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/*
* ekt.h
*
* interface to Encrypted Key Transport for SRTP
*
* David McGrew
* Cisco Systems, Inc.
*/
/*
*
* Copyright (c) 2001-2005 Cisco Systems, Inc.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* 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.
*
* Neither the name of the Cisco Systems, Inc. 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 COPYRIGHT HOLDERS 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
* COPYRIGHT HOLDERS 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.
*
*/
/*
* EKT implementation strategy
*
* use stream_template approach
*
* in srtp_unprotect, when a new stream appears, check if template has
* EKT defined, and if it does, then apply EKT processing
*
* question: will we want to allow key-sharing templates in addition
* to EKT templates? could define a new ssrc_type_t that's associated
* with an EKT, e.g. ssrc_any_ekt.
*
*
*/
#ifndef EKT_H
#define EKT_H
#ifdef __cplusplus
extern "C" {
#endif
#include "srtp_priv.h"
#define EKT_CIPHER_DEFAULT 1
#define EKT_CIPHER_AES_128_ECB 1
#define EKT_CIPHER_AES_192_KEY_WRAP 2
#define EKT_CIPHER_AES_256_KEY_WRAP 3
typedef uint16_t ekt_spi_t;
unsigned
ekt_octets_after_base_tag(ekt_stream_t ekt);
/*
* an srtp_policy_t structure can contain a pointer to an
* ekt_policy_t structure
*
* this structure holds all of the high level EKT information, and it
* is passed into libsrtp to indicate what policy should be in effect
*/
typedef struct ekt_policy_ctx_t {
ekt_spi_t spi; /* security parameter index */
uint8_t ekt_cipher_type;
uint8_t *ekt_key;
struct ekt_policy_ctx_t *next_ekt_policy;
} ekt_policy_ctx_t;
/*
* an ekt_data_t structure holds the data corresponding to an ekt key,
* spi, and so on
*/
typedef struct ekt_data_t {
ekt_spi_t spi;
uint8_t ekt_cipher_type;
aes_expanded_key_t ekt_enc_key;
aes_expanded_key_t ekt_dec_key;
struct ekt_data_t *next_ekt_data;
} ekt_data_t;
/*
* an srtp_stream_ctx_t can contain an ekt_stream_ctx_t
*
* an ekt_stream_ctx_t structure holds all of the EKT information for
* a specific SRTP stream
*/
typedef struct ekt_stream_ctx_t {
ekt_data_t *data;
uint16_t isn; /* initial sequence number */
uint8_t encrypted_master_key[SRTP_MAX_KEY_LEN];
} ekt_stream_ctx_t;
err_status_t
ekt_alloc(ekt_stream_t *stream_data, ekt_policy_t policy);
err_status_t
ekt_stream_init(ekt_stream_t e,
ekt_spi_t spi,
void *ekt_key,
unsigned ekt_cipher_type);
err_status_t
ekt_stream_init_from_policy(ekt_stream_t e, ekt_policy_t p);
err_status_t
srtp_stream_init_from_ekt(srtp_stream_t stream,
const void *srtcp_hdr,
unsigned pkt_octet_len);
void
ekt_write_data(ekt_stream_t ekt,
uint8_t *base_tag,
unsigned base_tag_len,
int *packet_len,
xtd_seq_num_t pkt_index);
/*
* We handle EKT by performing some additional steps before
* authentication (copying the auth tag into a temporary location,
* zeroizing the "base tag" field in the packet)
*
* With EKT, the tag_len parameter is actually the base tag
* length
*/
err_status_t
ekt_tag_verification_preproces(uint8_t *pkt_tag,
uint8_t *pkt_tag_copy,
unsigned tag_len);
err_status_t
ekt_tag_verification_postproces(uint8_t *pkt_tag,
uint8_t *pkt_tag_copy,
unsigned tag_len);
/*
* @brief EKT pre-processing for srtcp tag generation
*
* This function does the pre-processing of the SRTCP authentication
* tag format. When EKT is used, it consists of writing the Encrypted
* Master Key, the SRTP ROC, the Initial Sequence Number, and SPI
* fields. The Base Authentication Tag field is set to the all-zero
* value
*
* When EKT is not used, this function is a no-op.
*
*/
err_status_t
srtp_stream_srtcp_auth_tag_generation_preprocess(const srtp_stream_t *s,
uint8_t *pkt_tag,
unsigned pkt_octet_len);
/* it's not clear that a tag_generation_postprocess function is needed */
err_status_t
srtcp_auth_tag_generation_postprocess(void);
#ifdef __cplusplus
}
#endif
#endif /* EKT_H */
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