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480 行
14 KiB
480 行
14 KiB
package main
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// TODO learn more about chan chan's
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// http://marcio.io/2015/07/handling-1-million-requests-per-minute-with-golang/
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import (
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"bufio"
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"bytes"
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"crypto/rand"
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"encoding/base64"
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"flag"
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"fmt"
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"io"
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"io/ioutil"
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"net"
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"net/http"
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"net/url"
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"os"
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"strconv"
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"strings"
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"sync"
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"time"
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"github.com/emicklei/go-restful"
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"gopkg.in/yaml.v2"
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)
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// I'm not sure how to pass nested structs, so I de-nested this.
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// TODO Learn if passing nested structs is desirable?
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type Conf struct {
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Addr string `yaml:"addr,omitempty"`
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Port uint `yaml:"port,omitempty"`
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Mailer ConfMailer
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RootPath string `yaml:"root_path,omitempty"`
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}
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type ConfMailer struct {
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Url string `yaml:"url,omitempty"`
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ApiKey string `yaml:"api_key,omitempty"`
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From string `yaml:"from,omitempty"`
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}
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// So we can peek at net.Conn, which we can't do natively
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// https://stackoverflow.com/questions/51472020/how-to-get-the-size-of-available-tcp-data
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type bufferedConn struct {
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r *bufio.Reader
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rout io.Reader // See https://github.com/polvi/sni/blob/master/sni.go#L135
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net.Conn
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}
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func newBufferedConn(c net.Conn) bufferedConn {
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return bufferedConn{bufio.NewReader(c), nil, c}
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}
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func (b bufferedConn) Peek(n int) ([]byte, error) {
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return b.r.Peek(n)
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}
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func (b bufferedConn) Buffered() int {
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return b.r.Buffered()
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}
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func (b bufferedConn) Read(p []byte) (int, error) {
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if b.rout != nil {
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return b.rout.Read(p)
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}
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return b.r.Read(p)
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}
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type chatMsg struct {
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sender net.Conn
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Message string `json:"message"`
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ReceivedAt time.Time `json:"received_at"`
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Channel string `json:"channel"`
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User string `json:"user"`
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}
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// Poor-Man's container/ring (circular buffer)
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type chatHist struct {
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msgs []*chatMsg
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i int // current index
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c int // current count (number of elements)
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}
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// Multi-use
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var config Conf
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var virginConns chan net.Conn
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var gotClientHello chan bufferedConn
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var myChatHist chatHist
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var broadcastMsg chan chatMsg
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// Telnet
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var wantsServerHello chan bufferedConn
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var authTelnet chan telnetUser
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var cleanTelnet chan telnetUser
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// HTTP
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var demuxHttpClient chan bufferedConn
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var authChallenge chan authReq
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var valAuthReqs chan authReq
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var delAuthReqs chan authReq
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func usage() {
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fmt.Fprintf(os.Stderr, "\nusage: go run chatserver.go\n")
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flag.PrintDefaults()
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fmt.Println()
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os.Exit(1)
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}
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// https://blog.questionable.services/article/generating-secure-random-numbers-crypto-rand/
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func genAuthCode() (string, error) {
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n := 12
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b := make([]byte, n)
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_, err := rand.Read(b)
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// Note that err == nil only if we read len(b) bytes.
