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RAP protocol

RAP stands for the Remote Access Protocol of Radare2, it is compatible with radare1 and it simply defines a communication between a client and a server to simulate IO operations.

There are two different implementations, one in C and another in Python.

Usage example

Start in one terminal the following command to wait for incoming connections:

r2 rap://:9999

In another machine or terminal connect it:

r2 rap://localhost:9999//bin/ls

As you see, the path of the remote file to load must be specified, and this handled by the open() packet.

Known Bugs

  • Read/Write operations ignore the filedescriptor completely because it is supposed to be handled by the IO layer and it is redundant, but it introduces a bug that breaks support for multiple files.
  • This can be fixed with a new packet type RAP_SETFD.
  • Read lengths should be only 2 bytes, there's no sense in read > 64K of memory in a shot.
  • Seek does not returns anything
  • System vs Cmd - the first should have a return value as well as string result
  • Filedescriptors are assumed to be 32bit

Operations

The protocol is designed to be bidirectional, but right now, only one way is supported. The client sends a byte specifying the operation and the server will reply the same byte masked with the RMT_REPLY value (0x80 | op)

RAP_OPEN   = 1
RAP_READ   = 2
RAP_WRITE  = 3
RAP_SEEK   = 4
RAP_CLOSE  = 5
RAP_SYSTEM = 6
RAP_CMD    = 7
RAP_REPLY  = 0x80

This is how are constructed the packets:

RAP_OPEN
	struct packed RapOpen {
		ut8 op = 1;
		ut8 rw = 0; // 0 = read-only, 1 = read-write
		ut8 len = 15; // length of filename
	}
	>> 01 RW LN [....]
	<< 81 FD=(.. .. .. ..)

RAP_READ
	>> 02 LN=(.. .. .. ..)
	<< 82 LN=(.. .. .. ..) [..LN..]

RAP_WRITE
	>> 03 LN=(.. .. .. ..) [..LN..]
	<< 83 LN=(.. .. .. ..)

RAP_SEEK
	>> 04 FLAG=(..) OFFSET=(.. 8 bytes ..)
	<< 84

RAP_CLOSE
	>> 05 FD=(4 bytes)
	<< 85 RET=(4 bytes)

RAP_SYSTEM
	>> 06 LEN=(4 bytes) STR[LEN bytes]
	<< 86 LN=(.. .. .. ..) STR[ LEN bytes]

RAP_CMD_
	>> 07 LEN=(4 bytes) STR[LEN bytes]
	<< 87 LN=(.. .. .. ..) STR[ LEN bytes]

Examples

Python:

See radare2-bindings/python/remote.py and test-rap-*.py

C:

Server: libr/socket/rap_server.c
Client: libr/io/p/io_rap.c