Teso_API/Teso API/Methods/TokenService.cs

using Microsoft.IdentityModel.Tokens;
using System;
using System.Collections.Generic;
using System.IdentityModel.Tokens.Jwt;
using System.Linq;
using System.Security.Claims;
using System.Security.Cryptography;
using System.Text;
using System.Threading.Tasks;
using Teso_API.Models;

namespace Teso_API.Methods
{
    public class TokenService : ITokenService
    {
        public string GenerateAccessToken(IEnumerable<Claim> claims)
        {
            var secretKey = new SymmetricSecurityKey(Encoding.UTF8.GetBytes(ServerLocation.key));
            var signinCredentials = new SigningCredentials(secretKey, SecurityAlgorithms.HmacSha256);

            var tokeOptions = new JwtSecurityToken(
                issuer: ServerLocation.issuer,
                audience: ServerLocation.issuer,
                claims: claims,
                expires: DateTime.UtcNow.AddDays(14),
                signingCredentials: signinCredentials
            );

            var tokenString = new JwtSecurityTokenHandler().WriteToken(tokeOptions);
            return tokenString;
        }

        public string GenerateRefreshToken()
        {
            var randomNumber = new byte[32];
            using (var rng = RandomNumberGenerator.Create())
            {
                rng.GetBytes(randomNumber);
                return Convert.ToBase64String(randomNumber);
            }
        }

        public ClaimsPrincipal GetPrincipalFromExpiredToken(string token)
        {
            var tokenValidationParameters = new TokenValidationParameters
            {
                ValidateIssuer = true,
                ValidateAudience = true,
                ValidAudience = ServerLocation.audience,
                ValidIssuer = ServerLocation.issuer,
                ValidateIssuerSigningKey = true,
                IssuerSigningKey = new SymmetricSecurityKey(Encoding.UTF8.GetBytes(ServerLocation.key)),
                ValidateLifetime = false //here we are saying that we don't care about the token's expiration date

            };

            var tokenHandler = new JwtSecurityTokenHandler();
            SecurityToken securityToken;
            var principal = tokenHandler.ValidateToken(token, tokenValidationParameters, out securityToken);
            var jwtSecurityToken = securityToken as JwtSecurityToken;
            if (jwtSecurityToken == null || !jwtSecurityToken.Header.Alg.Equals(SecurityAlgorithms.HmacSha256, StringComparison.InvariantCultureIgnoreCase))
                throw new SecurityTokenException("Invalid token");

            return principal;

        }
    }
}