## modules/pa/spawn.c

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## DEFINITIONS

This source file includes following functions.

1. spawn_job
2. nfslock
3. nfsunlock

       1 /*  spawn.c
       2
       3     Source file for spawn operations for  PGPsendmail  (wrapper to sendmail).
       4
       5     Copyright (C) 1994-1998  Richard Gooch
       6
       7     This program is free software; you can redistribute it and/or modify
       8     it under the terms of the GNU General Public License as published by
       9     the Free Software Foundation; either version 2 of the License, or
      10     (at your option) any later version.
      11
      12     This program is distributed in the hope that it will be useful,
      13     but WITHOUT ANY WARRANTY; without even the implied warranty of
      14     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
      15     GNU General Public License for more details.
      16
      17     You should have received a copy of the GNU General Public License
      18     along with this program; if not, write to the Free Software
      19     Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
      20
      21     Richard Gooch may be reached by email at  rgooch@atnf.csiro.au
      22     The postal address is:
      23       Richard Gooch, c/o ATNF, P. O. Box 76, Epping, N.S.W., 2121, Australia.
      24 */
      25
      26 /*  This programme intercepts messages sent by user mail agents to the
      27     sendmail daemon and checks to see if messages can be encrypted using the
      28     recipient's PGP public keys.
      29
      30
      31     Written by      Richard Gooch   31-MAY-1994
      32
      33     Updated by      Richard Gooch   31-MAY-1994: Extracted from  pgpsendmail.c
      34
      35     Updated by      Richard Gooch   18-JUN-1994: Made error messages more
      36   explicit.
      37
      38     Updated by      Richard Gooch   27-JUN-1994: Copied  set_env  from
      39   pgpdaemon.c
      40
      41     Updated by      Richard Gooch   5-JUL-1994: Changed to use of  m_copy  .
      42
      43     Updated by      Richard Gooch   14-JUL-1994: Moved  copy_data  and  set_env
      44   to  misc.c
      45
      46     Updated by      Richard Gooch   3-DEC-1994: Fixed bug for externally set
      47   error descriptor.
      48
      49     Updated by      Richard Gooch   25-SEP-1997: Used new ERRSTRING macro.
      50
      51     Last updated by Richard Gooch   10-JUL-1998: Removed definitions of system
      52   errlist array.
      53
      54
      55 */
      56
      57 #include "rip.h"
      58
      59 #include <stdio.h>
      60 #include <stdlib.h>
      61 #include <errno.h>
      62 #include <sys/types.h>
      63 #include <unistd.h>
      64 #include <string.h>
      65 #include <sys/stat.h>
      66 #include <fcntl.h>
      67 #include <time.h>
      68
      69 /* #include "pgpsendmail.h" */
      70
      71 #ifndef ERRSTRING
      72 #define ERRSTRING strerror(errno)
      73 #endif /* ERRSTRING */
      74
      75 #define LINE_LENGTH 1024
      76 #define STRING_LENGTH 255
      77
      78 enum NFSL {
      79   NFSL_SYSF,
      80   NFSL_SECV,
      81   NFSL_LOCKED,
      82   NFSL_OK,
      83   NFSL_STOLEN,
      84   NFSL_LOST
      85 };
      86
      87
      88 int sd1[2] /*, sd2[2] */;  /* sd2 is used to have a collaborative
      89                                   dialogue between processes          */
      90 int spawn_job (char *path, char *argv[], int *in_fd, int *out_fd, int *err_fd)
         /* [<][>][^][v][top][bottom][index][help] */
      91 /*  This routine will fork(2) and execvp(2) a process.
      92     The file to execute must be pointed to by  path  .
      93     The NULL terminated list of arguments which will be passed to  main  must
      94     be pointed to by  argv  .
      95     The input file descriptor (fd = 0) for the process must be pointed to by
      96     in_fd  .If the value here is less than 0, then a pipe to the process is
      97     opened and the writeable end is written to the storage pointed to by  in_fd
      98     The standard output file descriptor (fd = 1) for the process must be
      99     pointed to by  out_fd  .If the value here is less than 0, then a pipe to
     100     the process is opened and the readable end is written to the storage
     101     pointed to by  out_fd  .
     102     The standard error output file descriptor (fd = 2) for the process must be
     103     pointed to by  err_fd  .If the value here is less than 0, then a pipe to
     104     the process is opened and the readable end is written to the storage
     105     pointed to by  err_fd  .
     106     The routine returns the child process ID on success, else it returns -1.
     107 */
     108 {
     109     int child_pid;
