// Copyright (c) 2015 The Bitcoin Core developers // Distributed under the MIT software license, see the accompanying // file COPYING or http://www.opensource.org/licenses/mit-license.php. #include "torcontrol.h" #include "utilstrencodings.h" #include "net.h" #include "util.h" #include "crypto/hmac_sha256.h" #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include /** Default control port */ const std::string DEFAULT_TOR_CONTROL = "127.0.0.1:9051"; /** Tor cookie size (from control-spec.txt) */ static const int TOR_COOKIE_SIZE = 32; /** Size of client/server nonce for SAFECOOKIE */ static const int TOR_NONCE_SIZE = 32; /** For computing serverHash in SAFECOOKIE */ static const std::string TOR_SAFE_SERVERKEY = "Tor safe cookie authentication server-to-controller hash"; /** For computing clientHash in SAFECOOKIE */ static const std::string TOR_SAFE_CLIENTKEY = "Tor safe cookie authentication controller-to-server hash"; /** 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; /** Maximum length for lines received on TorControlConnection. * tor-control-spec.txt mentions that there is explicitly no limit defined to line length, * this is belt-and-suspenders sanity limit to prevent memory exhaustion. */ static const int MAX_LINE_LENGTH = 100000; /****** Low-level TorControlConnection ********/ /** Reply from Tor, can be single or multi-line */ class TorControlReply { public: TorControlReply() { Clear(); } int code; std::vector 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 ConnectionCB; typedef boost::function 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 successfully 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 async_handler; private: /** Callback when ready for use */ boost::function connected; /** Callback when connection lost */ boost::function 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 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; // (-|+| ) self->message.code = atoi(s.substr(0,3)); 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 { LogPrint("tor", "tor: Received unexpected sync reply %i\n", self->message.code); } } self->message.Clear(); } } // Check for size of buffer - protect against memory exhaustion with very long lines // Do this after evbuffer_readln to make sure all full lines have been // removed from the buffer. Everything left is an incomplete line. if (evbuffer_get_length(input) > MAX_LINE_LENGTH) { LogPrintf("tor: Disconnecting because MAX_LINE_LENGTH exceeded\n"); self->Disconnect(); } } void TorControlConnection::eventcb(struct bufferevent *bev, short what, void *ctx) { TorControlConnection *self = (TorControlConnection*)ctx; if (what & BEV_EVENT_CONNECTED) { LogPrint("tor", "tor: Successfully connected!\n"); self->connected(*self); } else if (what & (BEV_EVENT_EOF|BEV_EVENT_ERROR)) { if (what & BEV_EVENT_ERROR) LogPrint("tor", "tor: Error connecting to Tor control socket\n"); else LogPrint("tor", "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) { LogPrintf("tor: Error parsing socket address %s\n", target); 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) { LogPrintf("tor: Error connecting to address %s\n", target); 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 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 ParseTorReplyMapping(const std::string &s) { std::map 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(); ++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(); ++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. * Returns a pair . * If an error occurred, status will be false, otherwise status will be true and the data will be returned in string. * * @param maxsize Puts a maximum size limit on the file that is read. If the file is larger than this, truncated data * (with len > maxsize) will be returned. */ static std::pair ReadBinaryFile(const std::string &filename, size_t maxsize=std::numeric_limits::max()) { 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); if (retval.size() > maxsize) break; } 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()) { fclose(f); 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 *reconnect_ev; float reconnect_timeout; CService service; /** Cooie for SAFECOOKIE auth */ std::vector cookie; /** ClientNonce for SAFECOOKIE auth */ std::vector clientNonce; /** 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 AUTHCHALLENGE result */ void authchallenge_cb(TorControlConnection& conn, const TorControlReply& reply); /** Callback for PROTOCOLINFO result */ void