mono/metadata/attach.c

   1 /*
   2  * attach.c: Support for attaching to the runtime from other processes.
   3  *
   4  * Author:
   5  *   Zoltan Varga (vargaz@gmail.com)
   6  *
   7  * Copyright 2007-2009 Novell, Inc (http://www.novell.com)
   8  * Licensed under the MIT license. See LICENSE file in the project root for full license information.
   9  */
  10
  11 #include <config.h>
  12 #include <glib.h>
  13
  14 #ifdef HOST_WIN32
  15 #define DISABLE_ATTACH
  16 #endif
  17 #ifndef DISABLE_ATTACH
  18
  19 #include <stdio.h>
  20 #include <stdlib.h>
  21 #include <string.h>
  22 #include <sys/types.h>
  23 #include <sys/socket.h>
  24 #include <sys/stat.h>
  25 #include <sys/un.h>
  26 #include <netinet/in.h>
  27 #include <sys/types.h>
  28 #include <sys/stat.h>
  29 #include <fcntl.h>
  30 #include <inttypes.h>
  31 #include <pwd.h>
  32 #include <errno.h>
  33 #include <netdb.h>
  34 #include <unistd.h>
  35
  36 #include <mono/metadata/assembly.h>
  37 #include <mono/metadata/metadata.h>
  38 #include <mono/metadata/class-internals.h>
  39 #include <mono/metadata/object-internals.h>
  40 #include <mono/metadata/threads-types.h>
  41 #include <mono/metadata/gc-internals.h>
  42 #include <mono/utils/mono-threads.h>
  43 #include "attach.h"
  44
  45 /*
  46  * This module enables other processes to attach to a running mono process and
  47  * load agent assemblies.
  48  * Communication is done through a UNIX Domain Socket located at
  49  * /tmp/mono-<USER>/.mono-<PID>.
  50  * We use a simplified version of the .net remoting protocol.
  51  * To increase security, and to avoid spinning up a listener thread on startup,
  52  * we follow the java implementation, and only start up the attach mechanism
  53  * when we receive a QUIT signal and there is a file named
  54  * '.mono_attach_pid<PID>' in /tmp.
  55  *
  56  * SECURITY:
  57  * - This module allows loading of arbitrary code into a running mono runtime, so
  58  *   it is security critical.
  59  * - Security is based on controlling access to the unix file to which the unix
  60  *   domain socket is bound. Permissions/ownership are set such that only the owner
  61  *   of the process can access the socket.
  62  * - As an additional measure, the socket is only created when the process receives
  63  *   a SIGQUIT signal, which only its owner/root can send.
  64  * - The socket is kept in a directory whose ownership is checked before creating
  65  *   the socket. This could allow an attacker a kind of DOS attack by creating the
  66  *   directory with the wrong permissions/ownership. However, the only thing such
  67  *   an attacker could prevent is the attaching of agents to the mono runtime.