     110     /*     char txt[LINE_LENGTH];  */
     111
     112     if (pipe(sd1) == -1)
     113       {
     114         perror("pipe failed");
     115         return(1);
     116       }
     117
     118     /*  Fork and exec  */
     119     switch ( child_pid = fork () )
     120     {
     121       case 0:
     122         /*  Child: exec  */
     123         close(sd1[0]);
     124
     125         dup2( sd1[1], 1 );   /* stdout */
     126
     127         /*      fprintf (stderr, "dup2 1 result: %s\n", ERRSTRING); */
     128         dup2( sd1[1], 2 );    /* stderr */
     129         /*      fprintf (stderr, "dup2 2 result: %s\n", ERRSTRING); */
     130
     131         execvp (path, argv);
     132
     133         fprintf (stderr, "Could not exec: \"%s\"\t%s\n", path, ERRSTRING);
     134         exit (1);
     135         break;
     136       case -1:
     137         /*  Error  */
     138         fprintf (stderr, "Could not fork\t%s\n", ERRSTRING);
     139         return (-1);
     140         break;
     141       default:
     142         /*  Parent  */
     143         break;
     144     }
     145     /*  Parent only  */
     146
     147     close(sd1[1]);
     148
     149     dup2 (sd1[0], 0);
     150
     151     /*     fprintf (stderr, "dup2 0 result: %s\n", ERRSTRING);  */
     152     /*     fprintf(stderr, "Reading child output\n");
     153     while (read(0, txt, 1000) != 0)
     154       fprintf(stderr, "child read %s\n", txt);
     155
     156       fprintf(stderr, "Finished reading child output\n");   */
     157
     158     return (child_pid);
     159 }   /*  End Function spawn_job  */
     160
     161
     162 #define DEFAULT_LOCKTIME 300;
     163
     164 time_t nfslock(char *path, char *namelock, int max_age, int notify)
         /* [<][>][^][v][top][bottom][index][help] */
     165 {
     166   int tries = 0, oldlck = 0, tmpfd;
     167   struct stat old_stat, our_tmp;
     168   char tmp[32];
     169   char *tpath, *fullpath;
     170
     171   srandom(getpid()+time(0));
     172   max_age = max_age ? max_age : DEFAULT_LOCKTIME;
     173
     174   /*
     175    * 1. create a tmp file with a psuedo random file name. we also make
     176    *    tpath which is a buffer to store the full pathname of the tmp file.
     177    */
     178
     179   sprintf(tmp,"slock%d.%d", (int)getpid(), (int)random());
     180
     181   tpath = UT_malloc(strlen(path) + 1 + strlen(tmp) + 1);
     182   if (tpath == NULL) return(NFSL_SYSF);
     183   sprintf(tpath,"%s/%s", path, tmp);
     184
     185   tmpfd = open(tpath, O_CREAT|O_WRONLY|O_EXCL, S_IRUSR|S_IWUSR);
     186
     187   if (tmpfd < 0) {      /* open failed */
     188     close(tmpfd);
     189     unlink(tpath);
     190     UT_free(tpath);
     191     return(NFSL_SYSF);
     192   }
     193
     194   if (getuid()==0) {    /* we're root, so be careful! */
     195     if (fstat(tmpfd, &our_tmp) < 0) {   /* stat failed... shouldn't happen */
     196       close(tmpfd);
     197       unlink(tpath);
     198       UT_free(tpath);
     199       return(NFSL_SYSF);
     200     }
     201     if (our_tmp.st_nlink != 1) {        /* someone's trying to mess with us */
     202       fprintf(stderr,"nfslock: bad link count on %s\n",tpath);
     203       close(tmpfd);
     204       unlink(tpath);
     205       UT_free(tpath);
     206       return(NFSL_SECV);
     207     }
     208   }
     209
     210   /*
     211    * 2. make fullpath, a buffer for the full pathname of the lock file.
     212    *    then start looping trying to lock it
     213    */
     214
     215   fullpath = UT_malloc(strlen(path) + 1 + strlen(namelock) + 1);
     216   if (fullpath == NULL) {
     217     close(tmpfd);
     218     unlink(tpath);
     219     UT_free(tpath);
     220     return(NFSL_SYSF);
     221   }
     222   sprintf(fullpath,"%s/%s", path, namelock);
     223
     224   while (tries < 10) {
     225
     226     /*
     227      * 3. link tmp file to lock file.  if it goes, we win and we clean
     228      *    up and return the st_ctime of the lock file.
     229      */
     230
     231     if (link(tpath, fullpath) == 0) {
     232       unlink(tpath); /* got it! */
     233       UT_free(tpath);
     234       close(tmpfd);
     235       if (lstat(fullpath, &our_tmp) < 0) {      /* stat failed... shouldn't happen */
     236         unlink(fullpath);
     237         UT_free(fullpath);
     238         return (NFSL_SYSF);
     239       }
     240       UT_free(fullpath);
     241       return(our_tmp.st_ctime);
     242     }
     243
     244     /*
     245      * 4. the lock failed.  check for a stale lock file, being mindful
     246      *    of NFS and the fact the time is set from the NFS server.  we
