michael@0: /*
michael@0:  * ekt.h
michael@0:  *
michael@0:  * interface to Encrypted Key Transport for SRTP
michael@0:  *
michael@0:  * David McGrew
michael@0:  * Cisco Systems, Inc.
michael@0:  */
michael@0: /*
michael@0:  *	
michael@0:  * Copyright (c) 2001-2005 Cisco Systems, Inc.
michael@0:  * All rights reserved.
michael@0:  * 
michael@0:  * Redistribution and use in source and binary forms, with or without
michael@0:  * modification, are permitted provided that the following conditions
michael@0:  * are met:
michael@0:  * 
michael@0:  *   Redistributions of source code must retain the above copyright
michael@0:  *   notice, this list of conditions and the following disclaimer.
michael@0:  * 
michael@0:  *   Redistributions in binary form must reproduce the above
michael@0:  *   copyright notice, this list of conditions and the following
michael@0:  *   disclaimer in the documentation and/or other materials provided
michael@0:  *   with the distribution.
michael@0:  * 
michael@0:  *   Neither the name of the Cisco Systems, Inc. nor the names of its
michael@0:  *   contributors may be used to endorse or promote products derived
michael@0:  *   from this software without specific prior written permission.
michael@0:  * 
michael@0:  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
michael@0:  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
michael@0:  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
michael@0:  * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
michael@0:  * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
michael@0:  * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
michael@0:  * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
michael@0:  * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
michael@0:  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
michael@0:  * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
michael@0:  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
michael@0:  * OF THE POSSIBILITY OF SUCH DAMAGE.
michael@0:  *
michael@0:  */
michael@0: 
michael@0: 
michael@0: 
michael@0: /*
michael@0:  * EKT implementation strategy 
michael@0:  * 
michael@0:  * use stream_template approach
michael@0:  *
michael@0:  * in srtp_unprotect, when a new stream appears, check if template has
michael@0:  * EKT defined, and if it does, then apply EKT processing 
michael@0:  *
michael@0:  * question: will we want to allow key-sharing templates in addition
michael@0:  * to EKT templates?  could define a new ssrc_type_t that's associated
michael@0:  * with an EKT, e.g.  ssrc_any_ekt.
michael@0:  *
michael@0:  *
michael@0:  */
michael@0: 
michael@0: #ifndef EKT_H
michael@0: #define EKT_H
michael@0: 
michael@0: #ifdef __cplusplus
michael@0: extern "C" {
michael@0: #endif
michael@0: 
michael@0: #include "srtp_priv.h"
michael@0: 
michael@0: #define EKT_CIPHER_DEFAULT           1
michael@0: #define EKT_CIPHER_AES_128_ECB       1
michael@0: #define EKT_CIPHER_AES_192_KEY_WRAP  2
michael@0: #define EKT_CIPHER_AES_256_KEY_WRAP  3
michael@0: 
michael@0: typedef uint16_t ekt_spi_t;
michael@0: 
michael@0: 
michael@0: unsigned
michael@0: ekt_octets_after_base_tag(ekt_stream_t ekt);
michael@0: 
michael@0: /*
michael@0:  * an srtp_policy_t structure can contain a pointer to an
michael@0:  * ekt_policy_t structure
michael@0:  *
michael@0:  * this structure holds all of the high level EKT information, and it
michael@0:  * is passed into libsrtp to indicate what policy should be in effect
michael@0:  */
michael@0: 
michael@0: typedef struct ekt_policy_ctx_t {
michael@0:   ekt_spi_t  spi;     /* security parameter index */
michael@0:   uint8_t    ekt_cipher_type;
michael@0:   uint8_t   *ekt_key;
