Attachment 214 Details for Bug 479 – zzh.c - a minimum server-side shell

zzh.c - a minimum server-side shell

zzh.c (text/plain), 2.69 KB, created by Ralf Hauser on 2003-01-31 03:02:48 AEDT

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Creator: Ralf Hauser

Created: 2003-01-31 03:02:48 AEDT

Size: 2.69 KB

patch

obsolete

>/*
> * zzh.c
> *
> * Shell for the "SSH Sleeping Beauty" user.
> *
> * (c) 1999, Tim Hemel <tim@n2it.net>
> *
> * More info see http://cuba.xs4all.nl/~tim/scvs/
> * 
> * Modified by Michael Steiner <steiner@acm.org> to add a few safety checks
> *
> * $Id: zzh.c,v 1.1 2001/03/06 16:38:03 sti Exp $
> */
>
>#include <stdio.h>
>#include <stdlib.h>
>#include <sys/types.h>
>#include <sys/time.h>
>#include <sys/stat.h>
>#include <unistd.h>
>#include <fcntl.h>
>
>/* Timeout in seconds */
>const int ZZZ = 10*60;
>#define MAX_CMD_LEN 255
>const char* PREFIX = P_tmpdir"/zzh";	/* prefix for tmpfiles */
>
>char cmd[MAX_CMD_LEN+1];
>
>/* simple commandline parsing */
>void parse_opt(int argc, char *argv[])
>{
>  int i,done;
>
>  done = 0;
>  for (i=0; (i<argc-1) && !done ; i++)
>  {
>    if (!strcmp(argv[i],"-c"))
>    {
>      strncpy(cmd,argv[i+1],MAX_CMD_LEN);
>      cmd[MAX_CMD_LEN] = '\0';
>      done = 1;
>    }
>  }
>}
>
>int main ( int argc, char* argv[] )
>{
>  int i;
>  char *fn;
>  int fd; 
>  fd_set fs;
>  struct timeval to;
>  struct stat sb;
>
>  /* set cmd to "" */
>  cmd[0]='\0';
>
>  parse_opt(argc, argv);
>
>  /* if no command string, exit */
>  if (!strcmp(cmd,"")) exit(0);
>
>  /* check what the command is */
>  if (!strcmp(cmd,"open"))
>  {
>    /* create a temporary filename, which will be used as a magic word */
>    fn = malloc(strlen(PREFIX) + strlen("XXXXXX") + 1);
>    if (fn==NULL) {
>      perror("no memory"); exit(1);
>    }
>    strcpy(fn, PREFIX);
>    strcat(fn, "XXXXXX");
>    mktemp(fn); 
>    fprintf(stdout,"%s\n",fn); fflush(stdout);
>    /* create a named pipe with this name */
>    if (mkfifo(fn, 0600)) {
>      perror("mkfifo"); exit(2);
>    }
>    if ((fd = open(fn,O_RDONLY)) == 0 ) {
>      perror("open"); exit(3);
>    }
>    /* set up a file descriptor set for select() */
>    FD_ZERO(&fs);
>    FD_SET(fd,&fs);
>    /* set the ZZZ second timeout */
>    to.tv_sec = ZZZ;
>
>    /* wait for input and do nothing with it */
>    if (select(fd+1, &fs, 0, 0, &to)>0) {
>      /* lseek(fd,0,SEEK_END); /* not necessary */
>    }
>    /* remove the temporary file */
>    unlink(fn);
>  }
>  else /* cmd != "" && cmd != "open" */
>  {
>    /* see if a file named cmd exists, .... */
>    if (stat(cmd,&sb)) {
>      perror("stat"); exit(1);
>    }
>    /* ... is a named pipe, ... */
>    if (!(sb.st_mode & S_IFIFO)) {
>      fprintf(stderr, "not named pipe "); exit(2);
>    }
>    /* ... is owned by me, ... */
>    if (sb.st_uid != getuid()) {
>      fprintf(stderr, "not owned by me"); exit(3);
>    }
>    /* ...  and finally is valid tmpfile */
>    if (strncmp(cmd, PREFIX, strlen(PREFIX))) {
>      fprintf(stderr, "wrong place"); exit(4);
>    }
>    /* Everything's allright: write to it */
>    fd = open(cmd,O_WRONLY);
>    if (fd > 0) { write(fd, "wake up", 1); }
>  }
> 
>  /* return 0; */
>  exit(0);
>}

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