src/common/runas.c

   1 /*
   2  * Copyright (C) 2011 - David Goulet <david.goulet@polymtl.ca>
   3  *                      Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License, version 2 only,
   7  * as published by the Free Software Foundation.
   8  *
   9  * This program is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
  12  * more details.
  13  *
  14  * You should have received a copy of the GNU General Public License along
  15  * with this program; if not, write to the Free Software Foundation, Inc.,
  16  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  17  */
  18
  19 #define _LGPL_SOURCE
  20 #include <errno.h>
  21 #include <limits.h>
  22 #include <stdio.h>
  23 #include <stdlib.h>
  24 #include <string.h>
  25 #include <sys/wait.h>
  26 #include <sys/types.h>
  27 #include <sys/stat.h>
  28 #include <unistd.h>
  29 #include <fcntl.h>
  30 #include <sched.h>
  31 #include <signal.h>
  32 #include <assert.h>
  33 #include <signal.h>
  34
  35 #include <common/lttng-kernel.h>
  36 #include <common/common.h>
  37 #include <common/utils.h>
  38 #include <common/compat/getenv.h>
  39 #include <common/compat/prctl.h>
  40 #include <common/unix.h>
  41 #include <common/defaults.h>
  42 #include <common/lttng-elf.h>
  43
  44 #include <lttng/constant.h>
  45
  46 #include "runas.h"
  47
  48 struct run_as_data;
  49 struct run_as_ret;
  50 typedef int (*run_as_fct)(struct run_as_data *data, struct run_as_ret *ret_value);
  51
  52 struct run_as_mkdir_data {
  53         char path[PATH_MAX];
  54         mode_t mode;
  55 };
  56
  57 struct run_as_open_data {
  58         char path[PATH_MAX];
  59         int flags;
  60         mode_t mode;
  61 };
  62
  63 struct run_as_unlink_data {
  64         char path[PATH_MAX];
  65 };
  66
  67 struct run_as_rmdir_recursive_data {
  68         char path[PATH_MAX];
  69 };
  70
  71 struct run_as_extract_elf_symbol_offset_data {
  72         char function[LTTNG_SYMBOL_NAME_LEN];
  73 };
  74
  75 struct run_as_extract_sdt_probe_offsets_data {
  76         char probe_name[LTTNG_SYMBOL_NAME_LEN];
  77         char provider_name[LTTNG_SYMBOL_NAME_LEN];
  78 };
  79
  80 struct run_as_mkdir_ret {
  81         int ret;
  82 };
  83
  84 struct run_as_open_ret {
  85         int ret;
  86 };
  87
  88 struct run_as_unlink_ret {
  89         int ret;
  90 };
  91
  92 struct run_as_rmdir_recursive_ret {
  93         int ret;
  94 };
  95
  96 struct run_as_extract_elf_symbol_offset_ret {
  97         uint64_t offset;
  98 };
  99
 100 struct run_as_extract_sdt_probe_offsets_ret {
 101         uint32_t num_offset;
 102         uint64_t offsets[LTTNG_KERNEL_MAX_UPROBE_NUM];
 103 };
 104
 105 enum run_as_cmd {
 106         RUN_AS_MKDIR,
 107         RUN_AS_OPEN,
 108         RUN_AS_UNLINK,
 109         RUN_AS_RMDIR_RECURSIVE,
 110         RUN_AS_MKDIR_RECURSIVE,
 111         RUN_AS_EXTRACT_ELF_SYMBOL_OFFSET,
 112         RUN_AS_EXTRACT_SDT_PROBE_OFFSETS,
 113 };
 114
 115 struct run_as_data {
 116         enum run_as_cmd cmd;
 117         int fd;
 118         union {
 119                 struct run_as_mkdir_data mkdir;
 120                 struct run_as_open_data open;
 121                 struct run_as_unlink_data unlink;
 122                 struct run_as_rmdir_recursive_data rmdir_recursive;
 123                 struct run_as_extract_elf_symbol_offset_data extract_elf_symbol_offset;
 124                 struct run_as_extract_sdt_probe_offsets_data extract_sdt_probe_offsets;
 125         } u;
 126         uid_t uid;
 127         gid_t gid;
 128 };
 129
 130 /*
 131  * The run_as_ret structure holds the returned value and status of the command.
 132  *
 133  * The `u` union field holds the return value of the command; in most cases it
 134  * represents the success or the failure of the command. In more complex
 135  * commands, it holds a computed value.
 136  *
 137  * The _errno field is the errno recorded after the execution of the command.
 138  *
 139  * The _error fields is used the signify that return status of the command. For
 140  * simple commands returning `int` the _error field will be the same as the
 141  * ret_int field. In complex commands, it signify the success or failure of the
 142  * command.
 143  *
 144  */
 145 struct run_as_ret {
 146         int fd;
 147         union {
 148                 struct run_as_mkdir_ret mkdir;
 149                 struct run_as_open_ret open;
 150                 struct run_as_unlink_ret unlink;
 151                 struct run_as_rmdir_recursive_ret rmdir_recursive;
 152                 struct run_as_extract_elf_symbol_offset_ret extract_elf_symbol_offset;
 153                 struct run_as_extract_sdt_probe_offsets_ret extract_sdt_probe_offsets;
 154         } u;
 155         int _errno;
 156         bool _error;
 157 };
 158
 159 struct run_as_worker {
 160         pid_t pid;      /* Worker PID. */
 161         int sockpair[2];
 162         char *procname;
 163 };
 164
 165 /* Single global worker per process (for now). */
 166 static struct run_as_worker *global_worker;
 167 /* Lock protecting the worker. */
 168 static pthread_mutex_t worker_lock = PTHREAD_MUTEX_INITIALIZER;
 169
 170 #ifdef VALGRIND
 171 static
 172 int use_clone(void)
 173 {
 174         return 0;
 175 }
 176 #else
 177 static
 178 int use_clone(void)
 179 {
 180         return !lttng_secure_getenv("LTTNG_DEBUG_NOCLONE");
 181 }
 182 #endif
 183
 184 LTTNG_HIDDEN
 185 int _utils_mkdir_recursive_unsafe(const char *path, mode_t mode);
 186
 187 /*
 188  * Create recursively directory using the FULL path.
