transmission/libtransmission/web.cc

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// This file Copyright © 2008-2022 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 <algorithm>
#include <condition_variable>
#include <list>
#include <map>
#include <memory>
#include <mutex>
#include <string>
#include <string_view>
#include <thread>
#ifdef _WIN32
#include <windows.h>
#include <wincrypt.h>
#endif
#include <curl/curl.h>
#include <event2/buffer.h>
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#include <fmt/core.h>
#include <fmt/format.h>
#include "crypto-utils.h"
#include "log.h"
#include "tr-assert.h"
#include "utils.h"
#include "web.h"
using namespace std::literals;
#if LIBCURL_VERSION_NUM >= 0x070F06 // CURLOPT_SOCKOPT* was added in 7.15.6
#define USE_LIBCURL_SOCKOPT
#endif
/***
****
***/
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;
}
#ifdef _WIN32
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 LPCWSTR const sys_store_names[] = {
L"CA",
L"ROOT",
};
for (size_t i = 0; i < TR_N_ELEMENTS(sys_store_names); ++i)
{
HCERTSTORE const sys_cert_store = CertOpenSystemStoreW(0, sys_store_names[i]);
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);
}
#endif
return CURLE_OK;
}
/***
****
***/
class tr_web::Impl
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{
public:
explicit Impl(Mediator& mediator_in)
: mediator{ mediator_in }
{
std::call_once(curl_init_flag, curlInit);
if (auto* bundle = tr_env_get_string("CURL_CA_BUNDLE", nullptr); bundle != nullptr)
{
curl_ca_bundle = bundle;
tr_free(bundle);
}
shareEverything();
if (curl_ssl_verify)
{
auto const* bundle = std::empty(curl_ca_bundle) ? "none" : curl_ca_bundle.c_str();
tr_logAddInfo(
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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(queued_tasks_mutex);
curl_thread = std::make_unique<std::thread>(curlThreadFunc, this);
}
~Impl()
{
run_mode = RunMode::CloseNow;
queued_tasks_cv.notify_one();
curl_thread->join();
}
void closeSoon()
{
run_mode = RunMode::CloseSoon;
queued_tasks_cv.notify_one();
}
[[nodiscard]] bool isClosed() const
{
return is_closed_;
}
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void fetch(FetchOptions&& options)
{
if (run_mode != RunMode::Run)
{
return;
}
auto const lock = std::unique_lock(queued_tasks_mutex);
queued_tasks.emplace_back(new Task{ *this, std::move(options) });
queued_tasks_cv.notify_one();
}
private:
class Task
{
private:
std::shared_ptr<evbuffer> const privbuf{ evbuffer_new(), evbuffer_free };
std::shared_ptr<CURL> const easy_handle{ curl_easy_init(), curl_easy_cleanup };
tr_web::FetchOptions options;
public:
Task(tr_web::Impl& impl_in, tr_web::FetchOptions&& options_in)
: options{ std::move(options_in) }
, impl{ impl_in }
{
response.user_data = options.done_func_user_data;
}
[[nodiscard]] auto* easy() const
{
return easy_handle.get();
}
[[nodiscard]] auto* body() const
{
return options.buffer != nullptr ? options.buffer : privbuf.get();
}
[[nodiscard]] auto const& speedLimitTag() const
{
return options.speed_limit_tag;
}
[[nodiscard]] auto const& url() const
{
return options.url;
}
[[nodiscard]] auto const& range() const
{
return options.range;
}
[[nodiscard]] auto const& cookies() const
{
return options.cookies;
}
[[nodiscard]] auto const& sndbuf() const
{
return options.sndbuf;
}
[[nodiscard]] auto const& rcvbuf() const
{
return options.rcvbuf;
}
[[nodiscard]] auto const& timeoutSecs() const
{
return options.timeout_secs;
}
void done()
{
if (options.done_func == nullptr)
{
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));
}
tr_web::Impl& impl;
tr_web::FetchResponse response;
};
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;
enum class RunMode
{
Run,
CloseSoon, // no new tasks; exit when running tasks finish
CloseNow // exit now even if tasks are running
};
RunMode run_mode = RunMode::Run;
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& 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(tr_time_msec(), task->easy());
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
static void initEasy(tr_web::Impl* impl, Task* task)
{
TR_ASSERT(std::this_thread::get_id() == impl->curl_thread->get_id());
auto* const e = task->easy();
