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