 189  */
 190 static
 191 int _mkdir_recursive(struct run_as_data *data, struct run_as_ret *ret_value)
 192 {
 193         const char *path;
 194         mode_t mode;
 195
 196         path = data->u.mkdir.path;
 197         mode = data->u.mkdir.mode;
 198
 199         /* Safe to call as we have transitioned to the requested uid/gid. */
 200         ret_value->u.mkdir.ret = _utils_mkdir_recursive_unsafe(path, mode);
 201         ret_value->_errno = errno;
 202         ret_value->_error = (ret_value->u.mkdir.ret) ? true : false;
 203         return ret_value->u.mkdir.ret;
 204 }
 205
 206 static
 207 int _mkdir(struct run_as_data *data, struct run_as_ret *ret_value)
 208 {
 209         ret_value->u.mkdir.ret = mkdir(data->u.mkdir.path, data->u.mkdir.mode);
 210         ret_value->_errno = errno;
 211         ret_value->_error = (ret_value->u.mkdir.ret) ? true : false;
 212         return ret_value->u.mkdir.ret;
 213 }
 214
 215 static
 216 int _open(struct run_as_data *data, struct run_as_ret *ret_value)
 217 {
 218         ret_value->u.open.ret = open(data->u.open.path, data->u.open.flags, data->u.open.mode);
 219         ret_value->fd = ret_value->u.open.ret;
 220         ret_value->_errno = errno;
 221         ret_value->_error = ret_value->u.open.ret < 0;
 222         return ret_value->u.open.ret;
 223 }
 224
 225 static
 226 int _unlink(struct run_as_data *data, struct run_as_ret *ret_value)
 227 {
 228         ret_value->u.unlink.ret = unlink(data->u.unlink.path);
 229         ret_value->_errno = errno;
 230         ret_value->_error = (ret_value->u.unlink.ret) ? true : false;
 231         return ret_value->u.unlink.ret;
 232 }
 233
 234 static
 235 int _rmdir_recursive(struct run_as_data *data, struct run_as_ret *ret_value)
 236 {
 237         ret_value->u.rmdir_recursive.ret = utils_recursive_rmdir(data->u.rmdir_recursive.path);
 238         ret_value->_errno = errno;
 239         ret_value->_error = (ret_value->u.rmdir_recursive.ret) ? true : false;
 240         return ret_value->u.rmdir_recursive.ret;
 241 }
 242
 243 #ifdef HAVE_ELF_H
 244 static
 245 int _extract_elf_symbol_offset(struct run_as_data *data,
 246                 struct run_as_ret *ret_value)
 247 {
 248         int ret = 0;
 249         ret_value->_error = false;
 250
 251         ret = lttng_elf_get_symbol_offset(data->fd,
 252                          data->u.extract_elf_symbol_offset.function,
 253                          &ret_value->u.extract_elf_symbol_offset.offset);
 254         if (ret) {
 255                 DBG("Failed to extract ELF function offset");
 256                 ret_value->_error = true;
 257         }
 258
 259         return ret;
 260 }
 261
 262 static
 263 int _extract_sdt_probe_offsets(struct run_as_data *data,
 264                 struct run_as_ret *ret_value)
 265 {
 266         int ret = 0;
 267         uint64_t *offsets = NULL;
 268         uint32_t num_offset;
 269
 270         ret_value->_error = false;
 271
 272         /* On success, this call allocates the offsets paramater. */
 273         ret = lttng_elf_get_sdt_probe_offsets(data->fd,
 274                         data->u.extract_sdt_probe_offsets.provider_name,
 275                         data->u.extract_sdt_probe_offsets.probe_name,
 276                         &offsets, &num_offset);
 277
 278         if (ret) {
 279                 DBG("Failed to extract SDT probe offsets");
 280                 ret_value->_error = true;
 281                 goto end;
 282         }
 283
 284         if (num_offset <= 0 || num_offset > LTTNG_KERNEL_MAX_UPROBE_NUM) {
 285                 DBG("Wrong number of probes.");
 286                 ret = -1;
 287                 ret_value->_error = true;
 288                 goto free_offset;
 289         }
 290
 291         /* Copy the content of the offsets array to the ret struct. */
 292         memcpy(ret_value->u.extract_sdt_probe_offsets.offsets,
 293                         offsets, num_offset * sizeof(uint64_t));
 294
 295         ret_value->u.extract_sdt_probe_offsets.num_offset = num_offset;
 296
 297 free_offset:
 298         free(offsets);
 299 end:
 300         return ret;
 301 }
 302 #else
 303 static
 304 int _extract_elf_symbol_offset(struct run_as_data *data,
 305                 struct run_as_ret *ret_value)
 306 {
 307         ERR("Unimplemented runas command RUN_AS_EXTRACT_ELF_SYMBOL_OFFSET");
 308         return -1;
 309 }
 310
 311 static
 312 int _extract_sdt_probe_offsets(struct run_as_data *data,
 313                 struct run_as_ret *ret_value)
 314 {
 315         ERR("Unimplemented runas command RUN_AS_EXTRACT_SDT_PROBE_OFFSETS");
 316         return -1;
 317 }
 318 #endif
 319
 320 static
 321 run_as_fct run_as_enum_to_fct(enum run_as_cmd cmd)
 322 {
 323         switch (cmd) {
 324         case RUN_AS_MKDIR:
 325                 return _mkdir;
 326         case RUN_AS_OPEN:
 327                 return _open;
 328         case RUN_AS_UNLINK:
 329                 return _unlink;
 330         case RUN_AS_RMDIR_RECURSIVE:
 331                 return _rmdir_recursive;
 332         case RUN_AS_MKDIR_RECURSIVE:
 333                 return _mkdir_recursive;
 334         case RUN_AS_EXTRACT_ELF_SYMBOL_OFFSET:
 335                 return _extract_elf_symbol_offset;
 336         case RUN_AS_EXTRACT_SDT_PROBE_OFFSETS:
 337                 return _extract_sdt_probe_offsets;
 338         default:
 339                 ERR("Unknown command %d", (int) cmd);
 340                 return NULL;
 341         }
 342 }
 343
 344 static
 345 int do_send_fd(int sock, int fd)
 346 {
 347         ssize_t len;
 348
 349         if (fd < 0) {
 350                 ERR("Attempt to send invalid file descriptor to master (fd = %i)", fd);
 351                 /* Return 0 as this is not a fatal error. */
 352                 return 0;
 353         }
 354
 355         len = lttcomm_send_fds_unix_sock(sock, &fd, 1);
 356         if (len < 0) {
 357                 PERROR("lttcomm_send_fds_unix_sock");
 358                 return -1;
 359         }
 360         return 0;
 361 }
 362
 363 static
 364 int do_recv_fd(int sock, int *fd)
 365 {
 366         ssize_t len;
 367
 368         len = lttcomm_recv_fds_unix_sock(sock, fd, 1);
 369
 370         if (!len) {
 371                 return -1;
 372         } else if (len < 0) {
 373                 PERROR("lttcomm_recv_fds_unix_sock");
 374                 return -1;
 375         }
 376         if (*fd < 0) {
 377                 ERR("Invalid file descriptor received from worker (fd = %i)", *fd);
 378                 /* Return 0 as this is not a fatal error. */
 379                 return 0;
 380         }
 381
 382         return 0;
 383 }
 384
 385 static
 386 int send_fd_to_worker(struct run_as_worker *worker, enum run_as_cmd cmd, int fd)
 387 {
 388         int ret = 0;
 389
 390         switch (cmd) {
 391         case RUN_AS_EXTRACT_ELF_SYMBOL_OFFSET:
 392         case RUN_AS_EXTRACT_SDT_PROBE_OFFSETS:
 393                 break;
 394         default:
 395                 return 0;
 396         }
 397
 398         if (fd < 0) {
 399                 ERR("Refusing to send invalid fd to worker (fd = %i)", fd);
 400                 return -1;
 401         }
 402
 403         ret = do_send_fd(worker->sockpair[0], fd);
 404         if (ret < 0) {
 405                 PERROR("do_send_fd");
 406                 ret = -1;
 407         }
 408
 409         return ret;
 410 }
 411
 412 static
 413 int send_fd_to_master(struct run_as_worker *worker, enum run_as_cmd cmd, int fd)
 414 {
 415         int ret = 0, ret_close = 0;
 416
 417         switch (cmd) {
 418         case RUN_AS_OPEN:
 419                 break;
 420         default:
 421                 return 0;
 422         }
 423
 424         if (fd < 0) {
 425                 DBG("Not sending file descriptor to master as it is invalid (fd = %i)", fd);
 426                 return 0;
 427         }
 428         ret = do_send_fd(worker->sockpair[1], fd);
 429         if (ret < 0) {
 430                 PERROR("do_send_fd error");
 431                 ret = -1;
 432         }
 433
 434         ret_close = close(fd);
 435         if (ret_close < 0) {
 436                 PERROR("close");
 437         }
 438
 439         return ret;
 440 }
 441
 442 static
 443 int recv_fd_from_worker(struct run_as_worker *worker, enum run_as_cmd cmd, int *fd)
 444 {
 445         int ret = 0;
 446
 447         switch (cmd) {
 448         case RUN_AS_OPEN:
 449                 break;
 450         default:
 451                 return 0;
 452         }
 453
 454         ret = do_recv_fd(worker->sockpair[0], fd);
 455         if (ret < 0) {
 456                 PERROR("do_recv_fd error");
 457                 ret = -1;
 458         }
 459
 460         return ret;
 461 }
 462
 463 static
 464 int recv_fd_from_master(struct run_as_worker *worker, enum run_as_cmd cmd, int *fd)
 465 {
 466         int ret = 0;
 467
 468         switch (cmd) {
 469         case RUN_AS_EXTRACT_ELF_SYMBOL_OFFSET:
 470         case RUN_AS_EXTRACT_SDT_PROBE_OFFSETS:
 471                 break;
 472         default:
 473                 return 0;
 474         }
 475
 476         ret = do_recv_fd(worker->sockpair[1], fd);
 477         if (ret < 0) {
 478                 PERROR("do_recv_fd error");
 479                 ret = -1;
 480         }
 481
 482         return ret;
 483 }
 484
 485 static
 486 int cleanup_received_fd(enum run_as_cmd cmd, int fd)
 487 {
 488         int ret = 0;
 489
 490         switch (cmd) {
 491         case RUN_AS_EXTRACT_ELF_SYMBOL_OFFSET:
 492         case RUN_AS_EXTRACT_SDT_PROBE_OFFSETS:
 493                 break;
 494         default:
 495                 return 0;
 496         }
 497
 498         if (fd < 0) {
 499                 return 0;
 500         }
 501         ret = close(fd);
 502         if (ret < 0) {
 503                 PERROR("close error");
 504                 ret = -1;
 505         }
 506
 507         return ret;
 508 }
 509
 510 /*
 511  * Return < 0 on error, 0 if OK, 1 on hangup.
