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
magicNumber()40 static UInt32 magicNumber()
41 {
42 return 0xDECAF4EA;
43 }
44
fileExtension()45 const String& fileExtension()
46 {
47 DEFINE_STATIC_LOCAL(const String, extension, (".download"));
48 return extension;
49 }
50
appendResumeData(CFDataRef resumeData,const String & bundlePath)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
extractResumeData(const String & bundlePath)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