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Add support for AES encryption and key wrap algorithms (#16025)
* Add oct-HSM key type Resolves #14887 * Add additional encryption algorithms to Keys Resolves #14888 * Add AES-CBC and AES-GCM implementations/proxies * Add AES support to AesCryptographyProvider * Use factory methods for encrypt/decrypt options * Update public API
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‎sdk/keyvault/Azure.Security.KeyVault.Keys/CHANGELOG.md‎

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## 4.2.0-beta.3 (Unreleased)
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### Added
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- Added `KeyType.OctHsm` to support "oct-HSM" key operations.
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- Added AES-GCM and AES-CBC support for encrypting and decrypting.
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## 4.2.0-beta.2 (2020-10-06)
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‎sdk/keyvault/Azure.Security.KeyVault.Keys/api/Azure.Security.KeyVault.Keys.netstandard2.0.cs‎

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‎sdk/keyvault/Azure.Security.KeyVault.Keys/src/Cryptography/AesCbc.cs‎

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// Copyright (c) Microsoft Corporation. All rights reserved.
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// Licensed under the MIT License.
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using System.Security.Cryptography;
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namespace Azure.Security.KeyVault.Keys.Cryptography
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{
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/// <summary>
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/// Copied from Microsoft.Azure.KeyVault.Cryptography for vanilla AESCBC as defined in https://tools.ietf.org/html/rfc3394
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/// </summary>
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internal class AesCbc
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{
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public const int BlockByteSize = 16;
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public static readonly AesCbc Aes128Cbc = new AesCbc("A128CBC", 128, PaddingMode.Zeros);
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public static readonly AesCbc Aes192Cbc = new AesCbc("A192CBC", 192, PaddingMode.Zeros);
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public static readonly AesCbc Aes256Cbc = new AesCbc("A256CBC", 256, PaddingMode.Zeros);
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public static readonly AesCbc Aes128CbcPad = new AesCbc("A128CBCPAD", 128, PaddingMode.PKCS7);
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public static readonly AesCbc Aes192CbcPad = new AesCbc("A192CBCPAD", 192, PaddingMode.PKCS7);
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public static readonly AesCbc Aes256CbcPad = new AesCbc("A256CBCPAD", 256, PaddingMode.PKCS7);
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private AesCbc(string name, int keySize, PaddingMode padding)
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{
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Name = name;
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KeySizeInBytes = keySize >> 3;
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Padding = padding;
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}
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public string Name { get; }
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public int KeySizeInBytes { get; }
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public PaddingMode Padding { get; }
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private static Aes Create( byte[] key, byte[] iv, PaddingMode padding )
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{
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var aes = Aes.Create();
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aes.Mode = CipherMode.CBC;
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aes.Padding = padding;
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aes.KeySize = key.Length * 8;
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aes.Key = key;
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aes.IV = iv;
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return aes;
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}
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public ICryptoTransform CreateDecryptor( byte[] key, byte[] iv )
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{
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if ( key == null )
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throw new CryptographicException( "No key material" );
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if (key.Length < KeySizeInBytes)
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throw new CryptographicException("key", $"key must be at least {KeySizeInBytes << 3} bits");
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if ( iv == null )
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throw new CryptographicException( "No initialization vector" );
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// Create the AES provider
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using ( var aes = Create( key.Take(KeySizeInBytes), iv, Padding ) )
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{
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return aes.CreateDecryptor();
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}
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}
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public ICryptoTransform CreateEncryptor( byte[] key, byte[] iv )
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{
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if ( key == null )
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throw new CryptographicException( "No key material" );
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if (key.Length < KeySizeInBytes)
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throw new CryptographicException("key", $"key must be at least {KeySizeInBytes << 3} bits");
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if ( iv == null )
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throw new CryptographicException( "No initialization vector" );
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// Create the AES provider
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using ( var aes = Create( key.Take(KeySizeInBytes), iv, Padding ) )
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{
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return aes.CreateEncryptor();
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}
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}
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}
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}

‎sdk/keyvault/Azure.Security.KeyVault.Keys/src/Cryptography/AesCryptographyProvider.cs‎

