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-rw-r--r--third_party/srtp/srtp/ekt.c279
1 files changed, 279 insertions, 0 deletions
diff --git a/third_party/srtp/srtp/ekt.c b/third_party/srtp/srtp/ekt.c
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+/*
+ * ekt.c
+ *
+ * Encrypted Key Transport for SRTP
+ *
+ * David McGrew
+ * Cisco Systems, Inc.
+ */
+/*
+ *
+ * Copyright (c) 2001-2006 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.
+ *
+ */
+
+
+#include "srtp_priv.h"
+#include "err.h"
+#include "ekt.h"
+
+extern debug_module_t mod_srtp;
+
+/*
+ * The EKT Authentication Tag format.
+ *
+ * 0 1 2 3
+ * 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * : Base Authentication Tag :
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * : Encrypted Master Key :
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * | Rollover Counter |
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * | Initial Sequence Number | Security Parameter Index |
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ *
+ */
+
+#define EKT_OCTETS_AFTER_BASE_TAG 24
+#define EKT_OCTETS_AFTER_EMK 8
+#define EKT_OCTETS_AFTER_ROC 4
+#define EKT_SPI_LEN 2
+
+unsigned
+ekt_octets_after_base_tag(ekt_stream_t ekt) {
+ /*
+ * if the pointer ekt is NULL, then EKT is not in effect, so we
+ * indicate this by returning zero
+ */
+ if (!ekt)
+ return 0;
+
+ switch(ekt->data->ekt_cipher_type) {
+ case EKT_CIPHER_AES_128_ECB:
+ return 16 + EKT_OCTETS_AFTER_EMK;
+ break;
+ default:
+ break;
+ }
+ return 0;
+}
+
+static inline ekt_spi_t
+srtcp_packet_get_ekt_spi(const uint8_t *packet_start, unsigned pkt_octet_len) {
+ const uint8_t *spi_location;
+
+ spi_location = packet_start + (pkt_octet_len - EKT_SPI_LEN);
+
+ return *((const ekt_spi_t *)spi_location);
+}
+
+static inline uint32_t
+srtcp_packet_get_ekt_roc(const uint8_t *packet_start, unsigned pkt_octet_len) {
+ const uint8_t *roc_location;
+
+ roc_location = packet_start + (pkt_octet_len - EKT_OCTETS_AFTER_ROC);
+
+ return *((const uint32_t *)roc_location);
+}
+
+static inline const uint8_t *
+srtcp_packet_get_emk_location(const uint8_t *packet_start,
+ unsigned pkt_octet_len) {
+ const uint8_t *location;
+
+ location = packet_start + (pkt_octet_len - EKT_OCTETS_AFTER_BASE_TAG);
+
+ return location;
+}
+
+
+err_status_t
+ekt_alloc(ekt_stream_t *stream_data, ekt_policy_t policy) {
+
+ /*
+ * if the policy pointer is NULL, then EKT is not in use
+ * so we just set the EKT stream data pointer to NULL
+ */
+ if (!policy) {
+ *stream_data = NULL;
+ return err_status_ok;
+ }
+
+ /* TODO */
+ *stream_data = NULL;
+
+ return err_status_ok;
+}
+
+err_status_t
+ekt_stream_init_from_policy(ekt_stream_t stream_data, ekt_policy_t policy) {
+ if (!stream_data)
+ return err_status_ok;
+
+ return err_status_ok;
+}
+
+
+void
+aes_decrypt_with_raw_key(void *ciphertext, const void *key, int key_len) {
+#ifndef OPENSSL
+//FIXME: need to get this working through the crypto module interface
+ aes_expanded_key_t expanded_key;
+
+ aes_expand_decryption_key(key, key_len, &expanded_key);
+ aes_decrypt(ciphertext, &expanded_key);
+#endif
+}
+
+/*
+ * The function srtp_stream_init_from_ekt() initializes a stream using
+ * the EKT data from an SRTCP trailer.
