Line data Source code
1 : // Copyright (c) 2020-2021 The Bitcoin Core developers
2 : // Distributed under the MIT software license, see the accompanying
3 : // file COPYING or http://www.opensource.org/licenses/mit-license.php.
4 :
5 : #include <chainparams.h>
6 : #include <compat/compat.h>
7 : #include <compat/endian.h>
8 : #include <crypto/sha256.h>
9 : #include <fs.h>
10 : #include <i2p.h>
11 : #include <logging.h>
12 : #include <netaddress.h>
13 : #include <netbase.h>
14 : #include <random.h>
15 : #include <sync.h>
16 : #include <tinyformat.h>
17 : #include <util/readwritefile.h>
18 : #include <util/sock.h>
19 : #include <util/spanparsing.h>
20 : #include <util/strencodings.h>
21 : #include <util/system.h>
22 : #include <util/threadinterrupt.h>
23 :
24 : #include <chrono>
25 : #include <memory>
26 : #include <stdexcept>
27 : #include <string>
28 :
29 : namespace i2p {
30 :
31 : /**
32 : * Swap Standard Base64 <-> I2P Base64.
33 : * Standard Base64 uses `+` and `/` as last two characters of its alphabet.
34 : * I2P Base64 uses `-` and `~` respectively.
35 : * So it is easy to detect in which one is the input and convert to the other.
36 : * @param[in] from Input to convert.
37 : * @return converted `from`
38 : */
39 16 : static std::string SwapBase64(const std::string& from)
40 : {
41 16 : std::string to;
42 16 : to.resize(from.size());
43 7323 : for (size_t i = 0; i < from.size(); ++i) {
44 7307 : switch (from[i]) {
45 : case '-':
46 8 : to[i] = '+';
47 8 : break;
48 : case '~':
49 22 : to[i] = '/';
50 22 : break;
51 : case '+':
52 40 : to[i] = '-';
53 40 : break;
54 : case '/':
55 110 : to[i] = '~';
56 110 : break;
57 : default:
58 7127 : to[i] = from[i];
59 7127 : break;
60 : }
61 7307 : }
62 16 : return to;
63 16 : }
64 :
65 : /**
66 : * Decode an I2P-style Base64 string.
67 : * @param[in] i2p_b64 I2P-style Base64 string.
68 : * @return decoded `i2p_b64`
69 : * @throw std::runtime_error if decoding fails
70 : */
71 6 : static Binary DecodeI2PBase64(const std::string& i2p_b64)
72 : {
73 6 : const std::string& std_b64 = SwapBase64(i2p_b64);
74 6 : auto decoded = DecodeBase64(std_b64);
75 6 : if (!decoded) {
76 5 : throw std::runtime_error(strprintf("Cannot decode Base64: \"%s\"", i2p_b64));
77 : }
78 1 : return std::move(*decoded);
79 11 : }
80 :
81 : /**
82 : * Derive the .b32.i2p address of an I2P destination (binary).
83 : * @param[in] dest I2P destination.
84 : * @return the address that corresponds to `dest`
85 : * @throw std::runtime_error if conversion fails
86 : */
87 5 : static CNetAddr DestBinToAddr(const Binary& dest)
88 : {
89 5 : CSHA256 hasher;
90 5 : hasher.Write(dest.data(), dest.size());
91 : unsigned char hash[CSHA256::OUTPUT_SIZE];
92 5 : hasher.Finalize(hash);
93 :
94 5 : CNetAddr addr;
95 5 : const std::string addr_str = EncodeBase32(hash, false) + ".b32.i2p";
96 5 : if (!addr.SetSpecial(addr_str)) {
97 0 : throw std::runtime_error(strprintf("Cannot parse I2P address: \"%s\"", addr_str));
98 : }
99 :
100 5 : return addr;
101 5 : }
102 :
103 : /**
104 : * Derive the .b32.i2p address of an I2P destination (I2P-style Base64).
105 : * @param[in] dest I2P destination.
