rd_safe.c   [plain text]

/*
 * lib/krb5/krb/rd_safe.c
 *
 * Copyright 1990,1991,2007,2008 by the Massachusetts Institute of Technology.
 * All Rights Reserved.
 *
 * Export of this software from the United States of America may
 *   require a specific license from the United States Government.
 *   It is the responsibility of any person or organization contemplating
 *   export to obtain such a license before exporting.
 * 
 * WITHIN THAT CONSTRAINT, permission to use, copy, modify, and
 * distribute this software and its documentation for any purpose and
 * without fee is hereby granted, provided that the above copyright
 * notice appear in all copies and that both that copyright notice and
 * this permission notice appear in supporting documentation, and that
 * the name of M.I.T. not be used in advertising or publicity pertaining
 * to distribution of the software without specific, written prior
 * permission.  Furthermore if you modify this software you must label
 * your software as modified software and not distribute it in such a
 * fashion that it might be confused with the original M.I.T. software.
 * M.I.T. makes no representations about the suitability of
 * this software for any purpose.  It is provided "as is" without express
 * or implied warranty.
 * 
 *
 * krb5_rd_safe()
 */

#include "k5-int.h"
#include "cleanup.h"
#include "auth_con.h"

/*
 parses a KRB_SAFE message from inbuf, placing the integrity-protected user
 data in *outbuf.

 key specifies the key to be used for decryption of the message.
 
 sender_addr and recv_addr specify the full addresses (host and port) of
 the sender and receiver.

 outbuf points to allocated storage which the caller should free when finished.

 returns system errors, integrity errors
 */
static krb5_error_code
krb5_rd_safe_basic(krb5_context context, const krb5_data *inbuf,
		   const krb5_keyblock *keyblock,
		   const krb5_address *recv_addr,
		   const krb5_address *sender_addr,
		   krb5_replay_data *replaydata, krb5_data *outbuf)
{
    krb5_error_code 	  retval;
    krb5_safe 		* message;
    krb5_data safe_body;
    krb5_checksum our_cksum, *his_cksum;
    krb5_octet zero_octet = 0;
    krb5_data *scratch;
    krb5_boolean valid;
    struct krb5_safe_with_body swb;

    if (!krb5_is_krb_safe(inbuf))
	return KRB5KRB_AP_ERR_MSG_TYPE;

    if ((retval = decode_krb5_safe_with_body(inbuf, &message, &safe_body)))
	return retval;

    if (!krb5_c_valid_cksumtype(message->checksum->checksum_type)) {
	retval = KRB5_PROG_SUMTYPE_NOSUPP;
	goto cleanup;
    }
    if (!krb5_c_is_coll_proof_cksum(message->checksum->checksum_type) ||
	!krb5_c_is_keyed_cksum(message->checksum->checksum_type)) {
	retval = KRB5KRB_AP_ERR_INAPP_CKSUM;
	goto cleanup;
    }

    if (!krb5_address_compare(context, sender_addr, message->s_address)) {
	retval = KRB5KRB_AP_ERR_BADADDR;
	goto cleanup;
    }

    if (message->r_address) {
	if (recv_addr) {
	    if (!krb5_address_compare(context, recv_addr, message->r_address)) {
		retval = KRB5KRB_AP_ERR_BADADDR;
		goto cleanup;
	    }
	} else {
	    krb5_address **our_addrs;
	
	    if ((retval = krb5_os_localaddr(context, &our_addrs)))
		goto cleanup;
	    
	    if (!krb5_address_search(context, message->r_address, our_addrs)) {
		krb5_free_addresses(context, our_addrs);
		retval = KRB5KRB_AP_ERR_BADADDR;
		goto cleanup;
	    }
	    krb5_free_addresses(context, our_addrs);
	}
    }

    /* verify the checksum */
    /*
     * In order to recreate what was checksummed, we regenerate the message
     * without checksum and then have the cryptographic subsystem verify
     * the checksum for us.  This is because some checksum methods have
     * a confounder encrypted as part of the checksum.
     */
    his_cksum = message->checksum;

    our_cksum.length = 0;
    our_cksum.checksum_type = 0;
    our_cksum.contents = &zero_octet;

    message->checksum = &our_cksum;

    swb.body = &safe_body;
    swb.safe = message;
    retval = encode_krb5_safe_with_body(&swb, &scratch);
    message->checksum = his_cksum;
    if (retval)
	goto cleanup;

    retval = krb5_c_verify_checksum(context, keyblock,
				    KRB5_KEYUSAGE_KRB_SAFE_CKSUM,
				    scratch, his_cksum, &valid);

