1 // Copyright 2014 The Chromium Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file.
4
5 #include "net/base/filename_util.h"
6
7 #include "base/file_util.h"
8 #include "base/files/file_path.h"
9 #include "base/path_service.h"
10 #include "base/strings/string_util.h"
11 #include "base/strings/sys_string_conversions.h"
12 #include "base/strings/utf_string_conversions.h"
13 #include "base/threading/thread_restrictions.h"
14 #include "net/base/escape.h"
15 #include "net/base/filename_util_internal.h"
16 #include "net/base/mime_util.h"
17 #include "net/base/net_string_util.h"
18 #include "net/http/http_content_disposition.h"
19 #include "url/gurl.h"
20
21 namespace net {
22
SanitizeGeneratedFileName(base::FilePath::StringType * filename,bool replace_trailing)23 void SanitizeGeneratedFileName(base::FilePath::StringType* filename,
24 bool replace_trailing) {
25 const base::FilePath::CharType kReplace[] = FILE_PATH_LITERAL("-");
26 if (filename->empty())
27 return;
28 if (replace_trailing) {
29 // Handle CreateFile() stripping trailing dots and spaces on filenames
30 // http://support.microsoft.com/kb/115827
31 size_t length = filename->size();
32 size_t pos = filename->find_last_not_of(FILE_PATH_LITERAL(" ."));
33 filename->resize((pos == std::string::npos) ? 0 : (pos + 1));
34 base::TrimWhitespace(*filename, base::TRIM_TRAILING, filename);
35 if (filename->empty())
36 return;
37 size_t trimmed = length - filename->size();
38 if (trimmed)
39 filename->insert(filename->end(), trimmed, kReplace[0]);
40 }
41 base::TrimString(*filename, FILE_PATH_LITERAL("."), filename);
42 if (filename->empty())
43 return;
44 // Replace any path information by changing path separators.
45 ReplaceSubstringsAfterOffset(filename, 0, FILE_PATH_LITERAL("/"), kReplace);
46 ReplaceSubstringsAfterOffset(filename, 0, FILE_PATH_LITERAL("\\"), kReplace);
47 }
48
49 // Returns the filename determined from the last component of the path portion
50 // of the URL. Returns an empty string if the URL doesn't have a path or is
51 // invalid. If the generated filename is not reliable,
52 // |should_overwrite_extension| will be set to true, in which case a better
53 // extension should be determined based on the content type.
GetFileNameFromURL(const GURL & url,const std::string & referrer_charset,bool * should_overwrite_extension)54 std::string GetFileNameFromURL(const GURL& url,
55 const std::string& referrer_charset,
56 bool* should_overwrite_extension) {
57 // about: and data: URLs don't have file names, but esp. data: URLs may
58 // contain parts that look like ones (i.e., contain a slash). Therefore we
59 // don't attempt to divine a file name out of them.
60 if (!url.is_valid() || url.SchemeIs("about") || url.SchemeIs("data"))
61 return std::string();
62
63 const std::string unescaped_url_filename = UnescapeURLComponent(
64 url.ExtractFileName(),
65 UnescapeRule::SPACES | UnescapeRule::URL_SPECIAL_CHARS);
66
67 // The URL's path should be escaped UTF-8, but may not be.
68 std::string decoded_filename = unescaped_url_filename;
69 if (!base::IsStringUTF8(decoded_filename)) {
70 // TODO(jshin): this is probably not robust enough. To be sure, we need
71 // encoding detection.
72 base::string16 utf16_output;
73 if (!referrer_charset.empty() &&
74 net::ConvertToUTF16(
75 unescaped_url_filename, referrer_charset.c_str(), &utf16_output)) {
76 decoded_filename = base::UTF16ToUTF8(utf16_output);
77 } else {
78 decoded_filename =
79 base::WideToUTF8(base::SysNativeMBToWide(unescaped_url_filename));
80 }
81 }
82 // If the URL contains a (possibly empty) query, assume it is a generator, and
83 // allow the determined extension to be overwritten.
84 *should_overwrite_extension = !decoded_filename.empty() && url.has_query();
85
86 return decoded_filename;
87 }
88
89 // Returns whether the specified extension is automatically integrated into the
90 // windows shell.
IsShellIntegratedExtension(const base::FilePath::StringType & extension)91 bool IsShellIntegratedExtension(const base::FilePath::StringType& extension) {
92 base::FilePath::StringType extension_lower = StringToLowerASCII(extension);
93
94 // http://msdn.microsoft.com/en-us/library/ms811694.aspx
95 // Right-clicking on shortcuts can be magical.
96 if ((extension_lower == FILE_PATH_LITERAL("local")) ||
97 (extension_lower == FILE_PATH_LITERAL("lnk")))
98 return true;
99
100 // http://www.juniper.net/security/auto/vulnerabilities/vuln2612.html
101 // Files become magical if they end in a CLSID, so block such extensions.
