net: Automatically create hidden service, listen on Tor

Starting with Tor version 0.2.7.1 it is possible, through Tor's control socket
API, to create and destroy 'ephemeral' hidden services programmatically.
https://stem.torproject.org/api/control.html#stem.control.Controller.create_ephemeral_hidden_service

This means that if Tor is running (and proper authorization is available),
bitcoin automatically creates a hidden service to listen on, without user
manual configuration. This will positively affect the number of available
.onion nodes.

- When the node is started, connect to Tor through control socket
- Send `ADD_ONION` command
- First time:
    - Make it create a hidden service key
    - Save the key in the data directory for later usage
- Make it redirect port 8333 to the local port 8333 (or whatever port we're listening on).
- Keep control socket connection open for as long node is running. The hidden service will
  (by default) automatically go away when the connection is closed.

1 files changed, 573 insertions, 0 deletions

diff --git a/src/torcontrol.cpp b/src/torcontrol.cpp
new file mode 100644
index 0000000000..bb72315c8e
--- /dev/null
+++ b/src/torcontrol.cpp
@@ -0,0 +1,573 @@
+#include "torcontrol.h"
+#include "utilstrencodings.h"
+#include "net.h"
+#include "util.h"
+#include "init.h" // Just for ShutdownRequested
+
+#include <vector>
+#include <deque>
+#include <set>
+#include <stdlib.h>
+
+#include <boost/function.hpp>
+#include <boost/bind.hpp>
+#include <boost/signals2/signal.hpp>
+#include <boost/foreach.hpp>
+#include <boost/algorithm/string/predicate.hpp>
+#include <boost/algorithm/string/split.hpp>
+#include <boost/algorithm/string/classification.hpp>
+
+#include <event2/bufferevent.h>
+#include <event2/buffer.h>
+#include <event2/util.h>
+#include <event2/event.h>
+
+const std::string DEFAULT_TOR_CONTROL = "127.0.0.1:9051";
+
+/****** Low-level TorControlConnection ********/
+
+/** Reply from Tor, can be single or multi-line */
+class TorControlReply
+{
+public:
+    TorControlReply() { Clear(); }
+
+    int code;
+    std::vector<std::string> lines;
+
+    void Clear()
+    {
+        code = 0;
+        lines.clear();
+    }
+};
+
+/** Low-level handling for Tor control connection.
+ * Speaks the SMTP-like protocol as defined in torspec/control-spec.txt
+ */
+class TorControlConnection
+{
+public:
+    typedef boost::function<void(TorControlConnection&)> ConnectionCB;
+    typedef boost::function<void(TorControlConnection &,const TorControlReply &)> ReplyHandlerCB;
+
+    /** Create a new TorControlConnection.
+     */
+    TorControlConnection(struct event_base *base);
+    ~TorControlConnection();
+
+    /**
+     * Connect to a Tor control port.
+     * target is address of the form host:port.
+     * connected is the handler that is called when connection is succesfully established.
+     * disconnected is a handler that is called when the connection is broken.
+     * Return true on success.
+     */
+    bool Connect(const std::string &target, const ConnectionCB& connected, const ConnectionCB& disconnected);
+
+    /**
+     * Disconnect from Tor control port.
+     */
+    bool Disconnect();
+
+    /** Send a command, register a handler for the reply.
+     * A trailing CRLF is automatically added.
+     * Return true on success.
