src/client/sandbox-server/main.c

   1 /* $Id$
   2  * filesystem sandbox server stub for libcaptive
   3  * Copyright (C) 2003 Jan Kratochvil <project-captive@jankratochvil.net>
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License as published by
   7  * the Free Software Foundation; exactly version 2 of June 1991 is required
   8  *
   9  * This program is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12  * GNU General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU General Public License
  15  * along with this program; if not, write to the Free Software
  16  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  17  */
  18
  19
  20 #include "config.h"
  21
  22 #include <glib/gmessages.h>
  23 #include <stdlib.h>
  24 #include <glib/giochannel.h>
  25 #include <glib/gerror.h>
  26 #include <popt.h>
  27 #include <string.h>
  28 #include <stdio.h>
  29 #include <locale.h>
  30 #include "captive/options.h"
  31 #include <glib-object.h>
  32 #include "captive/macros.h"
  33 #include <sys/types.h>
  34 #include <sys/stat.h>
  35 #include <unistd.h>
  36 #include <dirent.h>
  37 #include <errno.h>
  38 #include "../../libcaptive/sandbox/split.h"     /* for captive_sandbox_fd_closeup(); FIXME */
  39 #include <grp.h>
  40 #include <pwd.h>
  41 #include <fcntl.h>
  42 #include <sys/file.h>
  43
  44
  45 /* CONFIG: */
  46
  47 #define CHROOT_PATH_HASHKEY_LENGTH (64)
  48
  49
  50 GQuark sandbox_server_main_error_quark(void)
  51 {
  52 GQuark r=0;
  53
  54         if (!r)
  55                 r=g_quark_from_static_string("sandbox-server");
  56
  57         return r;
  58 }
  59
  60
  61 static gchar *optarg_setuid=CAPTIVE_SANDBOX_SETUID;
  62 static gchar *optarg_setgid=CAPTIVE_SANDBOX_SETGID;
  63 static gchar *optarg_chroot=CAPTIVE_SANDBOX_CHROOT;
  64
  65 static const struct poptOption popt_table[]={
  66 #define SANDBOX_SERVER_POPT(longname,argInfoP,argP,descripP,argDescripP) \
  67                 { \
  68                         longName: (longname), \
  69                         shortName: 0, \
  70                         argInfo: (argInfoP), \
  71                         arg: (void *)argP, \
  72                         val: 0, \
  73                         descrip: (descripP), \
  74                         argDescrip: (argDescripP), \
  75                 }
  76
  77                 SANDBOX_SERVER_POPT("setuid"  ,POPT_ARG_STRING,&optarg_setuid,N_("Username or UID to become; \"-\" for disable"),N_("UID")),
  78                 SANDBOX_SERVER_POPT("setgid"  ,POPT_ARG_STRING,&optarg_setgid,N_("Groupname or GID to become; \"-\" for disable"),N_("GID")),
  79                 SANDBOX_SERVER_POPT("chroot"  ,POPT_ARG_STRING,&optarg_chroot,N_("Pathname to directory for chroot(2); \"-\" for disable"),N_("directory")),
  80
  81 #undef SANDBOX_SERVER_POPT
  82                 POPT_AUTOHELP
  83                 POPT_TABLEEND
  84                 };
  85
  86
  87 static gchar *fatal_argv0;
  88
  89 static void fatal(const char *fmt,...)
