Source Code 1992 March/Source_Code_CD-ROM_Walnut_Creek_March_1992.iso/usenet/altsrcs/3/3543/undomserver.c

C/C++ Source or Header | 1991-06-26 | 5.5 KB | 219 lines

/* Public domain. */

#include <stdio.h>
#include <signal.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/wait.h>
#include <sys/un.h>
#include <sys/time.h>
#include "dupdup.h"
#include "malloc.h"
#include "errno.h"
#include "username.h"
#include "env.h"
#include "getopt.h"
#include "numfiles.h"

static int flagprintlocal = 0;
static int flagverbose = 1;
static struct sockaddr_un sabind;
static int flagbindok = 0;

SIGRET sigterm()
{
 if (flagbindok)
   unlink(sabind.sun_path);
 exit(0);
}

SIGRET sigchld()
{
 wait((union wait *) 0); /*XXX*/
}

static char errbuf[500];
void die(n,s) int n; char *s;
{ if (flagverbose) fprintf(stderr,"undomserver: fatal: %s\n",s); exit(n); }
void dies(n,s,t) int n; char *s; char *t;
{ if (flagverbose) fprintf(stderr,"undomserver: fatal: %s%s\n",s,t); exit(n); }
void diep(n,s) int n; char *s;
{ if (flagverbose) sprintf(errbuf,"undomserver: fatal: %s",s); perror(errbuf); exit(n); }
void warnp(s) char *s;
{ if (flagverbose) sprintf(errbuf,"undomserver: warning: %s",s); perror(errbuf); }
void warnsp(s,t) char *s; char *t;
{ if (flagverbose) sprintf(errbuf,"undomserver: warning: %s%s",s,t); perror(errbuf); }

main(argc,argv,envp)
int argc;
char *argv[];
char *envp[];
{
 int s;
 int dummy;
 int t;
 int *d;
 int tdup;
 int numfiles;
 static struct sockaddr_un sa;
 int uid;
 int arguid;
 int i;
 char undomlocal[200]; /*XXX*/
 char undomremote[300]; /*XXX*/
 unsigned char urlen;
 int opt;

 while ((opt = getopt(argc,argv,"qQ4")) != EOF)
   switch(opt)
    {
     case 'q':
       flagverbose = 0;
       break;
     case 'Q':
       flagverbose = 1;
       break;
     case '4':
       flagprintlocal = 1;
       break;
     case '?':
       break; /*XXX*/
     default:
       break; /*XXX*/
    }
 argc -= optind; argv += optind;

 if (argc < 3)
   die(1,"need at least three arguments");

 uid = getuid();
 if (username2uid(argv[0],&arguid) == -1)
   dies(2,"cannot figure out username ",argv[0]);
 if (uid && (uid != arguid))
   dies(3,"permission denied for username ",argv[0]);

 for (i = 0;argv[0][i];++i)
   if ((argv[0][i] == '/') || (argv[0][i] == ':') || (argv[0][i] == '.') || (argv[0][i] == '\n'))
     dies(4,"illegal characters in username ",argv[0]);

 for (i = 0;argv[1][i];++i)
   if ((argv[1][i] == '/') || (argv[1][i] == '.') || (argv[0][i] == '\n'))
     dies(5,"illegal characters in service ",argv[1]);

 close(6);
 close(7); /* XXX: these have implications that should be documented */

 numfiles = NUMFILES;
 d = (int *) malloc(numfiles * sizeof(int));
 if (!d)
   die(6,"cannot malloc");
 for (i = 0;i < numfiles;++i)
   d[i] = -1;

 if (strlen(UNDOMDIR) + strlen(argv[0]) + strlen(argv[1]) + 1 > 100) /*XXX*/
   die(8,"server socket name too long");
 sprintf(sabind.sun_path,"%s/%s:%s",UNDOMDIR,argv[0],argv[1]);

 signal(SIGTERM,sigterm);
 signal(SIGINT,sigterm);
 signal(SIGCHLD,sigchld);

 if (env_init() == -1)
   die(11,"cannot init environment");
 if (env_put("PROTO=UNDOM") == -1)
   die(11,"out of memory putting PROTO into environment");
 sprintf(undomlocal,"UNDOMLOCAL=%s:%s",argv[0],argv[1]);
 if (env_put(undomlocal) == -1)
   die(11,"out of memory putting UNDOMLOCAL into environment");
 sprintf(undomremote,"UNDOMREMOTE=");

 if (flagprintlocal)
  {
   FILE *fd4;
   fd4 = fdopen(4,"w");
   if (!fd4)
     die(1,"cannot print UNDOMLOCAL on fd 4");
   fprintf(fd4,"%s:%s\n",argv[0],argv[1]);
   fclose(fd4);
   close(4); /* just in case */
  }

 s = socket(AF_UNIX,SOCK_STREAM,0);
 if (s == -1)
   diep(7,"cannot create server socket");
 sabind.sun_family = AF_UNIX;
 if (bind(s,(struct sockaddr *) &sabind,strlen(sabind.sun_path) + 2) == -1)
   dies(9,"cannot bind server socket ",sabind.sun_path);
 /* XXX: there's a race right here */
 flagbindok = 1;
 if (listen(s,5) == -1)
  {
   unlink(sabind.sun_path);
   diep(10,"cannot listen on server socket");
  }

 for (;;)
  {
   /* XXX: don't accept too many requests at once? */
   dummy = sizeof(sa);
   t = accept(s,(struct sockaddr *) &sa,&dummy);
   if (t == -1) /* so when can this happen? */
    {
     switch(errno)
      {
       case SIGCHLD: break; /*XXX*/
       case EINTR: break; /*XXX*/
       case EMFILE: sleep(1); break; /*XXX*/
       case ENFILE: sleep(1); break; /*XXX*/
       default: ; /*XXX*/
      }
     continue;
    }

   if (((i = read(t,&urlen,1)) == -1) || (!i))
     continue; /* XXX: error message? */
   if (urlen == 0) /* XXX: undomkiller */
     sigterm();

   switch(fork())
    {
     case -1:
       warnp("cannot fork");
       break;

     case 0:

       if (urlen > sizeof(undomremote) - strlen(undomremote) - 5)
     die(1,"remote username too long");
       if (read(t,undomremote + strlen(undomremote),urlen) < urlen)
     die(1,"cannot read remote username");
       undomremote[sizeof(undomremote) - 1] = 0; /* just in case */
       /* XXX: warn if it's not already just the right length? */

       if (env_put(undomremote) == -1)
     die(1,"out of memory putting UNDOMREMOTE into environment");

       tdup = dup(t);
       if (tdup == -1)
     diep(1,"cannot dup connection to client");

       /* Now put t into descriptor 6 and tdup into descriptor 7. */
       /* XXX: should check that t and tdup are small enough */
       d[t] = 6;
       d[tdup] = 7;
       if (dupdup(d,numfiles) == -1)
     diep(1,"cannot dup connection to client");

       if (setreuid(uid,uid) == -1)
     diep(1,"cannot setreuid"); /* will never happen */
       execvp(argv[2],argv + 2);
       warnsp("cannot exec ",argv[2]);
       exit(1);

     default:
       close(t);
    }
  }
}