+     */
+    bool Command(const std::string &cmd, const ReplyHandlerCB& reply_handler);
+
+    /** Response handlers for async replies */
+    boost::signals2::signal<void(TorControlConnection &,const TorControlReply &)> async_handler;
+private:
+    /** Callback when ready for use */
+    boost::function<void(TorControlConnection&)> connected;
+    /** Callback when connection lost */
+    boost::function<void(TorControlConnection&)> disconnected;
+    /** Libevent event base */
+    struct event_base *base;
+    /** Connection to control socket */
+    struct bufferevent *b_conn;
+    /** Message being received */
+    TorControlReply message;
+    /** Response handlers */
+    std::deque<ReplyHandlerCB> reply_handlers;
+
+    /** Libevent handlers: internal */
+    static void readcb(struct bufferevent *bev, void *ctx);
+    static void eventcb(struct bufferevent *bev, short what, void *ctx);
+};
+
+TorControlConnection::TorControlConnection(struct event_base *base):
+    base(base), b_conn(0)
+{
+}
+
+TorControlConnection::~TorControlConnection()
+{
+    if (b_conn)
+        bufferevent_free(b_conn);
+}
+
+void TorControlConnection::readcb(struct bufferevent *bev, void *ctx)
+{
+    TorControlConnection *self = (TorControlConnection*)ctx;
+    struct evbuffer *input = bufferevent_get_input(bev);
+    size_t n_read_out = 0;
+    char *line;
+    assert(input);
+    //  If there is not a whole line to read, evbuffer_readln returns NULL
+    while((line = evbuffer_readln(input, &n_read_out, EVBUFFER_EOL_CRLF)) != NULL)
+    {
+        std::string s(line, n_read_out);
+        free(line);
+        if (s.size() < 4) // Short line
+            continue;
+        // <status>(-|+| )<data><CRLF>
+        self->message.code = atoi(s.substr(0,3).c_str());
+        self->message.lines.push_back(s.substr(4));
+        char ch = s[3]; // '-','+' or ' '
+        if (ch == ' ') {
+            // Final line, dispatch reply and clean up
+            if (self->message.code >= 600) {
+                // Dispatch async notifications to async handler
+                // Synchronous and asynchronous messages are never interleaved
+                self->async_handler(*self, self->message);
+            } else {
+                if (!self->reply_handlers.empty()) {
+                    // Invoke reply handler with message
+                    self->reply_handlers.front()(*self, self->message);
+                    self->reply_handlers.pop_front();
+                } else {
+                    LogPrintf("[tor] Received unexpected sync reply %i\n", self->message.code);
+                }
+            }
+            self->message.Clear();
+        }
+    }
+}
+
+void TorControlConnection::eventcb(struct bufferevent *bev, short what, void *ctx)
+{
+    TorControlConnection *self = (TorControlConnection*)ctx;
+    if (what & BEV_EVENT_CONNECTED) {
+        LogPrintf("[tor] Succesfully connected!\n");
+        self->connected(*self);
+    } else if (what & (BEV_EVENT_EOF|BEV_EVENT_ERROR)) {
+        if (what & BEV_EVENT_ERROR)
+            LogPrintf("[tor] Error connecting to Tor control socket\n");
+        else
+            LogPrintf("[tor] End of stream\n");
+        self->Disconnect();
+        self->disconnected(*self);
+    }
+}
+
+bool TorControlConnection::Connect(const std::string &target, const ConnectionCB& connected, const ConnectionCB& disconnected)
+{
+    if (b_conn)
+        Disconnect();
+    // Parse target address:port
+    struct sockaddr_storage connect_to_addr;
+    int connect_to_addrlen = sizeof(connect_to_addr);
+    if (evutil_parse_sockaddr_port(target.c_str(),
+        (struct sockaddr*)&connect_to_addr, &connect_to_addrlen)<0) {
+        perror("evutil_parse_sockaddr_port\n");
+        return false;
+    }
+
+    // Create a new socket, set up callbacks and enable notification bits
+    b_conn = bufferevent_socket_new(base, -1, BEV_OPT_CLOSE_ON_FREE);
+    if (!b_conn)
+        return false;
+    bufferevent_setcb(b_conn, TorControlConnection::readcb, NULL, TorControlConnection::eventcb, this);
+    bufferevent_enable(b_conn, EV_READ|EV_WRITE);
+    this->connected = connected;
+    this->disconnected = disconnected;
+
+    // Finally, connect to target
+    if (bufferevent_socket_connect(b_conn, (struct sockaddr*)&connect_to_addr, connect_to_addrlen) < 0) {
+        perror("bufferevent_socket_connect");
+        return false;
+    }
+    return true;
+}
+
+bool TorControlConnection::Disconnect()
+{
+    if (b_conn)
+        bufferevent_free(b_conn);
+    b_conn = 0;
+    return true;
+}
+
+bool TorControlConnection::Command(const std::string &cmd, const ReplyHandlerCB& reply_handler)
+{
+    if (!b_conn)
+        return false;
+    struct evbuffer *buf = bufferevent_get_output(b_conn);
+    if (!buf)
+        return false;
+    evbuffer_add(buf, cmd.data(), cmd.size());
+    evbuffer_add(buf, "\r\n", 2);
+    reply_handlers.push_back(reply_handler);
+    return true;
+}
+
+/****** General parsing utilities ********/
+
+/* Split reply line in the form 'AUTH METHODS=...' into a type
+ * 'AUTH' and arguments 'METHODS=...'.
