The Tor Browser / file revision

 /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */

 /* vim:set ts=2 sw=2 sts=2 tw=80 et cindent: */

 /* 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 "nsMediaSniffer.h"

 #include "nsIHttpChannel.h"

 #include "nsString.h"

 #include "nsMimeTypes.h"

 #include "mozilla/ArrayUtils.h"

 #include "mozilla/ModuleUtils.h"

 #include "mp3sniff.h"

 #ifdef MOZ_WEBM

 #include "nestegg/nestegg.h"

 #endif

 #include "nsIClassInfoImpl.h"

 #include <algorithm>

 // The minimum number of bytes that are needed to attempt to sniff an mp4 file.

 static const unsigned MP4_MIN_BYTES_COUNT = 12;

 // The maximum number of bytes to consider when attempting to sniff a file.

 static const uint32_t MAX_BYTES_SNIFFED = 512;

 // The maximum number of bytes to consider when attempting to sniff for a mp3

 // bitstream.

 // This is 320kbps * 144 / 32kHz + 1 padding byte + 4 bytes of capture pattern.

 static const uint32_t MAX_BYTES_SNIFFED_MP3 = 320 * 144 / 32 + 1 + 4;

 NS_IMPL_ISUPPORTS(nsMediaSniffer, nsIContentSniffer)

 nsMediaSniffer::nsMediaSnifferEntry nsMediaSniffer::sSnifferEntries[] = {

   // The string OggS, followed by the null byte.

   PATTERN_ENTRY("\xFF\xFF\xFF\xFF\xFF", "OggS", APPLICATION_OGG),

   // The string RIFF, followed by four bytes, followed by the string WAVE

   PATTERN_ENTRY("\xFF\xFF\xFF\xFF\x00\x00\x00\x00\xFF\xFF\xFF\xFF", "RIFF\x00\x00\x00\x00WAVE", AUDIO_WAV),

   // mp3 with ID3 tags, the string "ID3".

   PATTERN_ENTRY("\xFF\xFF\xFF", "ID3", AUDIO_MP3)

 };

 // This function implements mp4 sniffing algorithm, described at

 // http://mimesniff.spec.whatwg.org/#signature-for-mp4

 static bool MatchesMP4(const uint8_t* aData, const uint32_t aLength)

 {

   if (aLength <= MP4_MIN_BYTES_COUNT) {

     return false;

   }

   // Conversion from big endian to host byte order.

   uint32_t boxSize = (uint32_t)(aData[3] | aData[2] << 8 | aData[1] << 16 | aData[0] << 24);

   // Boxsize should be evenly divisible by 4.

   if (boxSize % 4 || aLength < boxSize) {

     return false;

   }

   // The string "ftyp".

   if (aData[4] != 0x66 ||

       aData[5] != 0x74 ||

       aData[6] != 0x79 ||

       aData[7] != 0x70) {

     return false;

   }

   for (uint32_t i = 2; i <= boxSize / 4 - 1 ; i++) {

     if (i == 3) {

       continue;

     }

     // The string "mp42" or "mp41".

     if (aData[4*i]   == 0x6D &&

         aData[4*i+1] == 0x70 &&

         aData[4*i+2] == 0x34) {

       return true;

     }

     // The string "isom" or "iso2".

     if (aData[4*i]   == 0x69 &&

         aData[4*i+1] == 0x73 &&

         aData[4*i+2] == 0x6F &&

         (aData[4*i+3] == 0x6D || aData[4*i+3] == 0x32)) {

       return true;

     }

   }

   return false;

 }

 static bool MatchesWebM(const uint8_t* aData, const uint32_t aLength)

 {

 #ifdef MOZ_WEBM

   return nestegg_sniff((uint8_t*)aData, aLength) ? true : false;

 #else

   return false;

 #endif

 }

 // This function implements mp3 sniffing based on parsing

 // packet headers and looking for expected boundaries.

 static bool MatchesMP3(const uint8_t* aData, const uint32_t aLength)

 {

   return mp3_sniff(aData, (long)aLength);

 }

 NS_IMETHODIMP

 nsMediaSniffer::GetMIMETypeFromContent(nsIRequest* aRequest,

                                        const uint8_t* aData,

                                        const uint32_t aLength,

                                        nsACString& aSniffedType)

 {

   // For media, we want to sniff only if the Content-Type is unknown, or if it

   // is application/octet-stream.

   nsCOMPtr<nsIChannel> channel = do_QueryInterface(aRequest);

   if (channel) {

     nsAutoCString contentType;

     nsresult rv = channel->GetContentType(contentType);

     NS_ENSURE_SUCCESS(rv, rv);

     if (!contentType.IsEmpty() &&

         !contentType.EqualsLiteral(APPLICATION_OCTET_STREAM) &&

         !contentType.EqualsLiteral(UNKNOWN_CONTENT_TYPE)) {

       return NS_ERROR_NOT_AVAILABLE;

     }

   }

   const uint32_t clampedLength = std::min(aLength, MAX_BYTES_SNIFFED);

   for (uint32_t i = 0; i < mozilla::ArrayLength(sSnifferEntries); ++i) {

     const nsMediaSnifferEntry& currentEntry = sSnifferEntries[i];

     if (clampedLength < currentEntry.mLength || currentEntry.mLength == 0) {

       continue;

     }

     bool matched = true;

     for (uint32_t j = 0; j < currentEntry.mLength; ++j) {

       if ((currentEntry.mMask[j] & aData[j]) != currentEntry.mPattern[j]) {

         matched = false;

         break;

       }

     }

     if (matched) {

       aSniffedType.AssignASCII(currentEntry.mContentType);

       return NS_OK;

     }

   }

   if (MatchesMP4(aData, clampedLength)) {

     aSniffedType.AssignLiteral(VIDEO_MP4);

     return NS_OK;

   }

   if (MatchesWebM(aData, clampedLength)) {

     aSniffedType.AssignLiteral(VIDEO_WEBM);

     return NS_OK;

   }

   // Bug 950023: 512 bytes are often not enough to sniff for mp3.

   if (MatchesMP3(aData, std::min(aLength, MAX_BYTES_SNIFFED_MP3))) {

     aSniffedType.AssignLiteral(AUDIO_MP3);

     return NS_OK;

   }

   // Could not sniff the media type, we are required to set it to

   // application/octet-stream.

   aSniffedType.AssignLiteral(APPLICATION_OCTET_STREAM);

   return NS_ERROR_NOT_AVAILABLE;

 }