JwtSecurityToken doesn't expire when it should

The problem is related ClockSkew. Normally, the validation libraries (at least the MS one) compensate for clock skew. ClockSkew default value is 5 minutes. See some answer here

You can change ClockSkew in TokenValidationParameters:

var tokenValidationParameters = new TokenValidationParameters
{
    //...your setting

    // set ClockSkew is zero
    ClockSkew = TimeSpan.Zero
};

app.UseJwtBearerAuthentication(new JwtBearerOptions
{
    AutomaticAuthenticate = true,
    AutomaticChallenge = true,
    TokenValidationParameters = tokenValidationParameters
});

Happy coding!

There are seems to be some issue with LifeTimeValidator. You can just override its logic with a custom delegate. Also, use JwtBearerOptions class to control authentication middleware behavior. For example:

new JwtBearerOptions
{
     AutomaticAuthenticate = true,
     AutomaticChallenge = true,
     TokenValidationParameters = new Microsoft.IdentityModel.Tokens.TokenValidationParameters
     {
           ValidIssuer = _configuration["Tokens:Issuer"],
           ValidAudience = _configuration["Tokens:Audience"],
           ValidateIssuer = true,
           ValidateAudience = true,
           ValidateLifetime = true,
           LifetimeValidator = LifetimeValidator,
           ValidateIssuerSigningKey = true,
           IssuerSigningKey = new SymmetricSecurityKey(Encoding.UTF8.GetBytes(_configuration["Tokens:Key"]))
      }
}

And assign LifetimeValidotor delegate, to provide its own timeout validation logic:

private bool LifetimeValidator(DateTime? notBefore, DateTime? expires, SecurityToken token, TokenValidationParameters @params)
{
     if (expires != null)
     {
          return expires > DateTime.UtcNow;
     }
     return false;
}

After reading through @Denis Kucherov's answer, I found out that I could use the same custom validator he posted without using the JwtBearerOptions class which would have required me to add a new library.

Also, Since there are two namespaces which contain a lot of these same classes I will make sure to mention that all of these are using the System.IdentityModels... namespaces. (NOT Microsoft.IdentityModels...)

Below is the code I ended up using:

private bool CustomLifetimeValidator(DateTime? notBefore, DateTime? expires, SecurityToken tokenToValidate, TokenValidationParameters @param)
{
    if (expires != null)
    {
        return expires > DateTime.UtcNow;
    }
    return false;
}
private JwtSecurityToken ValidateJwtToken(string tokenString)
{
   string secret = ConfigurationManager.AppSettings["jwtSecret"].ToString();
   var securityKey = new InMemorySymmetricSecurityKey(Encoding.Default.GetBytes(secret));
   JwtSecurityTokenHandler handler = new JwtSecurityTokenHandler();
   TokenValidationParameters validation = new TokenValidationParameters()
   {
       ValidAudience = "MyAudience",
       ValidIssuer = "MyIssuer",
       ValidateIssuer = true,
       ValidateLifetime = true,
       LifetimeValidator = CustomLifetimeValidator,
       RequireExpirationTime = true,
       IssuerSigningKey = securityKey,
       ValidateIssuerSigningKey = true,
   };
   SecurityToken token;
   ClaimsPrincipal principal = handler.ValidateToken(tokenString, validation, out token);
   return (JwtSecurityToken)token;
}