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
  39 static int parse_argv(pam_handle_t *handle,
  40                       int argc, const char **argv,
  41                       bool *create_session,
  42                       bool *kill_session,
  43                       bool *kill_user) {
  44
  45         unsigned i;
  46
  47         assert(argc >= 0);
  48         assert(argc == 0 || argv);
  49
  50         for (i = 0; i < (unsigned) argc; i++) {
  51                 int k;
  52
  53                 if (startswith(argv[i], "create-session=")) {
  54                         if ((k = parse_boolean(argv[i] + 15)) < 0) {
  55                                 pam_syslog(handle, LOG_ERR, "Failed to parse create-session= argument.");
  56                                 return k;
  57                         }
  58
  59                         if (create_session)
  60                                 *create_session = k;
  61                 } else if (startswith(argv[i], "kill-session=")) {
  62                         if ((k = parse_boolean(argv[i] + 13)) < 0) {
  63                                 pam_syslog(handle, LOG_ERR, "Failed to parse kill-session= argument.");
  64                                 return k;
  65                         }
  66
  67                         if (kill_session)
  68                                 *kill_session = k;
  69
  70                 } else if (startswith(argv[i], "kill-user=")) {
  71                         if ((k = parse_boolean(argv[i] + 10)) < 0) {
  72                                 pam_syslog(handle, LOG_ERR, "Failed to parse kill-user= argument.");
  73                                 return k;
  74                         }
  75
  76                         if (kill_user)
  77                                 *kill_user = k;
  78                 } else {
  79                         pam_syslog(handle, LOG_ERR, "Unknown parameter '%s'.", argv[i]);
  80                         return -EINVAL;
  81                 }
  82         }
  83
  84         if (kill_session && *kill_session && kill_user)
  85                 *kill_user = true;
  86
  87         return 0;
  88 }
  89
  90 static int open_file_and_lock(const char *fn) {
  91         int fd;
  92
  93         assert(fn);
  94
  95         if ((fd = open(fn, O_RDWR|O_CLOEXEC|O_NOCTTY|O_NOFOLLOW|O_CREAT, 0600)) < 0)
  96                 return -errno;
  97
  98         /* The BSD socket semantics are a lot nicer than those of
  99          * POSIX locks. Which is why we use flock() here. BSD locking
 100          * does not work across NFS which however is not needed here
 101          * as the filesystems in question should be local, and only
 102          * locally accessible, and most likely even tmpfs. */
 103
 104         if (flock(fd, LOCK_EX) < 0)
 105                 return -errno;
 106
 107         return fd;
 108 }
 109
 110 enum {
 111         SESSION_ID_AUDIT = 'a',
 112         SESSION_ID_COUNTER = 'c',
 113         SESSION_ID_RANDOM = 'r'
 114 };
 115
 116 static uint64_t get_session_id(int *mode) {
 117         char *s;
 118         int fd;
 119
 120         assert(mode);
 121
 122         /* First attempt: let's use the session ID of the audit
 123          * system, if it is available. */
 124         if (read_one_line_file("/proc/self/sessionid", &s) >= 0) {
 125                 uint32_t u;
 126                 int r;
 127
 128                 r = safe_atou32(s, &u);
 129                 free(s);
 130
 131                 if (r >= 0 && u != (uint32_t) -1 && u > 0) {
 132                         *mode = SESSION_ID_AUDIT;
 133                         return (uint64_t) u;
 134                 }
 135         }
 136
 137         /* Second attempt, use our own counter. */
 138         if ((fd = open_file_and_lock(RUNTIME_DIR "/user/.pam-systemd-session")) >= 0) {
 139                 uint64_t counter;
