source/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
  22 /* need to move this from here!! need some sleep ... */
  23 struct current_user current_user;
  24
  25 /****************************************************************************
  26 This is a utility function of smbrun().
  27 ****************************************************************************/
  28
  29 static int setup_out_fd(void)
  30 {
  31         int fd;
  32         TALLOC_CTX *ctx = talloc_stackframe();
  33         char *path = NULL;
  34
  35         path = talloc_asprintf(ctx,
  36                                 "%s/smb.XXXXXX",
  37                                 tmpdir());
  38         if (!path) {
  39                 TALLOC_FREE(ctx);
  40                 errno = ENOMEM;
  41                 return -1;
  42         }
  43
  44         /* now create the file */
  45         fd = smb_mkstemp(path);
  46
  47         if (fd == -1) {
  48                 DEBUG(0,("setup_out_fd: Failed to create file %s. (%s)\n",
  49                         path, strerror(errno) ));
  50                 TALLOC_FREE(ctx);
  51                 return -1;
  52         }
  53
  54         DEBUG(10,("setup_out_fd: Created tmp file %s\n", path ));
  55
  56         /* Ensure file only kept around by open fd. */
  57         unlink(path);
  58         TALLOC_FREE(ctx);
  59         return fd;
  60 }
  61
  62 /****************************************************************************
  63 run a command being careful about uid/gid handling and putting the output in
  64 outfd (or discard it if outfd is NULL).
  65 ****************************************************************************/
  66
  67 static int smbrun_internal(const char *cmd, int *outfd, bool sanitize)
  68 {
  69         pid_t pid;
  70         uid_t uid = current_user.ut.uid;
  71         gid_t gid = current_user.ut.gid;
  72
  73         /*
  74          * Lose any elevated privileges.
  75          */
  76         drop_effective_capability(KERNEL_OPLOCK_CAPABILITY);
  77         drop_effective_capability(DMAPI_ACCESS_CAPABILITY);
  78
  79         /* point our stdout at the file we want output to go into */
  80
  81         if (outfd && ((*outfd = setup_out_fd()) == -1)) {
  82                 return -1;
  83         }
  84
  85         /* in this method we will exec /bin/sh with the correct
  86            arguments, after first setting stdout to point at the file */
  87
  88         /*
  89          * We need to temporarily stop CatchChild from eating
  90          * SIGCLD signals as it also eats the exit status code. JRA.
  91          */
  92
  93         CatchChildLeaveStatus();
  94
  95         if ((pid=sys_fork()) < 0) {
  96                 DEBUG(0,("smbrun: fork failed with error %s\n", strerror(errno) ));
  97                 CatchChild();
  98                 if (outfd) {
  99                         close(*outfd);
 100                         *outfd = -1;
 101                 }
 102                 return errno;
 103         }
 104
 105         if (pid) {
 106                 /*
 107                  * Parent.
 108                  */
 109                 int status=0;
 110                 pid_t wpid;
 111
 112
 113                 /* the parent just waits for the child to exit */
 114                 while((wpid = sys_waitpid(pid,&status,0)) < 0) {
 115                         if(errno == EINTR) {
 116                                 errno = 0;
 117                                 continue;
 118                         }
 119                         break;
 120                 }
 121
 122                 CatchChild();
 123
 124                 if (wpid != pid) {
 125                         DEBUG(2,("waitpid(%d) : %s\n",(int)pid,strerror(errno)));
 126                         if (outfd) {
 127                                 close(*outfd);
 128                                 *outfd = -1;
 129                         }
 130                         return -1;
 131                 }
 132
 133                 /* Reset the seek pointer. */
 134                 if (outfd) {
 135                         sys_lseek(*outfd, 0, SEEK_SET);
 136                 }
 137
 138 #if defined(WIFEXITED) && defined(WEXITSTATUS)
 139                 if (WIFEXITED(status)) {
 140                         return WEXITSTATUS(status);
 141                 }
 142 #endif
 143
 144                 return status;
 145         }
 146
 147         CatchChild();
 148
 149         /* we are in the child. we exec /bin/sh to do the work for us. we
 150            don't directly exec the command we want because it may be a
 151            pipeline or anything else the config file specifies */
 152
 153         /* point our stdout at the file we want output to go into */
 154         if (outfd) {
 155                 close(1);
 156                 if (sys_dup2(*outfd,1) != 1) {
 157                         DEBUG(2,("Failed to create stdout file descriptor\n"));
 158                         close(*outfd);
 159                         exit(80);
 160                 }
 161         }
 162
 163         /* now completely lose our privileges. This is a fairly paranoid
 164            way of doing it, but it does work on all systems that I know of */
 165
 166         become_user_permanently(uid, gid);
 167
 168         if (getuid() != uid || geteuid() != uid ||
 169             getgid() != gid || getegid() != gid) {
 170                 /* we failed to lose our privileges - do not execute
 171                    the command */
 172                 exit(81); /* we can't print stuff at this stage,
 173                              instead use exit codes for debugging */
 174         }
 175
 176 #ifndef __INSURE__
 177         /* close all other file descriptors, leaving only 0, 1 and 2. 0 and
 178            2 point to /dev/null from the startup code */
 179         {
 180         int fd;
 181         for (fd=3;fd<256;fd++) close(fd);
 182         }
 183 #endif
 184
 185         {
 186                 const char *newcmd = sanitize ? escape_shell_string(cmd) : cmd;
 187                 if (!newcmd) {
 188                         exit(82);
 189                 }
 190                 execl("/bin/sh","sh","-c",newcmd,NULL);
 191         }
 192
 193         /* not reached */
 194         exit(83);
 195         return 1;
 196 }
 197
 198 /****************************************************************************
