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transmission/libtransmission/web.cc

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// This file Copyright © 2008-2023 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>
#ifdef _WIN32
#include <array>
#endif
#include <atomic>
#include <condition_variable>
#include <cstdint> // uint64_t
#include <list>
#include <map>
#include <memory>
#include <mutex>
#include <stack>
#include <string>
#include <thread>
#include <utility>
#ifdef _WIN32
#include <windows.h>
#include <wincrypt.h>
#include <ws2tcpip.h>
#else
#include <sys/socket.h> // setsockopt, SOL_SOCKET, SO_RC...
#endif
#include <curl/curl.h>
#include <event2/buffer.h>
#include <fmt/core.h>
#ifdef _WIN32
#include "libtransmission/crypto-utils.h"
#endif
#include "libtransmission/log.h"
#include "libtransmission/tr-assert.h"
#include "libtransmission/utils-ev.h"
#include "libtransmission/utils.h"
#include "libtransmission/web.h"
#include "libtransmission/web-utils.h"
using namespace std::literals;
#if LIBCURL_VERSION_NUM >= 0x070F06 // CURLOPT_SOCKOPT* was added in 7.15.6
#define USE_LIBCURL_SOCKOPT
#endif
// ---
namespace
{
namespace curl_helpers
{
struct ShareDeleter
{
void operator()(CURLSH* shared)
{
if (shared == nullptr)
{
return;
}
[[maybe_unused]] auto const status = curl_share_cleanup(shared);
TR_ASSERT(status == CURLSHE_OK);
}
};
using shared_unique_ptr = std::unique_ptr<CURLSH, ShareDeleter>;
struct MultiDeleter
{
void operator()(CURLM* multi) const
{
if (multi == nullptr)
{
return;
}
[[maybe_unused]] auto const status = curl_multi_cleanup(multi);
TR_ASSERT(status == CURLM_OK);
}
};
using multi_unique_ptr = std::unique_ptr<CURLM, MultiDeleter>;
struct EasyDeleter
{
void operator()(CURL* val) const noexcept
{
if (val != nullptr)
{
curl_easy_cleanup(val);
}
}
};
using easy_unique_ptr = std::unique_ptr<CURL, EasyDeleter>;
} // namespace curl_helpers
} // namespace
#ifdef _WIN32
static CURLcode ssl_context_func(CURL* /*curl*/, void* ssl_ctx, void* /*user_data*/)
{
auto const cert_store = tr_ssl_get_x509_store(ssl_ctx);
if (cert_store == nullptr)
{
return CURLE_OK;
}
curl_version_info_data const* const curl_ver = curl_version_info(CURLVERSION_NOW);
if (curl_ver->age >= 0 && strncmp(curl_ver->ssl_version, "Schannel", 8) == 0)
{
return CURLE_OK;
}
static auto constexpr SysStoreNames = std::array<LPCWSTR, 2>{
L"CA",
L"ROOT",
};
for (auto& sys_store_name : SysStoreNames)
{
HCERTSTORE const sys_cert_store = CertOpenSystemStoreW(0, sys_store_name);
if (sys_cert_store == nullptr)
{
continue;
}
PCCERT_CONTEXT sys_cert = nullptr;
while (true)
{
sys_cert = CertFindCertificateInStore(sys_cert_store, X509_ASN_ENCODING, 0, CERT_FIND_ANY, nullptr, sys_cert);
if (sys_cert == nullptr)
{
break;
}
tr_x509_cert_t const cert = tr_x509_cert_new(sys_cert->pbCertEncoded, sys_cert->cbCertEncoded);
if (cert == nullptr)
{
continue;
}
tr_x509_store_add(cert_store, cert);
tr_x509_cert_free(cert);
}
CertCloseStore(sys_cert_store, 0);
}
return CURLE_OK;
}
#endif
// ---
class tr_web::Impl
{
public:
explicit Impl(Mediator& mediator_in)
: mediator{ mediator_in }
{
if (auto bundle = tr_env_get_string("CURL_CA_BUNDLE"); !std::empty(bundle))
{
curl_ca_bundle = std::move(bundle);
}
shareEverything();
