aboutsummaryrefslogtreecommitdiff
path: root/src/i2p.cpp
blob: f7d480988b3275e5c76095c195c3f9530f5bc4ef (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
// Copyright (c) 2020-2021 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 <chainparams.h>
#include <compat/compat.h>
#include <compat/endian.h>
#include <crypto/sha256.h>
#include <fs.h>
#include <i2p.h>
#include <logging.h>
#include <netaddress.h>
#include <netbase.h>
#include <random.h>
#include <tinyformat.h>
#include <util/readwritefile.h>
#include <util/sock.h>
#include <util/spanparsing.h>
#include <util/strencodings.h>
#include <util/system.h>

#include <chrono>
#include <memory>
#include <stdexcept>
#include <string>

namespace i2p {

/**
 * Swap Standard Base64 <-> I2P Base64.
 * Standard Base64 uses `+` and `/` as last two characters of its alphabet.
 * I2P Base64 uses `-` and `~` respectively.
 * So it is easy to detect in which one is the input and convert to the other.
 * @param[in] from Input to convert.
 * @return converted `from`
 */
static std::string SwapBase64(const std::string& from)
{
    std::string to;
    to.resize(from.size());
    for (size_t i = 0; i < from.size(); ++i) {
        switch (from[i]) {
        case '-':
            to[i] = '+';
            break;
        case '~':
            to[i] = '/';
            break;
        case '+':
            to[i] = '-';
            break;
        case '/':
            to[i] = '~';
            break;
        default:
            to[i] = from[i];
            break;
        }
    }
    return to;
}

/**
 * Decode an I2P-style Base64 string.
 * @param[in] i2p_b64 I2P-style Base64 string.
 * @return decoded `i2p_b64`
 * @throw std::runtime_error if decoding fails
 */
static Binary DecodeI2PBase64(const std::string& i2p_b64)
{
    const std::string& std_b64 = SwapBase64(i2p_b64);
    auto decoded = DecodeBase64(std_b64);
    if (!decoded) {
        throw std::runtime_error(strprintf("Cannot decode Base64: \"%s\"", i2p_b64));
    }
    return std::move(*decoded);
}

/**
 * Derive the .b32.i2p address of an I2P destination (binary).
 * @param[in] dest I2P destination.
 * @return the address that corresponds to `dest`
 * @throw std::runtime_error if conversion fails
 */
static CNetAddr DestBinToAddr(const Binary& dest)
{
    CSHA256 hasher;
    hasher.Write(dest.data(), dest.size());
    unsigned char hash[CSHA256::OUTPUT_SIZE];
    hasher.Finalize(hash);

    CNetAddr addr;
    const std::string addr_str = EncodeBase32(hash, false) + ".b32.i2p";
    if (!addr.SetSpecial(addr_str)) {
        throw std::runtime_error(strprintf("Cannot parse I2P address: \"%s\"", addr_str));
    }

    return addr;
}

/**
 * Derive the .b32.i2p address of an I2P destination (I2P-style Base64).
 * @param[in] dest I2P destination.
 * @return the address that corresponds to `dest`
 * @throw std::runtime_error if conversion fails
 */
static CNetAddr DestB64ToAddr(const std::string& dest)
{
    const Binary& decoded = DecodeI2PBase64(dest);
    return DestBinToAddr(decoded);
}

namespace sam {

Session::Session(const fs::path& private_key_file,
                 const CService& control_host,
                 CThreadInterrupt* interrupt)
    : m_private_key_file{private_key_file},
      m_control_host{control_host},
      m_interrupt{interrupt},
      m_control_sock{std::make_unique<Sock>(INVALID_SOCKET)},
      m_transient{false}
{
}

Session::Session(const CService& control_host, CThreadInterrupt* interrupt)
    : m_control_host{control_host},
      m_interrupt{interrupt},
      m_control_sock{std::make_unique<Sock>(INVALID_SOCKET)},
      m_transient{true}
{
}

Session::~Session()
{
    LOCK(m_mutex);
    Disconnect();
}

bool Session::Listen(Connection& conn)
{
    try {
        LOCK(m_mutex);
        CreateIfNotCreatedAlready();
        conn.me = m_my_addr;
        conn.sock = StreamAccept();
        return true;
    } catch (const std::runtime_error& e) {
        Log("Error listening: %s", e.what());
        CheckControlSock();
    }
    return false;
}

bool Session::Accept(Connection& conn)
{
    try {
        while (!*m_interrupt) {
            Sock::Event occurred;
            if (!conn.sock->Wait(MAX_WAIT_FOR_IO, Sock::RECV, &occurred)) {
                throw std::runtime_error("wait on socket failed");
            }

            if (occurred == 0) {
                // Timeout, no incoming connections or errors within MAX_WAIT_FOR_IO.
                continue;
            }