+ */
+static std::pair<std::string,std::string> SplitTorReplyLine(const std::string &s)
+{
+    size_t ptr=0;
+    std::string type;
+    while (ptr < s.size() && s[ptr] != ' ') {
+        type.push_back(s[ptr]);
+        ++ptr;
+    }
+    if (ptr < s.size())
+        ++ptr; // skip ' '
+    return make_pair(type, s.substr(ptr));
+}
+
+/** Parse reply arguments in the form 'METHODS=COOKIE,SAFECOOKIE COOKIEFILE=".../control_auth_cookie"'.
+ */
+static std::map<std::string,std::string> ParseTorReplyMapping(const std::string &s)
+{
+    std::map<std::string,std::string> mapping;
+    size_t ptr=0;
+    while (ptr < s.size()) {
+        std::string key, value;
+        while (ptr < s.size() && s[ptr] != '=') {
+            key.push_back(s[ptr]);
+            ++ptr;
+        }
+        if (ptr == s.size()) // unexpected end of line
+            return std::map<std::string,std::string>();
+        ++ptr; // skip '='
+        if (ptr < s.size() && s[ptr] == '"') { // Quoted string
+            ++ptr; // skip '='
+            bool escape_next = false;
+            while (ptr < s.size() && (!escape_next && s[ptr] != '"')) {
+                escape_next = (s[ptr] == '\\');
+                value.push_back(s[ptr]);
+                ++ptr;
+            }
+            if (ptr == s.size()) // unexpected end of line
+                return std::map<std::string,std::string>();
+            ++ptr; // skip closing '"'
+            /* TODO: unescape value - according to the spec this depends on the
+             * context, some strings use C-LogPrintf style escape codes, some
+             * don't. So may be better handled at the call site.
+             */
+        } else { // Unquoted value. Note that values can contain '=' at will, just no spaces
+            while (ptr < s.size() && s[ptr] != ' ') {
+                value.push_back(s[ptr]);
+                ++ptr;
+            }
+        }
+        if (ptr < s.size() && s[ptr] == ' ')
+            ++ptr; // skip ' ' after key=value
+        mapping[key] = value;
+    }
+    return mapping;
+}
+
+/** Read full contents of a file and return them in a std::string. */
+static std::pair<bool,std::string> ReadBinaryFile(const std::string &filename)
+{
+    FILE *f = fopen(filename.c_str(), "rb");
+    if (f == NULL)
+        return std::make_pair(false,"");
+    std::string retval;
+    char buffer[128];
+    size_t n;
+    while ((n=fread(buffer, 1, sizeof(buffer), f)) > 0)
+        retval.append(buffer, buffer+n);
+    fclose(f);
+    return std::make_pair(true,retval);
+}
+
+/** Write contents of std::string to a file.
+ * @return true on success.
