feat: sign and verify token func

internal/auth/jwt.go

@@ -0,0 +1,89 @@
+package auth
+
+import (
+	"crypto/ecdsa"
+	"crypto/x509"
+	"encoding/base64"
+	"fmt"
+	"os"
+
+	"github.com/golang-jwt/jwt/v5"
+)
+
+func parseBase64PrivateKey(envVar string) (*ecdsa.PrivateKey, error) {
+    b64 := os.Getenv(envVar)
+    if b64 == "" {
+        return nil, fmt.Errorf("env var %s is empty", envVar)
+    }
+
+    decoded, err := base64.StdEncoding.DecodeString(b64)
+    if err != nil {
+        return nil, fmt.Errorf("failed to decode base64 key: %v", err)
+    }
+
+    return x509.ParseECPrivateKey(decoded)
+}
+
+func parseBase64PublicKey(envVar string) (*ecdsa.PublicKey, error) {
+    b64 := os.Getenv(envVar)
+    if b64 == "" {
+        return nil, fmt.Errorf("env var %s is empty", envVar)
+    }
+
+    decoded, err := base64.StdEncoding.DecodeString(b64)
+    if err != nil {
+        return nil, fmt.Errorf("failed to decode base64 key: %v", err)
+    }
+
+    pubInterface, err := x509.ParsePKIXPublicKey(decoded)
+    if err != nil {
+        return nil, fmt.Errorf("failed to parse public key: %v", err)
+    }
+
+    pubKey, ok := pubInterface.(*ecdsa.PublicKey)
+    if !ok {
+        return nil, fmt.Errorf("not an ECDSA public key")
+    }
+
+    return pubKey, nil
+}
+
+func SignJwtToken(claims jwt.Claims) (string, error) {
+	privateKey, err := parseBase64PrivateKey("JWT_PRIVATE_KEY")
+	if err != nil {
+		return "", err
+	}
+
+	token := jwt.NewWithClaims(jwt.SigningMethodES256, claims)
+	s, err := token.SignedString(privateKey)
+	if err != nil {
+		return "", err
+	}
+
+	return s, nil
+}
+
+func VerifyToken(token string, claims jwt.Claims) (*jwt.Token, error) {
+	publicKey, err := parseBase64PublicKey("JWT_PUBLIC_KEY")
+	if err != nil {
+		return nil, err
+	}
+
+	parsed, err := jwt.ParseWithClaims(token, claims, func(t *jwt.Token) (any, error) {
+		if _, ok := t.Method.(*jwt.SigningMethodECDSA); !ok {
+			return nil, fmt.Errorf("unexpected signing method: %v", t.Header["alg"])
+		}
+		return publicKey, nil
+	})
+
+	if err != nil {
+		return nil, fmt.Errorf("invalid token: %w", err)
+	}
+
+	if !parsed.Valid {
+		return nil, fmt.Errorf("token is not valid")
+	}
+
+	return parsed, nil
+}
+