michael@0:   struct ekt_policy_ctx_t *next_ekt_policy;
michael@0: } ekt_policy_ctx_t;
michael@0: 
michael@0: 
michael@0: /*
michael@0:  * an ekt_data_t structure holds the data corresponding to an ekt key,
michael@0:  * spi, and so on
michael@0:  */
michael@0: 
michael@0: typedef struct ekt_data_t {
michael@0:   ekt_spi_t spi;
michael@0:   uint8_t ekt_cipher_type;
michael@0:   aes_expanded_key_t ekt_enc_key;
michael@0:   aes_expanded_key_t ekt_dec_key;
michael@0:   struct ekt_data_t *next_ekt_data;
michael@0: } ekt_data_t;
michael@0: 
michael@0: /*
michael@0:  * an srtp_stream_ctx_t can contain an ekt_stream_ctx_t
michael@0:  *
michael@0:  * an ekt_stream_ctx_t structure holds all of the EKT information for
michael@0:  * a specific SRTP stream
michael@0:  */
michael@0: 
michael@0: typedef struct ekt_stream_ctx_t {
michael@0:   ekt_data_t *data;    
michael@0:   uint16_t    isn;     /* initial sequence number  */
michael@0:   uint8_t     encrypted_master_key[SRTP_MAX_KEY_LEN];
michael@0: } ekt_stream_ctx_t;
michael@0: 
michael@0: 
michael@0: 
michael@0: err_status_t 
michael@0: ekt_alloc(ekt_stream_t *stream_data, ekt_policy_t policy);
michael@0: 
michael@0: err_status_t
michael@0: ekt_stream_init(ekt_stream_t e, 
michael@0: 		ekt_spi_t spi,
michael@0: 		void *ekt_key,
michael@0: 		unsigned ekt_cipher_type);
michael@0: 
michael@0: err_status_t
michael@0: ekt_stream_init_from_policy(ekt_stream_t e, ekt_policy_t p);
michael@0:   
michael@0: 
michael@0: 
michael@0: err_status_t
michael@0: srtp_stream_init_from_ekt(srtp_stream_t stream,			  
michael@0: 			  const void *srtcp_hdr,
michael@0: 			  unsigned pkt_octet_len);
michael@0: 		
michael@0: 
michael@0: void
michael@0: ekt_write_data(ekt_stream_t ekt,
michael@0: 	       uint8_t *base_tag, 
michael@0: 	       unsigned base_tag_len, 
michael@0: 	       int *packet_len,
michael@0: 	       xtd_seq_num_t pkt_index);		
michael@0: 
michael@0: /*
michael@0:  * We handle EKT by performing some additional steps before
michael@0:  * authentication (copying the auth tag into a temporary location,
michael@0:  * zeroizing the "base tag" field in the packet)
michael@0:  *
michael@0:  * With EKT, the tag_len parameter is actually the base tag
michael@0:  * length
michael@0:  */
michael@0: 
michael@0: err_status_t
michael@0: ekt_tag_verification_preproces(uint8_t *pkt_tag, 
michael@0: 			       uint8_t *pkt_tag_copy, 
michael@0: 			       unsigned tag_len);
michael@0: 
michael@0: err_status_t
michael@0: ekt_tag_verification_postproces(uint8_t *pkt_tag,
michael@0: 				uint8_t *pkt_tag_copy,
michael@0: 				unsigned tag_len);
michael@0: 
michael@0: 
michael@0: /*
michael@0:  * @brief EKT pre-processing for srtcp tag generation
michael@0:  *
michael@0:  * This function does the pre-processing of the SRTCP authentication
michael@0:  * tag format.  When EKT is used, it consists of writing the Encrypted
michael@0:  * Master Key, the SRTP ROC, the Initial Sequence Number, and SPI
michael@0:  * fields.  The Base Authentication Tag field is set to the all-zero
michael@0:  * value
michael@0:  * 
michael@0:  * When EKT is not used, this function is a no-op.
michael@0:  * 
michael@0:  */
michael@0: 
michael@0: err_status_t
michael@0: srtp_stream_srtcp_auth_tag_generation_preprocess(const srtp_stream_t *s,
michael@0: 						 uint8_t *pkt_tag,
michael@0: 						 unsigned pkt_octet_len);
michael@0: 
michael@0: /* it's not clear that a tag_generation_postprocess function is needed */
michael@0: 
michael@0: err_status_t
michael@0: srtcp_auth_tag_generation_postprocess(void);
michael@0: 
michael@0: 
michael@0: #ifdef __cplusplus
michael@0: }
michael@0: #endif
michael@0: 
michael@0: #endif /* EKT_H */