g10/exec.c

   1 /* exec.c - generic call-a-program code
   2  * Copyright (C) 2001, 2002, 2003, 2004, 2005 Free Software Foundation, Inc.
   3  *
   4  * This file is part of GnuPG.
   5  *
   6  * GnuPG 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  * GnuPG 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 /*
  21    FIXME: We should replace most code in this module by our
  22    spawn implementation from common/exechelp.c.
  23  */
  24
  25
  26 #include <config.h>
  27 #include <stdlib.h>
  28 #include <stdarg.h>
  29 #include <stdio.h>
  30 #include <sys/stat.h>
  31 #include <sys/types.h>
  32 #ifndef EXEC_TEMPFILE_ONLY
  33 #include <sys/wait.h>
  34 #endif
  35 #ifdef HAVE_DOSISH_SYSTEM
  36 #include <windows.h>
  37 #endif
  38 #include <fcntl.h>
  39 #include <unistd.h>
  40 #include <string.h>
  41 #include <errno.h>
  42
  43 #include "gpg.h"
  44 #include "options.h"
  45 #include "i18n.h"
  46 #include "iobuf.h"
  47 #include "util.h"
  48 #include "mkdtemp.h"  /* From gnulib. */
  49 #include "membuf.h"
  50 #include "exec.h"
  51
  52 #ifdef NO_EXEC
  53 int
  54 exec_write(struct exec_info **info,const char *program,
  55                const char *args_in,const char *name,int writeonly,int binary)
  56 {
  57   log_error(_("no remote program execution supported\n"));
  58   return G10ERR_GENERAL;
  59 }
  60
  61 int
  62 exec_read(struct exec_info *info) { return G10ERR_GENERAL; }
  63 int
  64 exec_finish(struct exec_info *info) { return G10ERR_GENERAL; }
  65 int
  66 set_exec_path(const char *path) { return G10ERR_GENERAL; }
  67
  68 #else /* ! NO_EXEC */
  69
  70 #if defined (_WIN32)
  71 /* This is a nicer system() for windows that waits for programs to
  72    return before returning control to the caller.  I hate helpful
  73    computers. */
  74 static int
  75 w32_system(const char *command)
  76 {
  77   PROCESS_INFORMATION pi;
  78   STARTUPINFO si;
  79   char *string;
  80
  81   /* We must use a copy of the command as CreateProcess modifies this
  82      argument. */
  83   string=xstrdup(command);
  84
  85   memset(&pi,0,sizeof(pi));
  86   memset(&si,0,sizeof(si));
  87   si.cb=sizeof(si);
  88
  89   if(!CreateProcess(NULL,string,NULL,NULL,FALSE,
  90                     DETACHED_PROCESS,
  91                     NULL,NULL,&si,&pi))
  92     return -1;
  93
  94   /* Wait for the child to exit */
  95   WaitForSingleObject(pi.hProcess,INFINITE);
  96
  97   CloseHandle(pi.hProcess);
  98   CloseHandle(pi.hThread);
  99   xfree(string);
 100
 101   return 0;
 102 }
 103 #endif
 104
 105 /* Replaces current $PATH */
 106 int
 107 set_exec_path(const char *path)
 108 {
 109   char *p;
 110
 111   p=xmalloc(5+strlen(path)+1);
 112   strcpy(p,"PATH=");
 113   strcat(p,path);
 114
 115   if(DBG_EXTPROG)
 116     log_debug("set_exec_path: %s\n",p);
 117
 118   /* Notice that path is never freed.  That is intentional due to the
 119      way putenv() works.  This leaks a few bytes if we call
 120      set_exec_path multiple times. */
 121
 122   if(putenv(p)!=0)
 123     return G10ERR_GENERAL;
 124   else
 125     return 0;
 126 }
 127
 128 /* Makes a temp directory and filenames */
 129 static int
 130 make_tempdir(struct exec_info *info)
 131 {
 132   char *tmp=opt.temp_dir,*namein=info->name,*nameout;
 133
 134   if(!namein)
 135     namein=info->flags.binary?"tempin" EXTSEP_S "bin":"tempin" EXTSEP_S "txt";
 136
 137   nameout=info->flags.binary?"tempout" EXTSEP_S "bin":"tempout" EXTSEP_S "txt";
 138
 139   /* Make up the temp dir and files in case we need them */
