Create token module for JWT handling

Author: PythonHacker24

internal/token/token.go

@@ -0,0 +1,83 @@
+package token
+
+import (
+	"fmt"
+	"net/http"
+	"strings"
+	"time"
+
+	"github.com/golang-jwt/jwt/v5"
+
+	"github.com/PythonHacker24/linux-acl-management-backend/config"
+)
+
+/* generating jwt token for user identification with specified configs */
+func GenerateJWT(username string) (string, error) {
+	expiryHours := config.BackendConfig.BackendSecurity.JWTExpiry
+
+	/* generate JWT token with claims */
+	token := jwt.NewWithClaims(jwt.SigningMethodHS256, jwt.MapClaims{
+		"username": username,
+		"exp":      time.Now().Add(time.Hour * time.Duration(expiryHours)).Unix(),
+	})
+
+	return token.SignedString([]byte(config.BackendConfig.BackendSecurity.JWTTokenSecret))
+}
+
+/* validate JWT token and return claims */
+func ValidateJWT(tokenString string) (jwt.MapClaims, error) {
+	/* parse the token */
+	token, err := jwt.Parse(tokenString, func(token *jwt.Token) (interface{}, error) {
+		if _, ok := token.Method.(*jwt.SigningMethodHMAC); !ok {
+			return nil, fmt.Errorf("unexpected signing method")
+		}
+		return []byte(config.BackendConfig.BackendSecurity.JWTTokenSecret), nil
+	})
+
+	/* check if token is valid */
+	if err != nil {
+		return nil, fmt.Errorf("JWT parsing error: %w", err)
+	}
+
+	/* check if token is valid */
+	if claims, ok := token.Claims.(jwt.MapClaims); ok && token.Valid {
+		return claims, nil
+	}
+
+	return nil, fmt.Errorf("invalid token")
+}
+
+/* extracts username from JWT token */
+func GetUsernameFromJWT(tokenString string) (string, error) {
+	/* get claims from JWT Token */
+	claims, err := ValidateJWT(tokenString)
+	if err != nil {
+		return "", fmt.Errorf("JWT validation error: %w", err)
+	}
+
+	/* extract username from JWT Token */
+	username, ok := claims["username"].(string)
+	if !ok {
+		return "", fmt.Errorf("username not found in token")
+	}
+
+	return username, nil
+}
+
+/* extract username from http request (wrapper around GetUsernameFromJWT for http requests) */
+func ExtractUsernameFromRequest(r *http.Request) (string, error) {
+	/* get the authorization header */
+	authHeader := r.Header.Get("Authorization")
+	if authHeader == "" {
+		return "", fmt.Errorf("authorization header not found")
+	}
+
+	/* check if the header is in the correct format */
+	parts := strings.Split(authHeader, " ")
+	if len(parts) != 2 || parts[0] != "Bearer" {
+		return "", fmt.Errorf("invalid authorization header format")
+	}
+
+	/* extract username from JWT token */
+	return GetUsernameFromJWT(parts[1])
+}