/// <summary>Encode Pdu class to BER byte buffer</summary>
/// <remarks>
/// Encodes the protocol data unit using the passed encoder and stores
/// the results in the passed buffer. An exception is thrown if an
/// error occurs with the encoding of the information.
/// </remarks>
/// <param name="buffer">The buffer to write the encoded information.</param>
public override void Encode(MutableByte buffer)
{
MutableByte tmpBuffer = new MutableByte();
// if request id is 0, get a random value
if (requestId.Value == 0)
{
requestId.SetRandom();
}
requestId.Encode(tmpBuffer);
errorStatus.Encode(tmpBuffer);
errorIndex.Encode(tmpBuffer);
// if V2TRAP PDU type, add sysUpTime and trapObjectID OIDs before encoding VarBind
if (Type == EPduType.V2Trap || Type == EPduType.Inform)
{
if (VbList.Count == 0)
{
// add sysUpTime and trapObjectID to the VbList
VbList.Add(SnmpConstants.SysUpTime, TrapSysUpTime);
VbList.Add(SnmpConstants.TrapObjectId, trapObjectID);
}
else
{
// Make sure user didn't manually add sysUpTime and trapObjectID values
// to the pdu
// if we have more then one item in the VarBinds array check for sysUpTime
if (VbList.Count > 0)
{
// if the first Vb in the VarBinds array is not sysUpTime append it in the
// encoded byte array
if (!VbList[0].Oid.Equals(SnmpConstants.SysUpTime))
{
Vb sysUpTimeVb = new Vb(SnmpConstants.SysUpTime, TrapSysUpTime);
VbList.Insert(0, sysUpTimeVb);
}
}
// if we have 2 or more Vbs in the VarBinds array check for trapObjectID Vb
if (VbList.Count > 1)
{
// if second Vb in the VarBinds array is not trapObjectId encode the value
if (!VbList[1].Oid.Equals(SnmpConstants.TrapObjectId))
{
Vb trapObjectIdVb = new Vb(SnmpConstants.TrapObjectId, trapObjectID);
VbList.Insert(1, trapObjectIdVb);
}
}
}
}
// encode variable bindings
VbList.Encode(tmpBuffer);
// Now encode the header for the PDU
BuildHeader(buffer, (byte)Type, tmpBuffer.Length);
buffer.Append(tmpBuffer);
}
/// <summary>BER encode security model field.</summary>
/// <remarks>
/// USM security model is a SEQUENCE encoded inside a OCTETSTRING. To encode it, first encode the sequence
/// of class values then "wrap" it inside a OCTETSTRING field
/// </remarks>
/// <param name="buffer">Buffer to store encoded USM security model header</param>
public override void Encode(MutableByte buffer)
{
MutableByte tmp = new MutableByte();
// First encode all the values that will form the sequence
_engineId.Encode(tmp);
// Encode engine boots
_engineBoots.Encode(tmp);
// encode engine time
_engineTime.Encode(tmp);
_securityName.Encode(tmp);
if (_authentication != AuthenticationDigests.None)
{
if (AuthenticationParameters.Length <= 0)
{
// If authentication is used, set authentication parameters field to 12 bytes set to 0x00
AuthenticationParameters.Set(new byte[] { 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 });
}
}
else
{
AuthenticationParameters.Reset();
}
AuthenticationParameters.Encode(tmp);
if (_privacy != PrivacyProtocols.None)
{
if (_privacyParameters.Length <= 0)
{
IPrivacyProtocol privProto = PrivacyProtocol.GetInstance(_privacy);
if (privProto != null)
{
byte[] parameter = new byte[privProto.PrivacyParametersLength];
for (int i = 0; i < privProto.PrivacyParametersLength; i++)
{
parameter[i] = 0x00; // This is not necessary since all array members are, by default, initialized to 0
}
_privacyParameters.Set(parameter);
}
else
{
throw new SnmpException(SnmpException.UnsupportedPrivacyProtocol, "Unrecognized privacy protocol specified.");
}
}
}
else
{
_privacyParameters.Reset();
}
_privacyParameters.Encode(tmp);
MutableByte tmp1 = new MutableByte();
BuildHeader(tmp1, SnmpConstants.SMI_SEQUENCE, tmp.Length);
tmp1.Append(tmp);
BuildHeader(buffer, OCTETSTRING, tmp1.Length);
buffer.Append(tmp1);
}
/// <summary>
/// Wrap BER encoded SNMP information contained in the parameter <see cref="MutableByte"/> class.
///
/// Information in the parameter is prepended by the SNMP version field and wrapped in a sequence header.
///
/// Derived classes call this method to finalize SNMP packet encoding.
