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      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 "components/crx_file/id_util.h"
      6 
      7 #include "base/files/file_path.h"
      8 #include "base/strings/string_number_conversions.h"
      9 #include "base/strings/string_util.h"
     10 #include "crypto/sha2.h"
     11 
     12 namespace {
     13 
     14 // Converts a normal hexadecimal string into the alphabet used by extensions.
     15 // We use the characters 'a'-'p' instead of '0'-'f' to avoid ever having a
     16 // completely numeric host, since some software interprets that as an IP
     17 // address.
     18 static void ConvertHexadecimalToIDAlphabet(std::string* id) {
     19   for (size_t i = 0; i < id->size(); ++i) {
     20     int val;
     21     if (base::HexStringToInt(
     22             base::StringPiece(id->begin() + i, id->begin() + i + 1), &val)) {
     23       (*id)[i] = val + 'a';
     24     } else {
     25       (*id)[i] = 'a';
     26     }
     27   }
     28 }
     29 
     30 }  // namespace
     31 
     32 namespace crx_file {
     33 namespace id_util {
     34 
     35 // First 16 bytes of SHA256 hashed public key.
     36 const size_t kIdSize = 16;
     37 
     38 std::string GenerateId(const std::string& input) {
     39   uint8 hash[kIdSize];
     40   crypto::SHA256HashString(input, hash, sizeof(hash));
     41   std::string output =
     42       base::StringToLowerASCII(base::HexEncode(hash, sizeof(hash)));
     43   ConvertHexadecimalToIDAlphabet(&output);
     44 
     45   return output;
     46 }
     47 
     48 std::string GenerateIdForPath(const base::FilePath& path) {
     49   base::FilePath new_path = MaybeNormalizePath(path);
     50   std::string path_bytes =
     51       std::string(reinterpret_cast<const char*>(new_path.value().data()),
     52                   new_path.value().size() * sizeof(base::FilePath::CharType));
     53   return GenerateId(path_bytes);
     54 }
     55 
     56 base::FilePath MaybeNormalizePath(const base::FilePath& path) {
     57 #if defined(OS_WIN)
     58   // Normalize any drive letter to upper-case. We do this for consistency with
     59   // net_utils::FilePathToFileURL(), which does the same thing, to make string
     60   // comparisons simpler.
     61   base::FilePath::StringType path_str = path.value();
     62   if (path_str.size() >= 2 && path_str[0] >= L'a' && path_str[0] <= L'z' &&
     63       path_str[1] == L':')
     64     path_str[0] = towupper(path_str[0]);
     65 
     66   return base::FilePath(path_str);
     67 #else
     68   return path;
     69 #endif
     70 }
     71 
     72 bool IdIsValid(const std::string& id) {
     73   // Verify that the id is legal.
     74   if (id.size() != (crx_file::id_util::kIdSize * 2))
     75     return false;
     76 
     77   // We only support lowercase IDs, because IDs can be used as URL components
     78   // (where GURL will lowercase it).
     79   std::string temp = base::StringToLowerASCII(id);
     80   for (size_t i = 0; i < temp.size(); i++)
     81     if (temp[i] < 'a' || temp[i] > 'p')
     82       return false;
     83 
     84   return true;
     85 }
     86 
     87 }  // namespace id_util
     88 }  // namespace crx_file
     89