+ */
+static bool WriteBinaryFile(const std::string &filename, const std::string &data)
+{
+    FILE *f = fopen(filename.c_str(), "wb");
+    if (f == NULL)
+        return false;
+    if (fwrite(data.data(), 1, data.size(), f) != data.size())
+        return false;
+    fclose(f);
+    return true;
+}
+
+/****** Bitcoin specific TorController implementation ********/
+
+/** Controller that connects to Tor control socket, authenticate, then create
+ * and maintain a ephemeral hidden service.
+ */
+class TorController
+{
+public:
+    TorController(struct event_base* base, const std::string& target);
+    ~TorController();
+
+    /** Get name fo file to store private key in */
+    std::string GetPrivateKeyFile();
+
+    /** Reconnect, after getting disconnected */
+    void Reconnect();
+private:
+    struct event_base* base;
+    std::string target;
+    TorControlConnection conn;
+    std::string private_key;
+    std::string service_id;
+    bool reconnect;
+    struct event *shutdown_poll_ev;
+    struct event *reconnect_ev;
+    float reconnect_timeout;
+
+    /** Callback for ADD_ONION result */
+    void add_onion_cb(TorControlConnection& conn, const TorControlReply& reply);
+    /** Callback for AUTHENTICATE result */
+    void auth_cb(TorControlConnection& conn, const TorControlReply& reply);
+    /** Callback for PROTOCOLINFO result */
+    void protocolinfo_cb(TorControlConnection& conn, const TorControlReply& reply);
+    /** Callback after succesful connection */
+    void connected_cb(TorControlConnection& conn);
+    /** Callback after connection lost or failed connection attempt */
+    void disconnected_cb(TorControlConnection& conn);
+
+    /** Callback for shutdown poll timer */
+    static void shutdown_poll_cb(evutil_socket_t fd, short what, void *arg);
+    /** Callback for reconnect timer */
+    static void reconnect_cb(evutil_socket_t fd, short what, void *arg);
+};
+
+/** Exponential backoff configuration - initial timeout in seconds */
+static const float RECONNECT_TIMEOUT_START = 1.0;
+/** Exponential backoff configuration - growth factor */
+static const float RECONNECT_TIMEOUT_EXP = 1.5;
+
+TorController::TorController(struct event_base* base, const std::string& target):
+    base(base),
+    target(target), conn(base), reconnect(true), shutdown_poll_ev(0), reconnect_ev(0),
+    reconnect_timeout(RECONNECT_TIMEOUT_START)
+{
+    // Start connection attempts immediately
+    if (!conn.Connect(target, boost::bind(&TorController::connected_cb, this, _1),
+         boost::bind(&TorController::disconnected_cb, this, _1) )) {
+        LogPrintf("[tor] Initiating connection to Tor control port %s failed\n", target);
+    }
+    // Read service private key if cached
+    std::pair<bool,std::string> pkf = ReadBinaryFile(GetPrivateKeyFile());
+    if (pkf.first) {
+        LogPrintf("[tor] Reading cached private key from %s\n", GetPrivateKeyFile());
+        private_key = pkf.second;
+    }
+    // Periodic timer event to poll for shutdown
+    // The same 200ms as in bitcoind. This is not the nicest solution, but we cannot exactly use
+    // boost::interrupt here.
