From 972e41e92d756a337846132d053d5bb3fa4cf25e Mon Sep 17 00:00:00 2001
From: "cheetah.cat" <git@cheetah.cat>
Date: Wed, 21 Aug 2024 18:40:55 +0200
Subject: [PATCH] added tokenmanager

---
 client/tokenmanager.go | 89 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 89 insertions(+)
 create mode 100644 client/tokenmanager.go

diff --git a/client/tokenmanager.go b/client/tokenmanager.go
new file mode 100644
index 0000000..d724836
--- /dev/null
+++ b/client/tokenmanager.go
@@ -0,0 +1,89 @@
+package client
+
+import (
+	"crypto"
+	"crypto/rand"
+	"crypto/rsa"
+	"crypto/sha256"
+	"crypto/x509"
+	"encoding/base64"
+	"encoding/json"
+	"encoding/pem"
+	"errors"
+	"fmt"
+	"time"
+)
+
+const tokenExpirationSeconds = 60
+
+type TokenManager struct {
+	issuer     string
+	privateKey string
+}
+
+func (t *TokenManager) CreateJwt() (string, error) {
+	if t.issuer == "" || t.privateKey == "" {
+		return "", errors.New("missing required field issuer or private key")
+	}
+
+	key, err := t.getRsaPrivateKey()
+	if err != nil {
+		return "", err
+	}
+
+	var header = struct {
+		Algorithm string `json:"alg"`
+		Type      string `json:"typ"`
+	}{
+		"RS256",
+		"JWT",
+	}
+	var payload = struct {
+		Issuer     string `json:"iss"`
+		Expiration int64  `json:"exp"`
+	}{
+		t.issuer,
+		time.Now().Unix() + tokenExpirationSeconds,
+	}
+
+	headerJson, _ := json.Marshal(&header)
+	payloadJson, _ := json.Marshal(&payload)
+	pkg := base64.RawURLEncoding.EncodeToString(headerJson) + "." + base64.RawURLEncoding.EncodeToString(payloadJson)
+
+	if signature, err := t.sign([]byte(pkg), key); err != nil {
+		return "", err
+	} else {
+		return pkg + "." + base64.RawURLEncoding.EncodeToString(signature), nil
+	}
+}
+
+func (t *TokenManager) sign(data []byte, privateKey *rsa.PrivateKey) ([]byte, error) {
+	h := sha256.New()
+	h.Write(data)
+	d := h.Sum(nil)
+	return rsa.SignPKCS1v15(rand.Reader, privateKey, crypto.SHA256, d)
+}
+
+func (t *TokenManager) getRsaPrivateKey() (*rsa.PrivateKey, error) {
+	block, _ := pem.Decode([]byte(t.privateKey))
+	if block == nil {
+		return nil, errors.New("invalid private key format")
+	}
+
+	switch block.Type {
+	case "PRIVATE KEY":
+		key, err := x509.ParsePKCS8PrivateKey(block.Bytes)
+		if err != nil {
+			return nil, err
+		}
+		return key.(*rsa.PrivateKey), nil
+	case "RSA PRIVATE KEY":
+		key, err := x509.ParsePKCS1PrivateKey(block.Bytes)
+		if err != nil {
+			return nil, err
+		}
+		return key, nil
+	default:
+		return nil, fmt.Errorf("unsupported key type %q", block.Type)
+	}
+}