/
60.go
82 lines (71 loc) · 2.11 KB
/
60.go
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package main
import (
"bytes"
"crypto/rand"
"crypto/rsa"
"crypto/sha1"
"encoding/gob"
"fmt"
"log"
. "net"
)
var HELLO_WORLD = []byte("Hello World")
var RSA_LABEL = []byte("served")
type LaunchError []interface{}
func (l LaunchError) Error() (r string) {
if len(l) > 0 {
r = fmt.Sprintf(l[0].(string), l[1:]...)
}
return
}
func NewLaunchError(format string, v ...interface{}) (l LaunchError) {
return LaunchError(append([]interface{}{ format }, v))
}
func main() {
Serve(":1025", func(connection *UDPConn, c *UDPAddr, packet *bytes.Buffer) (n int) {
var key rsa.PublicKey
var response []byte
if e := gob.NewDecoder(packet).Decode(&key); e != nil {
log.Println("unable to decode wrapper:", c)
} else if response, e = rsa.EncryptOAEP(sha1.New(), rand.Reader, &key, HELLO_WORLD, RSA_LABEL); e != nil {
log.Println("unable to encrypt server response")
} else if n, e = connection.WriteToUDP(response, c); e != nil {
log.Println("unable to write response to client:", c)
}
return
})
}
func Serve(address string, f func(*UDPConn, *UDPAddr, *bytes.Buffer) int) {
e := Launch(address, func(connection *UDPConn) (e error) {
defer func() {
if x := recover(); x != nil {
e = LaunchError{ "serve failure %v", x }
}
}()
for {
buffer := make([]byte, 1024)
if n, client, e := connection.ReadFromUDP(buffer); e == nil {
go func(c *UDPAddr, b []byte) {
if n := f(connection, c, bytes.NewBuffer(b)); n != 0 {
log.Println(n, "bytes written to", c)
}
}(client, buffer[:n])
} else {
log.Println(address, e.Error())
}
}
return
})
if e, ok:= e.(LaunchError); ok {
log.Fatalln(e.Error())
}
}
func Launch(address string, f func(*UDPConn) error) error {
var connection *UDPConn
if a, e := ResolveUDPAddr("udp", address); e != nil {
return NewLaunchError("unable to resolve UDP address:", e.Error())
} else if connection, e = ListenUDP("udp", a); e != nil {
return LaunchError{ "can't open socket for listening:", e.Error() }
}
return f(connection)
}