validate jwt token code example

Example 1: validate jwt token c#

public static Task<IPrincipal> validateToken(string token)
        {
            ClaimsPrincipal principal = getPrincipal(token);
            if (principal == null)
                return null;
            ClaimsIdentity identity = null;
            try
            {
                identity = (ClaimsIdentity)principal.Identity;
                IPrincipal Iprincipal = new ClaimsPrincipal(identity);
                return Task.FromResult(Iprincipal);
            }
            catch (NullReferenceException)
            {
                return Task.FromResult<IPrincipal>(null);
            }
        }

 private static ClaimsPrincipal getPrincipal(string token)
        {
            try
            {
                JwtSecurityTokenHandler tokenHandler = new JwtSecurityTokenHandler();
                JwtSecurityToken jwtToken = (JwtSecurityToken)tokenHandler.ReadToken(token);
                if (jwtToken == null)
                    return null;
                byte[] key = Encoding.ASCII.GetBytes(config.jwtSecret);
                TokenValidationParameters parameters = new TokenValidationParameters()
                {
                    ValidIssuer = config.jwtIssuer,
                    ValidAudience = config.jwtIssuer,
                    ValidateLifetime = true,
                    RequireExpirationTime = true,
                    ValidateIssuer = true,
                    ValidateAudience = true,
                    IssuerSigningKey = new SymmetricSecurityKey(key),
                    ClockSkew = TimeSpan.Zero
                };
                SecurityToken securityToken;
                ClaimsPrincipal principal = tokenHandler.ValidateToken(token,
                      parameters, out securityToken);
                return principal;
            }
            catch
            {
                return null;
            }
  }

Example 2: javascript token generator

function generate_token(length){
    //edit the token allowed characters
    var a = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890".split("");
    var b = [];  
    for (var i=0; i<length; i++) {
        var j = (Math.random() * (a.length-1)).toFixed(0);
        b[i] = a[j];
    }
    return b.join("");
}
generate_token(32); //returns "qweQj4giRJSdMNzB8g1XIa6t3YtRIHPH"

Example 3: decode csrf token online

{
  "alg": "CfDJ8OW5OI0CPGJBgSNlGwO0x4YF7qbYKVv7KOO-N0eFtDUzXOrL7F9Xd9W1otVi4ueJOkAmAhuoHFWNkqRaFD7zvAMHMSKncl6Vo5QXKmpvy6vqxOKxSURdIey8aZPRi3Nnhp2p9la-Al5xrVKz0lignRdcCHf3O7pF9zv_sNx_c_T7pUe3WsxaJEPX3t_9FO2Wjw"
}

Example 4: jwt

JSON Web Token is an Internet standard for creating data with optional
signature and/or optional encryption whose payload holds JSON that asserts
some number of claims.

The tokens are signed either using a private secret or a public/private key.