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skey_fn.c

/* 
   Copyright (c) 1995-2000 by Cisco systems, Inc.

   Permission to use, copy, modify, and distribute modified and
   unmodified copies of this software for any purpose and without fee is
   hereby granted, provided that (a) this copyright and permission notice
   appear on all copies of the software and supporting documentation, (b)
   the name of Cisco Systems, Inc. not be used in advertising or
   publicity pertaining to distribution of the program without specific
   prior permission, and (c) notice be given in supporting documentation
   that use, modification, copying and distribution is by permission of
   Cisco Systems, Inc.

   Cisco Systems, Inc. makes no representations about the suitability
   of this software for any purpose.  THIS SOFTWARE IS PROVIDED ``AS
   IS'' AND WITHOUT ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING,
   WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
   FITNESS FOR A PARTICULAR PURPOSE.
*/

#ifdef SKEY
#include "tac_plus.h"
#include "expire.h"

/* internal state variables */
#define STATE_AUTHEN_START   0      /* no requests issued */
#define STATE_AUTHEN_GETUSER 1      /* username has been requested */
#define STATE_AUTHEN_GETPASS 2      /* password has been requested */

#include <skey.h>

struct private_data {
    struct skey skey;
    char password[MAX_PASSWD_LEN + 1];
    int state;
};

/* Use s/key to verify a supplied password using state set up earlier
when the username was supplied */

static int
skey_verify(passwd, data)
char *passwd;
struct authen_data *data;
{
    struct private_data *p = data->method_data;
    struct skey *skeyp = &p->skey;

    data->status = TAC_PLUS_AUTHEN_STATUS_FAIL;

    if (skeyverify(skeyp, passwd) == 0) {
      /* S/Key authentication succeeded */
      data->status = TAC_PLUS_AUTHEN_STATUS_PASS;
      if (skeyp->n < 5) {
          data->server_msg = tac_strdup("Password will expire soon");
          return (1);
      }
    }
    return (0);
}

/*
 * Skey tacacs login authentication function. Wants a username
 * and a password, and tries to verify them via skey.
 *
 * Choose_authen will ensure that we already have a username before this
 * gets called.
 *
 * We will query for a password and keep it in the method_data.
 *
 * Any strings returned via pointers in authen_data must come from the
 * heap. They will get freed by the caller.
 *
 * Return 0 if data->status is valid, otherwise 1
 */

int
skey_fn(data)
struct authen_data *data;
{
    char *name, *passwd;
    struct private_data *p;
    char *prompt;
    int pwlen;

    p = (struct private_data *) data->method_data;

    /* An abort has been received. Clean up and return */
    if (data->flags & TAC_PLUS_CONTINUE_FLAG_ABORT) {
      if (data->method_data)
          free(data->method_data);
      data->method_data = NULL;
      return (1);
    }
    /* Initialise method_data if first time through */
    if (!p) {
      p = (struct private_data *) tac_malloc(sizeof(struct private_data));
      bzero(p, sizeof(struct private_data));
      data->method_data = p;
      p->state = STATE_AUTHEN_START;
    }

    /* Unless we're enabling, we need a username */
    if (data->service != TAC_PLUS_AUTHEN_SVC_ENABLE &&
      !(char) data->NAS_id->username[0]) {
      switch (p->state) {

      case STATE_AUTHEN_GETUSER:
          /* we have previously asked for a username but none came back.
           * This is a gross error */
          data->status = TAC_PLUS_AUTHEN_STATUS_ERROR;
          report(LOG_ERR, "%s: No username supplied after GETUSER",
               session.peer);
          return (0);

      case STATE_AUTHEN_START:
          /* No username. Try requesting one */
          data->status = TAC_PLUS_AUTHEN_STATUS_GETUSER;
          if (data->service == TAC_PLUS_AUTHEN_SVC_LOGIN) {
            prompt = "\nUser Access Verification\n\nUsername: ";
          } else {
            prompt = "Username: ";
          }
          data->server_msg = tac_strdup(prompt);
          p->state = STATE_AUTHEN_GETUSER;
          return (0);

      default:
          /* something awful has happened. Give up and die */
          report(LOG_ERR, "%s: skey_fn bad state %d", 
               session.peer, p->state);
          return (1);
      }
    }

    /* we now have a username if we needed one */
    name = data->NAS_id->username;

    /* Do we have a password? */
    passwd = p->password;

    if (!passwd[0]) {
      char skeyprompt[80];

      /* no password yet. Either we need to ask for one and expect to get
       * called again, or we asked but nothing came back, which is fatal */

      switch (p->state) {
      case STATE_AUTHEN_GETPASS:
          /* We already asked for a password. This should be the reply */
          if (data->client_msg) {
            pwlen = MIN(strlen(data->client_msg), MAX_PASSWD_LEN);
          } else {
            pwlen = 0;
          }
          strncpy(passwd, data->client_msg, pwlen);
          passwd[pwlen] = '\0';
          break;

      default:
          /* Request a password */
          passwd = cfg_get_login_secret(name, TAC_PLUS_RECURSE);
          if (!passwd && !STREQ(passwd, "skey")) {
            report(LOG_ERR, "Cannot find skey password declaration for %s",
                   name);
            data->status = TAC_PLUS_AUTHEN_STATUS_ERROR;
            return(1);
          }

          if (skeychallenge(&p->skey, name, skeyprompt) == 0) {
            char buf[256];
            sprintf(buf, "%s\nPassword: ", skeyprompt);
            data->server_msg = tac_strdup(buf);
            data->status = TAC_PLUS_AUTHEN_STATUS_GETPASS;
            p->state = STATE_AUTHEN_GETPASS;
            return (0);
          } 

          data->status = TAC_PLUS_AUTHEN_STATUS_ERROR;
          report(LOG_ERR, "Cannot generate skey prompt for %s", name);
          return(1);
      }
    }

    /* We have a username and password. Try validating */

    /* Assume the worst */
    data->status = TAC_PLUS_AUTHEN_STATUS_FAIL;

    switch (data->service) {
    case TAC_PLUS_AUTHEN_SVC_LOGIN:
      skey_verify(passwd, data);
      if (debug)
          report(LOG_INFO, "login query for '%s' %s from %s %s",
               name && name[0] ? name : "unknown",
               data->NAS_id->NAS_port && data->NAS_id->NAS_port[0] ?
                   data->NAS_id->NAS_port : "unknown",
               session.peer,
               (data->status == TAC_PLUS_AUTHEN_STATUS_PASS) ?
               "accepted" : "rejected");
      break;

    default:
      data->status = TAC_PLUS_AUTHEN_STATUS_ERROR;
      report(LOG_ERR, "%s: Bogus service value %d from packet", 
             session.peer, data->service);
      break;
    }

    if (data->method_data)
      free(data->method_data);
    data->method_data = NULL;

    switch (data->status) {
    case TAC_PLUS_AUTHEN_STATUS_ERROR:
    case TAC_PLUS_AUTHEN_STATUS_FAIL:
    case TAC_PLUS_AUTHEN_STATUS_PASS:
      return (0);
    default:
      report(LOG_ERR, "%s: skey_fn couldn't set recognizable status %d",
             session.peer, data->status);
      data->status = TAC_PLUS_AUTHEN_STATUS_ERROR;
      return (1);
    }
}
#else /* SKEY */

/* The following code is not needed or used. It exists solely to
   prevent compilers from "helpfully" complaining that this source
   file is empty, which upsets novices building the software */

static int dummy = 0;

#endif /* SKEY */

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