httpserver.cpp

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// Copyright (c) 2015 The Bitcoin Core developers
// Copyright (c) 2015-2018 The PIVX developers
// Copyright (c) 2018-2020 The DAPS Project developers
// Distributed under the MIT software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
#include "httpserver.h"
 
#include "chainparamsbase.h"
#include "compat.h"
#include "util.h"
#include "netbase.h"
#include "rpc/protocol.h" // For HTTP status codes
#include "sync.h"
#include "guiinterface.h"
 
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
 
#include <sys/types.h>
#include <sys/stat.h>
#include <signal.h>
#include <future>
 
#include <deque>
#include <event2/event.h>
#include <event2/http.h>
#include <event2/thread.h>
#include <event2/buffer.h>
#include <event2/bufferevent.h>
#include <event2/util.h>
#include <event2/keyvalq_struct.h>
 
#ifdef EVENT__HAVE_NETINET_IN_H
#include <netinet/in.h>
#ifdef _XOPEN_SOURCE_EXTENDED
#include <arpa/inet.h>
#endif
#endif
 
static const size_t MAX_HEADERS_SIZE = 8192;
 
class HTTPWorkItem : public HTTPClosure
{
public:
    HTTPWorkItem(HTTPRequest* req, const std::string &path, const HTTPRequestHandler& func):
        req(req), path(path), func(func)
    {
    }
    void operator()()
    {
        func(req.get(), path);
    }
 
    std::unique_ptr<HTTPRequest> req;
 
private:
    std::string path;
    HTTPRequestHandler func;
};
 
template <typename WorkItem>
class WorkQueue
{
private:
    std::mutex cs;
    std::condition_variable cond;
    /* XXX in C++11 we can use std::unique_ptr here and avoid manual cleanup */
    std::deque<WorkItem*> queue;
    bool running;
    size_t maxDepth;
    int numThreads;
 
    class ThreadCounter
    {
    public:
        WorkQueue &wq;
        ThreadCounter(WorkQueue &w): wq(w)
        {
            std::lock_guard<std::mutex> lock(wq.cs);
            wq.numThreads += 1;
        }
        ~ThreadCounter()
        {
            std::lock_guard<std::mutex> lock(wq.cs);
            wq.numThreads -= 1;
            wq.cond.notify_all();
        }
    };
 
public:
    WorkQueue(size_t maxDepth) : running(true),
                                 maxDepth(maxDepth),
                                 numThreads(0)
    {
    }
    /*( Precondition: worker threads have all stopped
     * (call WaitExit)
     */
    ~WorkQueue()
    {
        while (!queue.empty()) {
            delete queue.front();
            queue.pop_front();
        }
    }
    bool Enqueue(WorkItem* item)
    {
        std::unique_lock<std::mutex> lock(cs);
        if (queue.size() >= maxDepth) {
            return false;
        }
        queue.push_back(item);
        cond.notify_one();
        return true;
    }
    void Run()
    {
        ThreadCounter count(*this);
        while (running) {
            WorkItem* i = 0;
            {
                std::unique_lock<std::mutex> lock(cs);
                while (running && queue.empty())
                    cond.wait(lock);
                if (!running)
                    break;
                i = queue.front();
                queue.pop_front();
            }
            (*i)();
            delete i;
        }
    }
    void Interrupt()
    {
        std::unique_lock<std::mutex> lock(cs);
        running = false;
        cond.notify_all();
    }
    void WaitExit()
    {
        std::unique_lock<std::mutex> lock(cs);
        while (numThreads > 0)
            cond.wait(lock);
    }
 
    size_t Depth()
    {
        std::unique_lock<std::mutex> lock(cs);
        return queue.size();
    }
};
 
struct HTTPPathHandler
{
    HTTPPathHandler() {}
    HTTPPathHandler(std::string prefix, bool exactMatch, HTTPRequestHandler handler):
        prefix(prefix), exactMatch(exactMatch), handler(handler)
    {
    }
    std::string prefix;
    bool exactMatch;
    HTTPRequestHandler handler;
};
 
