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 2 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, write to the Free Software
  18  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
  19  * USA.
  20  */
  21
  22 #include <config.h>
  23 #include <stdlib.h>
  24 #include <stdarg.h>
  25 #include <stdio.h>
  26 #include <sys/stat.h>
  27 #include <sys/types.h>
  28 #ifndef EXEC_TEMPFILE_ONLY
  29 #include <sys/wait.h>
  30 #endif
  31 #ifdef HAVE_DOSISH_SYSTEM
  32 #include <windows.h>
  33 #endif
  34 #include <fcntl.h>
  35 #include <unistd.h>
  36 #include <string.h>
  37 #include <errno.h>
  38
  39 #include "gpg.h"
  40 #include "options.h"
  41 #include "i18n.h"
  42 #include "iobuf.h"
  43 #include "util.h"
  44 #include "mkdtemp.h"  /* From gnulib. */
  45 #include "exec.h"
  46
  47 #ifdef NO_EXEC
  48 int exec_write(struct exec_info **info,const char *program,
  49                const char *args_in,const char *name,int writeonly,int binary)
  50 {
  51   log_error(_("no remote program execution supported\n"));
  52   return G10ERR_GENERAL;
  53 }
  54
  55 int exec_read(struct exec_info *info) { return G10ERR_GENERAL; }
  56 int exec_finish(struct exec_info *info) { return G10ERR_GENERAL; }
  57 int set_exec_path(const char *path) { return G10ERR_GENERAL; }
  58
  59 #else /* ! NO_EXEC */
  60
  61 #if defined (_WIN32)
  62 /* This is a nicer system() for windows that waits for programs to
  63    return before returning control to the caller.  I hate helpful
  64    computers. */
  65 static int w32_system(const char *command)
  66 {
  67   PROCESS_INFORMATION pi;
  68   STARTUPINFO si;
  69   char *string;
  70
  71   /* We must use a copy of the command as CreateProcess modifies this
  72      argument. */
  73   string=xstrdup(command);
  74
  75   memset(&pi,0,sizeof(pi));
  76   memset(&si,0,sizeof(si));
  77   si.cb=sizeof(si);
  78
  79   if(!CreateProcess(NULL,string,NULL,NULL,FALSE,0,NULL,NULL,&si,&pi))
  80     return -1;
  81
  82   /* Wait for the child to exit */
  83   WaitForSingleObject(pi.hProcess,INFINITE);
  84
  85   CloseHandle(pi.hProcess);
  86   CloseHandle(pi.hThread);
  87   xfree(string);
  88
  89   return 0;
  90 }
  91 #endif
  92
  93 /* Replaces current $PATH */
  94 int set_exec_path(const char *path)
  95 {
  96   char *p;
  97
  98   p=xmalloc(5+strlen(path)+1);
  99   strcpy(p,"PATH=");
 100   strcat(p,path);
 101
 102   if(DBG_EXTPROG)
 103     log_debug("set_exec_path: %s\n",p);
 104
 105   /* Notice that path is never freed.  That is intentional due to the
 106      way putenv() works.  This leaks a few bytes if we call
 107      set_exec_path multiple times. */
 108
 109   if(putenv(p)!=0)
 110     return G10ERR_GENERAL;
 111   else
 112     return 0;
 113 }
 114
 115 /* Makes a temp directory and filenames */
 116 static int make_tempdir(struct exec_info *info)
 117 {
 118   char *tmp=opt.temp_dir,*namein=info->name,*nameout;
 119
 120   if(!namein)
 121     namein=info->flags.binary?"tempin" EXTSEP_S "bin":"tempin" EXTSEP_S "txt";
 122
 123   nameout=info->flags.binary?"tempout" EXTSEP_S "bin":"tempout" EXTSEP_S "txt";
 124
 125   /* Make up the temp dir and files in case we need them */
 126
 127   if(tmp==NULL)
 128     {
 129 #if defined (_WIN32)
 130       int err;
 131
 132       tmp=xmalloc(MAX_PATH+2);
 133       err=GetTempPath(MAX_PATH+1,tmp);
 134       if(err==0 || err>MAX_PATH+1)
 135         strcpy(tmp,"c:\\windows\\temp");
 136       else
 137         {
 138           int len=strlen(tmp);
 139
 140           /* GetTempPath may return with \ on the end */
 141           while(len>0 && tmp[len-1]=='\\')
 142             {
 143               tmp[len-1]='\0';
 144               len--;
 145             }
 146         }
 147 #else /* More unixish systems */
 148       tmp=getenv("TMPDIR");
 149       if(tmp==NULL)
 150         {
 151           tmp=getenv("TMP");
 152           if(tmp==NULL)
 153             {
 154 #ifdef __riscos__
 155               tmp="<Wimp$ScrapDir>.GnuPG";
 156               mkdir(tmp,0700); /* Error checks occur later on */
 157 #else
 158               tmp="/tmp";