  90 {
  91 va_list ap;
  92
  93         fprintf(stderr,"%s: ",fatal_argv0);
  94         va_start(ap,fmt);
  95         vfprintf(stderr,fmt,ap);
  96         va_end(ap);
  97         fprintf(stderr,"!\nAborting!\n");
  98         exit(EXIT_FAILURE);
  99         /* NOTREACHED */
 100         for (;;);
 101 }
 102
 103 static void check_dir_safety(const gchar *dir)
 104 {
 105 gchar *local_dir;
 106 const gchar *cs;
 107 static gint depth=0;
 108
 109         if (++depth>=1000)
 110                 fatal("Loop count >=%d during check_dir_safety(\"%s\")",depth,dir);
 111
 112         if (*dir!='/')
 113                 fatal("chroot path \"%s\" not absolute",dir);
 114         dir=captive_printf_alloca("%s/",dir);
 115         local_dir=(gchar *)captive_strdup_alloca(dir);
 116         for (cs=dir;cs;cs=strchr(cs+1,'/')) {
 117 struct stat statbuf;
 118
 119                 g_assert(*cs=='/');
 120                 /* Include the trailing '/' to resolve the root directory as "/". */
 121                 memcpy(local_dir,dir,cs+1-dir);
 122                 local_dir[cs+1-dir]=0;
 123                 if (lstat(local_dir,&statbuf))
 124                         fatal("lstat(\"%s\") of chroot path component: %m",local_dir);
 125                 if (S_ISLNK(statbuf.st_mode)) {
 126 char linkbuf[PATH_MAX];
 127 int linkbuflen;
 128
 129                         if (0>(linkbuflen=readlink(local_dir,linkbuf,sizeof(linkbuf)-1)))
 130                                 fatal("readlink(\"%s\") of chroot path component: %m",local_dir);
 131                         linkbuf[linkbuflen]=0;
 132                         check_dir_safety(linkbuf);
 133                         if (stat(local_dir,&statbuf))   /* NOT lstat(2) */
 134                                 fatal("stat(\"%s\") of chroot path component: %m",local_dir);
 135                         }
 136                 if (!S_ISDIR(statbuf.st_mode))
 137                         fatal("lstat/stat(\"%s\") of chroot path component is !S_ISDIR",local_dir);
 138                 if (statbuf.st_uid!=0)
 139                         fatal("lstat/stat(\"%s\") of chroot path component has UID %d !=0",local_dir,(int)statbuf.st_uid);
 140                 if (statbuf.st_gid!=0)
 141                         fatal("lstat/stat(\"%s\") of chroot path component has GID %d !=0",local_dir,(int)statbuf.st_gid);
 142                 if ((statbuf.st_mode&(S_IFDIR|S_ISVTX|0111)) != (S_IFDIR|0111))
 143                         fatal("lstat/stat(\"%s\") of chroot path component has mode 0%o !=04[01]111",local_dir,(int)statbuf.st_mode);
 144                 }
 145
 146         depth--;
 147 }
 148
 149 static void chrooted_unlink_recursive(const gchar *pathname)
 150 {
 151 DIR *dir;
 152 struct dirent *dirent;
 153 static gint depth=0;
 154 struct stat statbuf;
 155
 156         if (++depth>=1000)
 157                 fatal("Loop count >=%d during chrooted_unlink_recursive(\"%s\")",depth,pathname);
 158
 159         /* Security: Do not allow anyone to escape the sandbox directory by symlinks. */
 160         if (lstat(pathname,&statbuf))
 161                 fatal("Cannot lstat(\"%s\") to delete leftover sandbox files: %m",pathname);
 162         if (!S_ISDIR(statbuf.st_mode)) {
 163                 if (unlink(pathname))
 164                         fatal("Cannot unlink(\"%s\") to delete leftover sandbox files: %m",pathname);
 165                 goto done;
 166                 }
 167         if (!(dir=opendir(pathname)))
 168                 fatal("Cannot opendir(\"%s\") to delete leftover sandbox files: %m",pathname);
 169         while (errno=0,(dirent=readdir(dir))) {
 170 gchar *dirent_path;
 171
 172                 if (!strcmp(dirent->d_name,".") || !strcmp(dirent->d_name,".."))
