src/pam-module.c

   1 /*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
   2
   3 /***
   4   This file is part of systemd.
   5
   6   Copyright 2010 Lennart Poettering
   7
   8   systemd is free software; you can redistribute it and/or modify it
   9   under the terms of the GNU General Public License as published by
  10   the Free Software Foundation; either version 2 of the License, or
  11   (at your option) any later version.
  12
  13   systemd is distributed in the hope that it will be useful, but
  14   WITHOUT ANY WARRANTY; without even the implied warranty of
  15   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  16   General Public License for more details.
  17
  18   You should have received a copy of the GNU General Public License
  19   along with systemd; If not, see <http://www.gnu.org/licenses/>.
  20 ***/
  21
  22 #include <errno.h>
  23 #include <fcntl.h>
  24 #include <sys/file.h>
  25 #include <pwd.h>
  26 #include <endian.h>
  27
  28 #include <security/pam_modules.h>
  29 #include <security/_pam_macros.h>
  30 #include <security/pam_modutil.h>
  31 #include <security/pam_ext.h>
  32 #include <security/pam_misc.h>
  33
  34 #include "util.h"
  35 #include "cgroup-util.h"
  36 #include "macro.h"
  37 #include "sd-daemon.h"
  38 #include "strv.h"
  39
  40 static int parse_argv(pam_handle_t *handle,
  41                       int argc, const char **argv,
  42                       bool *create_session,
  43                       bool *kill_session,
  44                       bool *kill_user,
  45                       bool *keep_root,
  46                       char ***controllers,
  47                       char ***reset_controllers) {
  48
  49         unsigned i;
  50         bool reset_controller_set = false;
  51
  52         assert(argc >= 0);
  53         assert(argc == 0 || argv);
  54
  55         for (i = 0; i < (unsigned) argc; i++) {
  56                 int k;
  57
  58                 if (startswith(argv[i], "create-session=")) {
  59                         if ((k = parse_boolean(argv[i] + 15)) < 0) {
  60                                 pam_syslog(handle, LOG_ERR, "Failed to parse create-session= argument.");
  61                                 return k;
  62                         }
  63
  64                         if (create_session)
  65                                 *create_session = k;
  66
  67                 } else if (startswith(argv[i], "kill-session=")) {
  68                         if ((k = parse_boolean(argv[i] + 13)) < 0) {
  69                                 pam_syslog(handle, LOG_ERR, "Failed to parse kill-session= argument.");
  70                                 return k;
  71                         }
  72
  73                         if (kill_session)
  74                                 *kill_session = k;
  75
  76                 } else if (startswith(argv[i], "kill-user=")) {
  77                         if ((k = parse_boolean(argv[i] + 10)) < 0) {
  78                                 pam_syslog(handle, LOG_ERR, "Failed to parse kill-user= argument.");
  79                                 return k;
  80                         }
  81
  82                         if (kill_user)
  83                                 *kill_user = k;
  84
  85                 } else if (startswith(argv[i], "keep-root=")) {
  86                         if ((k = parse_boolean(argv[i] + 10)) < 0) {
  87                                 pam_syslog(handle, LOG_ERR, "Failed to parse keep-root= argument.");
  88                                 return k;
  89                         }
  90
  91                         if (keep_root)
  92                                 *keep_root = k;
  93
  94                 } else if (startswith(argv[i], "controllers=")) {
  95
  96                         if (controllers) {
  97                                 char **l;
  98
  99                                 if (!(l = strv_split(argv[i] + 12, ","))) {
 100                                         pam_syslog(handle, LOG_ERR, "Out of memory.");
 101                                         return -ENOMEM;
 102                                 }
 103
 104                                 strv_free(*controllers);