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if err != nil {
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return "", err
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}
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return base64.URLEncoding.EncodeToString(b), nil
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}
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func muxTcp(conn bufferedConn) {
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// Wish List for protocol detection
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// * PROXY protocol (and loop)
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// * HTTP CONNECT (proxy) (and loop)
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// * tls (and loop) https://github.com/polvi/sni
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// * http/ws
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// * irc
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// * fallback to telnet
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// At this piont we've already at least one byte via Peek()
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// so the first packet is available in the buffer
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// Note: Realistically no tls/http/irc client is going to send so few bytes
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// (and no router is going to chunk so small)
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// that it cannot reasonably detect the protocol in the first packet
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// However, typical MTU is 1,500 and HTTP can have a 2k URL
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// so expecting to find the "HTTP/1.1" in the Peek is not always reasonable
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n := conn.Buffered()
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firstMsg, err := conn.Peek(n)
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if nil != err {
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conn.Close()
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return
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}
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var protocol string
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// between A and z
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if firstMsg[0] >= 65 && firstMsg[0] <= 122 {
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i := bytes.Index(firstMsg, []byte(" /"))
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if -1 != i {
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protocol = "HTTP"
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// very likely HTTP
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j := bytes.IndexAny(firstMsg, "\r\n")
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if -1 != j {
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k := bytes.Index(bytes.ToLower(firstMsg[:j]), []byte("HTTP/1"))
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if -1 != k {
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// positively HTTP
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}
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}
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}
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} else if 0x16 /*22*/ == firstMsg[0] {
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// Because I don't always remember off the top of my head what the first byte is
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// http://blog.fourthbit.com/2014/12/23/traffic-analysis-of-an-ssl-slash-tls-session
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// https://tlseminar.github.io/first-few-milliseconds/
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// TODO I want to learn about ALPN
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protocol = "TLS"
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}
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if "" == protocol {
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fmt.Fprintf(conn, "\n\nWelcome to Sample Chat! You're not an HTTP client, assuming Telnet.\nYou must authenticate via email to participate\n\nEmail: ")
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wantsServerHello <- conn
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return
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} else if "HTTP" != protocol {
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defer conn.Close()
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fmt.Fprintf(conn, "\n\nNot yet supported. Try HTTP or Telnet\n\n")
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return
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}
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demuxHttpClient <- conn
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}
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func testForHello(netConn net.Conn) {
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ts := time.Now()
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fmt.Fprintf(os.Stdout, "[New Connection] (%s) welcome %s\n", ts, netConn.RemoteAddr().String())
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m := sync.Mutex{}
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virgin := true
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bufConn := newBufferedConn(netConn)
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go func() {
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// Cause first packet to be loaded into buffer
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_, err := bufConn.Peek(1)
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if nil != err {
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panic(err)
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}
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m.Lock()
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if virgin {
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virgin = false
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gotClientHello <- bufConn
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} else {
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wantsServerHello <- bufConn
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}
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m.Unlock()
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}()
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// Wait for a hello packet of some sort from the client
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// (obviously this wouldn't work in extremely high latency situations)
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time.Sleep(250 * 1000000)
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// If we still haven't received data from the client
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// assume that the client must be expecting a welcome from us
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m.Lock()
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if virgin {
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virgin = false
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// Defer as to not block and prolonging the mutex
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// (not that those few cycles much matter...)
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defer fmt.Fprintf(netConn,
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"\n\nWelcome to Sample Chat! You appear to be using Telnet (http is also available on this port)."+
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"\nYou must authenticate via email to participate\n\nEmail: ")
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}
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m.Unlock()
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}
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func sendAuthCode(cnf ConfMailer, to string) (string, error) {
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code, err := genAuthCode()
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if nil != err {
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return "", err
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}
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// TODO use go text templates with HTML escaping
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text := "Your authorization code:\n\n" + code
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html := "Your authorization code:<br><br>" + code
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// https://stackoverflow.com/questions/24493116/how-to-send-a-post-request-in-go
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// https://stackoverflow.com/questions/16673766/basic-http-auth-in-go
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client := http.Client{}
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form := url.Values{}
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form.Add("from", cnf.From)
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form.Add("to", to)
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form.Add("subject", "Sample Chat Auth Code: "+code)
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form.Add("text", text)
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form.Add("html", html)
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req, err := http.NewRequest("POST", cnf.Url, strings.NewReader(form.Encode()))
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if nil != err {
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return "", err
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}
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//req.PostForm = form ??
