forked from openrs2/openrs2
You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
72 lines
2.6 KiB
72 lines
2.6 KiB
4 years ago
|
# Protocol overview
|
||
|
|
|
||
|
|
The RuneScape protocol runs on top of the [Transmission Control Protocol
|
||
|
|
(TCP)][tcp]. As TCP is stream-oriented, a framing scheme is required to
|
||
|
|
determine where one packet ends and where the next begins. RuneScape primarily
|
||
|
|
uses a [type-length-value (TLV)][tlv] scheme for framing, though some
|
||
|
|
exceptions do exist - for example, the JAGGRAB and JS5 protocols use different
|
||
|
|
framing schemes.
|
||
|
|
|
||
|
|
A RuneScape connection may be in several states, each of which has a different
|
||
|
|
set of opcodes (types in TLV parlance). Opcodes may have different meanings in
|
||
|
|
different states. Opcodes may be optionally encrypted with the [ISAAC stream
|
||
|
|
cipher][isaac].
|
||
|
|
|
||
|
|
All connections start in the [login](login.md) state.
|
||
|
|
|
||
|
|
## Types
|
||
|
|
|
||
|
|
There are three types of packets:
|
||
|
|
|
||
|
|
* Fixed length - supports any payload length, including no payload.
|
||
|
|
* Variable length (byte) - supports up to 255 bytes of payload.
|
||
|
|
* Variable length (short) - supports up to 65,535 bytes of payload in theory,
|
||
|
|
though in practice the client's receive buffer limits the payload to 5,000
|
||
|
|
bytes in the 550 build. This limit is raised by OpenRS2's client patcher.
|
||
|
|
|
||
|
|
They are structured as follows:
|
||
|
|
|
||
|
|
### Fixed length
|
||
|
|
|
||
|
|
| Data type | Description |
|
||
|
|
|--------------|-------------|
|
||
|
|
| UnsignedByte | Opcode |
|
||
|
|
| Byte\[len\] | Payload |
|
||
|
|
|
||
|
|
### Variable length (byte)
|
||
|
|
|
||
|
|
| Data type | Description |
|
||
|
|
|--------------|--------------|
|
||
|
|
| UnsignedByte | Opcode |
|
||
|
|
| UnsignedByte | Length (len) |
|
||
|
|
| Byte\[len\] | Payload |
|
||
|
|
|
||
|
|
### Variable length (short)
|
||
|
|
|
||
|
|
| Data type | Description |
|
||
|
|
|---------------|--------------|
|
||
|
|
| UnsignedByte | Opcode |
|
||
|
|
| UnsignedShort | Length (len) |
|
||
|
|
| Byte\[len\] | Payload |
|
||
|
|
|
||
|
|
## Opcode encryption
|
||
|
|
|
||
|
|
Opcodes are encrypted by adding the opcode to the next 32-bit output from the
|
||
|
|
ISAAC random number generator and truncating the result to 8 bits. Decryption
|
||
|
|
is the same process in reverse: the 32-bit output is subtracted from the
|
||
|
|
encrypted opcode, and then the result is truncated to 8 bits.
|
||
|
|
|
||
|
|
There are two ISAAC random number generators: one used for upstream (client ->
|
||
|
|
server) traffic and one used for downstream (server -> client) traffic. Both
|
||
|
|
are initialised with a seed consisting of four 32-bit integers.
|
||
|
|
|
||
|
|
The upstream seed is the same as the downstream seed, except each integer
|
||
|
|
component is incremented by 50.
|
||
|
|
|
||
|
|
The seed is negotiated during the login process. Before it is negotiated,
|
||
|
|
opcodes are not encrypted.
|
||
|
|
|
||
|
|
[isaac]: https://burtleburtle.net/bob/rand/isaacafa.html
|
||
|
|
[tcp]: https://en.wikipedia.org/wiki/Transmission_Control_Protocol
|
||
|
|
[tlv]: https://en.wikipedia.org/wiki/Type-length-value
|