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@@ -18,7 +18,7 @@ public override bool SupportsOperation(KeyOperation operation)
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{
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if (KeyMaterial != null)
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{
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if (operation == KeyOperation.WrapKey || operation == KeyOperation.UnwrapKey)
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if (operation == KeyOperation.Encrypt || operation == KeyOperation.Decrypt || operation == KeyOperation.WrapKey || operation == KeyOperation.UnwrapKey)
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{
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return KeyMaterial.SupportsOperation(operation);
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}
@@ -27,26 +27,122 @@ public override bool SupportsOperation(KeyOperation operation)
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return false;
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}
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public override DecryptResult Decrypt(DecryptOptions options, CancellationToken cancellationToken = default)
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{
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Argument.AssertNotNull(options, nameof(options));
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ThrowIfTimeInvalid();
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EncryptionAlgorithm algorithm = options.Algorithm;
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if (algorithm.GetAesCbcEncryptionAlgorithm() is AesCbc aesCbc)
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{
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using ICryptoTransform decryptor = aesCbc.CreateDecryptor(KeyMaterial.K, options.Iv);
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byte[] ciphertext = options.Ciphertext;
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byte[] plaintext = decryptor.TransformFinalBlock(ciphertext, 0, ciphertext.Length);
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return new DecryptResult
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{
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Algorithm = algorithm,
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KeyId = KeyMaterial.Id,
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Plaintext = plaintext,
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};
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}
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else if (algorithm.IsAesGcm() && AesGcmProxy.TryCreate(KeyMaterial.K, out AesGcmProxy aesGcm))
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{
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using (aesGcm)
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{
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byte[] ciphertext = options.Ciphertext;
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byte[] plaintext = new byte[ciphertext.Length];
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aesGcm.Decrypt(options.Iv, ciphertext, options.AuthenticationTag, plaintext, options.AdditionalAuthenticatedData);
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return new DecryptResult
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{
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Algorithm = algorithm,
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KeyId = KeyMaterial.Id,
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Plaintext = plaintext,
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};
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}
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}
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else
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{
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KeysEventSource.Singleton.AlgorithmNotSupported(nameof(Decrypt), algorithm);
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return null;
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}
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}
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public override EncryptResult Encrypt(EncryptOptions options, CancellationToken cancellationToken = default)
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{
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Argument.AssertNotNull(options, nameof(options));
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ThrowIfTimeInvalid();
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EncryptionAlgorithm algorithm = options.Algorithm;
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if (algorithm.GetAesCbcEncryptionAlgorithm() is AesCbc aesCbc)
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{
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using ICryptoTransform encryptor = aesCbc.CreateEncryptor(KeyMaterial.K, options.Iv);
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byte[] plaintext = options.Plaintext;
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byte[] ciphertext = encryptor.TransformFinalBlock(plaintext, 0, plaintext.Length);
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return new EncryptResult
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{
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Algorithm = algorithm,
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KeyId = KeyMaterial.Id,
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Ciphertext = ciphertext,
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Iv = options.Iv,
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};
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}
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else if (algorithm.IsAesGcm() && AesGcmProxy.TryCreate(KeyMaterial.K, out AesGcmProxy aesGcm))
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{
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using (aesGcm)
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{
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byte[] plaintext = options.Plaintext;
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byte[] ciphertext = new byte[plaintext.Length];
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byte[] tag = new byte[AesGcmProxy.NonceByteSize];
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// Generate an nonce only for local AES-GCM; Managed HSM will do it service-side and err if serialized.
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byte[] iv = Crypto.GenerateIv(AesGcmProxy.NonceByteSize);
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aesGcm.Encrypt(iv, plaintext, ciphertext, tag, options.AdditionalAuthenticatedData);
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return new EncryptResult
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{
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Algorithm = algorithm,
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KeyId = KeyMaterial.Id,
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Ciphertext = ciphertext,
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Iv = iv,
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AuthenticationTag = tag,
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AdditionalAuthenticatedData = options.AdditionalAuthenticatedData,
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};
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}
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}
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else
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{
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KeysEventSource.Singleton.AlgorithmNotSupported(nameof(Encrypt), algorithm);
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return null;
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}
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}
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public override UnwrapResult UnwrapKey(KeyWrapAlgorithm algorithm, byte[] encryptedKey, CancellationToken cancellationToken)
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{
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Argument.AssertNotNull(encryptedKey, nameof(encryptedKey));
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34-
int algorithmKeySizeBytes = algorithm.GetKeySizeInBytes();
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if (algorithmKeySizeBytes == 0)
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AesKw keyWrapAlgorithm = algorithm.GetAesKeyWrapAlgorithm();
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if (keyWrapAlgorithm == null)
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{
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KeysEventSource.Singleton.AlgorithmNotSupported(nameof(UnwrapKey), algorithm);
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return null;
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}
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int keySizeBytes = GetKeySizeInBytes();
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if (keySizeBytes < algorithmKeySizeBytes)
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if (keySizeBytes < keyWrapAlgorithm.KeySizeInBytes)
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{
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throw new ArgumentException($"Key wrap algorithm {algorithm} key size {algorithmKeySizeBytes} is greater than the underlying key size {keySizeBytes}");
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throw new ArgumentException($"Key wrap algorithm {algorithm} key size {keyWrapAlgorithm.KeySizeInBytes} is greater than the underlying key size {keySizeBytes}");
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}
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byte[] sizedKey = (keySizeBytes == algorithmKeySizeBytes) ? KeyMaterial.K : KeyMaterial.K.Take(algorithmKeySizeBytes);
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using ICryptoTransform decryptor = AesKw.CreateDecryptor(sizedKey);
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using ICryptoTransform decryptor = keyWrapAlgorithm.CreateDecryptor(KeyMaterial.K);
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byte[] key = decryptor.TransformFinalBlock(encryptedKey, 0, encryptedKey.Length);
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return new UnwrapResult
@@ -63,22 +159,20 @@ public override WrapResult WrapKey(KeyWrapAlgorithm algorithm, byte[] key, Cance
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ThrowIfTimeInvalid();
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int algorithmKeySizeBytes = algorithm.GetKeySizeInBytes();
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if (algorithmKeySizeBytes == 0)
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AesKw keyWrapAlgorithm = algorithm.GetAesKeyWrapAlgorithm();
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if (keyWrapAlgorithm == null)
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{
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KeysEventSource.Singleton.AlgorithmNotSupported(nameof(WrapKey), algorithm);
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return null;
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}
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int keySizeBytes = GetKeySizeInBytes();
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if (keySizeBytes < algorithmKeySizeBytes)
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if (keySizeBytes < keyWrapAlgorithm.KeySizeInBytes)
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{
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throw new ArgumentException($"Key wrap algorithm {algorithm} key size {algorithmKeySizeBytes} is greater than the underlying key size {keySizeBytes}");
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throw new ArgumentException($"Key wrap algorithm {algorithm} key size {keyWrapAlgorithm.KeySizeInBytes} is greater than the underlying key size {keySizeBytes}");
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}
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79-
byte[] sizedKey = (keySizeBytes == algorithmKeySizeBytes) ? KeyMaterial.K : KeyMaterial.K.Take(algorithmKeySizeBytes);
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using ICryptoTransform encryptor = AesKw.CreateEncryptor(sizedKey);
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using ICryptoTransform encryptor = keyWrapAlgorithm.CreateEncryptor(KeyMaterial.K);
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byte[] encryptedKey = encryptor.TransformFinalBlock(key, 0, key.Length);
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return new WrapResult
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};
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}
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92-
private int GetKeySizeInBits()
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{
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return GetKeySizeInBytes() << 3;
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}
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private int GetKeySizeInBytes()
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{
99188
if (KeyMaterial.K != null)
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}
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return 0;
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}
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}
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}