if (curl_ssl_verify)
{
auto const* bundle = std::empty(curl_ca_bundle) ? "none" : curl_ca_bundle.c_str();
tr_logAddInfo(
fmt::format(_("Will verify tracker certs using envvar CURL_CA_BUNDLE: {bundle}"), fmt::arg("bundle", bundle)));
tr_logAddInfo(_("NB: this only works if you built against libcurl with openssl or gnutls, NOT nss"));
tr_logAddInfo(_("NB: Invalid certs will appear as 'Could not connect to tracker' like many other errors"));
}
if (auto const& file = mediator.cookieFile(); file)
{
this->cookie_file = *file;
}
if (auto const& ua = mediator.userAgent(); ua)
{
this->user_agent = *ua;
}
auto const lock = std::unique_lock{ tasks_mutex_ };
curl_thread = std::make_unique<std::thread>(&Impl::curlThreadFunc, this);
}
Impl(Impl&&) = delete;
Impl(Impl const&) = delete;
Impl& operator=(Impl&&) = delete;
Impl& operator=(Impl const&) = delete;
~Impl()
{
deadline_ = mediator.now();
queued_tasks_cv_.notify_one();
curl_thread->join();
}
void startShutdown(std::chrono::milliseconds deadline)
{
deadline_ = mediator.now() + std::chrono::duration_cast<std::chrono::seconds>(deadline).count();
queued_tasks_cv_.notify_one();
}
void fetch(FetchOptions&& options)
{
if (deadline_exists())
{
return;
}
auto const lock = std::unique_lock{ tasks_mutex_ };
queued_tasks_.emplace_back(*this, std::move(options));
queued_tasks_cv_.notify_one();
}
class Task
{
public:
Task(tr_web::Impl& impl_in, tr_web::FetchOptions&& options_in)
: impl{ impl_in }
, options{ std::move(options_in) }
{
auto const parsed = tr_urlParse(options.url);
easy_ = parsed ? impl.get_easy(parsed->host) : nullptr;
response.user_data = options.done_func_user_data;
}
// Some of the curl_easy_setopt() args took a pointer to this task.
// Disable moving so that we don't accidentally invalidate those pointers.
Task(Task&&) = delete;
Task(Task const&) = delete;
Task& operator=(Task&&) = delete;
Task& operator=(Task const&) = delete;
~Task()
{
easy_dispose(easy_);
}
[[nodiscard]] constexpr auto* easy() const
{
return easy_;
}
[[nodiscard]] auto* body() const
{
return options.buffer != nullptr ? options.buffer : privbuf.get();
}
[[nodiscard]] constexpr auto const& speedLimitTag() const
{
return options.speed_limit_tag;
}
[[nodiscard]] constexpr auto const& url() const
{
return options.url;
}
[[nodiscard]] constexpr auto const& range() const
{
return options.range;
}
[[nodiscard]] constexpr auto const& cookies() const
{
return options.cookies;
}
[[nodiscard]] constexpr auto const& sndbuf() const
{
return options.sndbuf;
}
[[nodiscard]] constexpr auto const& rcvbuf() const
{
return options.rcvbuf;
}
[[nodiscard]] constexpr auto const& timeoutSecs() const
{
return options.timeout_secs;
}
[[nodiscard]] constexpr auto ipProtocol() const
{
switch (options.ip_proto)
{
case FetchOptions::IPProtocol::V4:
return CURL_IPRESOLVE_V4;
case FetchOptions::IPProtocol::V6:
return CURL_IPRESOLVE_V6;
default:
return CURL_IPRESOLVE_WHATEVER;
}
}
[[nodiscard]] auto publicAddress() const
{
switch (options.ip_proto)
{
case FetchOptions::IPProtocol::V4:
return impl.mediator.publicAddressV4();
case FetchOptions::IPProtocol::V6:
return impl.mediator.publicAddressV6();
default:
auto ip = impl.mediator.publicAddressV4();
if (ip == std::nullopt)
{
ip = impl.mediator.publicAddressV6();