  68  */
  69
  70 typedef struct {
  71         gboolean enabled;
  72 } AgentConfig;
  73
  74 typedef struct {
  75         int bytes_sent;
  76 } AgentStats;
  77
  78 /*******************************************************************/
  79 /* Remoting Protocol type definitions from [MS-NRBF] and [MS-NRTP] */
  80 /*******************************************************************/
  81
  82 typedef enum {
  83         PRIM_TYPE_INT32 = 8,
  84         PRIM_TYPE_INT64 = 9,
  85         PRIM_TYPE_NULL = 17,
  86         PRIM_TYPE_STRING = 18
  87 } PrimitiveType;
  88
  89 static AgentConfig config;
  90
  91 static int listen_fd, conn_fd;
  92
  93 static char *ipc_filename;
  94
  95 static char *server_uri;
  96
  97 static HANDLE receiver_thread_handle;
  98
  99 static gboolean stop_receiver_thread;
 100
 101 static gboolean needs_to_start, started;
 102
 103 static void transport_connect (void);
 104
 105 static gsize WINAPI receiver_thread (void *arg);
 106
 107 static void transport_start_receive (void);
 108
 109 /*
 110  * Functions to decode protocol data
 111  */
 112 static inline int
 113 decode_byte (guint8 *buf, guint8 **endbuf, guint8 *limit)
 114 {
 115         *endbuf = buf + 1;
 116         g_assert (*endbuf <= limit);
 117         return buf [0];
 118 }
 119
 120 static inline int
 121 decode_int (guint8 *buf, guint8 **endbuf, guint8 *limit)
 122 {
 123         *endbuf = buf + 4;
 124         g_assert (*endbuf <= limit);
 125
 126         return (((int)buf [0]) << 0) | (((int)buf [1]) << 8) | (((int)buf [2]) << 16) | (((int)buf [3]) << 24);
 127 }
 128
 129 static char*
 130 decode_string_value (guint8 *buf, guint8 **endbuf, guint8 *limit)
 131 {
 132         int type;
 133     gint32 length;
 134         guint8 *p = buf;
 135         char *s;
 136
 137         type = decode_byte (p, &p, limit);
 138         if (type == PRIM_TYPE_NULL) {
 139                 *endbuf = p;
 140                 return NULL;
 141         }
 142         g_assert (type == PRIM_TYPE_STRING);
 143
 144         length = 0;
 145         while (TRUE) {
 146                 guint8 b = decode_byte (p, &p, limit);
 147
 148                 length <<= 8;
 149                 length += b;
 150                 if (b <= 0x7f)
 151                         break;
 152         }
 153
 154         g_assert (length < (1 << 16));
 155
 156         s = (char *)g_malloc (length + 1);
 157
 158         g_assert (p + length <= limit);
 159         memcpy (s, p, length);
 160         s [length] = '\0';
 161         p += length;
 162
 163         *endbuf = p;
 164
 165         return s;
 166 }
 167
 168 /********************************/
 169 /*    AGENT IMPLEMENTATION      */
 170 /********************************/
 171
 172 void
 173 mono_attach_parse_options (char *options)
 174 {
 175         if (!options)
 176                 return;
 177         if (!strcmp (options, "disable"))
 178                 config.enabled = FALSE;
 179 }
 180
 181 void
 182 mono_attach_init (void)
 183 {
 184         config.enabled = TRUE;
 185 }
 186
 187 /**
 188  * mono_attach_start:
 189  *
 190  * Start the attach mechanism if needed.  This is called from a signal handler so it must be signal safe.
 191  *
 192  * Returns: whenever it was started.
 193  */
 194 gboolean
 195 mono_attach_start (void)
 196 {
 197         char path [256];
 198         int fd;
 199
 200         if (started)
 201                 return FALSE;
 202
 203         /* Check for the existence of the trigger file */
 204
 205         /*
 206          * We don't do anything with this file, and the only thing an attacker can do
 207          * by creating it is to enable the attach mechanism if the process receives a
 208          * SIGQUIT signal, which can only be sent by the owner/root.
 209          */
 210         snprintf (path, sizeof (path), "/tmp/.mono_attach_pid%"PRIdMAX"", (intmax_t) getpid ());
 211         fd = open (path, O_RDONLY);
 212         if (fd == -1)
 213                 return FALSE;
 214         close (fd);
 215
 216         if (!config.enabled)
 217                 /* Act like we started */
 218                 return TRUE;
 219
 220         if (started)
 221                 return FALSE;
 222
 223         /*
 224          * Our startup includes non signal-safe code, so ask the finalizer thread to
 225          * do the actual startup.