106 : * @return the address that corresponds to `dest`
107 : * @throw std::runtime_error if conversion fails
108 : */
109 5 : static CNetAddr DestB64ToAddr(const std::string& dest)
110 : {
111 5 : const Binary& decoded = DecodeI2PBase64(dest);
112 5 : return DestBinToAddr(decoded);
113 5 : }
114 :
115 : namespace sam {
116 :
117 14 : Session::Session(const fs::path& private_key_file,
118 : const Proxy& control_host,
119 : CThreadInterrupt* interrupt)
120 7 : : m_private_key_file{private_key_file},
121 7 : m_control_host{control_host},
122 7 : m_interrupt{interrupt},
123 7 : m_transient{false}
124 7 : {
125 14 : }
126 :
127 0 : Session::Session(const Proxy& control_host, CThreadInterrupt* interrupt)
128 0 : : m_control_host{control_host},
129 0 : m_interrupt{interrupt},
130 0 : m_transient{true}
131 0 : {
132 0 : }
133 :
134 14 : Session::~Session()
135 7 : {
136 7 : LOCK(m_mutex);
137 7 : Disconnect();
138 14 : }
139 :
140 5 : bool Session::Listen(Connection& conn)
141 : {
142 : try {
143 5 : LOCK(m_mutex);
144 5 : CreateIfNotCreatedAlready();
145 5 : conn.me = m_my_addr;
146 5 : conn.sock = StreamAccept();
147 5 : return true;
148 5 : } catch (const std::runtime_error& e) {
149 0 : LogPrintLevel(BCLog::I2P, BCLog::Level::Error, "Couldn't listen: %s\n", e.what());
150 0 : CheckControlSock();
151 0 : }
152 0 : return false;
153 5 : }
154 :
155 5 : bool Session::Accept(Connection& conn)
156 : {
157 5 : AssertLockNotHeld(m_mutex);
158 :
159 5 : std::string errmsg;
160 5 : bool disconnect{false};
161 :
162 5 : while (!*m_interrupt) {
163 : Sock::Event occurred;
164 5 : if (!conn.sock->Wait(MAX_WAIT_FOR_IO, Sock::RECV, SocketEventsParams{::g_socket_events_mode}, &occurred)) {
165 0 : errmsg = "wait on socket failed";
166 0 : break;
167 : }
168 :
169 5 : if (occurred == 0) {
170 : // Timeout, no incoming connections or errors within MAX_WAIT_FOR_IO.
171 0 : continue;
172 : }
173 :
174 5 : std::string peer_dest;
175 : try {
176 5 : peer_dest = conn.sock->RecvUntilTerminator('\n', MAX_WAIT_FOR_IO, *m_interrupt, MAX_MSG_SIZE);
177 5 : } catch (const std::runtime_error& e) {
178 0 : errmsg = e.what();
179 : break;
180 0 : }
181 :
182 5 : CNetAddr peer_addr;
183 : try {
184 5 : peer_addr = DestB64ToAddr(peer_dest);
185 5 : } catch (const std::runtime_error& e) {
186 : // The I2P router is expected to send the Base64 of the connecting peer,
187 : // but it may happen that something like this is sent instead:
188 : // STREAM STATUS RESULT=I2P_ERROR MESSAGE="Session was closed"
189 : // In that case consider the session damaged and close it right away,
190 : // even if the control socket is alive.
191 5 : if (peer_dest.find("RESULT=I2P_ERROR") != std::string::npos) {
192 5 : errmsg = strprintf("unexpected reply that hints the session is unusable: %s", peer_dest);
193 5 : disconnect = true;
194 5 : } else {
195 0 : errmsg = e.what();
196 : }
197 : break;
198 5 : }
199 :
200 0 : conn.peer = CService(peer_addr, I2P_SAM31_PORT);
201 :
202 0 : return true;
203 5 : }
204 :
205 5 : if (*m_interrupt) {
206 0 : LogPrintLevel(BCLog::I2P, BCLog::Level::Debug, "Accept was interrupted\n");
207 0 : } else {
208 5 : LogPrintLevel(BCLog::I2P, BCLog::Level::Debug, "Error accepting%s: %s\n", disconnect ? " (will close the session)" : "", errmsg);
209 : }
210 5 : if (disconnect) {
211 5 : LOCK(m_mutex);
212 5 : Disconnect();
213 5 : } else {
214 0 : CheckControlSock();
215 : }
216 5 : return false;
217 10 : }
218 :
219 6 : bool Session::Connect(const CService& to, Connection& conn, bool& proxy_error)
220 : {
221 : // Refuse connecting to arbitrary ports. We don't specify any destination port to the SAM proxy
222 : // when connecting (SAM 3.1 does not use ports) and it forces/defaults it to I2P_SAM31_PORT.
