Merge pull request #30 from quentinlampin/sctp-checksum

SCTP checksum compute

microschc/binary/buffer.py

@@ -395,6 +395,21 @@ def __xor__(self, another: 'Buffer'):
         bitwise_xor_buffer: Buffer = Buffer(content=bitwise_xor_content, length=self.length, padding=self.padding)
         return bitwise_xor_buffer
 
+    def __invert__(self):
+        two_complement_content: bytes = b''
+        if self.padding == Padding.LEFT:
+            mask: int = (1 << (8 - self.padding_length)%8) - 1
+            two_complement_content += (~self.content[0] & mask).to_bytes(1, 'big')
+            for b in iter(self.content):
+                two_complement_content += (~b & 0xff).to_bytes(1, 'big')
+        else:
+            mask: int = (0xff << (self.padding_length)) & 0xff
+            for b in iter(self.content[:len(self.content)-1]):
+                two_complement_content += (~b & 0xff).to_bytes(1, 'big')
+            two_complement_content += (~self.content[len(self.content)-1] & mask).to_bytes(1, 'big')
+
+        two_complement: Buffer = Buffer(content=two_complement_content, length=self.length, padding=self.padding)
+        return two_complement   
 
 
     def __setitem__(self,items, values):
@@ -423,7 +438,7 @@ def __getitem__(self, items):
         assert isinstance(items, (slice, int))
 
         if isinstance(items, slice):
-            start_bit, stop_bit, _ = items.indices(self.length)
+            start_bit, stop_bit, stride = items.indices(self.length)
 