 512  */
 513 static
 514 int handle_one_cmd(struct run_as_worker *worker)
 515 {
 516         int ret = 0;
 517         struct run_as_data data;
 518         ssize_t readlen, writelen;
 519         struct run_as_ret sendret;
 520         run_as_fct cmd;
 521         uid_t prev_euid;
 522
 523         memset(&sendret, 0, sizeof(sendret));
 524         sendret.fd = -1;
 525
 526         /*
 527          * Stage 1: Receive run_as_data struct from the master.
 528          * The structure contains the command type and all the parameters needed for
 529          * its execution
 530          */
 531         readlen = lttcomm_recv_unix_sock(worker->sockpair[1], &data,
 532                         sizeof(data));
 533         if (readlen == 0) {
 534                 /* hang up */
 535                 ret = 1;
 536                 goto end;
 537         }
 538         if (readlen < sizeof(data)) {
 539                 PERROR("lttcomm_recv_unix_sock error");
 540                 ret = -1;
 541                 goto end;
 542         }
 543
 544         cmd = run_as_enum_to_fct(data.cmd);
 545         if (!cmd) {
 546                 ret = -1;
 547                 goto end;
 548         }
 549
 550         /*
 551          * Stage 2: Receive file descriptor from master.
 552          * Some commands need a file descriptor as input so if it's needed we
 553          * receive the fd using the Unix socket.
 554          */
 555         ret = recv_fd_from_master(worker, data.cmd, &data.fd);
 556         if (ret < 0) {
 557                 PERROR("recv_fd_from_master error");
 558                 ret = -1;
 559                 goto end;
 560         }
 561
 562         prev_euid = getuid();
 563         if (data.gid != getegid()) {
 564                 ret = setegid(data.gid);
 565                 if (ret < 0) {
 566                         sendret._error = true;
 567                         sendret._errno = errno;
 568                         PERROR("setegid");
 569                         goto write_return;
 570                 }
 571         }
 572         if (data.uid != prev_euid) {
 573                 ret = seteuid(data.uid);
 574                 if (ret < 0) {
 575                         sendret._error = true;
 576                         sendret._errno = errno;
 577                         PERROR("seteuid");
 578                         goto write_return;
 579                 }
 580         }
 581
 582         /*
 583          * Also set umask to 0 for mkdir executable bit.
 584          */
 585         umask(0);
 586
 587         /*
 588          * Stage 3: Execute the command
 589          */
 590         ret = (*cmd)(&data, &sendret);
 591         if (ret < 0) {
 592                 DBG("Execution of command returned an error");
 593         }
 594
 595 write_return:
 596         ret = cleanup_received_fd(data.cmd, data.fd);
 597         if (ret < 0) {
 598                 ERR("Error cleaning up FD");
 599                 goto end;
 600         }
 601
 602         /*
 603          * Stage 4: Send run_as_ret structure to the master.
 604          * This structure contain the return value of the command and the errno.
 605          */
 606         writelen = lttcomm_send_unix_sock(worker->sockpair[1], &sendret,
 607                         sizeof(sendret));
 608         if (writelen < sizeof(sendret)) {
 609                 PERROR("lttcomm_send_unix_sock error");
 610                 ret = -1;
 611                 goto end;
 612         }
 613
 614         /*
 615          * Stage 5: Send file descriptor to the master
 616          * Some commands return a file descriptor so if it's needed we pass it back
 617          * to the master using the Unix socket.
 618          */
 619         ret = send_fd_to_master(worker, data.cmd, sendret.fd);
 620         if (ret < 0) {
 621                 DBG("Sending FD to master returned an error");
 622                 goto end;
 623         }
 624
 625         if (seteuid(prev_euid) < 0) {
 626                 PERROR("seteuid");
 627                 ret = -1;
 628                 goto end;
 629         }
 630         ret = 0;
 631 end:
 632         return ret;
 633 }
 634
 635 static
 636 int run_as_worker(struct run_as_worker *worker)
 637 {
 638         int ret;
 639         ssize_t writelen;
 640         struct run_as_ret sendret;
 641         size_t proc_orig_len;
 642
 643         /*
 644          * Initialize worker. Set a different process cmdline.