 159 #endif
 160             }
 161         }
 162 #endif
 163     }
 164
 165   info->tempdir=xmalloc(strlen(tmp)+strlen(DIRSEP_S)+10+1);
 166
 167   sprintf(info->tempdir,"%s" DIRSEP_S "gpg-XXXXXX",tmp);
 168
 169 #if defined (_WIN32)
 170   xfree(tmp);
 171 #endif
 172
 173   if(mkdtemp(info->tempdir)==NULL)
 174     log_error(_("can't create directory `%s': %s\n"),
 175               info->tempdir,strerror(errno));
 176   else
 177     {
 178       info->flags.madedir=1;
 179
 180       info->tempfile_in=xmalloc(strlen(info->tempdir)+
 181                                 strlen(DIRSEP_S)+strlen(namein)+1);
 182       sprintf(info->tempfile_in,"%s" DIRSEP_S "%s",info->tempdir,namein);
 183
 184       if(!info->flags.writeonly)
 185         {
 186           info->tempfile_out=xmalloc(strlen(info->tempdir)+
 187                                      strlen(DIRSEP_S)+strlen(nameout)+1);
 188           sprintf(info->tempfile_out,"%s" DIRSEP_S "%s",info->tempdir,nameout);
 189         }
 190     }
 191
 192   return info->flags.madedir?0:G10ERR_GENERAL;
 193 }
 194
 195 /* Expands %i and %o in the args to the full temp files within the
 196    temp directory. */
 197 static int expand_args(struct exec_info *info,const char *args_in)
 198 {
 199   const char *ch=args_in;
 200   unsigned int size,len;
 201
 202   info->flags.use_temp_files=0;
 203   info->flags.keep_temp_files=0;
 204
 205   if(DBG_EXTPROG)
 206     log_debug("expanding string \"%s\"\n",args_in);
 207
 208   size=100;
 209   info->command=xmalloc(size);
 210   len=0;
 211   info->command[0]='\0';
 212
 213   while(*ch!='\0')
 214     {
 215       if(*ch=='%')
 216         {
 217           char *append=NULL;
 218
 219           ch++;
 220
 221           switch(*ch)
 222             {
 223             case 'O':
 224               info->flags.keep_temp_files=1;
 225               /* fall through */
 226
 227             case 'o': /* out */
 228               if(!info->flags.madedir)
 229                 {
 230                   if(make_tempdir(info))
 231                     goto fail;
 232                 }
 233               append=info->tempfile_out;
 234               info->flags.use_temp_files=1;
 235               break;
 236
 237             case 'I':
 238               info->flags.keep_temp_files=1;
 239               /* fall through */
 240
 241             case 'i': /* in */
 242               if(!info->flags.madedir)
 243                 {
 244                   if(make_tempdir(info))
 245                     goto fail;
 246                 }
 247               append=info->tempfile_in;
 248               info->flags.use_temp_files=1;
 249               break;
 250
 251             case '%':
 252               append="%";
 253               break;
 254             }
 255
 256           if(append)
 257             {
 258               size_t applen=strlen(append);
 259
 260               if(applen+len>size-1)
 261                 {
 262                   if(applen<100)
 263                     applen=100;
 264
 265                   size+=applen;
 266                   info->command=xrealloc(info->command,size);
 267                 }
 268
 269               strcat(info->command,append);
 270               len+=strlen(append);
 271             }
 272         }
 273       else
 274         {
 275           if(len==size-1) /* leave room for the \0 */
 276             {
 277               size+=100;
 278               info->command=xrealloc(info->command,size);
 279             }
 280
 281           info->command[len++]=*ch;
 282           info->command[len]='\0';
 283         }
 284
 285       ch++;
 286     }
 287
 288   if(DBG_EXTPROG)
 289     log_debug("args expanded to \"%s\", use %u, keep %u\n",info->command,
 290               info->flags.use_temp_files,info->flags.keep_temp_files);
 291
 292   return 0;
 293
 294  fail:
 295
 296   xfree(info->command);
 297   info->command=NULL;
 298
 299   return G10ERR_GENERAL;
 300 }
 301
 302 /* Either handles the tempfile creation, or the fork/exec.  If it
 303    returns ok, then info->tochild is a FILE * that can be written to.