static struct event_base* eventBase = 0;
struct evhttp* eventHTTP = 0;
static std::vector<CSubNet> rpc_allow_subnets;
static WorkQueue<HTTPClosure>* workQueue = 0;
std::vector<HTTPPathHandler> pathHandlers;
std::vector<evhttp_bound_socket *> boundSockets;
 
static bool ClientAllowed(const CNetAddr& netaddr)
{
    if (!netaddr.IsValid())
        return false;
    for (const CSubNet& subnet : rpc_allow_subnets)
        if (subnet.Match(netaddr))
            return true;
    return false;
}
 
static bool InitHTTPAllowList()
{
    rpc_allow_subnets.clear();
    CNetAddr localv4;
    CNetAddr localv6;
    LookupHost("127.0.0.1", localv4, false);
    LookupHost("::1", localv6, false);
    rpc_allow_subnets.push_back(CSubNet(localv4, 8));      // always allow IPv4 local subnet
    rpc_allow_subnets.push_back(CSubNet(localv6));         // always allow IPv6 localhost
    if (mapMultiArgs.count("-rpcallowip")) {
        const std::vector<std::string>& vAllow = mapMultiArgs["-rpcallowip"];
        for (std::string strAllow : vAllow) {
            CSubNet subnet;
            LookupSubNet(strAllow.c_str(), subnet);
            if (!subnet.IsValid()) {
                uiInterface.ThreadSafeMessageBox(
                    strprintf("Invalid -rpcallowip subnet specification: %s. Valid are a single IP (e.g. 1.2.3.4), a network/netmask (e.g. 1.2.3.4/255.255.255.0) or a network/CIDR (e.g. 1.2.3.4/24).", strAllow),
                    "", CClientUIInterface::MSG_ERROR);
                return false;
            }
            rpc_allow_subnets.push_back(subnet);
        }
    }
    std::string strAllowed;
    for (const CSubNet& subnet : rpc_allow_subnets)
        strAllowed += subnet.ToString() + " ";
    LogPrint(BCLog::HTTP, "Allowing HTTP connections from: %s\n", strAllowed);
    return true;
}
 
static std::string RequestMethodString(HTTPRequest::RequestMethod m)
{
    switch (m) {
    case HTTPRequest::GET:
        return "GET";
        break;
    case HTTPRequest::POST:
        return "POST";
        break;
    case HTTPRequest::HEAD:
        return "HEAD";
        break;
    case HTTPRequest::PUT:
        return "PUT";
        break;
    default:
        return "unknown";
    }
}
 
static void http_request_cb(struct evhttp_request* req, void* arg)
{
    // Disable reading to work around a libevent bug, fixed in 2.2.0.
    if (event_get_version_number() >= 0x02010600 && event_get_version_number() < 0x02020001) {
        evhttp_connection* conn = evhttp_request_get_connection(req);
        if (conn) {
            bufferevent* bev = evhttp_connection_get_bufferevent(conn);
            if (bev) {
                bufferevent_disable(bev, EV_READ);
            }
        }
    }
    std::unique_ptr<HTTPRequest> hreq(new HTTPRequest(req));
 
    LogPrint(BCLog::HTTP, "Received a %s request for %s from %s\n",
             RequestMethodString(hreq->GetRequestMethod()), hreq->GetURI(), hreq->GetPeer().ToString());
 
    // Early address-based allow check
    if (!ClientAllowed(hreq->GetPeer())) {
        hreq->WriteReply(HTTP_FORBIDDEN);
        return;
    }
 
    // Early reject unknown HTTP methods
    if (hreq->GetRequestMethod() == HTTPRequest::UNKNOWN) {
        hreq->WriteReply(HTTP_BADMETHOD);
        return;
    }
 