 105                                 *controllers = l;
 106                         }
 107
 108                 } else if (startswith(argv[i], "reset-controllers=")) {
 109
 110                         if (reset_controllers) {
 111                                 char **l;
 112
 113                                 if (!(l = strv_split(argv[i] + 18, ","))) {
 114                                         pam_syslog(handle, LOG_ERR, "Out of memory.");
 115                                         return -ENOMEM;
 116                                 }
 117
 118                                 strv_free(*reset_controllers);
 119                                 *reset_controllers = l;
 120                         }
 121
 122                         reset_controller_set = true;
 123
 124                 } else {
 125                         pam_syslog(handle, LOG_ERR, "Unknown parameter '%s'.", argv[i]);
 126                         return -EINVAL;
 127                 }
 128         }
 129
 130         if (!reset_controller_set && reset_controllers) {
 131                 char **l;
 132
 133                 if (!(l = strv_new("cpu", NULL))) {
 134                         pam_syslog(handle, LOG_ERR, "Out of memory");
 135                         return -ENOMEM;
 136                 }
 137
 138                 *reset_controllers = l;
 139         }
 140
 141         if (controllers)
 142                 strv_remove(*controllers, "name=systemd");
 143
 144         if (reset_controllers)
 145                 strv_remove(*reset_controllers, "name=systemd");
 146
 147         if (kill_session && *kill_session && kill_user)
 148                 *kill_user = true;
 149
 150         return 0;
 151 }
 152
 153 static int open_file_and_lock(const char *fn) {
 154         int fd;
 155
 156         assert(fn);
 157
 158         if ((fd = open(fn, O_RDWR|O_CLOEXEC|O_NOCTTY|O_NOFOLLOW|O_CREAT, 0600)) < 0)
 159                 return -errno;
 160
 161         /* The BSD socket semantics are a lot nicer than those of
 162          * POSIX locks. Which is why we use flock() here. BSD locking
 163          * does not work across NFS which however is not needed here
 164          * as the filesystems in question should be local, and only
 165          * locally accessible, and most likely even tmpfs. */
 166
 167         if (flock(fd, LOCK_EX) < 0)
 168                 return -errno;
 169
 170         return fd;
 171 }
 172
 173 enum {
 174         SESSION_ID_AUDIT = 'a',
 175         SESSION_ID_COUNTER = 'c',
 176         SESSION_ID_RANDOM = 'r'
 177 };
 178
 179 static uint64_t get_session_id(int *mode) {
 180         char *s;
 181         int fd;
 182
 183         assert(mode);
 184
 185         /* First attempt: let's use the session ID of the audit
 186          * system, if it is available. */
 187         if (read_one_line_file("/proc/self/sessionid", &s) >= 0) {
 188                 uint32_t u;
 189                 int r;
 190
 191                 r = safe_atou32(s, &u);
 192                 free(s);
 193
 194                 if (r >= 0 && u != (uint32_t) -1 && u > 0) {
 195                         *mode = SESSION_ID_AUDIT;
 196                         return (uint64_t) u;
 197                 }
 198         }
 199
 200         /* Second attempt, use our own counter. */
 201         if ((fd = open_file_and_lock(RUNTIME_DIR "/user/.pam-systemd-session")) >= 0) {
 202                 uint64_t counter;
 203                 ssize_t r;
 204
 205                 /* We do a bit of endianess swapping here, just to be
 206                  * sure. /var should be machine specific anyway, and
 207                  * /var/run even mounted from tmpfs, so this
 208                  * byteswapping should really not be necessary. But
 209                  * then again, you never know, so let's avoid any
 210                  * risk. */
 211
 212                 if (loop_read(fd, &counter, sizeof(counter), false) != sizeof(counter))
 213                         counter = 1;
 214                 else
 215                         counter = le64toh(counter) + 1;
 216
 217                 if (lseek(fd, 0, SEEK_SET) == 0) {
 218                         uint64_t swapped = htole64(counter);
 219
