Ensure the hash length (2x)

[shargon]

No description provided.

[igormcoelho]

I think we have a SafeRead method somewhere, to ensure this.

[lock9]

@igormcoelho I searched for it in code ("safe" and "reader.Read").
I found similar code in ECPoint class, but it has a length check in a second step.

public static ECPoint DeserializeFrom(BinaryReader reader, ECCurve curve)
        {
            int expectedLength = (curve.Q.GetBitLength() + 7) / 8;
            byte[] buffer = new byte[1 + expectedLength * 2];
            buffer[0] = reader.ReadByte();
            switch (buffer[0])
            {
                case 0x02:
                case 0x03:
                    reader.Read(buffer, 1, expectedLength);
                    return DecodePoint(buffer.Take(1 + expectedLength).ToArray(), curve);
                case 0x04:
                    reader.Read(buffer, 1, expectedLength * 2);
                    return DecodePoint(buffer, curve);
                default:
                    throw new FormatException("Invalid point encoding " + buffer[0]);
            }
        }

public static ECPoint DecodePoint(byte[] encoded, ECCurve curve)
        {
            ECPoint p = null;
            int expectedLength = (curve.Q.GetBitLength() + 7) / 8;
            switch (encoded[0])
            {
                case 0x02: // compressed
                case 0x03: // compressed
                    {
                        if (encoded.Length != (expectedLength + 1))
                            throw new FormatException("Incorrect length for compressed encoding");
                        int yTilde = encoded[0] & 1;
                        BigInteger X1 = new BigInteger(encoded.Skip(1).Reverse().Concat(new byte[1]).ToArray());
                        p = DecompressPoint(yTilde, X1, curve);
                        break;
                    }
                case 0x04: // uncompressed
                    {
                        if (encoded.Length != (2 * expectedLength + 1))
                            throw new FormatException("Incorrect length for uncompressed/hybrid encoding");
                        BigInteger X1 = new BigInteger(encoded.Skip(1).Take(expectedLength).Reverse().Concat(new byte[1]).ToArray());
                        BigInteger Y1 = new BigInteger(encoded.Skip(1 + expectedLength).Reverse().Concat(new byte[1]).ToArray());
                        p = new ECPoint(new ECFieldElement(X1, curve), new ECFieldElement(Y1, curve), curve);
                        break;
                    }
                default:
                    throw new FormatException("Invalid point encoding " + encoded[0]);
            }
            return p;
        }

[shargon]

i will fix it

[lock9]

Don't forget to check if this fix is also required in 3x

[shargon]

Is done @lock9, ready to be merged