public static SanitizeResult sanitizer(String html, Regex allowedTags, Regex forbiddenTags, bool isConsiderAllowedTag = false)
{
SanitizeResult ret = new SanitizeResult();
Stack <String> openTags = new Stack <string>();
if (String.IsNullOrEmpty(html))
{
return(ret);
}
List <String> tokens = tokenize(html);
// ------------------- LOOP for every token --------------------------
for (int i = 0; i < tokens.Count; i++)
{
String token = tokens[i];
bool isAcceptedToken = false;
Match startMatcher = tagStartPattern.Match(token);
Match endMatcher = tagClosePattern.Match(token);
//-------------------------------------------------------------------------------- COMMENT <!-- ......... -->
if (commentPattern.Match(token).Success)
{
ret.val = ret.val + token + (token.EndsWith("-->") ? "" : "-->");
ret.invalidTags.Add(token + (token.EndsWith("-->") ? "" : "-->"));
continue;
//-------------------------------------------------------------------------------- OPEN TAG <tag .........>
}
else if (startMatcher.Success)
{
//tag name extraction
String tag = startMatcher.Groups[1].Value.ToLower();
//----------------------------------------------------- FORBIDDEN TAG <script .........>
if (forbiddenTags.Match(tag).Success)
{
ret.invalidTags.Add("<" + tag + ">");
continue;
// -------------------------------------------------- WELL KNOWN TAG
}
else if (allowedTags.Match(tag).Success)
{
if (!isConsiderAllowedTag)
{
ret.invalidTags.Add("<" + tag + ">");
continue;
}
String cleanToken = "<" + tag;
String tokenBody = startMatcher.Groups[2].Value;
//first test table consistency
//table tbody tfoot thead th tr td
if ("thead".Equals(tag) || "tbody".Equals(tag) || "tfoot".Equals(tag) || "tr".Equals(tag))
{
if (openTags.Select(t => t == "table").Count() <= 0)
{
ret.invalidTags.Add("<" + tag + ">");
continue;
}
}
else if ("td".Equals(tag) || "th".Equals(tag))
{
if (openTags.Count(t => t == "tr") <= 0)
{
ret.invalidTags.Add("<" + tag + ">");
continue;
}
}
// then test properties
//Match attributes = attributesPattern.Match(tokenBody);
var attributes = attributesPattern.Matches(tokenBody);
bool foundURL = false; // URL flag
foreach (Match attribute in attributes)
//while (attributes.find())
{
String attr = attribute.Groups[1].Value.ToLower();
String val = attribute.Groups[2].Value;
if (val.Contains("&{"))
{
ret.invalidTags.Add(attr + " " + val);
}
// we will accept href in case of <A>
else if ("a".Equals(tag) && "href".Equals(attr))
{ // <a href="......">
try
{
var url = new Uri(val);
if (url.Scheme == Uri.UriSchemeHttp || url.Scheme == Uri.UriSchemeHttps || url.Scheme == Uri.UriSchemeMailto)
{
foundURL = true;
}
else
{
ret.invalidTags.Add(attr + " " + val);
val = "";
}
}
catch
{
ret.invalidTags.Add(attr + " " + val);
val = "";
}
}
else if ((tag == "img" || tag == "embed") && "src".Equals(attr))
{ // <img src="......">
try
{
var url = new Uri(val);
if (url.Scheme == Uri.UriSchemeHttp || url.Scheme == Uri.UriSchemeHttps)
{
foundURL = true;
}
else
{
ret.invalidTags.Add(attr + " " + val);
val = "";
}
}
catch
{
ret.invalidTags.Add(attr + " " + val);
val = "";
}
}
else if ("href".Equals(attr) || "src".Equals(attr))
{ // <tag src/href="......"> skipped
ret.invalidTags.Add(tag + " " + attr + " " + val);
continue;
}
else if (attr == "width" || attr == "height")
{ // <tag width/height="......">
Regex r = new Regex("\\d+%|\\d+$");
if (!r.Match(val.ToLower()).Success)
