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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.

/*

   auth-kerberos.c

   Hacked together by Dug Song <dugsong@umich.edu>.

   Kerberos authentication and ticket-passing routines.

*/

#include "includes.h"
#include "packet.h"
#include "xmalloc.h"
#include "ssh.h"

#ifdef KRB4
#include <sys/param.h>
#include <krb.h>

int ssh_tf_init(uid_t uid)
{
  extern char *ticket;
  char *tkt_root = TKT_ROOT;
  struct stat st;
  int fd;

  /* Set unique ticket string manually since we're still root. */
  ticket = xmalloc(MAXPATHLEN);
#ifdef AFS
  if (lstat("/ticket", &st) != -1)
    tkt_root = "/ticket/";
#endif /* AFS */
  sprintf(ticket, "%.100s%d_%d", tkt_root, uid, getpid());
  (void) krb_set_tkt_string(ticket);

  /* Make sure we own this ticket file, and we created it. */
  if (lstat(ticket, &st) < 0 && errno == ENOENT) {
    /* good, no ticket file exists. create it. */
    if ((fd = open(ticket, O_RDWR|O_CREAT|O_EXCL, 0600)) != -1) {
      close(fd);
      return 1;
    }
  }
  else {
    /* file exists. make sure server_user owns it (e.g. just passed ticket),
       and that it isn't a symlink, and that it is mode 600. */
    if (st.st_mode == (S_IFREG|S_IRUSR|S_IWUSR) && st.st_uid == uid)
      return 1;
  }
  /* Failure. */
  log("WARNING: bad ticket file %.100s", ticket);
  return 0;
}

int auth_krb4(const char *server_user, KTEXT auth, char **client)
{
  AUTH_DAT adat   = { 0 };
  KTEXT_ST reply;
  char instance[INST_SZ];
  int r, s;
  u_long cksum;
  Key_schedule schedule;
  struct sockaddr_in local, foreign;
  
  s = packet_get_connection_in();
  
  r = sizeof(local);
  memset(&local, 0, sizeof(local));
  if (getsockname(s, (struct sockaddr *) &local, &r) < 0)
    debug("getsockname failed: %.100s", strerror(errno));
  r = sizeof(foreign);
  memset(&foreign, 0, sizeof(foreign));
  if (getpeername(s, (struct sockaddr *)&foreign, &r) < 0)
    debug("getpeername failed: %.100s", strerror(errno));
  
  instance[0] = '*'; instance[1] = 0;
  
  /* Get the encrypted request, challenge, and session key. */
  r = krb_rd_req(auth, KRB4_SERVICE_NAME, instance, 0, &adat, "");
  if (r != KSUCCESS) {
    packet_send_debug("Kerberos V4 krb_rd_req: %.100s", krb_err_txt[r]);
    return 0;
  }
  des_key_sched((des_cblock *)adat.session, schedule);
  
  *client = xmalloc(MAX_K_NAME_SZ);
  sprintf(*client, "%.100s%.100s%.100s@%.100s", adat.pname, *adat.pinst ? "." : "",
		 adat.pinst, adat.prealm);

  /* Check ~/.klogin authorization now. */
  if (kuserok(&adat, (char *)server_user) != KSUCCESS) {
    packet_send_debug("Kerberos V4 .klogin authorization failed!");
    log("Kerberos V4 .klogin authorization failed for %.100s to account %.100s",
	*client, server_user);
    return 0;
  }
  /* Increment the checksum, and return it encrypted with the session key. */
  cksum = adat.checksum + 1;
  cksum = htonl(cksum);
  
  /* If we can't successfully encrypt the checksum, we send back an empty
     message, admitting our failure. */
  if ((r = krb_mk_priv((u_char *)&cksum, reply.dat, sizeof(cksum)+1,
		       schedule, &adat.session, &local, &foreign)) < 0) {
    packet_send_debug("Kerberos V4 mk_priv: (%d) %.100s", r, krb_err_txt[r]);
    reply.dat[0] = 0;
    reply.length = 0;
  }
  else
    reply.length = r;
  