 173                         continue;
 174                 dirent_path=g_strdup_printf("%s/%s",pathname,dirent->d_name);
 175                 chrooted_unlink_recursive(dirent_path);
 176                 g_free(dirent_path);
 177                 }
 178         if (errno)
 179                 fatal("Cannot readdir(\"%s\") during delete of leftover sandbox files: %m",pathname);
 180         if (closedir(dir))
 181                 fatal("Cannot closedir(\"%s\") during delete of leftover sandbox files: %m",pathname);
 182         if (rmdir(pathname))
 183                 fatal("Cannot rmdir(\"%s\") during delete of leftover sandbox files: %m",pathname);
 184
 185 done:
 186         depth--;
 187 }
 188
 189 static void chrooted_cleanuplockeddirs(const gchar *pathname)
 190 {
 191 DIR *dir;
 192 struct dirent *dirent;
 193
 194         if (!(dir=opendir(pathname))) {
 195                 if (errno!=ENOTDIR)
 196                         fatal("Cannot opendir(\"%s\") to delete leftover sandbox files: %m",pathname);
 197                 /* errno==ENOTDIR, a regular file */
 198                 if (unlink(pathname))
 199                         fatal("Cannot unlink(\"%s\") to delete leftover sandbox files: %m",pathname);
 200                 return;
 201                 }
 202         while (errno=0,(dirent=readdir(dir))) {
 203 gchar *dirent_path;
 204 int direntfd;
 205
 206                 if (!strcmp(dirent->d_name,".") || !strcmp(dirent->d_name,".."))
 207                         continue;
 208                 dirent_path=g_strdup_printf("%s/%s",pathname,dirent->d_name);
 209                 if (-1==(direntfd=open(dirent_path,O_RDONLY))) {
 210                         if (errno==ENOENT)      /* It could disappear in the meantime. */
 211                                 goto next_dirent_free_dirent_path;
 212                         fatal("Cannot open(\"%s\") as the child directory during delete of leftover sandbox files: %m",dirent_path);
 213                         }
 214                 if (flock(direntfd,LOCK_EX|LOCK_NB)) {
 215                         if (errno==EWOULDBLOCK) /* Valid directory in use. */
 216                                 goto next_dirent_close_direntfd;
 217                         fatal("Cannot flock(\"%s\",LOCK_EX|LOCK_NB) child directory during delete of leftover sandbox files: %m",dirent_path);
 218                         }
 219                 chrooted_unlink_recursive(dirent_path);
 220 next_dirent_close_direntfd:
 221                 if (close(direntfd))
 222                         fatal("Cannot close(\"%s\") child directory during delete of leftover sandbox files: %m",dirent_path);
 223 next_dirent_free_dirent_path:
 224                 g_free(dirent_path);
 225                 }
 226         if (errno)
 227                 fatal("Cannot readdir(\"%s\") during delete of leftover sandbox files: %m",pathname);
 228         if (closedir(dir))
 229                 fatal("Cannot closedir(\"%s\") during delete of leftover sandbox files: %m",pathname);
 230 }
 231
 232 static void chrooted_createdir(const gchar *dir,uid_t uid,gid_t gid,gboolean lock)
 233 {
 234 gint retries;
 235
 236         for (retries=0;retries<10;retries++) {
 237 struct stat statbuf;
 238 int dirfd;
 239
 240                 if (mkdir(dir,0711)) {
 241                         if (errno!=EEXIST)
 242                                 fatal("Failed to create chroot directory \"%s\": %m",dir);
 243                         chrooted_unlink_recursive(dir);
 244                         if (mkdir(dir,0711))
 245                                 fatal("Failed to create chroot directory \"%s\" after attempted unlink: %m",dir);
 246                         }
 247                 if (!lock)
 248                         break;
 249                 dirfd=open(dir,O_RDONLY);
 250                 if (dirfd==-1) {
 251                         if (errno!=ENOENT)
 252                                 fatal("Failed to open created chroot directory \"%s\" to lock it: %m",dir);
 253                         continue;
 254                         }
 255                 /* Do not use 'LOCK_NB' here as the garbage collector should release it soon. */