 140                 ssize_t r;
 141
 142                 /* We do a bit of endianess swapping here, just to be
 143                  * sure. /var should be machine specific anyway, and
 144                  * /var/run even mounted from tmpfs, so this
 145                  * byteswapping should really not be necessary. But
 146                  * then again, you never know, so let's avoid any
 147                  * risk. */
 148
 149                 if (loop_read(fd, &counter, sizeof(counter), false) != sizeof(counter))
 150                         counter = 1;
 151                 else
 152                         counter = le64toh(counter) + 1;
 153
 154                 if (lseek(fd, 0, SEEK_SET) == 0) {
 155                         uint64_t swapped = htole64(counter);
 156
 157                         r = loop_write(fd, &swapped, sizeof(swapped), false);
 158
 159                         if (r != sizeof(swapped))
 160                                 r = -EIO;
 161                 } else
 162                         r = -errno;
 163
 164                 close_nointr_nofail(fd);
 165
 166                 if (r >= 0) {
 167                         *mode = SESSION_ID_COUNTER;
 168                         return counter;
 169                 }
 170         }
 171
 172         *mode = SESSION_ID_RANDOM;
 173
 174         /* Last attempt, pick a random value */
 175         return (uint64_t) random_ull();
 176 }
 177 static int get_user_data(
 178                 pam_handle_t *handle,
 179                 const char **ret_username,
 180                 struct passwd **ret_pw) {
 181
 182         const char *username = NULL;
 183         struct passwd *pw = NULL;
 184         int r;
 185         bool have_loginuid = false;
 186         char *s;
 187
 188         assert(handle);
 189         assert(ret_username);
 190         assert(ret_pw);
 191
 192         if (read_one_line_file("/proc/self/loginuid", &s) >= 0) {
 193                 uint32_t u;
 194
 195                 r = safe_atou32(s, &u);
 196                 free(s);
 197
 198                 if (r >= 0 && u != (uint32_t) -1 && u > 0) {
 199                         have_loginuid = true;
 200                         pw = pam_modutil_getpwuid(handle, u);
 201                 }
 202         }
 203
 204         if (!have_loginuid) {
 205                 if ((r = pam_get_user(handle, &username, NULL)) != PAM_SUCCESS) {
 206                         pam_syslog(handle, LOG_ERR, "Failed to get user name.");
 207                         return r;
 208                 }
 209
 210                 if (!username || !*username) {
 211                         pam_syslog(handle, LOG_ERR, "User name not valid.");
 212                         return PAM_AUTH_ERR;
 213                 }
 214
 215                 pw = pam_modutil_getpwnam(handle, username);
 216         }
 217
 218         if (!pw) {
 219                 pam_syslog(handle, LOG_ERR, "Failed to get user data.");
 220                 return PAM_USER_UNKNOWN;
 221         }
 222
 223         *ret_pw = pw;
 224         *ret_username = username ? username : pw->pw_name;
 225
 226         return PAM_SUCCESS;
 227 }
 228
 229 static int create_user_group(pam_handle_t *handle, const char *group, struct passwd *pw, bool attach, bool remember) {
 230         int r;
 231
 232         assert(handle);
 233         assert(group);
 234
 235         if (attach)
 236                 r = cg_create_and_attach(SYSTEMD_CGROUP_CONTROLLER, group, 0);
 237         else
 238                 r = cg_create(SYSTEMD_CGROUP_CONTROLLER, group);
 239
 240         if (r < 0) {
 241                 pam_syslog(handle, LOG_ERR, "Failed to create cgroup: %s", strerror(-r));
 242                 return PAM_SESSION_ERR;
 243         }
 244
 245         if (r > 0 && remember) {
 246                 /* Remember that it was us who created this group, and