}
return ip;
}
}
void done()
{
if (!options.done_func)
{
return;
}
response.body.assign(reinterpret_cast<char const*>(evbuffer_pullup(body(), -1)), evbuffer_get_length(body()));
impl.mediator.run(std::move(options.done_func), std::move(this->response));
options.done_func = {};
}
[[nodiscard]] bool operator==(Task const& that) const noexcept
{
return easy() == that.easy();
}
tr_web::Impl& impl;
tr_web::FetchResponse response;
private:
void easy_dispose(CURL* easy)
{
if (easy == nullptr)
{
return;
}
impl.paused_easy_handles.erase(easy_);
if (auto const url = tr_urlParse(options.url); url)
{
curl_easy_reset(easy);
impl.easy_pool_[std::string{ url->host }].emplace(easy);
}
else
{
curl_easy_cleanup(easy);
}
}
libtransmission::evhelpers::evbuffer_unique_ptr privbuf{ evbuffer_new() };
tr_web::FetchOptions options;
CURL* easy_;
};
static auto constexpr BandwidthPauseMsec = long{ 500 };
static auto constexpr DnsCacheTimeoutSecs = long{ 60 * 60 };
static auto constexpr MaxRedirects = long{ 10 };
bool const curl_verbose = tr_env_key_exists("TR_CURL_VERBOSE");
bool const curl_ssl_verify = !tr_env_key_exists("TR_CURL_SSL_NO_VERIFY");
bool const curl_proxy_ssl_verify = !tr_env_key_exists("TR_CURL_PROXY_SSL_NO_VERIFY");
Mediator& mediator;
std::string curl_ca_bundle;
std::string cookie_file;
std::string user_agent;
std::unique_ptr<std::thread> curl_thread;
// if unset: steady-state, all is good
// if set: do not accept new tasks
// if set and deadline reached: kill all remaining tasks
std::atomic<time_t> deadline_ = {};
[[nodiscard]] auto deadline() const
{
return deadline_.load();
}
[[nodiscard]] bool deadline_exists() const
{
return deadline() != time_t{};
}
[[nodiscard]] bool deadline_reached() const
{
return deadline_exists() && deadline() <= mediator.now();
}
[[nodiscard]] CURL* get_easy(std::string_view host)
{
CURL* easy = nullptr;
if (auto iter = easy_pool_.find(host); iter != std::end(easy_pool_) && !std::empty(iter->second))
{
easy = iter->second.top().release();
iter->second.pop();
}
if (easy == nullptr)
{
easy = curl_easy_init();
}
return easy;
}
static size_t onDataReceived(void* data, size_t size, size_t nmemb, void* vtask)
{
size_t const bytes_used = size * nmemb;
auto* task = static_cast<Task*>(vtask);
TR_ASSERT(std::this_thread::get_id() == task->impl.curl_thread->get_id());
if (auto const range = task->range(); range)
{
// https://curl.se/libcurl/c/CURLINFO_RESPONSE_CODE.html
// "The stored value will be zero if no server response code has been received"
static auto constexpr NoResponseCode = 0L;
static auto constexpr PartialContentResponseCode = 206L;
// Test for webservers that don't support partial-content, see GH #4595
auto code = long{};
(void)curl_easy_getinfo(task->easy(), CURLINFO_RESPONSE_CODE, &code);
if (code != NoResponseCode && code != PartialContentResponseCode)
{
tr_logAddWarn(fmt::format(
_("Couldn't fetch '{url}': expected HTTP response code {expected_code}, got {actual_code}"),
fmt::arg("url", task->url()),
fmt::arg("expected_code", PartialContentResponseCode),
fmt::arg("actual_code", code)));
// Tell curl to error out. Returning anything that's not
// `bytes_used` signals an error and causes the transfer
// to be aborted w/CURLE_WRITE_ERROR.