 256                 if (flock(dirfd,LOCK_EX))
 257                         fatal("Failed to lock created chroot directory \"%s\": %m",dir);
 258                 if (lstat(dir,&statbuf)) {
 259                         if (errno!=ENOENT)
 260                                 fatal("Failed to lstat(2) created chroot directory \"%s\": %m",dir);
 261                         if (close(dirfd))
 262                                 fatal("Failed to close created and locked chroot directory \"%s\": %m",dir);
 263                         continue;
 264                         }
 265                 /* Leave 'dirfd' open to leave it LOCK_EX-ed. */
 266                 break;
 267                 }
 268         if (chown(dir,uid,gid))
 269                 fatal("Failed to chown(\"%s\",%d,%d): %m",dir,uid,gid);
 270         if (chmod(dir,0711))    /* Just to be safe after chown(2); should be already done by mkdir(2). */
 271                 fatal("Failed to chmod(\"%s\",0%o): %m",dir,0711);
 272 }
 273
 274 static const gchar *chrooted_orbit_dir;
 275
 276 static void chroot_setup(gboolean fragile)
 277 {
 278 uid_t want_uid=0;
 279 const gchar *want_uid_name=NULL;
 280 gid_t want_gid=0;
 281 char *endptr;
 282
 283         if (fragile) {
 284                 captive_sandbox_fd_closeup(2 /* STDERR */ +1);
 285                 clearenv();
 286                 }
 287
 288 #define CLEANEMPTY(var) G_STMT_START { \
 289                 if ((var) && (!*(var) || *(var)=='-')) \
 290                         (var)=NULL; \
 291                 } G_STMT_END
 292         CLEANEMPTY(optarg_setgid);
 293         CLEANEMPTY(optarg_setuid);
 294         CLEANEMPTY(optarg_chroot);
 295 #undef CLEANEMPTY
 296
 297         if (optarg_setgid) {
 298 long want_gidl;
 299
 300                 want_gidl=strtol(optarg_setgid,&endptr,10);
 301                 if (!endptr || !*endptr) {
 302                         want_gid=want_gidl;
 303                         if (want_gidl<=0 || want_gid!=(gid_t)want_gidl)
 304                                 fatal("Numeric setgid not parsable: %s",optarg_setgid);
 305                         }
 306                 else {
 307 struct group *want_gid_group=NULL;
 308                         if (!(want_gid_group=getgrnam(optarg_setgid)))
 309                                 fatal("Unable to query setgid group name \"%s\"",optarg_setgid);
 310                         want_gid=want_gid_group->gr_gid;
 311                         }
 312                 }
 313
 314         if (optarg_setuid) {
 315 long want_uidl;
 316 struct passwd *want_uid_passwd;
 317                 want_uidl=strtol(optarg_setuid,&endptr,10);
 318                 if (!endptr || !*endptr) {
 319                         want_uid=want_uidl;
 320                         if (want_uidl<=0 || want_uid!=(gid_t)want_uidl)
 321                                 fatal("Numeric setuid not parsable: %s",optarg_setuid);
 322                         }
 323                 else {
 324                         if (!(want_uid_passwd=getpwnam(optarg_setuid)))
 325                                 fatal("Unable to query setuid user name \"%s\"",optarg_setuid);
 326                         want_uid=want_uid_passwd->pw_uid;
 327                         }
 328                 if (!want_uid)
 329                         fatal("Unable to detect setuid UID");
 330                 if (!(want_uid_passwd=getpwuid(want_uid)))
 331                         fatal("Unable to query name of UID %d",(int)want_uid);
 332                 want_uid_name=captive_strdup_alloca(want_uid_passwd->pw_name);
 333                 }
 334
 335         if (fragile && !optarg_chroot)
 336                 fatal("Fragile setuid/root environment but no --chroot set");
 337         if (optarg_chroot) {
 338 const gchar *chroot_pid_dir,*chroot_pid_hashkey_dir;
 339 GRand *grand;
 340 gchar chroot_hashkey[CHROOT_PATH_HASHKEY_LENGTH+1],*s;
 341 gint gi;
 342
 343                 check_dir_safety(optarg_chroot);
 344                 if (!(grand=g_rand_new()))      /* I hope g_rand_new() is security-safe. It looks so. */
 345                         fatal("Cannot initialize random number generator g_rand_new()");
