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Annotation of coherent/g/usr/lib/uucp/tay104/unix/spawn.c, revision 1.1

1.1     ! root        1: /* spawn.c
        !             2:    Spawn a program securely.
        !             3: 
        !             4:    Copyright (C) 1992 Ian Lance Taylor
        !             5: 
        !             6:    This file is part of the Taylor UUCP package.
        !             7: 
        !             8:    This program is free software; you can redistribute it and/or
        !             9:    modify it under the terms of the GNU General Public License as
        !            10:    published by the Free Software Foundation; either version 2 of the
        !            11:    License, or (at your option) any later version.
        !            12: 
        !            13:    This program is distributed in the hope that it will be useful, but
        !            14:    WITHOUT ANY WARRANTY; without even the implied warranty of
        !            15:    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
        !            16:    General Public License for more details.
        !            17: 
        !            18:    You should have received a copy of the GNU General Public License
        !            19:    along with this program; if not, write to the Free Software
        !            20:    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
        !            21: 
        !            22:    The author of the program may be contacted at [email protected] or
        !            23:    c/o Infinity Development Systems, P.O. Box 520, Waltham, MA 02254.
        !            24:    */
        !            25: 
        !            26: #include "uucp.h"
        !            27: 
        !            28: #include "uudefs.h"
        !            29: #include "sysdep.h"
        !            30: 
        !            31: #include <errno.h>
        !            32: 
        !            33: #if HAVE_FCNTL_H
        !            34: #include <fcntl.h>
        !            35: #else
        !            36: #if HAVE_SYS_FILE_H
        !            37: #include <sys/file.h>
        !            38: #endif
        !            39: #endif
        !            40: 
        !            41: #ifndef O_RDONLY
        !            42: #define O_RDONLY 0
        !            43: #define O_WRONLY 1
        !            44: #define O_RDWR 2
        !            45: #endif
        !            46: 
        !            47: #ifndef FD_CLOEXEC
        !            48: #define FD_CLOEXEC 1
        !            49: #endif
        !            50: 
        !            51: #ifndef environ
        !            52: extern char **environ;
        !            53: #endif
        !            54: 
        !            55: /* Spawn a child in a fairly secure fashion.  This returns the process
        !            56:    ID of the child or -1 on error.  It takes far too many arguments:
        !            57: 
        !            58:    pazargs -- arguments (element 0 is command)
        !            59:    aidescs -- file descriptors for stdin, stdout and stderr
        !            60:    fkeepuid -- TRUE if euid should be left unchanged
        !            61:    fkeepenv -- TRUE if environment should be left unmodified
        !            62:    zchdir -- directory to chdir to
        !            63:    fnosigs -- TRUE if child should ignore SIGHUP, SIGINT and SIGQUIT
        !            64:    fshell -- TRUE if should try /bin/sh if execve gets ENOEXEC
        !            65:    zpath -- value for environment variable PATH
        !            66:    zuu_machine -- value for environment variable UU_MACHINE
        !            67:    zuu_user -- value for environment variable UU_USER
        !            68: 
        !            69:    The aidescs array is three elements long.  0 is stdin, 1 is stdout
        !            70:    and 2 is stderr.  The array may contain either file descriptor
        !            71:    numbers to dup appropriately, or one of the following:
        !            72: 
        !            73:    SPAWN_NULL -- set descriptor to /dev/null
        !            74:    SPAWN_READ_PIPE -- set aidescs element to pipe for parent to read
        !            75:    SPAWN_WRITE_PIPE -- set aidescs element to pipe for parent to write
        !            76: 
        !            77:    If fkeepenv is FALSE, a standard environment is created.  The
        !            78:    environment arguments (zpath, zuu_machine and zuu_user) are only
        !            79:    used if fkeepenv is FALSE; any of them may be NULL.