return bytes_used + 1;
}
}
if (auto const& tag = task->speedLimitTag(); tag)
{
// If this is more bandwidth than is allocated for this tag,
// then pause the torrent for a tick. curl will deliver `data`
// again when the transfer is unpaused.
if (task->impl.mediator.clamp(*tag, bytes_used) < bytes_used)
{
task->impl.paused_easy_handles.emplace(task->easy(), tr_time_msec());
return CURL_WRITEFUNC_PAUSE;
}
task->impl.mediator.notifyBandwidthConsumed(*tag, bytes_used);
}
evbuffer_add(task->body(), data, bytes_used);
tr_logAddTrace(fmt::format("wrote {} bytes to task {}'s buffer", bytes_used, fmt::ptr(task)));
return bytes_used;
}
#ifdef USE_LIBCURL_SOCKOPT
static int onSocketCreated(void* vtask, curl_socket_t fd, curlsocktype /*purpose*/)
{
auto const* const task = static_cast<Task const*>(vtask);
TR_ASSERT(std::this_thread::get_id() == task->impl.curl_thread->get_id());
// Ignore the sockopt() return values -- these are suggestions
// rather than hard requirements & it's OK for them to fail
if (auto const& buf = task->sndbuf(); buf)
{
(void)setsockopt(fd, SOL_SOCKET, SO_SNDBUF, reinterpret_cast<char const*>(&*buf), sizeof(*buf));
}
if (auto const& buf = task->rcvbuf(); buf)
{
(void)setsockopt(fd, SOL_SOCKET, SO_RCVBUF, reinterpret_cast<char const*>(&*buf), sizeof(*buf));
}
// return nonzero if this function encountered an error
return 0;
}
#endif
void initEasy(Task& task)
{
TR_ASSERT(std::this_thread::get_id() == curl_thread->get_id());
auto* const e = task.easy();
(void)curl_easy_setopt(e, CURLOPT_SHARE, shared());
(void)curl_easy_setopt(e, CURLOPT_DNS_CACHE_TIMEOUT, DnsCacheTimeoutSecs);
(void)curl_easy_setopt(e, CURLOPT_AUTOREFERER, 1L);
(void)curl_easy_setopt(e, CURLOPT_ACCEPT_ENCODING, "");
(void)curl_easy_setopt(e, CURLOPT_FOLLOWLOCATION, 1L);
(void)curl_easy_setopt(e, CURLOPT_MAXREDIRS, -1L);
(void)curl_easy_setopt(e, CURLOPT_NOSIGNAL, 1L);
(void)curl_easy_setopt(e, CURLOPT_PRIVATE, &task);
(void)curl_easy_setopt(e, CURLOPT_IPRESOLVE, task.ipProtocol());
#ifdef USE_LIBCURL_SOCKOPT
(void)curl_easy_setopt(e, CURLOPT_SOCKOPTFUNCTION, onSocketCreated);
(void)curl_easy_setopt(e, CURLOPT_SOCKOPTDATA, &task);
#endif
if (!curl_ssl_verify)
{
#if LIBCURL_VERSION_NUM >= 0x073400 /* 7.52.0 */
(void)curl_easy_setopt(e, CURLOPT_SSL_VERIFYHOST, 0L);
(void)curl_easy_setopt(e, CURLOPT_SSL_VERIFYPEER, 0L);
#endif
}
else if (!std::empty(curl_ca_bundle))
{
(void)curl_easy_setopt(e, CURLOPT_CAINFO, curl_ca_bundle.c_str());
}
else
{
#ifdef _WIN32
(void)curl_easy_setopt(e, CURLOPT_SSL_CTX_FUNCTION, ssl_context_func);
#endif
}
if (!curl_proxy_ssl_verify)
{
(void)curl_easy_setopt(e, CURLOPT_CAINFO, NULL);
(void)curl_easy_setopt(e, CURLOPT_CAPATH, NULL);
#if LIBCURL_VERSION_NUM >= 0x073400 /* 7.52.0 */
(void)curl_easy_setopt(e, CURLOPT_PROXY_SSL_VERIFYHOST, 0L);
(void)curl_easy_setopt(e, CURLOPT_PROXY_SSL_VERIFYPEER, 0L);
#endif
}
else if (!std::empty(curl_ca_bundle))
{
#if LIBCURL_VERSION_NUM >= 0x073400 /* 7.52.0 */
(void)curl_easy_setopt(e, CURLOPT_PROXY_CAINFO, curl_ca_bundle.c_str());
#endif
}
if (auto const& ua = user_agent; !std::empty(ua))
