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i bet a lot of people didn't know what ssh 1.2.16 had a nice license.
well, except for the patent issues.  someone in sweden (forget their
name at the moment) cleaned out most of the patented code, and now
this code removes rsa code.  when this is done, it will link against
libssl, but the work isn't completely done yet.  then we need to bring
this up to modern days, featurewise.

/*

gen_minfd.c

Author: David Mazieres <dm@lcs.mit.edu>
	Contributed to be part of ssh.

Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
                   All rights reserved

Created: Tue Aug 22 17:22:57 1995 ylo
Last modified: Tue Aug 22 17:44:32 1995 ylo

*/

#include "includes.h"
#include <sys/resource.h>
#include "fdlim.h"

static char *self;

static void
child_test (char *fdstr)
{
  int fd = atoi (fdstr);
  if (fcntl (fd, F_GETFL, NULL) < 0) {
    exit (1);
  }
  exit (0);
}

static int
run_child (char *shell, int fd)
{
  char cmd[128];
  int pid;
  int status;

  if (dup2 (0, fd) < 0) {
    perror ("dup2");
    return (-1);
  }

  sprintf (cmd, "%s -fd %d", self, fd);

  fflush (stdout);
  pid = fork ();
  if (! pid) {
    close (1);  /* prevent any garbage from entering the output */
    dup (2);
    execlp (shell, shell, "-c", cmd, NULL);
    exit (1);
  }
  close (fd);
  if (wait (&status) != pid) {
    fprintf (stderr, "wrong/no child??\n");
    exit (1);
  }
  return (status ? -1 : 0);
}

static int
do_shell (char *shell)
{
  int fd, min, max;

  min = 3;
  max = fdlim_get (0) - 1;
  if (max < 0) {
    printf ("fdlim_get: bad value\n");
    exit (1);
  }

  if (run_child (shell, max)
      && run_child (shell, --max))  /* bizarre ultrix weirdness */
    return (-1);

  while (min + 1 < max) {
    fd = (min + max) / 2;
    if (run_child (shell, fd))
      min = fd;
    else
      max = fd;
  }
  return (max);
}

int
main (int argc, char **argv)
{
  int fd;
  int i;
  char *p;

  if (argc == 3 && !strcmp (argv[1], "-fd"))
    child_test (argv[2]);
  self = argv[0];

  fd = fdlim_get (1);
  if (fd < 0) {
    fprintf (stderr, "fdlim_get: bad value\n");
    exit (1);
  }
  fdlim_set (fd);
  printf ("/* maximum file descriptors = %d */\n\n", fd);
  printf ("struct Min_Auth_Fd {\n"
	  "  int fd;\n"
	  "  char shell[32];\n"
	  "};\n\n"
	  "static struct Min_Auth_Fd mafd[] = {\n");
  for (i = 1; i < argc; i++) {
    fd = do_shell (argv[i]);
    if ((p = strrchr (argv[i], '/')))
      p++;
    else
      p = argv[i];
    if (fd > 0)
      printf ("  { %d, \"%s\" },\n", fd, p);
  }
  printf ("  { 0, \"\" },\n};\n\n"
	  "#define MAFD_MAX (sizeof (mafd) / sizeof (mafd[0]) - 1)\n");
  return (0);
}