The Tor Browser: browser/components/feeds/src/nsFeedSniffer.cpp@8bccb770b82d (annotated)

browser/components/feeds/src/nsFeedSniffer.cpp@8bccb770b82d (annotated)

browser/components/feeds/src/nsFeedSniffer.cpp

Wed, 31 Dec 2014 13:27:57 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Wed, 31 Dec 2014 13:27:57 +0100
branch: TOR_BUG_3246
changeset 6: 8bccb770b82d
permissions: -rw-r--r--

Ignore runtime configuration files generated during quality assurance.

 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
 /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 #include "nsFeedSniffer.h"
 #include "nsNetCID.h"
 #include "nsXPCOM.h"
 #include "nsCOMPtr.h"
 #include "nsStringStream.h"
 #include "nsBrowserCompsCID.h"
 #include "nsICategoryManager.h"
 #include "nsIServiceManager.h"
 #include "nsComponentManagerUtils.h"
 #include "nsServiceManagerUtils.h"
 #include "nsIStreamConverterService.h"
 #include "nsIStreamConverter.h"
 #include "nsIStreamListener.h"
 #include "nsIHttpChannel.h"
 #include "nsIMIMEHeaderParam.h"
 #include "nsMimeTypes.h"
 #include "nsIURI.h"
 #include <algorithm>
 #define TYPE_ATOM "application/atom+xml"
 #define TYPE_RSS "application/rss+xml"
 #define TYPE_MAYBE_FEED "application/vnd.mozilla.maybe.feed"
 #define NS_RDF "http://www.w3.org/1999/02/22-rdf-syntax-ns#"
 #define NS_RSS "http://purl.org/rss/1.0/"
 #define MAX_BYTES 512u
 NS_IMPL_ISUPPORTS(nsFeedSniffer,
                   nsIContentSniffer,
                   nsIStreamListener,
                   nsIRequestObserver)
 nsresult
 nsFeedSniffer::ConvertEncodedData(nsIRequest* request,
                                   const uint8_t* data,
                                   uint32_t length)
 {
   nsresult rv = NS_OK;
  mDecodedData = "";
  nsCOMPtr<nsIHttpChannel> httpChannel(do_QueryInterface(request));
   if (!httpChannel)
     return NS_ERROR_NO_INTERFACE;
   nsAutoCString contentEncoding;
   httpChannel->GetResponseHeader(NS_LITERAL_CSTRING("Content-Encoding"),
                                  contentEncoding);
   if (!contentEncoding.IsEmpty()) {
     nsCOMPtr<nsIStreamConverterService> converterService(do_GetService(NS_STREAMCONVERTERSERVICE_CONTRACTID));
     if (converterService) {
       ToLowerCase(contentEncoding);
       nsCOMPtr<nsIStreamListener> converter;
       rv = converterService->AsyncConvertData(contentEncoding.get(),
                                               "uncompressed", this, nullptr,
                                               getter_AddRefs(converter));
       NS_ENSURE_SUCCESS(rv, rv);
       converter->OnStartRequest(request, nullptr);
       nsCOMPtr<nsIStringInputStream> rawStream =
         do_CreateInstance(NS_STRINGINPUTSTREAM_CONTRACTID);
       if (!rawStream)
         return NS_ERROR_FAILURE;
       rv = rawStream->SetData((const char*)data, length);
       NS_ENSURE_SUCCESS(rv, rv);
       rv = converter->OnDataAvailable(request, nullptr, rawStream, 0, length);
       NS_ENSURE_SUCCESS(rv, rv);
       converter->OnStopRequest(request, nullptr, NS_OK);
     }
   }
   return rv;
 }
 template<int N>
 static bool
 StringBeginsWithLowercaseLiteral(nsAString& aString,
                                  const char (&aSubstring)[N])
 {
   return StringHead(aString, N).LowerCaseEqualsLiteral(aSubstring);
 }
 bool
 HasAttachmentDisposition(nsIHttpChannel* httpChannel)
 {
   if (!httpChannel)
     return false;
   uint32_t disp;
   nsresult rv = httpChannel->GetContentDisposition(&disp);
   if (NS_SUCCEEDED(rv) && disp == nsIChannel::DISPOSITION_ATTACHMENT)
     return true;
   return false;
 }
 /**
  * @return the first occurrence of a character within a string buffer,
  *         or nullptr if not found
  */
 static const char*
 FindChar(char c, const char *begin, const char *end)
 {
   for (; begin < end; ++begin) {
     if (*begin == c)
       return begin;
   }
   return nullptr;
 }
 /**
  *
  * Determine if a substring is the "documentElement" in the document.
  *
  * All of our sniffed substrings: <rss, <feed, <rdf:RDF must be the "document"