 226          */
 227         needs_to_start = TRUE;
 228         mono_gc_finalize_notify ();
 229
 230         return TRUE;
 231 }
 232
 233 /* Called by the finalizer thread when it is woken up */
 234 void
 235 mono_attach_maybe_start (void)
 236 {
 237         if (!needs_to_start)
 238                 return;
 239
 240         needs_to_start = FALSE;
 241         if (!started) {
 242                 transport_start_receive ();
 243
 244                 started = TRUE;
 245         }
 246 }
 247
 248 void
 249 mono_attach_cleanup (void)
 250 {
 251         if (listen_fd)
 252                 close (listen_fd);
 253         if (ipc_filename)
 254                 unlink (ipc_filename);
 255
 256         stop_receiver_thread = TRUE;
 257         if (conn_fd)
 258                 /* This will cause receiver_thread () to break out of the read () call */
 259                 close (conn_fd);
 260
 261         /* Wait for the receiver thread to exit */
 262         if (receiver_thread_handle)
 263                 WaitForSingleObjectEx (receiver_thread_handle, 0, FALSE);
 264 }
 265
 266 static int
 267 mono_attach_load_agent (MonoDomain *domain, char *agent, char *args, MonoObject **exc)
 268 {
 269         MonoError error;
 270         MonoAssembly *agent_assembly;
 271         MonoImage *image;
 272         MonoMethod *method;
 273         guint32 entry;
 274         MonoArray *main_args;
 275         gpointer pa [1];
 276         MonoImageOpenStatus open_status;
 277
 278         agent_assembly = mono_assembly_open (agent, &open_status);
 279         if (!agent_assembly) {
 280                 fprintf (stderr, "Cannot open agent assembly '%s': %s.\n", agent, mono_image_strerror (open_status));
 281                 g_free (agent);
 282                 return 2;
 283         }
 284
 285         /*
 286          * Can't use mono_jit_exec (), as it sets things which might confuse the
 287          * real Main method.
 288          */
 289         image = mono_assembly_get_image (agent_assembly);
 290         entry = mono_image_get_entry_point (image);
 291         if (!entry) {
 292                 g_print ("Assembly '%s' doesn't have an entry point.\n", mono_image_get_filename (image));
 293                 g_free (agent);
 294                 return 1;
 295         }
 296
 297         method = mono_get_method_checked (image, entry, NULL, NULL, &error);
 298         if (method == NULL){
 299                 g_print ("The entry point method of assembly '%s' could not be loaded due to %s\n", agent, mono_error_get_message (&error));
 300                 mono_error_cleanup (&error);
 301                 g_free (agent);
 302                 return 1;
 303         }
 304
 305
 306         main_args = (MonoArray*)mono_array_new_checked (domain, mono_defaults.string_class, (args == NULL) ? 0 : 1, &error);
 307         if (main_args == NULL) {
 308                 g_print ("Could not allocate main method args due to %s\n", mono_error_get_message (&error));
 309                 mono_error_cleanup (&error);
 310                 g_free (agent);
 311                 return 1;
 312         }
 313
 314         if (args) {
 315                 mono_array_set (main_args, MonoString*, 0, mono_string_new (domain, args));
 316         }
 317
 318
 319         pa [0] = main_args;
 320         mono_runtime_try_invoke (method, NULL, pa, exc, &error);
 321         if (!is_ok (&error)) {
 322                 g_print ("The entry point method of assembly '%s' could not be executed due to %s\n", agent, mono_error_get_message (&error));
 323                 mono_error_cleanup (&error);
 324                 g_free (agent);
 325                 return 1;
 326         }
 327
 328         g_free (agent);
 329
 330         return 0;
 331 }
 332
 333 /*
 334  * ipc_connect:
 335  *
 336  *   Create a UNIX domain socket and bind it to a file in /tmp.
 337  *
 338  * SECURITY: This routine is _very_ security critical since we depend on the UNIX
 339  * permissions system to prevent attackers from connecting to the socket.
 340  */
 341 static void
 342 ipc_connect (void)
 343 {
 344         struct sockaddr_un name;
 345         int sock, res;
 346         size_t size;
 347         char *filename, *directory;
 348         struct stat stat;
 349         struct passwd pwbuf;
 350         char buf [1024];
 351         struct passwd *pw;
 352
 353         if (getuid () != geteuid ()) {
 354                 fprintf (stderr, "attach: disabled listening on an IPC socket when running in setuid mode.\n");
 355                 return;
 356         }
 357
 358         /* Create the socket.   */
 359         sock = socket (PF_UNIX, SOCK_STREAM, 0);
 360         if (sock < 0) {
 361                 perror ("attach: failed to create IPC socket");
 362                 return;
 363         }
 364
 365         /*
 366          * For security reasons, create a directory to hold the listening socket,
 367          * since there is a race between bind () and chmod () below.
