/// <summary>
/// Encode SNMP packet for sending.
/// </summary>
/// <returns>BER encoded SNMP packet.</returns>
public override byte[] Encode()
{
MutableByte buf = new MutableByte();
if (Pdu.Type != PduType.Get && Pdu.Type != PduType.GetNext &&
Pdu.Type != PduType.Set && Pdu.Type != PduType.V2Trap &&
Pdu.Type != PduType.Response && Pdu.Type != PduType.GetBulk &&
Pdu.Type != PduType.Inform)
{
throw new SnmpInvalidPduTypeException("Invalid SNMP PDU type while attempting to encode PDU: " + string.Format("0x{0:x2}", Pdu.Type));
}
// snmp version
_protocolVersion.Encode(buf);
// community string
_snmpCommunity.Encode(buf);
// pdu
_pdu.Encode(buf);
// wrap the packet into a sequence
MutableByte tmpBuf = new MutableByte();
AsnType.BuildHeader(tmpBuf, SnmpConstants.SMI_SEQUENCE, buf.Length);
buf.Prepend(tmpBuf);
return(buf);
}
/// <summary>
/// Encode SNMP packet for sending.
/// </summary>
/// <returns>BER encoded SNMP packet.</returns>
/// <exception cref="SnmpInvalidPduTypeException">Thrown when PDU being encoded is not a valid SNMP version 1 PDU. Acceptable
/// protocol version 1 operations are GET, GET-NEXT, SET and RESPONSE.</exception>
public override byte[] Encode()
{
if (Pdu.Type != PduType.Get && Pdu.Type != PduType.GetNext &&
Pdu.Type != PduType.Set && Pdu.Type != PduType.Response)
{
throw new SnmpInvalidVersionException("Invalid SNMP PDU type while attempting to encode PDU: " + string.Format("0x{0:x2}", Pdu.Type));
}
if (Pdu.RequestId == 0)
{
System.Random rand = new System.Random((Int32)DateTime.Now.Ticks);
Pdu.RequestId = rand.Next();
}
MutableByte tmpBuffer = new MutableByte();
// snmp version
_protocolVersion.Encode(tmpBuffer);
// community string
_snmpCommunity.Encode(tmpBuffer);
// pdu
Pdu.Encode(tmpBuffer);
MutableByte buf = new MutableByte();
// wrap the packet into a sequence
AsnType.BuildHeader(buf, SnmpConstants.SMI_SEQUENCE, tmpBuffer.Length);
buf.Append(tmpBuffer);
return(buf);
}
/// <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>
/// Convert <see cref="ScopedPdu"/> into a BER encoded byte array. Resulting byte array is appended
/// to the argument specified <see cref="MutableByte"/> class.
///
/// Privacy operations are not performed by this method. Value encoded and returned by this method is
/// suitable for sending in NoAuthNoPriv or AuthNoPriv security configurations. If privacy is required,
/// caller will have to perform encryption and decryption operations after BER encoding is performed.
///
/// In privacy protected SNMP version 3 packets, ScopedPdu is 1) encrypted using configured encryption
/// method, 2) added to a <see cref="OctetString"/> field, and 3) appended to the data buffer.
///
/// Because privacy operation is intrusive, it is recommended that BER encoding of the ScopedPdu packet
/// is stored in a temporary <see cref="MutableByte"/> class, where it can be privacy protected and
/// added to the <see cref="OctetString"/> class for final encoding into the target SNMP v3 packet.
/// </summary>
/// <param name="buffer"><see cref="MutableByte"/> class passed by reference that encoded ScopedPdu
/// value is appended to.</param>
public override void Encode(MutableByte buffer)
{
MutableByte tmp = new MutableByte();
_contextEngineId.Encode(tmp);
_contextName.Encode(tmp);
// Encode base
base.Encode(tmp);
BuildHeader(buffer, SnmpConstants.SMI_SEQUENCE, tmp.Length);
buffer.Append(tmp);
}
/// <summary>
/// Encode SNMP packet for sending.
/// </summary>
/// <returns>BER encoded SNMP packet.</returns>
public override byte[] Encode()
{
MutableByte tmpBuffer = new MutableByte();
// encode the community strings
snmpCommunity.Encode(tmpBuffer);
Pdu.Encode(tmpBuffer);
Encode(tmpBuffer);
return(tmpBuffer);
}
/// <summary>
/// Encode SNMP v3 message flag field
/// </summary>
/// <param name="buffer">Buffer to append encoded value to</param>
public override void Encode(MutableByte buffer)
{
byte flag = 0x00;
if (_authenticationFlag)
{
flag |= FLAG_AUTH;
}
if (_privacyFlag)
{
flag |= FLAG_PRIV;
}
if (_reportableFlag)
{
flag |= FLAG_REPORTABLE;
}
OctetString flagObject = new OctetString(flag);
flagObject.Encode(buffer);
}
/// <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);
}
