// returns offset of varbind list
public UInt32 Deserialize(Byte[] packet, UInt32 offset)
{
this.packetBytes = packet;
UInt32 initialOffset = offset;
//
// SNMP Message Type
//
if (packet[offset] != Asn1.TYPE_SEQUENCE)
{
throw new FormatException(String.Format(
"Expected snmp packet to be of type Sequence but is {0}", Asn1.GetTypeOrNumberString(packet[offset])));
}
offset++;
UInt32 sequenceLength = Asn1.ParseDefiniteLength(packet, ref offset);
UInt32 sequenceOffsetLimit = offset + sequenceLength;
if (packet.Length - offset < sequenceLength)
{
throw new FormatException(String.Format(
"Failed to parse snmp packet because it was truncated from {0} bytes to {1}",
sequenceLength + (offset - initialOffset), packet.Length - initialOffset));
}
//
// Version
//
if (packet[offset] != Asn1.TYPE_INTEGER)
{
throw new FormatException(String.Format(
"Expected snmp version to be of type Integer but is {0}", Asn1.GetTypeOrNumberString(packet[offset])));
}
offset++;
this.version = Asn1.ParseIntegerToByte(packet, ref offset);
if (this.version != 0)
{
throw new NotImplementedException(String.Format("Snmp version {0} (binary code {1}) is not implemented yet",
this.version + 1, this.version));
}
//
// Community
//
if (packet[offset] != Asn1.TYPE_OCTET_STRING)
{
throw new FormatException(String.Format(
"Expected snmp community to be of type OctetString but is '{0}'", Asn1.GetTypeOrNumberString(packet[offset])));
}
offset++;
Int32 communityLength = (Byte)Asn1.ParseDefiniteLength(packet, ref offset);
if (communityLength < 0)
{
throw new FormatException(String.Format("Expected community octet string length to be positive but is {0}", communityLength));
}
offset += (UInt32)communityLength;
//
// PDU Type
//
Byte pduTypeByte = packet[offset];
offset++;
if (pduTypeByte < 0xA0)
{
throw new FormatException(String.Format("Expected SNMP pdu type to be >= 0xA0 but is {0:2X}", pduTypeByte));
}
//
// Use similar logic to parse similar types
// Get, GetNext, GetResponse, Set
if (pduTypeByte <= 0xA3)
{
SnmpPduType pduType = (SnmpPduType)(pduTypeByte - 0xA0);
UInt32 pduLength = Asn1.ParseDefiniteLength(packet, ref offset);
if (offset + pduLength != sequenceOffsetLimit)
{
throw new FormatException(String.Format(
"Snmp packet is malformed, the pdu which ends at {0} does not end at the same place as the sequence at {1}",
offset + pduLength, sequenceOffsetLimit));
}
//
// Request ID
//
if (packet[offset] != Asn1.TYPE_INTEGER)
{
throw new FormatException(String.Format(
"Expected Snmp{0}Pdu to start with the Integer type but started with '{1}'", pduType, Asn1.GetTypeOrNumberString(packet[offset])));
}
offset++;
this.requestID = Asn1.ParseIntegerToInt32(packet, ref offset);
//
// Error Status
//
if (packet[offset] != Asn1.TYPE_INTEGER)
{
throw new FormatException(String.Format(
"Expected Snmp{0}Pdu ErrorStatus to be an Integer type but is '{1}'", pduType, Asn1.GetTypeOrNumberString(packet[offset])));
}
offset++;
this.errorStatus = (SnmpErrorStatus)Asn1.ParseIntegerToInt32(packet, ref offset);
//
// Error Index
//
if (packet[offset] != Asn1.TYPE_INTEGER)
{
throw new FormatException(String.Format(
"Expected Snmp{0}Pdu ErrorIndex to be an Integer type but is '{1}'", pduType, Asn1.GetTypeOrNumberString(packet[offset])));
}
offset++;
this.errorIndex = Asn1.ParseIntegerToInt32(packet, ref offset);
//
// Varbind List
//
if (packet[offset] != Asn1.TYPE_SEQUENCE)
{
throw new FormatException(String.Format(
"Expected varbind list to be of type Sequence but is {0}", Asn1.GetTypeOrNumberString(packet[offset])));
}
offset++;
UInt32 varbindListLength = Asn1.ParseDefiniteLength(packet, ref offset);
if (offset + varbindListLength != sequenceOffsetLimit)
{
throw new FormatException(String.Format(
"Snmp packet is malformed, the varbind list which ends at {0} does not end at the same place as the sequence at {1}",
offset + varbindListLength, sequenceOffsetLimit));
}
return(offset); // return the offset to the varbind variables
}
else
{
throw new NotImplementedException(String.Format("Snmp pdu type {0} is not implemented yet", pduTypeByte));
}
}
public static Int32 ParsePduInt32(Byte[] packet, UInt32 offset, UInt32 length)
{
UInt32 initialOffset = offset;
//
// Varbind
//
if (packet[offset] != Asn1.TYPE_SEQUENCE)
{
throw new FormatException(String.Format(
"Expected varbind to be of type Sequence but is {0}", Asn1.GetTypeOrNumberString(packet[offset])));
}
offset++;
UInt32 varbindLength = Asn1.ParseDefiniteLength(packet, ref offset);
if (packet.Length - offset < varbindLength)
{
throw new FormatException(String.Format(
"Failed to parse snmp packet because it was truncated from {0} bytes to {1}",
varbindLength + (offset - initialOffset), packet.Length - initialOffset));
}
//
// Skip the bound variable
//
offset++; // Skip the type
UInt32 boundVariableLength = Asn1.ParseDefiniteLength(packet, ref offset);
offset += boundVariableLength;
//
// Parse the integer
//
if (packet[offset] != Asn1.TYPE_INTEGER)
{
throw new FormatException(String.Format(
"Expected value to be of type Integer but is {0}", Asn1.GetTypeOrNumberString(packet[offset])));
}
offset++;
return(Asn1.ParseIntegerToInt32(packet, ref offset));
}
