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         char * const *env)
  73 {
  74         pid_t pid;
  75         uid_t uid = current_user.ut.uid;
  76         gid_t gid = current_user.ut.gid;
  77         void (*saved_handler)(int);
  78
  79         /*
  80          * Lose any elevated privileges.
  81          */
  82         drop_effective_capability(KERNEL_OPLOCK_CAPABILITY);
  83         drop_effective_capability(DMAPI_ACCESS_CAPABILITY);
  84
  85         /* point our stdout at the file we want output to go into */
  86
  87         if (outfd && ((*outfd = setup_out_fd()) == -1)) {
  88                 return -1;
  89         }
  90
  91         /* in this method we will exec /bin/sh with the correct
  92            arguments, after first setting stdout to point at the file */
  93
  94         /*
  95          * We need to temporarily stop CatchChild from eating
  96          * SIGCLD signals as it also eats the exit status code. JRA.
  97          */
  98
  99         saved_handler = CatchChildLeaveStatus();
 100
 101         if ((pid=fork()) < 0) {
 102                 DEBUG(0,("smbrun: fork failed with error %s\n", strerror(errno) ));
 103                 (void)CatchSignal(SIGCLD, saved_handler);
 104                 if (outfd) {
 105                         close(*outfd);
 106                         *outfd = -1;
 107                 }
 108                 return errno;
 109         }
 110
 111         if (pid) {
 112                 /*
 113                  * Parent.
 114                  */
 115                 int status=0;
 116                 pid_t wpid;
 117
 118
 119                 /* the parent just waits for the child to exit */
 120                 while((wpid = waitpid(pid,&status,0)) < 0) {
 121                         if(errno == EINTR) {
 122                                 errno = 0;
 123                                 continue;
 124                         }
 125                         break;
 126                 }
 127
 128                 (void)CatchSignal(SIGCLD, saved_handler);
 129
 130                 if (wpid != pid) {
 131                         DEBUG(2,("waitpid(%d) : %s\n",(int)pid,strerror(errno)));
 132                         if (outfd) {
 133                                 close(*outfd);
 134                                 *outfd = -1;
 135                         }
 136                         return -1;
 137                 }
 138
 139                 /* Reset the seek pointer. */
 140                 if (outfd) {
 141                         lseek(*outfd, 0, SEEK_SET);
 142                 }
 143
 144 #if defined(WIFEXITED) && defined(WEXITSTATUS)
 145                 if (WIFEXITED(status)) {
 146                         return WEXITSTATUS(status);
 147                 }
 148 #endif
 149
 150                 return status;
 151         }
 152
 153         (void)CatchChild();
 154
 155         /* we are in the child. we exec /bin/sh to do the work for us. we
 156            don't directly exec the command we want because it may be a
 157            pipeline or anything else the config file specifies */
 158
 159         /* point our stdout at the file we want output to go into */
 160         if (outfd) {
 161                 close(1);
 162                 if (dup2(*outfd,1) != 1) {
 163                         DEBUG(2,("Failed to create stdout file descriptor\n"));
 164                         close(*outfd);
 165                         exit(80);
 166                 }
 167         }
 168
 169         /* now completely lose our privileges. This is a fairly paranoid
 170            way of doing it, but it does work on all systems that I know of */
 171
 172         become_user_permanently(uid, gid);
 173
 174         if (!non_root_mode()) {
 175                 if (getuid() != uid || geteuid() != uid ||
 176                     getgid() != gid || getegid() != gid) {
 177                         /* we failed to lose our privileges - do not execute
 178                            the command */
 179                         exit(81); /* we can't print stuff at this stage,
 180                                      instead use exit codes for debugging */
 181                 }
 182         }
 183
 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         closefrom(3);
 187
 188         {
 189                 char *newcmd = NULL;
 190                 if (sanitize) {
 191                         newcmd = escape_shell_string(cmd);
 192                         if (!newcmd)
 193                                 exit(82);
 194                 }
 195
 196                 if (env != NULL) {
 197                         execle("/bin/sh","sh","-c",
 198                                 newcmd ? (const char *)newcmd : cmd, NULL,
 199                                 env);
 200                 } else {
 201                         execl("/bin/sh","sh","-c",
 202                                 newcmd ? (const char *)newcmd : cmd, NULL);
 203                 }
 204
 205                 SAFE_FREE(newcmd);
 206         }
 207
 208         /* not reached */
 209         exit(83);
 210         return 1;
 211 }
 212
 213 /****************************************************************************
 214  Use only in known safe shell calls (printing).
 215 ****************************************************************************/
 216
 217 int smbrun_no_sanitize(const char *cmd, int *outfd, char * const *env)
 218 {
 219         return smbrun_internal(cmd, outfd, false, env);
 220 }
 221
 222 /****************************************************************************
 223  By default this now sanitizes shell expansion.
 224 ****************************************************************************/
 225
 226 int smbrun(const char *cmd, int *outfd, char * const *env)
 227 {
 228         return smbrun_internal(cmd, outfd, true, env);
 229 }
 230
 231 /****************************************************************************
 232 run a command being careful about uid/gid handling and putting the output in
 233 outfd (or discard it if outfd is NULL).
