Add current version of libSRTP from CVS.

libsrtp/srtp/ekt.c

+/*
+ * 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 */
+  
+}
+