transmission/libtransmission/subprocess-win32.cc

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// This file Copyright © 2011-2023 Mnemosyne LLC.
// It may be used under GPLv2 (SPDX: GPL-2.0-only), GPLv3 (SPDX: GPL-3.0-only),
// or any future license endorsed by Mnemosyne LLC.
// License text can be found in the licenses/ folder.
#include <algorithm>
#include <climits>
#include <cstring>
#include <cwchar>
#include <map>
#include <iterator>
#include <string>
#include <string_view>
#include <fmt/core.h>
#include <fmt/xchar.h> // for wchar_t support
#include <windows.h>
#include "libtransmission/transmission.h"
#include "libtransmission/error.h"
#include "libtransmission/subprocess.h"
#include "libtransmission/tr-assert.h"
#include "libtransmission/utils.h"
using namespace std::literals;
namespace
{
enum class tr_app_type
{
EXE,
BATCH
};
void set_system_error(tr_error** error, DWORD code, std::string_view what)
{
if (error == nullptr)
{
return;
}
if (auto const message = tr_win32_format_message(code); !std::empty(message))
{
tr_error_set(error, code, fmt::format(FMT_STRING("{:s} failed: {:s}"), what, message));
}
else
{
tr_error_set(error, code, fmt::format(FMT_STRING("{:s} failed: Unknown error: {:#08x}"), what, code));
}
}
// "The sort is case-insensitive, Unicode order, without regard to locale" © MSDN
class WStrICompare
{
public:
[[nodiscard]] auto compare(std::wstring_view a, std::wstring_view b) const noexcept // <=>
{
int diff = wcsnicmp(std::data(a), std::data(b), std::min(std::size(a), std::size(b)));
if (diff == 0)
{
diff = std::size(a) < std::size(b) ? -1 : (std::size(a) > std::size(b) ? 1 : 0);
}
return diff;
}
[[nodiscard]] auto operator()(std::wstring_view a, std::wstring_view b) const noexcept // <
{
return compare(a, b) < 0;
}
};
using SortedWideEnv = std::map<std::wstring, std::wstring, WStrICompare>;
/*
* Var1=Value1\0
* Var2=Value2\0
* Var3=Value3\0
* ...
* VarN=ValueN\0\0
*/
auto to_env_string(SortedWideEnv const& wide_env)
{
auto ret = std::vector<wchar_t>{};
for (auto const& [key, val] : wide_env)
{
fmt::format_to(std::back_inserter(ret), FMT_STRING(L"{:s}={:s}"), key, val);
ret.insert(std::end(ret), L'\0');
}
ret.insert(std::end(ret), L'\0');
return ret;
}
/*
* Var1=Value1\0
* Var2=Value2\0
* Var3=Value3\0
* ...
* VarN=ValueN\0\0
*/
auto parse_env_string(wchar_t const* env)
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{
auto sorted = SortedWideEnv{};
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for (;;)
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{
auto const line = std::wstring_view{ env };
if (std::empty(line))
{
break;
}
if (auto const pos = line.find(L'='); pos != std::string_view::npos)
{
sorted.insert_or_assign(std::wstring{ line.substr(0, pos) }, std::wstring{ line.substr(pos + 1) });
}
env += std::size(line) + 1 /*'\0'*/;
}
return sorted;
}
auto get_current_env()
{
auto env = SortedWideEnv{};
if (auto* pwch = GetEnvironmentStringsW(); pwch != nullptr)
{
env = parse_env_string(pwch);
FreeEnvironmentStringsW(pwch);
}
return env;
}
void append_argument(std::string& arguments, char const* argument)
{
if (!std::empty(arguments))
{
arguments += ' ';
}
if (!tr_str_is_empty(argument) && strpbrk(argument, " \t\n\v\"") == nullptr)
{
arguments += argument;
return;
}
arguments += '"';
for (char const* src = argument; *src != '\0';)
{
size_t backslash_count = 0;
while (*src == '\\')
{
++backslash_count;
++src;
}
switch (*src)
{
case '\0':
backslash_count = backslash_count * 2;
break;
case '"':
backslash_count = backslash_count * 2 + 1;
break;
}
if (backslash_count != 0)
{
arguments.append(backslash_count, '\\');
}
if (*src != '\0')
{
arguments += *src++;
}
}
arguments += '"';
}
bool contains_batch_metachars(char const* text)
{
/* First part - chars explicitly documented by `cmd.exe /?` as "special" */
return strpbrk(
text,
"&<>()@^|"
"%!^\"") != nullptr;
}
auto get_app_type(char const* app)
{
auto const lower = tr_strlower(app);
if (tr_strvEndsWith(lower, ".cmd") || tr_strvEndsWith(lower, ".bat"))
{
return tr_app_type::BATCH;
}
/* TODO: Support other types? */
return tr_app_type::EXE;
}
void append_app_launcher_arguments(tr_app_type app_type, std::string& args)
{
switch (app_type)
{
case tr_app_type::EXE:
break;
case tr_app_type::BATCH:
append_argument(args, "cmd.exe");
append_argument(args, "/d");
append_argument(args, "/e:off");
append_argument(args, "/v:off");
append_argument(args, "/s");
append_argument(args, "/c");
break;
default:
TR_ASSERT_MSG(false, "unsupported application type");
break;
}
}
std::wstring construct_cmd_line(char const* const* cmd)
{
auto const app_type = get_app_type(cmd[0]);
auto args = std::string{};
append_app_launcher_arguments(app_type, args);
for (size_t i = 0; cmd[i] != nullptr; ++i)
{
if (app_type == tr_app_type::BATCH && i > 0 && contains_batch_metachars(cmd[i]))
{
/* FIXME: My attempts to escape them one or another way didn't lead to anything good so far */
args.clear();
break;
}
append_argument(args, cmd[i]);
}
if (!std::empty(args))
{
return tr_win32_utf8_to_native(args);
}
return {};
}
} // namespace
bool tr_spawn_async(
char const* const* cmd,
std::map<std::string_view, std::string_view> const& env,
std::string_view work_dir,
tr_error** error)
{
// full_env = current_env + env;
auto full_env = get_current_env();
for (auto const& [key, val] : env)
{
full_env.insert_or_assign(tr_win32_utf8_to_native(key), tr_win32_utf8_to_native(val));
}
auto cmd_line = construct_cmd_line(cmd);
if (std::empty(cmd_line))
{
set_system_error(error, ERROR_INVALID_PARAMETER, "Constructing command line");
return false;
}
auto const current_dir = tr_win32_utf8_to_native(work_dir);
auto si = STARTUPINFOW{};
si.cb = sizeof(si);
si.dwFlags = STARTF_USESHOWWINDOW;
si.wShowWindow = SW_HIDE;
PROCESS_INFORMATION pi;
bool const ret = CreateProcessW(
nullptr,
std::data(cmd_line),
nullptr,
nullptr,
FALSE,
NORMAL_PRIORITY_CLASS | CREATE_UNICODE_ENVIRONMENT | CREATE_NO_WINDOW | CREATE_DEFAULT_ERROR_MODE,
std::empty(full_env) ? nullptr : to_env_string(full_env).data(),
std::empty(current_dir) ? nullptr : current_dir.c_str(),
&si,
&pi);
if (ret)
{
CloseHandle(pi.hThread);
CloseHandle(pi.hProcess);
}
else
{
set_system_error(error, GetLastError(), "Call to CreateProcess()");
}
return ret;
}