Rate Limiting

Apply rate limiting to upload endpoints to prevent abuse. Limit the number of uploads per user per time window using session-based tracking in the upload handler.

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<%-- Upload handler with session-based rate limiting --%>
public class UploadHandler : IHttpHandler, IRequiresSessionState
{
    private const int MaxUploadsPerMinute = 10;

    public void ProcessRequest(HttpContext context)
    {
        // Track uploads per session
        var key = "UploadCount";
        var timestampKey = "UploadWindowStart";

        DateTime windowStart = context.Session[timestampKey]
            as DateTime? ?? DateTime.MinValue;
        int count = context.Session[key] as int? ?? 0;

        // Reset window if expired
        if ((DateTime.UtcNow - windowStart).TotalMinutes >= 1)
        {
            count = 0;
            windowStart = DateTime.UtcNow;
            context.Session[timestampKey] = windowStart;
        }

        if (count >= MaxUploadsPerMinute)
        {
            context.Response.StatusCode = 429;
            context.Response.Write(
                "Too many uploads. Please try again later.");
            return;
        }

        // Process upload
        HttpPostedFile file = context.Request.Files[0];
        file.SaveAs(Path.Combine(uploadDir, file.FileName));

        context.Session[key] = count + 1;
        context.Response.Write(
            "{\"fileName\":\"" + file.FileName + "\"}");
    }
}

<%-- web.config: configure rate limit settings --%>
<appSettings>
    <add key="UploadRateLimit" value="10" />
    <add key="UploadRateWindowSeconds" value="60" />
</appSettings>

<%-- Client-side: handle 429 status --%>
<script>
AjaxUploader.create(el, {
    uploadUrl: '/ajaxupload.axd/upload',
    onError: function (file, error) {
        if (error.status === 429) {
            alert('Upload limit reached. Please wait.');
        }
    }
});
</script>