source3/lib/smbrun.c

   1 /*
   2    Unix SMB/CIFS implementation.
   3    run a command as a specified user
   4    Copyright (C) Andrew Tridgell 1992-1998
   5
   6    This program is free software; you can redistribute it and/or modify
   7    it under the terms of the GNU General Public License as published by
   8    the Free Software Foundation; either version 3 of the License, or
   9    (at your option) any later version.
  10
  11    This program is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14    GNU General Public License for more details.
  15
  16    You should have received a copy of the GNU General Public License
  17    along with this program.  If not, see <http://www.gnu.org/licenses/>.
  18 */
  19
  20 #include "includes.h"
  21 #include "system/filesys.h"
  22
  23 /* need to move this from here!! need some sleep ... */
  24 struct current_user current_user;
  25
  26 /****************************************************************************
  27 This is a utility function of smbrun().
  28 ****************************************************************************/
  29
  30 static int setup_out_fd(void)
  31 {
  32         int fd;
  33         TALLOC_CTX *ctx = talloc_stackframe();
  34         char *path = NULL;
  35         mode_t mask;
  36
  37         path = talloc_asprintf(ctx,
  38                                 "%s/smb.XXXXXX",
  39                                 tmpdir());
  40         if (!path) {
  41                 TALLOC_FREE(ctx);
  42                 errno = ENOMEM;
  43                 return -1;
  44         }
  45
  46         /* now create the file */
  47         mask = umask(S_IRWXO | S_IRWXG);
  48         fd = mkstemp(path);
  49         umask(mask);
  50
  51         if (fd == -1) {
  52                 DEBUG(0,("setup_out_fd: Failed to create file %s. (%s)\n",
  53                         path, strerror(errno) ));
  54                 TALLOC_FREE(ctx);
  55                 return -1;
  56         }
  57
  58         DEBUG(10,("setup_out_fd: Created tmp file %s\n", path ));
  59
  60         /* Ensure file only kept around by open fd. */
  61         unlink(path);
  62         TALLOC_FREE(ctx);
  63         return fd;
  64 }
  65
  66 /****************************************************************************
  67 run a command being careful about uid/gid handling and putting the output in
  68 outfd (or discard it if outfd is NULL).
  69 ****************************************************************************/
  70
  71 static int smbrun_internal(const char *cmd, int *outfd, bool sanitize)
  72 {
  73         pid_t pid;
  74         uid_t uid = current_user.ut.uid;
  75         gid_t gid = current_user.ut.gid;
  76         void (*saved_handler)(int);
  77
  78         /*
  79          * Lose any elevated privileges.
  80          */
  81         drop_effective_capability(KERNEL_OPLOCK_CAPABILITY);
  82         drop_effective_capability(DMAPI_ACCESS_CAPABILITY);
  83
  84         /* point our stdout at the file we want output to go into */
  85
  86         if (outfd && ((*outfd = setup_out_fd()) == -1)) {
  87                 return -1;
  88         }
  89
  90         /* in this method we will exec /bin/sh with the correct
  91            arguments, after first setting stdout to point at the file */
  92
  93         /*
  94          * We need to temporarily stop CatchChild from eating
  95          * SIGCLD signals as it also eats the exit status code. JRA.
  96          */
  97
  98         saved_handler = CatchChildLeaveStatus();
  99
 100         if ((pid=fork()) < 0) {
 101                 DEBUG(0,("smbrun: fork failed with error %s\n", strerror(errno) ));
 102                 (void)CatchSignal(SIGCLD, saved_handler);
 103                 if (outfd) {
 104                         close(*outfd);
 105                         *outfd = -1;
 106                 }
 107                 return errno;
 108         }
 109
 110         if (pid) {
 111                 /*
 112                  * Parent.
