private static void CheckTag(DerTag expected, byte[] data, int position)
{
if (position >= data.Length)
{
throw new CryptographicException(SR.Cryptography_Der_Invalid_Encoding);
}
byte actual = data[position];
// Context-specific datatypes cannot be tag-verified
if ((actual & ContextSpecificTagFlag) != 0)
{
return;
}
byte relevant = (byte)(actual & TagNumberMask);
byte expectedByte = (byte)((byte)expected & TagNumberMask);
if (expectedByte != relevant)
{
throw new CryptographicException(
SR.Cryptography_Der_Invalid_Encoding
#if DEBUG
,
new InvalidOperationException(
"Expected tag '0x" + expectedByte.ToString("X2") +
"', got '0x" + actual.ToString("X2") +
"' at position " + position)
#endif
);
}
}
private static void CheckTag(DerTag expected, byte[] data, int position)
{
if (position >= data.Length)
{
throw new CryptographicException("Invalid Der-Encoding");
}
byte actual = data[position];
byte relevant = (byte)(actual & TagNumberMask);
// Multi-byte tags are not supported by this implementation.
if (relevant == TagNumberMask)
{
throw new CryptographicException("Invalid Der-Encoding");
}
// Context-specific datatypes cannot be tag-verified
if ((actual & ContextSpecificTagFlag) != 0)
{
return;
}
byte expectedByte = (byte)((byte)expected & TagNumberMask);
if (expectedByte != relevant)
{
throw new CryptographicException("Invalid Der-Encoding");
}
}
private void EatTag(DerTag expected)
{
if (!HasData)
{
throw new CryptographicException("Invalid Der-Encoding");
}
CheckTag(expected, _data, _position);
_position++;
}
private void EatTag(DerTag expected)
{
if (!HasData)
{
throw new CryptographicException(SR.GetString(SR.Cryptography_Der_Invalid_Encoding));
}
CheckTag(expected, _data, _position);
_position++;
}
private DerSequenceReader ReadCollectionWithTag(DerTag expected)
{
// DerSequenceReader wants to read its own tag, so don't EatTag here.
CheckTag(expected, _data, _position);
int lengthLength;
int contentLength = ScanContentLength(_data, _position + 1, _end, out lengthLength);
int totalLength = 1 + lengthLength + contentLength;
DerSequenceReader reader = new DerSequenceReader(expected, _data, _position, totalLength);
_position += totalLength;
return(reader);
}
internal DerSequenceReader(DerTag tagToEat, byte[] data, int offset, int length)
{
_data = data;
_end = offset + length;
Debug.Assert(data != null, "Data is null");
Debug.Assert(offset >= 0, "Offset is negative");
if (length < 2 || length > data.Length - offset)
{
throw new CryptographicException(SR.Cryptography_Der_Invalid_Encoding);
}
_position = offset;
EatTag(tagToEat);
ContentLength = EatLength();
}
private DerSequenceReader(DerTag tagToEat, byte[] data, int offset, int length)
{
Debug.Assert(data != null, "Data is null");
if (offset < 0 || length < 2 || length > data.Length - offset)
{
throw new CryptographicException("Invalid Der-Encoding");
}
_data = data;
_end = offset + length;
_position = offset;
EatTag(tagToEat);
int contentLength = EatLength();
Debug.Assert(_end - contentLength >= _position);
ContentLength = contentLength;
// If the sequence reports being smaller than the buffer, shrink the end-of-validity.
_end = _position + contentLength;
}
private static void CheckTag(DerTag expected, byte[] data, int position)
{
byte actual = data[position];
// Context-specific datatypes cannot be tag-verified
if ((actual & ContextSpecificTagFlag) != 0)
{
return;
}
byte relevant = (byte)(actual & 0x1F);
byte expectedByte = (byte)expected;
if (expectedByte != relevant)
{
throw new InvalidOperationException(
"Expected tag '0x" + expectedByte.ToString("X2") +
"', got '0x" + actual.ToString("X2") +
"' at position " + position);
}
}
private DateTime ReadTime(DerTag timeTag, string formatString)
{
EatTag(timeTag);
int contentLength = EatLength();
string decodedTime = System.Text.Encoding.ASCII.GetString(_data, _position, contentLength);
_position += contentLength;
Debug.Assert(
decodedTime[decodedTime.Length - 1] == 'Z',
$"The date doesn't follow the X.690 format, ending with {decodedTime[decodedTime.Length - 1]}");
DateTime time;
DateTimeFormatInfo fi = LazyInitializer.EnsureInitialized(
ref s_validityDateTimeFormatInfo,
() =>
{
var clone = (DateTimeFormatInfo)CultureInfo.InvariantCulture.DateTimeFormat.Clone();
clone.Calendar.TwoDigitYearMax = 2049;
return(clone);
});
if (!DateTime.TryParseExact(
decodedTime,
formatString,
fi,
DateTimeStyles.AssumeUniversal | DateTimeStyles.AdjustToUniversal,
out time))
{
throw new CryptographicException("Invalid Der-Encoding");
}
return(time);
}
internal bool HasTag(DerTag expectedTag)
{
return(HasTag((byte)expectedTag));
}
private void EatTag(DerTag expected)
{
CheckTag(expected, _data, _position);
_position++;
}
private static void CheckTag(DerTag expected, byte[] data, int position)
{
byte actual = data[position];
// Context-specific datatypes cannot be tag-verified
if ((actual & ContextSpecificTagFlag) != 0)
{
return;
}
byte relevant = (byte)(actual & 0x1F);
byte expectedByte = (byte)expected;
if (expectedByte != relevant)
{
throw new InvalidOperationException(
"Expected tag '0x" + expectedByte.ToString("X2") +
"', got '0x" + actual.ToString("X2") +
"' at position " + position);
}
}
private void EatTag(DerTag expected)
{
CheckTag(expected, _data, _position);
_position++;
}
internal byte[] ReadValue(DerTag tag)
{
EatTag(tag);
return(ReadContentAsBytes());
}