  /* Clear session key. */
  memset(&adat.session, 0, sizeof(&adat.session));
  
  packet_start(SSH_SMSG_AUTH_KERBEROS_RESPONSE);
  packet_put_string((char *) reply.dat, reply.length);
  packet_send();
  packet_write_wait();
  return 1;
}
#endif /* KRB4 */

#ifdef AFS
#include <kafs.h>


#ifdef KERBEROS_TGT_PASSING

int auth_kerberos_tgt(struct passwd *pw, const char *string)
{
  CREDENTIALS creds;
  extern char *ticket;
  int r;
  
  if (!radix_to_creds(string, &creds)) {
    log("Protocol error decoding Kerberos V4 tgt");
    packet_send_debug("Protocol error decoding Kerberos V4 tgt");
    goto auth_kerberos_tgt_failure;
  }
  if (strncmp(creds.service, "", 1) == 0) /* backward compatibility */
    strcpy(creds.service, "krbtgt");
  
  if (strcmp(creds.service, "krbtgt")) {
    log("Kerberos V4 tgt (%.100s%.100s%.100s@%.100s) rejected for uid %d",
	creds.pname, creds.pinst[0] ? "." : "", creds.pinst, creds.realm,
	pw->pw_uid);
    packet_send_debug("Kerberos V4 tgt (%.100s%.100s%.100s@%.100s) rejected for uid %d",
		      creds.pname, creds.pinst[0] ? "." : "", creds.pinst,
		      creds.realm, pw->pw_uid);
    goto auth_kerberos_tgt_failure;
  }
  if (!ssh_tf_init(pw->pw_uid) ||
      (r = in_tkt(creds.pname, creds.pinst)) ||
      (r = save_credentials(creds.service,creds.instance,creds.realm,
			    creds.session,creds.lifetime,creds.kvno,
			    &creds.ticket_st,creds.issue_date))) {
    xfree(ticket);
    ticket = NULL;
    packet_send_debug("Kerberos V4 tgt refused: couldn't save credentials");
    goto auth_kerberos_tgt_failure;
  }
  /* Successful authentication, passed all checks. */
  chown(ticket, pw->pw_uid, pw->pw_gid);
  packet_send_debug("Kerberos V4 ticket accepted (%.100s.%.100s@%.100s, %.100s%.100s%.100s@%.100s)",
		    creds.service, creds.instance, creds.realm,
		    creds.pname, creds.pinst[0] ? "." : "",
		    creds.pinst, creds.realm);
  
  packet_start(SSH_SMSG_SUCCESS);
  packet_send();
  packet_write_wait();
  return 1;

auth_kerberos_tgt_failure:
  memset(&creds, 0, sizeof(creds));
  packet_start(SSH_SMSG_FAILURE);
  packet_send();
  packet_write_wait();
  return 0;
}
#endif /* KERBEROS_TGT_PASSING */

int auth_afs_token(char *server_user, uid_t uid, const char *string)
{
  CREDENTIALS creds;

  if (!radix_to_creds(string, &creds)) {
    log("Protocol error decoding AFS token");
    packet_send_debug("Protocol error decoding AFS token");
    packet_start(SSH_SMSG_FAILURE);
    packet_send();
    packet_write_wait();
    return 0;
  }
  if (strncmp(creds.service, "", 1) == 0) /* backward compatibility */
    strcpy(creds.service, "afs");
  
  if (strncmp(creds.pname, "AFS ID ", 7) == 0)
    uid = atoi(creds.pname + 7);
  
  if (kafs_settoken(creds.realm, uid, &creds)) {
    log("AFS token (%.100s@%.100s) rejected for uid %d",
	creds.pname, creds.realm, uid);
    packet_send_debug("AFS token (%.100s@%.100s) rejected for uid %d", creds.pname,
		      creds.realm, uid);
    packet_start(SSH_SMSG_FAILURE);
    packet_send();
    packet_write_wait();
    return 0;
  }
  packet_send_debug("AFS token accepted (%.100s@%.100s, %.100s@%.100s)", creds.service,
		    creds.realm, creds.pname, creds.realm);
  packet_start(SSH_SMSG_SUCCESS);
  packet_send();
  packet_write_wait();
  return 1;
}
#endif /* AFS */