 247                  * that hence we need to remove it too. This is a
 248                  * protection against removing the cgroup when run
 249                  * recursively. */
 250                 if ((r = pam_set_data(handle, "systemd.created", INT_TO_PTR(1), NULL)) != PAM_SUCCESS) {
 251                         pam_syslog(handle, LOG_ERR, "Failed to install created variable.");
 252                         return r;
 253                 }
 254         }
 255
 256         if ((r = cg_set_task_access(SYSTEMD_CGROUP_CONTROLLER, group, 0755, pw->pw_uid, pw->pw_gid)) < 0 ||
 257             (r = cg_set_group_access(SYSTEMD_CGROUP_CONTROLLER, group, 0755, pw->pw_uid, pw->pw_gid)) < 0) {
 258                 pam_syslog(handle, LOG_ERR, "Failed to change access modes: %s", strerror(-r));
 259                 return PAM_SESSION_ERR;
 260         }
 261
 262         return PAM_SUCCESS;
 263 }
 264
 265 _public_ PAM_EXTERN int pam_sm_open_session(
 266                 pam_handle_t *handle,
 267                 int flags,
 268                 int argc, const char **argv) {
 269
 270         const char *username = NULL;
 271         struct passwd *pw;
 272         int r;
 273         char *buf = NULL;
 274         int lock_fd = -1;
 275         bool create_session = true;
 276
 277         assert(handle);
 278
 279         /* pam_syslog(handle, LOG_DEBUG, "pam-systemd initializing"); */
 280
 281         if (parse_argv(handle, argc, argv, &create_session, NULL, NULL) < 0)
 282                 return PAM_SESSION_ERR;
 283
 284         /* Make this a NOP on non-systemd systems */
 285         if (sd_booted() <= 0)
 286                 return PAM_SUCCESS;
 287
 288         if ((r = get_user_data(handle, &username, &pw)) != PAM_SUCCESS)
 289                 goto finish;
 290
 291         if (safe_mkdir(RUNTIME_DIR "/user", 0755, 0, 0) < 0) {
 292                 pam_syslog(handle, LOG_ERR, "Failed to create runtime directory: %m");
 293                 r = PAM_SYSTEM_ERR;
 294                 goto finish;
 295         }
 296
 297         if ((lock_fd = open_file_and_lock(RUNTIME_DIR "/user/.pam-systemd-lock")) < 0) {
 298                 pam_syslog(handle, LOG_ERR, "Failed to lock runtime directory: %m");
 299                 r = PAM_SYSTEM_ERR;
 300                 goto finish;
 301         }
 302
 303         /* Create /var/run/$USER */
 304         free(buf);
 305         if (asprintf(&buf, RUNTIME_DIR "/user/%s", username) < 0) {
 306                 r = PAM_BUF_ERR;
 307                 goto finish;
 308         }
 309
 310         if (safe_mkdir(buf, 0700, pw->pw_uid, pw->pw_gid) < 0) {
 311                 pam_syslog(handle, LOG_WARNING, "Failed to create runtime directory: %m");
 312                 r = PAM_SYSTEM_ERR;
 313                 goto finish;
 314         } else if ((r = pam_misc_setenv(handle, "XDG_RUNTIME_DIR", buf, 0)) != PAM_SUCCESS) {
 315                 pam_syslog(handle, LOG_ERR, "Failed to set runtime dir.");
 316                 goto finish;
 317         }
 318
 319         free(buf);
 320         buf = NULL;
 321
 322         if (create_session) {
 323                 const char *id;
 324
 325                 /* Reuse or create XDG session ID */
 326                 if (!(id = pam_getenv(handle, "XDG_SESSION_ID"))) {
 327                         int mode;
 328
 329                         if (asprintf(&buf, "%llux", (unsigned long long) get_session_id(&mode)) < 0) {
 330                                 r = PAM_BUF_ERR;
 331                                 goto finish;
 332                         }
 333
 334                         /* To avoid id clashes we add the session id
 335                          * source to our session ids. Note that the
 336                          * session id source might change during
 337                          * runtime, because a filesystem became
 338                          * writable or the system reconfigured. */