 220                         r = loop_write(fd, &swapped, sizeof(swapped), false);
 221
 222                         if (r != sizeof(swapped))
 223                                 r = -EIO;
 224                 } else
 225                         r = -errno;
 226
 227                 close_nointr_nofail(fd);
 228
 229                 if (r >= 0) {
 230                         *mode = SESSION_ID_COUNTER;
 231                         return counter;
 232                 }
 233         }
 234
 235         *mode = SESSION_ID_RANDOM;
 236
 237         /* Last attempt, pick a random value */
 238         return (uint64_t) random_ull();
 239 }
 240 static int get_user_data(
 241                 pam_handle_t *handle,
 242                 const char **ret_username,
 243                 struct passwd **ret_pw) {
 244
 245         const char *username = NULL;
 246         struct passwd *pw = NULL;
 247         int r;
 248         bool have_loginuid = false;
 249         char *s;
 250
 251         assert(handle);
 252         assert(ret_username);
 253         assert(ret_pw);
 254
 255         if (read_one_line_file("/proc/self/loginuid", &s) >= 0) {
 256                 uint32_t u;
 257
 258                 r = safe_atou32(s, &u);
 259                 free(s);
 260
 261                 if (r >= 0 && u != (uint32_t) -1 && u > 0) {
 262                         have_loginuid = true;
 263                         pw = pam_modutil_getpwuid(handle, u);
 264                 }
 265         }
 266
 267         if (!have_loginuid) {
 268                 if ((r = pam_get_user(handle, &username, NULL)) != PAM_SUCCESS) {
 269                         pam_syslog(handle, LOG_ERR, "Failed to get user name.");
 270                         return r;
 271                 }
 272
 273                 if (!username || !*username) {
 274                         pam_syslog(handle, LOG_ERR, "User name not valid.");
 275                         return PAM_AUTH_ERR;
 276                 }
 277
 278                 pw = pam_modutil_getpwnam(handle, username);
 279         }
 280
 281         if (!pw) {
 282                 pam_syslog(handle, LOG_ERR, "Failed to get user data.");
 283                 return PAM_USER_UNKNOWN;
 284         }
 285
 286         *ret_pw = pw;
 287         *ret_username = username ? username : pw->pw_name;
 288
 289         return PAM_SUCCESS;
 290 }
 291
 292 static int create_user_group(
 293                 pam_handle_t *handle,
 294                 const char *controller,
 295                 const char *group,
 296                 struct passwd *pw,
 297                 bool attach,
 298                 bool remember) {
 299
 300         int r;
 301
 302         assert(handle);
 303         assert(group);
 304
 305         if (attach)
 306                 r = cg_create_and_attach(controller, group, 0);
 307         else
 308                 r = cg_create(controller, group);
 309
 310         if (r < 0) {
 311                 pam_syslog(handle, LOG_ERR, "Failed to create cgroup: %s", strerror(-r));
 312                 return PAM_SESSION_ERR;
 313         }
 314
 315         if (r > 0 && remember) {
 316                 /* Remember that it was us who created this group, and
 317                  * that hence we need to remove it too. This is a
 318                  * protection against removing the cgroup when run
 319                  * recursively. */
 320                 if ((r = pam_set_data(handle, "systemd.created", INT_TO_PTR(1), NULL)) != PAM_SUCCESS) {
 321                         pam_syslog(handle, LOG_ERR, "Failed to install created variable.");
 322                         return r;
 323                 }
 324         }
 325
 326         if ((r = cg_set_task_access(controller, group, 0644, pw->pw_uid, pw->pw_gid)) < 0 ||
 327             (r = cg_set_group_access(controller, group, 0755, pw->pw_uid, pw->pw_gid)) < 0) {
 328                 pam_syslog(handle, LOG_ERR, "Failed to change access modes: %s", strerror(-r));
 329                 return PAM_SESSION_ERR;
 330         }
 331
 332         return PAM_SUCCESS;
 333 }
 334
 335 static int reset_group(
 336                 pam_handle_t *handle,
 337                 const char *controller) {
 338
 339         int r;
 340