  * element within the XML DOM, i.e. the root container element. Otherwise,
  * it's possible that someone embedded one of these tags inside a document of
  * another type, e.g. a HTML document, and we don't want to show the preview
  * page if the document isn't actually a feed.
  *
  * @param   start
  *          The beginning of the data being sniffed
  * @param   end
  *          The end of the data being sniffed, right before the substring that
  *          was found.
  * @returns true if the found substring is the documentElement, false
  *          otherwise.
  */
 static bool
 IsDocumentElement(const char *start, const char* end)
 {
   // For every tag in the buffer, check to see if it's a PI, Doctype or
   // comment, our desired substring or something invalid.
   while ( (start = FindChar('<', start, end)) ) {
     ++start;
     if (start >= end)
       return false;
     // Check to see if the character following the '<' is either '?' or '!'
     // (processing instruction or doctype or comment)... these are valid nodes
     // to have in the prologue.
     if (*start != '?' && *start != '!')
       return false;
     // Now advance the iterator until the '>' (We do this because we don't want
     // to sniff indicator substrings that are embedded within other nodes, e.g.
     // comments: <!-- <rdf:RDF .. > -->
     start = FindChar('>', start, end);
     if (!start)
       return false;
     ++start;
   }
   return true;
 }
 /**
  * Determines whether or not a string exists as the root element in an XML data
  * string buffer.
  * @param   dataString
  *          The data being sniffed
  * @param   substring
  *          The substring being tested for existence and root-ness.
  * @returns true if the substring exists and is the documentElement, false
  *          otherwise.
  */
 static bool
 ContainsTopLevelSubstring(nsACString& dataString, const char *substring)
 {
   int32_t offset = dataString.Find(substring);
   if (offset == -1)
     return false;
   const char *begin = dataString.BeginReading();
   // Only do the validation when we find the substring.
   return IsDocumentElement(begin, begin + offset);
 }
 NS_IMETHODIMP
 nsFeedSniffer::GetMIMETypeFromContent(nsIRequest* request,
                                       const uint8_t* data,
                                       uint32_t length,
                                       nsACString& sniffedType)
 {
   nsCOMPtr<nsIHttpChannel> channel(do_QueryInterface(request));
   if (!channel)
     return NS_ERROR_NO_INTERFACE;
   // Check that this is a GET request, since you can't subscribe to a POST...
   nsAutoCString method;
   channel->GetRequestMethod(method);
   if (!method.Equals("GET")) {
     sniffedType.Truncate();
     return NS_OK;
   }
   // We need to find out if this is a load of a view-source document. In this
   // case we do not want to override the content type, since the source display
   // does not need to be converted from feed format to XUL. More importantly,
   // we don't want to change the content type from something
   // nsContentDLF::CreateInstance knows about (e.g. application/xml, text/html
   // etc) to something that only the application fe knows about (maybe.feed)
   // thus deactivating syntax highlighting.
   nsCOMPtr<nsIURI> originalURI;
   channel->GetOriginalURI(getter_AddRefs(originalURI));
   nsAutoCString scheme;
   originalURI->GetScheme(scheme);
   if (scheme.EqualsLiteral("view-source")) {
     sniffedType.Truncate();
     return NS_OK;
   }
   // Check the Content-Type to see if it is set correctly. If it is set to
   // something specific that we think is a reliable indication of a feed, don't
   // bother sniffing since we assume the site maintainer knows what they're
   // doing.
   nsAutoCString contentType;
   channel->GetContentType(contentType);
   bool noSniff = contentType.EqualsLiteral(TYPE_RSS) ||
                    contentType.EqualsLiteral(TYPE_ATOM);
   // Check to see if this was a feed request from the location bar or from
   // the feed: protocol. This is also a reliable indication.