{
(void)curl_easy_setopt(e, CURLOPT_USERAGENT, ua.c_str());
}
(void)curl_easy_setopt(e, CURLOPT_TIMEOUT, static_cast<long>(task.timeoutSecs().count()));
(void)curl_easy_setopt(e, CURLOPT_URL, task.url().c_str());
(void)curl_easy_setopt(e, CURLOPT_VERBOSE, curl_verbose ? 1L : 0L);
(void)curl_easy_setopt(e, CURLOPT_WRITEDATA, &task);
(void)curl_easy_setopt(e, CURLOPT_WRITEFUNCTION, &tr_web::Impl::onDataReceived);
(void)curl_easy_setopt(e, CURLOPT_MAXREDIRS, MaxRedirects);
if (auto const addrstr = task.publicAddress(); addrstr)
{
(void)curl_easy_setopt(e, CURLOPT_INTERFACE, addrstr->c_str());
}
if (auto const& cookies = task.cookies(); cookies)
{
(void)curl_easy_setopt(e, CURLOPT_COOKIE, cookies->c_str());
}
if (auto const& file = cookie_file; !std::empty(file))
{
(void)curl_easy_setopt(e, CURLOPT_COOKIEFILE, file.c_str());
}
if (auto const& range = task.range(); range)
{
/* don't bother asking the server to compress webseed fragments */
(void)curl_easy_setopt(e, CURLOPT_ACCEPT_ENCODING, "identity");
(void)curl_easy_setopt(e, CURLOPT_HTTP_CONTENT_DECODING, 0L);
(void)curl_easy_setopt(e, CURLOPT_RANGE, range->c_str());
}
}
void resumePausedTasks()
{
TR_ASSERT(std::this_thread::get_id() == curl_thread->get_id());
auto& paused = paused_easy_handles;
if (std::empty(paused))
{
return;
}
auto const now = tr_time_msec();
for (auto it = std::begin(paused); it != std::end(paused);)
{
if (it->second + BandwidthPauseMsec < now)
{
curl_easy_pause(it->first, CURLPAUSE_CONT);
it = paused.erase(it);
}
else
{
++it;
}
}
}
[[nodiscard]] bool is_idle() const noexcept
{
return std::empty(queued_tasks_) && std::empty(running_tasks_);
}
void remove_task(Task const& task)
{
auto const lock = std::unique_lock{ tasks_mutex_ };
auto const iter = std::find(std::begin(running_tasks_), std::end(running_tasks_), task);
TR_ASSERT(iter != std::end(running_tasks_));
if (iter == std::end(running_tasks_))
{
return;
}
iter->done();
running_tasks_.erase(iter);
}
void timeout_task(Task& task)
{
task.response.status = 408; // request timed out
task.response.did_timeout = true;
remove_task(task);
}
// the thread started by Impl.curl_thread runs this function
void curlThreadFunc()
{
auto const multi = curl_helpers::multi_unique_ptr{ curl_multi_init() };
auto repeats = unsigned{};
for (;;)
{
if (deadline_reached())
{
while (!std::empty(running_tasks_))
{
auto& task = running_tasks_.front();
curl_multi_remove_handle(multi.get(), task.easy());
timeout_task(task);
}
}
if (deadline_exists() && is_idle())
{
break;
}
if (auto lock = std::unique_lock{ tasks_mutex_ }; lock.owns_lock())
{
// sleep until there's something to do
auto const stop_waiting = [this]()
{
return !is_idle() || !deadline_exists();
};
if (!stop_waiting())
{
queued_tasks_cv_.wait(lock, stop_waiting);
}
// add queued tasks
if (!std::empty(queued_tasks_))
{
for (auto& task : queued_tasks_)
{
initEasy(task);
curl_multi_add_handle(multi.get(), task.easy());
}
running_tasks_.splice(std::end(running_tasks_), queued_tasks_);
}
}
resumePausedTasks();
// Adapted from https://curl.se/libcurl/c/curl_multi_wait.html docs.
