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Packet handling order of operations notes

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This commit is contained in:
Emily 2020-04-04 23:12:24 +02:00
parent 37e732e19f
commit 0cd474601a
2 changed files with 25 additions and 6 deletions
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19
notes/packet_writeup.md
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@ -11,6 +11,25 @@
## Shared ## Shared
* Can be internal packet * Can be internal packet
* If packet is smaller then 3 bytes; forward to plugin handlers (*)before handling them (len(data) <= 2)
## Order of operations
1. Check if banned (if true, cancel rest and handle) [^1]
2. If first byte in data is (0x19, 0x1d, 0x1f, 0x24 or 0x18) custom code flow required [^2]
3. HandleSocketReceiveFromConnectedPlayer (cancel rest if handled)
4. Check if cheat (modified) packet (unexpected at this time, there are some packets we can expect) [^3]
[^1]: this could be changed in custom implementation (dont allow inital connection instead)
[^2]: if (0x18 and length == 2) or (0x19 and length <= 2):
handle packet and return
elif (0x1d or 0x1f or 0x24) and length <= 2:
handle packet, but continue
[^3]: if ((0x18 or 0x1a) and length <= 3) or ((0x19 or 0x1d) and length <= 2) or
((0x08 or 0x07 or 0x27) and length >= 5) or (0x37 and length < 400):
We expect this packet, everything is ok?
else:
This is a cheat (modified / injected) packet that should not arrive at this time
Send a packet to client that you received a modified packet (0x26)
# Internal packet # Internal packet
|condition|name|bit length|type|notes| |condition|name|bit length|type|notes|

12
sampy/client/player.py
View File

@ -8,16 +8,19 @@ logger = logging.getLogger(__name__)
STATE_CONNECTING = 0 STATE_CONNECTING = 0
STATE_AUTH = 1 STATE_AUTH = 1
STATE_CONNECTED = 2
class PlayerClient(BaseClient): class PlayerClient(BaseClient):
def __init__(self, server: "__ServerInstance__", ip: str, port: int): def __init__(self, server: "__ServerInstance__", ip: str, port: int):
super().__init__(server, ip, port) super().__init__(server, ip, port)
logger.debug("Client resolved to PlayerClient") logger.debug("Client resolved to PlayerClient")
# TODO: check if banned and handle here
self.state = STATE_CONNECTING self.state = STATE_CONNECTING
self.handlers = { self.handlers = {
0x18: self.on_connection_request, STATE_CONNECTING: self.on_connection_request,
#0x00: self.on_state_dependent_handle #0x00: self.on_state_dependent_handle
} }
@ -26,10 +29,7 @@ class PlayerClient(BaseClient):
try: try:
packet = self.server.compressor.decompress(packet) packet = self.server.compressor.decompress(packet)
await self.handlers.get(self.state, self.on_unimplemented)(packet)
await self.handlers.get(packet[0], self.on_unimplemented)(packet)
except Exception as err: except Exception as err:
logger.error(err) logger.error(err)
@ -54,7 +54,7 @@ class PlayerClient(BaseClient):
logger.debug("challenge: passed") logger.debug("challenge: passed")
self.state = STATE_AUTH self.state = STATE_CONNECTED
await self.send(b"\x19\x00") # Challenge passed await self.send(b"\x19\x00") # Challenge passed
async def parse_internal_packet(self, packet: bytes): async def parse_internal_packet(self, packet: bytes):