         else:
             start_bit = items

microschc/crypto/__init__.py

@@ -0,0 +1 @@
+from .crc import CRC32C_TABLE, crc32c

microschc/crypto/crc.py

@@ -0,0 +1,66 @@
+from microschc.binary.buffer import Buffer
+
+
+CRC32C_TABLE = [
+    0x00000000, 0xF26B8303, 0xE13B70F7, 0x1350F3F4, 0xC79A971F,
+    0x35F1141C, 0x26A1E7E8, 0xD4CA64EB, 0x8AD958CF, 0x78B2DBCC,
+    0x6BE22838, 0x9989AB3B, 0x4D43CFD0, 0xBF284CD3, 0xAC78BF27,
+    0x5E133C24, 0x105EC76F, 0xE235446C, 0xF165B798, 0x030E349B,
+    0xD7C45070, 0x25AFD373, 0x36FF2087, 0xC494A384, 0x9A879FA0,
+    0x68EC1CA3, 0x7BBCEF57, 0x89D76C54, 0x5D1D08BF, 0xAF768BBC,
+    0xBC267848, 0x4E4DFB4B, 0x20BD8EDE, 0xD2D60DDD, 0xC186FE29,
+    0x33ED7D2A, 0xE72719C1, 0x154C9AC2, 0x061C6936, 0xF477EA35,
+    0xAA64D611, 0x580F5512, 0x4B5FA6E6, 0xB93425E5, 0x6DFE410E,
+    0x9F95C20D, 0x8CC531F9, 0x7EAEB2FA, 0x30E349B1, 0xC288CAB2,
+    0xD1D83946, 0x23B3BA45, 0xF779DEAE, 0x05125DAD, 0x1642AE59,
+    0xE4292D5A, 0xBA3A117E, 0x4851927D, 0x5B016189, 0xA96AE28A,
+    0x7DA08661, 0x8FCB0562, 0x9C9BF696, 0x6EF07595, 0x417B1DBC,
+    0xB3109EBF, 0xA0406D4B, 0x522BEE48, 0x86E18AA3, 0x748A09A0,
+    0x67DAFA54, 0x95B17957, 0xCBA24573, 0x39C9C670, 0x2A993584,
+    0xD8F2B687, 0x0C38D26C, 0xFE53516F, 0xED03A29B, 0x1F682198,
+    0x5125DAD3, 0xA34E59D0, 0xB01EAA24, 0x42752927, 0x96BF4DCC,
+    0x64D4CECF, 0x77843D3B, 0x85EFBE38, 0xDBFC821C, 0x2997011F,
+    0x3AC7F2EB, 0xC8AC71E8, 0x1C661503, 0xEE0D9600, 0xFD5D65F4,
+    0x0F36E6F7, 0x61C69362, 0x93AD1061, 0x80FDE395, 0x72966096,
+    0xA65C047D, 0x5437877E, 0x4767748A, 0xB50CF789, 0xEB1FCBAD,
+    0x197448AE, 0x0A24BB5A, 0xF84F3859, 0x2C855CB2, 0xDEEEDFB1,
+    0xCDBE2C45, 0x3FD5AF46, 0x7198540D, 0x83F3D70E, 0x90A324FA,
+    0x62C8A7F9, 0xB602C312, 0x44694011, 0x5739B3E5, 0xA55230E6,
+    0xFB410CC2, 0x092A8FC1, 0x1A7A7C35, 0xE811FF36, 0x3CDB9BDD,
+    0xCEB018DE, 0xDDE0EB2A, 0x2F8B6829, 0x82F63B78, 0x709DB87B,
+    0x63CD4B8F, 0x91A6C88C, 0x456CAC67, 0xB7072F64, 0xA457DC90,
+    0x563C5F93, 0x082F63B7, 0xFA44E0B4, 0xE9141340, 0x1B7F9043,
+    0xCFB5F4A8, 0x3DDE77AB, 0x2E8E845F, 0xDCE5075C, 0x92A8FC17,
+    0x60C37F14, 0x73938CE0, 0x81F80FE3, 0x55326B08, 0xA759E80B,
+    0xB4091BFF, 0x466298FC, 0x1871A4D8, 0xEA1A27DB, 0xF94AD42F,
+    0x0B21572C, 0xDFEB33C7, 0x2D80B0C4, 0x3ED04330, 0xCCBBC033,
+    0xA24BB5A6, 0x502036A5, 0x4370C551, 0xB11B4652, 0x65D122B9,
+    0x97BAA1BA, 0x84EA524E, 0x7681D14D, 0x2892ED69, 0xDAF96E6A,
+    0xC9A99D9E, 0x3BC21E9D, 0xEF087A76, 0x1D63F975, 0x0E330A81,
+    0xFC588982, 0xB21572C9, 0x407EF1CA, 0x532E023E, 0xA145813D,
+    0x758FE5D6, 0x87E466D5, 0x94B49521, 0x66DF1622, 0x38CC2A06,
+    0xCAA7A905, 0xD9F75AF1, 0x2B9CD9F2, 0xFF56BD19, 0x0D3D3E1A,
+    0x1E6DCDEE, 0xEC064EED, 0xC38D26C4, 0x31E6A5C7, 0x22B65633,
+    0xD0DDD530, 0x0417B1DB, 0xF67C32D8, 0xE52CC12C, 0x1747422F,
+    0x49547E0B, 0xBB3FFD08, 0xA86F0EFC, 0x5A048DFF, 0x8ECEE914,
+    0x7CA56A17, 0x6FF599E3, 0x9D9E1AE0, 0xD3D3E1AB, 0x21B862A8,
+    0x32E8915C, 0xC083125F, 0x144976B4, 0xE622F5B7, 0xF5720643,
+    0x07198540, 0x590AB964, 0xAB613A67, 0xB831C993, 0x4A5A4A90,
+    0x9E902E7B, 0x6CFBAD78, 0x7FAB5E8C, 0x8DC0DD8F, 0xE330A81A,
+    0x115B2B19, 0x020BD8ED, 0xF0605BEE, 0x24AA3F05, 0xD6C1BC06,
+    0xC5914FF2, 0x37FACCF1, 0x69E9F0D5, 0x9B8273D6, 0x88D28022,
+    0x7AB90321, 0xAE7367CA, 0x5C18E4C9, 0x4F48173D, 0xBD23943E,
+    0xF36E6F75, 0x0105EC76, 0x12551F82, 0xE03E9C81, 0x34F4F86A,
+    0xC69F7B69, 0xD5CF889D, 0x27A40B9E, 0x79B737BA, 0x8BDCB4B9,
+    0x988C474D, 0x6AE7C44E, 0xBE2DA0A5, 0x4C4623A6, 0x5F16D052,
+    0xAD7D5351 
+]
+
+def crc32c(buffer: Buffer, crc_init:int):
+    crc32c = crc_init
+    for c in buffer.chunks(length=8, padding=True):
+        b = c.value()
+        crc32c = (crc32c >> 8)^CRC32C_TABLE[(crc32c^b)&0xff]
+    crc32c_content:bytes = crc32c.to_bytes(4, 'big')
+    crc32c_buffer: Buffer = Buffer(content=crc32c_content, length=32)
+    return crc32c_buffer