 645          */
 646         proc_orig_len = strlen(worker->procname);
 647         memset(worker->procname, 0, proc_orig_len);
 648         strncpy(worker->procname, DEFAULT_RUN_AS_WORKER_NAME, proc_orig_len);
 649
 650         ret = lttng_prctl(PR_SET_NAME,
 651                         (unsigned long) DEFAULT_RUN_AS_WORKER_NAME, 0, 0, 0);
 652         if (ret && ret != -ENOSYS) {
 653                 /* Don't fail as this is not essential. */
 654                 PERROR("prctl PR_SET_NAME");
 655         }
 656
 657         memset(&sendret, 0, sizeof(sendret));
 658
 659         writelen = lttcomm_send_unix_sock(worker->sockpair[1], &sendret,
 660                         sizeof(sendret));
 661         if (writelen < sizeof(sendret)) {
 662                 PERROR("lttcomm_send_unix_sock error");
 663                 ret = EXIT_FAILURE;
 664                 goto end;
 665         }
 666
 667         for (;;) {
 668                 ret = handle_one_cmd(worker);
 669                 if (ret < 0) {
 670                         ret = EXIT_FAILURE;
 671                         goto end;
 672                 } else if (ret > 0) {
 673                         break;
 674                 } else {
 675                         continue;       /* Next command. */
 676                 }
 677         }
 678         ret = EXIT_SUCCESS;
 679 end:
 680         return ret;
 681 }
 682
 683 static
 684 int run_as_cmd(struct run_as_worker *worker,
 685                 enum run_as_cmd cmd,
 686                 struct run_as_data *data,
 687                 struct run_as_ret *ret_value,
 688                 uid_t uid, gid_t gid)
 689 {
 690         int ret = 0;
 691         ssize_t readlen, writelen;
 692
 693         /*
 694          * If we are non-root, we can only deal with our own uid.
 695          */
 696         if (geteuid() != 0) {
 697                 if (uid != geteuid()) {
 698                         ret = -1;
 699                         ret_value->_errno = EPERM;
 700                         ERR("Client (%d)/Server (%d) UID mismatch (and sessiond is not root)",
 701                                 (int) uid, (int) geteuid());
 702                         goto end;
 703                 }
 704         }
 705
 706         data->cmd = cmd;
 707         data->uid = uid;
 708         data->gid = gid;
 709
 710         /*
 711          * Stage 1: Send the run_as_data struct to the worker process
 712          */
 713         writelen = lttcomm_send_unix_sock(worker->sockpair[0], data,
 714                         sizeof(*data));
 715         if (writelen < sizeof(*data)) {
 716                 PERROR("Error writing message to run_as");
 717                 ret = -1;
 718                 ret_value->_errno = EIO;
 719                 goto end;
 720         }
 721
 722         /*
 723          * Stage 2: Send file descriptor to the worker process if needed
 724          */
 725         ret = send_fd_to_worker(worker, data->cmd, data->fd);
 726         if (ret) {
 727                 PERROR("do_send_fd error");
 728                 ret = -1;
 729                 ret_value->_errno = EIO;
 730                 goto end;
 731         }
 732
 733         /*
 734          * Stage 3: Wait for the execution of the command
 735          */
 736
 737         /*
 738          * Stage 4: Receive the run_as_ret struct containing the return value and
 739          * errno
 740          */
 741         readlen = lttcomm_recv_unix_sock(worker->sockpair[0], ret_value,
 742                         sizeof(*ret_value));
 743         if (!readlen) {
 744                 ERR("Run-as worker has hung-up during run_as_cmd");
 745                 ret = -1;
 746                 ret_value->_errno = EIO;
 747                 goto end;
 748         } else if (readlen < sizeof(*ret_value)) {
 749                 PERROR("Error reading response from run_as");
 750                 ret = -1;
 751                 ret_value->_errno = errno;
 752                 goto end;
 753         }
 754
 755         if (ret_value->_error) {
 756                 /* Skip stage 5 on error as there will be no fd to receive. */
 757                 goto end;
 758         }
 759
 760         /*
 761          * Stage 5: Receive file descriptor if needed
 762          */
 763         ret = recv_fd_from_worker(worker, data->cmd, &ret_value->fd);
 764         if (ret < 0) {
 765                 ERR("Error receiving fd");
 766                 ret = -1;
 767                 ret_value->_errno = EIO;
 768         }
 769
 770 end:
 771         return ret;
 772 }
 773
 774 /*
 775  * This is for debugging ONLY and should not be considered secure.
 776  */
 777 static
 778 int run_as_noworker(enum run_as_cmd cmd,
 779                 struct run_as_data *data, struct run_as_ret *ret_value,
 780                 uid_t uid, gid_t gid)
 781 {
 782         int ret, saved_errno;
 783         mode_t old_mask;
 784         run_as_fct fct;
 785
 786         fct = run_as_enum_to_fct(cmd);
 787         if (!fct) {
 788                 errno = -ENOSYS;
 789                 ret = -1;
 790                 goto end;
 791         }
 792         old_mask = umask(0);
 793         ret = fct(data, ret_value);
 794         saved_errno = ret_value->_errno;
 795         umask(old_mask);
 796         errno = saved_errno;
 797 end:
 798         return ret;
 799 }
 800
 801 static
 802 int reset_sighandler(void)
 803 {
 804         int sig;
 805
 806         DBG("Resetting run_as worker signal handlers to default");
 807         for (sig = 1; sig <= 31; sig++) {
 808                 (void) signal(sig, SIG_DFL);
 809         }
 810         return 0;
 811 }
 812
 813 static
 814 void worker_sighandler(int sig)
 815 {
 816         const char *signame;
 817
 818         /*
 819          * The worker will inherit its parent's signals since they are part of
 820          * the same process group. However, in the case of SIGINT and SIGTERM,
 821          * we want to give the worker a chance to teardown gracefully when its
 822          * parent closes the command socket.
