telegraf/plugins/inputs/minecraft/internal/rcon/rcon.go

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2017-06-23 23:54:12 +00:00
// Package rcon implements the communication protocol for communicating
// with RCON servers. Tested and working with Valve game servers.
package rcon
import (
"bytes"
"crypto/rand"
"encoding/binary"
"errors"
"fmt"
"net"
"strings"
)
const (
PacketPaddingSize uint8 = 2 // Size of Packet's padding.
PacketHeaderSize uint8 = 8 // Size of Packet's header.
)
const (
TerminationSequence = "\x00" // Null empty ASCII string suffix.
)
// Packet type constants.
// https://developer.valvesoftware.com/wiki/Source_RCON_Protocol#Packet_Type
const (
Exec int32 = 2
Auth int32 = 3
AuthResponse int32 = 2
ResponseValue int32 = 0
)
// Rcon package errors.
var (
ErrInvalidWrite = errors.New("Failed to write the payload corretly to remote connection.")
ErrInvalidRead = errors.New("Failed to read the response corretly from remote connection.")
ErrInvalidChallenge = errors.New("Server failed to mirror request challenge.")
ErrUnauthorizedRequest = errors.New("Client not authorized to remote server.")
ErrFailedAuthorization = errors.New("Failed to authorize to the remote server.")
)
type Client struct {
Host string // The IP address of the remote server.
Port int // The Port the remote server's listening on.
Authorized bool // Has the client been authorized by the server?
Connection net.Conn // The TCP connection to the server.
}
type Header struct {
Size int32 // The size of the payload.
Challenge int32 // The challenge ths server should mirror.
Type int32 // The type of request being sent.
}
type Packet struct {
Header Header // Packet header.
Body string // Body of packet.
}
// Compile converts a packets header and body into its approriate
// byte array payload, returning an error if the binary packages
// Write method fails to write the header bytes in their little
// endian byte order.
func (p Packet) Compile() (payload []byte, err error) {
var size int32 = p.Header.Size
var buffer bytes.Buffer
var padding [PacketPaddingSize]byte
if err = binary.Write(&buffer, binary.LittleEndian, &size); nil != err {
return
} else if err = binary.Write(&buffer, binary.LittleEndian, &p.Header.Challenge); nil != err {
return
} else if err = binary.Write(&buffer, binary.LittleEndian, &p.Header.Type); nil != err {
return
}
buffer.WriteString(p.Body)
buffer.Write(padding[:])
return buffer.Bytes(), nil
}
// NewPacket returns a pointer to a new Packet type.
func NewPacket(challenge, typ int32, body string) (packet *Packet) {
size := int32(len([]byte(body)) + int(PacketHeaderSize+PacketPaddingSize))
return &Packet{Header{size, challenge, typ}, body}
}
// Authorize calls Send with the appropriate command type and the provided
// password. The response packet is returned if authorization is successful
// or a potential error.
func (c *Client) Authorize(password string) (response *Packet, err error) {
if response, err = c.Send(Auth, password); nil == err {
if response.Header.Type == AuthResponse {
c.Authorized = true
} else {
err = ErrFailedAuthorization
response = nil
return
}
}
return
}
// Execute calls Send with the appropriate command type and the provided
// command. The response packet is returned if the command executed successfully
// or a potential error.
func (c *Client) Execute(command string) (response *Packet, err error) {
return c.Send(Exec, command)
}
// Sends accepts the commands type and its string to execute to the clients server,
// creating a packet with a random challenge id for the server to mirror,
// and compiling its payload bytes in the appropriate order. The resonse is
// decompiled from its bytes into a Packet type for return. An error is returned
// if send fails.
func (c *Client) Send(typ int32, command string) (response *Packet, err error) {
if typ != Auth && !c.Authorized {
err = ErrUnauthorizedRequest
return
}
// Create a random challenge for the server to mirror in its response.
var challenge int32
binary.Read(rand.Reader, binary.LittleEndian, &challenge)
// Create the packet from the challenge, typ and command
// and compile it to its byte payload
packet := NewPacket(challenge, typ, command)
payload, err := packet.Compile()
var n int
if nil != err {
return
} else if n, err = c.Connection.Write(payload); nil != err {
return
} else if n != len(payload) {
err = ErrInvalidWrite
return
}
var header Header
if err = binary.Read(c.Connection, binary.LittleEndian, &header.Size); nil != err {
return
} else if err = binary.Read(c.Connection, binary.LittleEndian, &header.Challenge); nil != err {
return
} else if err = binary.Read(c.Connection, binary.LittleEndian, &header.Type); nil != err {
return
}
if packet.Header.Type == Auth && header.Type == ResponseValue {
// Discard, empty SERVERDATA_RESPOSE_VALUE from authorization.
c.Connection.Read(make([]byte, header.Size-int32(PacketHeaderSize)))
// Reread the packet header.
if err = binary.Read(c.Connection, binary.LittleEndian, &header.Size); nil != err {
return
} else if err = binary.Read(c.Connection, binary.LittleEndian, &header.Challenge); nil != err {
return
} else if err = binary.Read(c.Connection, binary.LittleEndian, &header.Type); nil != err {
return
}
}
if header.Challenge != packet.Header.Challenge {
err = ErrInvalidChallenge
return
}
body := make([]byte, header.Size-int32(PacketHeaderSize))
n, err = c.Connection.Read(body)
if nil != err {
return
} else if n != len(body) {
err = ErrInvalidRead
return
}
response = new(Packet)
response.Header = header
response.Body = strings.TrimRight(string(body), TerminationSequence)
return
}
// NewClient creates a new Client type, creating the connection
// to the server specified by the host and port arguements. If
// the connection fails, an error is returned.
func NewClient(host string, port int) (client *Client, err error) {
client = new(Client)
client.Host = host
client.Port = port
client.Connection, err = net.Dial("tcp", fmt.Sprintf("%v:%v", client.Host, client.Port))
return
}