 346                 for (s=chroot_hashkey;s<chroot_hashkey+CHROOT_PATH_HASHKEY_LENGTH;s++) {
 347                         gi=g_rand_int_range(grand,0,10+26+26);
 348                         /**/ if (gi>=0 && gi<10)
 349                                 *s='0'+gi-(0);
 350                         else if (gi>=10+0 && gi<10+26)
 351                                 *s='a'+gi-(10);
 352                         else if (gi>=10+26+0 && gi<10+26+26)
 353                                 *s='A'+gi-(10+26);
 354                         else g_assert_not_reached();
 355                         }
 356                 g_rand_free(grand);
 357                 *s=0;
 358                 if (geteuid()==0)       /* Not 'fragile' as we can be native 'root'. */
 359                         chrooted_cleanuplockeddirs(optarg_chroot);
 360                 chroot_pid_dir=captive_printf_alloca("%s/sandbox-server-%d",optarg_chroot,(int)getpid());
 361                 chrooted_createdir(chroot_pid_dir,(!optarg_setuid ? (uid_t)-1 : want_uid),(!optarg_setgid ? (gid_t)-1 : want_gid),
 362                                 TRUE);  /* lock */
 363                 chroot_pid_hashkey_dir=captive_printf_alloca("%s/%s",chroot_pid_dir,chroot_hashkey);
 364                 chrooted_createdir(chroot_pid_hashkey_dir,(!optarg_setuid ? (uid_t)-1 : want_uid),(!optarg_setgid ? (gid_t)-1 : want_gid),
 365                                 FALSE); /* lock */
 366                 if (chroot(chroot_pid_hashkey_dir))
 367                         fatal("Failed to chroot(\"%s\"): %m",chroot_pid_hashkey_dir);
 368                 if (chdir("/"))
 369                         fatal("Failed to chdir(\"%s\"): %m","/");
 370                 /* Now it is safe to set umask(0000) as we are protected by 'chroot_hashkey'.
 371                  * We need it to permit our spawning parent to hardlink its sockets to us.
 372                  */
 373                 umask(0000);
 374                 if (umask(0000)!=0000)
 375                         fatal("Failed to set umask(0%o): %m",0000);
 376                 if (want_uid_name) {
 377                         printf("chroot_pid_hashkey_dir=%s\n",chroot_pid_hashkey_dir);
 378                         chrooted_orbit_dir=g_strdup_printf("/tmp/orbit-%s",want_uid_name);
 379                         printf("chrooted_orbit_dir=%s\n",chrooted_orbit_dir);
 380                         }
 381                 }
 382
 383         if (fragile && !optarg_setgid)
 384                 fatal("Fragile setuid/root environment but no --setgid set");
 385         if (optarg_setgid) {
 386                 if (!want_gid || setgid(want_gid))
 387                         fatal("Failed to setgid(%d)",(!want_gid ? -1 : (int)want_gid));
 388                 if (setgroups(1 /* size */,&want_gid))
 389                         fatal("Failed to setgroups(1,[%d])",(!want_gid ? -1 : (int)want_gid));
 390                 }
 391         if (fragile && !optarg_setuid)
 392                 fatal("Fragile setuid/root environment but no --setuid set");
 393         if (optarg_setuid) {
 394                 if (!want_uid || setuid(want_uid))
 395                         fatal("Failed to setuid(%d)",(!want_uid ? -1 : (int)want_uid));
 396                 }
 397
 398         /* Prepare /tmp for /tmp/orbit-$username directories for ORBit2
 399          * and also for parent's hardlink to its /tmp/captive-orbit-$pid directory. */
 400         if (optarg_chroot) {
 401                 if (mkdir("/tmp",S_ISVTX|0777))
 402                         fatal("Failed to mkdir(\"%s\"): %m","/tmp");
 403                 if (mkdir("/etc",0700))
 404                         fatal("Failed to mkdir(\"%s\"): %m","/etc");
 405                 if (want_uid_name && want_uid && want_gid) {
 406 FILE *f;
 407                         if (!(f=fopen("/etc/passwd","w")))
 408                                 fatal("Failed to fopen(\"%s\",\"w\"): %m","/etc/passwd");
 409                         if (0>fprintf(f,"%s:*:%d:%d:%s:%s:/bin/false",want_uid_name,(int)want_uid,(int)want_gid,want_uid_name,optarg_chroot))
 410                                 fatal("Failed to fprintf(\"%s\"): %m","/etc/passwd");
