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