 341         assert(handle);
 342
 343         if ((r = cg_attach(controller, "/", 0)) < 0) {
 344                 pam_syslog(handle, LOG_ERR, "Failed to reset cgroup for controller %s: %s", controller, strerror(-r));
 345                 return PAM_SESSION_ERR;
 346         }
 347
 348         return PAM_SUCCESS;
 349 }
 350
 351 _public_ PAM_EXTERN int pam_sm_open_session(
 352                 pam_handle_t *handle,
 353                 int flags,
 354                 int argc, const char **argv) {
 355
 356         const char *username = NULL;
 357         struct passwd *pw;
 358         int r;
 359         char *buf = NULL;
 360         int lock_fd = -1;
 361         bool create_session = true;
 362         char **controllers = NULL, **reset_controllers = NULL, **c;
 363
 364         assert(handle);
 365
 366         /* pam_syslog(handle, LOG_DEBUG, "pam-systemd initializing"); */
 367
 368         /* Make this a NOP on non-systemd systems */
 369         if (sd_booted() <= 0)
 370                 return PAM_SUCCESS;
 371
 372         if (parse_argv(handle, argc, argv, &create_session, NULL, NULL, NULL, &controllers, &reset_controllers) < 0)
 373                 return PAM_SESSION_ERR;
 374
 375         if ((r = get_user_data(handle, &username, &pw)) != PAM_SUCCESS)
 376                 goto finish;
 377
 378         if (safe_mkdir(RUNTIME_DIR "/user", 0755, 0, 0) < 0) {
 379                 pam_syslog(handle, LOG_ERR, "Failed to create runtime directory: %m");
 380                 r = PAM_SYSTEM_ERR;
 381                 goto finish;
 382         }
 383
 384         if ((lock_fd = open_file_and_lock(RUNTIME_DIR "/user/.pam-systemd-lock")) < 0) {
 385                 pam_syslog(handle, LOG_ERR, "Failed to lock runtime directory: %m");
 386                 r = PAM_SYSTEM_ERR;
 387                 goto finish;
 388         }
 389
 390         /* Create /var/run/$USER */
 391         free(buf);
 392         if (asprintf(&buf, RUNTIME_DIR "/user/%s", username) < 0) {
 393                 r = PAM_BUF_ERR;
 394                 goto finish;
 395         }
 396
 397         if (safe_mkdir(buf, 0700, pw->pw_uid, pw->pw_gid) < 0) {
 398                 pam_syslog(handle, LOG_WARNING, "Failed to create runtime directory: %m");
 399                 r = PAM_SYSTEM_ERR;
 400                 goto finish;
 401         } else if ((r = pam_misc_setenv(handle, "XDG_RUNTIME_DIR", buf, 0)) != PAM_SUCCESS) {
 402                 pam_syslog(handle, LOG_ERR, "Failed to set runtime dir.");
 403                 goto finish;
 404         }
 405
 406         free(buf);
 407         buf = NULL;
 408
 409         if (create_session) {
 410                 const char *id;
 411
 412                 /* Reuse or create XDG session ID */
 413                 if (!(id = pam_getenv(handle, "XDG_SESSION_ID"))) {
 414                         int mode;
 415
 416                         if (asprintf(&buf, "%llux", (unsigned long long) get_session_id(&mode)) < 0) {
 417                                 r = PAM_BUF_ERR;
 418                                 goto finish;
 419                         }
 420
 421                         /* To avoid id clashes we add the session id
 422                          * source to our session ids. Note that the
 423                          * session id source might change during
 424                          * runtime, because a filesystem became
 425                          * writable or the system reconfigured. */
 426                         buf[strlen(buf)-1] =
 427                                 mode != SESSION_ID_AUDIT ? (char) mode : 0;
 428
 429                         if ((r = pam_misc_setenv(handle, "XDG_SESSION_ID", buf, 0)) != PAM_SUCCESS) {
 430                                 pam_syslog(handle, LOG_ERR, "Failed to set session id.");
 431                                 goto finish;
 432                         }
 433
 434                         if (!(id = pam_getenv(handle, "XDG_SESSION_ID"))) {
 435                                 pam_syslog(handle, LOG_ERR, "Failed to get session id.");
 436                                 r = PAM_SESSION_ERR;
 437                                 goto finish;
 438                         }
 439                 }