{ // test numeric values
ret.invalidTags.Add(tag + " " + attr + " " + val);
continue;
}
}
else if ("style".Equals(attr))
{ // <tag style="......">
// then test properties
var styles = stylePattern.Matches(val);
String cleanStyle = "";
foreach (Match style in styles)
//while (styles.find())
{
String styleName = style.Groups[1].Value.ToLower();
String styleValue = style.Groups[2].Value;
// suppress invalid styles values
if (forbiddenStylePattern.Match(styleValue).Success)
{
ret.invalidTags.Add(tag + " " + attr + " " + styleValue);
continue;
}
// check if valid url
Match urlStyleMatcher = urlStylePattern.Match(styleValue);
if (urlStyleMatcher.Success)
{
try
{
String url = urlStyleMatcher.Groups[1].Value;
var uri = new Uri(url);
if (!(uri.Scheme == Uri.UriSchemeHttp || uri.Scheme == Uri.UriSchemeHttps))
{
ret.invalidTags.Add(tag + " " + attr + " " + styleValue);
continue;
}
}
catch
{
ret.invalidTags.Add(tag + " " + attr + " " + styleValue);
continue;
}
}
cleanStyle = cleanStyle + styleName + ":" + encode(styleValue) + ";";
}
val = cleanStyle;
}
else if (attr.StartsWith("on"))
{ // skip all javascript events
ret.invalidTags.Add(tag + " " + attr + " " + val);
continue;
}
else
{ // by default encode all properies
val = encode(val);
}
cleanToken = cleanToken + " " + attr + "=\"" + val + "\"";
}
cleanToken = cleanToken + ">";
isAcceptedToken = true;
// for <img> and <a>
if ((tag == "a" || tag == "img" || tag == "embed") && !foundURL)
{
isAcceptedToken = false;
cleanToken = "";
}
token = cleanToken;
// push the tag if require closure and it is accepted (otherwise is encoded)
if (isAcceptedToken && !(standAloneTags.Match(tag).Success || selfClosed.Match(tag).Success))
{
openTags.Push(tag);
}
// -------------------------------------------------------------------------------- UNKNOWN TAG
}
else
{
//ret.invalidTags.Add(token);
//ret.val = ret.val + token;
continue;
}
// -------------------------------------------------------------------------------- CLOSE TAG </tag>
}
else if (endMatcher.Success)
{
String tag = endMatcher.Groups[1].Value.ToLower();
//is self closing
if (selfClosed.Match(tag).Success)
{
ret.invalidTags.Add(token);
continue;
}
if (forbiddenTags.Match(tag).Success)
{
ret.invalidTags.Add("/" + tag);
continue;
}
if (!allowedTags.Match(tag).Success)
{
//ret.invalidTags.Add(token);
//ret.val = ret.val + token;
continue;
}
else
{
String cleanToken = "";
// check tag position in the stack
int pos = -1;
bool found = false;
foreach (var item in openTags)
{
pos++;
if (item == tag)
{
found = true;
break;
}
}
// if found on top ok
if (found)
{
for (int k = 0; k <= pos; k++)
{
//pop all elements before tag and close it
String poppedTag = openTags.Pop();
cleanToken = cleanToken + "</" + poppedTag + ">";
isAcceptedToken = true;
}
}
token = cleanToken;
}
}
ret.val = ret.val + token;
if (isAcceptedToken)
{
ret.html = ret.html + token;
//ret.text = ret.text + " ";
}
else
{
String sanToken = htmlEncodeApexesAndTags(token);
ret.html = ret.html + sanToken;
ret.text = ret.text + htmlEncodeApexesAndTags(removeLineFeed(token));
}
}
// must close remaining tags
while (openTags.Count() > 0)
{
//pop all elements before tag and close it
String poppedTag = openTags.Pop();
ret.html = ret.html + "</" + poppedTag + ">";
ret.val = ret.val + "</" + poppedTag + ">";
}
//set boolean value
ret.isValid = ret.invalidTags.Count == 0;
return(ret);
}