// 'numfds' being zero means either a timeout or no file descriptors to
// wait for. Try timeout on first occurrence, then assume no file
// descriptors and no file descriptors to wait for means wait for 100
// milliseconds.
auto numfds = int{};
curl_multi_wait(multi.get(), nullptr, 0, 1000, &numfds);
if (numfds == 0)
{
++repeats;
if (repeats > 1U)
{
std::this_thread::sleep_for(100ms);
}
}
else
{
repeats = 0;
}
// nonblocking update of the tasks
auto n_running = int{};
curl_multi_perform(multi.get(), &n_running);
// process any tasks that just finished
CURLMsg* msg = nullptr;
auto unused = int{};
while ((msg = curl_multi_info_read(multi.get(), &unused)) != nullptr)
{
if (msg->msg == CURLMSG_DONE && msg->easy_handle != nullptr)
{
auto* const e = msg->easy_handle;
Task* task = nullptr;
curl_easy_getinfo(e, CURLINFO_PRIVATE, (void*)&task);
auto req_bytes_sent = long{};
auto total_time = double{};
curl_easy_getinfo(e, CURLINFO_REQUEST_SIZE, &req_bytes_sent);
curl_easy_getinfo(e, CURLINFO_TOTAL_TIME, &total_time);
curl_easy_getinfo(e, CURLINFO_RESPONSE_CODE, &task->response.status);
task->response.did_connect = task->response.status > 0 || req_bytes_sent > 0;
task->response.did_timeout = task->response.status == 0 &&
std::chrono::duration<double>(total_time) >= task->timeoutSecs();
curl_multi_remove_handle(multi.get(), e);
remove_task(*task);
}
}
}
}
curl_helpers::shared_unique_ptr const curlsh_{ curl_share_init() };
std::map<std::string /*host*/, std::stack<curl_helpers::easy_unique_ptr>, std::less<>> easy_pool_;
std::mutex tasks_mutex_;
std::condition_variable queued_tasks_cv_;
std::list<Task> queued_tasks_;
std::list<Task> running_tasks_;
CURLSH* shared()
{
return curlsh_.get();
}
void shareEverything()
{
// Tell curl to share whatever it can.
// https://curl.se/libcurl/c/CURLSHOPT_SHARE.html
//
// The user's system probably has a different version of curl than
// we're compiling with; so instead of listing fields by name, just
// loop until curl says we've exhausted the list.
auto* const sh = shared();
for (long type = CURL_LOCK_DATA_COOKIE;; ++type)
{
if (curl_share_setopt(sh, CURLSHOPT_SHARE, type) != CURLSHE_OK)
{
tr_logAddDebug(fmt::format("CURLOPT_SHARE ended at {}", type));
return;
}
}
}
std::map<CURL*, uint64_t /*tr_time_msec()*/> paused_easy_handles;
};
tr_web::tr_web(Mediator& mediator)
: impl_{ std::make_unique<Impl>(mediator) }
{
}
tr_web::~tr_web()
{
impl_->startShutdown(0ms);
}
std::unique_ptr<tr_web> tr_web::create(Mediator& mediator)
{
return std::unique_ptr<tr_web>(new tr_web(mediator));
}
void tr_web::fetch(FetchOptions&& options)
{
impl_->fetch(std::move(options));
}
void tr_web::startShutdown(std::chrono::milliseconds deadline)
{
impl_->startShutdown(deadline);
}
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