 140
 141   if(tmp==NULL)
 142     {
 143 #if defined (_WIN32)
 144       int err;
 145
 146       tmp=xmalloc(MAX_PATH+2);
 147       err=GetTempPath(MAX_PATH+1,tmp);
 148       if(err==0 || err>MAX_PATH+1)
 149         strcpy(tmp,"c:\\windows\\temp");
 150       else
 151         {
 152           int len=strlen(tmp);
 153
 154           /* GetTempPath may return with \ on the end */
 155           while(len>0 && tmp[len-1]=='\\')
 156             {
 157               tmp[len-1]='\0';
 158               len--;
 159             }
 160         }
 161 #else /* More unixish systems */
 162       tmp=getenv("TMPDIR");
 163       if(tmp==NULL)
 164         {
 165           tmp=getenv("TMP");
 166           if(tmp==NULL)
 167             {
 168 #ifdef __riscos__
 169               tmp="<Wimp$ScrapDir>.GnuPG";
 170               mkdir(tmp,0700); /* Error checks occur later on */
 171 #else
 172               tmp="/tmp";
 173 #endif
 174             }
 175         }
 176 #endif
 177     }
 178
 179   info->tempdir=xmalloc(strlen(tmp)+strlen(DIRSEP_S)+10+1);
 180
 181   sprintf(info->tempdir,"%s" DIRSEP_S "gpg-XXXXXX",tmp);
 182
 183 #if defined (_WIN32)
 184   xfree(tmp);
 185 #endif
 186
 187   if(mkdtemp(info->tempdir)==NULL)
 188     log_error(_("can't create directory `%s': %s\n"),
 189               info->tempdir,strerror(errno));
 190   else
 191     {
 192       info->flags.madedir=1;
 193
 194       info->tempfile_in=xmalloc(strlen(info->tempdir)+
 195                                 strlen(DIRSEP_S)+strlen(namein)+1);
 196       sprintf(info->tempfile_in,"%s" DIRSEP_S "%s",info->tempdir,namein);
 197
 198       if(!info->flags.writeonly)
 199         {
 200           info->tempfile_out=xmalloc(strlen(info->tempdir)+
 201                                      strlen(DIRSEP_S)+strlen(nameout)+1);
 202           sprintf(info->tempfile_out,"%s" DIRSEP_S "%s",info->tempdir,nameout);
 203         }
 204     }
 205
 206   return info->flags.madedir?0:G10ERR_GENERAL;
 207 }
 208
 209 /* Expands %i and %o in the args to the full temp files within the
 210    temp directory. */
 211 static int
 212 expand_args(struct exec_info *info,const char *args_in)
 213 {
 214   const char *ch = args_in;
 215   membuf_t command;
 216
 217   info->flags.use_temp_files=0;
 218   info->flags.keep_temp_files=0;
 219
 220   if(DBG_EXTPROG)
 221     log_debug("expanding string \"%s\"\n",args_in);
 222
 223   init_membuf (&command, 100);
 224
 225   while(*ch!='\0')
 226     {
 227       if(*ch=='%')
 228         {
 229           char *append=NULL;
 230
 231           ch++;
 232
 233           switch(*ch)
 234             {
 235             case 'O':
 236               info->flags.keep_temp_files=1;
 237               /* fall through */
 238
 239             case 'o': /* out */
 240               if(!info->flags.madedir)
 241                 {
 242                   if(make_tempdir(info))
 243                     goto fail;
 244                 }
 245               append=info->tempfile_out;
 246               info->flags.use_temp_files=1;
 247               break;
 248
 249             case 'I':
 250               info->flags.keep_temp_files=1;
 251               /* fall through */
 252
 253             case 'i': /* in */
 254               if(!info->flags.madedir)
 255                 {
 256                   if(make_tempdir(info))
 257                     goto fail;
 258                 }
 259               append=info->tempfile_in;
 260               info->flags.use_temp_files=1;
 261               break;
 262
 263             case '%':
