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
  42
  43 /* CONFIG: */
  44
  45 #define CHROOT_PATH_HASHKEY_LENGTH (64)
  46
  47
  48 GQuark sandbox_server_main_error_quark(void)
  49 {
  50 GQuark r=0;
  51
  52         if (!r)
  53                 r=g_quark_from_static_string("sandbox-server");
  54
  55         return r;
  56 }
  57
  58
  59 static gchar *optarg_setuid=CAPTIVE_SANDBOX_SETUID;
  60 static gchar *optarg_setgid=CAPTIVE_SANDBOX_SETGID;
  61 static gchar *optarg_chroot=CAPTIVE_SANDBOX_CHROOT;
  62
  63 static const struct poptOption popt_table[]={
  64 #define SANDBOX_SERVER_POPT(longname,argInfoP,argP,descripP,argDescripP) \
  65                 { \
  66                         longName: (longname), \
  67                         shortName: 0, \
  68                         argInfo: (argInfoP), \
  69                         arg: (void *)argP, \
  70                         val: 0, \
  71                         descrip: (descripP), \
  72                         argDescrip: (argDescripP), \
  73                 }
  74
  75                 SANDBOX_SERVER_POPT("setuid"  ,POPT_ARG_STRING,&optarg_setuid,N_("Username or UID to become; \"-\" for disable"),N_("UID")),
  76                 SANDBOX_SERVER_POPT("setgid"  ,POPT_ARG_STRING,&optarg_setgid,N_("Groupname or GID to become; \"-\" for disable"),N_("GID")),
  77                 SANDBOX_SERVER_POPT("chroot"  ,POPT_ARG_STRING,&optarg_chroot,N_("Pathname to directory for chroot(2); \"-\" for disable"),N_("directory")),
  78
  79 #undef SANDBOX_SERVER_POPT
  80                 POPT_AUTOHELP
  81                 POPT_TABLEEND
  82                 };
  83
  84
  85 static gchar *fatal_argv0;
  86
  87 static void fatal(const char *fmt,...)
  88 {
  89 va_list ap;
  90
  91         fprintf(stderr,"%s: ",fatal_argv0);
  92         va_start(ap,fmt);
  93         vfprintf(stderr,fmt,ap);
  94         va_end(ap);
  95         fprintf(stderr,"!\nAborting!\n");
  96         exit(EXIT_FAILURE);
  97         /* NOTREACHED */
  98         for (;;);
  99 }
 100
 101 static void check_dir_safety(const gchar *dir)
 102 {
 103 gchar *local_dir;
 104 const gchar *cs;
 105 static gint depth=0;
 106
 107         if (++depth>=1000)
 108                 fatal("Loop count >=%d during check_dir_safety(\"%s\")",depth,dir);
 109
 110         if (*dir!='/')
 111                 fatal("chroot path \"%s\" not absolute",dir);
 112         dir=captive_printf_alloca("%s/",dir);
 113         local_dir=(gchar *)captive_strdup_alloca(dir);
 114         for (cs=dir;cs;cs=strchr(cs+1,'/')) {
 115 struct stat statbuf;
 116
 117                 g_assert(*cs=='/');
 118                 /* Include the trailing '/' to resolve the root directory as "/". */
 119                 memcpy(local_dir,dir,cs+1-dir);
 120                 local_dir[cs+1-dir]=0;
 121                 if (lstat(local_dir,&statbuf))
 122                         fatal("lstat(\"%s\") of chroot path component: %m",local_dir);
 123                 if (S_ISLNK(statbuf.st_mode)) {
 124 char linkbuf[PATH_MAX];
 125 int linkbuflen;
 126
 127                         if (0>(linkbuflen=readlink(local_dir,linkbuf,sizeof(linkbuf)-1)))
 128                                 fatal("readlink(\"%s\") of chroot path component: %m",local_dir);
 129                         linkbuf[linkbuflen]=0;
 130                         check_dir_safety(linkbuf);
 131                         if (stat(local_dir,&statbuf))   /* NOT lstat(2) */
 132                                 fatal("stat(\"%s\") of chroot path component: %m",local_dir);
 133                         }
 134                 if (!S_ISDIR(statbuf.st_mode))
 135                         fatal("lstat/stat(\"%s\") of chroot path component is !S_ISDIR",local_dir);
 136                 if (statbuf.st_uid!=0)
