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