 304    The rules are: if there are no args, then it's a fork/exec/pipe.
 305    If there are args, but no tempfiles, then it's a fork/exec/pipe via
 306    shell -c.  If there are tempfiles, then it's a system. */
 307
 308 int exec_write(struct exec_info **info,const char *program,
 309                const char *args_in,const char *name,int writeonly,int binary)
 310 {
 311   int ret=G10ERR_GENERAL;
 312
 313   if(opt.exec_disable && !opt.no_perm_warn)
 314     {
 315       log_info(_("external program calls are disabled due to unsafe "
 316                  "options file permissions\n"));
 317
 318       return ret;
 319     }
 320
 321 #if defined(HAVE_GETUID) && defined(HAVE_GETEUID)
 322   /* There should be no way to get to this spot while still carrying
 323      setuid privs.  Just in case, bomb out if we are. */
 324   if(getuid()!=geteuid())
 325     BUG();
 326 #endif
 327
 328   if(program==NULL && args_in==NULL)
 329     BUG();
 330
 331   *info=xmalloc_clear(sizeof(struct exec_info));
 332
 333   if(name)
 334     (*info)->name=xstrdup(name);
 335   (*info)->flags.binary=binary;
 336   (*info)->flags.writeonly=writeonly;
 337
 338   /* Expand the args, if any */
 339   if(args_in && expand_args(*info,args_in))
 340     goto fail;
 341
 342 #ifdef EXEC_TEMPFILE_ONLY
 343   if(!(*info)->flags.use_temp_files)
 344     {
 345       log_error(_("this platform requires temporary files when calling"
 346                   " external programs\n"));
 347       goto fail;
 348     }
 349
 350 #else /* !EXEC_TEMPFILE_ONLY */
 351
 352   /* If there are no args, or there are args, but no temp files, we
 353      can use fork/exec/pipe */
 354   if(args_in==NULL || (*info)->flags.use_temp_files==0)
 355     {
 356       int to[2],from[2];
 357
 358       if(pipe(to)==-1)
 359         goto fail;
 360
 361       if(pipe(from)==-1)
 362         {
 363           close(to[0]);
 364           close(to[1]);
 365           goto fail;
 366         }
 367
 368       if(((*info)->child=fork())==-1)
 369         {
 370           close(to[0]);
 371           close(to[1]);
 372           close(from[0]);
 373           close(from[1]);
 374           goto fail;
 375         }
 376
 377       if((*info)->child==0)
 378         {
 379           char *shell=getenv("SHELL");
 380
 381           if(shell==NULL)
 382             shell="/bin/sh";
 383
 384           /* I'm the child */
 385
 386           /* If the program isn't going to respond back, they get to
 387              keep their stdout/stderr */
 388           if(!(*info)->flags.writeonly)
 389             {
 390               /* implied close of STDERR */
 391               if(dup2(STDOUT_FILENO,STDERR_FILENO)==-1)
 392                 _exit(1);
 393
 394               /* implied close of STDOUT */
 395               close(from[0]);
 396               if(dup2(from[1],STDOUT_FILENO)==-1)
 397                 _exit(1);
 398             }
 399
 400           /* implied close of STDIN */
 401           close(to[1]);
 402           if(dup2(to[0],STDIN_FILENO)==-1)
 403             _exit(1);
 404
 405           if(args_in==NULL)
 406             {
 407               if(DBG_EXTPROG)
 408                 log_debug("execlp: %s\n",program);
 409
 410               execlp(program,program,(void *)NULL);
 411             }
 412           else
 413             {
 414               if(DBG_EXTPROG)
 415                 log_debug("execlp: %s -c %s\n",shell,(*info)->command);
 416
 417               execlp(shell,shell,"-c",(*info)->command,(void *)NULL);
 418             }
 419
 420           /* If we get this far the exec failed.  Clean up and return. */
 421
 422           if(args_in==NULL)
 423             log_error(_("unable to execute program `%s': %s\n"),
 424                       program,strerror(errno));
 425           else
 426             log_error(_("unable to execute shell `%s': %s\n"),
 427                       shell,strerror(errno));
 428
 429           /* This mimics the POSIX sh behavior - 127 means "not found"
 430              from the shell. */