 137                         fatal("lstat/stat(\"%s\") of chroot path component has UID %d !=0",local_dir,(int)statbuf.st_uid);
 138                 if (statbuf.st_gid!=0)
 139                         fatal("lstat/stat(\"%s\") of chroot path component has GID %d !=0",local_dir,(int)statbuf.st_gid);
 140                 if ((statbuf.st_mode&(S_IFDIR|S_ISVTX|0111)) != (S_IFDIR|0111))
 141                         fatal("lstat/stat(\"%s\") of chroot path component has mode 0%o !=04[01]111",local_dir,(int)statbuf.st_mode);
 142                 }
 143
 144         depth--;
 145 }
 146
 147 static void unlink_recursive_suidsafe(const gchar *pathname)
 148 {
 149 DIR *dir;
 150 struct dirent *dirent;
 151 static gint depth=0;
 152
 153         if (++depth>=1000)
 154                 fatal("Loop count >=%d during unlink_recursive_suidsafe(\"%s\")",depth,pathname);
 155
 156         if (!(dir=opendir(pathname))) {
 157                 if (errno!=ENOTDIR)
 158                         fatal("Cannot opendir(\"%s\") to delete leftover sandbox files: %m",pathname);
 159                 /* errno==ENOTDIR, a regular file */
 160                 if (unlink(pathname))
 161                         fatal("Cannot pathname(\"%s\") to delete leftover sandbox files: %m",pathname);
 162                 goto done;
 163                 }
 164         while (errno=0,(dirent=readdir(dir))) {
 165 gchar *dirent_path;
 166
 167                 if (!strcmp(dirent->d_name,".") || !strcmp(dirent->d_name,".."))
 168                         continue;
 169                 dirent_path=g_strdup_printf("%s/%s",pathname,dirent->d_name);
 170                 unlink_recursive_suidsafe(dirent_path);
 171                 g_free(dirent_path);
 172                 }
 173         if (errno)
 174                 fatal("Cannot readdir(\"%s\") during delete of leftover sandbox files: %m",pathname);
 175         if (closedir(dir))
 176                 fatal("Cannot closedir(\"%s\") during delete of leftover sandbox files: %m",pathname);
 177         if (rmdir(pathname))
 178                 fatal("Cannot rmdir(\"%s\") during delete of leftover sandbox files: %m",pathname);
 179
 180 done:
 181         depth--;
 182 }
 183
 184 static void chrooted_createdir(const gchar *dir,uid_t uid,gid_t gid)
 185 {
 186         if (mkdir(dir,0711)) {
 187                 if (errno!=EEXIST)
 188                         fatal("Failed to create chroot directory \"%s\": %m",dir);
 189                 unlink_recursive_suidsafe(dir);
 190                 if (mkdir(dir,0711))
 191                         fatal("Failed to create chroot directory \"%s\" after attempted unlink: %m",dir);
 192                 }
 193         if (chown(dir,uid,gid))
 194                 fatal("Failed to chown(\"%s\",%d,%d): %m",dir,uid,gid);
 195         if (chmod(dir,0711))    /* Just to be safe after chown(2); should be already done by mkdir(2). */
 196                 fatal("Failed to chmod(\"%s\",0%o): %m",dir,0711);
 197 }
 198
 199 static const gchar *chrooted_orbit_dir;
 200
 201 static void chroot_setup(gboolean fragile)
 202 {
 203 uid_t want_uid=0;
 204 const gchar *want_uid_name=NULL;
 205 gid_t want_gid=0;
 206 char *endptr;
 207
 208         if (fragile) {
 209                 captive_sandbox_fd_closeup(2 /* STDERR */ +1);
 210                 clearenv();
 211                 }
 212
 213 #define CLEANEMPTY(var) G_STMT_START { \
 214                 if ((var) && (!*(var) || *(var)=='-')) \
 215                         (var)=NULL; \
 216                 } G_STMT_END
 217         CLEANEMPTY(optarg_setgid);
 218         CLEANEMPTY(optarg_setuid);
 219         CLEANEMPTY(optarg_chroot);
 220 #undef CLEANEMPTY
 221
 222         if (optarg_setgid) {
 223 long want_gidl;
 224
 225                 want_gidl=strtol(optarg_setgid,&endptr,10);
 226                 if (!endptr || !*endptr) {
