public static IApplicationBuilder UseCrossOrigin(this IApplicationBuilder builder, string rootPath)
{
//
// Allow CORs for rootPath only
if (!string.IsNullOrEmpty(rootPath) || rootPath != "/")
{
builder.Use(async(context, next) => {
bool isCorsPreflight = context.Request.Method.Equals("OPTIONS", StringComparison.OrdinalIgnoreCase) &&
context.Request.Headers[HeaderNames.Origin].Any();
if (isCorsPreflight && !context.Request.Path.StartsWithSegments(rootPath))
{
context.Response.StatusCode = (int)HttpStatusCode.NoContent;
}
else
{
await next.Invoke();
}
});
}
//
// Setup
var config = builder.ApplicationServices.GetRequiredService <IConfiguration>();
var corsConfiguration = new CorsConfiguration(config);
builder.UseCors(cBuilder => {
cBuilder.AllowAnyHeader();
cBuilder.WithExposedHeaders(HeaderNames.Total_Count,
Net.Http.Headers.HeaderNames.Location,
Net.Http.Headers.HeaderNames.Allow,
Net.Http.Headers.HeaderNames.WWWAuthenticate);
cBuilder.WithMethods("GET", "HEAD", "POST", "PUT", "PATCH", "DELETE", "OPTIONS", "DEBUG");
cBuilder.AllowCredentials();
IEnumerable <string> allowedOrigins = GetAllowedOrigins(corsConfiguration);
if (allowedOrigins.Any(o => o.Equals("*")))
{
cBuilder.AllowAnyOrigin();
}
else
{
cBuilder.WithOrigins(allowedOrigins.ToArray());
}
});
// We must allow OPTIONS to enter the application without integrated host authentication
// We do not want OPTIONS methods to ever pass cors middleware
builder.Use(async(context, next) => {
if (!context.Request.Method.Equals("OPTIONS", StringComparison.OrdinalIgnoreCase))
{
await next.Invoke();
}
});
return(builder);
}
private static IEnumerable <string> GetAllowedOrigins(CorsConfiguration config)
{
return(config.Rules.Where(r => r.Allow).Select(r => r.Origin));
}