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/files/file_path.h"
8#include "base/files/file_util.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
21namespace net {
22
23void 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.
54std::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.
91bool IsShellIntegratedExtension(const base::FilePath::StringType& extension) {
92  base::FilePath::StringType extension_lower =
93      base::StringToLowerASCII(extension);
94
95  // http://msdn.microsoft.com/en-us/library/ms811694.aspx
96  // Right-clicking on shortcuts can be magical.
97  if ((extension_lower == FILE_PATH_LITERAL("local")) ||
98      (extension_lower == FILE_PATH_LITERAL("lnk")))
99    return true;
100
101  // http://www.juniper.net/security/auto/vulnerabilities/vuln2612.html
102  // Files become magical if they end in a CLSID, so block such extensions.
103  if (!extension_lower.empty() &&
104      (extension_lower[0] == FILE_PATH_LITERAL('{')) &&
105      (extension_lower[extension_lower.length() - 1] == FILE_PATH_LITERAL('}')))
106    return true;
107  return false;
108}
109
110// Returns whether the specified file name is a reserved name on windows.
111// This includes names like "com2.zip" (which correspond to devices) and
112// desktop.ini and thumbs.db which have special meaning to the windows shell.
113bool IsReservedName(const base::FilePath::StringType& filename) {
114  // This list is taken from the MSDN article "Naming a file"
115  // http://msdn2.microsoft.com/en-us/library/aa365247(VS.85).aspx
116  // I also added clock$ because GetSaveFileName seems to consider it as a
117  // reserved name too.
118  static const char* const known_devices[] = {
119      "con",  "prn",  "aux",  "nul",  "com1", "com2", "com3",  "com4",
120      "com5", "com6", "com7", "com8", "com9", "lpt1", "lpt2",  "lpt3",
121      "lpt4", "lpt5", "lpt6", "lpt7", "lpt8", "lpt9", "clock$"};
122#if defined(OS_WIN)
123  std::string filename_lower =
124      base::StringToLowerASCII(base::WideToUTF8(filename));
125#elif defined(OS_POSIX)
126  std::string filename_lower = base::StringToLowerASCII(filename);
127#endif
128
129  for (size_t i = 0; i < arraysize(known_devices); ++i) {
130    // Exact match.
131    if (filename_lower == known_devices[i])
132      return true;
133    // Starts with "DEVICE.".
134    if (filename_lower.find(std::string(known_devices[i]) + ".") == 0)
135      return true;
136  }
137
138  static const char* const magic_names[] = {
139    // These file names are used by the "Customize folder" feature of the shell.
140    "desktop.ini",
141    "thumbs.db",
142  };
143
144  for (size_t i = 0; i < arraysize(magic_names); ++i) {
145    if (filename_lower == magic_names[i])
146      return true;
147  }
148
149  return false;
150}
151
152// Examines the current extension in |file_name| and modifies it if necessary in
153// order to ensure the filename is safe.  If |file_name| doesn't contain an
154// extension or if |ignore_extension| is true, then a new extension will be
155// constructed based on the |mime_type|.
156//
157// We're addressing two things here:
158//
159// 1) Usability.  If there is no reliable file extension, we want to guess a
160//    reasonable file extension based on the content type.
161//
162// 2) Shell integration.  Some file extensions automatically integrate with the
163//    shell.  We block these extensions to prevent a malicious web site from
164//    integrating with the user's shell.
165void EnsureSafeExtension(const std::string& mime_type,
166                         bool ignore_extension,
167                         base::FilePath* file_name) {
168  // See if our file name already contains an extension.
169  base::FilePath::StringType extension = file_name->Extension();
170  if (!extension.empty())
171    extension.erase(extension.begin());  // Erase preceding '.'.
172
173  if ((ignore_extension || extension.empty()) && !mime_type.empty()) {
174    base::FilePath::StringType preferred_mime_extension;
175    std::vector<base::FilePath::StringType> all_mime_extensions;
176    net::GetPreferredExtensionForMimeType(mime_type, &preferred_mime_extension);
177    net::GetExtensionsForMimeType(mime_type, &all_mime_extensions);
178    // If the existing extension is in the list of valid extensions for the
179    // given type, use it. This avoids doing things like pointlessly renaming
180    // "foo.jpg" to "foo.jpeg".
181    if (std::find(all_mime_extensions.begin(),
182                  all_mime_extensions.end(),
183                  extension) != all_mime_extensions.end()) {
184      // leave |extension| alone
185    } else if (!preferred_mime_extension.empty()) {
186      extension = preferred_mime_extension;
187    }
188  }
189
190#if defined(OS_WIN)
191  static const base::FilePath::CharType default_extension[] =
192      FILE_PATH_LITERAL("download");
193
194  // Rename shell-integrated extensions.
