private byte[]? DeriveSecretAgreement(ECDiffieHellmanPublicKey otherPartyPublicKey, IncrementalHash?hasher)
{
if (!(otherPartyPublicKey is ECDiffieHellmanSecurityTransformsPublicKey secTransPubKey))
{
secTransPubKey =
new ECDiffieHellmanSecurityTransformsPublicKey(otherPartyPublicKey.ExportParameters());
}
try
{
SafeSecKeyRefHandle otherPublic = secTransPubKey.KeyHandle;
if (Interop.AppleCrypto.EccGetKeySizeInBits(otherPublic) != KeySize)
{
throw new ArgumentException(
SR.Cryptography_ArgECDHKeySizeMismatch,
nameof(otherPartyPublicKey));
}
SafeSecKeyRefHandle?thisPrivate = GetKeys().PrivateKey;
if (thisPrivate == null)
{
throw new CryptographicException(SR.Cryptography_CSP_NoPrivateKey);
}
// Since Apple only supports secp256r1, secp384r1, and secp521r1; and 521 fits in
// 66 bytes ((521 + 7) / 8), the Span path will always succeed.
Span <byte> secretSpan = stackalloc byte[66];
byte[]? secret = Interop.AppleCrypto.EcdhKeyAgree(
thisPrivate,
otherPublic,
secretSpan,
out int bytesWritten);
// Either we wrote to the span or we returned an array, but not both, and not neither.
// ("neither" would have thrown)
Debug.Assert(
(bytesWritten == 0) != (secret == null),
$"bytesWritten={bytesWritten}, (secret==null)={secret == null}");
if (hasher == null)
{
return(secret ?? secretSpan.Slice(0, bytesWritten).ToArray());
}
if (secret == null)
{
hasher.AppendData(secretSpan.Slice(0, bytesWritten));
}
else
{
hasher.AppendData(secret);
Array.Clear(secret, 0, secret.Length);
}
return(null);
}
finally
{
if (!ReferenceEquals(otherPartyPublicKey, secTransPubKey))
{
secTransPubKey.Dispose();
}
}
}
/// <summary>
/// Get the secret agreement generated between two parties
/// </summary>
private byte[]? DeriveSecretAgreement(ECDiffieHellmanPublicKey otherPartyPublicKey, IncrementalHash?hasher)
{
Debug.Assert(otherPartyPublicKey != null);
// Ensure that this ECDH object contains a private key by attempting a parameter export
// which will throw an OpenSslCryptoException if no private key is available
ECParameters thisKeyExplicit = ExportExplicitParameters(true);
bool thisIsNamed = Interop.Crypto.EcKeyHasCurveName(_key.Value);
ECDiffieHellmanOpenSslPublicKey?otherKey = otherPartyPublicKey as ECDiffieHellmanOpenSslPublicKey;
bool disposeOtherKey = false;
if (otherKey == null)
{
disposeOtherKey = true;
ECParameters otherParameters =
thisIsNamed
? otherPartyPublicKey.ExportParameters()
: otherPartyPublicKey.ExportExplicitParameters();
otherKey = new ECDiffieHellmanOpenSslPublicKey(otherParameters);
}
bool otherIsNamed = otherKey.HasCurveName;
SafeEvpPKeyHandle?ourKey = null;
SafeEvpPKeyHandle?theirKey = null;
byte[]? rented = null;
int secretLength = 0;
try
{
if (otherKey.KeySize != KeySize)
{
throw new ArgumentException(SR.Cryptography_ArgECDHKeySizeMismatch, nameof(otherPartyPublicKey));
}
if (otherIsNamed == thisIsNamed)
{
ourKey = _key.UpRefKeyHandle();
theirKey = otherKey.DuplicateKeyHandle();
}
else if (otherIsNamed)
{
ourKey = _key.UpRefKeyHandle();
using (ECOpenSsl tmp = new ECOpenSsl(otherKey.ExportExplicitParameters()))
{
theirKey = tmp.UpRefKeyHandle();
}
}
else
{
using (ECOpenSsl tmp = new ECOpenSsl(thisKeyExplicit))
{
ourKey = tmp.UpRefKeyHandle();
}
theirKey = otherKey.DuplicateKeyHandle();
}
using (SafeEvpPKeyCtxHandle ctx = Interop.Crypto.EvpPKeyCtxCreate(ourKey, theirKey, out uint secretLengthU))
{
if (ctx == null || ctx.IsInvalid || secretLengthU == 0 || secretLengthU > int.MaxValue)
{
throw Interop.Crypto.CreateOpenSslCryptographicException();
}
secretLength = (int)secretLengthU;
// Indicate that secret can hold stackallocs from nested scopes
Span <byte> secret = stackalloc byte[0];
// Arbitrary limit. But it covers secp521r1, which is the biggest common case.
