aboutsummaryrefslogtreecommitdiff
path: root/openssl/agent/pkcs11/agent.cxx
blob: 78e8547901014d6dc63ed5634ce2cd92ba5ecb5d (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
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
// file      : openssl/agent/pkcs11/agent.cxx -*- C++ -*-
// license   : MIT; see accompanying LICENSE file

#include <sys/un.h>     // sockaddr_un
#include <sys/types.h>
#include <sys/socket.h>

#include <signal.h>  // kill(), sigaction(), sigemptyset(), SIG*
#include <unistd.h>  // fork(), getpid(), dup2(), setsid()
#include <termios.h> // tcgetattr(), tcsetattr()

#include <csignal>  // sig_atomic_t
#include <cstring>  // strlen(), strcpy(), memset(), memcmp()
#include <iostream>

#include <iostream> // cout

#include <libbutl/pager.mxx>

#include <openssl/protocol.hxx>
#include <openssl/diagnostics.hxx>

#include <openssl/agent/pkcs11/url.hxx>
#include <openssl/agent/pkcs11/options.hxx>
#include <openssl/agent/pkcs11/private-key.hxx>

namespace openssl
{
  namespace agent
  {
    namespace pkcs11
    {
      using namespace std;
      using namespace butl;

      static void
      pin_prompt (const string& prompt, char*, size_t);

      // The agent daemon top-level function.
      //
      static int
      daemon (const options&,
              identity&&,
              access&&,
              auto_fd&& sock,
              char* pin) noexcept;

      static int
      main (int argc, char* argv[])
      try
      {
        cli::argv_scanner scan (argc, argv);

        // Parse options.
        //
        options ops;
        ops.parse (scan);

        // Version.
        //
        if (ops.version ())
        {
          cout << "openssl-agent-pkcs11 " << OPENSSL_AGENT_VERSION_ID << endl
               << "libbutl " << LIBBUTL_VERSION_ID << endl
               << "Copyright (c) 2014-2019 Code Synthesis Ltd" << endl
               << "This is free software released under the MIT license."
               << endl;

          return 0;
        }

        // Help.
        //
        if (ops.help ())
        {
          pager p ("openssl-agent-pkcs11 help", false);
          print_openssl_agent_pkcs11_usage (p.stream ());

          // If the pager failed, assume it has issued some diagnostics.
          //
          return p.wait () ? 0 : 1;
        }

        // Parse arguments.
        //
        identity key_identity;
        access   key_access;

        try
        {
          string u (scan.more () ? scan.next () : "");
          if (u.empty ())
            fail << "private key URL argument expected";

          url key_url (u);

          key_identity = identity (key_url);
          key_access   = access   (key_url);
        }
        catch (const invalid_argument& e)
        {
          fail << "invalid PKCS#11 URL: " << e;
        }

        try
        {
          // Prompt the user for a token PIN unless it is already specified as
          // an access attribute in the URL.
          //
          char pin[65]; // NULL character-terminated PIN.

          if (!key_access.pin_value)
            pin_prompt ("Enter PIN for PKCS#11", pin, sizeof (pin));

          // Open the agent communication socket and fail if the path is
          // already taken. We could probably deal with the faulty case
          // ourselves but let's not complicate things for now.
          //
          auto_fd sock (socket (AF_UNIX, SOCK_STREAM, 0));

          if (sock.get () == -1)
            throw_system_error (errno);

          path sock_path (path::temp_path ("openssl-agent-pkcs11"));

          struct sockaddr_un addr;
          memset (&addr, 0, sizeof (addr));
          addr.sun_family = AF_UNIX;

          if (sock_path.string ().size () >= sizeof (addr.sun_path))
            throw_generic_error (ENAMETOOLONG);

          strcpy (addr.sun_path, sock_path.string ().c_str ());

          // Creates the socket filesystem entry.
          //
          // Not to confuse with std::bind().
          //
          if (::bind (sock.get (),
                      reinterpret_cast<sockaddr*> (&addr),
                      sizeof (addr)) == -1)
            throw_system_error (errno);

          auto_rmfile rm (sock_path);

          if (listen (sock.get (), 20 /* backlog */) == -1)
            throw_system_error (errno);

          // Fork off the agent daemon.
          //
          pid_t pid (fork ());

          if (pid == -1)
            throw_system_error (errno);

          // Run the agent daemon in the child process.
          //
          if (pid == 0)
            return daemon (ops,
                           move (key_identity),
                           move (key_access),
                           move (sock),
                           !key_access.pin_value ? pin : nullptr);

          // Erase the no longer needed PIN.
          //
          mem_clear (pin, sizeof (pin));

          // The child now is in charge for the socket filesystem entry.
          //
          rm.cancel ();

          sock.close ();

