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package main
import (
"context"
"encoding/json"
"fmt"
"net"
"net/http"
"reflect"
"strings"
"time"
jww "github.com/spf13/jwalterweatherman"
)
const (
APP_CTX_KEY = "app"
)
// tcpKeepAliveListener sets TCP keep-alive timeouts on accepted
// connections. It's used by ListenAndServe and ListenAndServeTLS so
// dead TCP connections (e.g. closing laptop mid-download) eventually
// go away.
type tcpKeepAliveListener struct {
*net.TCPListener
}
func (ln tcpKeepAliveListener) Accept() (c net.Conn, err error) {
tc, err := ln.AcceptTCP()
if err != nil {
return
}
tc.SetKeepAlive(true)
tc.SetKeepAlivePeriod(3 * time.Minute)
return tc, nil
}
// Do the same thing ListenAndServe does but allow passing in the listener
// instead of the address so that we can bind privileged ports before dropping
// permissions to start the server itself.
func ListenAndServeRaw(ln net.Listener, handler http.Handler) error {
server := &http.Server{Addr: ln.Addr().String(), Handler: handler}
return server.Serve(tcpKeepAliveListener{ln.(*net.TCPListener)})
}
// Handler that pushes the application context onto the request context stack
// so that it's available to all other handlers in the stack.
type ContextAwareHandler struct {
ctx *appContext
handler http.HandlerFunc
}
func (h ContextAwareHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
defaultHeaders(w)
h.handler(w, r.WithContext(context.WithValue(r.Context(), APP_CTX_KEY, h.ctx)))
}
// Handler that is able to inspect the application context and print out the
// value of specific fields.
type ContextPrintingHandler struct {
ctx *appContext
field string
}
func (h ContextPrintingHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
defaultHeaders(w)
c := reflect.ValueOf(h.ctx)
f := reflect.Indirect(c).FieldByName(h.field)
switch i := f.Interface().(type) {
case fmt.Stringer:
fmt.Fprintln(w, i.String())
case *string:
if i == nil {
fmt.Fprintln(w, "")
} else {
fmt.Fprintln(w, *i)
}
default:
fmt.Fprintln(w, i)
}
}
// Print default headers for JSON data
func defaultHeaders(w http.ResponseWriter) {
w.Header().Set("Content-Type", "text/plain")
w.Header().Set("Server", "EC2ws")
w.Header().Set("Connection", "close")
}
// Write out JSON data in formatted form or an error
func writeHTTPJson(w http.ResponseWriter, data interface{}, name string) {
jd, err := json.MarshalIndent(data, "", " ")
if err != nil {
jww.ERROR.Printf("Error marshaling json in %s: %s", name, err)
http.Error(w, err.Error(), http.StatusInternalServerError)
}
fmt.Fprintf(w, string(jd))
}
// Get the application context from the request context
func getAppCtx(r *http.Request) *appContext {
return r.Context().Value(APP_CTX_KEY).(*appContext)
}
// Handler that will reject non-local requests in case the daemon gets bound
// incorrectly to a public interface
type SecurityHandler struct {
handler http.Handler
}
func (h SecurityHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
// String is ip:port formatted
ip := strings.Split(r.RemoteAddr, ":")[0]
if ip != "169.254.169.254" && ip != "127.0.0.1" {
jww.ERROR.Printf("Non-local metadata request from %s!", ip)
http.NotFound(w, r)
return
} else {
h.handler.ServeHTTP(w, r)
}
}
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