102 if (!extension_lower.empty() &&
103 (extension_lower[0] == FILE_PATH_LITERAL('{')) &&
104 (extension_lower[extension_lower.length() - 1] == FILE_PATH_LITERAL('}')))
105 return true;
106 return false;
107 }
108
109 // Returns whether the specified file name is a reserved name on windows.
110 // This includes names like "com2.zip" (which correspond to devices) and
111 // desktop.ini and thumbs.db which have special meaning to the windows shell.
IsReservedName(const base::FilePath::StringType & filename)112 bool IsReservedName(const base::FilePath::StringType& filename) {
113 // This list is taken from the MSDN article "Naming a file"
114 // http://msdn2.microsoft.com/en-us/library/aa365247(VS.85).aspx
115 // I also added clock$ because GetSaveFileName seems to consider it as a
116 // reserved name too.
117 static const char* const known_devices[] = {
118 "con", "prn", "aux", "nul", "com1", "com2", "com3", "com4",
119 "com5", "com6", "com7", "com8", "com9", "lpt1", "lpt2", "lpt3",
120 "lpt4", "lpt5", "lpt6", "lpt7", "lpt8", "lpt9", "clock$"};
121 #if defined(OS_WIN)
122 std::string filename_lower = StringToLowerASCII(base::WideToUTF8(filename));
123 #elif defined(OS_POSIX)
124 std::string filename_lower = StringToLowerASCII(filename);
125 #endif
126
127 for (size_t i = 0; i < arraysize(known_devices); ++i) {
128 // Exact match.
129 if (filename_lower == known_devices[i])
130 return true;
131 // Starts with "DEVICE.".
132 if (filename_lower.find(std::string(known_devices[i]) + ".") == 0)
133 return true;
134 }
135
136 static const char* const magic_names[] = {
137 // These file names are used by the "Customize folder" feature of the shell.
138 "desktop.ini",
139 "thumbs.db",
140 };
141
142 for (size_t i = 0; i < arraysize(magic_names); ++i) {
143 if (filename_lower == magic_names[i])
144 return true;
145 }
146
147 return false;
148 }
149
150 // Examines the current extension in |file_name| and modifies it if necessary in
151 // order to ensure the filename is safe. If |file_name| doesn't contain an
152 // extension or if |ignore_extension| is true, then a new extension will be
153 // constructed based on the |mime_type|.
154 //
155 // We're addressing two things here:
156 //
157 // 1) Usability. If there is no reliable file extension, we want to guess a
158 // reasonable file extension based on the content type.
159 //
160 // 2) Shell integration. Some file extensions automatically integrate with the
161 // shell. We block these extensions to prevent a malicious web site from
162 // integrating with the user's shell.
EnsureSafeExtension(const std::string & mime_type,bool ignore_extension,base::FilePath * file_name)163 void EnsureSafeExtension(const std::string& mime_type,
164 bool ignore_extension,
165 base::FilePath* file_name) {
166 // See if our file name already contains an extension.
167 base::FilePath::StringType extension = file_name->Extension();
168 if (!extension.empty())
169 extension.erase(extension.begin()); // Erase preceding '.'.
170
171 if ((ignore_extension || extension.empty()) && !mime_type.empty()) {
172 base::FilePath::StringType preferred_mime_extension;
173 std::vector<base::FilePath::StringType> all_mime_extensions;
174 net::GetPreferredExtensionForMimeType(mime_type, &preferred_mime_extension);
175 net::GetExtensionsForMimeType(mime_type, &all_mime_extensions);
176 // If the existing extension is in the list of valid extensions for the
177 // given type, use it. This avoids doing things like pointlessly renaming
178 // "foo.jpg" to "foo.jpeg".
179 if (std::find(all_mime_extensions.begin(),
180 all_mime_extensions.end(),
181 extension) != all_mime_extensions.end()) {
182 // leave |extension| alone
183 } else if (!preferred_mime_extension.empty()) {
184 extension = preferred_mime_extension;
185 }
186 }
187
188 #if defined(OS_WIN)
189 static const base::FilePath::CharType default_extension[] =
190 FILE_PATH_LITERAL("download");
191
192 // Rename shell-integrated extensions.
193 // TODO(asanka): Consider stripping out the bad extension and replacing it
194 // with the preferred extension for the MIME type if one is available.