 431           if(errno==ENOENT)
 432             _exit(127);
 433
 434           _exit(1);
 435         }
 436
 437       /* I'm the parent */
 438
 439       close(to[0]);
 440
 441       (*info)->tochild=fdopen(to[1],binary?"wb":"w");
 442       if((*info)->tochild==NULL)
 443         {
 444           ret = gpg_error_from_errno (errno);
 445           close(to[1]);
 446           goto fail;
 447         }
 448
 449       close(from[1]);
 450
 451       (*info)->fromchild=iobuf_fdopen(from[0],"r");
 452       if((*info)->fromchild==NULL)
 453         {
 454           ret = gpg_error_from_errno (errno);
 455           close(from[0]);
 456           goto fail;
 457         }
 458
 459       /* fd iobufs are cached?! */
 460       iobuf_ioctl((*info)->fromchild,3,1,NULL);
 461
 462       return 0;
 463     }
 464 #endif /* !EXEC_TEMPFILE_ONLY */
 465
 466   if(DBG_EXTPROG)
 467     log_debug("using temp file `%s'\n",(*info)->tempfile_in);
 468
 469   /* It's not fork/exec/pipe, so create a temp file */
 470   if( is_secured_filename ((*info)->tempfile_in) )
 471     {
 472       (*info)->tochild = NULL;
 473       errno = EPERM;
 474     }
 475   else
 476     (*info)->tochild=fopen((*info)->tempfile_in,binary?"wb":"w");
 477   if((*info)->tochild==NULL)
 478     {
 479       ret = gpg_error_from_errno (errno);
 480       log_error(_("can't create `%s': %s\n"),
 481                 (*info)->tempfile_in,strerror(errno));
 482       goto fail;
 483     }
 484
 485   ret=0;
 486
 487  fail:
 488   return ret;
 489 }
 490
 491 int exec_read(struct exec_info *info)
 492 {
 493   int ret=G10ERR_GENERAL;
 494
 495   fclose(info->tochild);
 496   info->tochild=NULL;
 497
 498   if(info->flags.use_temp_files)
 499     {
 500       if(DBG_EXTPROG)
 501         log_debug("system() command is %s\n",info->command);
 502
 503 #if defined (_WIN32)
 504       info->progreturn=w32_system(info->command);
 505 #else
 506       info->progreturn=system(info->command);
 507 #endif
 508
 509       if(info->progreturn==-1)
 510         {
 511           log_error(_("system error while calling external program: %s\n"),
 512                     strerror(errno));
 513           info->progreturn=127;
 514           goto fail;
 515         }
 516
 517 #if defined(WIFEXITED) && defined(WEXITSTATUS)
 518       if(WIFEXITED(info->progreturn))
 519         info->progreturn=WEXITSTATUS(info->progreturn);
 520       else
 521         {
 522           log_error(_("unnatural exit of external program\n"));
 523           info->progreturn=127;
 524           goto fail;
 525         }
 526 #else
 527       /* If we don't have the macros, do the best we can. */
 528       info->progreturn = (info->progreturn & 0xff00) >> 8;
 529 #endif
 530
 531       /* 127 is the magic value returned from system() to indicate
 532          that the shell could not be executed, or from /bin/sh to
 533          indicate that the program could not be executed. */
 534
 535       if(info->progreturn==127)
 536         {
 537           log_error(_("unable to execute external program\n"));
 538           goto fail;
 539         }
 540
 541       if(!info->flags.writeonly)
 542         {
 543           info->fromchild=iobuf_open(info->tempfile_out);
 544           if (info->fromchild
 545               && is_secured_file (iobuf_get_fd (info->fromchild)))
 546             {
 547               iobuf_close (info->fromchild);
 548               info->fromchild = NULL;
 549               errno = EPERM;
 550             }
 551           if(info->fromchild==NULL)
 552             {
 553               ret = gpg_error_from_errno (errno);
 554               log_error(_("unable to read external program response: %s\n"),
 555                         strerror(errno));
 556               goto fail;
 557             }
 558
 559           /* Do not cache this iobuf on close */
 560           iobuf_ioctl(info->fromchild,3,1,NULL);
 561         }
 562     }
 563
 564   ret=0;
 565
 566  fail:
 567   return ret;
 568 }
 569
 570 int 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 */