 264               append="%";
 265               break;
 266             }
 267
 268           if(append)
 269             put_membuf_str (&command, append);
 270         }
 271       else
 272         put_membuf (&command, ch, 1);
 273
 274       ch++;
 275     }
 276
 277   put_membuf (&command, "", 1);  /* Terminate string.  */
 278
 279   info->command = get_membuf (&command, NULL);
 280   if (!info->command)
 281     return gpg_error_from_syserror ();
 282
 283   if(DBG_EXTPROG)
 284     log_debug("args expanded to \"%s\", use %u, keep %u\n",info->command,
 285               info->flags.use_temp_files,info->flags.keep_temp_files);
 286
 287   return 0;
 288
 289  fail:
 290   xfree (get_membuf (&command, NULL));
 291   return G10ERR_GENERAL;
 292 }
 293
 294 /* Either handles the tempfile creation, or the fork/exec.  If it
 295    returns ok, then info->tochild is a FILE * that can be written to.
 296    The rules are: if there are no args, then it's a fork/exec/pipe.
 297    If there are args, but no tempfiles, then it's a fork/exec/pipe via
 298    shell -c.  If there are tempfiles, then it's a system. */
 299
 300 int
 301 exec_write(struct exec_info **info,const char *program,
 302            const char *args_in,const char *name,int writeonly,int binary)
 303 {
 304   int ret=G10ERR_GENERAL;
 305
 306   if(opt.exec_disable && !opt.no_perm_warn)
 307     {
 308       log_info(_("external program calls are disabled due to unsafe "
 309                  "options file permissions\n"));
 310
 311       return ret;
 312     }
 313
 314 #if defined(HAVE_GETUID) && defined(HAVE_GETEUID)
 315   /* There should be no way to get to this spot while still carrying
 316      setuid privs.  Just in case, bomb out if we are. */
 317   if ( getuid () != geteuid ())
 318     BUG ();
 319 #endif
 320
 321   if(program==NULL && args_in==NULL)
 322     BUG();
 323
 324   *info=xmalloc_clear(sizeof(struct exec_info));
 325
 326   if(name)
 327     (*info)->name=xstrdup(name);
 328   (*info)->flags.binary=binary;
 329   (*info)->flags.writeonly=writeonly;
 330
 331   /* Expand the args, if any */
 332   if(args_in && expand_args(*info,args_in))
 333     goto fail;
 334
 335 #ifdef EXEC_TEMPFILE_ONLY
 336   if(!(*info)->flags.use_temp_files)
 337     {
 338       log_error(_("this platform requires temporary files when calling"
 339                   " external programs\n"));
 340       goto fail;
 341     }
 342
 343 #else /* !EXEC_TEMPFILE_ONLY */
 344
 345   /* If there are no args, or there are args, but no temp files, we
 346      can use fork/exec/pipe */
 347   if(args_in==NULL || (*info)->flags.use_temp_files==0)
 348     {
 349       int to[2],from[2];
 350
 351       if(pipe(to)==-1)
 352         goto fail;
 353
 354       if(pipe(from)==-1)
 355         {
 356           close(to[0]);
 357           close(to[1]);
 358           goto fail;
 359         }
 360
 361       if(((*info)->child=fork())==-1)
 362         {
 363           close(to[0]);
 364           close(to[1]);
 365           close(from[0]);
 366           close(from[1]);
 367           goto fail;
 368         }
 369
 370       if((*info)->child==0)
 371         {
 372           char *shell=getenv("SHELL");
 373
 374           if(shell==NULL)
 375             shell="/bin/sh";
 376
 377           /* I'm the child */
 378
 379           /* If the program isn't going to respond back, they get to
 380              keep their stdout/stderr */
 381           if(!(*info)->flags.writeonly)
 382             {
 383               /* implied close of STDERR */
