src/vsh.c

   1 /*
   2  * Marc E. Fiuczynski <mef@cs.princeton.edu>
   3  *
   4  * Copyright (c) 2004 The Trustees of Princeton University (Trustees).
   5  *
   6  * vsh is free software; you can redistribute it and/or modify it
   7  * under the terms of the GNU General Public License as published by
   8  * the Free Software Foundation; either version 2, or (at your option)
   9  * any later version.
  10  *
  11  * vsh is distributed in the hope that it will be useful, but WITHOUT
  12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
  13  * or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public
  14  * License for more details.
  15  *
  16  * You should have received a copy of the GNU General Public License
  17  * along with Poptop; see the file COPYING.  If not, write to the Free
  18  * Software Foundation, 59 Temple Place - Suite 330, Boston, MA
  19  * 02111-1307, USA.
  20  */
  21
  22 #ifdef HAVE_CONFIG_H
  23 #  include <config.h>
  24 #endif
  25 #include "compat.h"
  26
  27 #include <stdio.h>
  28 #include <stdlib.h>
  29 #include <string.h>
  30 #include <stdlib.h>
  31 #include <errno.h>
  32 #include <pwd.h>
  33 #include <unistd.h>
  34 #include <syscall.h>
  35 #include <sys/syscall.h>
  36 #include <asm/unistd.h>
  37 #include <sys/mount.h>
  38 #include <sys/types.h>
  39 #include <sys/stat.h>
  40 #include <fcntl.h>
  41 #include <ctype.h>
  42
  43 //--------------------------------------------------------------------
  44 #include "linuxcaps.h"
  45 #include "vserver.h"
  46
  47 /* Null byte made explicit */
  48 #define NULLBYTE_SIZE                    1
  49
  50 /* Base for all vserver roots for chroot */
  51 #define VSERVER_ROOT_BASE       "/vservers"
  52
  53 /* Change to root:root (before entering new context) */
  54 static int setuidgid_root()
  55 {
  56         if (setgid(0) < 0) {
  57                 fprintf(stderr, "setgid error\n");
  58                 return -1;
  59         }
  60         if (setuid(0) < 0) {
  61                 fprintf(stderr, "setuid error\n");
  62                 return -1;
  63         }
  64         return 0;
  65 }
  66
  67 static void compute_new_root(char *base, char **root, uid_t uid)
  68 {
  69         int             root_len;
  70         struct passwd   *pwd;
  71
  72         if ((pwd = getpwuid(uid)) == NULL) {
  73                 perror("vserver: getpwuid error ");
  74                 exit(1);
  75         }
  76
  77         root_len =
  78                 strlen(base) + strlen("/") +
  79                 strlen(pwd->pw_name)      + NULLBYTE_SIZE;
  80         (*root) = (char *)malloc(root_len);
  81         if ((*root) == NULL) {
  82                 perror("vserver: malloc error ");
  83                 exit(1);
  84         }
  85
  86         sprintf((*root), "%s/%s", base, pwd->pw_name);
  87         (*root)[root_len - 1] = '\0';
  88 }
  89
  90 /* Example: sandbox_root = /vservers/bnc, relpath = /proc/1 */
  91 static int sandbox_file_exists(char *sandbox_root, char *relpath)
  92 {
  93         struct stat stat_buf;
  94         char   *file;
  95         int    len, exists = 0;
  96
  97         len = strlen(sandbox_root) + strlen(relpath) + NULLBYTE_SIZE;
  98         if ((file = (char *)malloc(len)) == NULL) {
  99                 perror("vserver: malloc error ");
 100                 exit(1);
 101         }
 102         sprintf(file, "%s%s", sandbox_root, relpath);
 103         file[len - 1] = '\0';
 104         if (stat(file, &stat_buf) == 0) {
 105                 exists = 1;
 106         }
 107
 108
 109         free(file);
 110         return exists;
 111 }
 112
 113 static int proc_mounted(char *sandbox_root)
 114 {
 115         return sandbox_file_exists(sandbox_root, "/proc/1");
 116 }
 117
 118 static int devpts_mounted(char *sandbox_root)
 119 {
 120         return sandbox_file_exists(sandbox_root, "/dev/pts/0");
 121 }
 122
 123 static void mount_proc(char *sandbox_root,uid_t uid)
 124 {
 125         char        *source = "/proc";
 126         char        *target;
 127         int         len;
 128
 129         len = strlen(sandbox_root) + strlen("/") + strlen("proc") + NULLBYTE_SIZE;
 130         if ((target = (char *)malloc(len)) == NULL) {
 131                 perror("vserver: malloc error ");
 132                 exit(1);
 133         }
 134
 135         sprintf(target, "%s/proc", sandbox_root);
 136         target[len - 1] = '\0';
 137         if (!proc_mounted(sandbox_root))
