179 lines
4 KiB
Go
179 lines
4 KiB
Go
package main
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import (
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"crypto/rand"
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"crypto/sha256"
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"encoding/hex"
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"fmt"
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"html/template"
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"log"
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"net/http"
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"strconv"
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"sync"
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"time"
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)
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const (
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port = 3000
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difficulty = 20
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)
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var (
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challengeStore = make(map[string]time.Time)
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storeMutex sync.Mutex
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)
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func generateChallenge() string {
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b := make([]byte, 12)
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_, err := rand.Read(b)
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if err != nil {
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panic(err)
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}
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return hex.EncodeToString(b)
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}
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func checkDifficulty(hash []byte, bits int) bool {
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i := 0
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for bits > 0 {
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b := hash[i]
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if bits >= 8 {
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if b != 0 {
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return false
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}
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bits -= 8
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} else {
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mask := byte(0xFF << (8 - bits))
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if b&mask != 0 {
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return false
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}
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bits = 0
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}
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i++
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}
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return true
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}
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func indexHandler(w http.ResponseWriter, r *http.Request) {
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challenge := generateChallenge()
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storeMutex.Lock()
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challengeStore[challenge] = time.Now()
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storeMutex.Unlock()
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tmpl.Execute(w, map[string]string{
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"Challenge": challenge,
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"Difficulty": strconv.Itoa(difficulty),
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})
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}
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func postHandler(w http.ResponseWriter, r *http.Request) {
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challenge := r.FormValue("challenge")
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nonce := r.FormValue("nonce")
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storeMutex.Lock()
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_, ok := challengeStore[challenge]
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if ok {
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delete(challengeStore, challenge)
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}
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storeMutex.Unlock()
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if !ok {
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fmt.Fprint(w, "<p>Invalid challenge.</p><a href='/'>Try again</a>")
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return
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}
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hash := sha256.Sum256([]byte(challenge + nonce))
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if checkDifficulty(hash[:], difficulty) {
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fmt.Fprint(w, "<div style='text-align:center;'><h1>Success! Valid nonce.</h1><a href='/'>Try again</a></div>")
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} else {
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fmt.Fprint(w, "<div style='text-align:center;'><p>Invalid nonce.</p><a href='/'>Try again</a></div>")
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}
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}
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var tmpl = template.Must(template.New("page").Parse(`
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<!doctype html>
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<html lang="en">
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<head>
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<title>NOJSCAP demo</title>
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<meta charset="UTF-8">
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<meta name="viewport" content="width=device-width, initial-scale=1.0">
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<style>
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body {
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padding: 20px;
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margin-bottom: 300px;
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background: #cacaca;
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color: black;
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}
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::selection {
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background: #a60000;
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color: white;
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}
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code {
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white-space: break-spaces;
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background: black;
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color: white;
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padding: 10px;
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display: block;
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max-width: 500px;
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}
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.h {
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font-size: 21px;
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font-weight: bolder;
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width: 100%;
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float: left;
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}
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button {
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background: #006ed0;
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color: white;
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border: 1px solid #006ed0;
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padding: 10px 20px;
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margin-top: 10px;
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}
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input {
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background: black;
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color: white;
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padding: 10px;
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display: block;
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max-width: 500px;
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width: 100%;
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border: 0px solid transparent;
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font-family: monospace;
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font-size: 12px;
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}
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</style>
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</head>
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<body>
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<h1>NOJSCAP demo</h1>
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<p><a href="https://git.libroot.org/libroot/NOJSCAP/" target="_blank">https://git.libroot.org/libroot/NOJSCAP/</a></p>
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<p>If you don't already have the <b><em>NOJSCAP</em></b> client:</p>
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<code>$ git clone https://git.libroot.org/libroot/NOJSCAP/$ cd NOJSCAP/client/</code>
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<p><code>$ python3 nojscap.py {{.Challenge}} {{.Difficulty}}</code></p>
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<p><strong>Go:</strong></p>
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<p><code>$ go run nojscap.go {{.Challenge}} {{.Difficulty}}</code></p>
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<p><strong>Node.js:</strong></p>
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<p><code>$ node nojscap.js {{.Challenge}} {{.Difficulty}}</code></p>
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<p><strong>Rust:</strong></p>
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<p><code>$ rustc nojscap.rs -o nojscap_rs$ nojscap_rs {{.Challenge}} {{.Difficulty}}</code></p>
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<p><strong>C:</strong></p>
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<p><code>$ gcc -O2 -o nojscap nojscap.c -lssl -lcrypto$ ./nojscap {{.Challenge}} {{.Difficulty}}</code></p>
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<form method="POST">
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<input type="hidden" name="challenge" value="{{.Challenge}}">
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<label class="h">Nonce: <input name="nonce"></label>
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<button type="submit">Submit</button>
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</form>
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</body>
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</html>
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`))
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func main() {
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http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
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if r.Method == http.MethodPost {
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postHandler(w, r)
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} else {
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indexHandler(w, r)
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}
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})
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fmt.Printf("Running on http://localhost:%d\n", port)
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log.Fatal(http.ListenAndServe(fmt.Sprintf(":%d", port), nil))
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}
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