 227                         want_gid=want_gidl;
 228                         if (want_gidl<=0 || want_gid!=(gid_t)want_gidl)
 229                                 fatal("Numeric setgid not parsable: %s",optarg_setgid);
 230                         }
 231                 else {
 232 struct group *want_gid_group=NULL;
 233                         if (!(want_gid_group=getgrnam(optarg_setgid)))
 234                                 fatal("Unable to query setgid group name \"%s\"",optarg_setgid);
 235                         want_gid=want_gid_group->gr_gid;
 236                         }
 237                 }
 238
 239         if (optarg_setuid) {
 240 long want_uidl;
 241 struct passwd *want_uid_passwd;
 242                 want_uidl=strtol(optarg_setuid,&endptr,10);
 243                 if (!endptr || !*endptr) {
 244                         want_uid=want_uidl;
 245                         if (want_uidl<=0 || want_uid!=(gid_t)want_uidl)
 246                                 fatal("Numeric setuid not parsable: %s",optarg_setuid);
 247                         }
 248                 else {
 249                         if (!(want_uid_passwd=getpwnam(optarg_setuid)))
 250                                 fatal("Unable to query setuid user name \"%s\"",optarg_setuid);
 251                         want_uid=want_uid_passwd->pw_uid;
 252                         }
 253                 if (!want_uid)
 254                         fatal("Unable to detect setuid UID");
 255                 if (!(want_uid_passwd=getpwuid(want_uid)))
 256                         fatal("Unable to query name of UID %d",(int)want_uid);
 257                 want_uid_name=captive_strdup_alloca(want_uid_passwd->pw_name);
 258                 }
 259
 260         if (fragile && !optarg_chroot)
 261                 fatal("Fragile setuid/root environment but no --chroot set");
 262         if (optarg_chroot) {
 263 const gchar *chroot_pid_dir,*chroot_pid_hashkey_dir;
 264 GRand *grand;
 265 gchar chroot_hashkey[CHROOT_PATH_HASHKEY_LENGTH+1],*s;
 266 gint gi;
 267
 268                 check_dir_safety(optarg_chroot);
 269                 if (!(grand=g_rand_new()))      /* I hope g_rand_new() is security-safe. It looks so. */
 270                         fatal("Cannot initialize random number generator g_rand_new()");
 271                 for (s=chroot_hashkey;s<chroot_hashkey+CHROOT_PATH_HASHKEY_LENGTH;s++) {
 272                         gi=g_rand_int_range(grand,0,10+26+26);
 273                         /**/ if (gi>=0 && gi<10)
 274                                 *s='0'+gi-(0);
 275                         else if (gi>=10+0 && gi<10+26)
 276                                 *s='a'+gi-(10);
 277                         else if (gi>=10+26+0 && gi<10+26+26)
 278                                 *s='A'+gi-(10+26);
 279                         else g_assert_not_reached();
 280                         }
 281                 g_rand_free(grand);
 282                 *s=0;
 283                 chroot_pid_dir=captive_printf_alloca("%s/sandbox-server-%d",optarg_chroot,(int)getpid());
 284                 chrooted_createdir(chroot_pid_dir,(!optarg_setuid ? (uid_t)-1 : want_uid),(!optarg_setgid ? (gid_t)-1 : want_gid));
 285                 chroot_pid_hashkey_dir=captive_printf_alloca("%s/%s",chroot_pid_dir,chroot_hashkey);
 286                 chrooted_createdir(chroot_pid_hashkey_dir,(!optarg_setuid ? (uid_t)-1 : want_uid),(!optarg_setgid ? (gid_t)-1 : want_gid));
 287                 if (chroot(chroot_pid_hashkey_dir))
 288                         fatal("Failed to chroot(\"%s\"): %m",chroot_pid_hashkey_dir);
 289                 if (chdir("/"))
 290                         fatal("Failed to chdir(\"%s\"): %m","/");
 291                 /* Now it is safe to set umask(0000) as we are protected by 'chroot_hashkey'.