 138                 mount(source, target, "proc", MS_BIND | MS_RDONLY, NULL);
 139
 140         free(target);
 141 }
 142
 143 static void mount_devpts(char *sandbox_root)
 144 {
 145         char        *source = "/dev/pts";
 146         char        *target;
 147         int         len;
 148
 149         len = strlen(sandbox_root) + strlen("/") + strlen("dev/pts") + NULLBYTE_SIZE;
 150         if ((target = (char *)malloc(len)) == NULL) {
 151                 perror("vserver: malloc error ");
 152                 exit(1);
 153         }
 154
 155         sprintf(target, "%s/dev/pts", sandbox_root);
 156         target[len - 1] = '\0';
 157         if (!devpts_mounted(sandbox_root))
 158                 mount(source, target, "devpts", 0, NULL);
 159
 160         free(target);
 161 }
 162
 163 static int sandbox_chroot(uid_t uid)
 164 {
 165         char *sandbox_root = NULL;
 166
 167         compute_new_root(VSERVER_ROOT_BASE,&sandbox_root, uid);
 168         mount_proc(sandbox_root,uid);
 169         mount_devpts(sandbox_root);
 170         if (chroot(sandbox_root) < 0) {
 171                 fprintf(stderr,"vserver: chroot error (%s): ",sandbox_root);
 172                 perror("");
 173                 exit(1);
 174         }
 175         if (chdir("/") < 0) {
 176                 perror("vserver: chdir error ");
 177                 exit(1);
 178         }
 179         return 0;
 180 }
 181
 182 #ifndef CAP_CONTEXT
 183 #  define CAP_CONTEXT   29
 184 #endif
 185
 186 static struct {
 187         const char *option;
 188         int bit;
 189 }tbcap[]={
 190         // The following capabilities are normally available
 191         // to vservers administrator, but are place for
 192         // completeness
 193         {"CAP_CHOWN",CAP_CHOWN},
 194         {"CAP_DAC_OVERRIDE",CAP_DAC_OVERRIDE},
 195         {"CAP_DAC_READ_SEARCH",CAP_DAC_READ_SEARCH},
 196         {"CAP_FOWNER",CAP_FOWNER},
 197         {"CAP_FSETID",CAP_FSETID},
 198         {"CAP_KILL",CAP_KILL},
 199         {"CAP_SETGID",CAP_SETGID},
 200         {"CAP_SETUID",CAP_SETUID},
 201         {"CAP_SETPCAP",CAP_SETPCAP},
 202         {"CAP_SYS_TTY_CONFIG",CAP_SYS_TTY_CONFIG},
 203         {"CAP_LEASE",CAP_LEASE},
 204         {"CAP_SYS_CHROOT",CAP_SYS_CHROOT},
 205
 206         // Those capabilities are not normally available
 207         // to vservers because they are not needed and
 208         // may represent a security risk
 209         {"CAP_LINUX_IMMUTABLE",CAP_LINUX_IMMUTABLE},
 210         {"CAP_NET_BIND_SERVICE",CAP_NET_BIND_SERVICE},
 211         {"CAP_NET_BROADCAST",CAP_NET_BROADCAST},
 212         {"CAP_NET_ADMIN",       CAP_NET_ADMIN},
 213         {"CAP_NET_RAW", CAP_NET_RAW},
 214         {"CAP_IPC_LOCK",        CAP_IPC_LOCK},
 215         {"CAP_IPC_OWNER",       CAP_IPC_OWNER},
 216         {"CAP_SYS_MODULE",CAP_SYS_MODULE},
 217         {"CAP_SYS_RAWIO",       CAP_SYS_RAWIO},
 218         {"CAP_SYS_PACCT",       CAP_SYS_PACCT},
 219         {"CAP_SYS_ADMIN",       CAP_SYS_ADMIN},
 220         {"CAP_SYS_BOOT",        CAP_SYS_BOOT},
 221         {"CAP_SYS_NICE",        CAP_SYS_NICE},
 222         {"CAP_SYS_RESOURCE",CAP_SYS_RESOURCE},
 223         {"CAP_SYS_TIME",        CAP_SYS_TIME},
 224         {"CAP_MKNOD",           CAP_MKNOD},
 225         {"CAP_CONTEXT",         CAP_CONTEXT},
 226         {NULL,0}
 227 };
 228
 229 #define VSERVERCONF "/etc/vservers/"
 230 static unsigned get_remove_cap(char *name) {
 231         FILE     *fb;
 232         unsigned remove_cap;
 233
 234         char *vserverconf;
 235         int vserverconflen;
 236
 237         remove_cap = /* NOTE: keep in sync with chcontext.c */
 238                 (1<<CAP_LINUX_IMMUTABLE)|
 239                 (1<<CAP_NET_BROADCAST)|
 240                 (1<<CAP_NET_ADMIN)|
 241                 (1<<CAP_NET_RAW)|
 242                 (1<<CAP_IPC_LOCK)|
 243                 (1<<CAP_IPC_OWNER)|
 244                 (1<<CAP_SYS_MODULE)|
 245                 (1<<CAP_SYS_RAWIO)|
 246                 (1<<CAP_SYS_PACCT)|
 247                 (1<<CAP_SYS_ADMIN)|
 248                 (1<<CAP_SYS_BOOT)|
 249                 (1<<CAP_SYS_NICE)|
 250                 (1<<CAP_SYS_RESOURCE)|
 251                 (1<<CAP_SYS_TIME)|
 252                 (1<<CAP_MKNOD)|
 253                 (1<<CAP_CONTEXT)|
 254                 0
 255                 ;
 256
 257         /*
 258          * find out which capabilities to put back in by reading the conf file
