transmission/libtransmission/session-id.cc

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// This file Copyright © 2016-2022 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 <ctime>
#include <string_view>
#include <iterator> // for std::back_inserter
#ifndef _WIN32
#include <sys/stat.h>
#endif
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#include <fmt/format.h>
#include "transmission.h"
#include "session-id.h"
#include "crypto-utils.h" // for tr_rand_buf()
#include "error-types.h"
#include "error.h"
#include "file.h"
#include "log.h"
#include "platform.h"
#include "tr-strbuf.h" // for tr_pathbuf
#include "utils.h" // for _()
using namespace std::literals;
namespace
{
void get_lockfile_path(std::string_view session_id, tr_pathbuf& path)
{
fmt::format_to(std::back_inserter(path), FMT_STRING("{:s}/tr_session_id_{:s}"), tr_getSessionIdDir(), session_id);
}
tr_sys_file_t create_lockfile(std::string_view session_id)
{
if (std::empty(session_id))
{
return TR_BAD_SYS_FILE;
}
auto lockfile_path = tr_pathbuf{};
get_lockfile_path(session_id, lockfile_path);
tr_error* error = nullptr;
auto lockfile_fd = tr_sys_file_open(lockfile_path, TR_SYS_FILE_READ | TR_SYS_FILE_WRITE | TR_SYS_FILE_CREATE, 0600, &error);
if (lockfile_fd != TR_BAD_SYS_FILE)
{
if (tr_sys_file_lock(lockfile_fd, TR_SYS_FILE_LOCK_EX | TR_SYS_FILE_LOCK_NB, &error))
{
#ifndef _WIN32
/* Allow any user to lock the file regardless of current umask */
fchmod(lockfile_fd, 0644);
#endif
}
else
{
tr_sys_file_close(lockfile_fd);
lockfile_fd = TR_BAD_SYS_FILE;
}
}
if (error != nullptr)
{
tr_logAddWarn(fmt::format(
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_("Couldn't create '{path}': {error} ({error_code})"),
fmt::arg("path", lockfile_path),
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fmt::arg("error", error->message),
fmt::arg("error_code", error->code)));
tr_error_free(error);
}
return lockfile_fd;
}
void destroy_lockfile(tr_sys_file_t lockfile_fd, std::string_view session_id)
{
if (lockfile_fd != TR_BAD_SYS_FILE)
{
tr_sys_file_close(lockfile_fd);
}
if (!std::empty(session_id))
{
auto lockfile_path = tr_pathbuf{};
get_lockfile_path(session_id, lockfile_path);
tr_sys_path_remove(lockfile_path);
}
}
#ifndef _WIN32
auto constexpr WouldBlock = EWOULDBLOCK;
#else
auto constexpr WouldBlock = ERROR_LOCK_VIOLATION;
#endif
} // namespace
tr_session_id::session_id_t tr_session_id::make_session_id()
{
auto session_id = session_id_t{};
tr_rand_buffer(std::data(session_id), std::size(session_id));
static auto constexpr Pool = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"sv;
for (auto& chr : session_id)
{
chr = Pool[static_cast<unsigned char>(chr) % std::size(Pool)];
}
session_id.back() = '\0';
return session_id;
}
tr_session_id::~tr_session_id()
{
destroy_lockfile(current_lock_file_, std::data(current_value_));
destroy_lockfile(previous_lock_file_, std::data(previous_value_));
}
bool tr_session_id::isLocal(std::string_view session_id) noexcept
{
if (std::empty(session_id))
{
return false;
}
auto is_local = bool{ false };
auto lockfile_path = tr_pathbuf{};
get_lockfile_path(session_id, lockfile_path);
tr_error* error = nullptr;
if (auto lockfile_fd = tr_sys_file_open(lockfile_path, TR_SYS_FILE_READ, 0, &error); lockfile_fd == TR_BAD_SYS_FILE)
{
if (TR_ERROR_IS_ENOENT(error->code))
{
tr_error_clear(&error);
}
}
else
{
if (!tr_sys_file_lock(lockfile_fd, TR_SYS_FILE_LOCK_SH | TR_SYS_FILE_LOCK_NB, &error) && (error->code == WouldBlock))
{
is_local = true;
tr_error_clear(&error);
}
tr_sys_file_close(lockfile_fd);
}
if (error != nullptr)
{
tr_logAddWarn(fmt::format(
_("Couldn't open session lock file '{path}': {error} ({error_code})"),
fmt::arg("path", lockfile_path),
fmt::arg("error", error->message),
fmt::arg("error_code", error->code)));
tr_error_free(error);
}
return is_local;
}
std::string_view tr_session_id::sv() const noexcept
{
if (auto const now = get_current_time_(); now >= expires_at_)
{
destroy_lockfile(previous_lock_file_, std::data(previous_value_));
previous_value_ = current_value_;
previous_lock_file_ = current_lock_file_;
current_value_ = make_session_id();
current_lock_file_ = create_lockfile(std::data(current_value_));
expires_at_ = now + SessionIdDurationSec;
}
// -1 to strip the '\0'
return std::string_view{ std::data(current_value_), std::size(current_value_) - 1 };
}
char const* tr_session_id::c_str() const noexcept
{
return std::data(sv()); // current_value_ is zero-terminated
}