195 if (IsShellIntegratedExtension(extension))
196 extension.assign(default_extension);
197 #endif
198
199 *file_name = file_name->ReplaceExtension(extension);
200 }
201
FilePathToString16(const base::FilePath & path,base::string16 * converted)202 bool FilePathToString16(const base::FilePath& path, base::string16* converted) {
203 #if defined(OS_WIN)
204 return base::WideToUTF16(
205 path.value().c_str(), path.value().size(), converted);
206 #elif defined(OS_POSIX)
207 std::string component8 = path.AsUTF8Unsafe();
208 return !component8.empty() &&
209 base::UTF8ToUTF16(component8.c_str(), component8.size(), converted);
210 #endif
211 }
212
GetSuggestedFilenameImpl(const GURL & url,const std::string & content_disposition,const std::string & referrer_charset,const std::string & suggested_name,const std::string & mime_type,const std::string & default_name,ReplaceIllegalCharactersCallback replace_illegal_characters_callback)213 base::string16 GetSuggestedFilenameImpl(
214 const GURL& url,
215 const std::string& content_disposition,
216 const std::string& referrer_charset,
217 const std::string& suggested_name,
218 const std::string& mime_type,
219 const std::string& default_name,
220 ReplaceIllegalCharactersCallback replace_illegal_characters_callback) {
221 // TODO: this function to be updated to match the httpbis recommendations.
222 // Talk to abarth for the latest news.
223
224 // We don't translate this fallback string, "download". If localization is
225 // needed, the caller should provide localized fallback in |default_name|.
226 static const base::FilePath::CharType kFinalFallbackName[] =
227 FILE_PATH_LITERAL("download");
228 std::string filename; // In UTF-8
229 bool overwrite_extension = false;
230
231 // Try to extract a filename from content-disposition first.
232 if (!content_disposition.empty()) {
233 HttpContentDisposition header(content_disposition, referrer_charset);
234 filename = header.filename();
235 }
236
237 // Then try to use the suggested name.
238 if (filename.empty() && !suggested_name.empty())
239 filename = suggested_name;
240
241 // Now try extracting the filename from the URL. GetFileNameFromURL() only
242 // looks at the last component of the URL and doesn't return the hostname as a
243 // failover.
244 if (filename.empty())
245 filename = GetFileNameFromURL(url, referrer_charset, &overwrite_extension);
246
247 // Finally try the URL hostname, but only if there's no default specified in
248 // |default_name|. Some schemes (e.g.: file:, about:, data:) do not have a
249 // host name.
250 if (filename.empty() && default_name.empty() && url.is_valid() &&
251 !url.host().empty()) {
252 // TODO(jungshik) : Decode a 'punycoded' IDN hostname. (bug 1264451)
253 filename = url.host();
254 }
255
256 bool replace_trailing = false;
257 base::FilePath::StringType result_str, default_name_str;
258 #if defined(OS_WIN)
259 replace_trailing = true;
260 result_str = base::UTF8ToUTF16(filename);
261 default_name_str = base::UTF8ToUTF16(default_name);
262 #else
263 result_str = filename;
264 default_name_str = default_name;
265 #endif
266 SanitizeGeneratedFileName(&result_str, replace_trailing);
267 if (result_str.find_last_not_of(FILE_PATH_LITERAL("-_")) ==
268 base::FilePath::StringType::npos) {
269 result_str = !default_name_str.empty()
270 ? default_name_str
271 : base::FilePath::StringType(kFinalFallbackName);
272 overwrite_extension = false;
273 }
274 replace_illegal_characters_callback.Run(&result_str, '-');
275 base::FilePath result(result_str);
276 GenerateSafeFileName(mime_type, overwrite_extension, &result);
277
278 base::string16 result16;
279 if (!FilePathToString16(result, &result16)) {
280 result = base::FilePath(default_name_str);
281 if (!FilePathToString16(result, &result16)) {
282 result = base::FilePath(kFinalFallbackName);
283 FilePathToString16(result, &result16);
284 }
285 }
286 return result16;
287 }
288
GenerateFileNameImpl(const GURL & url,const std::string & content_disposition,const std::string & referrer_charset,const std::string & suggested_name,const std::string & mime_type,const std::string & default_file_name,ReplaceIllegalCharactersCallback replace_illegal_characters_callback)289 base::FilePath GenerateFileNameImpl(
290 const GURL& url,
291 const std::string& content_disposition,
292 const std::string& referrer_charset,
293 const std::string& suggested_name,
294 const std::string& mime_type,
295 const std::string& default_file_name,
296 ReplaceIllegalCharactersCallback replace_illegal_characters_callback) {
297 base::string16 file_name =
298 GetSuggestedFilenameImpl(url,
299 content_disposition,
300 referrer_charset,
301 suggested_name,
302 mime_type,
303 default_file_name,
304 replace_illegal_characters_callback);
305
306 #if defined(OS_WIN)
307 base::FilePath generated_name(file_name);
308 #else
309 base::FilePath generated_name(
310 base::SysWideToNativeMB(base::UTF16ToWide(file_name)));
311 #endif
312
313 DCHECK(!generated_name.empty());
314
315 return generated_name;
316 }
317
318 } // namespace net
319