public void SealWithMac(
ReadOnlySpan <char> password,
HashAlgorithmName hashAlgorithm,
int iterationCount)
{
if (iterationCount < 1)
{
throw new ArgumentOutOfRangeException(nameof(iterationCount));
}
if (IsSealed)
{
throw new InvalidOperationException(SR.Cryptography_Pkcs12_PfxIsSealed);
}
byte[]? rentedAuthSafe = null;
Span <byte> authSafeSpan = default;
byte[]? rentedMac = null;
Span <byte> macSpan = default;
Span <byte> salt = stackalloc byte[0];
try
{
AsnWriter contentsWriter = new AsnWriter(AsnEncodingRules.BER);
using (IncrementalHash hasher = IncrementalHash.CreateHash(hashAlgorithm))
{
contentsWriter.PushSequence();
if (_contents != null)
{
foreach (ContentInfoAsn contentInfo in _contents)
{
contentInfo.Encode(contentsWriter);
}
}
contentsWriter.PopSequence();
rentedAuthSafe = CryptoPool.Rent(contentsWriter.GetEncodedLength());
if (!contentsWriter.TryEncode(rentedAuthSafe, out int written))
{
Debug.Fail("TryEncode failed with a pre-allocated buffer");
throw new InvalidOperationException();
}
authSafeSpan = rentedAuthSafe.AsSpan(0, written);
// Get an array of the proper size for the hash.
byte[] macKey = hasher.GetHashAndReset();
rentedMac = CryptoPool.Rent(macKey.Length);
macSpan = rentedMac.AsSpan(0, macKey.Length);
// Since the biggest supported hash is SHA-2-512 (64 bytes), the
// 128-byte cap here shouldn't ever come into play.
Debug.Assert(macKey.Length <= 128);
salt = stackalloc byte[Math.Min(macKey.Length, 128)];
RandomNumberGenerator.Fill(salt);
Pkcs12Kdf.DeriveMacKey(
password,
hashAlgorithm,
iterationCount,
salt,
macKey);
using (IncrementalHash mac = IncrementalHash.CreateHMAC(hashAlgorithm, macKey))
{
mac.AppendData(authSafeSpan);
if (!mac.TryGetHashAndReset(macSpan, out int bytesWritten) || bytesWritten != macSpan.Length)
{
Debug.Fail($"TryGetHashAndReset wrote {bytesWritten} of {macSpan.Length} bytes");
throw new CryptographicException();
}
}
}
// https://tools.ietf.org/html/rfc7292#section-4
//
// PFX ::= SEQUENCE {
// version INTEGER {v3(3)}(v3,...),
// authSafe ContentInfo,
// macData MacData OPTIONAL
// }
AsnWriter writer = new AsnWriter(AsnEncodingRules.BER);
{
writer.PushSequence();
writer.WriteInteger(3);
writer.PushSequence();
{
writer.WriteObjectIdentifierForCrypto(Oids.Pkcs7Data);
Asn1Tag contextSpecific0 = new Asn1Tag(TagClass.ContextSpecific, 0);
writer.PushSequence(contextSpecific0);
{
writer.WriteOctetString(authSafeSpan);
writer.PopSequence(contextSpecific0);
}
writer.PopSequence();
}
// https://tools.ietf.org/html/rfc7292#section-4
//
// MacData ::= SEQUENCE {
// mac DigestInfo,
// macSalt OCTET STRING,
// iterations INTEGER DEFAULT 1
// -- Note: The default is for historical reasons and its use is
// -- deprecated.
// }
writer.PushSequence();
{
writer.PushSequence();
{
writer.PushSequence();
{
writer.WriteObjectIdentifierForCrypto(PkcsHelpers.GetOidFromHashAlgorithm(hashAlgorithm));
writer.PopSequence();
}
writer.WriteOctetString(macSpan);
writer.PopSequence();
}
writer.WriteOctetString(salt);
if (iterationCount > 1)
{
writer.WriteInteger(iterationCount);
}
writer.PopSequence();
}
writer.PopSequence();
_sealedData = writer.Encode();
}
}
finally
{
CryptographicOperations.ZeroMemory(macSpan);
CryptographicOperations.ZeroMemory(authSafeSpan);
if (rentedMac != null)
{
// Already cleared
CryptoPool.Return(rentedMac, clearSize: 0);
}
if (rentedAuthSafe != null)
{
// Already cleared
CryptoPool.Return(rentedAuthSafe, clearSize: 0);
}
}
}
public bool VerifyMac(ReadOnlySpan <char> password)
{
if (IntegrityMode != Pkcs12IntegrityMode.Password)
{
throw new InvalidOperationException(
SR.Format(
SR.Cryptography_Pkcs12_WrongModeForVerify,
Pkcs12IntegrityMode.Password,
IntegrityMode));
}
Debug.Assert(_decoded.MacData.HasValue);
HashAlgorithmName hashAlgorithm;
int expectedOutputSize;
string algorithmValue = _decoded.MacData.Value.Mac.DigestAlgorithm.Algorithm.Value;
switch (algorithmValue)
{
case Oids.Md5:
expectedOutputSize = 128 >> 3;
hashAlgorithm = HashAlgorithmName.MD5;
break;
case Oids.Sha1:
expectedOutputSize = 160 >> 3;
hashAlgorithm = HashAlgorithmName.SHA1;
break;
case Oids.Sha256:
expectedOutputSize = 256 >> 3;
hashAlgorithm = HashAlgorithmName.SHA256;
break;
case Oids.Sha384:
expectedOutputSize = 384 >> 3;
hashAlgorithm = HashAlgorithmName.SHA384;
break;
case Oids.Sha512:
expectedOutputSize = 512 >> 3;
hashAlgorithm = HashAlgorithmName.SHA512;
break;
default:
throw new CryptographicException(
SR.Format(SR.Cryptography_UnknownHashAlgorithm, algorithmValue));
}
if (_decoded.MacData.Value.Mac.Digest.Length != expectedOutputSize)
{
throw new CryptographicException(SR.Cryptography_Der_Invalid_Encoding);
}
// Cannot use the ArrayPool or stackalloc here because CreateHMAC needs a properly bounded array.
byte[] derived = new byte[expectedOutputSize];
int iterationCount =
PasswordBasedEncryption.NormalizeIterationCount(_decoded.MacData.Value.IterationCount);
Pkcs12Kdf.DeriveMacKey(
password,
hashAlgorithm,
iterationCount,
_decoded.MacData.Value.MacSalt.Span,
derived);
using (IncrementalHash hmac = IncrementalHash.CreateHMAC(hashAlgorithm, derived))
{
hmac.AppendData(_authSafeContents.Span);
if (!hmac.TryGetHashAndReset(derived, out int bytesWritten) || bytesWritten != expectedOutputSize)
{
Debug.Fail($"TryGetHashAndReset wrote {bytesWritten} bytes when {expectedOutputSize} was expected");
throw new CryptographicException();
}
return(CryptographicOperations.FixedTimeEquals(
derived,
_decoded.MacData.Value.Mac.Digest.Span));
}
}