    // Find registered handler for prefix
    std::string strURI = hreq->GetURI();
    std::string path;
    std::vector<HTTPPathHandler>::const_iterator i = pathHandlers.begin();
    std::vector<HTTPPathHandler>::const_iterator iend = pathHandlers.end();
    for (; i != iend; ++i) {
        bool match = false;
        if (i->exactMatch)
            match = (strURI == i->prefix);
        else
            match = (strURI.substr(0, i->prefix.size()) == i->prefix);
        if (match) {
            path = strURI.substr(i->prefix.size());
            break;
        }
    }
 
    // Dispatch to worker thread
    if (i != iend) {
        std::unique_ptr<HTTPWorkItem> item(new HTTPWorkItem(hreq.release(), path, i->handler));
        assert(workQueue);
        if (workQueue->Enqueue(item.get()))
            item.release(); /* if true, queue took ownership */
        else
            item->req->WriteReply(HTTP_INTERNAL, "Work queue depth exceeded");
    } else {
        hreq->WriteReply(HTTP_NOTFOUND);
    }
}
 
static void http_reject_request_cb(struct evhttp_request* req, void*)
{
    LogPrint(BCLog::HTTP, "Rejecting request while shutting down\n");
    evhttp_send_error(req, HTTP_SERVUNAVAIL, NULL);
}
static bool ThreadHTTP(struct event_base* base, struct evhttp* http)
{
    util::ThreadRename("bitcoin-http");
    LogPrint(BCLog::HTTP, "Entering http event loop\n");
    event_base_dispatch(base);
    // Event loop will be interrupted by InterruptHTTPServer()
    LogPrint(BCLog::HTTP, "Exited http event loop\n");
    return event_base_got_break(base) == 0;
}
 
static bool HTTPBindAddresses(struct evhttp* http)
{
    int defaultPort = GetArg("-rpcport", BaseParams().RPCPort());
    std::vector<std::pair<std::string, uint16_t> > endpoints;
 
    // Determine what addresses to bind to
    if (!mapArgs.count("-rpcallowip")) { // Default to loopback if not allowing external IPs
        endpoints.push_back(std::make_pair("::1", defaultPort));
        endpoints.push_back(std::make_pair("127.0.0.1", defaultPort));
        if (mapArgs.count("-rpcbind")) {
            LogPrintf("WARNING: option -rpcbind was ignored because -rpcallowip was not specified, refusing to allow everyone to connect\n");
        }
    } else if (mapArgs.count("-rpcbind")) { // Specific bind address
        const std::vector<std::string>& vbind = mapMultiArgs["-rpcbind"];
        for (std::vector<std::string>::const_iterator i = vbind.begin(); i != vbind.end(); ++i) {
            int port = defaultPort;
            std::string host;
            SplitHostPort(*i, port, host);
            endpoints.push_back(std::make_pair(host, port));
        }
    } else { // No specific bind address specified, bind to any
        endpoints.push_back(std::make_pair("::", defaultPort));
        endpoints.push_back(std::make_pair("0.0.0.0", defaultPort));
    }
 
    // Bind addresses
    for (std::vector<std::pair<std::string, uint16_t> >::iterator i = endpoints.begin(); i != endpoints.end(); ++i) {
        LogPrint(BCLog::HTTP, "Binding RPC on address %s port %i\n", i->first, i->second);
        evhttp_bound_socket *bind_handle = evhttp_bind_socket_with_handle(http, i->first.empty() ? NULL : i->first.c_str(), i->second);
        if (bind_handle) {
            boundSockets.push_back(bind_handle);
        } else {
            LogPrintf("Binding RPC on address %s port %i failed.\n", i->first, i->second);
        }
    }
    return !boundSockets.empty();
}
 
static void HTTPWorkQueueRun(WorkQueue<HTTPClosure>* queue)
{
    util::ThreadRename("bitcoin-httpworker");
    queue->Run();
}
 