 259          */
 260
 261         /* construct the pathname to the conf file */
 262         vserverconflen = strlen(VSERVERCONF) + strlen(name) + strlen(".conf") + NULLBYTE_SIZE;
 263         vserverconf    = (char *)malloc(vserverconflen);
 264         sprintf(vserverconf, "%s%s.conf", VSERVERCONF, name);
 265
 266         /* open the conf file for reading */
 267         fb = fopen(vserverconf,"r");
 268         if (fb != NULL) {
 269                 unsigned cap;
 270                 size_t index;
 271                 size_t len;
 272                 char buffer[1000], *p;
 273
 274                 /* the conf file file exist */
 275                 while((p=fgets(buffer,sizeof(buffer)-1,fb))!=NULL) {
 276
 277                         /* walk past leading spaces */
 278                         index = 0;
 279                         len = strnlen(buffer,sizeof(buffer)-1);
 280                         while(isspace((int)buffer[index])) {
 281                                 if (index < len) {
 282                                         index++;
 283                                 } else {
 284                                         goto out;
 285                                 }
 286                         }
 287
 288                         if (buffer[index] == '#') continue;
 289
 290                         /* check if it is the S_CAPS */
 291                         if ((p=strstr(&buffer[index],"S_CAPS"))!=NULL) {
 292                                 int j;
 293                                 cap = 0;
 294
 295                                 /* what follows is a bunch of error
 296                                    checking to parse the S_CAPS="..."
 297                                    string */
 298
 299                                 /* adjust index into buffer */
 300                                 index+= (p-&buffer[index])+strlen("S_CAPS");
 301
 302                                 /* skip over whitespace */
 303                                 while(isspace((int)buffer[index])) {
 304                                         if (index < len) {
 305                                                 index++;
 306                                         } else {
 307                                         /* parse error */
 308                                                 goto out;
 309                                         }
 310                                 }
 311
 312                                 /* expecting to see = sign */
 313                                 if (buffer[index++]!='=') {
 314                                         /* parse error */
 315                                         goto out;
 316                                 }
 317
 318                                 /* skip over whitespace */
 319                                 while(isspace((int)buffer[index])) {
 320                                         if (index < len) {
 321                                                 index++;
 322                                         } else {
 323                                                 /* parse error */
 324                                                 goto out;
 325                                         }
 326                                 }
 327
 328                                 /* expecting to see the opening " */
 329                                 if (buffer[index]!='"') {
 330                                         /* parse error */
 331                                         goto out;
 332                                 }
 333
 334                                 /* check to see that we are still within bounds */
 335                                 if (index < len) {
 336                                         index++;
 337                                 } else {
 338                                         /* parse error */
 339                                         goto out;
 340                                 }
 341
 342                                 /* search for the closing " */
 343                                 if((p=strstr(&buffer[index],"\""))==NULL) {
 344                                         /* parse error */
 345                                         goto out;
 346                                 }
 347
 348                                 /* ok... we should now have a bunch of
 349                                    CAP keys words within the quotes */
 350
