private void ValidateHttp11(Package package)
{
// Is it claiming to be HTTP/1.1? Then it shouldn't do HTTP/1.0 things
// Blocks some common corporate proxy servers in strict mode
if (package.HeadersMixed.ContainsKey("Pragma")
&& package.HeadersMixed["Pragma"].Contains("no-cache")
&& !package.HeadersMixed.ContainsKey("Cache-Control")) {
package.RaiseStrict(Errors.Http11Invalid);
}
}
public RuleProcessing Validate(Package package)
{
if (package.Request.HttpMethod != "POST" && String.IsNullOrEmpty(package.Request.UserAgent))
package.Raise(Errors.UserAgentMissing);
// Broken spambots send URLs with various invalid characters
// Some broken browsers send the #vector in the referer field :(
// Worse yet, some Javascript client-side apps do the same in
// blatant violation of the protocol and good sense.
// if (strpos($package['request_uri'], "#") !== FALSE || strpos($package['headers_mixed']['Referer'], "#") !== FALSE) {
if (package.Request.RawUrl.Contains('#'))
package.RaiseStrict(Errors.Malicious);
// A pretty nasty SQL injection attack on IIS servers
if (package.Request.RawUrl.Contains(";DECLARE%20@"))
package.Raise(Errors.Malicious);
// Range: field exists and begins with 0
// Real user-agents do not start ranges at 0
// NOTE: this blocks the whois.sc bot. No big loss.
// Exceptions: MT (not fixable); LJ (refuses to fix; may be
// blocked again in the future); Facebook
if (package.HeadersMixed.ContainsKey("Range")
&& package.HeadersMixed["Range"].Contains("=0-")) {
if (!(
package.Request.UserAgent.StartsWith("MovableType") ||
package.Request.UserAgent.StartsWith("URI::Fetch") ||
package.Request.UserAgent.StartsWith("php-openid/") ||
package.Request.UserAgent.StartsWith("facebookexternalhit")
)) {
package.RaiseStrict(Errors.RangeHeaderZero);
}
}
// Content-Range is a response header, not a request header
if (package.HeadersMixed.ContainsKey("Content-Range"))
package.Raise(Errors.InvalidRangeHeader);
// Lowercase via is used by open proxies/referrer spammers
// Exceptions: Clearswift uses lowercase via (refuses to fix;
// may be blocked again in the future)
if (package.Request.Headers["via"] != null &&
!package.Request.Headers["via"].Contains("Clearswift") &&
!package.Request.UserAgent.Contains("CoralWebPrx"))
package.Raise(Errors.InvalidVia);
// pinappleproxy is used by referrer spammers
if (package.HeadersMixed.ContainsKey("Via")) {
string via = package.HeadersMixed["Via"].ToLowerInvariant();
if (via.Contains("pinappleproxy") || via.Contains("pcnetserver") || via.Contains("invisiware"))
package.Raise(Errors.BannedProxy);
}
// TE: if present must have Connection: TE
// RFC 2616 14.39
// Blocks Microsoft ISA Server 2004 in strict mode. Contact Microsoft
// to obtain a hotfix.
if (package.HeadersMixed.ContainsKey("Te")) {
if (Regex.Match(package.HeadersMixed["Connection"], @"\bTE\b").Success)
package.RaiseStrict(Errors.TeWithoutConnectionTe);
}
if (package.HeadersMixed.ContainsKey("Connection")) {
// Connection: keep-alive and close are mutually exclusive.
// Keep-Alive shouldn't appear twice, neither should Close.
var connection = package.HeadersMixed.GetValues("Connection");
var keepAlives = connection.Sum
(x => Regex.Matches(x, @"\bKeep-Alive\b", RegexOptions.IgnoreCase).Count);
var closes = connection.Sum
(x => Regex.Matches(x, @"\bClose\b", RegexOptions.IgnoreCase).Count);
if (keepAlives + closes > 1)
package.Raise(Errors.InvalidConnectionHeader);
// Keep-Alive format in RFC 2068; some bots mangle these headers
if (connection.Any(x => x.IndexOf
("Keep-Alive: ", StringComparison.InvariantCultureIgnoreCase) >= 0))
package.Raise(Errors.MaliciousConnectionHeader);
}
// Headers which are not seen from normal user agents; only malicious bots
if (package.HeadersMixed.ContainsKey("X-Aaaaaaaaaaaa") ||
package.HeadersMixed.ContainsKey("X-Aaaaaaaaaa"))
package.Raise(Errors.ProhibitedHeader);
// Proxy-Connection does not exist and should never be seen in the wild
// http://lists.w3.org/Archives/Public/ietf-http-wg-old/1999JanApr/0032.html
// http://lists.w3.org/Archives/Public/ietf-http-wg-old/1999JanApr/0040.html
if (package.HeadersMixed.ContainsKey("Proxy-Connection"))
package.RaiseStrict(Errors.ProxyConnectionHeaderPresent);
if (package.HeadersMixed.ContainsKey("Referer")) {
string referer = package.HeadersMixed["Referer"];
// Referer, if it exists, must not be blank
if (referer == String.Empty)
package.Raise(Errors.BlankReferer);
// Referer, if it exists, must contain a :
// While a relative URL is technically valid in Referer, all known
// legitimate user-agents send an absolute URL
if (!referer.Contains(":"))
package.Raise(Errors.CorruptReferer);
}
return RuleProcessing.Continue;
}