static void libevent_log_cb(int severity, const char *msg)
{
#ifndef EVENT_LOG_WARN
// EVENT_LOG_WARN was added in 2.0.19; but before then _EVENT_LOG_WARN existed.
# define EVENT_LOG_WARN _EVENT_LOG_WARN
#endif
    if (severity >= EVENT_LOG_WARN) // Log warn messages and higher without debug category
        LogPrintf("libevent: %s\n", msg);
    else
        LogPrint(BCLog::LIBEVENT, "libevent: %s\n", msg);
}
 
bool InitHTTPServer()
{
    struct evhttp* http = 0;
    struct event_base* base = 0;
 
    if (!InitHTTPAllowList())
        return false;
 
    if (GetBoolArg("-rpcssl", false)) {
        uiInterface.ThreadSafeMessageBox(
            "SSL mode for RPC (-rpcssl) is no longer supported.",
            "", CClientUIInterface::MSG_ERROR);
        return false;
    }
 
    // Redirect libevent's logging to our own log
    event_set_log_callback(&libevent_log_cb);
    // Update libevent's log handling. Returns false if our version of
    // libevent doesn't support debug logging, in which case we should
    // clear the BCLog::LIBEVENT flag.
    if (!UpdateHTTPServerLogging(g_logger->WillLogCategory(BCLog::LIBEVENT))) {
        g_logger->DisableCategory(BCLog::LIBEVENT);
    }
 
#ifdef WIN32
    evthread_use_windows_threads();
#else
    evthread_use_pthreads();
#endif
 
    base = event_base_new(); // XXX RAII
    if (!base) {
        LogPrintf("Couldn't create an event_base: exiting\n");
        return false;
    }
 
    /* Create a new evhttp object to handle requests. */
    http = evhttp_new(base); // XXX RAII
    if (!http) {
        LogPrintf("couldn't create evhttp. Exiting.\n");
        event_base_free(base);
        return false;
    }
 
    evhttp_set_timeout(http, GetArg("-rpcservertimeout", DEFAULT_HTTP_SERVER_TIMEOUT));
    evhttp_set_max_headers_size(http, MAX_HEADERS_SIZE);
    evhttp_set_max_body_size(http, MAX_SIZE);
    evhttp_set_gencb(http, http_request_cb, NULL);
 
    if (!HTTPBindAddresses(http)) {
        LogPrintf("Unable to bind any endpoint for RPC server\n");
        evhttp_free(http);
        event_base_free(base);
        return false;
    }
 
    LogPrint(BCLog::HTTP, "Initialized HTTP server\n");
    int workQueueDepth = std::max((long)GetArg("-rpcworkqueue", DEFAULT_HTTP_WORKQUEUE), 1L);
    LogPrintf("HTTP: creating work queue of depth %d\n", workQueueDepth);
 
    workQueue = new WorkQueue<HTTPClosure>(workQueueDepth);
    eventBase = base;
    eventHTTP = http;
    return true;
}
 
bool UpdateHTTPServerLogging(bool enable) {
#if LIBEVENT_VERSION_NUMBER >= 0x02010100
    if (enable) {
        event_enable_debug_logging(EVENT_DBG_ALL);
    } else {
        event_enable_debug_logging(EVENT_DBG_NONE);
    }
    return true;
#else
    // Can't update libevent logging if version < 02010100
    return false;
#endif
}
 
std::thread threadHTTP;
std::future<bool> threadResult;
 
bool StartHTTPServer()
{
    LogPrint(BCLog::HTTP, "Starting HTTP server\n");
    int rpcThreads = std::max((long)GetArg("-rpcthreads", DEFAULT_HTTP_THREADS), 1L);
    LogPrintf("HTTP: starting %d worker threads\n", rpcThreads);
    std::packaged_task<bool(event_base*, evhttp*)> task(ThreadHTTP);
    threadResult = task.get_future();
    threadHTTP = std::thread(std::move(task), eventBase, eventHTTP);
 