 292                  * We need it to permit our spawning parent to hardlink its sockets to us.
 293                  */
 294                 umask(0000);
 295                 if (umask(0000)!=0000)
 296                         fatal("Failed to set umask(0%o): %m",0000);
 297                 if (want_uid_name) {
 298                         printf("chroot_pid_hashkey_dir=%s\n",chroot_pid_hashkey_dir);
 299                         chrooted_orbit_dir=g_strdup_printf("/tmp/orbit-%s",want_uid_name);
 300                         printf("chrooted_orbit_dir=%s\n",chrooted_orbit_dir);
 301                         }
 302                 }
 303
 304         if (fragile && !optarg_setgid)
 305                 fatal("Fragile setuid/root environment but no --setgid set");
 306         if (optarg_setgid) {
 307                 if (!want_gid || setgid(want_gid))
 308                         fatal("Failed to setgid(%d)",(!want_gid ? -1 : (int)want_gid));
 309                 if (setgroups(1 /* size */,&want_gid))
 310                         fatal("Failed to setgroups(1,[%d])",(!want_gid ? -1 : (int)want_gid));
 311                 }
 312         if (fragile && !optarg_setuid)
 313                 fatal("Fragile setuid/root environment but no --setuid set");
 314         if (optarg_setuid) {
 315                 if (!want_uid || setuid(want_uid))
 316                         fatal("Failed to setuid(%d)",(!want_uid ? -1 : (int)want_uid));
 317                 }
 318
 319         /* Prepare /tmp for /tmp/orbit-$username directories for ORBit2
 320          * and also for parent's hardlink to its /tmp/captive-orbit-$pid directory. */
 321         if (optarg_chroot) {
 322                 if (mkdir("/tmp",S_ISVTX|0777))
 323                         fatal("Failed to mkdir(\"%s\"): %m","/tmp");
 324                 if (mkdir("/etc",0700))
 325                         fatal("Failed to mkdir(\"%s\"): %m","/etc");
 326                 if (want_uid_name && want_uid && want_gid) {
 327 FILE *f;
 328                         if (!(f=fopen("/etc/passwd","w")))
 329                                 fatal("Failed to fopen(\"%s\",\"w\"): %m","/etc/passwd");
 330                         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))
 331                                 fatal("Failed to fprintf(\"%s\"): %m","/etc/passwd");
 332                         if (fclose(f))
 333                                 fatal("Failed to fclose(\"%s\"): %m","/etc/passwd");
 334                         }
 335                 }
 336
 337         if (fragile) {
 338 gid_t gid_list[2];
 339 int gid_list_size,i;
 340
 341                 if (getuid()!=want_uid)
 342                         fatal("getuid()=%d != want_uid=%d",(int)getuid(),(int)want_uid);
 343                 if (geteuid()!=want_uid)
 344                         fatal("geteuid()=%d != want_uid=%d",(int)geteuid(),(int)want_uid);
 345                 if (getgid()!=want_gid)
 346                         fatal("getgid()=%d != want_gid=%d",(int)getgid(),(int)want_gid);
 347                 if (getegid()!=want_gid)
 348                         fatal("getegid()=%d != want_gid=%d",(int)getegid(),(int)want_gid);
 349                 gid_list_size=getgroups(G_N_ELEMENTS(gid_list),gid_list);