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req.Header.Add("User-Agent", "golang http.Client - Sample Chat App Authenticator")
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req.Header.Add("Content-Type", "application/x-www-form-urlencoded")
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req.SetBasicAuth("api", cnf.ApiKey)
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resp, err := client.Do(req)
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if nil != err {
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return "", err
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}
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defer resp.Body.Close()
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// Security XXX
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// we trust mailgun implicitly and this is just a demo
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// hence no DoS check on body size for now
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body, err := ioutil.ReadAll(resp.Body)
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if nil != err {
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return "", err
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}
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if resp.StatusCode < 200 || resp.StatusCode >= 300 || "{" != string(body[0]) {
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fmt.Fprintf(os.Stdout, "[Mailgun] Uh-oh...\n[Maigun] Baby Brent says: %s\n", body)
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}
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return code, nil
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}
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func main() {
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flag.Usage = usage
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port := flag.Uint("port", 0, "tcp telnet chat port")
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confname := flag.String("conf", "./config.yml", "yaml config file")
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flag.Parse()
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confstr, err := ioutil.ReadFile(*confname)
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fmt.Fprintf(os.Stdout, "-conf=%s\n", *confname)
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if nil != err {
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fmt.Fprintf(os.Stderr, "%s\nUsing defaults instead\n", err)
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confstr = []byte("{\"port\":" + strconv.Itoa(int(*port)) + "}")
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}
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err = yaml.Unmarshal(confstr, &config)
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if nil != err {
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config = Conf{}
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}
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if "" == config.RootPath {
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// TODO Maybe embed the public dir into the binary
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// (and provide a flag with path for override - like gitea)
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config.RootPath = "./public"
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}
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// The magical sorting hat
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virginConns = make(chan net.Conn, 128)
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// TCP & Authentication
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telnetConns := make(map[bufferedConn]telnetUser)
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wantsServerHello = make(chan bufferedConn, 128)
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authTelnet = make(chan telnetUser, 128)
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// HTTP & Authentication
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myAuthReqs := make(map[string]authReq)
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authReqs = make(chan authReq, 128)
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valAuthReqs = make(chan authReq, 128)
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delAuthReqs = make(chan authReq, 128)
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gotClientHello = make(chan bufferedConn, 128)
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demuxHttpClient = make(chan bufferedConn, 128)
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//myRooms["general"] = make(chan chatMsg, 128)
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// Note: I had considered dynamically select on channels for rooms.
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// https://stackoverflow.com/questions/19992334/how-to-listen-to-n-channels-dynamic-select-statement
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// I don't think that's actually the best approach, but I just wanted to save the link
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broadcastMsg = make(chan chatMsg, 128)
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myChatHist.msgs = make([]*chatMsg, 128)
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var addr string
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if 0 != int(*port) {
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addr = config.Addr + ":" + strconv.Itoa(int(*port))
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} else {
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addr = config.Addr + ":" + strconv.Itoa(int(config.Port))
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}
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// https://golang.org/pkg/net/#Conn
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sock, err := net.Listen("tcp", addr)
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if nil != err {
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fmt.Fprintf(os.Stderr, "Couldn't bind to TCP socket %q: %s\n", addr, err)
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os.Exit(2)
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}
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fmt.Println("Listening on", addr)
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go func() {
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for {
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conn, err := sock.Accept()
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if err != nil {
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// Not sure what kind of error this could be or how it could happen.
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// Could a connection abort or end before it's handled?
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fmt.Fprintf(os.Stderr, "Error accepting connection:\n%s\n", err)
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}
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virginConns <- conn
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}
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}()
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// Learning by Example
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// https://github.com/emicklei/go-restful/blob/master/examples/restful-multi-containers.go
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// https://github.com/emicklei/go-restful/blob/master/examples/restful-basic-authentication.go
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// https://github.com/emicklei/go-restful/blob/master/examples/restful-serve-static.go
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// https://github.com/emicklei/go-restful/blob/master/examples/restful-pre-post-filters.go
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container := restful.NewContainer()
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wsStatic := new(restful.WebService)
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wsStatic.Path("/")
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wsStatic.Route(wsStatic.GET("/").To(serveStatic))
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wsStatic.Route(wsStatic.GET("/{subpath:*}").To(serveStatic))
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container.Add(wsStatic)
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cors := restful.CrossOriginResourceSharing{ExposeHeaders: []string{"Authorization"}, CookiesAllowed: false, Container: container}
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wsApi := new(restful.WebService)
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wsApi.Path("/api").Consumes(restful.MIME_JSON).Produces(restful.MIME_JSON).Filter(cors.Filter)
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wsApi.Route(wsApi.GET("/hello").To(serveHello))
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wsApi.Route(wsApi.POST("/sessions").To(requestAuth))
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wsApi.Route(wsApi.POST("/sessions/{cid}").To(issueToken))
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wsApi.Route(wsApi.GET("/rooms/{room}").Filter(requireToken).To(listMsgs))
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wsApi.Route(wsApi.POST("/rooms/{room}").Filter(requireToken).To(postMsg))
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container.Add(wsApi)
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server := &http.Server{
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Addr: addr,
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Handler: container,
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}
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myHttpServer := newHttpServer(sock)
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go func() {
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server.Serve(myHttpServer)
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}()
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// Main event loop handling most access to shared data
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for {
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select {
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case conn := <-virginConns:
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// This is short lived
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go testForHello(conn)
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case u := <-authTelnet:
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// allow to receive messages
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// (and be counted among the users)
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telnetConns[u.bufConn] = u
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// is chan chan the right way to handle this?