    for (int i = 0; i < rpcThreads; i++) {
        std::thread rpc_worker(HTTPWorkQueueRun, workQueue);
        rpc_worker.detach();
    }
    return true;
}
 
void InterruptHTTPServer()
{
    LogPrint(BCLog::HTTP, "Interrupting HTTP server\n");
    if (eventHTTP) {
        for (evhttp_bound_socket *socket : boundSockets) {
            evhttp_del_accept_socket(eventHTTP, socket);
        }
        evhttp_set_gencb(eventHTTP, http_reject_request_cb, NULL);
    }
    if (workQueue)
        workQueue->Interrupt();
}
 
void StopHTTPServer()
{
    LogPrint(BCLog::HTTP, "Stopping HTTP server\n");
    if (workQueue) {
        LogPrint(BCLog::HTTP, "Waiting for HTTP worker threads to exit\n");
        workQueue->WaitExit();
        delete workQueue;
    }
    MilliSleep(500); // Avoid race condition while the last HTTP-thread is exiting
    if (eventBase) {
        LogPrint(BCLog::HTTP, "Waiting for HTTP event thread to exit\n");
        // Give event loop a few seconds to exit (to send back last RPC responses), then break it
        // Before this was solved with event_base_loopexit, but that didn't work as expected in
        // at least libevent 2.0.21 and always introduced a delay. In libevent
        // master that appears to be solved, so in the future that solution
        // could be used again (if desirable).
        // (see discussion in https://github.com/bitcoin/bitcoin/pull/6990)
        if (threadResult.valid() && threadResult.wait_for(std::chrono::milliseconds(2000)) == std::future_status::timeout) {
            LogPrintf("HTTP event loop did not exit within allotted time, sending loopbreak\n");
            event_base_loopbreak(eventBase);
 
        }
        threadHTTP.join();
    }
    if (eventHTTP) {
        evhttp_free(eventHTTP);
        eventHTTP = 0;
    }
    if (eventBase) {
        event_base_free(eventBase);
        eventBase = 0;
    }
    LogPrint(BCLog::HTTP, "Stopped HTTP server\n");
}
 
struct event_base* EventBase()
{
    return eventBase;
}
 
static void httpevent_callback_fn(evutil_socket_t, short, void* data)
{
    // Static handler: simply call inner handler
    HTTPEvent *self = ((HTTPEvent*)data);
    self->handler();
    if (self->deleteWhenTriggered)
        delete self;
}
 
HTTPEvent::HTTPEvent(struct event_base* base, bool deleteWhenTriggered, const std::function<void(void)>& handler):
    deleteWhenTriggered(deleteWhenTriggered), handler(handler)
{
    ev = event_new(base, -1, 0, httpevent_callback_fn, this);
    assert(ev);
}
HTTPEvent::~HTTPEvent()
{
    event_free(ev);
}
void HTTPEvent::trigger(struct timeval* tv)
{
    if (tv == NULL)
        event_active(ev, 0, 0); // immediately trigger event in main thread
    else
        evtimer_add(ev, tv); // trigger after timeval passed
}
HTTPRequest::HTTPRequest(struct evhttp_request* req) : req(req),
                                                       replySent(false)
{
}
HTTPRequest::~HTTPRequest()
{
    if (!replySent) {
        // Keep track of whether reply was sent to avoid request leaks
        LogPrintf("%s: Unhandled request\n", __func__);
        WriteReply(HTTP_INTERNAL, "Unhandled request");
    }
    // evhttpd cleans up the request, as long as a reply was sent.
}
 
std::pair<bool, std::string> HTTPRequest::GetHeader(const std::string& hdr)
{
    const struct evkeyvalq* headers = evhttp_request_get_input_headers(req);
    assert(headers);
    const char* val = evhttp_find_header(headers, hdr.c_str());
    if (val)
        return std::make_pair(true, val);
    else
        return std::make_pair(false, "");
}
 