 384               if(dup2(STDOUT_FILENO,STDERR_FILENO)==-1)
 385                 _exit(1);
 386
 387               /* implied close of STDOUT */
 388               close(from[0]);
 389               if(dup2(from[1],STDOUT_FILENO)==-1)
 390                 _exit(1);
 391             }
 392
 393           /* implied close of STDIN */
 394           close(to[1]);
 395           if(dup2(to[0],STDIN_FILENO)==-1)
 396             _exit(1);
 397
 398           if(args_in==NULL)
 399             {
 400               if(DBG_EXTPROG)
 401                 log_debug("execlp: %s\n",program);
 402
 403               execlp(program,program,(void *)NULL);
 404             }
 405           else
 406             {
 407               if(DBG_EXTPROG)
 408                 log_debug("execlp: %s -c %s\n",shell,(*info)->command);
 409
 410               execlp(shell,shell,"-c",(*info)->command,(void *)NULL);
 411             }
 412
 413           /* If we get this far the exec failed.  Clean up and return. */
 414
 415           if(args_in==NULL)
 416             log_error(_("unable to execute program `%s': %s\n"),
 417                       program,strerror(errno));
 418           else
 419             log_error(_("unable to execute shell `%s': %s\n"),
 420                       shell,strerror(errno));
 421
 422           /* This mimics the POSIX sh behavior - 127 means "not found"
 423              from the shell. */
 424           if(errno==ENOENT)
 425             _exit(127);
 426
 427           _exit(1);
 428         }
 429
 430       /* I'm the parent */
 431
 432       close(to[0]);
 433
 434       (*info)->tochild=fdopen(to[1],binary?"wb":"w");
 435       if((*info)->tochild==NULL)
 436         {
 437           ret = gpg_error_from_syserror ();
 438           close(to[1]);
 439           goto fail;
 440         }
 441
 442       close(from[1]);
 443
 444       (*info)->fromchild=iobuf_fdopen(from[0],"r");
 445       if((*info)->fromchild==NULL)
 446         {
 447           ret = gpg_error_from_syserror ();
 448           close(from[0]);
 449           goto fail;
 450         }
 451
 452       /* fd iobufs are cached?! */
 453       iobuf_ioctl((*info)->fromchild,3,1,NULL);
 454
 455       return 0;
 456     }
 457 #endif /* !EXEC_TEMPFILE_ONLY */
 458
 459   if(DBG_EXTPROG)
 460     log_debug("using temp file `%s'\n",(*info)->tempfile_in);
 461
 462   /* It's not fork/exec/pipe, so create a temp file */
 463   if( is_secured_filename ((*info)->tempfile_in) )
 464     {
 465       (*info)->tochild = NULL;
 466       errno = EPERM;
 467     }
 468   else
 469     (*info)->tochild=fopen((*info)->tempfile_in,binary?"wb":"w");
 470   if((*info)->tochild==NULL)
 471     {
 472       ret = gpg_error_from_syserror ();
 473       log_error(_("can't create `%s': %s\n"),
 474                 (*info)->tempfile_in,strerror(errno));
 475       goto fail;
 476     }
 477
 478   ret=0;
 479
 480  fail:
 481   if (ret)
 482     {
 483       xfree (*info);
 484       *info = NULL;
 485     }
 486   return ret;
 487 }
 488
 489 int
 490 exec_read(struct exec_info *info)
 491 {
 492   int ret=G10ERR_GENERAL;
 493
 494   fclose(info->tochild);
 495   info->tochild=NULL;
 496
 497   if(info->flags.use_temp_files)
 498     {
 499       if(DBG_EXTPROG)
 500         log_debug("system() command is %s\n",info->command);
 501
 502 #if defined (_WIN32)
 503       info->progreturn=w32_system(info->command);
 504 #else
 505       info->progreturn=system(info->command);
 506 #endif
 507
 508       if(info->progreturn==-1)
 509         {