          // Send the init request to the agent to make sure that it is alive
          // and has successfully initialized the key. Issue the received from
          // the agent diagnostics and exit with non-zero status if the
          // initialization failed. Note that the daemon will also exit right
          // after the response in this case.
          //
          {
            sock = connect (sock_path);

            ifdstream is (fddup (sock.get ()));
            ofdstream os (move  (sock));

            os << request ("init");
            os.close ();

            response r;
            is >> r;

            if (r.status != 0)
            {
              text << r.error;
              return r.status;
            }
          }

          // Let's mimic the 'ssh-agent -s' command output.
          //
          cout << "OPENSSL_AGENT_PKCS11_SOCK=" << sock_path << "; "
               << "export OPENSSL_AGENT_PKCS11_SOCK;\n"
               << "OPENSSL_AGENT_PKCS11_PID=" << pid << "; "
               << "export OPENSSL_AGENT_PKCS11_PID;\n"
               << "echo Agent pid " << pid << endl;

          return 0;
        }
        catch (const io_error&)
        {
          fail << "unable to communicate with daemon";
        }
        catch (const system_error& e)
        {
          fail << "unable to start daemon: " << e;
        }

        return 0;
      }
      catch (const failed&)
      {
        return 1; // Diagnostics has already been issued.
      }
      catch (const cli::exception& e)
      {
        error << e;
        return 1;
      }

      // Prompt for the PIN.
      //
      // We would be happy to use getpass() functions but it is mentioned as
      // obsolete in the man page and is likely to be removed from the glibc
      // future versions. Thus, we will provide our own implementation of the
      // function that is inspired by the openssh implementation.
      //
      // Note: _NSIG is Linux-specic.
      //
      static volatile sig_atomic_t received_signals[_NSIG];

      extern "C" void
      handle_signal (int sig)
      {
        received_signals[sig] = 1;
      }

      static void
      pin_prompt (const string& prompt, char* buf, size_t max_len)
      {
        // Note that openssh tries to open /dev/tty for read/write access but
        // falls back to stdin/stdout on failure. Let's skip the fallback for
        // simplicity.
        //
        try
        {
          auto_fd ifd  (fdopen ("/dev/tty", fdopen_mode::in));
          ofdstream os (fdopen ("/dev/tty", fdopen_mode::out));

          // Disable the echo.
          //
          termios term_attrs;
          if (tcgetattr (os.fd (), &term_attrs) == -1)
            throw_system_error (errno);

          termios na (term_attrs);
          na.c_lflag &= ~ECHO;

          if (tcsetattr (os.fd (), TCSAFLUSH, &na) == -1)
            throw_system_error (errno);

          // Catch signals that would otherwise cause the user to end up with
          // echo turned off in the shell.
          //
          for (size_t i (0); i < _NSIG; ++i)
            received_signals[i] = 0;

          using sigaction_type = struct sigaction;

          sigaction_type sa;
          memset (&sa, 0, sizeof (sa));
          sigemptyset (&sa.sa_mask);
          sa.sa_handler = handle_signal;

          // Save the current signal handlers while setting up the new ones.
          //
          vector<pair<int, sigaction_type>> sig_handlers;

          const vector<int> sigs ({
              SIGALRM,
              SIGHUP,
              SIGINT,
              SIGPIPE,
              SIGQUIT,
              SIGTERM,
              SIGTSTP,
              SIGTTIN,
              SIGTTOU});

          for (int s: sigs)
          {
            sig_handlers.push_back (make_pair (s, sigaction_type ()));

            if (sigaction (s, &sa, &sig_handlers.back ().second) == -1)
              throw_system_error (errno);
          }

          // Restore the echo state and signal handlers and resend the
          // received signals.
          //
          auto restore = [&os, &term_attrs, &sig_handlers] ()
          {
            if (tcsetattr (os.fd (), TCSAFLUSH, &term_attrs) == -1)
              throw_system_error (errno);

            for (const pair<int, sigaction_type>& sa: sig_handlers)
            {
              if (sigaction (sa.first, &sa.second, nullptr) == -1)
                throw_system_error (errno);
            }

            pid_t pid (getpid ());
            for (int i (0); i < _NSIG; i++)
            {
              if (received_signals[i] != 0 && kill (pid, i) == -1)
                throw_system_error (errno);
            }
          };

          auto rst (make_exception_guard ([&restore] ()
                                          {
                                            try
                                            {
                                              restore ();
                                            }
                                            catch (const system_error&)
                                            {
                                              // Not much we can do here.
                                              //
                                            }
                                          }));

          // Print prompt.
          //
          os << prompt << ": " << flush;

          // Read the PIN.
          //
          // Reserve space for the terminating NULL character.
          //
          size_t n (max_len - 1);
          size_t i (0);
          for (; i < n; ++i)
          {
            ssize_t r (read (ifd.get (), buf + i, 1));
            if (r == -1)
              throw_system_error (errno);

            if (r == 0 || buf[i] == '\n')
              break;
          }

          restore ();

          os << endl;
          os.close ();

          if (i == n)
            fail << "PIN is too long";

          buf[i] = '\0';
        }
        catch (const system_error& e)
        {
          fail << "failed to read PIN: " << e;
        }
      }