 350                 for (i=0;i<gid_list_size;i++) {
 351                         if (gid_list[i]!=want_gid)
 352                                 fatal("getgroups() list member @%d %d != want_gid=%d",i,(int)gid_list[i],(int)want_gid);
 353                         }
 354                 }
 355 }
 356
 357
 358 int main(int argc,char **argv)
 359 {
 360 poptContext context;
 361 int errint;
 362 const char *cmd_arg;
 363 struct captive_options options;
 364 gboolean fragile;
 365
 366         g_log_set_always_fatal(~(0
 367                         |G_LOG_LEVEL_MESSAGE
 368                         |G_LOG_LEVEL_INFO
 369                         |G_LOG_LEVEL_DEBUG
 370                         ));
 371
 372         fatal_argv0=argv[0];
 373         fragile=(getuid()!=geteuid() || getuid()==0 || geteuid()==0);
 374
 375 #ifndef MAINTAINER_MODE
 376         if (fragile && (argc!=1 || argv[1]))
 377                 fatal("Arguments invalid as running in fragile setuid/root environment");
 378
 379         if (fragile)
 380                 chroot_setup(TRUE);
 381 #endif /* MAINTAINER_MODE */
 382
 383         /* Initialize the i18n stuff */
 384         setlocale(LC_ALL,"");
 385         bindtextdomain(PACKAGE,LOCALEDIR);
 386         textdomain(PACKAGE);
 387
 388         /* Initialize GObject subsystem of GLib. */
 389         g_type_init();
 390
 391         captive_options_init(&options);
 392         captive_options=&options;       /* for parsing by 'CAPTIVE_POPT_INCLUDE' */
 393
 394         context=poptGetContext(
 395                         PACKAGE,        /* name */
 396                         argc,(/*en-const*/const char **)argv,   /* argc,argv */
 397                         popt_table,     /* options */
 398                         POPT_CONTEXT_POSIXMEHARDER);    /* flags; && !POPT_CONTEXT_KEEP_FIRST */
 399         if (context==NULL) {
 400                 g_assert_not_reached(); /* argument recognization args_error */
 401                 return EXIT_FAILURE;
 402                 }
 403         errint=poptReadDefaultConfig(context,
 404                         TRUE);  /* useEnv */
 405         if (errint!=0) {
 406                 g_assert_not_reached(); /* argument recognization args_error */
 407                 return EXIT_FAILURE;
 408                 }
 409         errint=poptGetNextOpt(context);
 410         if (errint!=-1) {
 411                 g_assert_not_reached(); /* some non-callbacked argument reached */
 412                 return EXIT_FAILURE;
 413                 }
 414         cmd_arg=poptPeekArg(context);
 415         if (cmd_arg) {
 416                 g_assert_not_reached(); /* some non-option argument reached */
 417                 return EXIT_FAILURE;
 418                 }
 419         /* 'cmd_arg'-style args gets cleared by 'poptFreeContext(context);' below */
 420         poptFreeContext(context);
 421
 422 #ifdef MAINTAINER_MODE
 423         chroot_setup(FALSE);
 424 #endif /* MAINTAINER_MODE */
 425
 426         captive_options=NULL;   /* already parsed by 'CAPTIVE_POPT_INCLUDE' */
 427
 428         captive_corba_sandbox_child(chrooted_orbit_dir);
 429
 430         g_assert_not_reached();
 431         return EXIT_SUCCESS;
 432 }