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Implement AES-GCM with CryptoKit on macOS
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src/libraries/System.Security.Cryptography/src/System/Security/Cryptography/AesGcm.macOS.cs
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,128 @@ | ||
| // Licensed to the .NET Foundation under one or more agreements. | ||
| // The .NET Foundation licenses this file to you under the MIT license. | ||
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| using System.Diagnostics; | ||
| using System.Diagnostics.CodeAnalysis; | ||
| using Microsoft.Win32.SafeHandles; | ||
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| namespace System.Security.Cryptography | ||
| { | ||
| public sealed partial class AesGcm | ||
| { | ||
| // Apple CryptoKit does not support short authentication tags. Since .NET originally supported AES-GCM via | ||
| // OpenSSL, which does support short tags, we need to continue to support them. If a caller supplies a short | ||
| // tag we will continue to use OpenSSL if it is available. Otherwise, use CryptoKit. | ||
| private static readonly bool s_openSslAvailable = Interop.OpenSslNoInit.OpenSslIsAvailable; | ||
| private const int CryptoKitSupportedTagSizeInBytes = 16; | ||
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| private byte[]? _key; | ||
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| // CryptoKit added ChaCha20Poly1305 in macOS 10.15, which is our minimum target for macOS. We still may end | ||
| // up throwing a platform not supported if a caller uses a short authentication tag and OpenSSL is not | ||
| // available. But recommended use of AES-GCM with a 16-byte tag is supported. | ||
| public static bool IsSupported => true; | ||
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| [MemberNotNull(nameof(_key))] | ||
| private void ImportKey(ReadOnlySpan<byte> key) | ||
| { | ||
| // We should only be calling this in the constructor, so there shouldn't be a previous key. | ||
| Debug.Assert(_key is null); | ||
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| // Pin the array on the POH so that the GC doesn't move it around to allow zeroing to be more effective. | ||
| _key = GC.AllocateArray<byte>(key.Length, pinned: true); | ||
| key.CopyTo(_key); | ||
| } | ||
|
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| private void EncryptCore( | ||
| ReadOnlySpan<byte> nonce, | ||
| ReadOnlySpan<byte> plaintext, | ||
| Span<byte> ciphertext, | ||
| Span<byte> tag, | ||
| ReadOnlySpan<byte> associatedData) | ||
| { | ||
| CheckDisposed(); | ||
|
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| if (tag.Length != CryptoKitSupportedTagSizeInBytes) | ||
| { | ||
| using (SafeEvpCipherCtxHandle ctxHandle = CreateOpenSslHandle()) | ||
| { | ||
| AesGcmOpenSslCommon.Encrypt(ctxHandle, nonce, plaintext, ciphertext, tag, associatedData); | ||
| } | ||
| } | ||
| else | ||
| { | ||
| Interop.AppleCrypto.AesGcmEncrypt( | ||
| _key, | ||
| nonce, | ||
| plaintext, | ||
| ciphertext, | ||
| tag, | ||
| associatedData); | ||
| } | ||
| } | ||
|
|
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| private void DecryptCore( | ||
| ReadOnlySpan<byte> nonce, | ||
| ReadOnlySpan<byte> ciphertext, | ||
| ReadOnlySpan<byte> tag, | ||
| Span<byte> plaintext, | ||
| ReadOnlySpan<byte> associatedData) | ||
| { | ||
| CheckDisposed(); | ||
|
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| if (tag.Length != CryptoKitSupportedTagSizeInBytes) | ||
| { | ||
| using (SafeEvpCipherCtxHandle ctxHandle = CreateOpenSslHandle()) | ||
| { | ||
| AesGcmOpenSslCommon.Decrypt(ctxHandle, nonce, ciphertext, tag, plaintext, associatedData); | ||
| } | ||
| } | ||
| else | ||
| { | ||
| Interop.AppleCrypto.AesGcmDecrypt( | ||
| _key, | ||
| nonce, | ||
| ciphertext, | ||
| tag, | ||
| plaintext, | ||
| associatedData); | ||
| } | ||
| } | ||
|
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| public void Dispose() | ||
| { | ||
| CryptographicOperations.ZeroMemory(_key); | ||
| _key = null; | ||
| } | ||
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| [MemberNotNull(nameof(_key))] | ||
| private void CheckDisposed() | ||
| { | ||
| ObjectDisposedException.ThrowIf(_key is null, this); | ||
| } | ||
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| private SafeEvpCipherCtxHandle CreateOpenSslHandle() | ||
| { | ||
| Debug.Assert(_key is not null); | ||
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| // We should only get here if the tag size is not 128-bit. If that happens, and OpenSSL is not available, | ||
| // then we can't proceed. | ||
| if (!s_openSslAvailable) | ||
| { | ||
| throw new PlatformNotSupportedException(SR.PlatformNotSupported_AesGcmTagSize); | ||
| } | ||
|
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| IntPtr cipherHandle = AesGcmOpenSslCommon.GetCipher(_key.Length * 8); | ||
| SafeEvpCipherCtxHandle ctxHandle = Interop.Crypto.EvpCipherCreatePartial(cipherHandle); | ||
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| Interop.Crypto.CheckValidOpenSslHandle(ctxHandle); | ||
| Interop.Crypto.EvpCipherSetKeyAndIV( | ||
| ctxHandle, | ||
| _key, | ||
| Span<byte>.Empty, | ||
| Interop.Crypto.EvpCipherDirection.NoChange); | ||
| Interop.Crypto.EvpCipherSetGcmNonceLength(ctxHandle, NonceSize); | ||
| return ctxHandle; | ||
| } | ||
| } | ||
| } |
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