 339                         buf[strlen(buf)-1] =
 340                                 mode != SESSION_ID_AUDIT ? (char) mode : 0;
 341
 342                         if ((r = pam_misc_setenv(handle, "XDG_SESSION_ID", buf, 0)) != PAM_SUCCESS) {
 343                                 pam_syslog(handle, LOG_ERR, "Failed to set session id.");
 344                                 goto finish;
 345                         }
 346
 347                         if (!(id = pam_getenv(handle, "XDG_SESSION_ID"))) {
 348                                 pam_syslog(handle, LOG_ERR, "Failed to get session id.");
 349                                 r = PAM_SESSION_ERR;
 350                                 goto finish;
 351                         }
 352                 }
 353
 354                 r = asprintf(&buf, "/user/%s/%s", username, id);
 355         } else
 356                 r = asprintf(&buf, "/user/%s/master", username);
 357
 358         if (r < 0) {
 359                 r = PAM_BUF_ERR;
 360                 goto finish;
 361         }
 362
 363         pam_syslog(handle, LOG_INFO, "Moving new user session for %s into control group %s.", username, buf);
 364
 365         if ((r = create_user_group(handle, buf, pw, true, true)) != PAM_SUCCESS)
 366                 goto finish;
 367
 368         r = PAM_SUCCESS;
 369
 370 finish:
 371         free(buf);
 372
 373         if (lock_fd >= 0)
 374                 close_nointr_nofail(lock_fd);
 375
 376         return r;
 377 }
 378
 379 static int session_remains(pam_handle_t *handle, const char *user_path) {
 380         int r;
 381         bool remains = false;
 382         DIR *d;
 383         char *subgroup;
 384
 385         if ((r = cg_enumerate_subgroups(SYSTEMD_CGROUP_CONTROLLER, user_path, &d)) < 0)
 386                 return r;
 387
 388         while ((r = cg_read_subgroup(d, &subgroup)) > 0) {
 389
 390                 remains = !streq(subgroup, "master");
 391                 free(subgroup);
 392
 393                 if (remains)
 394                         break;
 395         }
 396
 397         closedir(d);
 398
 399         if (r < 0)
 400                 return r;
 401
 402         return !!remains;
 403 }
 404
 405 _public_ PAM_EXTERN int pam_sm_close_session(
 406                 pam_handle_t *handle,
 407                 int flags,
 408                 int argc, const char **argv) {
 409
 410         const char *username = NULL;
 411         bool kill_session = false;
 412         bool kill_user = false;
 413         int lock_fd = -1, r;
 414         char *session_path = NULL, *nosession_path = NULL, *user_path = NULL;
 415         const char *id;
 416         struct passwd *pw;
 417         const void *created = NULL;
 418
 419         assert(handle);
 420
 421         if (parse_argv(handle, argc, argv, NULL, &kill_session, &kill_user) < 0)
 422                 return PAM_SESSION_ERR;
 423
 424         /* Make this a NOP on non-systemd systems */
 425         if (sd_booted() <= 0)
 426                 return PAM_SUCCESS;
 427
 428         if ((r = get_user_data(handle, &username, &pw)) != PAM_SUCCESS)
 429                 goto finish;
 430
 431         if ((lock_fd = open_file_and_lock(RUNTIME_DIR "/user/.pam-systemd-lock")) < 0) {
 432                 pam_syslog(handle, LOG_ERR, "Failed to lock runtime directory: %m");
 433                 r = PAM_SYSTEM_ERR;
 434                 goto finish;
 435         }
 436
 437         /* We are probably still in some session/user dir. Move ourselves out of the way as first step */
 438         if ((r = cg_attach(SYSTEMD_CGROUP_CONTROLLER, "/user", 0)) < 0)
 439                 pam_syslog(handle, LOG_ERR, "Failed to move us away: %s", strerror(-r));
 440
 441         if (asprintf(&user_path, "/user/%s", username) < 0) {
 442                 r = PAM_BUF_ERR;
 443                 goto finish;
 444         }
