate(_ctxHandle, Span<byte>.Empty, out _, associatedData))
{
throw Interop.Crypto.CreateOpenSslCryptographicException();
}
}
if (!Interop.Crypto.EvpCipherUpdate(_ctxHandle, plaintext, out int plaintextBytesWritten, ciphertext))
{
throw Interop.Crypto.CreateOpenSslCryptographicException();
}
Interop.Crypto.EvpCipherSetGcmTag(_ctxHandle, tag);
if (!Interop.Crypto.EvpCipherFinalEx(
_ctxHandle,
plaintext.Slice(plaintextBytesWritten),
out int bytesWritten))
{
CryptographicOperations.ZeroMemory(plaintext);
throw new AuthenticationTagMismatchException();
}
plaintextBytesWritten += bytesWritten;
if (plaintextBytesWritten != plaintext.Length)
{
Debug.Fail($"GCM decrypt wrote {plaintextBytesWritten} of {plaintext.Length} bytes.");
throw new CryptographicException();
}
}
private static IntPtr GetCipher(int keySizeInBits)
{
switch (keySizeInBits)
{
case 128: return Interop.Crypto.EvpAes128Gcm();
case 192: return Interop.Crypto.EvpAes192Gcm();
case 256: return Interop.Crypto.EvpAes256Gcm();
default:
Debug.Fail("Key size should already be validated");
return IntPtr.Zero;
}
}
public void Dispose()
{
_ctxHandle.Dispose();
}
}
}