    (void) memset((char *)scratch->data, 0, scratch->length);
    krb5_free_data(context, scratch);
    
    if (!valid) {
	/*
	 * Checksum over only the KRB-SAFE-BODY, like RFC 1510 says, in
	 * case someone actually implements it correctly.
	 */
	retval = krb5_c_verify_checksum(context, keyblock,
					KRB5_KEYUSAGE_KRB_SAFE_CKSUM,
					&safe_body, his_cksum, &valid);
	if (!valid) {
	    retval = KRB5KRB_AP_ERR_MODIFIED;
	    goto cleanup;
	}
    }

    replaydata->timestamp = message->timestamp;
    replaydata->usec = message->usec;
    replaydata->seq = message->seq_number;

    *outbuf = message->user_data;
    message->user_data.data = NULL;
    retval = 0;
    
cleanup:
    krb5_free_safe(context, message);
    return retval;
}

krb5_error_code KRB5_CALLCONV
krb5_rd_safe(krb5_context context, krb5_auth_context auth_context,
	     const krb5_data *inbuf, krb5_data *outbuf,
	     krb5_replay_data *outdata)
{
    krb5_error_code 	  retval;
    krb5_keyblock	* keyblock;
    krb5_replay_data	  replaydata;

    if (((auth_context->auth_context_flags & KRB5_AUTH_CONTEXT_RET_TIME) ||
      (auth_context->auth_context_flags & KRB5_AUTH_CONTEXT_RET_SEQUENCE)) &&
      (outdata == NULL)) 
	/* Need a better error */
	return KRB5_RC_REQUIRED;

    if ((auth_context->auth_context_flags & KRB5_AUTH_CONTEXT_DO_TIME) &&
      (auth_context->rcache == NULL)) 
	return KRB5_RC_REQUIRED;

    /* Get keyblock */
    if ((keyblock = auth_context->recv_subkey) == NULL)
	keyblock = auth_context->keyblock;

{
    krb5_address * premote_fulladdr = NULL;
    krb5_address * plocal_fulladdr = NULL;
    krb5_address remote_fulladdr;
    krb5_address local_fulladdr;
    CLEANUP_INIT(2);

    if (auth_context->local_addr) {
    	if (auth_context->local_port) {
            if (!(retval = krb5_make_fulladdr(context, auth_context->local_addr,
                                 	      auth_context->local_port, 
					      &local_fulladdr))){
                CLEANUP_PUSH(local_fulladdr.contents, free);
	        plocal_fulladdr = &local_fulladdr;
            } else {
	        return retval;
            }
	} else {
            plocal_fulladdr = auth_context->local_addr;
        }
    }

    if (auth_context->remote_addr) {
    	if (auth_context->remote_port) {
            if (!(retval = krb5_make_fulladdr(context,auth_context->remote_addr,
                                 	      auth_context->remote_port, 
					      &remote_fulladdr))){
                CLEANUP_PUSH(remote_fulladdr.contents, free);
	        premote_fulladdr = &remote_fulladdr;
            } else {
	        return retval;
            }
	} else {
            premote_fulladdr = auth_context->remote_addr;
        }
    }

    memset(&replaydata, 0, sizeof(replaydata));
    if ((retval = krb5_rd_safe_basic(context, inbuf, keyblock,
				     plocal_fulladdr, premote_fulladdr,
				     &replaydata, outbuf))) {
	CLEANUP_DONE();
	return retval;
    }

    CLEANUP_DONE();
}


    if (auth_context->auth_context_flags & KRB5_AUTH_CONTEXT_DO_TIME) {
	krb5_donot_replay replay;

	if ((retval = krb5int_check_clockskew(context, replaydata.timestamp)))
	    goto error;

	if ((retval = krb5_gen_replay_name(context, auth_context->remote_addr, 
					   "_safe", &replay.client)))
	    goto error;

	replay.server = "";		/* XXX */
	replay.cusec = replaydata.usec;
	replay.ctime = replaydata.timestamp;
	if ((retval = krb5_rc_store(context, auth_context->rcache, &replay))) {
	    krb5_xfree(replay.client);
	    goto error;
	}
	krb5_xfree(replay.client);
    }

    if (auth_context->auth_context_flags & KRB5_AUTH_CONTEXT_DO_SEQUENCE) {
	if (!krb5int_auth_con_chkseqnum(context, auth_context,
					replaydata.seq)) {
	    retval =  KRB5KRB_AP_ERR_BADORDER;
	    goto error;
	}
	auth_context->remote_seq_number++;
    }

    if ((auth_context->auth_context_flags & KRB5_AUTH_CONTEXT_RET_TIME) ||
      (auth_context->auth_context_flags & KRB5_AUTH_CONTEXT_RET_SEQUENCE)) {
	outdata->timestamp = replaydata.timestamp;
	outdata->usec = replaydata.usec;
	outdata->seq = replaydata.seq;
    }
	
    /* everything is ok - return data to the user */
    return 0;

error:
    krb5_xfree(outbuf->data);
    return retval;

}