 113                  */
 114                 int status=0;
 115                 pid_t wpid;
 116
 117
 118                 /* the parent just waits for the child to exit */
 119                 while((wpid = sys_waitpid(pid,&status,0)) < 0) {
 120                         if(errno == EINTR) {
 121                                 errno = 0;
 122                                 continue;
 123                         }
 124                         break;
 125                 }
 126
 127                 (void)CatchSignal(SIGCLD, saved_handler);
 128
 129                 if (wpid != pid) {
 130                         DEBUG(2,("waitpid(%d) : %s\n",(int)pid,strerror(errno)));
 131                         if (outfd) {
 132                                 close(*outfd);
 133                                 *outfd = -1;
 134                         }
 135                         return -1;
 136                 }
 137
 138                 /* Reset the seek pointer. */
 139                 if (outfd) {
 140                         lseek(*outfd, 0, SEEK_SET);
 141                 }
 142
 143 #if defined(WIFEXITED) && defined(WEXITSTATUS)
 144                 if (WIFEXITED(status)) {
 145                         return WEXITSTATUS(status);
 146                 }
 147 #endif
 148
 149                 return status;
 150         }
 151
 152         (void)CatchChild();
 153
 154         /* we are in the child. we exec /bin/sh to do the work for us. we
 155            don't directly exec the command we want because it may be a
 156            pipeline or anything else the config file specifies */
 157
 158         /* point our stdout at the file we want output to go into */
 159         if (outfd) {
 160                 close(1);
 161                 if (dup2(*outfd,1) != 1) {
 162                         DEBUG(2,("Failed to create stdout file descriptor\n"));
 163                         close(*outfd);
 164                         exit(80);
 165                 }
 166         }
 167
 168         /* now completely lose our privileges. This is a fairly paranoid
 169            way of doing it, but it does work on all systems that I know of */
 170
 171         become_user_permanently(uid, gid);
 172
 173         if (!non_root_mode()) {
 174                 if (getuid() != uid || geteuid() != uid ||
 175                     getgid() != gid || getegid() != gid) {
 176                         /* we failed to lose our privileges - do not execute
 177                            the command */
 178                         exit(81); /* we can't print stuff at this stage,
 179                                      instead use exit codes for debugging */
 180                 }
 181         }
 182
 183 #ifndef __INSURE__
 184         /* close all other file descriptors, leaving only 0, 1 and 2. 0 and
 185            2 point to /dev/null from the startup code */
 186         {
 187         int fd;
 188         for (fd=3;fd<256;fd++) close(fd);
 189         }
 190 #endif
 191
 192         {
 193                 char *newcmd = NULL;
 194                 if (sanitize) {
 195                         newcmd = escape_shell_string(cmd);
 196                         if (!newcmd)
 197                                 exit(82);
 198                 }
 199
 200                 execl("/bin/sh","sh","-c",
 201                     newcmd ? (const char *)newcmd : cmd, NULL);
 202
 203                 SAFE_FREE(newcmd);
 204         }
 205
 206         /* not reached */
 207         exit(83);
 208         return 1;
 209 }
 210
 211 /****************************************************************************
 212  Use only in known safe shell calls (printing).
 213 ****************************************************************************/
 214
 215 int smbrun_no_sanitize(const char *cmd, int *outfd)
 216 {
 217         return smbrun_internal(cmd, outfd, False);
 218 }
 219
 220 /****************************************************************************
 221  By default this now sanitizes shell expansion.
 222 ****************************************************************************/
 223
 224 int smbrun(const char *cmd, int *outfd)
 225 {
 226         return smbrun_internal(cmd, outfd, True);
 227 }
 228
 229 /****************************************************************************
 230 run a command being careful about uid/gid handling and putting the output in
 231 outfd (or discard it if outfd is NULL).
 232 sends the provided secret to the child stdin.
 233 ****************************************************************************/
 234
 235 int smbrunsecret(const char *cmd, const char *secret)
 236 {
 237         pid_t pid;
 238         uid_t uid = current_user.ut.uid;
 239         gid_t gid = current_user.ut.gid;
 240         int ifd[2];
 241         void (*saved_handler)(int);
 242
 243         /*
 244          * Lose any elevated privileges.