        !            80: 
        !            81:    This routine expects that all file descriptors have been set to
        !            82:    close-on-exec, so it doesn't have to worry about closing them
        !            83:    explicitly.  It sets the close-on-exec flag for the new pipe
        !            84:    descriptors it returns.  */
        !            85: 
        !            86: pid_t
        !            87: ixsspawn (pazargs, aidescs, fkeepuid, fkeepenv, zchdir, fnosigs, fshell,
        !            88:          zpath, zuu_machine, zuu_user)
        !            89:      const char **pazargs;
        !            90:      int aidescs[3];
        !            91:      boolean fkeepuid;
        !            92:      boolean fkeepenv;
        !            93:      const char *zchdir;
        !            94:      boolean fnosigs;
        !            95:      boolean fshell;
        !            96:      const char *zpath;
        !            97:      const char *zuu_machine;
        !            98:      const char *zuu_user;
        !            99: {
        !           100:   char *zshcmd;
        !           101:   int i;
        !           102:   char *azenv[9];
        !           103:   char **pazenv;
        !           104:   boolean ferr;
        !           105:   int ierr = 0;
        !           106:   int onull;
        !           107:   int aichild_descs[3];
        !           108:   int cpar_close;
        !           109:   int aipar_close[4];
        !           110:   int cchild_close;
        !           111:   int aichild_close[3];
        !           112:   pid_t iret = 0;
        !           113:   const char *zcmd;
        !           114: 
        !           115:   /* If we might have to use the shell, allocate enough space for the
        !           116:      quoted command before forking.  Otherwise the allocation would
        !           117:      modify the data segment and we could not safely use vfork.  */
        !           118:   zshcmd = NULL;
        !           119:   if (fshell)
        !           120:     {
        !           121:       size_t clen;
        !           122: 
        !           123:       clen = 0;
        !           124:       for (i = 0; pazargs[i] != NULL; i++)
        !           125:        clen += strlen (pazargs[i]);
        !           126:       zshcmd = zbufalc (2 * clen + i);
        !           127:     }
        !           128: 
        !           129:   /* Set up a standard environment.  This is again done before forking
        !           130:      because it will modify the data segment.  */
        !           131:   if (fkeepenv)
        !           132:     pazenv = environ;
        !           133:   else
        !           134:     {
        !           135:       const char *zterm, *ztz;
        !           136:       char *zspace;
        !           137:       int ienv;
        !           138: 
        !           139:       if (zpath == NULL)
        !           140:        zpath = CMDPATH;
        !           141: 
        !           142:       azenv[0] = zbufalc (sizeof "PATH=" + strlen (zpath));
        !           143:       sprintf (azenv[0], "PATH=%s", zpath);
        !           144:       zspace = azenv[0] + sizeof "PATH=" - 1;
        !           145:       while ((zspace = strchr (zspace, ' ')) != NULL)
        !           146:        *zspace = ':';
        !           147:     
        !           148:       azenv[1] = zbufalc (sizeof "HOME=" + strlen (zSspooldir));
        !           149:       sprintf (azenv[1], "HOME=%s", zSspooldir);
        !           150: 
        !           151:       zterm = getenv ("TERM");
        !           152:       if (zterm == NULL)
        !           153:        zterm = "unknown";
        !           154:       azenv[2] = zbufalc (sizeof "TERM=" + strlen (zterm));
        !           155:       sprintf (azenv[2], "TERM=%s", zterm);
        !           156: 
        !           157:       azenv[3] = zbufcpy ("SHELL=/bin/sh");
        !           158:   
        !           159:       azenv[4] = zbufalc (sizeof "USER=" + strlen (OWNER));
        !           160:       sprintf (azenv[4], "USER=%s", OWNER);
        !           161: 
        !           162:       ienv = 5;
        !           163: 
        !           164:       ztz = getenv ("TZ");
        !           165:       if (ztz != NULL)
        !           166:        {
        !           167:          azenv[ienv] = zbufalc (sizeof "TZ=" + strlen (ztz));
        !           168:          sprintf (azenv[ienv], "TZ=%s", ztz);
        !           169:          ++ienv;
        !           170:        }
        !           171: 
        !           172:       if (zuu_machine != NULL)
        !           173:        {
        !           174:          azenv[ienv] = zbufalc (sizeof "UU_MACHINE="
        !           175:                                 + strlen (zuu_machine));
        !           176:          sprintf (azenv[ienv], "UU_MACHINE=%s", zuu_machine);
        !           177:          ++ienv;
        !           178:        }
        !           179: 
        !           180:       if (zuu_user != NULL)
        !           181:        {
        !           182:          azenv[ienv] = zbufalc (sizeof "UU_USER="