protocolinfo_cb(TorControlConnection& conn, const TorControlReply& reply); /** Callback after successful connection */ void connected_cb(TorControlConnection& conn); /** Callback after connection lost or failed connection attempt */ void disconnected_cb(TorControlConnection& conn); /** Callback for reconnect timer */ static void reconnect_cb(evutil_socket_t fd, short what, void *arg); }; TorController::TorController(struct event_base* baseIn, const std::string& target): base(baseIn), target(target), conn(base), reconnect(true), reconnect_ev(0), reconnect_timeout(RECONNECT_TIMEOUT_START) { reconnect_ev = event_new(base, -1, 0, reconnect_cb, this); if (!reconnect_ev) LogPrintf("tor: Failed to create event for reconnection: out of memory?\n"); // 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 pkf = ReadBinaryFile(GetPrivateKeyFile()); if (pkf.first) { LogPrint("tor", "tor: Reading cached private key from %s\n", GetPrivateKeyFile()); private_key = pkf.second; } } TorController::~TorController() { if (reconnect_ev) { event_free(reconnect_ev); reconnect_ev = 0; } if (service.IsValid()) { RemoveLocal(service); } } void TorController::add_onion_cb(TorControlConnection& conn, const TorControlReply& reply) { if (reply.code == 250) { LogPrint("tor", "tor: ADD_ONION successful\n"); BOOST_FOREACH(const std::string &s, reply.lines) { std::map m = ParseTorReplyMapping(s); std::map::iterator i; if ((i = m.find("ServiceID")) != m.end()) service_id = i->second; if ((i = m.find("PrivateKey")) != m.end()) private_key = i->second; } service = CService(service_id+".onion", GetListenPort()); LogPrintf("tor: Got service ID %s, advertising service %s\n", service_id, service.ToString()); if (WriteBinaryFile(GetPrivateKeyFile(), private_key)) { LogPrint("tor", "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 if (reply.code == 510) { // 510 Unrecognized command LogPrintf("tor: Add onion failed with unrecognized command (You probably need to upgrade Tor)\n"); } else { LogPrintf("tor: Add onion failed; error code %d\n", reply.code); } } void TorController::auth_cb(TorControlConnection& conn, const TorControlReply& reply) { if (reply.code == 250) { LogPrint("tor", "tor: Authentication successful\n"); // Now that we know Tor is running setup the proxy for onion addresses // if -onion isn't set to something else. if (GetArg("-onion", "") == "") { proxyType addrOnion = proxyType(CService("127.0.0.1", 9050), true); SetProxy(NET_TOR, addrOnion); SetLimited(NET_TOR, false); } // Finally - now create the service if (private_key.empty()) // No private key, generate one private_key = "NEW:RSA1024"; // Explicitly request RSA1024 - see issue #9214 // 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"); } } /** Compute Tor SAFECOOKIE response. * * ServerHash is computed as: * HMAC-SHA256("Tor safe cookie authentication server-to-controller hash", * CookieString | ClientNonce | ServerNonce) * (with the HMAC key as its first argument) * * After a controller sends a successful AUTHCHALLENGE command, the * next command sent on the connection must be an AUTHENTICATE command, * and the only authentication string which that AUTHENTICATE command * will accept is: * * HMAC-SHA256("Tor safe cookie authentication controller-to-server hash", * CookieString | ClientNonce | ServerNonce) * */ static std::vector ComputeResponse(const std::string &key, const std::vector &cookie, const std::vector &clientNonce, const std::vector &serverNonce) { CHMAC_SHA256 computeHash((const uint8_t*)key.data(), key.size()); std::vector computedHash(CHMAC_SHA256::OUTPUT_SIZE, 0); computeHash.Write(begin_ptr(cookie), cookie.size()); computeHash.Write(begin_ptr(clientNonce), clientNonce.size()); computeHash.Write(begin_ptr(serverNonce), serverNonce.size()); computeHash.Finalize(begin_ptr(computedHash)); return computedHash; } void TorController::authchallenge_cb(TorControlConnection& conn, const TorControlReply& reply) { if (reply.code == 250) { LogPrint("tor", "tor: SAFECOOKIE authentication challenge successful\n"); std::pair l = SplitTorReplyLine(reply.lines[0]); if (l.first == "AUTHCHALLENGE") { std::map m = ParseTorReplyMapping(l.second); std::vector serverHash = ParseHex(m["SERVERHASH"]); std::vector serverNonce = ParseHex(m["SERVERNONCE"]); LogPrint("tor", "tor: AUTHCHALLENGE ServerHash %s ServerNonce %s\n", HexStr(serverHash), HexStr(serverNonce)); if (serverNonce.size() != 32) { LogPrintf("tor: ServerNonce is not 32 bytes, as required by spec\n"); return; } std::vector computedServerHash = ComputeResponse(TOR_SAFE_SERVERKEY, cookie, clientNonce, serverNonce); if (computedServerHash != serverHash) { LogPrintf("tor: ServerHash %s does not match expected ServerHash %s\n", HexStr(serverHash), HexStr(computedServerHash)); return; } std::vector computedClientHash = ComputeResponse(TOR_SAFE_CLIENTKEY, cookie, clientNonce, serverNonce); conn.Command("AUTHENTICATE " + HexStr(computedClientHash), boost::bind(&TorController::auth_cb, this, _1, _2)); } else { LogPrintf("tor: Invalid reply to AUTHCHALLENGE\n"); } } else { LogPrintf("tor: SAFECOOKIE authentication challenge failed\n"); } } void TorController::protocolinfo_cb(TorControlConnection& conn, const TorControlReply& reply) { if (reply.code == 250) { std::set 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 l = SplitTorReplyLine(s); if (l.first == "AUTH") { std::map m = ParseTorReplyMapping(l.second); std::map::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 m = ParseTorReplyMapping(l.second); std::map::iterator i; if ((i = m.find("Tor")) != m.end()) { LogPrint("tor", "tor: Connected to Tor version %s\n", i->second); } } } BOOST_FOREACH(const std::string &s, methods) { LogPrint("tor", "tor: Supported authentication method: %s\n", s); } // Prefer NULL, otherwise SAFECOOKIE. If a password is provided, use HASHEDPASSWORD /* Authentication: * cookie: hex-encoded ~/.tor/control_auth_cookie * password: "password" */ std::string torpassword = GetArg("-torpassword", ""); if (!torpassword.empty()) { if (methods.count("HASHEDPASSWORD")) { LogPrint("tor", "tor: Using HASHEDPASSWORD authentication\n"); boost::replace_all(torpassword, "\"", "\\\""); conn.Command("AUTHENTICATE \"" + torpassword + "\"", boost::bind(&TorController::auth_cb, this, _1, _2)); } else { LogPrintf("tor: Password provided with -torpassword, but HASHEDPASSWORD authentication is not available\n"); } } else if (methods.count("NULL")) { LogPrint("tor", "tor: Using NULL authentication\n"); conn.Command("AUTHENTICATE", boost::bind(&TorController::auth_cb, this, _1, _2)); } else if (methods.count("SAFECOOKIE")) { // Cookie: hexdump -e '32/1 "%02x""\n"' ~/.tor/control_auth_cookie LogPrint("tor", "tor: Using SAFECOOKIE authentication, reading cookie authentication from %s\n", cookiefile); std::pair status_cookie = ReadBinaryFile(cookiefile, TOR_COOKIE_SIZE); if (status_cookie.first && status_cookie.second.size() == TOR_COOKIE_SIZE) { // conn.Command("AUTHENTICATE " + HexStr(status_cookie.second), boost::bind(&TorController::auth_cb, this, _1, _2)); cookie = std::vector(status_cookie.second.begin(), status_cookie.second.end()); clientNonce = std::vector(TOR_NONCE_SIZE, 0); GetRandBytes(&clientNonce[0], TOR_NONCE_SIZE); conn.Command("AUTHCHALLENGE SAFECOOKIE " + HexStr(clientNonce), boost::bind(&TorController::authchallenge_cb, this, _1, _2)); } else { if (status_cookie.first) { LogPrintf("tor: Authentication cookie %s is not exactly %i bytes, as is required by the spec\n", cookiefile, TOR_COOKIE_SIZE); } else { LogPrintf("tor: Authentication cookie %s could not be opened (check permissions)\n", cookiefile); } } } else if (methods.count("HASHEDPASSWORD")) { LogPrintf("tor: The only supported authentication mechanism left is password, but no password provided with -torpassword\n"); } else { 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) { // Stop advertising service when disconnected if (service.IsValid()) RemoveLocal(service); service = CService(); if (!reconnect) return; LogPrint("tor", "tor: Not connected to 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)); if (reconnect_ev) 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::reconnect_cb(evutil_socket_t fd, short what, void *arg) { TorController *self = (TorController*)arg; self->Reconnect(); } /****** Thread ********/ struct event_base *base; boost::thread torControlThread; static void TorControlThread() { TorController ctrl(base, GetArg("-torcontrol", DEFAULT_TOR_CONTROL)); event_base_dispatch(base); } void StartTorControl(boost::thread_group& threadGroup, CScheduler& scheduler) { assert(!base); #ifdef WIN32 evthread_use_windows_threads(); #else evthread_use_pthreads(); #endif base = event_base_new(); if (!base) { LogPrintf("tor: Unable to create event_base\n"); return; } torControlThread = boost::thread(boost::bind(&TraceThread, "torcontrol", &TorControlThread)); } void InterruptTorControl() { if (base) { LogPrintf("tor: Thread interrupt\n"); event_base_loopbreak(base); } } void StopTorControl() { if (base) { torControlThread.join(); event_base_free(base); base = 0; } }