server/src/Core/IdentityServer/TokenRetrieval.cs

using Microsoft.AspNetCore.Http;

namespace Bit.Core.IdentityServer
{
    public static class TokenRetrieval
    {
        private static string _headerScheme = "Bearer ";
        private static string _queuryScheme = "access_token";
        private static string _authHeader = "Authorization";

        public static Func<HttpRequest, string> FromAuthorizationHeaderOrQueryString()
        {
            return (request) =>
            {
                var authorization = request.Headers[_authHeader].FirstOrDefault();
                if (string.IsNullOrWhiteSpace(authorization))
                {
                    return request.Query[_queuryScheme].FirstOrDefault();
                }

                if (authorization.StartsWith(_headerScheme, StringComparison.OrdinalIgnoreCase))
                {
                    return authorization.Substring(_headerScheme.Length).Trim();
                }

                return null;
            };
        }
    }
}