        !           183:                                 + strlen (zuu_user));
        !           184:          sprintf (azenv[ienv], "UU_USER=%s", zuu_user);
        !           185:          ++ienv;
        !           186:        }
        !           187: 
        !           188:       azenv[ienv] = NULL;
        !           189:       pazenv = azenv;
        !           190:     }
        !           191: 
        !           192:   /* Set up any needed pipes.  */
        !           193: 
        !           194:   ferr = FALSE;
        !           195:   onull = -1;
        !           196:   cpar_close = 0;
        !           197:   cchild_close = 0;
        !           198: 
        !           199:   for (i = 0; i < 3; i++)
        !           200:     {
        !           201:       if (aidescs[i] == SPAWN_NULL)
        !           202:        {
        !           203:          if (onull < 0)
        !           204:            {
        !           205:              onull = open ((char *) "/dev/null", O_RDWR);
        !           206:              if (onull < 0
        !           207:                  || fcntl (onull, F_SETFD,
        !           208:                            fcntl (onull, F_GETFD, 0) | FD_CLOEXEC) < 0)
        !           209:                {
        !           210:                  ierr = errno;
        !           211:                  (void) close (onull);
        !           212:                  ferr = TRUE;
        !           213:                  break;
        !           214:                }
        !           215:              aipar_close[cpar_close] = onull;
        !           216:              ++cpar_close;
        !           217:            }
        !           218:          aichild_descs[i] = onull;
        !           219:        }
        !           220:       else if (aidescs[i] != SPAWN_READ_PIPE
        !           221:               && aidescs[i] != SPAWN_WRITE_PIPE)
        !           222:        aichild_descs[i] = aidescs[i];
        !           223:       else
        !           224:        {
        !           225:          int aipipe[2];
        !           226: 
        !           227:          if (pipe (aipipe) < 0)
        !           228:            {
        !           229:              ierr = errno;
        !           230:              ferr = TRUE;
        !           231:              break;
        !           232:            }
        !           233: 
        !           234:          if (aidescs[i] == SPAWN_READ_PIPE)
        !           235:            {
        !           236:              aidescs[i] = aipipe[0];
        !           237:              aichild_close[cchild_close] = aipipe[0];
        !           238:              aichild_descs[i] = aipipe[1];
        !           239:              aipar_close[cpar_close] = aipipe[1];
        !           240:            }
        !           241:          else
        !           242:            {
        !           243:              aidescs[i] = aipipe[1];
        !           244:              aichild_close[cchild_close] = aipipe[1];
        !           245:              aichild_descs[i] = aipipe[0];
        !           246:              aipar_close[cpar_close] = aipipe[0];
        !           247:            }
        !           248: 
        !           249:          ++cpar_close;
        !           250:          ++cchild_close;
        !           251: 
        !           252:          if (fcntl (aidescs[i], F_SETFD,
        !           253:                     fcntl (aidescs[i], F_GETFD, 0) | FD_CLOEXEC) < 0)
        !           254:            {
        !           255:              ierr = errno;
        !           256:              ferr = TRUE;
        !           257:              break;
        !           258:            }         
        !           259:        }
        !           260:     }
        !           261: 
        !           262: #if DEBUG > 1
        !           263:   if (! ferr && FDEBUGGING (DEBUG_EXECUTE))
        !           264:     {
        !           265:       ulog (LOG_DEBUG_START, "Forking %s", pazargs[0]);
        !           266:       for (i = 1; pazargs[i] != NULL; i++)
        !           267:        ulog (LOG_DEBUG_CONTINUE, " %s", pazargs[i]);
        !           268:       ulog (LOG_DEBUG_END, "%s", "");
        !           269:     }
        !           270: #endif
        !           271: 
        !           272:   if (! ferr)
        !           273:     {
        !           274:       /* This should really be vfork if available.  */
        !           275:       iret = ixsfork ();
        !           276:       if (iret < 0)
        !           277:        {
        !           278:          ferr = TRUE;
        !           279:          ierr = errno;
        !           280:        }
        !           281:     }
        !           282: 
        !           283:   if (ferr)
        !           284:     {
        !           285:       for (i = 0; i < cchild_close; i++)
        !           286:        (void) close (aichild_close[i]);
        !           287:       iret = -1;
        !           288:     }
        !           289: 
        !           290:   if (iret != 0)
        !           291:     {