 823          */
 824         switch (sig) {
 825         case SIGINT:
 826                 signame = "SIGINT";
 827                 break;
 828         case SIGTERM:
 829                 signame = "SIGTERM";
 830                 break;
 831         default:
 832                 signame = NULL;
 833         }
 834
 835         if (signame) {
 836                 DBG("run_as worker received signal %s", signame);
 837         } else {
 838                 DBG("run_as_worker received signal %d", sig);
 839         }
 840 }
 841
 842 static
 843 int set_worker_sighandlers(void)
 844 {
 845         int ret = 0;
 846         sigset_t sigset;
 847         struct sigaction sa;
 848
 849         if ((ret = sigemptyset(&sigset)) < 0) {
 850                 PERROR("sigemptyset");
 851                 goto end;
 852         }
 853
 854         sa.sa_handler = worker_sighandler;
 855         sa.sa_mask = sigset;
 856         sa.sa_flags = 0;
 857         if ((ret = sigaction(SIGINT, &sa, NULL)) < 0) {
 858                 PERROR("sigaction SIGINT");
 859                 goto end;
 860         }
 861
 862         if ((ret = sigaction(SIGTERM, &sa, NULL)) < 0) {
 863                 PERROR("sigaction SIGTERM");
 864                 goto end;
 865         }
 866
 867         DBG("run_as signal handler set for SIGTERM and SIGINT");
 868 end:
 869         return ret;
 870 }
 871
 872 static
 873 int run_as_create_worker_no_lock(const char *procname)
 874 {
 875         pid_t pid;
 876         int i, ret = 0;
 877         ssize_t readlen;
 878         struct run_as_ret recvret;
 879         struct run_as_worker *worker;
 880
 881         assert(!global_worker);
 882         if (!use_clone()) {
 883                 /*
 884                  * Don't initialize a worker, all run_as tasks will be performed
 885                  * in the current process.
 886                  */
 887                 ret = 0;
 888                 goto end;
 889         }
 890         worker = zmalloc(sizeof(*worker));
 891         if (!worker) {
 892                 ret = -ENOMEM;
 893                 goto end;
 894         }
 895         worker->procname = strdup(procname);
 896         if (!worker->procname) {
 897                 ret = -ENOMEM;
 898                 goto error_procname_alloc;
 899         }
 900         /* Create unix socket. */
 901         if (lttcomm_create_anon_unix_socketpair(worker->sockpair) < 0) {
 902                 ret = -1;
 903                 goto error_sock;
 904         }
 905
 906         /* Fork worker. */
 907         pid = fork();
 908         if (pid < 0) {
 909                 PERROR("fork");
 910                 ret = -1;
 911                 goto error_fork;
 912         } else if (pid == 0) {
 913                 /* Child */
 914
 915                 reset_sighandler();
 916
 917                 set_worker_sighandlers();
 918
 919                 /* Just close, no shutdown. */
 920                 if (close(worker->sockpair[0])) {
 921                         PERROR("close");
 922                         exit(EXIT_FAILURE);
 923                 }
 924
 925                 /*
 926                  * Close all FDs aside from STDIN, STDOUT, STDERR and sockpair[1]
 927                  * Sockpair[1] is used as a control channel with the master
 928                  */
 929                 for (i = 3; i < sysconf(_SC_OPEN_MAX); i++) {
 930                         if (i != worker->sockpair[1]) {
 931                                 (void) close(i);
 932                         }
 933                 }
 934
 935                 worker->sockpair[0] = -1;
 936                 ret = run_as_worker(worker);
 937                 if (lttcomm_close_unix_sock(worker->sockpair[1])) {
 938                         PERROR("close");
 939                         ret = -1;
 940                 }
 941                 worker->sockpair[1] = -1;
 942                 free(worker->procname);
 943                 free(worker);
 944                 LOG(ret ? PRINT_ERR : PRINT_DBG, "run_as worker exiting (ret = %d)", ret);
 945                 exit(ret ? EXIT_FAILURE : EXIT_SUCCESS);
 946         } else {
 947                 /* Parent */
 948
 949                 /* Just close, no shutdown. */
 950                 if (close(worker->sockpair[1])) {
 951                         PERROR("close");
 952                         ret = -1;
 953                         goto error_fork;
 954                 }
 955                 worker->sockpair[1] = -1;
 956                 worker->pid = pid;
 957                 /* Wait for worker to become ready. */
 958                 readlen = lttcomm_recv_unix_sock(worker->sockpair[0],
 959                                 &recvret, sizeof(recvret));
 960                 if (readlen < sizeof(recvret)) {
 961                         ERR("readlen: %zd", readlen);
 962                         PERROR("Error reading response from run_as at creation");
 963                         ret = -1;
 964                         goto error_fork;
 965                 }
 966                 global_worker = worker;
 967         }
 968 end:
 969         return ret;
 970
 971         /* Error handling. */
 972 error_fork:
 973         for (i = 0; i < 2; i++) {
 974                 if (worker->sockpair[i] < 0) {
 975                         continue;
 976                 }
 977                 if (lttcomm_close_unix_sock(worker->sockpair[i])) {
 978                         PERROR("close");
 979                 }
 980                 worker->sockpair[i] = -1;
 981         }
 982 error_sock:
 983         free(worker->procname);
 984 error_procname_alloc:
 985         free(worker);
 986         return ret;
 987 }
 988
 989 static
 990 int run_as_restart_worker(struct run_as_worker *worker)
 991 {
 992         int ret = 0;
 993         char *procname = NULL;
 994
 995         procname = worker->procname;
 996
 997         /* Close socket to run_as worker process and clean up the zombie process */
 998         run_as_destroy_worker();
 999
1000         /* Create a new run_as worker process*/
1001         ret = run_as_create_worker_no_lock(procname);
1002         if (ret < 0 ) {
1003                 ERR("Restarting the worker process failed");
1004                 ret = -1;
1005                 goto err;
1006         }
1007 err:
1008         return ret;
1009 }
1010
1011 static
1012 int run_as(enum run_as_cmd cmd, struct run_as_data *data,
1013                    struct run_as_ret *ret_value, uid_t uid, gid_t gid)
1014 {
1015         int ret, saved_errno;
1016
1017         pthread_mutex_lock(&worker_lock);
1018         if (use_clone()) {
1019                 DBG("Using run_as worker");
1020
1021                 assert(global_worker);
1022
1023                 ret = run_as_cmd(global_worker, cmd, data, ret_value, uid, gid);
1024                 saved_errno = ret_value->_errno;
1025
1026                 /*
1027                  * If the worker thread crashed the errno is set to EIO. we log
1028                  * the error and  start a new worker process.