 351                                 for (j=0; tbcap[j].option != NULL; j++){
 352                                         if ((p=strstr(buffer,tbcap[j].option))!=NULL){
 353                                                 len = strlen(tbcap[j].option);
 354                                                 if (((isspace(*(p-1))) || (*(p-1)=='"')) &&
 355                                                     ((isspace(*(p+len))) || (*(p+len)=='"'))) {
 356                                                         cap |= (1<<tbcap[j].bit);
 357                                                 } else {
 358                                                         /* parse error */
 359                                                         goto out;
 360                                                 }
 361                                         }
 362                                 }
 363                                 remove_cap &= ~cap;
 364                                 break;
 365                         }
 366                 }
 367  out:
 368                 /* close the conf file */
 369                 fclose(fb);
 370         }
 371         return remove_cap;
 372 }
 373
 374 static int sandbox_processes(uid_t uid, unsigned remove_cap)
 375 {
 376         int      context;
 377         int      flags;
 378
 379         /* Unique context */
 380         context = uid;
 381
 382         flags = 0;
 383         flags |= 1; /* VX_INFO_LOCK -- cannot request a new vx_id */
 384         /* flags |= 4; VX_INFO_NPROC -- limit number of procs in a context */
 385
 386         if (vc_new_s_context(context,remove_cap,flags) < 0) {
 387                 perror("vserver: new_s_context error ");
 388                 exit(1);
 389         }
 390         return 0;
 391 }
 392
 393
 394 void runas_slice_user(char *username)
 395 {
 396         struct passwd *pwd;
 397         char          *home_env, *logname_env, *mail_env, *shell_env, *user_env;
 398         int           home_len, logname_len, mail_len, shell_len, user_len;
 399         static char   *envp[10];
 400
 401         if ((pwd = getpwnam(username)) == NULL) {
 402                 perror("vserver: getpwnam error ");
 403                 exit(1);
 404         }
 405
 406         if (setgid(pwd->pw_gid) < 0) {
 407                 perror("vserver: setgid error ");
 408                 exit(1);
 409         }
 410
 411         if (setuid(pwd->pw_uid) < 0) {
 412                 perror("vserver: setuid error ");
 413                 exit(1);
 414         }
 415
 416         if (chdir(pwd->pw_dir) < 0) {
 417                 perror("vserver: chdir error ");
 418                 exit(1);
 419         }
 420
 421         home_len    = strlen("HOME=") + strlen(pwd->pw_dir) + NULLBYTE_SIZE;
 422         logname_len = strlen("LOGNAME=") + strlen(username) + NULLBYTE_SIZE;
 423         mail_len    = strlen("MAIL=/var/spool/mail/") + strlen(username)
 424                 + NULLBYTE_SIZE;
 425         shell_len   = strlen("SHELL=") + strlen(pwd->pw_shell) + NULLBYTE_SIZE;
 426         user_len    = strlen("USER=") + strlen(username) + NULLBYTE_SIZE;
 427
 428         home_env    = (char *)malloc(home_len);
 429         logname_env = (char *)malloc(logname_len);
 430         mail_env    = (char *)malloc(mail_len);
 431         shell_env   = (char *)malloc(shell_len);
 432         user_env    = (char *)malloc(user_len);
 433
 434         if ((home_env    == NULL)  ||
 435             (logname_env == NULL)  ||
 436             (mail_env    == NULL)  ||
 437             (shell_env   == NULL)  ||
 438             (user_env    == NULL)) {
 439                 perror("vserver: malloc error ");
 440                 exit(1);
 441         }
 442
 443         sprintf(home_env, "HOME=%s", pwd->pw_dir);
 444         sprintf(logname_env, "LOGNAME=%s", username);
 445         sprintf(mail_env, "MAIL=/var/spool/mail/%s", username);
 446         sprintf(shell_env, "SHELL=%s", pwd->pw_shell);
 447         sprintf(user_env, "USER=%s", username);
 448
 449         home_env[home_len - 1]       = '\0';
 450         logname_env[logname_len - 1] = '\0';
 451         mail_env[mail_len - 1]       = '\0';
 452         shell_env[shell_len - 1]     = '\0';
 453         user_env[user_len - 1]       = '\0';
 454
 455         envp[0] = home_env;
 456         envp[1] = logname_env;
 457         envp[2] = mail_env;
 458         envp[3] = shell_env;
 459         envp[4] = user_env;