(void)curl_easy_setopt(e, CURLOPT_SHARE, impl->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_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);
#ifdef USE_LIBCURL_SOCKOPT
(void)curl_easy_setopt(e, CURLOPT_SOCKOPTFUNCTION, onSocketCreated);
(void)curl_easy_setopt(e, CURLOPT_SOCKOPTDATA, task);
#endif
if (!impl->curl_ssl_verify)
{
(void)curl_easy_setopt(e, CURLOPT_SSL_VERIFYHOST, 0L);
(void)curl_easy_setopt(e, CURLOPT_SSL_VERIFYPEER, 0L);
}
else if (!std::empty(impl->curl_ca_bundle))
{
(void)curl_easy_setopt(e, CURLOPT_CAINFO, impl->curl_ca_bundle.c_str());
}
else
{
(void)curl_easy_setopt(e, CURLOPT_SSL_CTX_FUNCTION, ssl_context_func);
}
if (!impl->curl_proxy_ssl_verify)
{
(void)curl_easy_setopt(e, CURLOPT_PROXY_SSL_VERIFYHOST, 0L);
(void)curl_easy_setopt(e, CURLOPT_PROXY_SSL_VERIFYPEER, 0L);
}
else if (!std::empty(impl->curl_ca_bundle))
{
(void)curl_easy_setopt(e, CURLOPT_PROXY_CAINFO, impl->curl_ca_bundle.c_str());
}
if (auto const& ua = impl->user_agent; !std::empty(ua))
{
(void)curl_easy_setopt(e, CURLOPT_USERAGENT, ua.c_str());
}
(void)curl_easy_setopt(e, CURLOPT_TIMEOUT, task->timeoutSecs());
(void)curl_easy_setopt(e, CURLOPT_URL, task->url().c_str());
(void)curl_easy_setopt(e, CURLOPT_VERBOSE, impl->curl_verbose ? 1L : 0L);
(void)curl_easy_setopt(e, CURLOPT_WRITEDATA, task);
(void)curl_easy_setopt(e, CURLOPT_WRITEFUNCTION, onDataReceived);
(void)curl_easy_setopt(e, CURLOPT_MAXREDIRS, MaxRedirects);
if (auto const addrstr = impl->mediator.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 = impl->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_ENCODING, "identity");
(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->first + BandwidthPauseMsec < now)
{
curl_easy_pause(it->second, CURLPAUSE_CONT);
it = paused.erase(it);
}
else
{
++it;
}
}
}
// the thread started by Impl.curl_thread runs this function
static void curlThreadFunc(Impl* impl)
{
auto const multi = std::shared_ptr<CURLM>(curl_multi_init(), curl_multi_cleanup);
auto running_tasks = int{ 0 };
auto repeats = unsigned{};
for (;;)
{
if (impl->run_mode == RunMode::CloseNow)
{
break;
}
if (impl->run_mode == RunMode::CloseSoon && std::empty(impl->queued_tasks) && running_tasks == 0)
{
break;
}
{
auto lock = std::unique_lock(impl->queued_tasks_mutex);
// sleep until there's something to do
auto const has_work = [&running_tasks, impl]()
{
return running_tasks > 0 || !std::empty(impl->queued_tasks) || impl->run_mode != RunMode::Run;
};
if (!has_work())
{
impl->queued_tasks_cv.wait(lock, has_work);
}
// add queued tasks
for (auto* task : impl->queued_tasks)
{
tr_logAddTrace(fmt::format("adding task to curl: '{}'", task->url()));
initEasy(impl, task);
curl_multi_add_handle(multi.get(), task->easy());
}
impl->queued_tasks.clear();
impl->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)
{
tr_wait_msec(100);
}
}
else
{
repeats = 0;
}
// nonblocking update of the tasks
curl_multi_perform(multi.get(), &running_tasks);
// 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 && total_time >= task->timeoutSecs();
curl_multi_remove_handle(multi.get(), e);
task->done();
delete task;
}
}
}
// Discard any queued tasks.
// This shouldn't happen, but do it just in case
std::for_each(std::begin(impl->queued_tasks), std::end(impl->queued_tasks), [](auto* task) { delete task; });
impl->is_closed_ = true;
}
private:
std::shared_ptr<CURLSH> const curlsh_{ curl_share_init(), curl_share_cleanup };
std::mutex queued_tasks_mutex;
std::condition_variable queued_tasks_cv;
std::list<Task*> queued_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;
}
}
}
static std::once_flag curl_init_flag;
bool is_closed_ = false;
std::multimap<uint64_t /*tr_time_msec()*/, CURL*> paused_easy_handles;
static void curlInit()
{
// try to enable ssl for https support;
// but if that fails, try a plain vanilla init
if (curl_global_init(CURL_GLOBAL_SSL) != CURLE_OK)
{
curl_global_init(0);
}
}
};
std::once_flag tr_web::Impl::curl_init_flag;
tr_web::tr_web(Mediator& mediator)
: impl_{ std::make_unique<Impl>(mediator) }
{
}
tr_web::~tr_web() = default;
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));
}
bool tr_web::isClosed() const
{
return impl_->isClosed();
}
void tr_web::closeSoon()
{
impl_->closeSoon();
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}