std::string HTTPRequest::ReadBody()
{
    struct evbuffer* buf = evhttp_request_get_input_buffer(req);
    if (!buf)
        return "";
    size_t size = evbuffer_get_length(buf);
    const char* data = (const char*)evbuffer_pullup(buf, size);
    if (!data) // returns NULL in case of empty buffer
        return "";
    std::string rv(data, size);
    evbuffer_drain(buf, size);
    return rv;
}
 
void HTTPRequest::WriteHeader(const std::string& hdr, const std::string& value)
{
    struct evkeyvalq* headers = evhttp_request_get_output_headers(req);
    assert(headers);
    evhttp_add_header(headers, hdr.c_str(), value.c_str());
}
 
void HTTPRequest::WriteReply(int nStatus, const std::string& strReply)
{
    assert(!replySent && req);
    // Send event to main http thread to send reply message
    struct evbuffer* evb = evhttp_request_get_output_buffer(req);
    assert(evb);
    evbuffer_add(evb, strReply.data(), strReply.size());
    auto req_copy = req;
    HTTPEvent* ev = new HTTPEvent(eventBase, true, [req_copy, nStatus]{
        evhttp_send_reply(req_copy, nStatus, nullptr, nullptr);
        // Re-enable reading from the socket. This is the second part of the libevent
        // workaround above.
        if (event_get_version_number() >= 0x02010600 && event_get_version_number() < 0x02020001) {
            evhttp_connection* conn = evhttp_request_get_connection(req_copy);
            if (conn) {
                bufferevent* bev = evhttp_connection_get_bufferevent(conn);
                if (bev) {
                    bufferevent_enable(bev, EV_READ | EV_WRITE);
                }
            }
        }
    });
    ev->trigger(0);
    replySent = true;
    req = 0; // transferred back to main thread
}
 
CService HTTPRequest::GetPeer()
{
    evhttp_connection* con = evhttp_request_get_connection(req);
    CService peer;
    if (con) {
        // evhttp retains ownership over returned address string
        const char* address = "";
        uint16_t port = 0;
        evhttp_connection_get_peer(con, (char**)&address, &port);
        peer = LookupNumeric(address, port);
    }
    return peer;
}
 
std::string HTTPRequest::GetURI()
{
    return evhttp_request_get_uri(req);
}
 
HTTPRequest::RequestMethod HTTPRequest::GetRequestMethod()
{
    switch (evhttp_request_get_command(req)) {
    case EVHTTP_REQ_GET:
        return GET;
        break;
    case EVHTTP_REQ_POST:
        return POST;
        break;
    case EVHTTP_REQ_HEAD:
        return HEAD;
        break;
    case EVHTTP_REQ_PUT:
        return PUT;
        break;
    default:
        return UNKNOWN;
        break;
    }
}
 
void RegisterHTTPHandler(const std::string &prefix, bool exactMatch, const HTTPRequestHandler &handler)
{
    LogPrint(BCLog::HTTP, "Registering HTTP handler for %s (exactmatch %d)\n", prefix, exactMatch);
    pathHandlers.push_back(HTTPPathHandler(prefix, exactMatch, handler));
}
 
void UnregisterHTTPHandler(const std::string &prefix, bool exactMatch)
{
    std::vector<HTTPPathHandler>::iterator i = pathHandlers.begin();
    std::vector<HTTPPathHandler>::iterator iend = pathHandlers.end();
    for (; i != iend; ++i)
        if (i->prefix == prefix && i->exactMatch == exactMatch)
            break;
    if (i != iend)
    {
        LogPrint(BCLog::HTTP, "Unregistering HTTP handler for %s (exactmatch %d)\n", prefix, exactMatch);
        pathHandlers.erase(i);
    }
}