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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.Runtime.Versioning;
using Internal.Cryptography;
namespace System.Security.Cryptography
{
[UnsupportedOSPlatform("browser")]
[UnsupportedOSPlatform("ios")]
[UnsupportedOSPlatform("tvos")]
public sealed partial class AesGcm : IDisposable
{
private const int NonceSize = 12;
public static KeySizes NonceByteSizes { get; } = new KeySizes(NonceSize, NonceSize, 1);
[Obsolete(Obsoletions.AesGcmTagConstructorMessage, DiagnosticId = Obsoletions.AesGcmTagConstructorDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
public AesGcm(ReadOnlySpan<byte> key)
{
ThrowIfNotSupported();
AesAEAD.CheckKeySize(key.Length);
ImportKey(key);
}
[Obsolete(Obsoletions.AesGcmTagConstructorMessage, DiagnosticId = Obsoletions.AesGcmTagConstructorDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
public AesGcm(byte[] key)
: this(new ReadOnlySpan<byte>(key ?? throw new ArgumentNullException(nameof(key))))
{
}
/// <summary>
/// Initializes a new instance of the <see cref="AesGcm" /> class with a provided key and required tag size.
/// </summary>
/// <param name="key">The secret key to use for this instance.</param>
/// <param name="tagSizeInBytes">The size of the tag, in bytes, that encryption and decryption must use.</param>
/// <exception cref="CryptographicException">
/// The <paramref name="key" /> parameter length is other than 16, 24, or 32 bytes (128, 192, or 256 bits).
/// </exception>
/// <exception cref="ArgumentException">
/// The <paramref name="tagSizeInBytes" /> parameter is an unsupported tag size indicated by
/// <see cref="TagByteSizes" />.
/// </exception>
/// <exception cref="PlatformNotSupportedException">
/// The current platform does not support AES-GCM.
/// </exception>
/// <remarks>
/// The <paramref name="tagSizeInBytes" /> parameter is used to indicate that the tag parameter in <c>Encrypt</c>
/// or <c>Decrypt</c> must be exactly this size. Indicating the required tag size prevents issues where callers
/// of <c>Decrypt</c> may supply a tag as input and that input is truncated to an unexpected size.
/// </remarks>
public AesGcm(ReadOnlySpan<byte> key, int tagSizeInBytes)
{
ThrowIfNotSupported();
AesAEAD.CheckKeySize(key.Length);
if (!tagSizeInBytes.IsLegalSize(TagByteSizes))
{
throw new ArgumentException(SR.Cryptography_InvalidTagLength, nameof(tagSizeInBytes));
}
TagSizeInBytes = tagSizeInBytes;
ImportKey(key);
}
/// <summary>
/// Initializes a new instance of the <see cref="AesGcm" /> class with a provided key and required tag size.
/// </summary>
/// <param name="key">The secret key to use for this instance.</param>
/// <param name="tagSizeInBytes">The size of the tag, in bytes, that encryption and decryption must use.</param>
/// <exception cref="ArgumentNullException">The <paramref name="key" /> parameter is null.</exception>
/// <exception cref="CryptographicException">
/// The <paramref name="key" /> parameter length is other than 16, 24, or 32 bytes (128, 192, or 256 bits).
/// </exception>
/// <exception cref="ArgumentException">
/// The <paramref name="tagSizeInBytes" /> parameter is an unsupported tag size indicated by
/// <see cref="TagByteSizes" />.
/// </exception>
/// <exception cref="PlatformNotSupportedException">
/// The current platform does not support AES-GCM.
/// </exception>
/// <remarks>
/// The <paramref name="tagSizeInBytes" /> parameter is used to indicate that the tag parameter in <c>Encrypt</c>
/// or <c>Decrypt</c> must be exactly this size. Indicating the required tag size prevents issues where callers
/// of <c>Decrypt</c> may supply a tag as input and that input is truncated to an unexpected size.
/// </remarks>
public AesGcm(byte[] key, int tagSizeInBytes)
: this(new ReadOnlySpan<byte>(key ?? throw new ArgumentNullException(nameof(key))), tagSizeInBytes)
{
}
/// <summary>
/// Gets the size of the tag, in bytes.
/// </summary>
/// <value>
/// The size of the tag that must be used for encryption or decryption, or <see langword="null" /> if the
/// tag size is unspecified.
/// </value>
public int? TagSizeInBytes { get; }
public void Encrypt(byte[] nonce, byte[] plaintext, byte[] ciphertext, byte[] tag, byte[]? associatedData = null)
{
ArgumentNullException.ThrowIfNull(nonce);
ArgumentNullException.ThrowIfNull(plaintext);
ArgumentNullException.ThrowIfNull(ciphertext);
ArgumentNullException.ThrowIfNull(tag);
Encrypt((ReadOnlySpan<byte>)nonce, plaintext, ciphertext, tag, associatedData);
}
public void Encrypt(
ReadOnlySpan<byte> nonce,
ReadOnlySpan<byte> plaintext,
Span<byte> ciphertext,
Span<byte> tag,
ReadOnlySpan<byte> associatedData = default)
{
CheckParameters(plaintext, ciphertext, nonce, tag);
EncryptCore(nonce, plaintext, ciphertext, tag, associatedData);
}
public void Decrypt(byte[] nonce, byte[] ciphertext, byte[] tag, byte[] plaintext, byte[]? associatedData = null)
{
ArgumentNullException.ThrowIfNull(nonce);
ArgumentNullException.ThrowIfNull(ciphertext);
ArgumentNullException.ThrowIfNull(tag);
ArgumentNullException.ThrowIfNull(plaintext);
Decrypt((ReadOnlySpan<byte>)nonce, ciphertext, tag, plaintext, associatedData);
}
public void Decrypt(
ReadOnlySpan<byte> nonce,
ReadOnlySpan<byte> ciphertext,
ReadOnlySpan<byte> tag,
Span<byte> plaintext,
ReadOnlySpan<byte> associatedData = default)
{
CheckParameters(plaintext, ciphertext, nonce, tag);
DecryptCore(nonce, ciphertext, tag, plaintext, associatedData);
}
private void CheckParameters(
ReadOnlySpan<byte> plaintext,
ReadOnlySpan<byte> ciphertext,
ReadOnlySpan<byte> nonce,
ReadOnlySpan<byte> tag)
{
if (plaintext.Length != ciphertext.Length)
throw new ArgumentException(SR.Cryptography_PlaintextCiphertextLengthMismatch);
if (!nonce.Length.IsLegalSize(NonceByteSizes))
throw new ArgumentException(SR.Cryptography_InvalidNonceLength, nameof(nonce));
if (TagSizeInBytes is int tagSizeInBytes)
{
// constructor promise
Debug.Assert(tagSizeInBytes.IsLegalSize(TagByteSizes));
if (tag.Length != tagSizeInBytes)
{
throw new ArgumentException(SR.Format(SR.Cryptography_IncorrectTagLength, tagSizeInBytes), nameof(tag));
}
}
else if (!tag.Length.IsLegalSize(TagByteSizes))
{
throw new ArgumentException(SR.Cryptography_InvalidTagLength, nameof(tag));
}
}
private static void ThrowIfNotSupported()
{
if (!IsSupported)
{
throw new PlatformNotSupportedException(SR.Format(SR.Cryptography_AlgorithmNotSupported, nameof(AesGcm)));
}
}
}
}
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