/// <summary>
/// This function checks the magic value in the key blob header
/// </summary>
/// <param name="magic">The expected magic number.</param>
/// <param name="includePrivateParameters">Private blob if true else public key blob</param>
private static void CheckMagicValueOfKey(KeyBlobMagicNumber magic, bool includePrivateParameters)
{
if (includePrivateParameters)
{
if (magic != KeyBlobMagicNumber.BCRYPT_DSA_PRIVATE_MAGIC && magic != KeyBlobMagicNumber.BCRYPT_DSA_PRIVATE_MAGIC_V2)
{
throw new CryptographicException(SR.Cryptography_NotValidPrivateKey);
}
}
else
{
if (magic != KeyBlobMagicNumber.BCRYPT_DSA_PUBLIC_MAGIC && magic != KeyBlobMagicNumber.BCRYPT_DSA_PUBLIC_MAGIC_V2)
{
throw new CryptographicException(SR.Cryptography_NotValidPublicOrPrivateKey);
}
}
}
public override DSAParameters ExportParameters(bool includePrivateParameters)
{
byte[] dsaBlob = ExportKeyBlob(includePrivateParameters);
KeyBlobMagicNumber magic = (KeyBlobMagicNumber)BitConverter.ToInt32(dsaBlob, 0);
// Check the magic value in the key blob header. If the blob does not have the required magic,
// then throw a CryptographicException.
CheckMagicValueOfKey(magic, includePrivateParameters);
unsafe
{
DSAParameters dsaParams = default;
fixed(byte *pDsaBlob = dsaBlob)
{
int offset;
if (magic == KeyBlobMagicNumber.BCRYPT_DSA_PUBLIC_MAGIC || magic == KeyBlobMagicNumber.BCRYPT_DSA_PRIVATE_MAGIC)
{
if (dsaBlob.Length < sizeof(BCRYPT_DSA_KEY_BLOB))
{
throw ErrorCode.E_FAIL.ToCryptographicException();
}
BCRYPT_DSA_KEY_BLOB *pBcryptBlob = (BCRYPT_DSA_KEY_BLOB *)pDsaBlob;
// We now have a buffer laid out as follows:
// BCRYPT_DSA_KEY_BLOB header
// byte[cbKey] P
// byte[cbKey] G
// byte[cbKey] Y
// -- Private only --
// byte[Sha1HashOutputSize] X
offset = sizeof(KeyBlobMagicNumber) + sizeof(int); // skip Magic and cbKey
// Read out a (V1) BCRYPT_DSA_KEY_BLOB structure.
dsaParams.Counter = BinaryPrimitives.ReadInt32BigEndian(Interop.BCrypt.Consume(dsaBlob, ref offset, 4));
dsaParams.Seed = Interop.BCrypt.Consume(dsaBlob, ref offset, Sha1HashOutputSize);
dsaParams.Q = Interop.BCrypt.Consume(dsaBlob, ref offset, Sha1HashOutputSize);
Debug.Assert(offset == sizeof(BCRYPT_DSA_KEY_BLOB), $"Expected offset = sizeof(BCRYPT_DSA_KEY_BLOB), got {offset} != {sizeof(BCRYPT_DSA_KEY_BLOB)}");
dsaParams.P = Interop.BCrypt.Consume(dsaBlob, ref offset, pBcryptBlob->cbKey);
dsaParams.G = Interop.BCrypt.Consume(dsaBlob, ref offset, pBcryptBlob->cbKey);
dsaParams.Y = Interop.BCrypt.Consume(dsaBlob, ref offset, pBcryptBlob->cbKey);
if (includePrivateParameters)
{
dsaParams.X = Interop.BCrypt.Consume(dsaBlob, ref offset, Sha1HashOutputSize);
}
}
else
{
Debug.Assert(magic == KeyBlobMagicNumber.BCRYPT_DSA_PUBLIC_MAGIC_V2 || magic == KeyBlobMagicNumber.BCRYPT_DSA_PRIVATE_MAGIC_V2);
if (dsaBlob.Length < sizeof(BCRYPT_DSA_KEY_BLOB_V2))
{
throw ErrorCode.E_FAIL.ToCryptographicException();
}
BCRYPT_DSA_KEY_BLOB_V2 *pBcryptBlob = (BCRYPT_DSA_KEY_BLOB_V2 *)pDsaBlob;
// We now have a buffer laid out as follows:
// BCRYPT_DSA_KEY_BLOB_V2 header
// byte[cbSeedLength] Seed
// byte[cbGroupSize] Q
// byte[cbKey] P
// byte[cbKey] G
// byte[cbKey] Y
// -- Private only --
// byte[cbGroupSize] X
offset = sizeof(BCRYPT_DSA_KEY_BLOB_V2) - 4; //skip to Count[4]
// Read out a BCRYPT_DSA_KEY_BLOB_V2 structure.
dsaParams.Counter = BinaryPrimitives.ReadInt32BigEndian(Interop.BCrypt.Consume(dsaBlob, ref offset, 4));
Debug.Assert(offset == sizeof(BCRYPT_DSA_KEY_BLOB_V2), $"Expected offset = sizeof(BCRYPT_DSA_KEY_BLOB_V2), got {offset} != {sizeof(BCRYPT_DSA_KEY_BLOB_V2)}");
dsaParams.Seed = Interop.BCrypt.Consume(dsaBlob, ref offset, pBcryptBlob->cbSeedLength);
dsaParams.Q = Interop.BCrypt.Consume(dsaBlob, ref offset, pBcryptBlob->cbGroupSize);
dsaParams.P = Interop.BCrypt.Consume(dsaBlob, ref offset, pBcryptBlob->cbKey);
dsaParams.G = Interop.BCrypt.Consume(dsaBlob, ref offset, pBcryptBlob->cbKey);
dsaParams.Y = Interop.BCrypt.Consume(dsaBlob, ref offset, pBcryptBlob->cbKey);
if (includePrivateParameters)
{
dsaParams.X = Interop.BCrypt.Consume(dsaBlob, ref offset, pBcryptBlob->cbGroupSize);
}
}
// If no counter/seed information is present, normalize Counter and Seed to 0/null to maintain parity with the CAPI version of DSA.
if (dsaParams.Counter == -1)
{
dsaParams.Counter = 0;
dsaParams.Seed = null;
}
Debug.Assert(offset == dsaBlob.Length, $"Expected offset = dsaBlob.Length, got {offset} != {dsaBlob.Length}");
return(dsaParams);
}
}
}
/// <summary>
/// This function checks the magic value in the key blob header
/// </summary>
/// <param name="includePrivateParameters">Private blob if true else public key blob</param>
private static void CheckMagicValueOfKey(KeyBlobMagicNumber magic, bool includePrivateParameters)
{
if (includePrivateParameters)
{
if (magic != KeyBlobMagicNumber.BCRYPT_DSA_PRIVATE_MAGIC && magic != KeyBlobMagicNumber.BCRYPT_DSA_PRIVATE_MAGIC_V2)
throw new CryptographicException(SR.Cryptography_NotValidPrivateKey);
}
else
{
if (magic != KeyBlobMagicNumber.BCRYPT_DSA_PUBLIC_MAGIC && magic != KeyBlobMagicNumber.BCRYPT_DSA_PUBLIC_MAGIC_V2)
throw new CryptographicException(SR.Cryptography_NotValidPublicOrPrivateKey);
}
}