microschc/protocol/__init__.py

@@ -6,13 +6,15 @@
 from .ipv4 import IPv4ComputeFunctions, IPv4Fields
 from .ipv6 import IPv6ComputeFunctions, IPv6Fields
 from .udp import UDPComputeFunctions, UDPFields
+from .sctp import SCTPComputeFunctions, SCTPFields
 
 ComputeFunctions: Dict[str, Tuple[ComputeFunctionType, ComputeFunctionDependenciesType]] = {
     IPv4Fields.TOTAL_LENGTH: IPv4ComputeFunctions[IPv4Fields.TOTAL_LENGTH],
     IPv4Fields.HEADER_CHECKSUM: IPv4ComputeFunctions[IPv4Fields.HEADER_CHECKSUM],
     IPv6Fields.PAYLOAD_LENGTH: IPv6ComputeFunctions[IPv6Fields.PAYLOAD_LENGTH],
     UDPFields.LENGTH: UDPComputeFunctions[UDPFields.LENGTH],
-    UDPFields.CHECKSUM: UDPComputeFunctions[UDPFields.CHECKSUM]
+    UDPFields.CHECKSUM: UDPComputeFunctions[UDPFields.CHECKSUM],
+    SCTPFields.CHECKSUM: SCTPComputeFunctions[SCTPFields.CHECKSUM]
 }
 
 

microschc/protocol/sctp.py

@@ -8,15 +8,18 @@
 
 
 from enum import Enum
+from functools import reduce
 
+from microschc.crypto.crc import CRC32C_TABLE, crc32c
 from microschc.protocol.registry import PARSERS, REGISTER_PARSER, ProtocolsIDs
 
 SCTP_HEADER_ID = 'SCTP'
 
 from enum import Enum
 from typing import Dict, List, Tuple, Type
-from microschc.binary.buffer import Buffer
+from microschc.binary.buffer import Buffer, Padding
 from microschc.parser import HeaderParser, ParserError
+from microschc.protocol.compute import ComputeFunctionDependenciesType, ComputeFunctionType
 from microschc.rfc8724 import FieldDescriptor, HeaderDescriptor
 
 SCTP_HEADER_ID = 'SCTP'
@@ -604,9 +607,9 @@ def _parse_parameter(self, buffer: Buffer) -> Tuple[List[FieldDescriptor], int]:
         +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
         |        Parameter Type         |       Parameter Length        |
         +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-        \                                                               \
+        \                                                               \ 
         /                        Parameter Value                        /
-        \                                                               \
+        \                                                               \ 
         +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
         """
         fields: List[FieldDescriptor] = []
@@ -632,4 +635,26 @@ def _parse_parameter(self, buffer: Buffer) -> Tuple[List[FieldDescriptor], int]:
             )
         return fields, parameter_length_value + parameter_padding_length
 
+
+def _compute_checksum(decompressed_fields: List[Tuple[str, Buffer]], rule_field_position: int) -> Buffer:
+    """
+    Checksum algorithm is the Castagnoli CRC32C Checksum Algorithm (CRC32c).
+    """
+    fields_values: List[Buffer] = [field_value for _, field_value in decompressed_fields]
+
+    sctp_checksum_position: int = rule_field_position
+    #   - SCTP checksum is the 4th field of UDP
+    sctp_header_and_payload_fields: List[Buffer] = [field for field in fields_values[sctp_checksum_position-3:]]
+    sctp_header_and_payload: Buffer = reduce(lambda x, y: x+y, sctp_header_and_payload_fields)
+
+    crc_init: int = 0xffffffff    
+    checksum = crc32c(buffer=sctp_header_and_payload, crc_init=crc_init)  
+    checksum = ~checksum
+    checksum_buffer = reduce(lambda x,y : x+y, list(checksum.chunks(length=8))[::-1])
+    return checksum_buffer
+
+SCTPComputeFunctions: Dict[str, Tuple[ComputeFunctionType, ComputeFunctionDependenciesType]] = {
+    SCTPFields.CHECKSUM: (_compute_checksum, { f.value for f in SCTPFields if f is not SCTPFields.CHECKSUM })
+}
+
 REGISTER_PARSER(protocol_id=ProtocolsIDs.SCTP, parser_class=SCTPParser)

