Make keyed checksums mandatory when generating and verifying checksums, with the following exceptions: * the checksum is being generated or verified as part of encrypting data for a legacy (DES) encryption type * the KRB5_CRYPTO_FLAG_ALLOW_UNKEYED_CHECKSUM flag was set on the crypto context, used to allow unkeyed checksums in krb5 authenticators By making unkeyed checksums opt-in, we eliminate a class of potential vulnerabilities where callers could pass unkeyed checksums. Any code that uses the mandatory checksum type for a given non-legacy encryption type should not be affected by this change. It could potentially break, say, a client trying to do FAST with DES keys but, that should not be supported (because FAST KDCs also support AES). Closes: #835
		
			
				
	
	
		
			152 lines
		
	
	
		
			4.5 KiB
		
	
	
	
		
			C
		
	
	
	
	
	
			
		
		
	
	
			152 lines
		
	
	
		
			4.5 KiB
		
	
	
	
		
			C
		
	
	
	
	
	
/*
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 * Copyright (c) 1997 - 2002 Kungliga Tekniska Högskolan
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 * (Royal Institute of Technology, Stockholm, Sweden).
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 * All rights reserved.
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 *
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 * Redistribution and use in source and binary forms, with or without
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 * modification, are permitted provided that the following conditions
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 * are met:
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 *
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 * 1. Redistributions of source code must retain the above copyright
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 *    notice, this list of conditions and the following disclaimer.
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 *
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 * 2. Redistributions in binary form must reproduce the above copyright
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 *    notice, this list of conditions and the following disclaimer in the
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 *    documentation and/or other materials provided with the distribution.
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 *
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 * 3. Neither the name of the Institute nor the names of its contributors
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 *    may be used to endorse or promote products derived from this software
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 *    without specific prior written permission.
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 *
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 * THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
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 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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 * ARE DISCLAIMED.  IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
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 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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 * SUCH DAMAGE.
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 */
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#include "krb5_locl.h"
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KRB5_LIB_FUNCTION krb5_error_code KRB5_LIB_CALL
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_krb5_mk_req_internal(krb5_context context,
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		      krb5_auth_context *auth_context,
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		      const krb5_flags ap_req_options,
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		      krb5_data *in_data,
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		      krb5_creds *in_creds,
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		      krb5_data *outbuf,
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		      krb5_key_usage checksum_usage,
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		      krb5_key_usage encrypt_usage)
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{
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    krb5_error_code ret;
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    krb5_data authenticator;
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    Checksum c;
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    Checksum *c_opt;
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    krb5_auth_context ac;
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    if(auth_context) {
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	if(*auth_context == NULL)
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	    ret = krb5_auth_con_init(context, auth_context);
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	else
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	    ret = 0;
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	ac = *auth_context;
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    } else
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	ret = krb5_auth_con_init(context, &ac);
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    if(ret)
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	return ret;
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    if(ac->local_subkey == NULL && (ap_req_options & AP_OPTS_USE_SUBKEY)) {
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	ret = krb5_auth_con_generatelocalsubkey(context,
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						ac,
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						&in_creds->session);
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	if(ret)
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	    goto out;
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    }
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    krb5_free_keyblock(context, ac->keyblock);
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    ret = krb5_copy_keyblock(context, &in_creds->session, &ac->keyblock);
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    if (ret)
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	goto out;
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    /*
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     * Use the default checksum type except for some interoperability cases
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     * with older MIT, DCE and Windows KDCs.
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     */
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    if (in_data) {
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	krb5_crypto crypto;
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	krb5_cksumtype checksum_type = CKSUMTYPE_NONE;
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	if (ac->keyblock->keytype == ETYPE_DES_CBC_CRC)
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	    checksum_type = CKSUMTYPE_RSA_MD4;
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	else if (ac->keyblock->keytype == ETYPE_DES_CBC_MD4 ||
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		 ac->keyblock->keytype == ETYPE_DES_CBC_MD5 ||
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		 ac->keyblock->keytype == ETYPE_ARCFOUR_HMAC_MD5 ||
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		 ac->keyblock->keytype == ETYPE_ARCFOUR_HMAC_MD5_56)
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	    checksum_type = CKSUMTYPE_RSA_MD5;
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	else
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	    checksum_type = CKSUMTYPE_NONE;
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	ret = krb5_crypto_init(context, ac->keyblock, 0, &crypto);
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	if (ret)
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	    goto out;
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	_krb5_crypto_set_flags(context, crypto, KRB5_CRYPTO_FLAG_ALLOW_UNKEYED_CHECKSUM);
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	ret = krb5_create_checksum(context,
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				   crypto,
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				   checksum_usage,
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				   checksum_type,
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				   in_data->data,
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				   in_data->length,
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				   &c);
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	krb5_crypto_destroy(context, crypto);
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	c_opt = &c;
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    } else {
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	c_opt = NULL;
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    }
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    if (ret)
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	goto out;
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    ret = _krb5_build_authenticator(context,
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				    ac,
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				    ac->keyblock->keytype,
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				    in_creds,
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				    c_opt,
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				    &authenticator,
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				    encrypt_usage);
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    if (c_opt)
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	free_Checksum (c_opt);
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    if (ret)
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	goto out;
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    ret = krb5_build_ap_req (context, ac->keyblock->keytype,
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			     in_creds, ap_req_options, authenticator, outbuf);
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out:
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    if(auth_context == NULL)
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	krb5_auth_con_free(context, ac);
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    return ret;
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}
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KRB5_LIB_FUNCTION krb5_error_code KRB5_LIB_CALL
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krb5_mk_req_extended(krb5_context context,
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		     krb5_auth_context *auth_context,
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		     const krb5_flags ap_req_options,
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		     krb5_data *in_data,
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		     krb5_creds *in_creds,
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		     krb5_data *outbuf)
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{
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    return _krb5_mk_req_internal (context,
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				 auth_context,
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				 ap_req_options,
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				 in_data,
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				 in_creds,
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				 outbuf,
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				 KRB5_KU_AP_REQ_AUTH_CKSUM,
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				 KRB5_KU_AP_REQ_AUTH);
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}
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