+    struct timeval time;
+    time.tv_usec = 200000;
+    time.tv_sec = 0;
+    shutdown_poll_ev = event_new(base, -1, EV_PERSIST, shutdown_poll_cb, this);
+    event_add(shutdown_poll_ev, &time);
+}
+
+TorController::~TorController()
+{
+    if (shutdown_poll_ev)
+        event_del(shutdown_poll_ev);
+    if (reconnect_ev)
+        event_del(reconnect_ev);
+}
+
+void TorController::add_onion_cb(TorControlConnection& conn, const TorControlReply& reply)
+{
+    if (reply.code == 250) {
+        LogPrintf("[tor] ADD_ONION succesful\n");
+        BOOST_FOREACH(const std::string &s, reply.lines) {
+            std::map<std::string,std::string> m = ParseTorReplyMapping(s);
+            std::map<std::string,std::string>::iterator i;
+            if ((i = m.find("ServiceID")) != m.end())
+                service_id = i->second;
+            if ((i = m.find("PrivateKey")) != m.end())
+                private_key = i->second;
+        }
+
+        CService service(service_id+".onion", GetListenPort(), false);
+        LogPrintf("[tor] Got service ID %s, advertizing service %s\n", service_id, service.ToString());
+        if (WriteBinaryFile(GetPrivateKeyFile(), private_key)) {
+            LogPrintf("[tor] Cached service private key to %s\n", GetPrivateKeyFile());
+        } else {
+            LogPrintf("[tor] Error writing service private key to %s\n", GetPrivateKeyFile());
+        }
+        AddLocal(service, LOCAL_MANUAL);
+        // ... onion requested - keep connection open
+    } else {
+        LogPrintf("[tor] Add onion failed\n");
+    }
+}
+
+void TorController::auth_cb(TorControlConnection& conn, const TorControlReply& reply)
+{
+    if (reply.code == 250) {
+        LogPrintf("[tor] Authentication succesful\n");
+        // Finally - now create the service
+        if (private_key.empty()) // No private key, generate one
+            private_key = "NEW:BEST";
+        // Request hidden service, redirect port.
+        // Note that the 'virtual' port doesn't have to be the same as our internal port, but this is just a convenient
+        // choice.  TODO; refactor the shutdown sequence some day.
+        conn.Command(strprintf("ADD_ONION %s Port=%i,127.0.0.1:%i", private_key, GetListenPort(), GetListenPort()),
+            boost::bind(&TorController::add_onion_cb, this, _1, _2));
+    } else {
+        LogPrintf("[tor] Authentication failed\n");
+    }
+}
+
+void TorController::protocolinfo_cb(TorControlConnection& conn, const TorControlReply& reply)
+{
+    if (reply.code == 250) {
+        std::set<std::string> methods;
+        std::string cookiefile;
+        /*
+         * 250-AUTH METHODS=COOKIE,SAFECOOKIE COOKIEFILE="/home/x/.tor/control_auth_cookie"
+         * 250-AUTH METHODS=NULL
+         * 250-AUTH METHODS=HASHEDPASSWORD
+         */
+        BOOST_FOREACH(const std::string &s, reply.lines) {
+            std::pair<std::string,std::string> l = SplitTorReplyLine(s);
+            if (l.first == "AUTH") {
+                std::map<std::string,std::string> m = ParseTorReplyMapping(l.second);
+                std::map<std::string,std::string>::iterator i;
+                if ((i = m.find("METHODS")) != m.end())
+                    boost::split(methods, i->second, boost::is_any_of(","));
+                if ((i = m.find("COOKIEFILE")) != m.end())
+                    cookiefile = i->second;
+            } else if (l.first == "VERSION") {
+                std::map<std::string,std::string> m = ParseTorReplyMapping(l.second);
+                std::map<std::string,std::string>::iterator i;
+                if ((i = m.find("Tor")) != m.end()) {
+                    LogPrintf("[tor] Connected to Tor version %s\n", i->second);
+                }
+            }
+        }
+        BOOST_FOREACH(const std::string &s, methods) {
+            LogPrintf("[tor] Supported authentication method: %s\n", s);
+        }
+        // Prefer NULL, otherwise COOKIE. If a password is provided, use HASHEDPASSWORD
+        // We do not support SAFECOOKIE