 199  Use only in known safe shell calls (printing).
 200 ****************************************************************************/
 201
 202 int smbrun_no_sanitize(const char *cmd, int *outfd)
 203 {
 204         return smbrun_internal(cmd, outfd, False);
 205 }
 206
 207 /****************************************************************************
 208  By default this now sanitizes shell expansion.
 209 ****************************************************************************/
 210
 211 int smbrun(const char *cmd, int *outfd)
 212 {
 213         return smbrun_internal(cmd, outfd, True);
 214 }
 215
 216 /****************************************************************************
 217 run a command being careful about uid/gid handling and putting the output in
 218 outfd (or discard it if outfd is NULL).
 219 sends the provided secret to the child stdin.
 220 ****************************************************************************/
 221
 222 int smbrunsecret(const char *cmd, const char *secret)
 223 {
 224         pid_t pid;
 225         uid_t uid = current_user.ut.uid;
 226         gid_t gid = current_user.ut.gid;
 227         int ifd[2];
 228
 229         /*
 230          * Lose any elevated privileges.
 231          */
 232         drop_effective_capability(KERNEL_OPLOCK_CAPABILITY);
 233         drop_effective_capability(DMAPI_ACCESS_CAPABILITY);
 234
 235         /* build up an input pipe */
 236         if(pipe(ifd)) {
 237                 return -1;
 238         }
 239
 240         /* in this method we will exec /bin/sh with the correct
 241            arguments, after first setting stdout to point at the file */
 242
 243         /*
 244          * We need to temporarily stop CatchChild from eating
 245          * SIGCLD signals as it also eats the exit status code. JRA.
 246          */
 247
 248         CatchChildLeaveStatus();
 249
 250         if ((pid=sys_fork()) < 0) {
 251                 DEBUG(0, ("smbrunsecret: fork failed with error %s\n", strerror(errno)));
 252                 CatchChild();
 253                 return errno;
 254         }
 255
 256         if (pid) {
 257                 /*
 258                  * Parent.
 259                  */
 260                 int status = 0;
 261                 pid_t wpid;
 262                 size_t towrite;
 263                 ssize_t wrote;
 264
 265                 close(ifd[0]);
 266                 /* send the secret */
 267                 towrite = strlen(secret);
 268                 wrote = write(ifd[1], secret, towrite);
 269                 if ( wrote != towrite ) {
 270                     DEBUG(0,("smbrunsecret: wrote %ld of %lu bytes\n",(long)wrote,(unsigned long)towrite));
 271                 }
 272                 fsync(ifd[1]);
 273                 close(ifd[1]);
 274
 275                 /* the parent just waits for the child to exit */
 276                 while((wpid = sys_waitpid(pid, &status, 0)) < 0) {
 277                         if(errno == EINTR) {
 278                                 errno = 0;
 279                                 continue;
 280                         }
 281                         break;
 282                 }
 283
 284                 CatchChild();
 285
 286                 if (wpid != pid) {
 287                         DEBUG(2, ("waitpid(%d) : %s\n", (int)pid, strerror(errno)));
 288                         return -1;
 289                 }
 290
 291 #if defined(WIFEXITED) && defined(WEXITSTATUS)
 292                 if (WIFEXITED(status)) {
 293                         return WEXITSTATUS(status);
 294                 }
 295 #endif
 296
 297                 return status;
 298         }
 299
 300         CatchChild();
 301
 302         /* we are in the child. we exec /bin/sh to do the work for us. we
 303            don't directly exec the command we want because it may be a
 304            pipeline or anything else the config file specifies */
 305
 306         close(ifd[1]);
 307         close(0);
 308         if (sys_dup2(ifd[0], 0) != 0) {
 309                 DEBUG(2,("Failed to create stdin file descriptor\n"));
 310                 close(ifd[0]);
 311                 exit(80);
 312         }
 313
 314         /* now completely lose our privileges. This is a fairly paranoid
 315            way of doing it, but it does work on all systems that I know of */
 316
 317         become_user_permanently(uid, gid);
 318
 319         if (getuid() != uid || geteuid() != uid ||
 320             getgid() != gid || getegid() != gid) {
 321                 /* we failed to lose our privileges - do not execute
 322                    the command */
 323                 exit(81); /* we can't print stuff at this stage,
 324                              instead use exit codes for debugging */
 325         }
 326
 327 #ifndef __INSURE__
 328         /* close all other file descriptors, leaving only 0, 1 and 2. 0 and
 329            2 point to /dev/null from the startup code */
 330         {
 331                 int fd;
 332                 for (fd = 3; fd < 256; fd++) close(fd);
 333         }
 334 #endif
 335
 336         execl("/bin/sh", "sh", "-c", cmd, NULL);
 337
 338         /* not reached */
 339         exit(82);
 340         return 1;
 341 }