            const std::string& peer_dest =
                conn.sock->RecvUntilTerminator('\n', MAX_WAIT_FOR_IO, *m_interrupt, MAX_MSG_SIZE);

            conn.peer = CService(DestB64ToAddr(peer_dest), I2P_SAM31_PORT);

            return true;
        }
    } catch (const std::runtime_error& e) {
        Log("Error accepting: %s", e.what());
        CheckControlSock();
    }
    return false;
}

bool Session::Connect(const CService& to, Connection& conn, bool& proxy_error)
{
    // Refuse connecting to arbitrary ports. We don't specify any destination port to the SAM proxy
    // when connecting (SAM 3.1 does not use ports) and it forces/defaults it to I2P_SAM31_PORT.
    if (to.GetPort() != I2P_SAM31_PORT) {
        proxy_error = false;
        return false;
    }

    proxy_error = true;

    std::string session_id;
    std::unique_ptr<Sock> sock;
    conn.peer = to;

    try {
        {
            LOCK(m_mutex);
            CreateIfNotCreatedAlready();
            session_id = m_session_id;
            conn.me = m_my_addr;
            sock = Hello();
        }

        const Reply& lookup_reply =
            SendRequestAndGetReply(*sock, strprintf("NAMING LOOKUP NAME=%s", to.ToStringIP()));

        const std::string& dest = lookup_reply.Get("VALUE");

        const Reply& connect_reply = SendRequestAndGetReply(
            *sock, strprintf("STREAM CONNECT ID=%s DESTINATION=%s SILENT=false", session_id, dest),
            false);

        const std::string& result = connect_reply.Get("RESULT");

        if (result == "OK") {
            conn.sock = std::move(sock);
            return true;
        }

        if (result == "INVALID_ID") {
            LOCK(m_mutex);
            Disconnect();
            throw std::runtime_error("Invalid session id");
        }

        if (result == "CANT_REACH_PEER" || result == "TIMEOUT") {
            proxy_error = false;
        }

        throw std::runtime_error(strprintf("\"%s\"", connect_reply.full));
    } catch (const std::runtime_error& e) {
        Log("Error connecting to %s: %s", to.ToString(), e.what());
        CheckControlSock();
        return false;
    }
}

// Private methods

std::string Session::Reply::Get(const std::string& key) const
{
    const auto& pos = keys.find(key);
    if (pos == keys.end() || !pos->second.has_value()) {
        throw std::runtime_error(
            strprintf("Missing %s= in the reply to \"%s\": \"%s\"", key, request, full));
    }
    return pos->second.value();
}

template <typename... Args>
void Session::Log(const std::string& fmt, const Args&... args) const
{
    LogPrint(BCLog::I2P, "%s\n", tfm::format(fmt, args...));
}

Session::Reply Session::SendRequestAndGetReply(const Sock& sock,
                                               const std::string& request,
                                               bool check_result_ok) const
{
    sock.SendComplete(request + "\n", MAX_WAIT_FOR_IO, *m_interrupt);

    Reply reply;

    // Don't log the full "SESSION CREATE ..." because it contains our private key.
    reply.request = request.substr(0, 14) == "SESSION CREATE" ? "SESSION CREATE ..." : request;

    // It could take a few minutes for the I2P router to reply as it is querying the I2P network
    // (when doing name lookup, for example). Notice: `RecvUntilTerminator()` is checking
    // `m_interrupt` more often, so we would not be stuck here for long if `m_interrupt` is
    // signaled.
    static constexpr auto recv_timeout = 3min;

    reply.full = sock.RecvUntilTerminator('\n', recv_timeout, *m_interrupt, MAX_MSG_SIZE);

    for (const auto& kv : spanparsing::Split(reply.full, ' ')) {
        const auto& pos = std::find(kv.begin(), kv.end(), '=');
        if (pos != kv.end()) {
            reply.keys.emplace(std::string{kv.begin(), pos}, std::string{pos + 1, kv.end()});
        } else {
            reply.keys.emplace(std::string{kv.begin(), kv.end()}, std::nullopt);
        }
    }

    if (check_result_ok && reply.Get("RESULT") != "OK") {
        throw std::runtime_error(
            strprintf("Unexpected reply to \"%s\": \"%s\"", request, reply.full));
    }

    return reply;
}

std::unique_ptr<Sock> Session::Hello() const
{
    auto sock = CreateSock(m_control_host);

    if (!sock) {
        throw std::runtime_error("Cannot create socket");
    }

    if (!ConnectSocketDirectly(m_control_host, *sock, nConnectTimeout, true)) {
        throw std::runtime_error(strprintf("Cannot connect to %s", m_control_host.ToString()));
    }