 440
 441                 r = asprintf(&buf, "/user/%s/%s", username, id);
 442         } else
 443                 r = asprintf(&buf, "/user/%s/master", username);
 444
 445         if (r < 0) {
 446                 r = PAM_BUF_ERR;
 447                 goto finish;
 448         }
 449
 450         pam_syslog(handle, LOG_INFO, "Moving new user session for %s into control group %s.", username, buf);
 451
 452         if ((r = create_user_group(handle, SYSTEMD_CGROUP_CONTROLLER, buf, pw, true, true)) != PAM_SUCCESS)
 453                 goto finish;
 454
 455         /* The additional controllers don't really matter, so we
 456          * ignore the return value */
 457         STRV_FOREACH(c, controllers)
 458                 create_user_group(handle, *c, buf, pw, true, false);
 459
 460         STRV_FOREACH(c, reset_controllers)
 461                 reset_group(handle, *c);
 462
 463         r = PAM_SUCCESS;
 464
 465 finish:
 466         free(buf);
 467
 468         if (lock_fd >= 0)
 469                 close_nointr_nofail(lock_fd);
 470
 471         strv_free(controllers);
 472         strv_free(reset_controllers);
 473
 474         return r;
 475 }
 476
 477 static int session_remains(pam_handle_t *handle, const char *user_path) {
 478         int r;
 479         bool remains = false;
 480         DIR *d;
 481         char *subgroup;
 482
 483         if ((r = cg_enumerate_subgroups(SYSTEMD_CGROUP_CONTROLLER, user_path, &d)) < 0)
 484                 return r;
 485
 486         while ((r = cg_read_subgroup(d, &subgroup)) > 0) {
 487
 488                 remains = !streq(subgroup, "master");
 489                 free(subgroup);
 490
 491                 if (remains)
 492                         break;
 493         }
 494
 495         closedir(d);
 496
 497         if (r < 0)
 498                 return r;
 499
 500         return !!remains;
 501 }
 502
 503 _public_ PAM_EXTERN int pam_sm_close_session(
 504                 pam_handle_t *handle,
 505                 int flags,
 506                 int argc, const char **argv) {
 507
 508         const char *username = NULL;
 509         bool kill_session = false;
 510         bool kill_user = false;
 511         bool keep_root = true;
 512         int lock_fd = -1, r;
 513         char *session_path = NULL, *nosession_path = NULL, *user_path = NULL;
 514         const char *id;
 515         struct passwd *pw;
 516         const void *created = NULL;
 517         char **controllers = NULL, **c;
 518
 519         assert(handle);
 520
 521         /* Make this a NOP on non-systemd systems */
 522         if (sd_booted() <= 0)
 523                 return PAM_SUCCESS;
 524
 525         if (parse_argv(handle, argc, argv, NULL, &kill_session, &kill_user, &keep_root, &controllers, NULL) < 0)
 526                 return PAM_SESSION_ERR;
 527
 528         if ((r = get_user_data(handle, &username, &pw)) != PAM_SUCCESS)
 529                 goto finish;
 530
 531         if ((lock_fd = open_file_and_lock(RUNTIME_DIR "/user/.pam-systemd-lock")) < 0) {
 532                 pam_syslog(handle, LOG_ERR, "Failed to lock runtime directory: %m");
 533                 r = PAM_SYSTEM_ERR;
 534                 goto finish;
 535         }
 536
 537         /* We are probably still in some session/user dir. Move ourselves out of the way as first step */
 538         if ((r = cg_attach(SYSTEMD_CGROUP_CONTROLLER, "/user", 0)) < 0)
 539                 pam_syslog(handle, LOG_ERR, "Failed to move us away: %s", strerror(-r));
 540
 541         STRV_FOREACH(c, controllers)
 542                 if ((r = cg_attach(*c, "/user", 0)) < 0)
 543                         pam_syslog(handle, LOG_ERR, "Failed to move us away in %s hierarchy: %s", *c, strerror(-r));
 544
 545         if (asprintf(&user_path, "/user/%s", username) < 0) {
 546                 r = PAM_BUF_ERR;
 547                 goto finish;
 548         }
 549
 550         pam_get_data(handle, "systemd.created", &created);
 551
 552         if ((id = pam_getenv(handle, "XDG_SESSION_ID")) && created) {
 553
 554                 if (asprintf(&session_path, "/user/%s/%s", username, id) < 0 ||
 555                     asprintf(&nosession_path, "/user/%s/master", username) < 0) {