223 6 : if (to.GetPort() != I2P_SAM31_PORT) {
224 0 : LogPrintLevel(BCLog::I2P, BCLog::Level::Debug, "Error connecting to %s, connection refused due to arbitrary port %s\n", to.ToStringAddrPort(), to.GetPort());
225 0 : proxy_error = false;
226 0 : return false;
227 : }
228 :
229 6 : proxy_error = true;
230 :
231 6 : std::string session_id;
232 6 : std::unique_ptr<Sock> sock;
233 6 : conn.peer = to;
234 :
235 : try {
236 : {
237 6 : LOCK(m_mutex);
238 6 : CreateIfNotCreatedAlready();
239 0 : session_id = m_session_id;
240 0 : conn.me = m_my_addr;
241 0 : sock = Hello();
242 6 : }
243 :
244 0 : const Reply& lookup_reply =
245 0 : SendRequestAndGetReply(*sock, strprintf("NAMING LOOKUP NAME=%s", to.ToStringAddr()));
246 :
247 0 : const std::string& dest = lookup_reply.Get("VALUE");
248 :
249 0 : const Reply& connect_reply = SendRequestAndGetReply(
250 0 : *sock, strprintf("STREAM CONNECT ID=%s DESTINATION=%s SILENT=false", session_id, dest),
251 : false);
252 :
253 0 : const std::string& result = connect_reply.Get("RESULT");
254 :
255 0 : if (result == "OK") {
256 0 : conn.sock = std::move(sock);
257 0 : return true;
258 : }
259 :
260 0 : if (result == "INVALID_ID") {
261 0 : LOCK(m_mutex);
262 0 : Disconnect();
263 0 : throw std::runtime_error("Invalid session id");
264 0 : }
265 :
266 0 : if (result == "CANT_REACH_PEER" || result == "TIMEOUT") {
267 0 : proxy_error = false;
268 0 : }
269 :
270 0 : throw std::runtime_error(strprintf("\"%s\"", connect_reply.full));
271 6 : } catch (const std::runtime_error& e) {
272 6 : LogPrintLevel(BCLog::I2P, BCLog::Level::Debug, "Error connecting to %s: %s\n", to.ToStringAddrPort(), e.what());
273 6 : CheckControlSock();
274 6 : return false;
275 6 : }
276 12 : }
277 :
278 : // Private methods
279 :
280 31 : std::string Session::Reply::Get(const std::string& key) const
281 : {
282 31 : const auto& pos = keys.find(key);
283 31 : if (pos == keys.end() || !pos->second.has_value()) {
284 0 : throw std::runtime_error(
285 0 : strprintf("Missing %s= in the reply to \"%s\": \"%s\"", key, request, full));
286 : }
287 31 : return pos->second.value();
288 0 : }
289 :
290 32 : Session::Reply Session::SendRequestAndGetReply(const Sock& sock,
291 : const std::string& request,
292 : bool check_result_ok) const
293 : {
294 33 : sock.SendComplete(request + "\n", MAX_WAIT_FOR_IO, *m_interrupt);
295 :
296 32 : Reply reply;
297 :
298 : // Don't log the full "SESSION CREATE ..." because it contains our private key.
299 32 : reply.request = request.substr(0, 14) == "SESSION CREATE" ? "SESSION CREATE ..." : request;
300 :
301 : // It could take a few minutes for the I2P router to reply as it is querying the I2P network
302 : // (when doing name lookup, for example). Notice: `RecvUntilTerminator()` is checking
303 : // `m_interrupt` more often, so we would not be stuck here for long if `m_interrupt` is
304 : // signaled.