     247      *    do a write on the tmp file to update its time to the server's
     248      *    idea of "now."
     249      */
     250
     251     oldlck = lstat(fullpath, &old_stat);
     252
     253     if (write(tmpfd, "\0", 1) != 1 || fstat(tmpfd, &our_tmp) < 0)
     254       break; /* something bogus is going on */
     255
     256     if (oldlck != -1 && old_stat.st_ctime + max_age < our_tmp.st_ctime) {
     257       unlink(fullpath); /* break the stale lock */
     258       if (notify) fprintf(stderr,"Breaking stale lock on %s.\n",fullpath);
     259       tries++;
     260       sleep(1+(random() % 10)); /* It is CRITICAL that we sleep after breaking
     261                                  * the lock. Otherwise, we could race with
     262                                  * another process and unlink it's newly-
     263                                  * created file.
     264                                  */
     265       continue;
     266     }
     267
     268     /*
     269      * 5. try again
     270      */
     271
     272     if (notify) {
     273       if (tries==0) fprintf(stderr,"Waiting for lock on file %s.\n",fullpath);
     274       else fprintf(stderr,"Still waiting...\n");
     275     }
     276     tries++;
     277     sleep(1+(random() % 10));
     278   }
     279
     280   /*
     281    * 6. give up, failure.
     282    */
     283
     284   errno = EEXIST;
     285   unlink(tpath);
     286   UT_free(tpath);
     287   UT_free(fullpath);
     288   close(tmpfd);
     289   return(NFSL_LOCKED);
     290 }
     291
     292 int nfsunlock(char *path, char *namelock, int max_age, time_t birth)
         /* [<][>][^][v][top][bottom][index][help] */
     293 {
     294   int tmpfd;
     295   struct stat old_stat, our_tmp;
     296   char *tpath, *fullpath;
     297
     298   srandom(getpid()+time(0));
     299   max_age = max_age ? max_age : DEFAULT_LOCKTIME;
     300
     301   /*
     302    * 1. Build a temp file and stat that to get an idea of what the server
     303    *    thinks the current time is (our_tmp.st_ctime)..
     304    */
     305
     306   tpath = UT_malloc(strlen(path) + 25);   /* small slop factor- 23 s/b enough */
     307   if (tpath == NULL) return(NFSL_SYSF);
     308   sprintf(tpath,"%s/slock%d.%d", path, (int)getpid(), (int)random());
     309
     310   tmpfd = open(tpath, O_CREAT|O_WRONLY|O_EXCL, S_IRUSR|S_IWUSR);
     311
     312   if ((tmpfd < 0) || (write(tmpfd, "\0", 1) != 1)
     313                   || (fstat(tmpfd, &our_tmp) < 0)) {
     314     /* The open failed, or we can't write the file, or we can't stat it */
     315     close(tmpfd);
     316     unlink(tpath);
     317     UT_free(tpath);
     318     return(NFSL_SYSF);
     319   }
     320
     321   close(tmpfd);         /* We don't need this once we have our_tmp.st_ctime. */
     322   unlink(tpath);
     323   UT_free(tpath);
     324
     325   /*
     326    * 2. make fullpath, a buffer for the full pathname of the lock file
     327    */
     328
     329   fullpath = UT_malloc(strlen(path) + 1 + strlen(namelock) + 1);
     330   if (fullpath == NULL)
     331     return(NFSL_SYSF);
     332   sprintf(fullpath,"%s/%s", path, namelock);
     333
     334   /*
     335    * 3. If the ctime hasn't been modified, unlink the file and return. If the
     336    *    lock has expired, sleep the usual random interval before returning.
     337    *    If we didn't sleep, there could be a race if the caller immediately
     338    *    tries to relock the file.
     339    */
     340
     341   if ( !lstat(fullpath, &old_stat) &&   /* stat succeeds so file is there */
     342       (old_stat.st_ctime == birth)) {   /* hasn't been modified since birth */
     343     unlink(fullpath);                   /* so the lock is ours to remove */
     344     if (our_tmp.st_ctime >= birth + max_age)    /* the lock has expired */
     345       sleep(1+(random() % 10));         /* so sleep a bit */
     346     UT_free(fullpath);
     347     return(NFSL_OK);                    /* success */
     348   }
     349
     350   UT_free(fullpath);       /* we don't use fullpath anymore */
     351
     352   /*
     353    * 4. Either ctime has been modified, or the entire lock file is missing.
     354    *    If the lock should still be ours, based on the ctime of the temp
     355    *    file, return with NFSL_STOLEN. If not, then our lock is expired and
     356    *    someone else has grabbed the file, so return NFSL_LOST.
     357    */
     358
     359   if (our_tmp.st_ctime < birth + max_age)       /* lock was stolen */
     360     return(NFSL_STOLEN);
     361
     362   return(NFSL_LOST);    /* The lock must have expired first. */
     363 }
     364
     365
     366

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