      // Terminate the daemon.
      //
      static volatile sig_atomic_t exit_requested (0); // Can be used as bool.

      extern "C" void
      handle_term (int /* sig */)
      {
        exit_requested = 1;

        // Now accept() will wakeup, set errno to EINTR, and return with -1.
        //
      }

      // Run the daemon.
      //
      static int
      daemon (const options& ops,
              identity&& ki,
              access&& ka,
              auto_fd&& sc,
              char* pin) noexcept
      try
      {
        // Demonize ourselves.
        //
        {
          if (setsid () == -1)
            throw_system_error (errno);

          dir_path::current_directory (dir_path ("/"));

          auto_fd nd (fdnull ());

          auto redir = [&nd] (int sd)
          {
            if (dup2 (nd.get (), sd) == -1)
              throw_system_error (errno);
          };

          redir (0);
          redir (1);
          redir (2);
        }

        auto_fd  sock         (move (sc));
        identity key_identity (move (ki));
        access   key_access   (move (ka));

        struct sigaction sa;
        memset (&sa, 0, sizeof (sa));
        sigemptyset (&sa.sa_mask);
        sa.sa_handler = handle_term;

        if (sigaction (SIGTERM, &sa, nullptr) == -1)
          throw_system_error (errno);

        // It would be natural to create the key at the time of receiving the
        // init request. However, we need to erase the PIN as soon as
        // possible. Thus, we will create it now. In case of failure we will
        // save the error to use for the upcoming init request response.
        //
        private_key key;

        // If present, indicates that we still expect the init request. Will
        // set it to nullopt after init request processing.
        //
        optional<string> init_error;

        try
        {
          optional<simulate_outcome> s;
          if (ops.simulate_specified ())
            s = ops.simulate ();

          key = private_key (key_identity, key_access, pin, s);
          init_error = "";
        }
        catch (const invalid_argument& e)
        {
          init_error = string ("error: ") + e.what ();
        }
        catch (const runtime_error& e)
        {
          init_error = string ("error: ") + e.what ();
        }

        // Erase the no longer needed PIN.
        //
        if (pin != nullptr)
          mem_clear (pin, strlen (pin));

        // Run the request processing loop.
        //
        while (true)
        {
          // Accept the client connection.
          //
          auto_fd fd (
            accept (sock.get (), nullptr /* addr */, nullptr /* addrlen */));

          if (exit_requested)
            break;

          if (fd.get () == -1)
          {
            if (errno == EINTR || errno == ECONNABORTED || errno == EPROTO)
              continue;

            throw_system_error (errno);
          }

          // If we fail to duplicate the file descriptor, then we are probably
          // out of resources. Anyway we can't do much about it and will bail
          // out.
          //
          ifdstream is (fddup (fd.get ()));

          try
          {
            ofdstream os (move (fd));

            // Respond to the client until he sends valid requests.
            //
            while (is.peek () != ifdstream::traits_type::eof ())
            {
              request rq;
              is >> rq;

              // The init request must be the first and only one.
              //
              if (rq.cmd == "init")
              {
                if (!init_error)
                {
                  os << response ("error: already initialized");
                  break;
                }

                if (!init_error->empty ())
                {
                  os << response (*init_error);
                  os.close ();

                  throw runtime_error (*init_error);
                }

                init_error = nullopt; // We don't expect init anymore.
                os << response ();    // Success.
                continue;
              }

              if (init_error)
              {
                os << response ("error: not initialized");
                break;
              }

              // Process the sign request.
              //
              if (rq.cmd == "sign")
              {
                // Parse and validate the request arguments (key URL and
                // simulate outcome).
                //
                if (rq.args.size () != 2)
                {
                  os << response ("error: invalid args");
                  break;
                }

                identity k;

                try
                {
                  k = identity (url (rq.args[0]));
                }
                catch (const invalid_argument& e)
                {
                  os << response (
                    string ("error: invalid private key URL: ") + e.what ());

                  break;
                }

                optional<simulate_outcome> sim;

                if (!rq.args[1].empty ())
                try
                {
                  sim = to_simulate_outcome (rq.args[1]);
                }
                catch (const invalid_argument& e)
                {
                  os << response (string ("error: ") + e.what ());
                  break;
                }

                if (k != key_identity)
                {
                  os << response ("error: private key doesn't match");
                  break;
                }

                try
                {
                  os << response (key.sign (rq.input, sim));
                }
                catch (const runtime_error& e)
                {
                  os << response (string ("error: ") + e.what ());
                  break;
                }
              }
            }

            // Close the client connection.
            //
            is.close ();
            os.close ();
          }
          catch (const io_error&)
          {
            // The client is presumably dead.
            //
          }
        }

        return 0;
      }
      catch (const std::exception&)
      {
        // There is no way we can complain.
        //
        return 1;
      }
    }
  }
}

int
main (int argc, char* argv[])
{
  return openssl::agent::pkcs11::main (argc, argv);
}