 368          */
 369         /* FIXME: Use TMP ? */
 370         pw = NULL;
 371 #ifdef HAVE_GETPWUID_R
 372         res = getpwuid_r (getuid (), &pwbuf, buf, sizeof (buf), &pw);
 373 #else
 374         pw = getpwuid(getuid ());
 375         res = pw != NULL ? 0 : 1;
 376 #endif
 377         if (res != 0) {
 378                 fprintf (stderr, "attach: getpwuid_r () failed.\n");
 379                 return;
 380         }
 381         g_assert (pw);
 382         directory = g_strdup_printf ("/tmp/mono-%s", pw->pw_name);
 383         res = mkdir (directory, S_IRUSR | S_IWUSR | S_IXUSR);
 384         if (res != 0) {
 385                 if (errno == EEXIST) {
 386                         /* Check type and permissions */
 387                         res = lstat (directory, &stat);
 388                         if (res != 0) {
 389                                 perror ("attach: lstat () failed");
 390                                 return;
 391                         }
 392                         if (!S_ISDIR (stat.st_mode)) {
 393                                 fprintf (stderr, "attach: path '%s' is not a directory.\n", directory);
 394                                 return;
 395                         }
 396                         if (stat.st_uid != getuid ()) {
 397                                 fprintf (stderr, "attach: directory '%s' is not owned by the current user.\n", directory);
 398                                 return;
 399                         }
 400                         if ((stat.st_mode & S_IRWXG) != 0 || (stat.st_mode & S_IRWXO) || ((stat.st_mode & S_IRWXU) != (S_IRUSR | S_IWUSR | S_IXUSR))) {
 401                                 fprintf (stderr, "attach: directory '%s' should have protection 0700.\n", directory);
 402                                 return;
 403                         }
 404                 } else {
 405                         perror ("attach: mkdir () failed");
 406                         return;
 407                 }
 408         }
 409
 410         filename = g_strdup_printf ("%s/.mono-%"PRIdMAX"", directory, (intmax_t) getpid ());
 411         unlink (filename);
 412
 413         /* Bind a name to the socket.   */
 414         name.sun_family = AF_UNIX;
 415         strcpy (name.sun_path, filename);
 416
 417         size = (offsetof (struct sockaddr_un, sun_path)
 418                         + strlen (name.sun_path) + 1);
 419
 420         if (bind (sock, (struct sockaddr *) &name, size) < 0) {
 421                 fprintf (stderr, "attach: failed to bind IPC socket '%s': %s\n", filename, strerror (errno));
 422                 close (sock);
 423                 return;
 424         }
 425
 426         /* Set permissions */
 427         res = chmod (filename, S_IRUSR | S_IWUSR);
 428         if (res != 0) {
 429                 perror ("attach: failed to set permissions on IPC socket");
 430                 close (sock);
 431                 unlink (filename);
 432                 return;
 433         }
 434
 435         res = listen (sock, 16);
 436         if (res != 0) {
 437                 fprintf (stderr, "attach: listen () failed: %s\n", strerror (errno));
 438                 exit (1);
 439         }
 440
 441         listen_fd = sock;
 442
 443         ipc_filename = g_strdup (filename);
 444
 445         server_uri = g_strdup_printf ("unix://%s/.mono-%"PRIdMAX"?/vm", directory, (intmax_t) getpid ());
 446
 447         g_free (filename);
 448         g_free (directory);
 449 }
 450
 451 static void
 452 transport_connect (void)
 453 {
 454         ipc_connect ();
 455 }
 456
 457 #if 0
 458
 459 static void
 460 transport_send (int fd, guint8 *data, int len)
 461 {
 462         int res;
 463
 464         stats.bytes_sent += len;
 465         //printf ("X: %d\n", stats.bytes_sent);
 466
 467         res = write (fd, data, len);
 468         if (res != len) {
 469                 /* FIXME: What to do here ? */
 470         }
 471 }
 472
 473 #endif
 474
 475 static void
 476 transport_start_receive (void)
 477 {
 478         transport_connect ();
 479
 480         if (!listen_fd)
 481                 return;
 482
 483         receiver_thread_handle = mono_threads_create_thread (receiver_thread, NULL, 0, NULL);
 484         g_assert (receiver_thread_handle);
