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