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