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package module
import (
"crypto/md5"
"crypto/rand"
"errors"
"io"
"tunnel/pkg/netstring"
"tunnel/pkg/server/env"
"tunnel/pkg/server/opts"
"tunnel/pkg/server/queue"
)
const ChallengeLen = 16
type auth struct {
secret string
challenge struct {
self string
peer string
}
hash string
recvChallenge chan struct{}
recvHash chan struct{}
fail chan struct{}
ok chan struct{}
}
var errDupChallenge = errors.New("peer duplicates challenge")
var errAuthFail = errors.New("peer auth fail")
type authModule struct{}
func (a *auth) generateChallenge() error {
b := make([]byte, ChallengeLen)
if _, err := rand.Read(b); err != nil {
return err
}
a.challenge.self = string(b)
return nil
}
func (a *auth) getHash(c string) string {
h := md5.New()
io.WriteString(h, a.secret)
io.WriteString(h, c)
return string(h.Sum(nil))
}
func (a *auth) isReady(c chan struct{}) bool {
select {
case <-a.fail:
return false
case <-c:
return true
}
}
func (a *auth) Send(rq, wq queue.Q) error {
e := netstring.NewEncoder(wq.Writer())
if err := a.generateChallenge(); err != nil {
return err
}
e.Encode(a.challenge.self)
if !a.isReady(a.recvChallenge) {
return nil
}
if a.challenge.self == a.challenge.peer {
return errDupChallenge
}
e.Encode(a.getHash(a.challenge.peer))
if !a.isReady(a.recvHash) {
return nil
}
if a.hash != a.getHash(a.challenge.self) {
close(a.fail)
return errAuthFail
}
close(a.ok)
return queue.Copy(rq, wq)
}
func (a *auth) Recv(rq, wq queue.Q) (err error) {
r := rq.Reader()
d := netstring.NewDecoder(r)
if a.challenge.peer, err = d.Decode(); err != nil {
close(a.fail)
return
}
close(a.recvChallenge)
if a.hash, err = d.Decode(); err != nil {
close(a.fail)
return err
}
close(a.recvHash)
if !a.isReady(a.ok) {
return nil
}
return queue.IoCopy(r, wq.Writer())
}
func getAuthSecret(env env.Env) string {
if v := env.Eval("@{tunnel.@{tunnel}.secret}"); v != "" {
return v
}
return env.Get("secret")
}
func (m authModule) Open(env env.Env) (interface{}, error) {
a := &auth{
secret: getAuthSecret(env),
recvChallenge: make(chan struct{}),
recvHash: make(chan struct{}),
fail: make(chan struct{}),
ok: make(chan struct{}),
}
return a, nil
}
func init() {
register("auth", func(opts.Opts, env.Env) (module, error) {
return authModule{}, nil
})
}
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