 245          */
 246         drop_effective_capability(KERNEL_OPLOCK_CAPABILITY);
 247         drop_effective_capability(DMAPI_ACCESS_CAPABILITY);
 248
 249         /* build up an input pipe */
 250         if(pipe(ifd)) {
 251                 return -1;
 252         }
 253
 254         /* in this method we will exec /bin/sh with the correct
 255            arguments, after first setting stdout to point at the file */
 256
 257         /*
 258          * We need to temporarily stop CatchChild from eating
 259          * SIGCLD signals as it also eats the exit status code. JRA.
 260          */
 261
 262         saved_handler = CatchChildLeaveStatus();
 263
 264         if ((pid=fork()) < 0) {
 265                 DEBUG(0, ("smbrunsecret: fork failed with error %s\n", strerror(errno)));
 266                 (void)CatchSignal(SIGCLD, saved_handler);
 267                 return errno;
 268         }
 269
 270         if (pid) {
 271                 /*
 272                  * Parent.
 273                  */
 274                 int status = 0;
 275                 pid_t wpid;
 276                 size_t towrite;
 277                 ssize_t wrote;
 278
 279                 close(ifd[0]);
 280                 /* send the secret */
 281                 towrite = strlen(secret);
 282                 wrote = write(ifd[1], secret, towrite);
 283                 if ( wrote != towrite ) {
 284                     DEBUG(0,("smbrunsecret: wrote %ld of %lu bytes\n",(long)wrote,(unsigned long)towrite));
 285                 }
 286                 fsync(ifd[1]);
 287                 close(ifd[1]);
 288
 289                 /* the parent just waits for the child to exit */
 290                 while((wpid = sys_waitpid(pid, &status, 0)) < 0) {
 291                         if(errno == EINTR) {
 292                                 errno = 0;
 293                                 continue;
 294                         }
 295                         break;
 296                 }
 297
 298                 (void)CatchSignal(SIGCLD, saved_handler);
 299
 300                 if (wpid != pid) {
 301                         DEBUG(2, ("waitpid(%d) : %s\n", (int)pid, strerror(errno)));
 302                         return -1;
 303                 }
 304
 305 #if defined(WIFEXITED) && defined(WEXITSTATUS)
 306                 if (WIFEXITED(status)) {
 307                         return WEXITSTATUS(status);
 308                 }
 309 #endif
 310
 311                 return status;
 312         }
 313
 314         (void)CatchChild();
 315
 316         /* we are in the child. we exec /bin/sh to do the work for us. we
 317            don't directly exec the command we want because it may be a
 318            pipeline or anything else the config file specifies */
 319
 320         close(ifd[1]);
 321         close(0);
 322         if (dup2(ifd[0], 0) != 0) {
 323                 DEBUG(2,("Failed to create stdin file descriptor\n"));
 324                 close(ifd[0]);
 325                 exit(80);
 326         }
 327
 328         /* now completely lose our privileges. This is a fairly paranoid
 329            way of doing it, but it does work on all systems that I know of */
 330
 331         become_user_permanently(uid, gid);
 332
 333         if (!non_root_mode()) {
 334                 if (getuid() != uid || geteuid() != uid ||
 335                     getgid() != gid || getegid() != gid) {
 336                         /* we failed to lose our privileges - do not execute
 337                            the command */
 338                         exit(81); /* we can't print stuff at this stage,
 339                                      instead use exit codes for debugging */
 340                 }
 341         }
 342
 343 #ifndef __INSURE__
 344         /* close all other file descriptors, leaving only 0, 1 and 2. 0 and
 345            2 point to /dev/null from the startup code */
 346         {
 347                 int fd;
 348                 for (fd = 3; fd < 256; fd++) close(fd);
 349         }
 350 #endif
 351
 352         execl("/bin/sh", "sh", "-c", cmd, NULL);
 353
 354         /* not reached */
 355         exit(82);
 356         return 1;
 357 }