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@aln787
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Last active August 29, 2015 14:15
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package main
// using asymmetric crypto/RSA keys
import (
"fmt"
"io/ioutil"
"log"
"net/http"
"time"
jwt "github.com/dgrijalva/jwt-go"
)
// location of the files used for signing and verification
const (
privKeyPath = "keys/app.rsa" // openssl genrsa -out app.rsa keysize
pubKeyPath = "keys/app.rsa.pub" // openssl rsa -in app.rsa -pubout > app.rsa.pub
)
// keys are held in global variables
// i havn't seen a memory corruption/info leakage in go yet
// but maybe it's a better idea, just to store the public key in ram?
// and load the signKey on every signing request? depends on your usage i guess
var (
verifyKey, signKey []byte
)
// read the key files before starting http handlers
func init() {
var err error
signKey, err = ioutil.ReadFile(privKeyPath)
if err != nil {
log.Fatal("Error reading private key")
return
}
verifyKey, err = ioutil.ReadFile(pubKeyPath)
if err != nil {
log.Fatal("Error reading private key")
return
}
}
// just some html, to lazy for http.FileServer()
const (
tokenName = "AccessToken"
landingHtml = `<h2>Welcome to the JWT Test</h2>
<a href="/restricted">fun area</a>
<form action="/authenticate" method="POST">
<input type="text" name="user">
<input type="password" name="pass">
<input type="submit">
</form>`
successHtml = `<h2>Token Set - have fun!</h2><p>Go <a href="/">Back...</a></p>`
restrictedHtml = `<h1>Welcome!!</h1><img src="https://httpcats.herokuapp.com/200" alt="" />`
)
// serves the form and restricted link
func landingHandler(w http.ResponseWriter, r *http.Request) {
w.Header().Set("Content-Type", "text/html")
w.WriteHeader(http.StatusOK)
fmt.Fprint(w, landingHtml)
}
// reads the form values, checks them and creates the token
func authHandler(w http.ResponseWriter, r *http.Request) {
// make sure its post
if r.Method != "POST" {
w.WriteHeader(http.StatusBadRequest)
fmt.Fprintln(w, "No POST", r.Method)
return
}
user := r.FormValue("user")
pass := r.FormValue("pass")
log.Printf("Authenticate: user[%s] pass[%s]\n", user, pass)
// check values
if user != "test" || pass != "known" {
w.WriteHeader(http.StatusForbidden)
fmt.Fprintln(w, "Wrong info")
return
}
// create a signer for rsa 256
t := jwt.New(jwt.GetSigningMethod("RS256"))
// set our claims
t.Claims["AccessToken"] = "level1"
t.Claims["CustomUserInfo"] = struct {
Name string
Kind string
}{user, "human"}
// set the expire time
// see http://tools.ietf.org/html/draft-ietf-oauth-json-web-token-20#section-4.1.4
t.Claims["exp"] = time.Now().Add(time.Minute * 1).Unix()
tokenString, err := t.SignedString(signKey)
if err != nil {
w.WriteHeader(http.StatusInternalServerError)
fmt.Fprintln(w, "Sorry, error while Signing Token!")
log.Printf("Token Signing error: %v\n", err)
return
}
// i know using cookies to store the token isn't really helpfull for cross domain api usage
// but it's just an example and i did not want to involve javascript
http.SetCookie(w, &http.Cookie{
Name: tokenName,
Value: tokenString,
Path: "/",
RawExpires: "0",
})
w.Header().Set("Content-Type", "text/html")
w.WriteHeader(http.StatusOK)
fmt.Fprintln(w, successHtml)
}
// only accessible with a valid token
func restrictedHandler(w http.ResponseWriter, r *http.Request) {
// check if we have a cookie with out tokenName
tokenCookie, err := r.Cookie(tokenName)
switch {
case err == http.ErrNoCookie:
w.WriteHeader(http.StatusUnauthorized)
fmt.Fprintln(w, "No Token, no fun!")
return
case err != nil:
w.WriteHeader(http.StatusInternalServerError)
fmt.Fprintln(w, "Error while Parsing cookie!")
log.Printf("Cookie parse error: %v\n", err)
return
}
// just for the lulz, check if it is empty.. should fail on Parse anyway..
if tokenCookie.Value == "" {
w.WriteHeader(http.StatusUnauthorized)
fmt.Fprintln(w, "No Token, no fun!")
return
}
// validate the token
token, err := jwt.Parse(tokenCookie.Value, func(token *jwt.Token) (interface{}, error) {
// since we only use the one private key to sign the tokens,
// we also only use its public counter part to verify
return verifyKey, nil
})
// branch out into the possible error from signing
switch err.(type) {
case nil: // no error
if !token.Valid { // but may still be invalid
w.WriteHeader(http.StatusUnauthorized)
fmt.Fprintln(w, "WHAT? Invalid Token? F*** off!")
return
}
// see stdout and watch for the CustomUserInfo, nicely unmarshalled
log.Printf("Someone accessed resricted area! Token:%+v\n", token)
w.Header().Set("Content-Type", "text/html")
w.WriteHeader(http.StatusOK)
fmt.Fprintln(w, restrictedHtml)
case *jwt.ValidationError: // something was wrong during the validation
vErr := err.(*jwt.ValidationError)
switch vErr.Errors {
case jwt.ValidationErrorExpired:
w.WriteHeader(http.StatusUnauthorized)
fmt.Fprintln(w, "Token Expired, get a new one.")
return
default:
w.WriteHeader(http.StatusInternalServerError)
fmt.Fprintln(w, "Error while Parsing Token!")
log.Printf("ValidationError error: %+v\n", vErr.Errors)
return
}
default: // something else went wrong
w.WriteHeader(http.StatusInternalServerError)
fmt.Fprintln(w, "Error while Parsing Token!")
log.Printf("Token parse error: %v\n", err)
return
}
}
// setup the handlers and start listening to requests
func main() {
http.HandleFunc("/", landingHandler)
http.HandleFunc("/authenticate", authHandler)
http.HandleFunc("/restricted", restrictedHandler)
log.Println("Listening...")
http.ListenAndServe(":8080", nil)
}
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