 411                         if (fclose(f))
 412                                 fatal("Failed to fclose(\"%s\"): %m","/etc/passwd");
 413                         }
 414                 }
 415
 416         if (fragile) {
 417 gid_t gid_list[2];
 418 int gid_list_size,i;
 419
 420                 if (getuid()!=want_uid)
 421                         fatal("getuid()=%d != want_uid=%d",(int)getuid(),(int)want_uid);
 422                 if (geteuid()!=want_uid)
 423                         fatal("geteuid()=%d != want_uid=%d",(int)geteuid(),(int)want_uid);
 424                 if (getgid()!=want_gid)
 425                         fatal("getgid()=%d != want_gid=%d",(int)getgid(),(int)want_gid);
 426                 if (getegid()!=want_gid)
 427                         fatal("getegid()=%d != want_gid=%d",(int)getegid(),(int)want_gid);
 428                 gid_list_size=getgroups(G_N_ELEMENTS(gid_list),gid_list);
 429                 for (i=0;i<gid_list_size;i++) {
 430                         if (gid_list[i]!=want_gid)
 431                                 fatal("getgroups() list member @%d %d != want_gid=%d",i,(int)gid_list[i],(int)want_gid);
 432                         }
 433                 }
 434 }
 435
 436
 437 int main(int argc,char **argv)
 438 {
 439 poptContext context;
 440 int errint;
 441 const char *cmd_arg;
 442 struct captive_options options;
 443 gboolean fragile;
 444
 445         g_log_set_always_fatal(~(0
 446                         |G_LOG_LEVEL_MESSAGE
 447                         |G_LOG_LEVEL_INFO
 448                         |G_LOG_LEVEL_DEBUG
 449                         ));
 450
 451         fatal_argv0=argv[0];
 452         fragile=(getuid()!=geteuid() || getuid()==0 || geteuid()==0);
 453
 454 #ifndef MAINTAINER_MODE
 455         if (fragile && (argc!=1 || argv[1]))
 456                 fatal("Arguments invalid as running in fragile setuid/root environment");
 457
 458         if (fragile)
 459                 chroot_setup(TRUE);
 460 #endif /* MAINTAINER_MODE */
 461
 462         /* Initialize the i18n stuff */
 463         setlocale(LC_ALL,"");
 464         bindtextdomain(PACKAGE,LOCALEDIR);
 465         textdomain(PACKAGE);
 466
 467         /* Initialize GObject subsystem of GLib. */
 468         g_type_init();
 469
 470         captive_options_init(&options);
 471         captive_options=&options;       /* for parsing by 'CAPTIVE_POPT_INCLUDE' */
 472
 473         context=poptGetContext(
 474                         PACKAGE,        /* name */
 475                         argc,(/*en-const*/const char **)argv,   /* argc,argv */
 476                         popt_table,     /* options */
 477                         POPT_CONTEXT_POSIXMEHARDER);    /* flags; && !POPT_CONTEXT_KEEP_FIRST */
 478         if (context==NULL) {
 479                 g_assert_not_reached(); /* argument recognization args_error */
 480                 return EXIT_FAILURE;
 481                 }
 482         errint=poptReadDefaultConfig(context,
 483                         TRUE);  /* useEnv */
 484         if (errint!=0) {
 485                 g_assert_not_reached(); /* argument recognization args_error */
 486                 return EXIT_FAILURE;
 487                 }
 488         errint=poptGetNextOpt(context);
 489         if (errint!=-1) {
 490                 g_assert_not_reached(); /* some non-callbacked argument reached */
 491                 return EXIT_FAILURE;
 492                 }
 493         cmd_arg=poptPeekArg(context);
 494         if (cmd_arg) {
 495                 g_assert_not_reached(); /* some non-option argument reached */
 496                 return EXIT_FAILURE;
 497                 }
 498         /* 'cmd_arg'-style args gets cleared by 'poptFreeContext(context);' below */
 499         poptFreeContext(context);
 500
 501 #ifdef MAINTAINER_MODE
 502         chroot_setup(FALSE);
 503 #endif /* MAINTAINER_MODE */
 504
 505         captive_options=NULL;   /* already parsed by 'CAPTIVE_POPT_INCLUDE' */
 506
 507         captive_corba_sandbox_child(chrooted_orbit_dir);
 508
 509         g_assert_not_reached();
 510         return EXIT_SUCCESS;
 511 }