/// <summary>Parse a revocation message.</summary>
public UserRevocationMessage(Certificate cacert, MemBlock data)
{
_data = data;
int pos = 0;
int length = 0;
Username = AdrConverter.Deserialize(data, pos, out length) as string;
pos += length;
// Random number to reduce likelihood of malicious duplication of messages
NumberSerializer.ReadInt(data, pos);
pos += 4;
// Verify that there is a date contained therein, perhaps we should verify the time
new DateTime(NumberSerializer.ReadLong(data, pos));
pos += 8;
Signature = new byte[data.Length - pos];
data.Slice(pos).CopyTo(Signature, 0);
// hash the data
SHA1CryptoServiceProvider sha1 = new SHA1CryptoServiceProvider();
Hash = sha1.ComputeHash(data, 0, data.Length - Signature.Length);
if (!cacert.PublicKey.VerifyHash(Hash,
CryptoConfig.MapNameToOID("SHA1"), Signature))
{
throw new Exception("Invalid UserRevocationMessage signature");
}
}
/// <summary>Parses web data and updates the revoked users hashtable if
/// successful</summary>
protected void UpdateRl(byte[] data)
{
// message is length (4) + date (8) + data (variable) + hash (~20)
int length = data.Length;
if (length < 12)
{
throw new Exception("No data? Didn't get enough data...");
}
length = NumberSerializer.ReadInt(data, 0);
DateTime date = new DateTime(NumberSerializer.ReadLong(data, 4));
// warn the user that this is an old revocation list, maybe there is an attack
if (date < DateTime.UtcNow.AddHours(-24))
{
ProtocolLog.WriteIf(IpopLog.GroupVPN, "Revocation list is over 24 hours old");
}
// Weird, data length is longer than the data we got
if (length > data.Length - 12)
{
throw new Exception("Missing data? Didn't get enough data...");
}
// hash the data and verify the signature
SHA1CryptoServiceProvider sha1 = new SHA1CryptoServiceProvider();
byte[] hash = sha1.ComputeHash(data, 4, length);
byte[] signature = new byte[data.Length - 4 - length];
Array.Copy(data, 4 + length, signature, 0, signature.Length);
if (!_ca_cert.PublicKey.VerifyHash(hash, CryptoConfig.MapNameToOID("SHA1"), signature))
{
throw new Exception("Invalid signature!");
}
// convert the data to an array list as it was sent to us
MemBlock mem = MemBlock.Reference(data, 12, length - 8);
ArrayList rl = AdrConverter.Deserialize(mem) as ArrayList;
if (rl == null)
{
throw new Exception("Data wasn't a list...");
}
// convert it into a hashtable for O(1) look ups
Hashtable ht = new Hashtable();
foreach (string username in rl)
{
ht[username] = true;
}
Interlocked.Exchange(ref _revoked_users, ht);
}