305 : static constexpr auto recv_timeout = 3min;
306 :
307 32 : reply.full = sock.RecvUntilTerminator('\n', recv_timeout, *m_interrupt, MAX_MSG_SIZE);
308 :
309 145 : for (const auto& kv : spanparsing::Split(reply.full, ' ')) {
310 114 : const auto& pos = std::find(kv.begin(), kv.end(), '=');
311 114 : if (pos != kv.end()) {
312 52 : reply.keys.emplace(std::string{kv.begin(), pos}, std::string{pos + 1, kv.end()});
313 52 : } else {
314 62 : reply.keys.emplace(std::string{kv.begin(), kv.end()}, std::nullopt);
315 : }
316 : }
317 :
318 31 : if (check_result_ok && reply.Get("RESULT") != "OK") {
319 0 : throw std::runtime_error(
320 0 : strprintf("Unexpected reply to \"%s\": \"%s\"", request, reply.full));
321 : }
322 :
323 31 : return reply;
324 32 : }
325 :
326 16 : std::unique_ptr<Sock> Session::Hello() const
327 : {
328 16 : auto sock = m_control_host.Connect();
329 :
330 16 : if (!sock) {
331 0 : throw std::runtime_error(strprintf("Cannot connect to %s", m_control_host.ToString()));
332 : }
333 :
334 16 : SendRequestAndGetReply(*sock, "HELLO VERSION MIN=3.1 MAX=3.1");
335 :
336 15 : return sock;
337 16 : }
338 :
339 6 : void Session::CheckControlSock()
340 : {
341 6 : LOCK(m_mutex);
342 :
343 6 : std::string errmsg;
344 6 : if (m_control_sock && !m_control_sock->IsConnected(errmsg)) {
345 0 : LogPrintLevel(BCLog::I2P, BCLog::Level::Debug, "Control socket error: %s\n", errmsg);
346 0 : Disconnect();
347 0 : }
348 6 : }
349 :
350 1 : void Session::DestGenerate(const Sock& sock)
351 : {
352 : // https://geti2p.net/spec/common-structures#key-certificates
353 : // "7" or "EdDSA_SHA512_Ed25519" - "Recent Router Identities and Destinations".
354 : // Use "7" because i2pd <2.24.0 does not recognize the textual form.
355 : // If SIGNATURE_TYPE is not specified, then the default one is DSA_SHA1.
356 1 : const Reply& reply = SendRequestAndGetReply(sock, "DEST GENERATE SIGNATURE_TYPE=7", false);
357 :
358 1 : m_private_key = DecodeI2PBase64(reply.Get("PRIV"));
359 1 : }
360 :
361 1 : void Session::GenerateAndSavePrivateKey(const Sock& sock)
362 : {
363 1 : DestGenerate(sock);
364 :
365 : // umask is set to 0077 in util/system.cpp, which is ok.
366 2 : if (!WriteBinaryFile(m_private_key_file,
367 1 : std::string(m_private_key.begin(), m_private_key.end()))) {
368 0 : throw std::runtime_error(
369 0 : strprintf("Cannot save I2P private key to %s", fs::quoted(fs::PathToString(m_private_key_file))));
370 : }
371 1 : }
372 :
373 10 : Binary Session::MyDestination() const
374 : {
375 : // From https://geti2p.net/spec/common-structures#destination:
376 : // "They are 387 bytes plus the certificate length specified at bytes 385-386, which may be
377 : // non-zero"
378 : static constexpr size_t DEST_LEN_BASE = 387;
379 : static constexpr size_t CERT_LEN_POS = 385;
380 :
381 : uint16_t cert_len;
382 :
383 10 : if (m_private_key.size() < CERT_LEN_POS + sizeof(cert_len)) {
384 8 : throw std::runtime_error(strprintf("The private key is too short (%d < %d)",
385 3 : m_private_key.size(),
386 3 : CERT_LEN_POS + sizeof(cert_len)));
387 : }
388 :
389 7 : memcpy(&cert_len, &m_private_key.at(CERT_LEN_POS), sizeof(cert_len));
390 7 : cert_len = be16toh_internal(cert_len);
391 :
392 7 : const size_t dest_len = DEST_LEN_BASE + cert_len;
393 :
394 7 : if (dest_len > m_private_key.size()) {
395 4 : throw std::runtime_error(strprintf("Certificate length (%d) designates that the private key should "
396 : "be %d bytes, but it is only %d bytes",
397 : cert_len,
398 : dest_len,
399 2 : m_private_key.size()));
400 : }
401 :
402 5 : return Binary{m_private_key.begin(), m_private_key.begin() + dest_len};
403 5 : }
404 :
405 11 : void Session::CreateIfNotCreatedAlready()
406 : {
407 11 : std::string errmsg;
408 11 : if (m_control_sock && m_control_sock->IsConnected(errmsg)) {
409 0 : return;
410 : }
411 :
412 11 : const auto session_type = m_transient ? "transient" : "persistent";
413 11 : const auto session_id = GetRandHash().GetHex().substr(0, 10); // full is overkill, too verbose in the logs
414 :
415 11 : LogPrintLevel(BCLog::I2P, BCLog::Level::Debug, "Creating %s SAM session %s with %s\n", session_type, session_id, m_control_host.ToString());
416 :
417 11 : auto sock = Hello();
418 :
419 10 : if (m_transient) {
420 : // The destination (private key) is generated upon session creation and returned
421 : // in the reply in DESTINATION=.
