heimdal/lib/krb5/recvauth.c

/*
 * Copyright (c) 1997-2007 Kungliga Tekniska Högskolan
 * (Royal Institute of Technology, Stockholm, Sweden).
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * 3. Neither the name of the Institute nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include "krb5_locl.h"

/*
 * See `sendauth.c' for the format.
 */

static krb5_boolean
match_exact(const void *data, const char *appl_version)
{
    return strcmp(data, appl_version) == 0;
}

/**
 * Perform the server side of the sendauth protocol.
 *
 * @param context       Kerberos 5 context.
 * @param auth_context  authentication context of the peer.
 * @param p_fd          socket associated to the connection.
 * @param appl_version  server-specific string.
 * @param server        server principal.
 * @param flags         if KRB5_RECVAUTH_IGNORE_VERSION is set, skip the sendauth version
 *                      part of the protocol.
 * @param keytab        server keytab.
 * @param ticket        on success, set to the authenticated client credentials.
 *                      Must be deallocated with krb5_free_ticket(). If not
 *                      interested, pass a NULL value.
 *
 * @return 0 to indicate success. Otherwise a Kerberos error code is
 *         returned, see krb5_get_error_message().
 */
KRB5_LIB_FUNCTION krb5_error_code KRB5_LIB_CALL
krb5_recvauth(krb5_context context,
	      krb5_auth_context *auth_context,
	      krb5_pointer p_fd,
	      const char *appl_version,
	      krb5_principal server,
	      int32_t flags,
	      krb5_keytab keytab,
	      krb5_ticket **ticket)
{
    return krb5_recvauth_match_version(context, auth_context, p_fd,
				       match_exact, appl_version,
				       server, flags,
				       keytab, ticket);
}

/**
 * Perform the server side of the sendauth protocol like krb5_recvauth(), but support
 * a user-specified callback, \a match_appl_version, to perform the match of the application
 * version \a match_data.
 */
KRB5_LIB_FUNCTION krb5_error_code KRB5_LIB_CALL
krb5_recvauth_match_version(krb5_context context,
			    krb5_auth_context *auth_context,
			    krb5_pointer p_fd,
			    krb5_boolean (*match_appl_version)(const void *,
							       const char*),
			    const void *match_data,
			    krb5_principal server,
			    int32_t flags,
			    krb5_keytab keytab,
			    krb5_ticket **ticket)
{
    krb5_error_code ret;
    const char *version = KRB5_SENDAUTH_VERSION;
    char her_version[sizeof(KRB5_SENDAUTH_VERSION)];
    char *her_appl_version;
    uint32_t len;
    u_char repl;
    krb5_data data;
    krb5_flags ap_options;
    ssize_t n;

    /*
     * If there are no addresses in auth_context, get them from `fd'.
     */

    if (*auth_context == NULL) {
	ret = krb5_auth_con_init (context, auth_context);
	if (ret)
	    return ret;
    }

    ret = krb5_auth_con_setaddrs_from_fd (context,
					  *auth_context,
					  p_fd);
    if (ret)
	return ret;

    /*
     * Expect SENDAUTH protocol version.
     */
    if(!(flags & KRB5_RECVAUTH_IGNORE_VERSION)) {
	n = krb5_net_read (context, p_fd, &len, 4);
	if (n < 0) {
	    ret = errno ? errno : EINVAL;
	    krb5_set_error_message(context, ret, "read: %s", strerror(ret));
	    return ret;
	}
	if (n == 0) {
	    krb5_set_error_message(context, KRB5_SENDAUTH_BADAUTHVERS,
				   N_("Failed to receive sendauth data", ""));
	    return KRB5_SENDAUTH_BADAUTHVERS;
	}
	len = ntohl(len);
	if (len != sizeof(her_version)
	    || krb5_net_read (context, p_fd, her_version, len) != len
	    || strncmp (version, her_version, len) != 0) {
	    repl = 1;
	    krb5_net_write (context, p_fd, &repl, 1);
	    krb5_clear_error_message (context);
	    return KRB5_SENDAUTH_BADAUTHVERS;
	}
    }

    /*
     * Expect application protocol version.
     */
    n = krb5_net_read (context, p_fd, &len, 4);
    if (n < 0) {
	ret = errno ? errno : EINVAL;
	krb5_set_error_message(context, ret, "read: %s", strerror(ret));
	return ret;
    }
    if (n == 0) {
	krb5_clear_error_message (context);
	return KRB5_SENDAUTH_BADAPPLVERS;
    }
    len = ntohl(len);
    her_appl_version = malloc (len);
    if (her_appl_version == NULL) {
	repl = 2;
	krb5_net_write (context, p_fd, &repl, 1);
	return krb5_enomem(context);
    }
    if (krb5_net_read (context, p_fd, her_appl_version, len) != len
	|| !(*match_appl_version)(match_data, her_appl_version)) {
	repl = 2;
	krb5_net_write (context, p_fd, &repl, 1);
	krb5_set_error_message(context, KRB5_SENDAUTH_BADAPPLVERS,
			       N_("wrong sendauth application version (%s)", ""),
			       her_appl_version);
	free (her_appl_version);
	return KRB5_SENDAUTH_BADAPPLVERS;
    }
    free (her_appl_version);

    /*
     * Send OK.
     */
    repl = 0;
    if (krb5_net_write (context, p_fd, &repl, 1) != 1) {
	ret = errno ? errno : EINVAL;
	krb5_set_error_message(context, ret, "write: %s", strerror(ret));
	return ret;
    }

    /*
     * Until here, the fields in the message were in cleartext and unauthenticated.
     * From now on, Kerberos kicks in.
     */

    /*
     * Expect AP_REQ.
     */
    krb5_data_zero (&data);
    ret = krb5_read_message (context, p_fd, &data);
    if (ret)
	return ret;

    ret = krb5_rd_req (context,
		       auth_context,
		       &data,
		       server,
		       keytab,
		       &ap_options,
		       ticket);
    krb5_data_free (&data);
    if (ret) {
	krb5_data error_data;
	krb5_error_code ret2;

	ret2 = krb5_mk_error (context,
			      ret,
			      NULL,
			      NULL,
			      NULL,
			      server,
			      NULL,
			      NULL,
			      &error_data);
	if (ret2 == 0) {
	    krb5_write_message (context, p_fd, &error_data);
	    krb5_data_free (&error_data);
	}
	return ret;
    }

    /*
     * Send OK.
     */
    len = 0;
    if (krb5_net_write (context, p_fd, &len, 4) != 4) {
	ret = errno ? errno : EINVAL;
	krb5_set_error_message(context, ret, "write: %s", strerror(ret));
	krb5_free_ticket(context, *ticket);
	*ticket = NULL;
	return ret;
    }

    /*
     * If client requires mutual authentication, send AP_REP.
     */
    if (ap_options & AP_OPTS_MUTUAL_REQUIRED) {
	ret = krb5_mk_rep (context, *auth_context, &data);
	if (ret) {
	    krb5_free_ticket(context, *ticket);
	    *ticket = NULL;
	    return ret;
	}

	ret = krb5_write_message (context, p_fd, &data);
	if (ret) {
	    krb5_free_ticket(context, *ticket);
	    *ticket = NULL;
	    return ret;
	}
	krb5_data_free (&data);
    }
    return 0;
}