Index: libsrtp/srtp/ekt.c |
=================================================================== |
--- libsrtp/srtp/ekt.c (revision 0) |
+++ libsrtp/srtp/ekt.c (revision 0) |
@@ -0,0 +1,278 @@ |
+/* |
+ * 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 "err.h" |
+#include "srtp_priv.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; |
+} |
+ |
+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); |
+} |
+ |
+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); |
+} |
+ |
+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) { |
+ aes_expanded_key_t expanded_key; |
+ |
+ aes_expand_decryption_key(key, key_len, &expanded_key); |
+ aes_decrypt(ciphertext, &expanded_key); |
+} |
+ |
+/* |
+ * 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; |
+ unsigned master_key_len; |
+ 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; |
+ master_key_len = 16; |
+ |
+ /* 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 */ |
+ |
+} |
+ |
Property changes on: libsrtp/srtp/ekt.c |
___________________________________________________________________ |
Added: svn:eol-style |
+ LF |