private static bool ReadFixedData(ref ArrayOffset <byte> input, int length, out byte[] data)
{
if (input.Length < length)
{
data = null;
return(false);
}
data = new byte[length];
input.CopyTo(data, 0, length);
input += length;
return(true);
}
public static IList <SctSignature> DecodeData(byte[] rawData)
{
var signatures = new List <SctSignature>();
var rData = new ArrayOffset <byte>(rawData, 0);
ArrayOffset <byte> list;
if (!ReadChunkUInt16Header(ref rData, out list))
{
return(signatures);
}
ArrayOffset <byte> sct;
int index = 0;
while (ReadChunkUInt16Header(ref list, out sct))
{
var originalSct = sct;
SctVersion version;
byte[] logId;
DateTime timestamp;
byte[] extensions;
SctHashAlgorithm hashAlgorithm;
SctSignatureAlgorithm signatureAlgorithm;
byte[] signature;
if (
!ReadByteEnumeration(ref sct, out version) ||
!ReadFixedData(ref sct, LOG_ID_SIZE, out logId) ||
!ReadTimestamp(ref sct, out timestamp) ||
!ReadVariableDataUInt16Header(ref sct, out extensions) ||
!ReadByteEnumeration(ref sct, out hashAlgorithm) ||
!ReadByteEnumeration(ref sct, out signatureAlgorithm) ||
!ReadVariableDataUInt16Header(ref sct, out signature)
)
{
continue;
}
signatures.Add(new SctSignature
{
LogId = logId,
Timestamp = timestamp,
HashAlgorithm = hashAlgorithm,
SignatureAlgorithm = signatureAlgorithm,
Extensions = extensions,
Signature = signature,
Index = index++
});
}
return(signatures);
}
private static bool ReadTimestamp(ref ArrayOffset <byte> input, out DateTime timestamp)
{
const int size = sizeof(ulong);
if (input.Length < size)
{
timestamp = default(DateTime);
return(false);
}
var epochTime = 0UL;
for (int i = 0, shift = size - 1; i < size; i++, shift--)
{
epochTime |= ((ulong)input[i] << (shift * 8));
}
timestamp = Epoch.UNIX_EPOCH.AddMilliseconds(epochTime);
input += size;
return(true);
}
private static bool ReadByteEnumeration <TEnumType>(ref ArrayOffset <byte> input, out TEnumType value)
{
if (!typeof(TEnumType).IsEnum || typeof(TEnumType).GetEnumUnderlyingType() != typeof(byte))
{
throw new ArgumentException(nameof(TEnumType));
}
const int size = sizeof(byte);
if (input.Length < size)
{
value = default(TEnumType);
return(false);
}
var val = input[0];
value = (TEnumType)(object)val;
input += size;
return(true);
}
private static bool ReadChunkUInt16Header(ref ArrayOffset <byte> input, out ArrayOffset <byte> output)
{
var inputCopy = input;
const int headerSize = sizeof(ushort);
if (inputCopy.Length < headerSize)
{
output = default(ArrayOffset <byte>);
return(false);
}
var chunkSize = (ushort)(inputCopy[0] << 8 | inputCopy[1]); //TLS records are big endian.
if (chunkSize > inputCopy.Length - headerSize)
{
output = default(ArrayOffset <byte>);
return(false);
}
var amountToConsume = headerSize + chunkSize;
output = inputCopy + headerSize;
input += amountToConsume;
return(true);
}
private static bool ReadVariableDataUInt16Header(ref ArrayOffset <byte> input, out byte[] data)
{
const int headerSize = sizeof(ushort);
if (input.Length < headerSize)
{
data = null;
return(false);
}
var chunkSize = (ushort)(input[0] << 8 | input[1]); //Big endian read
input += headerSize;
if (chunkSize == 0)
{
data = new byte[0];
return(true);
}
var result = new byte[chunkSize];
input.CopyTo(result, 0, chunkSize);
input += chunkSize;
data = result;
return(true);
}