   // The value of the header doesn't matter.
   if (!noSniff) {
     nsAutoCString sniffHeader;
     nsresult foundHeader =
       channel->GetRequestHeader(NS_LITERAL_CSTRING("X-Moz-Is-Feed"),
                                 sniffHeader);
     noSniff = NS_SUCCEEDED(foundHeader);
   }
   if (noSniff) {
     // check for an attachment after we have a likely feed.
     if(HasAttachmentDisposition(channel)) {
       sniffedType.Truncate();
       return NS_OK;
     }
     // set the feed header as a response header, since we have good metadata
     // telling us that the feed is supposed to be RSS or Atom
     channel->SetResponseHeader(NS_LITERAL_CSTRING("X-Moz-Is-Feed"),
                                NS_LITERAL_CSTRING("1"), false);
     sniffedType.AssignLiteral(TYPE_MAYBE_FEED);
     return NS_OK;
   }
   // Don't sniff arbitrary types.  Limit sniffing to situations that
   // we think can reasonably arise.
   if (!contentType.EqualsLiteral(TEXT_HTML) &&
       !contentType.EqualsLiteral(APPLICATION_OCTET_STREAM) &&
       // Same criterion as XMLHttpRequest.  Should we be checking for "+xml"
       // and check for text/xml and application/xml by hand instead?
       contentType.Find("xml") == -1) {
     sniffedType.Truncate();
     return NS_OK;
   }
   // Now we need to potentially decompress data served with
   // Content-Encoding: gzip
   nsresult rv = ConvertEncodedData(request, data, length);
   if (NS_FAILED(rv))
     return rv;
   // We cap the number of bytes to scan at MAX_BYTES to prevent picking up
   // false positives by accidentally reading document content, e.g. a "how to
   // make a feed" page.
   const char* testData;
   if (mDecodedData.IsEmpty()) {
     testData = (const char*)data;
     length = std::min(length, MAX_BYTES);
   } else {
     testData = mDecodedData.get();
     length = std::min(mDecodedData.Length(), MAX_BYTES);
   }
   // The strategy here is based on that described in:
   // http://blogs.msdn.com/rssteam/articles/PublishersGuide.aspx
   // for interoperarbility purposes.
   // Thus begins the actual sniffing.
   nsDependentCSubstring dataString((const char*)testData, length);
   bool isFeed = false;
   // RSS 0.91/0.92/2.0
   isFeed = ContainsTopLevelSubstring(dataString, "<rss");
   // Atom 1.0
   if (!isFeed)
     isFeed = ContainsTopLevelSubstring(dataString, "<feed");
   // RSS 1.0
   if (!isFeed) {
     isFeed = ContainsTopLevelSubstring(dataString, "<rdf:RDF") &&
       dataString.Find(NS_RDF) != -1 &&
       dataString.Find(NS_RSS) != -1;
   }
   // If we sniffed a feed, coerce our internal type
   if (isFeed && !HasAttachmentDisposition(channel))
     sniffedType.AssignLiteral(TYPE_MAYBE_FEED);
   else
     sniffedType.Truncate();
   return NS_OK;
 }
 NS_IMETHODIMP
 nsFeedSniffer::OnStartRequest(nsIRequest* request, nsISupports* context)
 {
   return NS_OK;
 }
 NS_METHOD
 nsFeedSniffer::AppendSegmentToString(nsIInputStream* inputStream,
                                      void* closure,
                                      const char* rawSegment,
                                      uint32_t toOffset,
                                      uint32_t count,
                                      uint32_t* writeCount)
 {
   nsCString* decodedData = static_cast<nsCString*>(closure);
   decodedData->Append(rawSegment, count);
   *writeCount = count;
   return NS_OK;
 }
 NS_IMETHODIMP
 nsFeedSniffer::OnDataAvailable(nsIRequest* request, nsISupports* context,
                                nsIInputStream* stream, uint64_t offset,
                                uint32_t count)
 {
   uint32_t read;
   return stream->ReadSegments(AppendSegmentToString, &mDecodedData, count,
                               &read);
 }
 NS_IMETHODIMP
 nsFeedSniffer::OnStopRequest(nsIRequest* request, nsISupports* context,
                              nsresult status)
 {
   return NS_OK;
 }

The Tor Browser / annotate

browser/components/feeds/src/nsFeedSniffer.cpp@8bccb770b82d (annotated)

browser/components/feeds/src/nsFeedSniffer.cpp