 445
 446         pam_get_data(handle, "systemd.created", &created);
 447
 448         if ((id = pam_getenv(handle, "XDG_SESSION_ID")) && created) {
 449
 450                 if (asprintf(&session_path, "/user/%s/%s", username, id) < 0 ||
 451                     asprintf(&nosession_path, "/user/%s/master", username) < 0) {
 452                         r = PAM_BUF_ERR;
 453                         goto finish;
 454                 }
 455
 456                 if (kill_session)  {
 457                         pam_syslog(handle, LOG_INFO, "Killing remaining processes of user session %s of %s.", id, username);
 458
 459                         /* Kill processes in session cgroup, and delete it */
 460                         if ((r = cg_kill_recursive_and_wait(SYSTEMD_CGROUP_CONTROLLER, session_path, true)) < 0)
 461                                 pam_syslog(handle, LOG_ERR, "Failed to kill session cgroup: %s", strerror(-r));
 462                 } else {
 463                         pam_syslog(handle, LOG_INFO, "Moving remaining processes of user session %s of %s into control group %s.", id, username, nosession_path);
 464
 465                         /* Migrate processes from session to user
 466                          * cgroup. First, try to create the user group
 467                          * in case it doesn't exist yet. Also, delete
 468                          * the session group. */
 469                         create_user_group(handle, nosession_path, pw, false, false);
 470
 471                         if ((r = cg_migrate_recursive(SYSTEMD_CGROUP_CONTROLLER, session_path, nosession_path, false, true)) < 0)
 472                                 pam_syslog(handle, LOG_ERR, "Failed to migrate session cgroup: %s", strerror(-r));
 473                 }
 474         }
 475
 476         /* GC user tree */
 477         cg_trim(SYSTEMD_CGROUP_CONTROLLER, user_path, false);
 478
 479         if ((r = session_remains(handle, user_path)) < 0)
 480                 pam_syslog(handle, LOG_ERR, "Failed to determine whether a session remains: %s", strerror(-r));
 481
 482         /* Kill user processes not attached to any session */
 483         if (kill_user && r == 0) {
 484
 485                 /* Kill user cgroup */
 486                 if ((r = cg_kill_recursive_and_wait(SYSTEMD_CGROUP_CONTROLLER, user_path, true)) < 0)
 487                         pam_syslog(handle, LOG_ERR, "Failed to kill user cgroup: %s", strerror(-r));
 488         } else {
 489
 490                 if ((r = cg_is_empty_recursive(SYSTEMD_CGROUP_CONTROLLER, user_path, true)) < 0)
 491                         pam_syslog(handle, LOG_ERR, "Failed to check user cgroup: %s", strerror(-r));
 492
 493                 /* Remove user cgroup */
 494                 if (r > 0) {
 495                         if ((r = cg_delete(SYSTEMD_CGROUP_CONTROLLER, user_path)) < 0)
 496                                 pam_syslog(handle, LOG_ERR, "Failed to delete user cgroup: %s", strerror(-r));
 497
 498                 /* If we managed to find somebody, don't cleanup the cgroup. */
 499                 } else if (r == 0)
 500                         r = -EBUSY;
 501         }
 502
 503         if (r >= 0) {
 504                 const char *runtime_dir;
 505
 506                 if ((runtime_dir = pam_getenv(handle, "XDG_RUNTIME_DIR")))
 507                         if ((r = rm_rf(runtime_dir, false, true)) < 0)
 508                                 pam_syslog(handle, LOG_ERR, "Failed to remove runtime directory: %s", strerror(-r));
 509         }
 510
 511         /* pam_syslog(handle, LOG_DEBUG, "pam-systemd done"); */
 512
 513         r = PAM_SUCCESS;
 514
 515 finish:
 516         if (lock_fd >= 0)
 517                 close_nointr_nofail(lock_fd);
 518
 519         free(session_path);
 520         free(nosession_path);
 521         free(user_path);
 522
 523         return r;
 524 }