 510           log_error(_("system error while calling external program: %s\n"),
 511                     strerror(errno));
 512           info->progreturn=127;
 513           goto fail;
 514         }
 515
 516 #if defined(WIFEXITED) && defined(WEXITSTATUS)
 517       if(WIFEXITED(info->progreturn))
 518         info->progreturn=WEXITSTATUS(info->progreturn);
 519       else
 520         {
 521           log_error(_("unnatural exit of external program\n"));
 522           info->progreturn=127;
 523           goto fail;
 524         }
 525 #else
 526       /* If we don't have the macros, do the best we can. */
 527       info->progreturn = (info->progreturn & 0xff00) >> 8;
 528 #endif
 529
 530       /* 127 is the magic value returned from system() to indicate
 531          that the shell could not be executed, or from /bin/sh to
 532          indicate that the program could not be executed. */
 533
 534       if(info->progreturn==127)
 535         {
 536           log_error(_("unable to execute external program\n"));
 537           goto fail;
 538         }
 539
 540       if(!info->flags.writeonly)
 541         {
 542           info->fromchild=iobuf_open(info->tempfile_out);
 543           if (info->fromchild
 544               && is_secured_file (iobuf_get_fd (info->fromchild)))
 545             {
 546               iobuf_close (info->fromchild);
 547               info->fromchild = NULL;
 548               errno = EPERM;
 549             }
 550           if(info->fromchild==NULL)
 551             {
 552               ret = gpg_error_from_syserror ();
 553               log_error(_("unable to read external program response: %s\n"),
 554                         strerror(errno));
 555               goto fail;
 556             }
 557
 558           /* Do not cache this iobuf on close */
 559           iobuf_ioctl(info->fromchild,3,1,NULL);
 560         }
 561     }
 562
 563   ret=0;
 564
 565  fail:
 566   return ret;
 567 }
 568
 569 int
 570 exec_finish(struct exec_info *info)
 571 {
 572   int ret=info->progreturn;
 573
 574   if(info->fromchild)
 575     iobuf_close(info->fromchild);
 576
 577   if(info->tochild)
 578     fclose(info->tochild);
 579
 580 #ifndef EXEC_TEMPFILE_ONLY
 581   if(info->child>0)
 582     {
 583       if(waitpid(info->child,&info->progreturn,0)!=0 &&
 584          WIFEXITED(info->progreturn))
 585         ret=WEXITSTATUS(info->progreturn);
 586       else
 587         {
 588           log_error(_("unnatural exit of external program\n"));
 589           ret=127;
 590         }
 591     }
 592 #endif
 593
 594   if(info->flags.madedir && !info->flags.keep_temp_files)
 595     {
 596       if(info->tempfile_in)
 597         {
 598           if(unlink(info->tempfile_in)==-1)
 599             log_info(_("WARNING: unable to remove tempfile (%s) `%s': %s\n"),
 600                      "in",info->tempfile_in,strerror(errno));
 601         }
 602
 603       if(info->tempfile_out)
 604         {
 605           if(unlink(info->tempfile_out)==-1)
 606             log_info(_("WARNING: unable to remove tempfile (%s) `%s': %s\n"),
 607                      "out",info->tempfile_out,strerror(errno));
 608         }
 609
 610       if(rmdir(info->tempdir)==-1)
 611         log_info(_("WARNING: unable to remove temp directory `%s': %s\n"),
 612                  info->tempdir,strerror(errno));
 613     }
 614
 615   xfree(info->command);
 616   xfree(info->name);
 617   xfree(info->tempdir);
 618   xfree(info->tempfile_in);
 619   xfree(info->tempfile_out);
 620   xfree(info);
 621
 622   return ret;
 623 }
 624 #endif /* ! NO_EXEC */