Add Minecraft input plugin (#2960)

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

@@ -0,0 +1,200 @@
+// 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
+}