422 0 : const Reply& reply = SendRequestAndGetReply(
423 0 : *sock,
424 0 : strprintf("SESSION CREATE STYLE=STREAM ID=%s DESTINATION=TRANSIENT SIGNATURE_TYPE=7 "
425 : "i2cp.leaseSetEncType=4,0 inbound.quantity=1 outbound.quantity=1",
426 : session_id));
427 :
428 0 : m_private_key = DecodeI2PBase64(reply.Get("DESTINATION"));
429 0 : } else {
430 : // Read our persistent destination (private key) from disk or generate
431 : // one and save it to disk. Then use it when creating the session.
432 10 : const auto& [read_ok, data] = ReadBinaryFile(m_private_key_file);
433 10 : if (read_ok) {
434 27 : m_private_key.assign(data.begin(), data.end());
435 9 : } else {
436 1 : GenerateAndSavePrivateKey(*sock);
437 : }
438 :
439 10 : const std::string& private_key_b64 = SwapBase64(EncodeBase64(m_private_key));
440 :
441 10 : SendRequestAndGetReply(*sock,
442 10 : strprintf("SESSION CREATE STYLE=STREAM ID=%s DESTINATION=%s "
443 : "i2cp.leaseSetEncType=4,0 inbound.quantity=3 outbound.quantity=3",
444 : session_id,
445 10 : private_key_b64));
446 10 : }
447 :
448 10 : m_my_addr = CService(DestBinToAddr(MyDestination()), I2P_SAM31_PORT);
449 5 : m_session_id = session_id;
450 5 : m_control_sock = std::move(sock);
451 :
452 5 : LogPrintLevel(BCLog::I2P, BCLog::Level::Info, "%s SAM session %s created, my address=%s\n",
453 : Capitalize(session_type),
454 : m_session_id,
455 : m_my_addr.ToStringAddrPort());
456 11 : }
457 :
458 5 : std::unique_ptr<Sock> Session::StreamAccept()
459 : {
460 5 : auto sock = Hello();
461 :
462 5 : const Reply& reply = SendRequestAndGetReply(
463 5 : *sock, strprintf("STREAM ACCEPT ID=%s SILENT=false", m_session_id), false);
464 :
465 5 : const std::string& result = reply.Get("RESULT");
466 :
467 5 : if (result == "OK") {
468 5 : return sock;
469 : }
470 :
471 0 : if (result == "INVALID_ID") {
472 : // If our session id is invalid, then force session re-creation on next usage.
473 0 : Disconnect();
474 0 : }
475 :
476 0 : throw std::runtime_error(strprintf("\"%s\"", reply.full));
477 5 : }
478 :
479 12 : void Session::Disconnect()
480 : {
481 12 : if (m_control_sock) {
482 5 : if (m_session_id.empty()) {
483 0 : LogPrintLevel(BCLog::I2P, BCLog::Level::Info, "Destroying incomplete SAM session\n");
484 0 : } else {
485 5 : LogPrintLevel(BCLog::I2P, BCLog::Level::Info, "Destroying SAM session %s\n", m_session_id);
486 : }
487 5 : m_control_sock.reset();
488 5 : }
489 12 : m_session_id.clear();
490 12 : }
491 : } // namespace sam
492 : } // namespace i2p
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