1029                  */
1030                 if (ret == -1 && saved_errno == EIO) {
1031                         DBG("Socket closed unexpectedly... "
1032                                         "Restarting the worker process");
1033                         ret = run_as_restart_worker(global_worker);
1034                         if (ret == -1) {
1035                                 ERR("Failed to restart worker process.");
1036                                 goto err;
1037                         }
1038                 }
1039         } else {
1040                 DBG("Using run_as without worker");
1041                 ret = run_as_noworker(cmd, data, ret_value, uid, gid);
1042         }
1043 err:
1044         pthread_mutex_unlock(&worker_lock);
1045         return ret;
1046 }
1047
1048 LTTNG_HIDDEN
1049 int run_as_mkdir_recursive(const char *path, mode_t mode, uid_t uid, gid_t gid)
1050 {
1051         struct run_as_data data;
1052         struct run_as_ret ret;
1053
1054         memset(&data, 0, sizeof(data));
1055         memset(&ret, 0, sizeof(ret));
1056         DBG3("mkdir() recursive %s with mode %d for uid %d and gid %d",
1057                         path, (int) mode, (int) uid, (int) gid);
1058         strncpy(data.u.mkdir.path, path, PATH_MAX - 1);
1059         data.u.mkdir.path[PATH_MAX - 1] = '\0';
1060         data.u.mkdir.mode = mode;
1061
1062         run_as(RUN_AS_MKDIR_RECURSIVE, &data, &ret, uid, gid);
1063         errno = ret._errno;
1064         return ret.u.mkdir.ret;
1065 }
1066
1067 LTTNG_HIDDEN
1068 int run_as_mkdir(const char *path, mode_t mode, uid_t uid, gid_t gid)
1069 {
1070         struct run_as_data data;
1071         struct run_as_ret ret;
1072
1073         memset(&data, 0, sizeof(data));
1074         memset(&ret, 0, sizeof(ret));
1075
1076         DBG3("mkdir() %s with mode %d for uid %d and gid %d",
1077                         path, (int) mode, (int) uid, (int) gid);
1078         strncpy(data.u.mkdir.path, path, PATH_MAX - 1);
1079         data.u.mkdir.path[PATH_MAX - 1] = '\0';
1080         data.u.mkdir.mode = mode;
1081         run_as(RUN_AS_MKDIR, &data, &ret, uid, gid);
1082         errno = ret._errno;
1083         return ret.u.mkdir.ret;
1084 }
1085
1086 LTTNG_HIDDEN
1087 int run_as_open(const char *path, int flags, mode_t mode, uid_t uid, gid_t gid)
1088 {
1089         struct run_as_data data;
1090         struct run_as_ret ret;
1091
1092         memset(&data, 0, sizeof(data));
1093         memset(&ret, 0, sizeof(ret));
1094
1095         DBG3("open() %s with flags %X mode %d for uid %d and gid %d",
1096                         path, flags, (int) mode, (int) uid, (int) gid);
1097         strncpy(data.u.open.path, path, PATH_MAX - 1);
1098         data.u.open.path[PATH_MAX - 1] = '\0';
1099         data.u.open.flags = flags;
1100         data.u.open.mode = mode;
1101         run_as(RUN_AS_OPEN, &data, &ret, uid, gid);
1102         errno = ret._errno;
1103         ret.u.open.ret = ret.fd;
1104         return ret.u.open.ret;
1105 }
1106
1107 LTTNG_HIDDEN
1108 int run_as_unlink(const char *path, uid_t uid, gid_t gid)
1109 {
1110         struct run_as_data data;
1111         struct run_as_ret ret;
1112
1113         memset(&data, 0, sizeof(data));
1114         memset(&ret, 0, sizeof(ret));
1115
1116         DBG3("unlink() %s with for uid %d and gid %d",
1117                         path, (int) uid, (int) gid);
1118         strncpy(data.u.unlink.path, path, PATH_MAX - 1);
1119         data.u.unlink.path[PATH_MAX - 1] = '\0';
1120         run_as(RUN_AS_UNLINK, &data, &ret, uid, gid);
1121         errno = ret._errno;
1122         return ret.u.unlink.ret;
1123 }
1124
1125 LTTNG_HIDDEN
1126 int run_as_rmdir_recursive(const char *path, uid_t uid, gid_t gid)
1127 {
1128         struct run_as_data data;
1129         struct run_as_ret ret;
1130
1131         memset(&data, 0, sizeof(data));
1132         memset(&ret, 0, sizeof(ret));
1133
1134         DBG3("rmdir_recursive() %s with for uid %d and gid %d",
1135                         path, (int) uid, (int) gid);
1136         strncpy(data.u.rmdir_recursive.path, path, PATH_MAX - 1);
1137         data.u.rmdir_recursive.path[PATH_MAX - 1] = '\0';
1138         run_as(RUN_AS_RMDIR_RECURSIVE, &data, &ret, uid, gid);
1139         errno = ret._errno;
1140         return ret.u.rmdir_recursive.ret;
1141 }
1142
1143 LTTNG_HIDDEN
1144 int run_as_extract_elf_symbol_offset(int fd, const char* function,
1145                 uid_t uid, gid_t gid, uint64_t *offset)
1146 {
1147         struct run_as_data data;