 485 }
 486
 487 static gsize WINAPI
 488 receiver_thread (void *arg)
 489 {
 490         MonoError error;
 491         int res, content_len;
 492         guint8 buffer [256];
 493         guint8 *p, *p_end;
 494         MonoObject *exc;
 495
 496         mono_native_thread_set_name (mono_native_thread_id_get (), "Attach receiver");
 497
 498         printf ("attach: Listening on '%s'...\n", server_uri);
 499
 500         while (TRUE) {
 501                 conn_fd = accept (listen_fd, NULL, NULL);
 502                 if (conn_fd == -1)
 503                         /* Probably closed by mono_attach_cleanup () */
 504                         return 0;
 505
 506                 printf ("attach: Connected.\n");
 507
 508                 MonoThread *thread = mono_thread_attach (mono_get_root_domain ());
 509                 mono_thread_set_name_internal (thread->internal_thread, mono_string_new (mono_get_root_domain (), "Attach receiver"), TRUE, &error);
 510                 mono_error_assert_ok (&error);
 511                 /* Ask the runtime to not abort this thread */
 512                 //mono_thread_current ()->flags |= MONO_THREAD_FLAG_DONT_MANAGE;
 513                 /* Ask the runtime to not wait for this thread */
 514                 thread->internal_thread->state |= ThreadState_Background;
 515
 516                 while (TRUE) {
 517                         char *cmd, *agent_name, *agent_args;
 518                         guint8 *body;
 519
 520                         /* Read Header */
 521                         res = read (conn_fd, buffer, 6);
 522
 523                         if (res == -1 && errno == EINTR)
 524                                 continue;
 525
 526                         if (res == -1 || stop_receiver_thread)
 527                                 break;
 528
 529                         if (res != 6)
 530                                 break;
 531
 532                         if ((strncmp ((char*)buffer, "MONO", 4) != 0) || buffer [4] != 1 || buffer [5] != 0) {
 533                                 fprintf (stderr, "attach: message from server has unknown header.\n");
 534                                 break;
 535                         }
 536
 537                         /* Read content length */
 538                         res = read (conn_fd, buffer, 4);
 539                         if (res != 4)
 540                                 break;
 541
 542                         p = buffer;
 543                         p_end = p + 8;
 544
 545                         content_len = decode_int (p, &p, p_end);
 546
 547                         /* Read message body */
 548                         body = (guint8 *)g_malloc (content_len);
 549                         res = read (conn_fd, body, content_len);
 550
 551                         p = body;
 552                         p_end = body + content_len;
 553
 554                         cmd = decode_string_value (p, &p, p_end);
 555                         if (cmd == NULL)
 556                                 break;
 557                         g_assert (!strcmp (cmd, "attach"));
 558
 559                         agent_name = decode_string_value (p, &p, p_end);
 560                         agent_args = decode_string_value (p, &p, p_end);
 561
 562                         printf ("attach: Loading agent '%s'.\n", agent_name);
 563                         mono_attach_load_agent (mono_domain_get (), agent_name, agent_args, &exc);
 564
 565                         g_free (body);
 566
 567                         // FIXME: Send back a result
 568                 }
 569
 570                 close (conn_fd);
 571                 conn_fd = 0;
 572
 573                 printf ("attach: Disconnected.\n");
 574
 575                 if (stop_receiver_thread)
 576                         break;
 577         }
 578
 579         return 0;
 580 }
 581
 582 #else /* DISABLE_ATTACH */
 583
 584 void
 585 mono_attach_parse_options (char *options)
 586 {
 587 }
 588
 589 void
 590 mono_attach_init (void)
 591 {
 592 }
 593
 594 gboolean
 595 mono_attach_start (void)
 596 {
 597         return FALSE;
 598 }
 599
 600 void
 601 mono_attach_maybe_start (void)
 602 {
 603 }
 604
 605 void
 606 mono_attach_cleanup (void)
 607 {
 608 }
 609
 610 #endif /* DISABLE_ATTACH */