+ */
+
+err_status_t
+srtp_stream_init_from_ekt(srtp_stream_t stream,
+ const void *srtcp_hdr,
+ unsigned pkt_octet_len) {
+ err_status_t err;
+ const uint8_t *master_key;
+ srtp_policy_t srtp_policy;
+ uint32_t roc;
+
+ /*
+ * NOTE: at present, we only support a single ekt_policy at a time.
+ */
+ if (stream->ekt->data->spi !=
+ srtcp_packet_get_ekt_spi(srtcp_hdr, pkt_octet_len))
+ return err_status_no_ctx;
+
+ if (stream->ekt->data->ekt_cipher_type != EKT_CIPHER_AES_128_ECB)
+ return err_status_bad_param;
+
+ /* decrypt the Encrypted Master Key field */
+ master_key = srtcp_packet_get_emk_location(srtcp_hdr, pkt_octet_len);
+ /* FIX!? This decrypts the master key in-place, and never uses it */
+ /* FIX!? It's also passing to ekt_dec_key (which is an aes_expanded_key_t)
+ * to a function which expects a raw (unexpanded) key */
+ aes_decrypt_with_raw_key((void*)master_key, &stream->ekt->data->ekt_dec_key, 16);
+
+ /* set the SRTP ROC */
+ roc = srtcp_packet_get_ekt_roc(srtcp_hdr, pkt_octet_len);
+ err = rdbx_set_roc(&stream->rtp_rdbx, roc);
+ if (err) return err;
+
+ err = srtp_stream_init(stream, &srtp_policy);
+ if (err) return err;
+
+ return err_status_ok;
+}
+
+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) {
+ uint32_t roc;
+ uint16_t isn;
+ unsigned emk_len;
+ uint8_t *packet;
+
+ /* if the pointer ekt is NULL, then EKT is not in effect */
+ if (!ekt) {
+ debug_print(mod_srtp, "EKT not in use", NULL);
+ return;
+ }
+
+ /* write zeros into the location of the base tag */
+ octet_string_set_to_zero(base_tag, base_tag_len);
+ packet = base_tag + base_tag_len;
+
+ /* copy encrypted master key into packet */
+ emk_len = ekt_octets_after_base_tag(ekt);
+ memcpy(packet, ekt->encrypted_master_key, emk_len);
+ debug_print(mod_srtp, "writing EKT EMK: %s,",
+ octet_string_hex_string(packet, emk_len));
+ packet += emk_len;
+
+ /* copy ROC into packet */
+ roc = (uint32_t)(pkt_index >> 16);
+ *((uint32_t *)packet) = be32_to_cpu(roc);
+ debug_print(mod_srtp, "writing EKT ROC: %s,",
+ octet_string_hex_string(packet, sizeof(roc)));
+ packet += sizeof(roc);
+
+ /* copy ISN into packet */
+ isn = (uint16_t)pkt_index;
+ *((uint16_t *)packet) = htons(isn);
+ debug_print(mod_srtp, "writing EKT ISN: %s,",
+ octet_string_hex_string(packet, sizeof(isn)));
+ packet += sizeof(isn);
+
+ /* copy SPI into packet */
+ *((uint16_t *)packet) = htons(ekt->data->spi);
+ debug_print(mod_srtp, "writing EKT SPI: %s,",
+ octet_string_hex_string(packet, sizeof(ekt->data->spi)));
+
+ /* increase packet length appropriately */
+ *packet_len += EKT_OCTETS_AFTER_EMK + emk_len;
+}
+
+
+/*
+ * The function call srtcp_ekt_trailer(ekt, auth_len, auth_tag )
+ *
+ * If the pointer ekt is NULL, then the other inputs are unaffected.
+ *
+ * auth_tag is a pointer to the pointer to the location of the
+ * authentication tag in the packet. If EKT is in effect, then the
+ * auth_tag pointer is set to the location
+ */
+
+void
+srtcp_ekt_trailer(ekt_stream_t ekt,
+ unsigned *auth_len,
+ void **auth_tag,
+ void *tag_copy) {
+
+ /*
+ * if there is no EKT policy, then the other inputs are unaffected
+ */
+ if (!ekt)
+ return;
+
+ /* copy auth_tag into temporary location */
+
+}
+
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