tests/binary/test_buffer.py

@@ -371,8 +371,25 @@ def test_and():
     buffer_1_and_1_left: Buffer = buffer_1 & buffer_1_pad_left
     expected_1_and_1_left: Buffer = Buffer(content=b'\x08\x68', length=13, padding=Padding.RIGHT)
     assert buffer_1_and_1_left == expected_1_and_1_left
-
-
+
+def test_complement():
+    buffer: Buffer = Buffer(content=b'\x01\xff\xf0', length=24)
+    complement = ~buffer
+    expected_buffer = Buffer(content=b'\xfe\x00\x0f', length=24)
+    assert complement == expected_buffer
+
+def test_complement_padding_left():
+    buffer: Buffer = Buffer(content=b'\x0f\xff\xf0', length=20)
+    complement = ~buffer
+    expected_buffer = Buffer(content=b'\x00\x00\x0f', length=20)
+    assert complement == expected_buffer
+
+def test_complement_padding_right():
+    buffer: Buffer = Buffer(content=b'\x0f\xff\x80', length=20, padding=Padding.RIGHT)
+    complement = ~buffer
+    expected_buffer = Buffer(content=b'\xf0\x00\x70', length=20, padding=Padding.RIGHT)
+    assert complement == expected_buffer
+
 def test_value():
 
     buffer: Buffer = Buffer(content=b'\x00\x01', length=16)

tests/protocol/test_sctp.py

@@ -1,5 +1,5 @@
 from typing import Dict, List, Tuple
-from microschc.protocol.sctp import SCTPParser, SCTPFields
+from microschc.protocol.sctp import SCTPParser, SCTPFields, SCTPComputeFunctions
 from microschc.parser.parser import HeaderDescriptor
 from microschc.rfc8724 import FieldDescriptor
 from microschc.binary.buffer import Buffer
@@ -1104,4 +1104,23 @@ def test_sctp_parser_parse_cookie_ack():
     chunk_length_fd:FieldDescriptor = sctp_header_descriptor.fields[6]
     assert chunk_length_fd.id == SCTPFields.CHUNK_LENGTH
     assert chunk_length_fd.position == 0
-    assert chunk_length_fd.value == Buffer(content=b'\x00\x04', length=16)
+    assert chunk_length_fd.value == Buffer(content=b'\x00\x04', length=16)
+
+def test_sctp_compute_checksum():
+
+    partially_reconstructed_content: bytes = bytes(
+        b'\x00\x07\x00\x07\x00\x00\x00\x00\x00\x00\x00\x00\x01\x00\x00\x20'
+        b'\x43\x23\x25\x44\x00\x00\xff\xff\x00\x11\x00\x11\x5c\xfe\x37\x9f'
+        b'\xc0\x00\x00\x04\x00\x0c\x00\x06\x00\x05\x00\x00'
+
+    )
+    expected_checksum: Buffer = Buffer(content=b'\x37\x61\xa7\x46', length=32)
+    parser:SCTPParser = SCTPParser()
+
+    partially_reconstructed_packet: Buffer = Buffer(content=partially_reconstructed_content, length=len(partially_reconstructed_content)*8)
+    sctp_header_descriptor: HeaderDescriptor = parser.parse(buffer=partially_reconstructed_packet)
+
+
+    decompressed_fields: List[Tuple[str, Buffer]] = [ (field.id,field.value) for field in sctp_header_descriptor.fields]
+    checksum_buffer: Buffer = SCTPComputeFunctions[SCTPFields.CHECKSUM][0](decompressed_fields, 3)
+    assert checksum_buffer == expected_checksum