 460         envp[5] = 0;
 461
 462         if ((putenv(home_env)    < 0) ||
 463             (putenv(logname_env) < 0) ||
 464             (putenv(mail_env)    < 0) ||
 465             (putenv(shell_env)   < 0) ||
 466             (putenv(user_env)    < 0)) {
 467                 perror("vserver: putenv error ");
 468                 exit(1);
 469         }
 470 }
 471
 472
 473
 474 void slice_enter(char *context)
 475 {
 476         struct passwd   *pwd;
 477         unsigned remove_cap;
 478         uid_t uid;
 479
 480         if ((pwd = getpwnam(context)) == NULL) {
 481                 fprintf(stderr,"vserver: getpwname(%s) failed",context);
 482                 exit(2);
 483         }
 484
 485         context = (char*)malloc(strlen(pwd->pw_name)+NULLBYTE_SIZE);
 486         if (!context) {
 487                 perror("vserver: malloc failed");
 488                 exit(2);
 489         }
 490         strcpy(context,pwd->pw_name);
 491
 492         if (setuidgid_root() < 0) { /* For chroot, new_s_context */
 493                 fprintf(stderr,"vserver: Could not setuid/setguid to root:root\n");
 494                 exit(2);
 495         }
 496
 497         remove_cap = get_remove_cap(context);
 498
 499         uid = pwd->pw_uid;
 500         if (sandbox_chroot(uid) < 0) {
 501                 fprintf(stderr, "vserver: Could not chroot to vserver root\n");
 502                 exit(2);
 503         }
 504
 505         if (sandbox_processes(uid, remove_cap) < 0) {
 506                 fprintf(stderr, "vserver: Could not sandbox processes in vserver\n");
 507                 exit(2);
 508         }
 509 }
 510
 511 //--------------------------------------------------------------------
 512
 513 #define DEFAULT_SHELL "/bin/sh"
 514
 515 /* Exit statuses for programs like 'env' that exec other programs.
 516    EXIT_FAILURE might not be 1, so use EXIT_FAIL in such programs.  */
 517 enum
 518 {
 519   EXIT_CANNOT_INVOKE = 126,
 520   EXIT_ENOENT = 127
 521 };
 522
 523 extern void slice_enter(char *);
 524 extern void runas_slice_user(char *);
 525
 526 int main(int argc, char **argv)
 527 {
 528     char *context, *username, *shell;
 529     struct passwd   *pwd;
 530     uid_t           uid;
 531     int index, i;
 532
 533     if (argv[0][0]=='-')
 534       index = 1;
 535     else
 536       index = 0;
 537
 538     uid = getuid();
 539     if ((pwd = getpwuid(uid)) == NULL) {
 540       fprintf(stderr,"vsh: getpwnam error failed for %d\n",uid);
 541       exit(1);
 542     }
 543
 544     context = (char*)strdup(pwd->pw_name);
 545     if (!context) {
 546       perror("vsh: strdup failed");
 547       exit(2);
 548     }
 549
 550     /* enter vserver "context" */
 551     slice_enter(context);
 552
 553     /* Now run as username in this context. Note that for PlanetLab's
 554        vserver configuration the context name also happens to be the
 555        "default" username within the vserver context.
 556     */
 557     username = context;
 558     runas_slice_user(username);
 559
 560     /* With the uid/gid appropriately set. Let's figure out what the
 561      * shell in the vserver's /etc/passwd is for the given username.
 562      */
 563     if ((pwd = getpwnam(username)) == NULL) {
 564         fprintf(stderr,"vsh: getpwnam error failed for %s\n",username);
 565         exit(1);
 566     }
 567
 568     /* Make sure pw->pw_shell is non-NULL.*/
 569     if (pwd->pw_shell == NULL || pwd->pw_shell[0] == '\0') {
 570       pwd->pw_shell = (char *) DEFAULT_SHELL;
 571     }
 572
 573     shell = (char *)strdup(pwd->pw_shell);
 574     if (!shell) {
 575       perror("vsh: strdup failed");
 576       exit(2);
 577     }
 578
 579     /* Check whether 'su' or 'sshd' invoked us as a login shell or
 580        not; did this above when testing argv[0]=='-'.
 581     */
 582     argv[0] = shell;
 583     if (index == 1) {
 584       char **args;
 585       args = (char**)malloc(sizeof(char*)*(argc+2));
 586       if (!args) {
 587         perror("vsh: malloc failed");
 588       }
 589       args[0] = argv[0];
 590       args[1] = "-l";
 591       for(i=1;i<argc+1;i++) {
 592         args[i+1] = argv[i];
 593       }
 594       argv = args;
 595     }
 596     (void) execvp(shell,argv);
 597     {
 598       int exit_status = (errno == ENOENT ? EXIT_ENOENT : EXIT_CANNOT_INVOKE);
 599       exit (exit_status);
 600     }
 601
 602     return 0; /* shutup compiler */
 603 }