1148         struct run_as_ret ret;
1149
1150         memset(&data, 0, sizeof(data));
1151         memset(&ret, 0, sizeof(ret));
1152
1153         DBG3("extract_elf_symbol_offset() on fd=%d and function=%s "
1154                 "with for uid %d and gid %d", fd, function, (int) uid, (int) gid);
1155
1156         data.fd = fd;
1157
1158         strncpy(data.u.extract_elf_symbol_offset.function, function, LTTNG_SYMBOL_NAME_LEN - 1);
1159
1160         data.u.extract_elf_symbol_offset.function[LTTNG_SYMBOL_NAME_LEN - 1] = '\0';
1161
1162         run_as(RUN_AS_EXTRACT_ELF_SYMBOL_OFFSET, &data, &ret, uid, gid);
1163
1164         errno = ret._errno;
1165
1166         if (ret._error) {
1167                 return -1;
1168         }
1169
1170         *offset = ret.u.extract_elf_symbol_offset.offset;
1171         return 0;
1172 }
1173
1174 LTTNG_HIDDEN
1175 int run_as_extract_sdt_probe_offsets(int fd, const char* provider_name,
1176                 const char* probe_name, uid_t uid, gid_t gid,
1177                 uint64_t **offsets, uint32_t *num_offset)
1178 {
1179         struct run_as_data data;
1180         struct run_as_ret ret;
1181
1182         memset(&data, 0, sizeof(data));
1183         memset(&ret, 0, sizeof(ret));
1184
1185         DBG3("extract_sdt_probe_offsets() on fd=%d, probe_name=%s and "
1186                 "provider_name=%s with for uid %d and gid %d", fd, probe_name,
1187                 provider_name, (int) uid, (int) gid);
1188
1189         data.fd = fd;
1190
1191         strncpy(data.u.extract_sdt_probe_offsets.probe_name, probe_name, LTTNG_SYMBOL_NAME_LEN - 1);
1192         strncpy(data.u.extract_sdt_probe_offsets.provider_name, provider_name, LTTNG_SYMBOL_NAME_LEN - 1);
1193
1194         data.u.extract_sdt_probe_offsets.probe_name[LTTNG_SYMBOL_NAME_LEN - 1] = '\0';
1195         data.u.extract_sdt_probe_offsets.provider_name[LTTNG_SYMBOL_NAME_LEN - 1] = '\0';
1196
1197         run_as(RUN_AS_EXTRACT_SDT_PROBE_OFFSETS, &data, &ret, uid, gid);
1198
1199         errno = ret._errno;
1200
1201         if (ret._error) {
1202                 return -1;
1203         }
1204
1205         *num_offset = ret.u.extract_sdt_probe_offsets.num_offset;
1206
1207         *offsets = zmalloc(*num_offset * sizeof(uint64_t));
1208         if (!*offsets) {
1209                 return -ENOMEM;
1210         }
1211
1212         memcpy(*offsets, ret.u.extract_sdt_probe_offsets.offsets, *num_offset * sizeof(uint64_t));
1213         return 0;
1214 }
1215
1216 LTTNG_HIDDEN
1217 int run_as_create_worker(const char *procname)
1218 {
1219         int ret;
1220
1221         pthread_mutex_lock(&worker_lock);
1222         ret = run_as_create_worker_no_lock(procname);
1223         pthread_mutex_unlock(&worker_lock);
1224         return ret;
1225 }
1226
1227 LTTNG_HIDDEN
1228 void run_as_destroy_worker(void)
1229 {
1230         struct run_as_worker *worker = global_worker;
1231
1232         DBG("Destroying run_as worker");
1233         pthread_mutex_lock(&worker_lock);
1234         if (!worker) {
1235                 goto end;
1236         }
1237         /* Close unix socket */
1238         DBG("Closing run_as worker socket");
1239         if (lttcomm_close_unix_sock(worker->sockpair[0])) {
1240                 PERROR("close");
1241         }
1242         worker->sockpair[0] = -1;
1243         /* Wait for worker. */
1244         for (;;) {
1245                 int status;
1246                 pid_t wait_ret;
1247
1248                 wait_ret = waitpid(worker->pid, &status, 0);
1249                 if (wait_ret < 0) {
1250                         if (errno == EINTR) {
1251                                 continue;
1252                         }
1253                         PERROR("waitpid");
1254                         break;
1255                 }
1256
1257                 if (WIFEXITED(status)) {
1258                         LOG(WEXITSTATUS(status) == 0 ? PRINT_DBG : PRINT_ERR,
1259                                         DEFAULT_RUN_AS_WORKER_NAME " terminated with status code %d",
1260                                         WEXITSTATUS(status));
1261                         break;
1262                 } else if (WIFSIGNALED(status)) {
1263                         ERR(DEFAULT_RUN_AS_WORKER_NAME " was killed by signal %d",
1264                                         WTERMSIG(status));
1265                         break;
1266                 }
1267         }
1268         free(worker->procname);
1269         free(worker);
1270         global_worker = NULL;
1271 end:
1272         pthread_mutex_unlock(&worker_lock);
1273 }