 556                         r = PAM_BUF_ERR;
 557                         goto finish;
 558                 }
 559
 560                 if (kill_session && (pw->pw_uid != 0 || !keep_root))  {
 561                         pam_syslog(handle, LOG_INFO, "Killing remaining processes of user session %s of %s.", id, username);
 562
 563                         /* Kill processes in session cgroup, and delete it */
 564                         if ((r = cg_kill_recursive_and_wait(SYSTEMD_CGROUP_CONTROLLER, session_path, true)) < 0)
 565                                 pam_syslog(handle, LOG_ERR, "Failed to kill session cgroup: %s", strerror(-r));
 566                 } else {
 567                         pam_syslog(handle, LOG_INFO, "Moving remaining processes of user session %s of %s into control group %s.", id, username, nosession_path);
 568
 569                         /* Migrate processes from session to user
 570                          * cgroup. First, try to create the user group
 571                          * in case it doesn't exist yet. Also, delete
 572                          * the session group. */
 573                         create_user_group(handle, SYSTEMD_CGROUP_CONTROLLER, nosession_path, pw, false, false);
 574
 575                         if ((r = cg_migrate_recursive(SYSTEMD_CGROUP_CONTROLLER, session_path, nosession_path, false, true)) < 0)
 576                                 pam_syslog(handle, LOG_ERR, "Failed to migrate session cgroup: %s", strerror(-r));
 577                 }
 578
 579                 STRV_FOREACH(c, controllers) {
 580                         create_user_group(handle, *c, nosession_path, pw, false, false);
 581
 582                         if ((r = cg_migrate_recursive(*c, session_path, nosession_path, false, true)) < 0)
 583                                 pam_syslog(handle, LOG_ERR, "Failed to migrate session cgroup in hierarchy %s: %s", *c, strerror(-r));
 584                 }
 585         }
 586
 587         /* GC user tree */
 588         cg_trim(SYSTEMD_CGROUP_CONTROLLER, user_path, false);
 589
 590         if ((r = session_remains(handle, user_path)) < 0)
 591                 pam_syslog(handle, LOG_ERR, "Failed to determine whether a session remains: %s", strerror(-r));
 592
 593         /* Kill user processes not attached to any session */
 594         if (kill_user && r == 0 && (pw->pw_uid != 0 || !keep_root)) {
 595
 596                 /* Kill user cgroup */
 597                 if ((r = cg_kill_recursive_and_wait(SYSTEMD_CGROUP_CONTROLLER, user_path, true)) < 0)
 598                         pam_syslog(handle, LOG_ERR, "Failed to kill user cgroup: %s", strerror(-r));
 599         } else {
 600
 601                 if ((r = cg_is_empty_recursive(SYSTEMD_CGROUP_CONTROLLER, user_path, true)) < 0)
 602                         pam_syslog(handle, LOG_ERR, "Failed to check user cgroup: %s", strerror(-r));
 603
 604                 /* Remove user cgroup */
 605                 if (r > 0) {
 606                         if ((r = cg_delete(SYSTEMD_CGROUP_CONTROLLER, user_path)) < 0)
 607                                 pam_syslog(handle, LOG_ERR, "Failed to delete user cgroup: %s", strerror(-r));
 608
 609                 /* If we managed to find somebody, don't cleanup the cgroup. */
 610                 } else if (r == 0)
 611                         r = -EBUSY;
 612         }
 613
 614         STRV_FOREACH(c, controllers)
 615                 cg_trim(*c, user_path, true);
 616
 617         if (r >= 0) {
 618                 const char *runtime_dir;
 619
 620                 if ((runtime_dir = pam_getenv(handle, "XDG_RUNTIME_DIR")))
 621                         if ((r = rm_rf(runtime_dir, false, true)) < 0)
 622                                 pam_syslog(handle, LOG_ERR, "Failed to remove runtime directory: %s", strerror(-r));
 623         }
 624
 625         /* pam_syslog(handle, LOG_DEBUG, "pam-systemd done"); */
 626
 627         r = PAM_SUCCESS;
 628
 629 finish:
 630         if (lock_fd >= 0)
 631                 close_nointr_nofail(lock_fd);
 632
 633         free(session_path);
 634         free(nosession_path);
 635         free(user_path);
 636
 637         strv_free(controllers);
 638
 639         return r;
 640 }