    SendRequestAndGetReply(*sock, "HELLO VERSION MIN=3.1 MAX=3.1");

    return sock;
}

void Session::CheckControlSock()
{
    LOCK(m_mutex);

    std::string errmsg;
    if (!m_control_sock->IsConnected(errmsg)) {
        Log("Control socket error: %s", errmsg);
        Disconnect();
    }
}

void Session::DestGenerate(const Sock& sock)
{
    // https://geti2p.net/spec/common-structures#key-certificates
    // "7" or "EdDSA_SHA512_Ed25519" - "Recent Router Identities and Destinations".
    // Use "7" because i2pd <2.24.0 does not recognize the textual form.
    const Reply& reply = SendRequestAndGetReply(sock, "DEST GENERATE SIGNATURE_TYPE=7", false);

    m_private_key = DecodeI2PBase64(reply.Get("PRIV"));
}

void Session::GenerateAndSavePrivateKey(const Sock& sock)
{
    DestGenerate(sock);

    // umask is set to 077 in init.cpp, which is ok (unless -sysperms is given)
    if (!WriteBinaryFile(m_private_key_file,
                         std::string(m_private_key.begin(), m_private_key.end()))) {
        throw std::runtime_error(
            strprintf("Cannot save I2P private key to %s", fs::quoted(fs::PathToString(m_private_key_file))));
    }
}

Binary Session::MyDestination() const
{
    // From https://geti2p.net/spec/common-structures#destination:
    // "They are 387 bytes plus the certificate length specified at bytes 385-386, which may be
    // non-zero"
    static constexpr size_t DEST_LEN_BASE = 387;
    static constexpr size_t CERT_LEN_POS = 385;

    uint16_t cert_len;
    memcpy(&cert_len, &m_private_key.at(CERT_LEN_POS), sizeof(cert_len));
    cert_len = be16toh(cert_len);

    const size_t dest_len = DEST_LEN_BASE + cert_len;

    return Binary{m_private_key.begin(), m_private_key.begin() + dest_len};
}

void Session::CreateIfNotCreatedAlready()
{
    std::string errmsg;
    if (m_control_sock->IsConnected(errmsg)) {
        return;
    }

    const auto session_type = m_transient ? "transient" : "persistent";
    const auto session_id = GetRandHash().GetHex().substr(0, 10); // full is overkill, too verbose in the logs

    Log("Creating %s SAM session %s with %s", session_type, session_id, m_control_host.ToString());

    auto sock = Hello();

    if (m_transient) {
        // The destination (private key) is generated upon session creation and returned
        // in the reply in DESTINATION=.
        const Reply& reply = SendRequestAndGetReply(
            *sock,
            strprintf("SESSION CREATE STYLE=STREAM ID=%s DESTINATION=TRANSIENT", session_id));

        m_private_key = DecodeI2PBase64(reply.Get("DESTINATION"));
    } else {
        // Read our persistent destination (private key) from disk or generate
        // one and save it to disk. Then use it when creating the session.
        const auto& [read_ok, data] = ReadBinaryFile(m_private_key_file);
        if (read_ok) {
            m_private_key.assign(data.begin(), data.end());
        } else {
            GenerateAndSavePrivateKey(*sock);
        }

        const std::string& private_key_b64 = SwapBase64(EncodeBase64(m_private_key));

        SendRequestAndGetReply(*sock,
                               strprintf("SESSION CREATE STYLE=STREAM ID=%s DESTINATION=%s",
                                         session_id,
                                         private_key_b64));
    }

    m_my_addr = CService(DestBinToAddr(MyDestination()), I2P_SAM31_PORT);
    m_session_id = session_id;
    m_control_sock = std::move(sock);

    Log("%s SAM session %s created, my address=%s",
        Capitalize(session_type),
        m_session_id,
        m_my_addr.ToString());
}

std::unique_ptr<Sock> Session::StreamAccept()
{
    auto sock = Hello();

    const Reply& reply = SendRequestAndGetReply(
        *sock, strprintf("STREAM ACCEPT ID=%s SILENT=false", m_session_id), false);

    const std::string& result = reply.Get("RESULT");

    if (result == "OK") {
        return sock;
    }

    if (result == "INVALID_ID") {
        // If our session id is invalid, then force session re-creation on next usage.
        Disconnect();
    }

    throw std::runtime_error(strprintf("\"%s\"", reply.full));
}

void Session::Disconnect()
{
    if (m_control_sock->Get() != INVALID_SOCKET) {
        if (m_session_id.empty()) {
            Log("Destroying incomplete SAM session");
        } else {
            Log("Destroying SAM session %s", m_session_id);
        }
    }
    m_control_sock = std::make_unique<Sock>(INVALID_SOCKET);
    m_session_id.clear();
}
} // namespace sam
} // namespace i2p