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 2 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, write to the Free Software
  18    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  19 */
  20
  21 #include "includes.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         pstring path;
  34
  35         slprintf(path, sizeof(path)-1, "%s/smb.XXXXXX", tmpdir());
  36
  37         /* now create the file */
  38         fd = smb_mkstemp(path);
  39
  40         if (fd == -1) {
  41                 DEBUG(0,("setup_out_fd: Failed to create file %s. (%s)\n",
  42                         path, strerror(errno) ));
  43                 return -1;
  44         }
  45
  46         DEBUG(10,("setup_out_fd: Created tmp file %s\n", path ));
  47
  48         /* Ensure file only kept around by open fd. */
  49         unlink(path);
  50         return fd;
  51 }
  52
  53 /****************************************************************************
  54 run a command being careful about uid/gid handling and putting the output in
  55 outfd (or discard it if outfd is NULL).
  56 ****************************************************************************/
  57
  58 int smbrun(const char *cmd, int *outfd)
  59 {
  60         pid_t pid;
  61         uid_t uid = current_user.ut.uid;
  62         gid_t gid = current_user.ut.gid;
  63
  64         /*
  65          * Lose any elevated privileges.
  66          */
  67         drop_effective_capability(KERNEL_OPLOCK_CAPABILITY);
  68         drop_effective_capability(DMAPI_ACCESS_CAPABILITY);
  69
  70         /* point our stdout at the file we want output to go into */
  71
  72         if (outfd && ((*outfd = setup_out_fd()) == -1)) {
  73                 return -1;
  74         }
  75
  76         /* in this method we will exec /bin/sh with the correct
  77            arguments, after first setting stdout to point at the file */
  78
  79         /*
  80          * We need to temporarily stop CatchChild from eating
  81          * SIGCLD signals as it also eats the exit status code. JRA.
  82          */
  83
  84         CatchChildLeaveStatus();
  85
  86         if ((pid=sys_fork()) < 0) {
  87                 DEBUG(0,("smbrun: fork failed with error %s\n", strerror(errno) ));
  88                 CatchChild();
  89                 if (outfd) {
  90                         close(*outfd);
  91                         *outfd = -1;
  92                 }
  93                 return errno;
  94         }
  95
  96         if (pid) {
  97                 /*
  98                  * Parent.
  99                  */
 100                 int status=0;
 101                 pid_t wpid;
 102
 103
 104                 /* the parent just waits for the child to exit */
 105                 while((wpid = sys_waitpid(pid,&status,0)) < 0) {
 106                         if(errno == EINTR) {
 107                                 errno = 0;
 108                                 continue;
 109                         }
 110                         break;
 111                 }
 112
 113                 CatchChild();
 114
 115                 if (wpid != pid) {
 116                         DEBUG(2,("waitpid(%d) : %s\n",(int)pid,strerror(errno)));
 117                         if (outfd) {
 118                                 close(*outfd);
 119                                 *outfd = -1;
 120                         }
 121                         return -1;
 122                 }
 123
 124                 /* Reset the seek pointer. */
 125                 if (outfd) {
 126                         sys_lseek(*outfd, 0, SEEK_SET);
 127                 }
 128
 129 #if defined(WIFEXITED) && defined(WEXITSTATUS)
 130                 if (WIFEXITED(status)) {
 131                         return WEXITSTATUS(status);
 132                 }
 133 #endif
 134
 135                 return status;
 136         }
 137
 138         CatchChild();
 139
 140         /* we are in the child. we exec /bin/sh to do the work for us. we
 141            don't directly exec the command we want because it may be a
 142            pipeline or anything else the config file specifies */
 143
 144         /* point our stdout at the file we want output to go into */
 145         if (outfd) {
 146                 close(1);
 147                 if (sys_dup2(*outfd,1) != 1) {
 148                         DEBUG(2,("Failed to create stdout file descriptor\n"));
 149                         close(*outfd);
 150                         exit(80);
 151                 }
 152         }
 153
 154         /* now completely lose our privileges. This is a fairly paranoid
 155            way of doing it, but it does work on all systems that I know of */
 156
 157         become_user_permanently(uid, gid);
 158
 159         if (getuid() != uid || geteuid() != uid ||
 160             getgid() != gid || getegid() != gid) {
 161                 /* we failed to lose our privileges - do not execute
 162                    the command */
 163                 exit(81); /* we can't print stuff at this stage,
 164                              instead use exit codes for debugging */
 165         }
 166
 167 #ifndef __INSURE__
 168         /* close all other file descriptors, leaving only 0, 1 and 2. 0 and
 169            2 point to /dev/null from the startup code */
 170         {
 171         int fd;
 172         for (fd=3;fd<256;fd++) close(fd);
 173         }
 174 #endif
 175
 176         execl("/bin/sh","sh","-c",cmd,NULL);
 177
 178         /* not reached */
 179         exit(82);
 180         return 1;
 181 }
 182
 183
 184 /****************************************************************************
 185 run a command being careful about uid/gid handling and putting the output in
 186 outfd (or discard it if outfd is NULL).