195  // TODO(asanka): Consider stripping out the bad extension and replacing it
196  // with the preferred extension for the MIME type if one is available.
197  if (IsShellIntegratedExtension(extension))
198    extension.assign(default_extension);
199#endif
200
201  *file_name = file_name->ReplaceExtension(extension);
202}
203
204bool FilePathToString16(const base::FilePath& path, base::string16* converted) {
205#if defined(OS_WIN)
206  return base::WideToUTF16(
207      path.value().c_str(), path.value().size(), converted);
208#elif defined(OS_POSIX)
209  std::string component8 = path.AsUTF8Unsafe();
210  return !component8.empty() &&
211         base::UTF8ToUTF16(component8.c_str(), component8.size(), converted);
212#endif
213}
214
215base::string16 GetSuggestedFilenameImpl(
216    const GURL& url,
217    const std::string& content_disposition,
218    const std::string& referrer_charset,
219    const std::string& suggested_name,
220    const std::string& mime_type,
221    const std::string& default_name,
222    ReplaceIllegalCharactersCallback replace_illegal_characters_callback) {
223  // TODO: this function to be updated to match the httpbis recommendations.
224  // Talk to abarth for the latest news.
225
226  // We don't translate this fallback string, "download". If localization is
227  // needed, the caller should provide localized fallback in |default_name|.
228  static const base::FilePath::CharType kFinalFallbackName[] =
229      FILE_PATH_LITERAL("download");
230  std::string filename;  // In UTF-8
231  bool overwrite_extension = false;
232
233  // Try to extract a filename from content-disposition first.
234  if (!content_disposition.empty()) {
235    HttpContentDisposition header(content_disposition, referrer_charset);
236    filename = header.filename();
237  }
238
239  // Then try to use the suggested name.
240  if (filename.empty() && !suggested_name.empty())
241    filename = suggested_name;
242
243  // Now try extracting the filename from the URL.  GetFileNameFromURL() only
244  // looks at the last component of the URL and doesn't return the hostname as a
245  // failover.
246  if (filename.empty())
247    filename = GetFileNameFromURL(url, referrer_charset, &overwrite_extension);
248
249  // Finally try the URL hostname, but only if there's no default specified in
250  // |default_name|.  Some schemes (e.g.: file:, about:, data:) do not have a
251  // host name.
252  if (filename.empty() && default_name.empty() && url.is_valid() &&
253      !url.host().empty()) {
254    // TODO(jungshik) : Decode a 'punycoded' IDN hostname. (bug 1264451)
255    filename = url.host();
256  }
257
258  bool replace_trailing = false;
259  base::FilePath::StringType result_str, default_name_str;
260#if defined(OS_WIN)
261  replace_trailing = true;
262  result_str = base::UTF8ToUTF16(filename);
263  default_name_str = base::UTF8ToUTF16(default_name);
264#else
265  result_str = filename;
266  default_name_str = default_name;
267#endif
268  SanitizeGeneratedFileName(&result_str, replace_trailing);
269  if (result_str.find_last_not_of(FILE_PATH_LITERAL("-_")) ==
270      base::FilePath::StringType::npos) {
271    result_str = !default_name_str.empty()
272                     ? default_name_str
273                     : base::FilePath::StringType(kFinalFallbackName);
274    overwrite_extension = false;
275  }
276  replace_illegal_characters_callback.Run(&result_str, '-');
277  base::FilePath result(result_str);
278  GenerateSafeFileName(mime_type, overwrite_extension, &result);
279
280  base::string16 result16;
281  if (!FilePathToString16(result, &result16)) {
282    result = base::FilePath(default_name_str);
283    if (!FilePathToString16(result, &result16)) {
284      result = base::FilePath(kFinalFallbackName);
285      FilePathToString16(result, &result16);
286    }
287  }
288  return result16;
289}
290
291base::FilePath GenerateFileNameImpl(
292    const GURL& url,
293    const std::string& content_disposition,
294    const std::string& referrer_charset,
295    const std::string& suggested_name,
296    const std::string& mime_type,
297    const std::string& default_file_name,
298    ReplaceIllegalCharactersCallback replace_illegal_characters_callback) {
299  base::string16 file_name =
300      GetSuggestedFilenameImpl(url,
301                               content_disposition,
302                               referrer_charset,
303                               suggested_name,
304                               mime_type,
305                               default_file_name,
306                               replace_illegal_characters_callback);
307
308#if defined(OS_WIN)
309  base::FilePath generated_name(file_name);
310#else
311  base::FilePath generated_name(
312      base::SysWideToNativeMB(base::UTF16ToWide(file_name)));
313#endif
314
315  DCHECK(!generated_name.empty());
316
317  return generated_name;
318}
319
320}  // namespace net
321