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