‎sdk/keyvault/Azure.Security.KeyVault.Keys/src/Cryptography/AesGcmProxy.cs‎

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// Copyright (c) Microsoft Corporation. All rights reserved.
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// Licensed under the MIT License.
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using System;
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using System.Reflection;
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using System.Security.Cryptography;
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namespace Azure.Security.KeyVault.Keys.Cryptography
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{
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/// <summary>
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/// Since System.Security.Cryptography.AesGcm requires targeting netstandard2.1,
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/// for needing this instance only we will proxy calls via reflection instead of multi-targeting.
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/// This feature will light up on netcoreapp3.0 or newer.
14+
/// </summary>
15+
internal class AesGcmProxy : IDisposable
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{
17+
public const int NonceByteSize = 12;
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private static MethodInfo s_decryptMethod;
20+
private static MethodInfo s_encryptMethod;
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22+
private readonly object _aes;
23+
24+
private AesGcmProxy(object aes)
25+
{
26+
_aes = aes ?? throw new ArgumentNullException(nameof(aes));
27+
}
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29+
public static bool TryCreate(byte[] key, out AesGcmProxy proxy)
30+
{
31+
Type t = typeof(Aes).Assembly.GetType("System.Security.Cryptography.AesGcm", false);
32+
if (t != null)
33+
{
34+
try
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{
36+
object aes = Activator.CreateInstance(t, key);
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38+
proxy = new AesGcmProxy(aes);
39+
return true;
40+
}
41+
catch
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{
43+
}
44+
}
45+
46+
proxy = null;
47+
return false;
48+
}
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50+
public void Decrypt(byte[] nonce, byte[] ciphertext, byte[] tag, byte[] plaintext, byte[] associatedData = default)
51+
{
52+
if (s_decryptMethod is null)
53+
{
54+
s_decryptMethod = _aes.GetType().GetMethod(nameof(Decrypt), new Type[] { typeof(byte[]), typeof(byte[]), typeof(byte[]), typeof(byte[]), typeof(byte[]) }) ??
55+
throw new InvalidOperationException($"{nameof(Decrypt)} method not found");
56+
}
57+
58+
s_decryptMethod.Invoke(_aes, new object[] { nonce, ciphertext, tag, plaintext, associatedData });
59+
}
60+
61+
public void Encrypt(byte[] nonce, byte[] plaintext, byte[] ciphertext, byte[] tag, byte[] associatedData = default)
62+
{
63+
if (s_encryptMethod is null)
64+
{
65+
s_encryptMethod = _aes.GetType().GetMethod(nameof(Encrypt), new Type[] { typeof(byte[]), typeof(byte[]), typeof(byte[]), typeof(byte[]), typeof(byte[]) }) ??
66+
throw new InvalidOperationException($"{nameof(Encrypt)} method not found");
67+
}
68+
69+
s_encryptMethod.Invoke(_aes, new object[] { nonce, plaintext, ciphertext, tag, associatedData });
70+
}
71+
72+
public void Dispose() => ((IDisposable)_aes)?.Dispose();
73+
}
74+
}

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