 187 sends the provided secret to the child stdin.
 188 ****************************************************************************/
 189
 190 int smbrunsecret(const char *cmd, const char *secret)
 191 {
 192         pid_t pid;
 193         uid_t uid = current_user.ut.uid;
 194         gid_t gid = current_user.ut.gid;
 195         int ifd[2];
 196
 197         /*
 198          * Lose any elevated privileges.
 199          */
 200         drop_effective_capability(KERNEL_OPLOCK_CAPABILITY);
 201         drop_effective_capability(DMAPI_ACCESS_CAPABILITY);
 202
 203         /* build up an input pipe */
 204         if(pipe(ifd)) {
 205                 return -1;
 206         }
 207
 208         /* in this method we will exec /bin/sh with the correct
 209            arguments, after first setting stdout to point at the file */
 210
 211         /*
 212          * We need to temporarily stop CatchChild from eating
 213          * SIGCLD signals as it also eats the exit status code. JRA.
 214          */
 215
 216         CatchChildLeaveStatus();
 217
 218         if ((pid=sys_fork()) < 0) {
 219                 DEBUG(0, ("smbrunsecret: fork failed with error %s\n", strerror(errno)));
 220                 CatchChild();
 221                 return errno;
 222         }
 223
 224         if (pid) {
 225                 /*
 226                  * Parent.
 227                  */
 228                 int status = 0;
 229                 pid_t wpid;
 230                 size_t towrite;
 231                 ssize_t wrote;
 232
 233                 close(ifd[0]);
 234                 /* send the secret */
 235                 towrite = strlen(secret);
 236                 wrote = write(ifd[1], secret, towrite);
 237                 if ( wrote != towrite ) {
 238                     DEBUG(0,("smbrunsecret: wrote %ld of %lu bytes\n",(long)wrote,(unsigned long)towrite));
 239                 }
 240                 fsync(ifd[1]);
 241                 close(ifd[1]);
 242
 243                 /* the parent just waits for the child to exit */
 244                 while((wpid = sys_waitpid(pid, &status, 0)) < 0) {
 245                         if(errno == EINTR) {
 246                                 errno = 0;
 247                                 continue;
 248                         }
 249                         break;
 250                 }
 251
 252                 CatchChild();
 253
 254                 if (wpid != pid) {
 255                         DEBUG(2, ("waitpid(%d) : %s\n", (int)pid, strerror(errno)));
 256                         return -1;
 257                 }
 258
 259 #if defined(WIFEXITED) && defined(WEXITSTATUS)
 260                 if (WIFEXITED(status)) {
 261                         return WEXITSTATUS(status);
 262                 }
 263 #endif
 264
 265                 return status;
 266         }
 267
 268         CatchChild();
 269
 270         /* we are in the child. we exec /bin/sh to do the work for us. we
 271            don't directly exec the command we want because it may be a
 272            pipeline or anything else the config file specifies */
 273
 274         close(ifd[1]);
 275         close(0);
 276         if (sys_dup2(ifd[0], 0) != 0) {
 277                 DEBUG(2,("Failed to create stdin file descriptor\n"));
 278                 close(ifd[0]);
 279                 exit(80);
 280         }
 281
 282         /* now completely lose our privileges. This is a fairly paranoid
 283            way of doing it, but it does work on all systems that I know of */
 284
 285         become_user_permanently(uid, gid);
 286
 287         if (getuid() != uid || geteuid() != uid ||
 288             getgid() != gid || getegid() != gid) {
 289                 /* we failed to lose our privileges - do not execute
 290                    the command */
 291                 exit(81); /* we can't print stuff at this stage,
 292                              instead use exit codes for debugging */
 293         }
 294
 295 #ifndef __INSURE__
 296         /* close all other file descriptors, leaving only 0, 1 and 2. 0 and
 297            2 point to /dev/null from the startup code */
 298         {
 299                 int fd;
 300                 for (fd = 3; fd < 256; fd++) close(fd);
 301         }
 302 #endif
 303
 304         execl("/bin/sh", "sh", "-c", cmd, NULL);
 305
 306         /* not reached */
 307         exit(82);
 308         return 1;
 309 }