tor-browser

The Tor Browser
git clone https://git.dasho.dev/tor-browser.git
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environment_internal.cc (4141B)

      1 // Copyright 2019 The Chromium Authors
      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 "base/process/environment_internal.h"
      6 
      7 #include <stddef.h>
      8 
      9 #include "build/build_config.h"
     10 
     11 #if BUILDFLAG(IS_POSIX) || BUILDFLAG(IS_FUCHSIA)
     12 #include <string.h>
     13 #endif
     14 
     15 #include <vector>
     16 
     17 namespace base {
     18 namespace internal {
     19 
     20 namespace {
     21 
     22 #if BUILDFLAG(IS_POSIX) || BUILDFLAG(IS_FUCHSIA) || BUILDFLAG(IS_WIN)
     23 // Parses a null-terminated input string of an environment block. The key is
     24 // placed into the given string, and the total length of the line, including
     25 // the terminating null, is returned.
     26 size_t ParseEnvLine(const NativeEnvironmentString::value_type* input,
     27                    NativeEnvironmentString* key) {
     28  // Skip to the equals or end of the string, this is the key.
     29  size_t cur = 0;
     30  while (input[cur] && input[cur] != '=')
     31    cur++;
     32  *key = NativeEnvironmentString(&input[0], cur);
     33 
     34  // Now just skip to the end of the string.
     35  while (input[cur])
     36    cur++;
     37  return cur + 1;
     38 }
     39 #endif
     40 
     41 }  // namespace
     42 
     43 #if BUILDFLAG(IS_POSIX) || BUILDFLAG(IS_FUCHSIA)
     44 
     45 std::unique_ptr<char* []> AlterEnvironment(const char* const* const env,
     46                                           const EnvironmentMap& changes) {
     47  std::string value_storage;  // Holds concatenated null-terminated strings.
     48  std::vector<size_t> result_indices;  // Line indices into value_storage.
     49 
     50  // First build up all of the unchanged environment strings. These are
     51  // null-terminated of the form "key=value".
     52  std::string key;
     53  for (size_t i = 0; env[i]; i++) {
     54    size_t line_length = ParseEnvLine(env[i], &key);
     55 
     56    // Keep only values not specified in the change vector.
     57    auto found_change = changes.find(key);
     58    if (found_change == changes.end()) {
     59      result_indices.push_back(value_storage.size());
     60      value_storage.append(env[i], line_length);
     61    }
     62  }
     63 
     64  // Now append all modified and new values.
     65  for (const auto& i : changes) {
     66    if (!i.second.empty()) {
     67      result_indices.push_back(value_storage.size());
     68      value_storage.append(i.first);
     69      value_storage.push_back('=');
     70      value_storage.append(i.second);
     71      value_storage.push_back(0);
     72    }
     73  }
     74 
     75  size_t pointer_count_required =
     76      result_indices.size() + 1 +  // Null-terminated array of pointers.
     77      (value_storage.size() + sizeof(char*) - 1) / sizeof(char*);  // Buffer.
     78  std::unique_ptr<char*[]> result(new char*[pointer_count_required]);
     79 
     80  // The string storage goes after the array of pointers.
     81  char* storage_data =
     82      reinterpret_cast<char*>(&result.get()[result_indices.size() + 1]);
     83  if (!value_storage.empty())
     84    memcpy(storage_data, value_storage.data(), value_storage.size());
     85 
     86  // Fill array of pointers at the beginning of the result.
     87  for (size_t i = 0; i < result_indices.size(); i++)
     88    result[i] = &storage_data[result_indices[i]];
     89  result[result_indices.size()] = 0;  // Null terminator.
     90 
     91  return result;
     92 }
     93 
     94 #elif BUILDFLAG(IS_WIN)
     95 
     96 NativeEnvironmentString AlterEnvironment(const wchar_t* env,
     97                                         const EnvironmentMap& changes) {
     98  NativeEnvironmentString result;
     99 
    100  // First build up all of the unchanged environment strings.
    101  const wchar_t* ptr = env;
    102  while (*ptr) {
    103    std::wstring key;
    104    size_t line_length = ParseEnvLine(ptr, &key);
    105 
    106    // Keep only values not specified in the change vector.
    107    if (changes.find(key) == changes.end()) {
    108      result.append(ptr, line_length);
    109    }
    110    ptr += line_length;
    111  }
    112 
    113  // Now append all modified and new values.
    114  for (const auto& i : changes) {
    115    // Windows environment blocks cannot handle keys or values with NULs.
    116    CHECK_EQ(std::wstring::npos, i.first.find(L'\0'));
    117    CHECK_EQ(std::wstring::npos, i.second.find(L'\0'));
    118    if (!i.second.empty()) {
    119      result += i.first;
    120      result.push_back('=');
    121      result += i.second;
    122      result.push_back('\0');
    123    }
    124  }
    125 
    126  // Add the terminating NUL.
    127  result.push_back('\0');
    128  return result;
    129 }
    130 
    131 #endif  // BUILDFLAG(IS_POSIX) || BUILDFLAG(IS_FUCHSIA)
    132 
    133 }  // namespace internal
    134 }  // namespace base