+        /* Authentication:
+         *   cookie:   hex-encoded ~/.tor/control_auth_cookie
+         *   password: "password"
+         */
+        if (methods.count("NULL")) {
+            LogPrintf("[tor] Using NULL authentication\n");
+            conn.Command("AUTHENTICATE", boost::bind(&TorController::auth_cb, this, _1, _2));
+        } else if (methods.count("COOKIE")) {
+            // Cookie: hexdump -e '32/1 "%02x""\n"'  ~/.tor/control_auth_cookie
+            LogPrintf("[tor] Using COOKIE authentication, reading cookie authentication from %s\n", cookiefile);
+            std::string cookie = ReadBinaryFile(cookiefile).second;
+            if (!cookie.empty()) {
+                conn.Command("AUTHENTICATE " + HexStr(cookie), boost::bind(&TorController::auth_cb, this, _1, _2));
+            } else {
+                LogPrintf("[tor] Authentication cookie not found\n");
+            }
+        } else {
+            /* TODO HASHEDPASSWORD w/ manual auth */
+            LogPrintf("[tor] No supported authentication method\n");
+        }
+    } else {
+        LogPrintf("[tor] Requesting protocol info failed\n");
+    }
+}
+
+void TorController::connected_cb(TorControlConnection& conn)
+{
+    reconnect_timeout = RECONNECT_TIMEOUT_START;
+    // First send a PROTOCOLINFO command to figure out what authentication is expected
+    if (!conn.Command("PROTOCOLINFO 1", boost::bind(&TorController::protocolinfo_cb, this, _1, _2)))
+        LogPrintf("[tor] Error sending initial protocolinfo command\n");
+}
+
+void TorController::disconnected_cb(TorControlConnection& conn)
+{
+    if (!reconnect)
+        return;
+    LogPrintf("[tor] Disconnected from Tor control port %s, trying to reconnect\n", target);
+    // Single-shot timer for reconnect. Use exponential backoff.
+    struct timeval time = MillisToTimeval(int64_t(reconnect_timeout * 1000.0));
+    reconnect_ev = event_new(base, -1, 0, reconnect_cb, this);
+    event_add(reconnect_ev, &time);
+    reconnect_timeout *= RECONNECT_TIMEOUT_EXP;
+}
+
+void TorController::Reconnect()
+{
+    /* Try to reconnect and reestablish if we get booted - for example, Tor
+     * may be restarting.
+     */
+    if (!conn.Connect(target, boost::bind(&TorController::connected_cb, this, _1),
+         boost::bind(&TorController::disconnected_cb, this, _1) )) {
+        LogPrintf("[tor] Re-initiating connection to Tor control port %s failed\n", target);
+    }
+}
+
+std::string TorController::GetPrivateKeyFile()
+{
+    return (GetDataDir() / "onion_private_key").string();
+}
+
+void TorController::shutdown_poll_cb(evutil_socket_t fd, short what, void *arg)
+{
+    TorController *self = (TorController*)arg;
+    if (ShutdownRequested()) {
+        // Shutdown was requested. Stop timers, and request control connection to terminate
+        LogPrintf("[tor] Thread interrupt\n");
+        if (self->shutdown_poll_ev)
+            event_del(self->shutdown_poll_ev);
+        self->shutdown_poll_ev = 0;
+        if (self->reconnect_ev)
+            event_del(self->reconnect_ev);
+        self->reconnect_ev = 0;
+        self->reconnect = false;
+        self->conn.Disconnect();
+    }
+}
+
+void TorController::reconnect_cb(evutil_socket_t fd, short what, void *arg)
+{
+    TorController *self = (TorController*)arg;
+    self->Reconnect();
+}
+
+/****** Thread ********/
+
+static void TorControlThread()
+{
+    struct event_base *base = event_base_new();
+    if (!base) {
+        LogPrintf("[tor] Unable to create event_base_new");
+        return;
+    }
+    TorController ctrl(base, GetArg("-torcontrol", DEFAULT_TOR_CONTROL));
+
+    event_base_dispatch(base);
+    event_base_free(base);
+}
+
+void StartTorControl(boost::thread_group& threadGroup, CScheduler& scheduler)
+{
+    threadGroup.create_thread(boost::bind(&TraceThread<void (*)()>, "torcontrol", &TorControlThread));
+}
+
+void StopTorControl()
+{
+    /* Nothing to do actually. Everything is cleaned up when thread exits */
+}
+