 234 sends the provided secret to the child stdin.
 235 ****************************************************************************/
 236
 237 int smbrunsecret(const char *cmd, const char *secret)
 238 {
 239         pid_t pid;
 240         uid_t uid = current_user.ut.uid;
 241         gid_t gid = current_user.ut.gid;
 242         int ifd[2];
 243         void (*saved_handler)(int);
 244
 245         /*
 246          * Lose any elevated privileges.
 247          */
 248         drop_effective_capability(KERNEL_OPLOCK_CAPABILITY);
 249         drop_effective_capability(DMAPI_ACCESS_CAPABILITY);
 250
 251         /* build up an input pipe */
 252         if(pipe(ifd)) {
 253                 return -1;
 254         }
 255
 256         /* in this method we will exec /bin/sh with the correct
 257            arguments, after first setting stdout to point at the file */
 258
 259         /*
 260          * We need to temporarily stop CatchChild from eating
 261          * SIGCLD signals as it also eats the exit status code. JRA.
 262          */
 263
 264         saved_handler = CatchChildLeaveStatus();
 265
 266         if ((pid=fork()) < 0) {
 267                 DEBUG(0, ("smbrunsecret: fork failed with error %s\n", strerror(errno)));
 268                 (void)CatchSignal(SIGCLD, saved_handler);
 269                 return errno;
 270         }
 271
 272         if (pid) {
 273                 /*
 274                  * Parent.
 275                  */
 276                 int status = 0;
 277                 pid_t wpid;
 278                 size_t towrite;
 279                 ssize_t wrote;
 280
 281                 close(ifd[0]);
 282                 /* send the secret */
 283                 towrite = strlen(secret);
 284                 wrote = write(ifd[1], secret, towrite);
 285                 if ( wrote != towrite ) {
 286                     DEBUG(0,("smbrunsecret: wrote %ld of %lu bytes\n",(long)wrote,(unsigned long)towrite));
 287                 }
 288                 fsync(ifd[1]);
 289                 close(ifd[1]);
 290
 291                 /* the parent just waits for the child to exit */
 292                 while((wpid = waitpid(pid, &status, 0)) < 0) {
 293                         if(errno == EINTR) {
 294                                 errno = 0;
 295                                 continue;
 296                         }
 297                         break;
 298                 }
 299
 300                 (void)CatchSignal(SIGCLD, saved_handler);
 301
 302                 if (wpid != pid) {
 303                         DEBUG(2, ("waitpid(%d) : %s\n", (int)pid, strerror(errno)));
 304                         return -1;
 305                 }
 306
 307 #if defined(WIFEXITED) && defined(WEXITSTATUS)
 308                 if (WIFEXITED(status)) {
 309                         return WEXITSTATUS(status);
 310                 }
 311 #endif
 312
 313                 return status;
 314         }
 315
 316         (void)CatchChild();
 317
 318         /* we are in the child. we exec /bin/sh to do the work for us. we
 319            don't directly exec the command we want because it may be a
 320            pipeline or anything else the config file specifies */
 321
 322         close(ifd[1]);
 323         close(0);
 324         if (dup2(ifd[0], 0) != 0) {
 325                 DEBUG(2,("Failed to create stdin file descriptor\n"));
 326                 close(ifd[0]);
 327                 exit(80);
 328         }
 329
 330         /* now completely lose our privileges. This is a fairly paranoid
 331            way of doing it, but it does work on all systems that I know of */
 332
 333         become_user_permanently(uid, gid);
 334
 335         if (!non_root_mode()) {
 336                 if (getuid() != uid || geteuid() != uid ||
 337                     getgid() != gid || getegid() != gid) {
 338                         /* we failed to lose our privileges - do not execute
 339                            the command */
 340                         exit(81); /* we can't print stuff at this stage,
 341                                      instead use exit codes for debugging */
 342                 }
 343         }
 344
 345         /* close all other file descriptors, leaving only 0, 1 and 2. 0 and
 346            2 point to /dev/null from the startup code */
 347         closefrom(3);
 348
 349         execl("/bin/sh", "sh", "-c", cmd, NULL);
 350
 351         /* not reached */
 352         exit(82);
 353         return 1;
 354 }