/// </summary>
/// <param name="buffer">Buffer containing BER encoded SNMP information</param>
public virtual void Encode(MutableByte buffer)
{
// Encode SNMP protocol version
MutableByte temp = new MutableByte();
_protocolVersion.Encode(temp);
buffer.Prepend(temp);
temp.Reset();
AsnType.BuildHeader(temp, SnmpConstants.SMI_SEQUENCE, buffer.Length);
buffer.Prepend(temp);
}
/// <summary>ASN.1 encode SNMP version 1 trap</summary>
/// <param name="buffer"><see cref="MutableByte"/> buffer to the end of which encoded values are appended.</param>
public override void Encode(MutableByte buffer)
{
MutableByte trapBuffer = new MutableByte();
// encode the enterprise id & address
_enterprise.Encode(trapBuffer);
_agentAddr.Encode(trapBuffer);
_generic.Encode(trapBuffer);
_specific.Encode(trapBuffer);
_timeStamp.Encode(trapBuffer);
VbList.Encode(trapBuffer);
MutableByte tmpBuffer = new MutableByte();
BuildHeader(tmpBuffer, (byte)PduType.Trap, trapBuffer.Length);
trapBuffer.Prepend(tmpBuffer);
buffer.Append(trapBuffer);
}
/// <summary>Encode SNMP version 3 packet</summary>
/// <param name="authKey">Authentication key (not password)</param>
/// <param name="privKey">Privacy key (not password)</param>
/// <remarks>
/// Before encoding the packet into a byte array you need to ensure all required information is
/// set. Examples of required information is request type, Vbs (Oid + values pairs), USM settings including
/// SecretName, authentication method and secret (if needed), privacy method and secret (if needed), etc.
/// </remarks>
/// <returns>Byte array BER encoded SNMP packet.</returns>
public byte[] Encode(byte[] authKey, byte[] privKey)
{
MutableByte buffer = new MutableByte();
// encode the global message data sequence header information
MutableByte globalMessageData = new MutableByte();
// if message id is 0 then generate a new, random message id
if (messageId.Value == 0)
{
Random rand = new Random();
messageId.Value = rand.Next(1, int.MaxValue);
}
// encode message id
messageId.Encode(globalMessageData);
// encode max message size
maxMessageSize.Encode(globalMessageData);
// message flags
messageFlags.Encode(globalMessageData);
// security model code
securityModel.Value = userSecurityModel.Type;
securityModel.Encode(globalMessageData);
// add global message data to the main buffer
// encode sequence header and add data
AsnType.BuildHeader(buffer, SnmpConstants.SmiSequence, globalMessageData.Length);
buffer.Append(globalMessageData);
MutableByte packetHeader = new MutableByte(buffer);
// before going down this road, check if this is a discovery packet
OctetString savedUserName = new OctetString();
bool privacy = messageFlags.Privacy;
bool authentication = messageFlags.Authentication;
bool reportable = messageFlags.Reportable;
if (userSecurityModel.EngineId.Length <= 0)
{
// save USM settings prior to encoding a Discovery packet
savedUserName.Set(userSecurityModel.SecurityName);
userSecurityModel.SecurityName.Reset(); // delete security name for discovery packets
messageFlags.Authentication = false;
messageFlags.Privacy = false;
messageFlags.Reportable = true;
}
userSecurityModel.Encode(buffer);
if (userSecurityModel.EngineId.Length <= 0)
{
// restore saved USM values
userSecurityModel.SecurityName.Set(savedUserName);
messageFlags.Authentication = authentication;
messageFlags.Privacy = privacy;
messageFlags.Reportable = reportable;
}
// Check if privacy encryption is required
MutableByte encodedPdu = new MutableByte();
if (messageFlags.Privacy && userSecurityModel.EngineId.Length > 0)
{
IPrivacyProtocol privacyProtocol = PrivacyProtocol.GetInstance(userSecurityModel.Privacy);
if (privacyProtocol == null)
{
throw new SnmpException(SnmpException.EErrorCode.UnsupportedPrivacyProtocol, "Specified privacy protocol is not supported.");
}
// Get BER encoded ScopedPdu
MutableByte unencryptedPdu = new MutableByte();
scopedPdu.Encode(unencryptedPdu);
// we have to expand the key
IAuthenticationDigest auth = Authentication.GetInstance(userSecurityModel.Authentication);
if (auth == null)
{
throw new SnmpException(SnmpException.EErrorCode.UnsupportedNoAuthPriv, "Invalid authentication protocol. noAuthPriv mode not supported.");
}
byte[] encryptedBuffer = privacyProtocol.Encrypt(unencryptedPdu, 0, unencryptedPdu.Length, privKey, userSecurityModel.EngineBoots, userSecurityModel.EngineTime, out byte[] privacyParameters, auth);
userSecurityModel.PrivacyParameters.Set(privacyParameters);
OctetString encryptedOctetString = new OctetString(encryptedBuffer);
encryptedOctetString.Encode(encodedPdu);
// now redo packet encoding
buffer.Reset();
buffer.Set(packetHeader);
userSecurityModel.Encode(buffer);
int preEncodedLength = encodedPdu.Length;
buffer.Append(encodedPdu);
if (maxMessageSize.Value != 0)
{
// verify compliance with maximum message size
if ((encodedPdu.Length - preEncodedLength) > maxMessageSize)
{
throw new SnmpException(SnmpException.EErrorCode.MaximumMessageSizeExceeded, "ScopedPdu exceeds maximum message size.");
}
}
}
else
{
scopedPdu.Encode(encodedPdu);
buffer.Append(encodedPdu);
}
Encode(buffer);
if (messageFlags.Authentication && userSecurityModel.EngineId.Length > 0)
{
userSecurityModel.Authenticate(authKey, ref buffer);
// Now re-encode the packet with the authentication information
userSecurityModel.Encode(packetHeader);
packetHeader.Append(encodedPdu);
Encode(packetHeader);
buffer = packetHeader;
}
return(buffer);
}