        !           292:       /* The parent.  Close the child's ends of the pipes and return
        !           293:         the process ID, or an error.  */
        !           294:       for (i = 0; i < cpar_close; i++)
        !           295:        (void) close (aipar_close[i]);
        !           296:       ubuffree (zshcmd);
        !           297:       if (! fkeepenv)
        !           298:        {
        !           299:          char **pz;
        !           300: 
        !           301:          for (pz = azenv; *pz != NULL; pz++)
        !           302:            ubuffree (*pz);
        !           303:        }
        !           304:       errno = ierr;
        !           305:       return iret;
        !           306:     }
        !           307: 
        !           308:   /* The child.  */
        !           309: 
        !           310: #ifdef STDIN_FILENO
        !           311: #if STDIN_FILENO != 0 || STDOUT_FILENO != 1 || STDERR_FILENO != 2
        !           312:  #error The following code makes invalid assumptions
        !           313: #endif
        !           314: #endif
        !           315: 
        !           316:   for (i = 0; i < 3; i++)
        !           317:     {
        !           318:       if (aichild_descs[i] != i)
        !           319:        (void) dup2 (aichild_descs[i], i);
        !           320:       /* This should only be necessary if aichild_descs[i] == i, but
        !           321:         some systems copy the close-on-exec flag for a dupped
        !           322:         descriptor, which is wrong according to POSIX.  */
        !           323:       (void) fcntl (i, F_SETFD, fcntl (i, F_GETFD, 0) &~ FD_CLOEXEC);
        !           324:     }
        !           325: 
        !           326:   zcmd = pazargs[0];
        !           327:   pazargs[0] = strrchr (zcmd, '/');
        !           328:   if (pazargs[0] == NULL)
        !           329:     pazargs[0] = zcmd;
        !           330:   else
        !           331:     ++pazargs[0];
        !           332: 
        !           333:   if (! fkeepuid)
        !           334:     {
        !           335:       (void) setuid (getuid ());
        !           336:       (void) setgid (getgid ());
        !           337:     }
        !           338: 
        !           339:   if (zchdir != NULL)
        !           340:     (void) chdir (zchdir);
        !           341: 
        !           342:   if (fnosigs)
        !           343:     {
        !           344: #ifdef SIGHUP
        !           345:       (void) signal (SIGHUP, SIG_IGN);
        !           346: #endif
        !           347: #ifdef SIGINT
        !           348:       (void) signal (SIGINT, SIG_IGN);
        !           349: #endif
        !           350: #ifdef SIGQUIT
        !           351:       (void) signal (SIGQUIT, SIG_IGN);
        !           352: #endif
        !           353:     }
        !           354: 
        !           355:   (void) execve ((char *) zcmd, (char **) pazargs, pazenv);
        !           356: 
        !           357:   /* The exec failed.  If permitted, try using /bin/sh to execute a
        !           358:      shell script.  */
        !           359: 
        !           360:   if (errno == ENOEXEC && fshell)
        !           361:     {
        !           362:       char *zto;
        !           363:       const char *azshargs[4];
        !           364:       
        !           365:       pazargs[0] = zcmd;
        !           366:       zto = zshcmd;
        !           367:       for (i = 0; pazargs[i] != NULL; i++)
        !           368:        {
        !           369:          const char *zfrom;
        !           370: 
        !           371:          for (zfrom = pazargs[i]; *zfrom != '\0'; zfrom++)
        !           372:            {
        !           373:              /* Some versions of /bin/sh appear to have a bug such
        !           374:                 that quoting a '/' sometimes causes an error.  I
        !           375:                 don't know exactly when this happens (I can recreate
        !           376:                 it on Ultrix 4.0), but in any case it is harmless to
        !           377:                 not quote a '/'.  */
        !           378:              if (*zfrom != '/')
        !           379:                *zto++ = '\\';
        !           380:              *zto++ = *zfrom;
        !           381:            }
        !           382:          *zto++ = ' ';
        !           383:        }
        !           384:       *(zto - 1) = '\0';
        !           385: 
        !           386:       azshargs[0] = "sh";
        !           387:       azshargs[1] = "-c";
        !           388:       azshargs[2] = zshcmd;
        !           389:       azshargs[3] = NULL;
        !           390: 
        !           391:       (void) execve ((char *) "/bin/sh", (char **) azshargs, pazenv);
        !           392:     }
        !           393: 
        !           394:   _exit (EXIT_FAILURE);
        !           395: 
        !           396:   /* Avoid compiler warning.  */
        !           397:   return -1;
        !           398: }

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