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u.userCount <- len(telnetConns)
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broadcastMsg <- chatMsg{
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sender: nil,
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Message: fmt.Sprintf("<%s> joined #general\r\n", u.email),
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ReceivedAt: time.Now(),
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Channel: "general",
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User: "system",
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}
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case ar := <-authReqs:
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myAuthReqs[ar.Cid] = ar
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case ar := <-valAuthReqs:
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// TODO In this case it's probably more conventional (and efficient) to
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// use struct with a mutex and the authReqs map than a chan chan
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av, ok := myAuthReqs[ar.Cid]
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//ar.Chan <- nil // TODO
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if ok {
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ar.Chan <- av
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} else {
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// sending empty object so that I can still send a copy
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// rather than a pointer above. Maybe not the right way
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// to do this, but it works for now.
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ar.Chan <- authReq{}
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}
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case ar := <-delAuthReqs:
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delete(myAuthReqs, ar.Cid)
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case bufConn := <-wantsServerHello:
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go handleTelnetConn(bufConn)
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case u := <-cleanTelnet:
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close(u.newMsg)
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// we can safely ignore this error, if any
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u.bufConn.Close()
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delete(telnetConns, u.bufConn)
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case bufConn := <-gotClientHello:
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go muxTcp(bufConn)
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case bufConn := <-demuxHttpClient:
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// this will be Accept()ed immediately by the go-restful container
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// NOTE: we don't store these HTTP connections for broadcast
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// since we manage the session by HTTP Auth Bearer rather than TCP
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myHttpServer.chans <- bufConn
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case msg := <-broadcastMsg:
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// copy comes in, pointer gets saved (and not GC'd, I hope)
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myChatHist.msgs[myChatHist.i] = &msg
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myChatHist.i += 1
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if myChatHist.c < cap(myChatHist.msgs) {
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myChatHist.c += 1
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}
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myChatHist.i %= len(myChatHist.msgs)
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// print the system message (the "log")
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t := msg.ReceivedAt
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tf := "%d-%02d-%02d %02d:%02d:%02d (%s)"
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var sender string
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if nil != msg.sender {
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sender = msg.sender.RemoteAddr().String()
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} else {
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sender = "system"
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}
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// Tangential thought:
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// I wonder if we could use IP detection to get a Telnet client's tz
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// ... could probably make time for this in the authentication loop
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zone, _ := msg.ReceivedAt.Zone()
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fmt.Fprintf(os.Stdout, tf+" [%s] (%s): %s\r\n",
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t.Year(), t.Month(), t.Day(),
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t.Hour(), t.Minute(), t.Second(), zone,
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sender,
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msg.User, msg.Message)
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for _, u := range telnetConns {
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// Don't echo back to the original client
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if msg.sender == u.bufConn {
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continue
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}
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msg := fmt.Sprintf(tf+" [%s]: %s", t.Year(), t.Month(), t.Day(), t.Hour(),
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t.Minute(), t.Second(), zone, msg.User, msg.Message)
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select {
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case u.newMsg <- msg:
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// all is well, client was ready to receive
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default:
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// Rate Limit: Reasonable poor man's DoS prevention (Part 2)
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// This client's send channel buffer is full.
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// It is consuming data too slowly. It may be malicious.
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// In the case that it's experiencing network issues,
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// well, these things happen when you're having network issues.
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// It can reconnect.
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cleanTelnet <- u
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}
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}
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}
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}
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}
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