const int StackAllocMax = 66;
if (secretLength > StackAllocMax)
{
rented = CryptoPool.Rent(secretLength);
secret = new Span <byte>(rented, 0, secretLength);
}
else
{
secret = stackalloc byte[secretLength];
}
Interop.Crypto.EvpPKeyDeriveSecretAgreement(ctx, secret);
if (hasher == null)
{
return(secret.ToArray());
}
else
{
hasher.AppendData(secret);
return(null);
}
}
}
finally
{
theirKey?.Dispose();
ourKey?.Dispose();
if (disposeOtherKey)
{
otherKey.Dispose();
}
if (rented != null)
{
CryptoPool.Return(rented, secretLength);
}
}
}
/// <summary>
/// Get the secret agreement generated between two parties
/// </summary>
private byte[]? DeriveSecretAgreement(ECDiffieHellmanPublicKey otherPartyPublicKey, IncrementalHash?hasher)
{
Debug.Assert(otherPartyPublicKey != null);
// Ensure that this ECDH object contains a private key by attempting a parameter export
// which will throw an OpenSslCryptoException if no private key is available
ECParameters thisKeyExplicit = ExportExplicitParameters(true);
bool thisIsNamed = Interop.AndroidCrypto.EcKeyHasCurveName(_key.Value);
ECDiffieHellmanAndroidPublicKey?otherKey = otherPartyPublicKey as ECDiffieHellmanAndroidPublicKey;
bool disposeOtherKey = false;
if (otherKey == null)
{
disposeOtherKey = true;
ECParameters otherParameters =
thisIsNamed
? otherPartyPublicKey.ExportParameters()
: otherPartyPublicKey.ExportExplicitParameters();
otherKey = new ECDiffieHellmanAndroidPublicKey(otherParameters);
}
bool otherIsNamed = otherKey.HasCurveName;
SafeEcKeyHandle?ourKey = null;
SafeEcKeyHandle?theirKey = null;
byte[]? rented = null;
// Calculate secretLength in bytes.
int secretLength = AsymmetricAlgorithmHelpers.BitsToBytes(KeySize);
try
{
if (otherKey.KeySize != KeySize)
{
throw new ArgumentException(SR.Cryptography_ArgECDHKeySizeMismatch, nameof(otherPartyPublicKey));
}
if (otherIsNamed == thisIsNamed)
{
ourKey = _key.UpRefKeyHandle();
theirKey = otherKey.DuplicateKeyHandle();
}
else if (otherIsNamed)
{
ourKey = _key.UpRefKeyHandle();
using (ECAndroid tmp = new ECAndroid(otherKey.ExportExplicitParameters()))
{
theirKey = tmp.UpRefKeyHandle();
}
}
else
{
using (ECAndroid tmp = new ECAndroid(thisKeyExplicit))
{
ourKey = tmp.UpRefKeyHandle();
}
theirKey = otherKey.DuplicateKeyHandle();
}
// Indicate that secret can hold stackallocs from nested scopes
Span <byte> secret = stackalloc byte[0];
// Arbitrary limit. But it covers secp521r1, which is the biggest common case.
const int StackAllocMax = 66;
if (secretLength > StackAllocMax)
{
rented = CryptoPool.Rent(secretLength);
secret = new Span <byte>(rented, 0, secretLength);
}
else
{
secret = stackalloc byte[secretLength];
}
if (!Interop.AndroidCrypto.EcdhDeriveKey(ourKey, theirKey, secret, out int usedBufferLength))
{
throw new CryptographicException();
}
Debug.Assert(secretLength == usedBufferLength, $"Expected secret length {secretLength} does not match actual secret length {usedBufferLength}.");
if (hasher == null)
{
return(secret.ToArray());
}
else
{
hasher.AppendData(secret);
return(null);
}
}
finally
{
theirKey?.Dispose();
ourKey?.Dispose();
if (disposeOtherKey)
{
otherKey.Dispose();
}
if (rented != null)
{
CryptoPool.Return(rented, secretLength);
}
}
}