1 /* 2 * Copyright (C) 2011 Apple Inc. All rights reserved. 3 * 4 * Redistribution and use in source and binary forms, with or without 5 * modification, are permitted provided that the following conditions 6 * are met: 7 * 1. Redistributions of source code must retain the above copyright 8 * notice, this list of conditions and the following disclaimer. 9 * 2. Redistributions in binary form must reproduce the above copyright 10 * notice, this list of conditions and the following disclaimer in the 11 * documentation and/or other materials provided with the distribution. 12 * 13 * THIS SOFTWARE IS PROVIDED BY APPLE COMPUTER, INC. ``AS IS'' AND ANY 14 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 15 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 16 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE COMPUTER, INC. OR 17 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, 18 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, 19 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR 20 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY 21 * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 22 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE 23 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 24 */ 25 26 #include "config.h" 27 #include "DownloadBundle.h" 28 29 #include <CoreFoundation/CoreFoundation.h> 30 #include <io.h> 31 #include <sys/stat.h> 32 #include <sys/types.h> 33 #include <wtf/text/CString.h> 34 #include <wtf/text/WTFString.h> 35 36 namespace WebCore { 37 38 namespace DownloadBundle { 39 40 static UInt32 magicNumber() 41 { 42 return 0xDECAF4EA; 43 } 44 45 const String& fileExtension() 46 { 47 DEFINE_STATIC_LOCAL(const String, extension, (".download")); 48 return extension; 49 } 50 51 bool appendResumeData(CFDataRef resumeData, const String& bundlePath) 52 { 53 if (!resumeData) { 54 LOG_ERROR("Invalid resume data to write to bundle path"); 55 return false; 56 } 57 if (bundlePath.isEmpty()) { 58 LOG_ERROR("Cannot write resume data to empty download bundle path"); 59 return false; 60 } 61 62 String nullifiedPath = bundlePath; 63 FILE* bundle = 0; 64 if (_wfopen_s(&bundle, nullifiedPath.charactersWithNullTermination(), TEXT("ab")) || !bundle) { 65 LOG_ERROR("Failed to open file %s to append resume data", bundlePath.ascii().data()); 66 return false; 67 } 68 69 bool result = false; 70 71 const UInt8* resumeBytes = CFDataGetBytePtr(resumeData); 72 ASSERT(resumeBytes); 73 if (!resumeBytes) 74 goto exit; 75 76 CFIndex resumeLength = CFDataGetLength(resumeData); 77 ASSERT(resumeLength > 0); 78 if (resumeLength < 1) 79 goto exit; 80 81 if (fwrite(resumeBytes, 1, resumeLength, bundle) != resumeLength) { 82 LOG_ERROR("Failed to write resume data to the bundle - errno(%i)", errno); 83 goto exit; 84 } 85 86 if (fwrite(&resumeLength, 4, 1, bundle) != 1) { 87 LOG_ERROR("Failed to write footer length to the bundle - errno(%i)", errno); 88 goto exit; 89 } 90 91 const UInt32& magic = magicNumber(); 92 if (fwrite(&magic, 4, 1, bundle) != 1) { 93 LOG_ERROR("Failed to write footer magic number to the bundle - errno(%i)", errno); 94 goto exit; 95 } 96 97 result = true; 98 exit: 99 fclose(bundle); 100 return result; 101 } 102 103 CFDataRef extractResumeData(const String& bundlePath) 104 { 105 if (bundlePath.isEmpty()) { 106 LOG_ERROR("Cannot create resume data from empty download bundle path"); 107 return 0; 108 } 109 110 // Open a handle to the bundle file 111 String nullifiedPath = bundlePath; 112 FILE* bundle = 0; 113 if (_wfopen_s(&bundle, nullifiedPath.charactersWithNullTermination(), TEXT("r+b")) || !bundle) { 114 LOG_ERROR("Failed to open file %s to get resume data", bundlePath.ascii().data()); 115 return 0; 116 } 117 118 CFDataRef result = 0; 119 Vector<UInt8> footerBuffer; 120 121 // Stat the file to get its size 122 struct _stat64 fileStat; 123 if (_fstat64(_fileno(bundle), &fileStat)) 124 goto exit; 125 126 // Check for the bundle magic number at the end of the file 127 fpos_t footerMagicNumberPosition = fileStat.st_size - 4; 128 ASSERT(footerMagicNumberPosition >= 0); 129 if (footerMagicNumberPosition < 0) 130 goto exit; 131 if (fsetpos(bundle, &footerMagicNumberPosition)) 132 goto exit; 133 134 UInt32 footerMagicNumber = 0; 135 if (fread(&footerMagicNumber, 4, 1, bundle) != 1) { 136 LOG_ERROR("Failed to read footer magic number from the bundle - errno(%i)", errno); 137 goto exit; 138 } 139 140 if (footerMagicNumber != magicNumber()) { 141 LOG_ERROR("Footer's magic number does not match 0x%X - errno(%i)", magicNumber(), errno); 142 goto exit; 143 } 144 145 // Now we're *reasonably* sure this is a .download bundle we actually wrote. 146 // Get the length of the resume data 147 fpos_t footerLengthPosition = fileStat.st_size - 8; 148 ASSERT(footerLengthPosition >= 0); 149 if (footerLengthPosition < 0) 150 goto exit; 151 152 if (fsetpos(bundle, &footerLengthPosition)) 153 goto exit; 154 155 UInt32 footerLength = 0; 156 if (fread(&footerLength, 4, 1, bundle) != 1) { 157 LOG_ERROR("Failed to read ResumeData length from the bundle - errno(%i)", errno); 158 goto exit; 159 } 160 161 // Make sure theres enough bytes to read in for the resume data, and perform the read 162 fpos_t footerStartPosition = fileStat.st_size - 8 - footerLength; 163 ASSERT(footerStartPosition >= 0); 164 if (footerStartPosition < 0) 165 goto exit; 166 if (fsetpos(bundle, &footerStartPosition)) 167 goto exit; 168 169 footerBuffer.resize(footerLength); 170 if (fread(footerBuffer.data(), 1, footerLength, bundle) != footerLength) { 171 LOG_ERROR("Failed to read ResumeData from the bundle - errno(%i)", errno); 172 goto exit; 173 } 174 175 // CFURLDownload will seek to the appropriate place in the file (before our footer) and start overwriting from there 176 // However, say we were within a few hundred bytes of the end of a download when it was paused - 177 // The additional footer extended the length of the file beyond its final length, and there will be junk data leftover 178 // at the end. Therefore, now that we've retrieved the footer data, we need to truncate it. 179 if (errno_t resizeError = _chsize_s(_fileno(bundle), footerStartPosition)) { 180 LOG_ERROR("Failed to truncate the resume footer off the end of the file - errno(%i)", resizeError); 181 goto exit; 182 } 183 184 // Finally, make the resume data. Now, it is possible by some twist of fate the bundle magic number 185 // was naturally at the end of the file and its not actually a valid bundle. That, or someone engineered 186 // it that way to try to attack us. In that cause, this CFData will successfully create but when we 187 // actually try to start the CFURLDownload using this bogus data, it will fail and we will handle that gracefully 188 result = CFDataCreate(0, footerBuffer.data(), footerLength); 189 exit: 190 fclose(bundle); 191 return result; 192 } 193 194 } // namespace DownloadBundle 195 196 } // namespace WebCore 197