def encode_name(self, name: Name) -> bytearray:
"""
Assembly a name-TLV
:param name: Name
:return: Name-TLV
"""
encoder = TlvEncoder()
# name = name[1:].split('/')
# for component in name[::-1]:
# encoder.writeBlobTlv(Tlv.NameComponent, [ord(c) for c in component])
# fill backwards
if name.digest:
encoder.writeBlobTlv(Tlv.ImplicitSha256DigestComponent, name.digest)
for c in name._components[::-1]:
encoder.writeBlobTlv(Tlv.NameComponent, c)
encoder.writeTypeAndLength(Tlv.Name, len(encoder))
return encoder.getOutput() #.tobytes()
def encode_data(self, name: Name, payload: bytearray) -> bytearray:
"""
Assembly a data packet
:param name: Name
:param payload: Payload
:return: Data-TLV
"""
encoder = TlvEncoder()
# Add content
encoder.writeBlobTlv(Tlv.Content, payload)
# Add meta info (empty)
encoder.writeTypeAndLength(Tlv.MetaInfo, 0)
# Add name
encoder.writeBuffer(self.encode_name(name))
# Add data type and len
encoder.writeTypeAndLength(Tlv.Data, len(encoder))
return encoder.getOutput().tobytes()
def encode_interest(self, name: Name) -> bytearray:
"""
Assembly an interest packet
:param name: Name
:return: Interest-TLV
"""
encoder = TlvEncoder()
# Add nonce
nonce = bytearray(4)
for i in range(4):
nonce[i] = SystemRandom().randint(0, 0xff)
encoder.writeBlobTlv(Tlv.Nonce, nonce)
# TODO: add implicitDigest flag here ?
# Add name
encoder.writeBuffer(self.encode_name(name))
# Add interest type and len
encoder.writeTypeAndLength(Tlv.Interest, len(encoder))
return encoder.getOutput().tobytes()
def encode_data(self, name: Name, payload: bytearray) -> bytearray:
"""
Assembly a data packet including a signature according to NDN packet format specification 0.3 (DigestSha256).
:param name: Name
:param payload: Payload
:return: Data-TLV
"""
encoder = TlvEncoder()
# Add signature (DigestSha256, zeroed)
encoder.writeBlobTlv(Tlv.SignatureValue, bytearray(32)) # signature value to set later
encoder.writeBlobTlv(Tlv.SignatureInfo, bytearray([Tlv.SignatureType, 1, 0]))
# Add content
encoder.writeBlobTlv(Tlv.Content, payload)
# Add meta info (empty)
encoder.writeTypeAndLength(Tlv.MetaInfo, 0)
# Add name
encoder.writeBuffer(self.encode_name(name))
# Add data type and len
encoder.writeTypeAndLength(Tlv.Data, len(encoder))
# Add signature value
packet_without_sig = encoder.getOutput().tobytes()
m = hashlib.sha256()
m.update(packet_without_sig[:-32])
sig = m.digest()
packet_with_sig = packet_without_sig[:-32] + sig
return packet_with_sig