public void Inspect(ResponseAnalysisContext context, CancellationToken cancellationToken)
{
if (context.IsHtml())
{
var body = context.ReadAsString();
if (body != null)
{
foreach (var comment in FastHtmlParser.FindAllComments(body))
{
if (
// respect Knockout.js comments
comment.StartsWith("<!-- ko", StringComparison.Ordinal) ||
comment.StartsWith("<!-- /ko", StringComparison.Ordinal) ||
// respect IE conditional comments
comment.StartsWith("<!--[if ", StringComparison.Ordinal) ||
comment.StartsWith("[endif]-->", StringComparison.Ordinal)
)
{
continue;
}
context.AddChange(TextChange.Remove(body, comment.Offset, comment.Length));
}
}
}
}
public void Inspect(ResponseAnalysisContext context, CancellationToken cancellationToken)
{
if (context.IsHtml())
{
// read content
string html = context.ReadAsString();
if (html == null)
{
return;
}
string csrfTag = null;
// enumerate forms
foreach (var formIndex in FastHtmlParser.FindAllTagIndexes(html, "form"))
{
// check method attribute
var method = FastHtmlParser.GetAttributeValueAtTag(html, "method", formIndex);
if (method.Equals("post", StringComparison.OrdinalIgnoreCase))
{
// generate CSRF hidden field
if (csrfTag == null)
{
var tokens = Antiforgery.GetAndStoreTokens(context.HttpContext);
csrfTag = $"<input type=\"hidden\" name=\"{HtmlEncoder.Default.Encode(tokens.FormFieldName)}\" value=\"{HtmlEncoder.Default.Encode(tokens.RequestToken)}\" />";
}
// insert field
int close = FastHtmlParser.FindClosePairFlatIndex(html, "form", formIndex);
context.AddChange(TextChange.Insert(html, close, csrfTag));
}
}
}
}
private static void InspectBody(ResponseAnalysisContext context)
{
string body = context.ReadAsString();
if (body != null)
{
// rewrite HTML
if (context.IsHtml())
{
foreach (var index in body.AllIndexesOf("http:", StringComparison.OrdinalIgnoreCase))
{
// make sure it is inside an attribute
var attributeName = FastHtmlParser.GetAttributeNameFromValueIndex(body, index);
if (attributeName.Equals("src", StringComparison.OrdinalIgnoreCase) ||
attributeName.Equals("href", StringComparison.OrdinalIgnoreCase) ||
attributeName.Equals("srcset", StringComparison.OrdinalIgnoreCase))
{
context.AddChange(TextChange.Insert(body, index + "http".Length, "s"));
// 'xmlns' excluded
}
}
}
// rewrite CSS
if (context.IsCss())
{
foreach (var index in body.AllIndexesOf("http:", StringComparison.OrdinalIgnoreCase))
{
context.AddChange(TextChange.Insert(body, index + "http".Length, "s"));
}
}
}
}
private static void InspectBody(ResponseAnalysisContext context)
{
var html = context.ReadAsString();
if (html != null)
{
foreach (var index in FastHtmlParser.FindAllTagIndexes(html, "meta"))
{
if (FastHtmlParser.GetAttributeValueAtTag(html, "name", index).Equals("generator", StringComparison.OrdinalIgnoreCase))
{
var end = FastHtmlParser.FindEndOfOpenTag(html, index) + 1;
context.AddChange(TextChange.Remove(html, index, end - index));
}
}
}
}
public async Task InspectAsync(ResponseAnalysisContext context, CancellationToken cancellationToken)
{
if (context.IsHtml())
{
var html = context.ReadAsString();
// find all script tags
foreach (var index in FastHtmlParser.FindAllTagIndexes(html, "script"))
{
// get 'src' attribute
var src = FastHtmlParser.GetAttributeValueAtTag(html, "src", index);
if (src.IndexOf(':') != -1 || src.StartsWith("//", StringComparison.Ordinal))
{
// check whether there is an 'integrity' attribute alrady
var integrity = FastHtmlParser.GetAttributeValueAtTag(html, "integrity", index);
if (integrity.Length > 0)
{
continue;
}
// compute integrity
var sri = await MemoryCache.GetOrCreateAsync($"SRI_{src}", async ce =>
{
ce.SetAbsoluteExpiration(DateTimeOffset.MaxValue);
ce.SetPriority(CacheItemPriority.High);
var client = HttpClientFactory.CreateClient();
try
{
// download script
using var request = new HttpRequestMessage(HttpMethod.Get, RelativeTo(src).ToString());
request.Headers.TryAddWithoutValidation("Origin", $"{context.HttpContext.Request.Scheme}://{context.HttpContext.Request.Host}");
using var response = await client.SendAsync(request);
if (!response.IsSuccessStatusCode)
{
return(null);
}
if (response.Content == null)
{
return(null);
}
if (!response.Headers.Any(h => h.Key.StartsWith("Access-Control-Allow", StringComparison.OrdinalIgnoreCase)))
{
return(null);
}
var stream = await response.Content.ReadAsStreamAsync();
// compute hash
var hash = HashAlgorithmPool.Sha256.ComputeHash(stream);
var base64 = Convert.ToBase64String(hash);
return($"sha256-{base64}");
}
catch (HttpRequestException)
{
return(null);
}
});
// add attribute
if (sri != null)
{
context.AddChange(FastHtmlParser.CreateInsertAttributeChange(html, index, "script", "integrity", sri));
if (FastHtmlParser.GetAttributeValueAtTag(html, "crossorigin", index).Length == 0)
{
context.AddChange(FastHtmlParser.CreateInsertAttributeChange(html, index, "script", "crossorigin", "anonymous"));
}
}
}
}
}
}
